libmicrohttpd2

auth_digest.c (111931B)

---

 /* SPDX-License-Identifier: LGPL-2.1-or-later OR (GPL-2.0-or-later WITH eCos-exception-2.0) */
 /*
   This file is part of GNU libmicrohttpd.
   Copyright (C) 2014-2025 Evgeny Grin (Karlson2k)
   Copyright (C) 2010, 2011, 2012, 2015, 2018 Christian Grothoff
 
   GNU libmicrohttpd is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.
 
   GNU libmicrohttpd is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.
 
   Alternatively, you can redistribute GNU libmicrohttpd and/or
   modify it under the terms of the GNU General Public License as
   published by the Free Software Foundation; either version 2 of
   the License, or (at your option) any later version, together
   with the eCos exception, as follows:
 
     As a special exception, if other files instantiate templates or
     use macros or inline functions from this file, or you compile this
     file and link it with other works to produce a work based on this
     file, this file does not by itself cause the resulting work to be
     covered by the GNU General Public License. However the source code
     for this file must still be made available in accordance with
     section (3) of the GNU General Public License v2.
 
     This exception does not invalidate any other reasons why a work
     based on this file might be covered by the GNU General Public
     License.
 
   You should have received copies of the GNU Lesser General Public
   License and the GNU General Public License along with this library;
   if not, see <https://www.gnu.org/licenses/>.
 */
 
 /**
  * @file src/mhd2/auth_digest.c
  * @brief  The implementation of the Digest Authorization internal functions
  * @author Karlson2k (Evgeny Grin)
  * Based on the MHD v0.xx code by Amr Ali, Matthieu Speder, Christian Grothoff,
  * Dirk Brinkmeier and Evgeny Grin.
  */
 
 #include "mhd_sys_options.h"
 
 #include "mhd_digest_auth_data.h"
 
 #include "mhd_assert.h"
 #include "mhd_unreachable.h"
 #include "mhd_assume.h"
 
 #include <string.h>
 #include "sys_malloc.h"
 
 #include "mhd_str_macros.h"
 #include "mhd_bithelpers.h"
 #include "mhd_arr_num_elems.h"
 #include "mhd_cntnr_ptr.h"
 #include "mhd_limits.h"
 #include "mhd_rng.h"
 
 #include "mhd_str_types.h"
 #include "mhd_buffer.h"
 #include "mhd_daemon.h"
 #include "mhd_request.h"
 #include "mhd_connection.h"
 
 #ifdef MHD_SUPPORT_SHA512_256
 #  include "mhd_sha512_256.h"
 #endif /* MHD_SUPPORT_SHA512_256 */
 #ifdef MHD_SUPPORT_SHA256
 #  include "mhd_sha256.h"
 #endif
 #ifdef MHD_SUPPORT_MD5
 #  include "mhd_md5.h"
 #endif
 
 #include "mhd_str.h"
 #include "mhd_mono_clock.h"
 #include "mhd_atomic_counter.h"
 #include "mhd_locks.h"
 
 #include "request_auth_get.h"
 #include "daemon_funcs.h"
 #include "stream_funcs.h"
 #include "stream_process_request.h"
 
 #include "auth_digest.h"
 
 /*
  * The maximum size of the hash digest, in bytes
  */
 #if defined(MHD_SUPPORT_SHA512_256)
 #  define mhd_MAX_DIGEST mhd_SHA512_256_DIGEST_SIZE
 #elif defined(MHD_SUPPORT_SHA256)
 #  define mhd_MAX_DIGEST mhd_SHA256_DIGEST_SIZE
 #else
 #  define mhd_MAX_DIGEST mhd_MD5_DIGEST_SIZE
 #endif
 
 /**
  * MD5 algorithm identifier for Digest Auth headers
  */
 #define mhd_MD5_TOKEN "MD5"
 
 /**
  * SHA-256 algorithm identifier for Digest Auth headers
  */
 #define mhd_SHA256_TOKEN "SHA-256"
 
 /**
  * SHA-512/256 algorithm for Digest Auth headers.
  */
 #define mhd_SHA512_256_TOKEN "SHA-512-256"
 
 /**
  * The suffix token for "session" algorithms for Digest Auth headers.
  */
 #define mhd_SESS_TOKEN "-sess"
 
 /**
  * The "auth" token for QOP for Digest Auth headers.
  */
 #define mhd_TOKEN_AUTH "auth"
 
 /**
  * The "auth-int" token for QOP for Digest Auth headers.
  */
 #define mhd_TOKEN_AUTH_INT "auth-int"
 
 
 /**
  * The required prefix of parameter with the extended notation
  */
 #define mhd_DAUTH_EXT_PARAM_PREFIX "UTF-8'"
 
 /**
  * The minimal size of the prefix for parameter with the extended notation
  */
 #define mhd_DAUTH_EXT_PARAM_MIN_LEN \
         mhd_SSTR_LEN (mhd_DAUTH_EXT_PARAM_PREFIX "'")
 
 /**
  * The maximum supported size for Digest Auth parameters, like "realm",
  * "username" etc.
  * This limitation is used only for quoted parameters.
  * Parameters without quoted backslash character will be processed as long
  * as they fit connection memory pool (buffer) size.
  */
 #define mhd_AUTH_DIGEST_MAX_PARAM_SIZE (65535)
 
 /**
  * Parameter of request's Digest Authorization header
  */
 struct mhd_RqDAuthParam
 {
   /**
    * The string with length, NOT zero-terminated
    */
   struct MHD_StringNullable value;
   /**
    * True if string must be "unquoted" before processing.
    * This member is false if the string is used in DQUOTE marks, but no
    * backslash-escape is used in the string.
    */
   bool quoted;
 };
 
 /**
  * Client's Digest Authorization header parameters
  */
 struct mhd_AuthDigesReqParams
 {
   struct mhd_RqDAuthParam nonce;
   struct mhd_RqDAuthParam opaque;
   struct mhd_RqDAuthParam response;
   struct mhd_RqDAuthParam username;
   struct mhd_RqDAuthParam username_ext;
   struct mhd_RqDAuthParam realm;
   struct mhd_RqDAuthParam uri;
   /* The raw QOP value, used in the 'response' calculation */
   struct mhd_RqDAuthParam qop_raw;
   struct mhd_RqDAuthParam cnonce;
   struct mhd_RqDAuthParam nc;
 
   /* Decoded values are below */
   bool userhash; /* True if 'userhash' parameter has value 'true'. */
   enum MHD_DigestAuthAlgo algo;
   enum MHD_DigestAuthQOP qop;
 };
 
 /**
  * Digest context data
  */
 union DigestCtx
 {
 #ifdef MHD_SUPPORT_SHA512_256
   struct mhd_Sha512_256Ctx sha512_256_ctx;
 #endif /* MHD_SUPPORT_SHA512_256 */
 #ifdef MHD_SUPPORT_SHA256
   struct mhd_Sha256Ctx sha256_ctx;
 #endif /* MHD_SUPPORT_SHA256 */
 #ifdef MHD_SUPPORT_MD5
   struct mhd_Md5Ctx md5_ctx;
 #endif /* MHD_SUPPORT_MD5 */
 };
 
 mhd_DATA_TRUNCATION_RUNTIME_CHECK_DISABLE
 
 /**
  * Generate simple hash.
  * Very limited avalanche effect. To be used mainly for the table slot choice.
  * @param data_size the size of the data to hash
  * @param data the data to hash
  * @return the hash value
  */
 static MHD_FN_PAR_NONNULL_ALL_
 MHD_FN_PAR_IN_SIZE_ (2, 1) uint_fast64_t
 simple_hash (size_t data_size,
              const uint8_t *restrict data)
 {
   static const uint_fast64_t c[] = { /* Some fractional parts of Euler's number */
     UINT64_C (0xCC64D3484C3475A1),
     UINT64_C (0xCF4DEBCB9ED801F2),
     UINT64_C (0x0C8737A803CF46AD),
     UINT64_C (0x294C9E0E0F9F14AB),
     UINT64_C (0xAD786D855D4EBB1A)
   };
   uint_fast64_t res;
   size_t i;
 
   res = UINT64_C (0x8316A8FE31A2228E); /* Some fractional part of Pi */
   i = 0;
   while (1)
   {
     uint_fast64_t a = 0;
 
     if (8 <= data_size)
       memcpy (&a, data, 8);
     else
       memcpy (&a, data, data_size);
     a ^= c[(i++) % mhd_ARR_NUM_ELEMS (c)];
     a = (uint_fast64_t) mhd_ROTR64 ((uint64_t) a, \
                                     (unsigned int) (res >> 58u));
     res ^= a;
     if (8 >= data_size)
       break;
     data_size -= 8;
     data += 8;
   }
   return res;
 }
 
 
 /**
  * Find index of the provided nonce in the nonces table
  * @param nonce the nonce to use
  * @param arr_size the size of the nonces table
  * @return the index
  */
 static MHD_FN_PAR_NONNULL_ALL_ size_t
 nonce_to_index (const uint8_t nonce[mhd_AUTH_DIGEST_NONCE_BIN_SIZE],
                 size_t arr_size)
 {
   uint_fast64_t hash;
   hash = simple_hash (mhd_AUTH_DIGEST_NONCE_BIN_SIZE,
                       nonce);
   if (arr_size == (arr_size & UINT32_C (0xFFFFFFFF)))
   { /* 'arr_size' <=32-bit */
     hash = (hash ^ (hash >> 32)) & UINT32_C (0xFFFFFFFF); /* Fold hash */
     if (arr_size == (arr_size & UINT16_C (0xFFFF)))
     { /* 'arr_size' <=16-bit */
       hash = (hash ^ (hash >> 16)) & UINT16_C (0xFFFF); /* Fold hash */
       if (arr_size == (arr_size & 0xFFu))
         hash = (hash ^ (hash >> 8)) & 0xFFu; /* 'arr_size' <=8-bit, fold hash */
     }
   }
   return ((size_t) hash) % arr_size;
 }
 
 
 mhd_DATA_TRUNCATION_RUNTIME_CHECK_RESTORE
 
 
 /**
  * Generate a new nonce
  * @param d the daemon to use (must match @a c connection)
  * @param c the connection to generate nonce for
  * @param[out] out_buf the output buffer to pull full nonce, including
  *                     "expiration" tail
  * @param[out] expir the expiration mark, duplicated for convenience
  * @return 'true' if succeed,
  *         'false' if failed
  */
 static MHD_FN_PAR_NONNULL_ALL_
 MHD_FN_PAR_OUT_ (3)
 MHD_FN_PAR_OUT_ (4) bool
 gen_new_nonce (struct MHD_Daemon *restrict d,
                struct MHD_Connection *restrict c,
                uint8_t out_buf[mhd_AUTH_DIGEST_NONCE_BIN_SIZE],
                uint_fast32_t *restrict expir)
 {
   uint_fast64_t expiration;
 
   mhd_assert (! mhd_D_HAS_MASTER (d)); /* only master daemon should be used */
   mhd_assert (d == c->daemon);
   mhd_assert (0 != d->auth_dg.cfg.nonce_tmout);
 
   expiration = mhd_monotonic_msec_counter ()
                + d->auth_dg.cfg.nonce_tmout * (uint_fast64_t) 1000;
 
   if (! mhd_rng (mhd_AUTH_DIGEST_NONCE_BIN_SIZE,
                  out_buf))
   {
     /* Fallback to generating nonce from application-provided
        entropy. Note: this should fail if we do not have
        application-provided entropy. */
     size_t gen_num;
     union DigestCtx d_ctx;
 
     gen_num = mhd_atomic_counter_get_inc_wrap (&(d->auth_dg.num_gen_nonces));
 
 #if defined(MHD_SUPPORT_SHA512_256)
     mhd_SHA512_256_init_one_time (&(d_ctx.sha512_256_ctx));
     mhd_SHA512_256_update (&(d_ctx.sha512_256_ctx),
                            d->auth_dg.entropy.size,
                            (const uint8_t*) d->auth_dg.entropy.data);
     mhd_SHA512_256_update (&(d_ctx.sha512_256_ctx),
                            sizeof(gen_num),
                            (const uint8_t*) &gen_num);
     if (0 != c->sk.addr.size)
       mhd_SHA512_256_update (&(d_ctx.sha512_256_ctx),
                              c->sk.addr.size,
                              (const uint8_t*) c->sk.addr.data);
     mhd_SHA512_256_update (&(d_ctx.sha512_256_ctx),
                            sizeof(expiration),
                            (const uint8_t*) &expiration);
     mhd_SHA512_256_finish_deinit (&(d_ctx.sha512_256_ctx), \
                                   out_buf);
     if (mhd_SHA512_256_has_err (&(d_ctx.sha512_256_ctx)))
       return false;
 #elif defined(MHD_SUPPORT_SHA256)
     mhd_SHA256_init_one_time (&(d_ctx.sha256_ctx));
     mhd_SHA256_update (&(d_ctx.sha256_ctx),
                        d->auth_dg.entropy.size,
                        (const void*) d->auth_dg.entropy.data);
     mhd_SHA256_update (&(d_ctx.sha256_ctx),
                        sizeof(gen_num),
                        (const void*) &gen_num);
     if (0 != c->sk.addr.size)
       mhd_SHA256_update (&(d_ctx.sha256_ctx),
                          c->sk.addr.size,
                          (const void*) c->sk.addr.data);
     mhd_SHA256_update (&(d_ctx.sha256_ctx),
                        sizeof(expiration),
                        (const void*) &expiration);
     mhd_SHA256_finish_deinit (&(d_ctx.sha256_ctx), \
                               out_buf);
     if (mhd_SHA256_has_err (&(d_ctx.sha256_ctx)))
       return false;
 #else  /* MHD_SUPPORT_MD5 */
 #ifndef MHD_SUPPORT_MD5
 #error At least one hashing algorithm must be enabled
 #endif
     mhd_MD5_init_one_time (&(d_ctx.md5_ctx));
     mhd_MD5_update (&(d_ctx.md5_ctx),
                     d->auth_dg.entropy.size,
                     (const void*) d->auth_dg.entropy.data);
     mhd_MD5_update (&(d_ctx.md5_ctx),
                     sizeof(gen_num),
                     (const void*) &gen_num);
     if (0 != c->sk.addr.size)
       mhd_MD5_update (&(d_ctx.md5_ctx),
                       c->sk.addr.size,
                       (const void*) c->sk.addr.data);
     mhd_MD5_update (&(d_ctx.md5_ctx),
                     sizeof(expiration),
                     (const void*) &expiration);
     mhd_MD5_finish_deinit (&(d_ctx.md5_ctx), \
                            out_buf);
     if (mhd_MD5_has_err (&(d_ctx.md5_ctx)))
       return false;
 
     /* One more hash, for the second part */
     gen_num = mhd_atomic_counter_get_inc_wrap (&(d->auth_dg.num_gen_nonces));
 
     mhd_MD5_init_one_time (&(d_ctx.md5_ctx));
     mhd_MD5_update (&(d_ctx.md5_ctx),
                     d->auth_dg.entropy.size,
                     (const void*) d->auth_dg.entropy.data);
     mhd_MD5_update (&(d_ctx.md5_ctx),
                     sizeof(gen_num),
                     (const void*) &gen_num);
     if (0 != c->sk.addr.size)
       mhd_MD5_update (&(d_ctx.md5_ctx),
                       c->sk.addr.size,
                       (const void*) c->sk.addr.data);
     mhd_MD5_update (&(d_ctx.md5_ctx),
                     sizeof(expiration),
                     (const void*) &expiration);
     mhd_MD5_finish_deinit (&(d_ctx.md5_ctx), \
                            out_buf + mhd_MD5_DIGEST_SIZE);
     if (mhd_MD5_has_err (&(d_ctx.md5_ctx)))
       return false;
 #endif /* MHD_SUPPORT_MD5 */
 
   }
 
   *expir = (uint_fast32_t) (expiration / 1000u);
   mhd_PUT_32BIT_LE_UNALIGN (out_buf + mhd_AUTH_DIGEST_NONCE_RAND_BIN_SIZE, \
                             (uint32_t) (*expir & UINT32_C (0xFFFFFFFF)));
 
   return true;
 }
 
 
 MHD_INTERNAL MHD_FN_PAR_NONNULL_ALL_
 MHD_FN_PAR_OUT_ (2) bool
 mhd_auth_digest_get_new_nonce (struct MHD_Connection *restrict c,
                                char out_buf[mhd_AUTH_DIGEST_NONCE_LEN])
 {
   static const int max_retries = 3;
   struct MHD_Daemon *restrict d = mhd_daemon_get_master_daemon (c->daemon);
   uint8_t nonce_bin[mhd_AUTH_DIGEST_NONCE_BIN_SIZE];
   uint_fast32_t expir;
   bool nonce_generated;
   int i;
 
   mhd_assert (0 != d->auth_dg.cfg.nonces_num);
   mhd_assert (NULL != d->auth_dg.nonces);
 
   nonce_generated = false;
   for (i = 0; i < max_retries; ++i)
   {
     bool good_nonce;
     struct mhd_DaemonAuthDigestNonceData *nonce_slot;
     if (! gen_new_nonce (d,
                          c,
                          nonce_bin,
                          &expir))
       continue; /* Failed, re-try */
 
     nonce_generated = true;
     nonce_slot = d->auth_dg.nonces
                  + nonce_to_index (nonce_bin,
                                    d->auth_dg.cfg.nonces_num);
     if (! mhd_mutex_lock (&(d->auth_dg.nonces_lock)))
       return false; /* Failure exit point */
     /* Check whether the same nonce has been used before */
     good_nonce = (0 != memcmp (nonce_slot->nonce,
                                nonce_bin,
                                sizeof(nonce_slot->nonce)));
     if (good_nonce)
     {
       memcpy (nonce_slot->nonce,
               nonce_bin,
               sizeof(nonce_slot->nonce));
       nonce_slot->valid_time = expir;
       nonce_slot->max_recvd_nc = 0;
       nonce_slot->nmask = 0;
     }
     else
     {
       /* Check whether the same nonce has been used with different expiration
          time. */
       nonce_generated = (nonce_slot->valid_time == expir);
     }
     mhd_mutex_unlock_chk (&(d->auth_dg.nonces_lock));
     if (good_nonce)
       break;
   }
   if (! nonce_generated)
     return false; /* Failure exit point */
 
   /* Use the generated nonce even if it is duplicated.
      One of the clients will just get "nonce stale" response with
      the new nonce. */
   (void) mhd_bin_to_hex (nonce_bin,
                          sizeof(nonce_bin),
                          out_buf);
   return true; /* Success exit point */
 }
 
 
 /**
  * Get client's Digest Authorization algorithm type.
  * If no algorithm is specified by client, MD5 is assumed.
  * @param algo_param the Digest Authorization 'algorithm' parameter
  * @return the algorithm type
  */
 static enum MHD_DigestAuthAlgo
 get_rq_dauth_algo (const struct mhd_RqDAuthParam *const algo_param)
 {
   if (NULL == algo_param->value.cstr)
     return MHD_DIGEST_AUTH_ALGO_MD5; /* Assume MD5 by default */
 
   if (algo_param->quoted)
   {
     if (mhd_str_equal_caseless_quoted_s_bin_n (algo_param->value.cstr, \
                                                algo_param->value.len, \
                                                mhd_MD5_TOKEN))
       return MHD_DIGEST_AUTH_ALGO_MD5;
     if (mhd_str_equal_caseless_quoted_s_bin_n (algo_param->value.cstr, \
                                                algo_param->value.len, \
                                                mhd_SHA256_TOKEN))
       return MHD_DIGEST_AUTH_ALGO_SHA256;
     if (mhd_str_equal_caseless_quoted_s_bin_n (algo_param->value.cstr, \
                                                algo_param->value.len, \
                                                mhd_SHA512_256_TOKEN))
       return MHD_DIGEST_AUTH_ALGO_SHA512_256;
 
     /* Algorithms below are not supported by MHD for authentication */
 
     if (mhd_str_equal_caseless_quoted_s_bin_n (algo_param->value.cstr, \
                                                algo_param->value.len, \
                                                mhd_MD5_TOKEN mhd_SESS_TOKEN))
       return MHD_DIGEST_AUTH_ALGO_MD5_SESSION;
     if (mhd_str_equal_caseless_quoted_s_bin_n (algo_param->value.cstr, \
                                                algo_param->value.len, \
                                                mhd_SHA256_TOKEN \
                                                mhd_SESS_TOKEN))
       return MHD_DIGEST_AUTH_ALGO_SHA256_SESSION;
     if (mhd_str_equal_caseless_quoted_s_bin_n (algo_param->value.cstr, \
                                                algo_param->value.len, \
                                                mhd_SHA512_256_TOKEN \
                                                mhd_SESS_TOKEN))
       return MHD_DIGEST_AUTH_ALGO_SHA512_256_SESSION;
 
     /* No known algorithm has been detected */
     return MHD_DIGEST_AUTH_ALGO_INVALID;
   }
   /* The algorithm value is not quoted */
   if (mhd_str_equal_caseless_n_st (mhd_MD5_TOKEN, \
                                    algo_param->value.cstr, \
                                    algo_param->value.len))
     return MHD_DIGEST_AUTH_ALGO_MD5;
   if (mhd_str_equal_caseless_n_st (mhd_SHA256_TOKEN, \
                                    algo_param->value.cstr, \
                                    algo_param->value.len))
     return MHD_DIGEST_AUTH_ALGO_SHA256;
   if (mhd_str_equal_caseless_n_st (mhd_SHA512_256_TOKEN, \
                                    algo_param->value.cstr, \
                                    algo_param->value.len))
     return MHD_DIGEST_AUTH_ALGO_SHA512_256;
 
   /* Algorithms below are not supported by MHD for authentication */
 
   if (mhd_str_equal_caseless_n_st (mhd_MD5_TOKEN mhd_SESS_TOKEN, \
                                    algo_param->value.cstr, \
                                    algo_param->value.len))
     return MHD_DIGEST_AUTH_ALGO_MD5_SESSION;
   if (mhd_str_equal_caseless_n_st (mhd_SHA256_TOKEN mhd_SESS_TOKEN, \
                                    algo_param->value.cstr, \
                                    algo_param->value.len))
     return MHD_DIGEST_AUTH_ALGO_SHA256_SESSION;
   if (mhd_str_equal_caseless_n_st (mhd_SHA512_256_TOKEN mhd_SESS_TOKEN, \
                                    algo_param->value.cstr, \
                                    algo_param->value.len))
     return MHD_DIGEST_AUTH_ALGO_SHA512_256_SESSION;
 
   /* No known algorithm has been detected */
   return MHD_DIGEST_AUTH_ALGO_INVALID;
 }
 
 
 /**
  * Get QOP ('quality of protection') type.
  * @param qop_param the Digest Authorization 'QOP' parameter
  * @return detected QOP ('quality of protection') type.
  */
 static enum MHD_DigestAuthQOP
 get_rq_dauth_qop (const struct mhd_RqDAuthParam *const qop_param)
 {
   if (NULL == qop_param->value.cstr)
     return MHD_DIGEST_AUTH_QOP_NONE;
   if (qop_param->quoted)
   {
     if (mhd_str_equal_caseless_quoted_s_bin_n (qop_param->value.cstr, \
                                                qop_param->value.len, \
                                                mhd_TOKEN_AUTH))
       return MHD_DIGEST_AUTH_QOP_AUTH;
     if (mhd_str_equal_caseless_quoted_s_bin_n (qop_param->value.cstr, \
                                                qop_param->value.len, \
                                                mhd_TOKEN_AUTH_INT))
       return MHD_DIGEST_AUTH_QOP_AUTH_INT;
   }
   else
   {
     if (mhd_str_equal_caseless_n_st (mhd_TOKEN_AUTH, \
                                      qop_param->value.cstr, \
                                      qop_param->value.len))
       return MHD_DIGEST_AUTH_QOP_AUTH;
     if (mhd_str_equal_caseless_n_st (mhd_TOKEN_AUTH_INT, \
                                      qop_param->value.cstr, \
                                      qop_param->value.len))
       return MHD_DIGEST_AUTH_QOP_AUTH_INT;
   }
   /* No know QOP has been detected */
   return MHD_DIGEST_AUTH_QOP_INVALID;
 }
 
 
 /**
  * Parse request Authorization header parameters for Digest Authentication
  * @param val the header string, everything after "Digest " substring
  * @param[out] pdauth the pointer to the structure with Digest Authentication
  *               parameters
  * @return true if parameters has been successfully parsed,
  *         false if format of the @a str is invalid
  */
 static MHD_FN_PAR_NONNULL_ALL_
 MHD_FN_PAR_OUT_ (2) bool
 parse_dauth_params (const struct MHD_String *restrict val,
                     struct mhd_AuthDigesReqParams *restrict pdauth)
 {
   /* The tokens */
   static const struct MHD_String nonce_tk = mhd_MSTR_INIT ("nonce");
   static const struct MHD_String opaque_tk = mhd_MSTR_INIT ("opaque");
   static const struct MHD_String algorithm_tk = mhd_MSTR_INIT ("algorithm");
   static const struct MHD_String response_tk = mhd_MSTR_INIT ("response");
   static const struct MHD_String username_tk = mhd_MSTR_INIT ("username");
   static const struct MHD_String username_ext_tk = mhd_MSTR_INIT ("username*");
   static const struct MHD_String realm_tk = mhd_MSTR_INIT ("realm");
   static const struct MHD_String uri_tk = mhd_MSTR_INIT ("uri");
   static const struct MHD_String qop_tk = mhd_MSTR_INIT ("qop");
   static const struct MHD_String cnonce_tk = mhd_MSTR_INIT ("cnonce");
   static const struct MHD_String nc_tk = mhd_MSTR_INIT ("nc");
   static const struct MHD_String userhash_tk = mhd_MSTR_INIT ("userhash");
   /* The locally processed parameters */
   struct mhd_RqDAuthParam userhash = { {0, NULL}, false};
   struct mhd_RqDAuthParam algorithm = { {0, NULL}, false};
   /* Indexes */
   size_t i;
   size_t p;
   /* The list of the tokens.
      The order of the elements matches the next array. */
   static const struct MHD_String *const tk_names[] = {
     &nonce_tk,          /* 0 */
     &opaque_tk,         /* 1 */
     &algorithm_tk,      /* 2 */
     &response_tk,       /* 3 */
     &username_tk,       /* 4 */
     &username_ext_tk,   /* 5 */
     &realm_tk,          /* 6 */
     &uri_tk,            /* 7 */
     &qop_tk,            /* 8 */
     &cnonce_tk,         /* 9 */
     &nc_tk,             /* 10 */
     &userhash_tk        /* 11 */
   };
   /* The list of the parameters.
      The order of the elements matches the previous array. */
   struct mhd_RqDAuthParam *params[sizeof(tk_names) / sizeof(tk_names[0])];
 
   params[0 ] = &(pdauth->nonce);           /* 0 */
   params[1 ] = &(pdauth->opaque);          /* 1 */
   params[2 ] = &algorithm;                 /* 2 */
   params[3 ] = &(pdauth->response);        /* 3 */
   params[4 ] = &(pdauth->username);        /* 4 */
   params[5 ] = &(pdauth->username_ext);    /* 5 */
   params[6 ] = &(pdauth->realm);           /* 6 */
   params[7 ] = &(pdauth->uri);             /* 7 */
   params[8 ] = &(pdauth->qop_raw);         /* 8 */
   params[9 ] = &(pdauth->cnonce);          /* 9 */
   params[10] = &(pdauth->nc);              /* 10 */
   params[11] = &userhash;                  /* 11 */
 
   mhd_assert (mhd_ARR_NUM_ELEMS (tk_names) == \
               mhd_ARR_NUM_ELEMS (params));
   i = 0;
 
   mhd_assert (' ' != val->cstr[0]);
   mhd_assert ('\t' != val->cstr[0]);
 
   while (val->len > i)
   {
     size_t left;
     mhd_assert (' ' != val->cstr[i]);
     mhd_assert ('\t' != val->cstr[i]);
 
     left = val->len - i;
     if ('=' == val->cstr[i])
       return false; /* The equal sign is not allowed as the first character */
     for (p = 0; p < mhd_ARR_NUM_ELEMS (tk_names); ++p)
     {
       const struct MHD_String *const tk_name = tk_names[p];
       struct mhd_RqDAuthParam *const param = params[p];
       if ( (tk_name->len <= left) &&
            mhd_str_equal_caseless_bin_n (val->cstr + i, tk_name->cstr,
                                          tk_name->len) &&
            ((tk_name->len == left) ||
             ('=' == val->cstr[i + tk_name->len]) ||
             (' ' == val->cstr[i + tk_name->len]) ||
             ('\t' == val->cstr[i + tk_name->len]) ||
             (',' == val->cstr[i + tk_name->len]) ||
             (';' == val->cstr[i + tk_name->len])) )
       {
         size_t value_start;
         size_t value_len;
         bool quoted; /* Only mark as "quoted" if backslash-escape used */
 
         if (tk_name->len == left)
           return false; /* No equal sign after parameter name, broken data */
 
         quoted = false;
         i += tk_name->len;
         /* Skip all whitespaces before '=' */
         while (val->len > i && (' ' == val->cstr[i] || '\t' == val->cstr[i]))
           i++;
         if ((i == val->len) || ('=' != val->cstr[i]))
           return false; /* No equal sign, broken data */
         i++;
         /* Skip all whitespaces after '=' */
         while (val->len > i && (' ' == val->cstr[i] || '\t' == val->cstr[i]))
           i++;
         if ((val->len > i) && ('"' == val->cstr[i]))
         { /* Value is in quotation marks */
           i++; /* Advance after the opening quote */
           value_start = i;
           while (val->len > i && '"' != val->cstr[i])
           {
             if ('\\' == val->cstr[i])
             {
               i++;
               quoted = true; /* Have escaped chars */
             }
             if (0 == val->cstr[i])
               return false; /* Binary zero in parameter value */
             i++;
           }
           if (val->len <= i)
             return false; /* No closing quote */
           mhd_assert ('"' == val->cstr[i]);
           value_len = i - value_start;
           i++; /* Advance after the closing quote */
         }
         else
         {
           value_start = i;
           while ((val->len > i) && (',' != val->cstr[i])
                  && (' ' != val->cstr[i]) && ('\t' != val->cstr[i])
                  && (';' != val->cstr[i]))
           {
             if (0 == val->cstr[i])
               return false;  /* Binary zero in parameter value */
             i++;
           }
           if (';' == val->cstr[i])
             return false;  /* Semicolon in parameter value */
           value_len = i - value_start;
         }
         /* Skip all whitespaces after parameter value */
         while (val->len > i && (' ' == val->cstr[i] || '\t' == val->cstr[i]))
           i++;
         if ((val->len > i) && (',' != val->cstr[i]))
           return false; /* Garbage after parameter value */
 
         /* Have valid parameter name and value */
         mhd_assert (! quoted || 0 != value_len);
         param->value.cstr = val->cstr + value_start;
         param->value.len = value_len;
         param->quoted = quoted;
 
         break; /* Found matching parameter name */
       }
     }
     if (p == mhd_ARR_NUM_ELEMS (tk_names))
     {
       /* No matching parameter name */
       while (val->len > i && ',' != val->cstr[i])
       {
         if ((0 == val->cstr[i]) || (';' == val->cstr[i]))
           return false; /* Not allowed characters */
         if ('"' == val->cstr[i])
         { /* Skip quoted part */
           i++; /* Advance after the opening quote */
           while (val->len > i && '"' != val->cstr[i])
           {
             if (0 == val->cstr[i])
               return false;  /* Binary zero is not allowed */
             if ('\\' == val->cstr[i])
               i++;           /* Skip escaped char */
             i++;
           }
           if (val->len <= i)
             return false; /* No closing quote */
           mhd_assert ('"' == val->cstr[i]);
         }
         i++;
       }
     }
     mhd_assert (val->len == i || ',' == val->cstr[i]);
     if (val->len > i)
       i++; /* Advance after ',' */
     /* Skip all whitespaces before next parameter name */
     while (i < val->len && (' ' == val->cstr[i] || '\t' == val->cstr[i]))
       i++;
   }
 
   /* Postprocess values */
 
   if (NULL != userhash.value.cstr)
   {
     if (userhash.quoted)
       pdauth->userhash =
         mhd_str_equal_caseless_quoted_s_bin_n (userhash.value.cstr, \
                                                userhash.value.len, \
                                                "true");
     else
       pdauth->userhash =
         mhd_str_equal_caseless_n_st ("true", userhash.value.cstr, \
                                      userhash.value.len);
 
   }
   else
     pdauth->userhash = false;
 
   pdauth->algo = get_rq_dauth_algo (&algorithm);
   pdauth->qop = get_rq_dauth_qop (&pdauth->qop_raw);
 
   return true;
 }
 
 
 /**
  * Find and pre-parse request's Digest Authorisation parameters.
  *
  * Function returns result of pre-parsing of the request's "Authorization"
  * header or returns cached result if the header has been already pre-parsed for
  * the current request.
  * @param req the request to process
  * @return #MHD_SC_OK if succeed,
  *         #MHD_SC_AUTH_ABSENT if request has no Digest Authorisation,
  *         #MHD_SC_CONNECTION_POOL_NO_MEM_AUTH_DATA if not enough memory,
  *         #MHD_SC_REQ_AUTH_DATA_BROKEN if the header is broken.
  */
 static MHD_FN_PAR_NONNULL_ALL_ enum MHD_StatusCode
 get_rq_auth_digest_params (struct MHD_Request *restrict req)
 {
   struct MHD_String h_auth_value;
   struct mhd_AuthDigesReqParams *dauth;
 
   mhd_assert (mhd_HTTP_STAGE_HEADERS_PROCESSED <= \
               mhd_CNTNR_CPTR (req, struct MHD_Connection, rq)->stage);
   mhd_assert (mhd_HTTP_STAGE_REQ_RECV_FINISHED >= \
               mhd_CNTNR_CPTR (req, struct MHD_Connection, rq)->stage);
 
   if (NULL != req->auth.digest.rqp)
     return MHD_SC_OK;
 
   if (! mhd_request_get_auth_header_value (req,
                                            mhd_AUTH_HDR_DIGEST,
                                            &h_auth_value))
     return MHD_SC_AUTH_ABSENT;
 
   dauth =
     (struct mhd_AuthDigesReqParams *)
     mhd_stream_alloc_memory (mhd_CNTNR_PTR (req, \
                                             struct MHD_Connection, \
                                             rq),
                              sizeof (struct mhd_AuthDigesReqParams));
 
   if (NULL == dauth)
     return MHD_SC_CONNECTION_POOL_NO_MEM_AUTH_DATA;
 
   memset (dauth, 0, sizeof(struct mhd_AuthDigesReqParams));
   if (! parse_dauth_params (&h_auth_value,
                             dauth))
     return MHD_SC_REQ_AUTH_DATA_BROKEN;
 
   req->auth.digest.rqp = dauth;
 
   return MHD_SC_OK;
 }
 
 
 /**
  * Get username type used by the client.
  * This function does not check whether userhash can be decoded or
  * extended notation (if used) is valid.
  * @param params the Digest Authorization parameters
  * @return the type of username
  */
 mhd_static_inline MHD_FN_PAR_NONNULL_ALL_ enum MHD_DigestAuthUsernameType
 get_rq_uname_type (const struct mhd_AuthDigesReqParams *params)
 {
   if (NULL != params->username.value.cstr)
   {
     if (NULL == params->username_ext.value.cstr)
       return params->userhash ?
              MHD_DIGEST_AUTH_UNAME_TYPE_USERHASH :
              MHD_DIGEST_AUTH_UNAME_TYPE_STANDARD;
     else  /* Both 'username' and 'username*' are used */
       return MHD_DIGEST_AUTH_UNAME_TYPE_INVALID;
   }
   else if (NULL != params->username_ext.value.cstr)
   {
     if (! params->username_ext.quoted && ! params->userhash &&
         (mhd_DAUTH_EXT_PARAM_MIN_LEN <= params->username_ext.value.len) )
       return MHD_DIGEST_AUTH_UNAME_TYPE_EXTENDED;
     else
       return MHD_DIGEST_AUTH_UNAME_TYPE_INVALID;
   }
 
   return MHD_DIGEST_AUTH_UNAME_TYPE_MISSING;
 }
 
 
 /**
  * Get total size required for 'username' and 'userhash_bin'
  * @param params the Digest Authorization parameters
  * @param uname_type the type of username
  * @return the total size required for 'username' and
  *         'userhash_bin' is userhash is used
  */
 mhd_static_inline MHD_FN_PAR_NONNULL_ALL_ size_t
 get_rq_unames_size (const struct mhd_AuthDigesReqParams *params,
                     enum MHD_DigestAuthUsernameType uname_type)
 {
   size_t s;
 
   mhd_assert (get_rq_uname_type (params) == uname_type);
   s = 0;
   if ((MHD_DIGEST_AUTH_UNAME_TYPE_STANDARD == uname_type) ||
       (MHD_DIGEST_AUTH_UNAME_TYPE_USERHASH == uname_type) )
   {
     s += params->username.value.len + 1; /* Add one byte for zero-termination */
     if (MHD_DIGEST_AUTH_UNAME_TYPE_USERHASH == uname_type)
       s += (params->username.value.len + 1) / 2;
   }
   else if (MHD_DIGEST_AUTH_UNAME_TYPE_EXTENDED == uname_type)
     s += params->username_ext.value.len
          - mhd_DAUTH_EXT_PARAM_MIN_LEN + 1; /* Add one byte for zero-termination */
   return s;
 }
 
 
 /**
  * Get unquoted version of Digest Authorization parameter.
  * This function automatically zero-teminate the result.
  * @param param the parameter to extract
  * @param[out] buf the output buffer, must have enough size to hold the result,
  *                 the recommended size is 'param->value.len + 1'
  * @return the size of the result, not including the terminating zero
  */
 static MHD_FN_PAR_NONNULL_ALL_
 MHD_FN_PAR_OUT_ (2) size_t
 get_rq_param_unquoted_copy_z (const struct mhd_RqDAuthParam *restrict param,
                               char *restrict buf)
 {
   size_t len;
   mhd_assert (NULL != param->value.cstr);
   if (! param->quoted)
   {
     memcpy (buf, param->value.cstr, param->value.len);
     buf [param->value.len] = 0;
     return param->value.len;
   }
 
   len = mhd_str_unquote (param->value.cstr, param->value.len, buf);
   mhd_assert (0 != len);
   mhd_assert (len < param->value.len);
   buf[len] = 0;
   return len;
 }
 
 
 /**
  * Get decoded version of username from extended notation.
  * This function automatically zero-teminate the result.
  * @param uname_ext the string of client's 'username*' parameter value
  * @param uname_ext_len the length of @a uname_ext in chars
  * @param[out] buf the output buffer to put decoded username value
  * @param buf_size the size of @a buf
  * @return the number of characters copied to the output buffer or
  *         -1 if wrong extended notation is used.
  */
 static MHD_FN_PAR_NONNULL_ALL_
 MHD_FN_PAR_IN_SIZE_ (1,2)
 MHD_FN_PAR_OUT_SIZE_ (3,4) ssize_t
 get_rq_extended_uname_copy_z (const char *restrict uname_ext,
                               size_t uname_ext_len,
                               char *restrict buf,
                               size_t buf_size)
 {
   size_t r;
   size_t w;
   if ((size_t) SSIZE_MAX < uname_ext_len)
     return -1; /* Too long input string */
 
   if (mhd_DAUTH_EXT_PARAM_MIN_LEN > uname_ext_len)
     return -1; /* Required prefix is missing */
 
   if (! mhd_str_equal_caseless_bin_n (
         uname_ext,
         mhd_DAUTH_EXT_PARAM_PREFIX,
         mhd_SSTR_LEN (mhd_DAUTH_EXT_PARAM_PREFIX)))
     return -1; /* Only UTF-8 is supported, as it is implied by RFC 7616 */
 
   r = mhd_SSTR_LEN (mhd_DAUTH_EXT_PARAM_PREFIX);
   /* Skip language tag */
   while (r < uname_ext_len && '\'' != uname_ext[r])
   {
     const char chr = uname_ext[r];
     if ((' ' == chr) || ('\t' == chr) || ('\"' == chr) || (',' == chr) ||
         (';' == chr) )
       return -1; /* Wrong char in language tag */
     r++;
   }
   if (r >= uname_ext_len)
     return -1; /* The end of the language tag was not found */
   r++; /* Advance to the next char */
 
   w = mhd_str_pct_decode_strict_n (uname_ext + r, uname_ext_len - r,
                                    buf, buf_size);
   if ((0 == w) && (0 != uname_ext_len - r))
     return -1; /* Broken percent encoding */
   buf[w] = 0; /* Zero terminate the result */
   mhd_assert (SSIZE_MAX > w);
   return (ssize_t) w;
 }
 
 
 /**
  * Get copy of username used by the client.
  * @param params the Digest Authorization parameters
  * @param uname_type the type of username
  * @param[out] uname_info the pointer to the structure to be filled
  * @param buf the buffer to be used for usernames
  * @param buf_size the size of the @a buf
  * @return the size of the @a buf used by pointers in @a unames structure
  */
 static size_t
 get_rq_uname (const struct mhd_AuthDigesReqParams *restrict params,
               enum MHD_DigestAuthUsernameType uname_type,
               struct MHD_AuthDigestInfo *restrict uname_info,
               uint8_t *restrict buf,
               size_t buf_size)
 {
   size_t buf_used;
 
   buf_used = 0;
   mhd_assert (get_rq_uname_type (params) == uname_type);
   mhd_assert (MHD_DIGEST_AUTH_UNAME_TYPE_INVALID != uname_type);
   mhd_assert (MHD_DIGEST_AUTH_UNAME_TYPE_MISSING != uname_type);
 
   uname_info->username.cstr = NULL;
   uname_info->username.len = 0;
   uname_info->userhash_hex.cstr = NULL;
   uname_info->userhash_hex.len = 0;
   uname_info->userhash_bin = NULL;
 
   if (MHD_DIGEST_AUTH_UNAME_TYPE_STANDARD == uname_type)
   {
     // TODO: Avoid copying string if not quoted
     uname_info->username.cstr = (char *) (buf + buf_used);
     uname_info->username.len =
       get_rq_param_unquoted_copy_z (&params->username,
                                     (char *) (buf + buf_used));
     buf_used += uname_info->username.len + 1;
     uname_info->uname_type = MHD_DIGEST_AUTH_UNAME_TYPE_STANDARD;
   }
   else if (MHD_DIGEST_AUTH_UNAME_TYPE_USERHASH == uname_type)
   {
     size_t res;
 
     uname_info->userhash_hex.cstr = (char *) (buf + buf_used);
     uname_info->userhash_hex.len =
       get_rq_param_unquoted_copy_z (&params->username,
                                     (char *) (buf + buf_used));
     buf_used += uname_info->userhash_hex.len + 1;
     uname_info->userhash_bin = (uint8_t *) (buf + buf_used);
     res = mhd_hex_to_bin (uname_info->userhash_hex.cstr,
                           uname_info->userhash_hex.len,
                           (uint8_t *) (buf + buf_used));
     if (res != uname_info->userhash_hex.len / 2)
     {
       uname_info->userhash_bin = NULL;
       uname_info->uname_type = MHD_DIGEST_AUTH_UNAME_TYPE_INVALID;
     }
     else
     {
       /* Avoid pointers outside allocated region when the size is zero */
       if (0 == res)
         uname_info->userhash_bin = (const uint8_t *) uname_info->username.cstr;
       uname_info->uname_type = MHD_DIGEST_AUTH_UNAME_TYPE_USERHASH;
       buf_used += res;
     }
   }
   else if (MHD_DIGEST_AUTH_UNAME_TYPE_EXTENDED == uname_type)
   {
     ssize_t res;
     res = get_rq_extended_uname_copy_z (params->username_ext.value.cstr,
                                         params->username_ext.value.len,
                                         (char *) (buf + buf_used),
                                         buf_size - buf_used);
     if (0 > res)
       uname_info->uname_type = MHD_DIGEST_AUTH_UNAME_TYPE_INVALID;
     else
     {
       uname_info->username.cstr = (char *) (buf + buf_used);
       uname_info->username.len = (size_t) res;
       uname_info->uname_type = MHD_DIGEST_AUTH_UNAME_TYPE_EXTENDED;
       buf_used += uname_info->username.len + 1;
     }
   }
   else
   {
     mhd_assert (0);
     uname_info->uname_type = MHD_DIGEST_AUTH_UNAME_TYPE_INVALID;
   }
   mhd_assert (buf_size >= buf_used);
   return buf_used;
 }
 
 
 /**
  * Result of request's Digest Authorization 'nc' value extraction
  */
 enum MHD_FIXED_ENUM_ mhd_GetRqNCResult
 {
   mhd_GET_RQ_NC_NONE = MHD_DIGEST_AUTH_NC_NONE,    /**< No 'nc' value */
   mhd_GET_RQ_NC_VALID = MHD_DIGEST_AUTH_NC_NUMBER, /**< Readable 'nc' value */
   mhd_GET_RQ_NC_TOO_LONG = MHD_DIGEST_AUTH_NC_TOO_LONG, /**< The 'nc' value is too long */
   mhd_GET_RQ_NC_TOO_LARGE = MHD_DIGEST_AUTH_NC_TOO_LARGE, /**< The 'nc' value is too big to fit uint32_t */
   mhd_GET_RQ_NC_BROKEN = 0                         /**< The 'nc' value is not a number */
 };
 
 
 /**
  * Get 'nc' value from request's Authorization header
  * @param params the request digest authentication
  * @param[out] nc the pointer to put nc value to
  * @return enum value indicating the result
  */
 static enum mhd_GetRqNCResult
 get_rq_nc (const struct mhd_AuthDigesReqParams *params,
            uint_fast32_t *nc)
 {
   const struct mhd_RqDAuthParam *const nc_param =
     &params->nc;
   char unq[16];
   const char *val;
   size_t val_len;
   size_t res;
   uint64_t nc_val;
 
   if (NULL == nc_param->value.cstr)
     return mhd_GET_RQ_NC_NONE;
 
   if (0 == nc_param->value.len)
     return mhd_GET_RQ_NC_BROKEN;
 
   if (! nc_param->quoted)
   {
     val = nc_param->value.cstr;
     val_len = nc_param->value.len;
   }
   else
   {
     /* Actually no backslashes must be used in 'nc' */
     if (sizeof(unq) < params->nc.value.len)
       return mhd_GET_RQ_NC_TOO_LONG;
     val_len = mhd_str_unquote (nc_param->value.cstr, nc_param->value.len, unq);
     if (0 == val_len)
       return mhd_GET_RQ_NC_BROKEN;
     val = unq;
   }
 
   res = mhd_strx_to_uint64_n (val,
                               val_len,
                               &nc_val);
   if (0 == res)
   {
     const char f = val[0];
     if ( (('9' >= f) && ('0' <= f)) ||
          (('F' >= f) && ('A' <= f)) ||
          (('a' <= f) && ('f' >= f)) )
       return mhd_GET_RQ_NC_TOO_LARGE;
     else
       return mhd_GET_RQ_NC_BROKEN;
   }
   if (val_len != res)
     return mhd_GET_RQ_NC_BROKEN;
   if (nc_val != (nc_val & UINT64_C (0xFFFFFFFF)))
     return mhd_GET_RQ_NC_TOO_LARGE;
   *nc = (uint_fast32_t) nc_val;
   return mhd_GET_RQ_NC_VALID;
 }
 
 
 static MHD_FN_MUST_CHECK_RESULT_ MHD_FN_PAR_NONNULL_ALL_
 enum MHD_StatusCode
 find_and_parse_auth_digest_info (struct MHD_Request *restrict req)
 {
   enum MHD_StatusCode res;
   struct MHD_AuthDigestInfo *info;
   enum MHD_DigestAuthUsernameType uname_type;
   size_t unif_buf_size;
   uint8_t *unif_buf_ptr;
   size_t unif_buf_used;
   enum mhd_GetRqNCResult nc_res;
 
   mhd_assert (NULL == req->auth.digest.info);
 
   res = get_rq_auth_digest_params (req);
   if (MHD_SC_OK != res)
     return res;
 
   unif_buf_size = 0;
 
   uname_type = get_rq_uname_type (req->auth.digest.rqp);
 
   unif_buf_size += get_rq_unames_size (req->auth.digest.rqp,
                                        uname_type);
 
   if (NULL != req->auth.digest.rqp->opaque.value.cstr)
     unif_buf_size += req->auth.digest.rqp->opaque.value.len + 1;  /* Add one for zero-termination */
   if (NULL != req->auth.digest.rqp->realm.value.cstr)
     unif_buf_size += req->auth.digest.rqp->realm.value.len + 1;   /* Add one for zero-termination */
   info =
     (struct MHD_AuthDigestInfo *)
     mhd_stream_alloc_memory (mhd_CNTNR_PTR (req, struct MHD_Connection, rq),
                              (sizeof(struct MHD_AuthDigestInfo))
                              + unif_buf_size);
   if (NULL == info)
     return MHD_SC_CONNECTION_POOL_NO_MEM_AUTH_DATA;
 
   memset (info,
           0,
           (sizeof(struct MHD_AuthDigestInfo)) + unif_buf_size);
 #ifndef HAVE_NULL_PTR_ALL_ZEROS
   info->username.cstr = NULL;
   info->userhash_hex.cstr = NULL;
   info->userhash_bin = NULL;
   info->opaque.cstr = NULL;
   info->realm.cstr = NULL;
 #endif
 
   unif_buf_ptr = (uint8_t *) (info + 1);
   unif_buf_used = 0;
 
   info->algo = req->auth.digest.rqp->algo;
 
   if ( (MHD_DIGEST_AUTH_UNAME_TYPE_MISSING != uname_type) &&
        (MHD_DIGEST_AUTH_UNAME_TYPE_INVALID != uname_type) )
     unif_buf_used +=
       get_rq_uname (req->auth.digest.rqp, uname_type, info,
                     unif_buf_ptr + unif_buf_used,
                     unif_buf_size - unif_buf_used);
   else
     info->uname_type = uname_type;
 
   if (NULL != req->auth.digest.rqp->opaque.value.cstr)
   {
     info->opaque.cstr = (char *) (unif_buf_ptr + unif_buf_used);
     info->opaque.len =
       get_rq_param_unquoted_copy_z (&(req->auth.digest.rqp->opaque),
                                     (char *) (unif_buf_ptr + unif_buf_used));
     unif_buf_used += info->opaque.len + 1;
   }
   if (NULL != req->auth.digest.rqp->realm.value.cstr)
   {
     info->realm.cstr = (char *) (unif_buf_ptr + unif_buf_used);
     info->realm.len =
       get_rq_param_unquoted_copy_z (&(req->auth.digest.rqp->realm),
                                     (char *) (unif_buf_ptr + unif_buf_used));
     unif_buf_used += info->realm.len + 1;
   }
 
   mhd_assert (unif_buf_size >= unif_buf_used);
 
   info->qop = req->auth.digest.rqp->qop;
 
   if (NULL != req->auth.digest.rqp->cnonce.value.cstr)
     info->cnonce_len = req->auth.digest.rqp->cnonce.value.len;
   else
     info->cnonce_len = 0;
 
   nc_res = get_rq_nc (req->auth.digest.rqp, &info->nc);
   if (mhd_GET_RQ_NC_VALID == nc_res)
   {
     if (0 == info->nc)
       info->nc_type = MHD_DIGEST_AUTH_NC_ZERO;
     else
       info->nc_type = MHD_DIGEST_AUTH_NC_NUMBER;
   }
   else
   {
     info->nc = 0;
     if (mhd_GET_RQ_NC_BROKEN == nc_res)
       info->nc_type = MHD_DIGEST_AUTH_NC_NONE;
     else
       info->nc_type = (enum MHD_DigestAuthNC) nc_res;
   }
 
   req->auth.digest.info = info;
 
   mhd_assert (uname_type == info->uname_type);
 
   if ((MHD_DIGEST_AUTH_UNAME_TYPE_MISSING == uname_type) ||
       (MHD_DIGEST_AUTH_UNAME_TYPE_INVALID == uname_type) ||
       ((mhd_GET_RQ_NC_BROKEN == nc_res)))
     return MHD_SC_REQ_AUTH_DATA_BROKEN;
 
   return MHD_SC_OK;
 }
 
 
 MHD_INTERNAL MHD_FN_MUST_CHECK_RESULT_ MHD_FN_PAR_NONNULL_ALL_
 MHD_FN_PAR_OUT_ (2) enum MHD_StatusCode
 mhd_request_get_auth_digest_info (
   struct MHD_Request *restrict req,
   const struct MHD_AuthDigestInfo **restrict v_auth_digest_info)
 {
   mhd_assert (mhd_HTTP_STAGE_HEADERS_PROCESSED <= \
               mhd_CNTNR_CPTR (req, struct MHD_Connection, rq)->stage);
   mhd_assert (mhd_HTTP_STAGE_REQ_RECV_FINISHED >= \
               mhd_CNTNR_CPTR (req, struct MHD_Connection, rq)->stage);
 
   if (MHD_SC_OK != req->auth.digest.parse_result)
     return req->auth.digest.parse_result;
 
   if (NULL == req->auth.digest.info)
     req->auth.digest.parse_result = find_and_parse_auth_digest_info (req);
 
   if (MHD_SC_OK != req->auth.digest.parse_result)
     return req->auth.digest.parse_result; /* Failure exit point */
 
   mhd_assert (NULL != req->auth.digest.info);
   *v_auth_digest_info = req->auth.digest.info;
 
   return MHD_SC_OK; /* Success exit point */
 }
 
 
 /**
  * Get base hash calculation algorithm from #MHD_DigestAuthAlgo value.
  * @param algo the MHD_DigestAuthAlgo value
  * @return the base hash calculation algorithm
  */
 mhd_static_inline enum MHD_DigestBaseAlgo
 get_base_digest_algo (enum MHD_DigestAuthAlgo algo)
 {
   unsigned int base_algo;
 
   base_algo =
     ((unsigned int) algo)
     & ~((unsigned int)
         (MHD_DIGEST_AUTH_ALGO_NON_SESSION
          | MHD_DIGEST_AUTH_ALGO_SESSION));
   return (enum MHD_DigestBaseAlgo) base_algo;
 }
 
 
 /**
  * Get digest size in bytes for specified algorithm.
  *
  * Internal inline version.
  * @param algo the algorithm to check
  * @return the size of the digest (in bytes) or zero if the input value is not
  *         supported/valid
  */
 mhd_static_inline size_t
 digest_get_hash_size (enum MHD_DigestAuthAlgo algo)
 {
 #ifdef MHD_SUPPORT_MD5
   mhd_assert (MHD_MD5_DIGEST_SIZE == mhd_MD5_DIGEST_SIZE);
 #endif /* MHD_SUPPORT_MD5 */
 #ifdef MHD_SUPPORT_SHA256
   mhd_assert (MHD_SHA256_DIGEST_SIZE == mhd_SHA256_DIGEST_SIZE);
 #endif /* MHD_SUPPORT_SHA256 */
 #ifdef MHD_SUPPORT_SHA512_256
   mhd_assert (MHD_SHA512_256_DIGEST_SIZE == mhd_SHA512_256_DIGEST_SIZE);
 #ifdef MHD_SUPPORT_SHA256
   mhd_assert (mhd_SHA256_DIGEST_SIZE == mhd_SHA512_256_DIGEST_SIZE);
 #endif /* MHD_SUPPORT_SHA256 */
 #endif /* MHD_SUPPORT_SHA512_256 */
   /* Only one algorithm must be specified */
   mhd_assert (1 == \
               (((0 != (((unsigned int) algo) \
                        & MHD_DIGEST_BASE_ALGO_MD5)) ? 1 : 0)   \
                + ((0 != (((unsigned int) algo) \
                          & MHD_DIGEST_BASE_ALGO_SHA256)) ? 1 : 0)   \
                + ((0 != (((unsigned int) algo) \
                          & MHD_DIGEST_BASE_ALGO_SHA512_256)) ? 1 : 0)));
 #ifdef MHD_SUPPORT_MD5
   if (0 != (((unsigned int) algo)
             & ((unsigned int) MHD_DIGEST_BASE_ALGO_MD5)))
     return MHD_MD5_DIGEST_SIZE;
   else
 #endif /* MHD_SUPPORT_MD5 */
 #if defined(MHD_SUPPORT_SHA256) && defined(MHD_SUPPORT_SHA512_256)
   if (0 != (((unsigned int) algo)
             & ( ((unsigned int) MHD_DIGEST_BASE_ALGO_SHA256)
                 | ((unsigned int) MHD_DIGEST_BASE_ALGO_SHA512_256))))
     return MHD_SHA256_DIGEST_SIZE; /* The same as mhd_SHA512_256_DIGEST_SIZE */
   else
 #elif defined(MHD_SUPPORT_SHA256)
   if (0 != (((unsigned int) algo)
             & ((unsigned int) MHD_DIGEST_BASE_ALGO_SHA256)))
     return MHD_SHA256_DIGEST_SIZE;
   else
 #elif defined(MHD_SUPPORT_SHA512_256)
   if (0 != (((unsigned int) algo)
             & ((unsigned int) MHD_DIGEST_BASE_ALGO_SHA512_256)))
     return MHD_SHA512_256_DIGEST_SIZE;
   else
 #endif /* MHD_SUPPORT_SHA512_256 */
     (void) 0; /* Unsupported algorithm */
 
   return 0; /* Wrong input or unsupported algorithm */
 }
 
 
 /**
  * Get digest size for specified algorithm.
  *
  * The size of the digest specifies the size of the userhash, userdigest
  * and other parameters which size depends on used hash algorithm.
  * @param algo the algorithm to check
  * @return the size of the digest (either #MHD_MD5_DIGEST_SIZE or
  *         #MHD_SHA256_DIGEST_SIZE/MHD_SHA512_256_DIGEST_SIZE)
  *         or zero if the input value is not supported or not valid
  * @sa #MHD_digest_auth_calc_userdigest()
  * @sa #MHD_digest_auth_calc_userhash(), #MHD_digest_auth_calc_userhash_hex()
  * @note Available since #MHD_VERSION 0x00097701
  * @ingroup authentication
  */
 MHD_EXTERN_ MHD_FN_CONST_ size_t
 MHD_digest_get_hash_size (enum MHD_DigestAuthAlgo algo)
 {
   return digest_get_hash_size (algo);
 }
 
 
 /**
  * The digest calculation structure.
  */
 struct DigestAlgorithm
 {
   /**
    * A context for the digest algorithm, already initialized to be
    * useful for @e init, @e update and @e digest.
    */
   union DigestCtx ctx;
 
   /**
    * The hash calculation algorithm.
    */
   enum MHD_DigestBaseAlgo algo;
 
   /**
    * Buffer for hex-print of the final digest.
    */
 #ifndef NDEBUG
   bool uninitialised; /**< The structure has been not set-up */
   bool algo_selected; /**< The algorithm has been selected */
   bool ready_for_hashing; /**< The structure is ready to hash data */
   bool hashing; /**< Some data has been hashed, but the digest has not finalised yet */
 #endif /* NDEBUG */
 };
 
 
 /**
  * Return the size of the digest.
  * @param da the digest calculation structure to identify
  * @return the size of the digest.
  */
 mhd_static_inline MHD_FN_PAR_NONNULL_ALL_ unsigned int
 digest_get_size (struct DigestAlgorithm *da)
 {
   mhd_assert (! da->uninitialised);
   mhd_assert (da->algo_selected);
 #ifdef MHD_SUPPORT_MD5
   if (MHD_DIGEST_BASE_ALGO_MD5 == da->algo)
     return mhd_MD5_DIGEST_SIZE;
 #endif /* MHD_SUPPORT_MD5 */
 #ifdef MHD_SUPPORT_SHA256
   if (MHD_DIGEST_BASE_ALGO_SHA256 == da->algo)
     return mhd_SHA256_DIGEST_SIZE;
 #endif /* MHD_SUPPORT_SHA256 */
 #ifdef MHD_SUPPORT_SHA512_256
   if (MHD_DIGEST_BASE_ALGO_SHA512_256 == da->algo)
     return mhd_SHA512_256_DIGEST_SIZE;
 #endif /* MHD_SUPPORT_SHA512_256 */
   mhd_UNREACHABLE ();
   return 0;
 }
 
 
 #if defined(mhd_MD5_HAS_DEINIT) \
   || defined(mhd_SHA256_HAS_DEINIT) \
   || defined(mhd_SHA512_256_HAS_DEINIT)
 /**
  * Indicates presence of digest_deinit() function
  */
 #define mhd_DIGEST_HAS_DEINIT 1
 #endif /* mhd_MD5_HAS_DEINIT || mhd_SHA256_HAS_DEINIT */
 
 #ifdef mhd_DIGEST_HAS_DEINIT
 /**
  * Zero-initialise digest calculation structure.
  *
  * This initialisation is enough to safely call #digest_deinit() only.
  * To make any real digest calculation, #digest_setup_and_init() must be called.
  * @param da the digest calculation
  */
 mhd_static_inline void
 digest_setup_zero (struct DigestAlgorithm *da)
 {
 #ifndef NDEBUG
   da->uninitialised = false;
   da->algo_selected = false;
   da->ready_for_hashing = false;
   da->hashing = false;
 #endif /* _DEBUG */
   da->algo = MHD_DIGEST_BASE_ALGO_INVALID;
 }
 
 
 /**
  * De-initialise digest calculation structure.
  *
  * This function must be called if #digest_setup_and_init() was called for
  * @a da.
  * This function must not be called if @a da was not initialised by
  * #digest_setup_and_init() or by #digest_setup_zero().
  * @param da the digest calculation
  */
 mhd_static_inline void
 digest_deinit (struct DigestAlgorithm *da)
 {
   mhd_assert (! da->uninitialised);
 #ifdef mhd_MD5_HAS_DEINIT
   if (MHD_DIGEST_BASE_ALGO_MD5 == da->algo)
     mhd_MD5_deinit (&(da->ctx.md5_ctx));
   else
 #endif /* mhd_MD5_HAS_DEINIT */
 #ifdef mhd_SHA256_HAS_DEINIT
   if (MHD_DIGEST_BASE_ALGO_SHA256 == da->algo)
     mhd_SHA256_deinit (&(da->ctx.sha256_ctx));
   else
 #endif /* mhd_SHA256_HAS_DEINIT */
 #ifdef mhd_SHA512_256_HAS_DEINIT
   if (MHD_DIGEST_BASE_ALGO_SHA512_256 == da->algo)
     mhd_SHA512_256_deinit (&(da->ctx.sha512_256_ctx));
   else
 #endif /* mhd_SHA512_256_HAS_DEINIT */
   (void) 0;
   digest_setup_zero (da);
 }
 
 
 #else  /* ! mhd_DIGEST_HAS_DEINIT */
 #define digest_setup_zero(da) ((void) 0)
 #define digest_deinit(da) ((void) 0)
 #endif /* ! mhd_DIGEST_HAS_DEINIT */
 
 
 /**
  * Set-up the digest calculation structure and initialise with initial values.
  *
  * If @a da was successfully initialised, #digest_deinit() must be called
  * after finishing using of the @a da.
  *
  * This function must not be called more than once for any @a da.
  *
  * @param da the structure to set-up
  * @param algo the algorithm to use for digest calculation
  * @return boolean 'true' if successfully set-up,
  *         false otherwise.
  */
 mhd_static_inline MHD_FN_MUST_CHECK_RESULT_ MHD_FN_PAR_NONNULL_ALL_ bool
 digest_init_one_time (struct DigestAlgorithm *da,
                       enum MHD_DigestBaseAlgo algo)
 {
 #ifndef NDEBUG
   da->uninitialised = false;
   da->algo_selected = false;
   da->ready_for_hashing = false;
   da->hashing = false;
 #endif /* _DEBUG */
   switch (algo)
   {
   case MHD_DIGEST_BASE_ALGO_MD5:
 #ifdef MHD_SUPPORT_MD5
     da->algo = MHD_DIGEST_BASE_ALGO_MD5;
 #  ifndef NDEBUG
     da->algo_selected = true;
 #  endif
     mhd_MD5_init_one_time (&(da->ctx.md5_ctx));
 #  ifndef NDEBUG
     da->ready_for_hashing = true;
 #  endif
     return true;
 #endif /* MHD_SUPPORT_MD5 */
     break;
 
   case MHD_DIGEST_BASE_ALGO_SHA256:
 #ifdef MHD_SUPPORT_SHA256
     da->algo = MHD_DIGEST_BASE_ALGO_SHA256;
 #  ifndef NDEBUG
     da->algo_selected = true;
 #  endif
     mhd_SHA256_init_one_time (&(da->ctx.sha256_ctx));
 #  ifndef NDEBUG
     da->ready_for_hashing = true;
 #  endif
     return true;
 #endif /* MHD_SUPPORT_SHA256 */
     break;
 
   case MHD_DIGEST_BASE_ALGO_SHA512_256:
 #ifdef MHD_SUPPORT_SHA512_256
     da->algo = MHD_DIGEST_BASE_ALGO_SHA512_256;
 #  ifndef NDEBUG
     da->algo_selected = true;
 #  endif
     mhd_SHA512_256_init_one_time (&(da->ctx.sha512_256_ctx));
 #  ifndef NDEBUG
     da->ready_for_hashing = true;
 #  endif
     return true;
 #endif /* MHD_SUPPORT_SHA512_256 */
     break;
 
   case MHD_DIGEST_BASE_ALGO_INVALID:
   default:
     mhd_UNREACHABLE ();
     break;
   }
   da->algo = MHD_DIGEST_BASE_ALGO_INVALID;
   return false; /* Unsupported or bad algorithm */
 }
 
 
 /**
  * Hash more data for digest calculation.
  * @param da the digest calculation
  * @param size the size of the @a data in bytes
  * @param data the data to process
  */
 mhd_static_inline MHD_FN_PAR_NONNULL_ALL_
 MHD_FN_PAR_IN_SIZE_ (3, 2) void
 digest_update (struct DigestAlgorithm *restrict da,
                size_t size,
                const void *restrict data)
 {
   mhd_assert (! da->uninitialised);
   mhd_assert (da->algo_selected);
   mhd_assert (da->ready_for_hashing);
   switch (da->algo)
   {
   case MHD_DIGEST_BASE_ALGO_MD5:
 #ifdef MHD_SUPPORT_MD5
     mhd_MD5_update (&da->ctx.md5_ctx,
                     size,
                     (const uint8_t *) data);
 #else
     mhd_UNREACHABLE ();
 #endif
     break;
   case MHD_DIGEST_BASE_ALGO_SHA256:
 #ifdef MHD_SUPPORT_SHA256
     mhd_SHA256_update (&da->ctx.sha256_ctx,
                        size,
                        (const uint8_t *) data);
 #else
     mhd_UNREACHABLE ();
 #endif
     break;
   case MHD_DIGEST_BASE_ALGO_SHA512_256:
 #ifdef MHD_SUPPORT_SHA512_256
     mhd_SHA512_256_update (&da->ctx.sha512_256_ctx,
                            size,
                            (const uint8_t *) data);
 #else
     mhd_UNREACHABLE ();
 #endif
     break;
   case MHD_DIGEST_BASE_ALGO_INVALID:
   default:
     mhd_UNREACHABLE ();
     break;
   }
 #ifndef NDEBUG
   da->hashing = true;
 #endif
 }
 
 
 /**
  * Feed digest calculation with more data from string.
  * @param da the digest calculation
  * @param str the zero-terminated string to process
  */
 mhd_static_inline MHD_FN_PAR_NONNULL_ALL_
 MHD_FN_PAR_CSTR_ (2) void
 digest_update_str (struct DigestAlgorithm *restrict da,
                    const char *restrict str)
 {
   digest_update (da,
                  strlen (str),
                  (const uint8_t *) str);
 }
 
 
 /**
  * Feed digest calculation with more data from string.
  * @param da the digest calculation
  * @param buf the sized buffer with the data
  */
 mhd_static_inline MHD_FN_PAR_NONNULL_ALL_
 MHD_FN_PAR_CSTR_ (2) void
 digest_update_cbuf (struct DigestAlgorithm *restrict da,
                     const struct mhd_BufferConst *restrict buf)
 {
   digest_update (da,
                  buf->size,
                  (const uint8_t *) buf->data);
 }
 
 
 /**
  * Feed digest calculation with more data from string.
  * @param da the digest calculation
  * @param buf the sized buffer with the data
  */
 mhd_static_inline MHD_FN_PAR_NONNULL_ALL_
 MHD_FN_PAR_CSTR_ (2) void
 digest_update_buf (struct DigestAlgorithm *restrict da,
                    const struct mhd_Buffer *restrict buf)
 {
   digest_update (da,
                  buf->size,
                  (const uint8_t *) buf->data);
 }
 
 
 /**
  * Feed digest calculation with single colon ':' character.
  * @param da the digest calculation
  */
 mhd_static_inline MHD_FN_PAR_NONNULL_ALL_ void
 digest_update_with_colon (struct DigestAlgorithm *da)
 {
   static const uint8_t colon = (uint8_t) ':';
   digest_update (da,
                  1,
                  &colon);
 }
 
 
 /**
  * Finally calculate hash (the digest).
  * @param da the digest calculation
  * @param[out] digest the pointer to the buffer to put calculated digest,
  *                    must be at least digest_get_size(da) bytes large
  */
 mhd_static_inline MHD_FN_PAR_NONNULL_ALL_
 MHD_FN_PAR_OUT_ (2) void
 digest_calc_hash (struct DigestAlgorithm *da,
                   uint8_t *digest)
 {
   mhd_assert (! da->uninitialised);
   mhd_assert (da->algo_selected);
   mhd_assert (da->ready_for_hashing);
   switch (da->algo)
   {
   case MHD_DIGEST_BASE_ALGO_MD5:
 #ifdef MHD_SUPPORT_MD5
 #  ifdef mhd_MD5_HAS_FINISH
     mhd_MD5_finish (&da->ctx.md5_ctx, digest);
 #    ifndef NDEBUG
     da->ready_for_hashing = false;
 #    endif /* _DEBUG */
 #  else  /* ! mhd_MD5_HAS_FINISH */
     mhd_MD5_finish_reset (&da->ctx.md5_ctx, digest);
 #    ifndef NDEBUG
     da->ready_for_hashing = true;
 #    endif /* _DEBUG */
 #  endif /* ! mhd_MD5_HAS_FINISH */
 #else  /* ! MHD_SUPPORT_MD5 */
     mhd_UNREACHABLE ();
 #endif /* ! MHD_SUPPORT_MD5 */
     break;
 
   case MHD_DIGEST_BASE_ALGO_SHA256:
 #ifdef MHD_SUPPORT_SHA256
 #  ifdef mhd_SHA256_HAS_FINISH
     mhd_SHA256_finish (&da->ctx.sha256_ctx, digest);
 #    ifndef NDEBUG
     da->ready_for_hashing = false;
 #    endif /* _DEBUG */
 #  else  /* ! mhd_SHA256_HAS_FINISH */
     mhd_SHA256_finish_reset (&da->ctx.sha256_ctx, digest);
 #    ifndef NDEBUG
     da->ready_for_hashing = true;
 #    endif /* _DEBUG */
 #  endif /* ! mhd_SHA256_HAS_FINISH */
 #else  /* ! MHD_SUPPORT_SHA256 */
     mhd_UNREACHABLE ();
 #endif /* ! MHD_SUPPORT_SHA256 */
     break;
 
   case MHD_DIGEST_BASE_ALGO_SHA512_256:
 #ifdef MHD_SUPPORT_SHA512_256
 #ifdef mhd_SHA512_256_HAS_FINISH
     mhd_SHA512_256_finish (&da->ctx.sha512_256_ctx, digest);
 #ifndef NDEBUG
     da->ready_for_hashing = false;
 #endif /* _DEBUG */
 #else  /* ! mhd_SHA512_256_HAS_FINISH */
     mhd_SHA512_256_finish_reset (&da->ctx.sha512_256_ctx, digest);
 #ifndef NDEBUG
     da->ready_for_hashing = true;
 #endif /* _DEBUG */
 #endif /* ! mhd_SHA512_256_HAS_FINISH */
 #else  /* ! MHD_SUPPORT_SHA512_256 */
     mhd_UNREACHABLE ();
 #endif /* ! MHD_SUPPORT_SHA512_256 */
     break;
 
   case MHD_DIGEST_BASE_ALGO_INVALID:
   default:
     mhd_UNREACHABLE ();
     break;
   }
 #ifndef NDEBUG
   da->hashing = false;
 #endif /* _DEBUG */
 }
 
 
 /**
  * Reset the digest calculation structure and prepare for new calculation.
  *
  * @param da the structure to reset
  */
 mhd_static_inline MHD_FN_PAR_NONNULL_ALL_ void
 digest_reset (struct DigestAlgorithm *da)
 {
   mhd_assert (! da->uninitialised);
   mhd_assert (da->algo_selected);
   mhd_assert (! da->hashing);
   switch (da->algo)
   {
   case MHD_DIGEST_BASE_ALGO_MD5:
 #ifdef MHD_SUPPORT_MD5
 #  ifdef mhd_MD5_HAS_FINISH
     mhd_assert (! da->ready_for_hashing);
 #  else  /* ! mhd_MD5_HAS_FINISH */
     mhd_assert (da->ready_for_hashing);
 #  endif /* ! mhd_MD5_HAS_FINISH */
     mhd_MD5_reset (&(da->ctx.md5_ctx));
 #  ifndef NDEBUG
     da->ready_for_hashing = true;
 #  endif /* _DEBUG */
 #else  /* ! MHD_SUPPORT_MD5 */
     mhd_UNREACHABLE ();
 #endif /* ! MHD_SUPPORT_MD5 */
     break;
 
   case MHD_DIGEST_BASE_ALGO_SHA256:
 #ifdef MHD_SUPPORT_SHA256
 #ifdef mhd_SHA256_HAS_FINISH
     mhd_assert (! da->ready_for_hashing);
 #else  /* ! mhd_SHA256_HAS_FINISH */
     mhd_assert (da->ready_for_hashing);
 #endif /* ! mhd_SHA256_HAS_FINISH */
     mhd_SHA256_reset (&(da->ctx.sha256_ctx));
 #ifndef NDEBUG
     da->ready_for_hashing = true;
 #endif /* _DEBUG */
 #else  /* ! MHD_SUPPORT_SHA256 */
     mhd_UNREACHABLE ();
 #endif /* ! MHD_SUPPORT_SHA256 */
     break;
 
   case MHD_DIGEST_BASE_ALGO_SHA512_256:
 #ifdef MHD_SUPPORT_SHA512_256
 #  ifdef mhd_SHA512_256_HAS_FINISH
     mhd_assert (! da->ready_for_hashing);
 #  else  /* ! mhd_SHA512_256_HAS_FINISH */
     mhd_assert (da->ready_for_hashing);
 #  endif /* ! mhd_SHA512_256_HAS_FINISH */
     mhd_SHA512_256_reset (&(da->ctx.sha512_256_ctx));
 #  ifndef NDEBUG
     da->ready_for_hashing = true;
 #  endif /* _DEBUG */
 #else  /* ! MHD_SUPPORT_SHA512_256 */
     mhd_UNREACHABLE ();
 #endif /* ! MHD_SUPPORT_SHA512_256 */
     break;
 
   case MHD_DIGEST_BASE_ALGO_INVALID:
   default:
 #ifndef NDEBUG
     da->ready_for_hashing = false;
 #endif
     mhd_UNREACHABLE ();
     break;
   }
 }
 
 
 #if defined(mhd_MD5_HAS_EXT_ERROR) \
   || defined(mhd_SHA256_HAS_EXT_ERROR) \
   || defined(mhd_SHA512_256_HAS_EXT_ERROR)
 /**
  * Indicates that digest algorithm has external error status
  */
 #define mhd_DIGEST_HAS_EXT_ERROR 1
 #endif /* mhd_MD5_HAS_EXT_ERROR || mhd_SHA256_HAS_EXT_ERROR
           || mhd_SHA512_256_HAS_EXT_ERROR*/
 
 #ifdef mhd_DIGEST_HAS_EXT_ERROR
 /**
  * Get external error state.
  *
  * When external digest calculation used, an error may occur during
  * initialisation or hashing data. This function checks whether external
  * error has been reported for digest calculation.
  * @param da the digest calculation
  * @return 'true' if external error occurs,
  *         'false' otherwise
  */
 mhd_static_inline MHD_FN_PAR_NONNULL_ALL_ bool
 digest_has_error (struct DigestAlgorithm *da)
 {
   mhd_assert (! da->uninitialised);
   mhd_assert (da->algo_selected);
   switch (da->algo)
   {
   case MHD_DIGEST_BASE_ALGO_MD5:
 #ifdef MHD_SUPPORT_MD5
     return mhd_MD5_has_err (&(da->ctx.md5_ctx));
 #else  /* ! MHD_SUPPORT_MD5 */
     mhd_UNREACHABLE ();
 #endif /* ! MHD_SUPPORT_MD5 */
     break;
 
   case MHD_DIGEST_BASE_ALGO_SHA256:
 #ifdef MHD_SUPPORT_SHA256
     return mhd_SHA256_has_err (&(da->ctx.sha256_ctx));
 #else  /* ! MHD_SUPPORT_SHA256 */
     mhd_UNREACHABLE ();
 #endif /* ! MHD_SUPPORT_SHA256 */
     break;
 
   case MHD_DIGEST_BASE_ALGO_SHA512_256:
 #ifdef MHD_SUPPORT_SHA512_256
     return mhd_SHA512_256_has_err (&(da->ctx.sha512_256_ctx));
 #else  /* ! MHD_SUPPORT_SHA512_256 */
     mhd_UNREACHABLE ();
 #endif /* ! MHD_SUPPORT_SHA512_256 */
     break;
 
   case MHD_DIGEST_BASE_ALGO_INVALID:
   default:
     break;
   }
   mhd_UNREACHABLE ();
   return true;
 }
 
 
 #else  /* ! mhd_DIGEST_HAS_EXT_ERROR */
 #define digest_has_error(da) (((void) (da)), ! ! 0)
 #endif /* ! mhd_DIGEST_HAS_EXT_ERROR */
 
 
 /**
  * Calculate userdigest, return it as binary data.
  *
  * It is equal to H(A1) for non-session algorithms.
  *
  * MHD internal version.
  *
  * @param da the digest algorithm
  * @param username the username to use
  * @param username_len the length of the @a username
  * @param realm the realm to use
  * @param realm_len the length of the @a realm
  * @param password the password, must be zero-terminated
  * @param[out] ha1_bin the output buffer, must have at least
  *                     #digest_get_size(da) bytes available
  */
 mhd_static_inline MHD_FN_PAR_NONNULL_ALL_
 MHD_FN_PAR_IN_SIZE_ (2, 3) MHD_FN_PAR_IN_SIZE_ (4, 5)
 MHD_FN_PAR_CSTR_ (6) MHD_FN_PAR_OUT_ (7) void
 calc_userdigest (struct DigestAlgorithm *restrict da,
                  const char *restrict username, const size_t username_len,
                  const char *restrict realm, const size_t realm_len,
                  const char *restrict password,
                  uint8_t *ha1_bin)
 {
   mhd_assert (! da->uninitialised);
   mhd_assert (da->algo_selected);
   mhd_assert (! da->hashing);
   digest_update (da, username_len, username);
   digest_update_with_colon (da);
   digest_update (da, realm_len, realm);
   digest_update_with_colon (da);
   digest_update_str (da, password);
   digest_calc_hash (da, ha1_bin);
 }
 
 
 MHD_EXTERN_ MHD_FN_PURE_ MHD_FN_PAR_NONNULL_ALL_
 MHD_FN_PAR_CSTR_ (2) MHD_FN_PAR_CSTR_ (3) MHD_FN_PAR_CSTR_ (4)
 MHD_FN_PAR_OUT_SIZE_ (6,5) enum MHD_StatusCode
 MHD_digest_auth_calc_userdigest (enum MHD_DigestAuthAlgo algo,
                                  const char *MHD_RESTRICT username,
                                  const char *MHD_RESTRICT realm,
                                  const char *MHD_RESTRICT password,
                                  size_t bin_buf_size,
                                  void *MHD_RESTRICT userdigest_bin)
 {
   struct DigestAlgorithm da;
   enum MHD_StatusCode ret;
   if (! digest_init_one_time (&da, get_base_digest_algo (algo)))
     return MHD_SC_AUTH_DIGEST_ALGO_NOT_SUPPORTED;
 
   if (digest_get_size (&da) > bin_buf_size)
     ret = MHD_SC_OUT_BUFF_TOO_SMALL;
   else
   {
     calc_userdigest (&da,
                      username,
                      strlen (username),
                      realm,
                      strlen (realm),
                      password,
                      (uint8_t *) userdigest_bin);
     ret = digest_has_error (&da) ? MHD_SC_HASH_FAILED : MHD_SC_OK;
   }
   digest_deinit (&da);
 
   return ret;
 }
 
 
 /**
  * Calculate userhash, return it as binary data.
  *
  * MHD internal version.
  *
  * @param da the digest algorithm
  * @param username_len the length of the @a username
  * @param username the username to use
  * @param realm_len the length of the @a realm
  * @param realm the realm to use
  * @param[out] digest_bin the output buffer, must have at least
  *                        #MHD_digest_get_hash_size(algo) bytes available
  */
 mhd_static_inline MHD_FN_PAR_NONNULL_ALL_
 MHD_FN_PAR_IN_SIZE_ (3, 2) MHD_FN_PAR_IN_SIZE_ (5, 4) MHD_FN_PAR_OUT_ (6) void
 calc_userhash (struct DigestAlgorithm *da,
                const size_t username_len,
                const char *username,
                const size_t realm_len,
                const char *realm,
                uint8_t *digest_bin)
 {
   mhd_assert (! da->uninitialised);
   mhd_assert (da->algo_selected);
   mhd_assert (! da->hashing);
   digest_update (da, username_len, username);
   digest_update_with_colon (da);
   digest_update (da, realm_len, realm);
   digest_calc_hash (da, digest_bin);
 }
 
 
 MHD_EXTERN_ MHD_FN_PURE_ MHD_FN_PAR_NONNULL_ALL_
 MHD_FN_PAR_CSTR_ (2)
 MHD_FN_PAR_CSTR_ (3) MHD_FN_PAR_OUT_SIZE_ (5,4) enum MHD_StatusCode
 MHD_digest_auth_calc_userhash (enum MHD_DigestAuthAlgo algo,
                                const char *MHD_RESTRICT username,
                                const char *MHD_RESTRICT realm,
                                size_t bin_buf_size,
                                void *MHD_RESTRICT userhash_bin)
 {
   struct DigestAlgorithm da;
   enum MHD_StatusCode ret;
 
   if (! digest_init_one_time (&da, get_base_digest_algo (algo)))
     return MHD_SC_AUTH_DIGEST_ALGO_NOT_SUPPORTED;
   if (digest_get_size (&da) > bin_buf_size)
     ret = MHD_SC_OUT_BUFF_TOO_SMALL;
   else
   {
     calc_userhash (&da,
                    strlen (username),
                    username,
                    strlen (realm),
                    realm,
                    (uint8_t *) userhash_bin);
 
     ret = digest_has_error (&da) ? MHD_SC_HASH_FAILED : MHD_SC_OK;
   }
   digest_deinit (&da);
 
   return ret;
 }
 
 
 MHD_EXTERN_ MHD_FN_PURE_ MHD_FN_PAR_NONNULL_ALL_
 MHD_FN_PAR_CSTR_ (2)
 MHD_FN_PAR_CSTR_ (3) MHD_FN_PAR_OUT_SIZE_ (5,4) enum MHD_StatusCode
 MHD_digest_auth_calc_userhash_hex (
   enum MHD_DigestAuthAlgo algo,
   const char *MHD_RESTRICT username,
   const char *MHD_RESTRICT realm,
   size_t hex_buf_size,
   char userhash_hex[MHD_FN_PAR_DYN_ARR_SIZE_ (hex_buf_size)])
 {
   uint8_t userhash_bin[mhd_MAX_DIGEST] = { 0u /* mute compiler warning */ };
   size_t digest_size;
   enum MHD_StatusCode res;
 
   digest_size = digest_get_hash_size (algo);
   if (digest_size * 2 + 1 > hex_buf_size)
     return MHD_SC_OUT_BUFF_TOO_SMALL;
   res = MHD_digest_auth_calc_userhash (algo,
                                        username,
                                        realm,
                                        sizeof(userhash_bin),
                                        userhash_bin);
   if (MHD_SC_OK != res)
     return res;
 
   (void) mhd_bin_to_hex_z (userhash_bin,
                            digest_size,
                            userhash_hex);
   return MHD_SC_OK;
 }
 
 
 /**
  * Extract timestamp from the given nonce.
  * @param nonce the nonce to check in binary form
  * @return 'true' if timestamp was extracted,
  *         'false' if nonce does not have valid timestamp.
  */
 mhd_static_inline uint_fast32_t
 get_nonce_timestamp (const uint8_t nonce[mhd_AUTH_DIGEST_NONCE_BIN_SIZE])
 {
   return (uint_fast32_t)
          mhd_GET_32BIT_LE_UNALIGN (nonce + mhd_AUTH_DIGEST_NONCE_RAND_BIN_SIZE);
 }
 
 
 /**
  * The result of nonce-nc map array check.
  */
 enum mhd_CheckNonceNC
 {
   /**
    * The nonce and NC are OK (valid and NC was not used before).
    */
   mhd_CHECK_NONCENC_OK = MHD_DAUTH_OK,
 
   /**
    * The 'nonce' is too old, has been overwritten with newer 'nonce' in
    * the same slot or 'nc' value has been used already.
    * The validity of the 'nonce' was not be checked.
    */
   mhd_CHECK_NONCENC_STALE = MHD_DAUTH_NONCE_STALE,
 
   /**
    * The 'nonce' is wrong, it was not generated before.
    */
   mhd_CHECK_NONCENC_WRONG = MHD_DAUTH_NONCE_WRONG
 };
 
 
 /**
  * Check nonce-nc map array with the new nonce counter.
  *
  * @param d the master daemon object
  * @param noncelen the length of @a nonce, in characters
  * @param nonce the pointer that referenced hex nonce, does not need to be
  *              zero-terminated
  * @param nc the nonce counter
  * @param time_now the current timestamp
  * @return #MHD_DAUTH_NONCENC_OK if successful,
  *         #MHD_DAUTH_NONCENC_STALE if nonce is stale (or no nonce-nc array
  *         is available),
  *         #MHD_DAUTH_NONCENC_WRONG if nonce was not recodered in nonce-nc map
  *         array, while it should.
  */
 static MHD_FN_MUST_CHECK_RESULT_ MHD_FN_PAR_NONNULL_ALL_
 MHD_FN_PAR_IN_SIZE_ (3, 2) enum mhd_CheckNonceNC
 check_nonce_nc (struct MHD_Daemon *restrict d,
                 size_t noncelen,
                 const char *restrict nonce,
                 uint_fast32_t nc,
                 uint_fast32_t time_now)
 {
   uint8_t nonce_bin[mhd_AUTH_DIGEST_NONCE_BIN_SIZE];
   struct mhd_DaemonAuthDigestNonceData *nonce_slot;
   uint_fast32_t valid_time;
   uint_fast32_t slot_valid_time;
   enum mhd_CheckNonceNC ret;
 
   mhd_assert (! mhd_D_HAS_MASTER (d)); /* only master daemon should be used */
   mhd_assert (0 != noncelen);
   mhd_assert (0 != nc);
   if (mhd_AUTH_DIGEST_NONCE_LEN != noncelen)
     return mhd_CHECK_NONCENC_WRONG;
 
   if (mhd_AUTH_DIGEST_NONCE_BIN_SIZE !=
       mhd_hex_to_bin (nonce,
                       mhd_AUTH_DIGEST_NONCE_LEN,
                       nonce_bin))
     return mhd_CHECK_NONCENC_WRONG;
 
   if ((NULL != memchr (nonce, 'A', mhd_AUTH_DIGEST_NONCE_LEN))
       || (NULL != memchr (nonce, 'B', mhd_AUTH_DIGEST_NONCE_LEN))
       || (NULL != memchr (nonce, 'C', mhd_AUTH_DIGEST_NONCE_LEN))
       || (NULL != memchr (nonce, 'D', mhd_AUTH_DIGEST_NONCE_LEN))
       || (NULL != memchr (nonce, 'E', mhd_AUTH_DIGEST_NONCE_LEN))
       || (NULL != memchr (nonce, 'F', mhd_AUTH_DIGEST_NONCE_LEN)))
     return mhd_CHECK_NONCENC_WRONG;   /* Upper case chars are not produced by MHD */
 
   valid_time = get_nonce_timestamp (nonce_bin);
 
   nonce_slot = d->auth_dg.nonces
                + nonce_to_index (nonce_bin,
                                  d->auth_dg.cfg.nonces_num);
 
   mhd_mutex_lock_chk (&(d->auth_dg.nonces_lock));
 
   slot_valid_time = nonce_slot->valid_time;
   if ((0 == memcmp (nonce_slot->nonce,
                     nonce_bin,
                     sizeof(nonce_slot->nonce)))
       && (slot_valid_time == valid_time))
   {
     /* The nonce matches the stored nonce */
     if (nonce_slot->max_recvd_nc < nc)
     {
       /* 'nc' is larger, shift bitmask and bump limit */
       const uint_fast32_t jump_size =
         (uint_fast32_t) nc - nonce_slot->max_recvd_nc;
       if (64 > jump_size)
       {
         /* small jump, less than mask width */
         nonce_slot->nmask <<= jump_size;
         /* Set bit for the old 'nc' value */
         nonce_slot->nmask |= (UINT64_C (1) << (jump_size - 1));
       }
       else if (64 == jump_size)
         nonce_slot->nmask = (UINT64_C (1) << 63);
       else
         nonce_slot->nmask = 0; /* big jump, unset all bits in the mask */
       nonce_slot->max_recvd_nc = nc;
       ret = mhd_CHECK_NONCENC_OK;
     }
     else if (nonce_slot->max_recvd_nc == nc)
       /* 'nc' was already used */
       ret = mhd_CHECK_NONCENC_STALE;
     else /* (nonce_slot->max_recvd_nc > nc) */
     {
       /* Out-of-order 'nc' value. Check whether it was used before */
       const uint_fast32_t nc_delta = nonce_slot->max_recvd_nc - nc;
 
       mhd_ASSUME (0u != nc_delta); /* Guaranteed by if() branches */
 
       if (64u >= nc_delta)
       {
         const uint_fast64_t nc_bit = (UINT64_C (1) << (nc_delta - 1));
 
         mhd_ASSUME (0u != nc_bit);
         mhd_ASSUME (0u != (nc_bit & UINT64_C (0xFFFFFFFFFFFFFFFF)));
 
         if (0u == (nc_bit & nonce_slot->nmask))
         {
           /* 'nc' has not been used before. Set the bit. */
           nonce_slot->nmask |= nc_bit;
           ret = mhd_CHECK_NONCENC_OK;
         }
         else
           ret = mhd_CHECK_NONCENC_STALE; /* 'nc' has been used before */
       }
       else
         ret = mhd_CHECK_NONCENC_STALE; /* 'nc' is too old (more than 64 value before) */
     }
   }
   else
   {
     /* The nonce does not match the stored nonce */
     if (((valid_time - slot_valid_time) & UINT32_C (0xFFFFFFFF)) <=
         ((slot_valid_time - valid_time) & UINT32_C (0xFFFFFFFF)))
     {
       /* The stored nonce was generated before the checked nonce */
       ret = mhd_CHECK_NONCENC_WRONG;
     }
     else
     {
       /* The stored nonce was generated after the checked nonce */
       const uint_fast32_t nonce_gen_time =
         ((valid_time - d->auth_dg.cfg.nonce_tmout) & UINT32_C (0xFFFFFFFF));
       if (((time_now - nonce_gen_time) & UINT32_C (0xFFFFFFFF)) <
           ((nonce_gen_time - time_now) & UINT32_C (0xFFFFFFFF)))
         ret = mhd_CHECK_NONCENC_WRONG; /* The nonce is generated in "future" */
       else
         /* Probably the nonce has been overwritten with a newer nonce */
         ret = mhd_CHECK_NONCENC_STALE;
     }
   }
 
   mhd_mutex_unlock_chk (&(d->auth_dg.nonces_lock));
 
   return ret;
 }
 
 
 struct test_header_param
 {
   struct MHD_Request *request;
   size_t num_get_params;
 };
 
 /**
  * Test if the given key-value pair is in the headers for the
  * given request.
  *
  * @param cls the test context
  * @param name the name of the key
  * @param value the value of the key
  * @return 'true' if the key-value pair is in the headers,
  *         'false' if not
  */
 static MHD_FN_PAR_NONNULL_ (2) MHD_FN_PAR_NONNULL_ (3) bool
 test_header (void *restrict cls,
              const struct MHD_String *restrict name,
              const struct MHD_StringNullable *restrict value)
 {
   struct test_header_param *const param = (struct test_header_param *) cls;
   struct MHD_Request *req = param->request;
   struct mhd_RequestField *pos;
   size_t i;
 
   param->num_get_params++;
   i = 0;
   for (pos = mhd_DLINKEDL_GET_FIRST (req, fields);
        NULL != pos;
        pos = mhd_DLINKEDL_GET_NEXT (pos, fields))
   {
     if (MHD_VK_URI_QUERY_PARAM != pos->field.kind)
       continue;
     if (++i == param->num_get_params)
     {
       if (name->len != pos->field.nv.name.len)
         return false;
       if (value->len != pos->field.nv.value.len)
         return false;
       if (0 != name->len)
       {
         mhd_assert (NULL != name->cstr);
         mhd_assert (NULL != pos->field.nv.name.cstr);
         if (0 != memcmp (name->cstr,
                          pos->field.nv.name.cstr,
                          name->len))
           return false;
       }
       if (0 != value->len)
       {
         mhd_assert (NULL != value->cstr);
         mhd_assert (NULL != pos->field.nv.value.cstr);
         if (0 != memcmp (value->cstr,
                          pos->field.nv.value.cstr,
                          value->len))
           return false;
       }
       return true;
     }
   }
   return false;
 }
 
 
 /**
  * Check that the arguments given by the client as part
  * of the authentication header match the arguments we
  * got as part of the HTTP request URI.
  *
  * @param req the request with get arguments to compare against
  * @param args the copy of argument URI string (after "?" in URI), will be
  *             modified by this function
  * @return 'true' if the arguments match,
  *         'false' if not
  */
 static MHD_FN_PAR_NONNULL_ALL_
 MHD_FN_PAR_CSTR_ (3)
 MHD_FN_PAR_INOUT_SIZE_ (3, 2) bool
 check_argument_match (struct MHD_Request *restrict req,
                       size_t args_len,
                       char *restrict args)
 {
   struct mhd_RequestField *pos;
   struct test_header_param param;
 
   param.request = req;
   param.num_get_params = 0;
   if (! mhd_parse_uri_args (args_len,
                             args,
                             &test_header,
                             &param))
     return false;
 
   /* Check that the number of arguments matches */
   for (pos = mhd_DLINKEDL_GET_FIRST (req, fields);
        NULL != pos;
        pos = mhd_DLINKEDL_GET_NEXT (pos, fields))
   {
     if (MHD_VK_URI_QUERY_PARAM != pos->field.kind)
       continue;
     param.num_get_params--;
   }
 
   if (0 != param.num_get_params)
     return false; /* argument count mismatch */
 
   return true;
 }
 
 
 /**
  * Check that the URI provided by the client as part
  * of the authentication header match the real HTTP request URI.
  *
  * @param req the request to compare URI
  * @param uri the copy of URI in the authentication header, should point to
  *            modifiable buffer at least @a uri_len + 1 characters long,
  *            will be modified by this function, not valid upon return
  * @param uri_len the length of the @a uri string in characters
  * @return boolean true if the URIs match,
  *         boolean false if not
  */
 static MHD_FN_PAR_NONNULL_ALL_
 MHD_FN_PAR_INOUT_ (3) bool
 check_uri_match (struct MHD_Request *restrict req,
                  const size_t uri_len,
                  char *restrict uri)
 {
   char *qmark;
   char *args;
   size_t url_len; /* The part before '?' char */
   size_t args_len;
 
   if (uri_len != req->req_target_len)
     return false;
 
   uri[uri_len] = 0;
   qmark = (char *) memchr (uri,
                            '?',
                            uri_len);
   if (NULL != qmark)
   {
     *qmark = 0;
     url_len = (size_t) (qmark - uri);
   }
   else
     url_len = uri_len;
 
   /* Need to unescape URI before comparing with req->url */
   url_len = mhd_str_pct_decode_lenient_n (uri,
                                           url_len,
                                           uri,
                                           url_len,
                                           NULL);
   if ((url_len != req->url_len) ||
       (0 != memcmp (uri,
                     req->url,
                     url_len)))
     return false;
 
   args = (NULL != qmark) ? (qmark + 1) : uri + uri_len;
   args_len = (size_t) (uri + uri_len - args);
 
   if (! check_argument_match (req,
                               args_len,
                               args))
     return false;
 
   return true;
 }
 
 
 /**
  * The size of the unquoting buffer in stack
  */
 #define mhd_STATIC_UNQ_BUFFER_SIZE 128
 
 
 /**
  * Get the pointer to buffer with required size
  * @param tmp1 the first buffer with fixed size
  * @param[in,out] ptmp2 the pointer to pointer to malloc'ed buffer
  * @param[in,out] ptmp2_size the pointer to the size of the buffer pointed by @a ptmp2
  * @param required_size the required size in buffer
  * @return the pointer to the buffer or NULL if failed to allocate buffer with
  *         requested size
  */
 static MHD_FN_PAR_NONNULL_ALL_
 MHD_FN_PAR_INOUT_ (2) MHD_FN_PAR_INOUT_ (3) char *
 get_buffer_for_size (char tmp1[mhd_STATIC_UNQ_BUFFER_SIZE],
                      char **restrict ptmp2,
                      size_t *restrict ptmp2_size,
                      size_t required_size)
 {
   mhd_assert ((0 == *ptmp2_size) || (NULL != *ptmp2));
   mhd_assert ((NULL != *ptmp2) || (0 == *ptmp2_size));
   mhd_assert ((0 == *ptmp2_size) || \
               (mhd_STATIC_UNQ_BUFFER_SIZE < *ptmp2_size));
 
   if (required_size <= mhd_STATIC_UNQ_BUFFER_SIZE)
     return tmp1;
 
   if (required_size <= *ptmp2_size)
     return *ptmp2;
 
   if (required_size > mhd_AUTH_DIGEST_MAX_PARAM_SIZE)
     return NULL;
   if (NULL != *ptmp2)
     free (*ptmp2);
   *ptmp2 = (char *) malloc (required_size);
   if (NULL == *ptmp2)
     *ptmp2_size = 0;
   else
     *ptmp2_size = required_size;
   return *ptmp2;
 }
 
 
 /**
   * The result of parameter unquoting
   */
 enum mhd_GetUnqResult
 {
   mhd_UNQ_OK = MHD_DAUTH_OK,               /**< Got unquoted string */
   mhd_UNQ_TOO_LARGE = MHD_DAUTH_TOO_LARGE, /**< The string is too large to unquote */
   mhd_UNQ_OUT_OF_MEM = MHD_DAUTH_ERROR     /**< Out of memory error */
 };
 
 /**
  * Get Digest authorisation parameter as unquoted string.
  * @param param the parameter to process
  * @param[in,out] tmp1 the small buffer in stack
  * @param[in,out] ptmp2 the pointer to pointer to malloc'ed buffer
  * @param[in,out] ptmp2_size the pointer to the size of the buffer pointed by @a ptmp2
  * @param[out] unquoted the pointer to store the result, NOT zero terminated
  * @return enum code indicating result of the process
  */
 static MHD_FN_MUST_CHECK_RESULT_ MHD_FN_PAR_NONNULL_ALL_
 MHD_FN_PAR_OUT_ (2) MHD_FN_PAR_INOUT_ (3) MHD_FN_PAR_INOUT_ (4)
 MHD_FN_PAR_OUT_ (5) enum mhd_GetUnqResult
 get_unquoted_param (const struct mhd_RqDAuthParam *param,
                     char tmp1[mhd_STATIC_UNQ_BUFFER_SIZE],
                     char **restrict ptmp2,
                     size_t *restrict ptmp2_size,
                     struct mhd_BufferConst *restrict unquoted)
 {
   char *str;
   size_t len;
   mhd_assert (NULL != param->value.cstr);
   mhd_assert (0 != param->value.len);
 
   if (! param->quoted)
   {
     unquoted->data = param->value.cstr;
     unquoted->size = param->value.len;
     return mhd_UNQ_OK;
   }
   /* The value is present and is quoted, needs to be copied and unquoted */
   str = get_buffer_for_size (tmp1,
                              ptmp2,
                              ptmp2_size,
                              param->value.len);
   if (NULL == str)
     return (param->value.len > mhd_AUTH_DIGEST_MAX_PARAM_SIZE) ?
            mhd_UNQ_TOO_LARGE : mhd_UNQ_OUT_OF_MEM;
 
   len = mhd_str_unquote (param->value.cstr,
                          param->value.len,
                          str);
   unquoted->data = str;
   unquoted->size = len;
   mhd_assert (0 != unquoted->size);
   mhd_assert (unquoted->size < param->value.len);
   return mhd_UNQ_OK;
 }
 
 
 /**
  * Get copy of Digest authorisation parameter as unquoted string.
  * @param param the parameter to process
  * @param[in,out] tmp1 the small buffer in stack
  * @param[in,out] ptmp2 the pointer to pointer to malloc'ed buffer
  * @param[in,out] ptmp2_size the pointer to the size of the buffer pointed by @a ptmp2
  * @param[out] unquoted the pointer to store the result, NOT zero terminated,
  *                      but with enough space to zero-terminate
  * @return enum code indicating result of the process
  */
 static MHD_FN_MUST_CHECK_RESULT_ MHD_FN_PAR_NONNULL_ALL_
 MHD_FN_PAR_OUT_ (2) MHD_FN_PAR_INOUT_ (3) MHD_FN_PAR_INOUT_ (4)
 MHD_FN_PAR_OUT_ (5) enum mhd_GetUnqResult
 get_unquoted_param_copy (const struct mhd_RqDAuthParam *param,
                          char tmp1[mhd_STATIC_UNQ_BUFFER_SIZE],
                          char **restrict ptmp2,
                          size_t *restrict ptmp2_size,
                          struct mhd_Buffer *restrict unquoted)
 {
   mhd_assert (NULL != param->value.cstr);
   mhd_assert (0 != param->value.len);
 
   /* The value is present and is quoted, needs to be copied and unquoted */
   /* Allocate buffer with one more additional byte for zero-termination */
   unquoted->data =
     get_buffer_for_size (tmp1,
                          ptmp2,
                          ptmp2_size,
                          param->value.len + 1);
 
   if (NULL == unquoted->data)
     return (param->value.len + 1 > mhd_AUTH_DIGEST_MAX_PARAM_SIZE) ?
            mhd_UNQ_TOO_LARGE : mhd_UNQ_OUT_OF_MEM;
 
   if (! param->quoted)
   {
     memcpy (unquoted->data,
             param->value.cstr,
             param->value.len);
     unquoted->size = param->value.len;
     return mhd_UNQ_OK;
   }
 
   unquoted->size =
     mhd_str_unquote (param->value.cstr,
                      param->value.len,
                      unquoted->data);
   mhd_assert (0 != unquoted->size);
   mhd_assert (unquoted->size < param->value.len);
   return mhd_UNQ_OK;
 }
 
 
 /**
  * Check whether Digest Auth request parameter is equal to given string
  * @param param the parameter to check
  * @param str_len the length of the @a str
  * @param str the string to compare with, does not need to be zero-terminated
  * @return true is parameter is equal to the given string,
  *         false otherwise
  */
 mhd_static_inline MHD_FN_MUST_CHECK_RESULT_ MHD_FN_PAR_NONNULL_ALL_
 MHD_FN_PAR_IN_SIZE_ (3,2) bool
 is_param_equal (const struct mhd_RqDAuthParam *restrict param,
                 const size_t str_len,
                 const char *restrict str)
 {
   mhd_assert (NULL != param->value.cstr);
   mhd_assert (0 != param->value.len);
   if (param->quoted)
     return mhd_str_equal_quoted_bin_n (param->value.cstr,
                                        param->value.len,
                                        str,
                                        str_len);
   return (str_len == param->value.len) &&
          (0 == memcmp (str, param->value.cstr, str_len));
 }
 
 
 /**
  * Check whether Digest Auth request parameter is caseless equal to given string
  * @param param the parameter to check
  * @param str_len the length of the @a str
  * @param str the string to compare with, does not need to be zero-terminated
  * @return true is parameter is caseless equal to the given string,
  *         false otherwise
  */
 mhd_static_inline MHD_FN_MUST_CHECK_RESULT_ MHD_FN_PAR_NONNULL_ALL_
 MHD_FN_PAR_IN_SIZE_ (3,2) bool
 is_param_equal_caseless (const struct mhd_RqDAuthParam *restrict param,
                          const size_t str_len,
                          const char *restrict str)
 {
   mhd_assert (NULL != param->value.cstr);
   mhd_assert (0 != param->value.len);
   if (param->quoted)
     return mhd_str_equal_caseless_quoted_bin_n (param->value.cstr,
                                                 param->value.len,
                                                 str,
                                                 str_len);
   return (str_len == param->value.len) &&
          (mhd_str_equal_caseless_bin_n (str, param->value.cstr, str_len));
 }
 
 
 /**
  * Authenticates the authorization header sent by the client
  *
  * If RFC2069 mode is allowed by setting bit #MHD_DIGEST_AUTH_QOP_NONE in
  * @a mqop and the client uses this mode, then server generated nonces are
  * used as one-time nonces because nonce-count is not supported in this old RFC.
  * Communication in this mode is very inefficient, especially if the client
  * requests several resources one-by-one as for every request new nonce must be
  * generated and client repeat all requests twice (the first time to get a new
  * nonce and the second time to perform an authorised request).
  *
  * @param req the request handle
  * @param realm the realm for authorization of the client
  * @param username the username to be authenticated, must be in clear text
  *                 even if userhash is used by the client
  * @param password the password used in the authentication,
  *                 must be NULL if @a userdigest is not NULL
  * @param userdigest the precalculated binary hash of the string
  *                   "username:realm:password",
  *                   must be NULL if @a password is not NULL
  * @param max_nc the maximum allowed nc (Nonce Count) value, if client's nc
  *               exceeds the specified value then MHD_DAUTH_NONCE_STALE is
  *               returned;
  *               unlike #digest_auth_check_all() zero is treated as "no limit"
  * @param mqop the QOP to use
  * @param malgo digest algorithms allowed to use, fail if algorithm specified
  *               by the client is not allowed by this parameter
  * @param[out] pbuf the pointer to pointer to internally malloc'ed buffer,
  *                  to be freed if not NULL upon return
  * @return #MHD_DAUTH_OK if authenticated,
  *         error code otherwise.
  * @ingroup authentication
  */
 static MHD_FN_MUST_CHECK_RESULT_
 MHD_FN_PAR_NONNULL_ (1)
 MHD_FN_PAR_NONNULL_ (2) MHD_FN_PAR_CSTR_ (2)
 MHD_FN_PAR_NONNULL_ (3) MHD_FN_PAR_CSTR_ (3)
 MHD_FN_PAR_CSTR_ (4)
 enum MHD_DigestAuthResult
 digest_auth_check_all_inner (struct MHD_Request *restrict req,
                              const char *restrict realm,
                              const char *restrict username,
                              const char *restrict password,
                              const uint8_t *restrict userdigest,
                              uint_fast32_t max_nc,
                              enum MHD_DigestAuthMultiQOP mqop,
                              enum MHD_DigestAuthMultiAlgo malgo,
                              char **pbuf,
                              struct DigestAlgorithm *da)
 {
   struct MHD_Daemon *const daemon =
     mhd_daemon_get_master_daemon (
       mhd_CNTNR_PTR (req, struct MHD_Connection, rq)->daemon);
   enum MHD_DigestAuthAlgo c_algo; /**< Client's algorithm */
   enum MHD_DigestAuthQOP c_qop; /**< Client's QOP */
   unsigned int digest_size;
   uint8_t hash1_bin[mhd_MAX_DIGEST];
   uint8_t hash2_bin[mhd_MAX_DIGEST];
   uint_fast32_t nc;
   const struct mhd_AuthDigesReqParams *restrict params;
   /**
    * Temporal buffer in stack for unquoting and other needs
    */
   char tmp1[mhd_STATIC_UNQ_BUFFER_SIZE];
   char **const ptmp2 = pbuf;     /**< Temporal malloc'ed buffer for unquoting */
   size_t tmp2_size; /**< The size of @a tmp2 buffer */
   struct mhd_BufferConst unquoted;
   struct mhd_Buffer unq_copy;
   enum mhd_GetUnqResult unq_res;
   size_t username_len;
   size_t realm_len;
 
   mhd_assert ((NULL == password) != (NULL == userdigest));
 
   tmp2_size = 0;
 
   if (1)
   {
     enum MHD_StatusCode res;
 
     res = get_rq_auth_digest_params (req);
     if (MHD_SC_OK != res)
     {
       if (MHD_SC_AUTH_ABSENT == res)
         return MHD_DAUTH_HEADER_MISSING;
       else if (MHD_SC_CONNECTION_POOL_NO_MEM_AUTH_DATA == res)
         return MHD_DAUTH_ERROR;
       else if (MHD_SC_REQ_AUTH_DATA_BROKEN == res)
         return MHD_DAUTH_HEADER_BROKEN;
       else
         mhd_UNREACHABLE ();
     }
     params = req->auth.digest.rqp;
   }
   mhd_assert (NULL != params);
 
   /* ** Initial parameters checks and setup ** */
   /* Get client's algorithm */
   c_algo = params->algo;
   /* Check whether client's algorithm is allowed by function parameter */
   if (((unsigned int) c_algo) !=
       (((unsigned int) c_algo) & ((unsigned int) malgo)))
     return MHD_DAUTH_WRONG_ALGO;
   /* Check whether client's algorithm is supported */
   if (0 != (((unsigned int) c_algo) & MHD_DIGEST_AUTH_ALGO_SESSION))
     return MHD_DAUTH_UNSUPPORTED_ALGO;
 #ifndef MHD_SUPPORT_MD5
   if (0 != (((unsigned int) c_algo) & MHD_DIGEST_BASE_ALGO_MD5))
     return MHD_DAUTH_UNSUPPORTED_ALGO;
 #endif /* ! MHD_SUPPORT_MD5 */
 #ifndef MHD_SUPPORT_SHA256
   if (0 != (((unsigned int) c_algo) & MHD_DIGEST_BASE_ALGO_SHA256))
     return MHD_DAUTH_UNSUPPORTED_ALGO;
 #endif /* ! MHD_SUPPORT_SHA256 */
 #ifndef MHD_SUPPORT_SHA512_256
   if (0 != (((unsigned int) c_algo) & MHD_DIGEST_BASE_ALGO_SHA512_256))
     return MHD_DAUTH_UNSUPPORTED_ALGO;
 #endif /* ! MHD_SUPPORT_SHA512_256 */
   if (! digest_init_one_time (da, get_base_digest_algo (c_algo)))
     mhd_UNREACHABLE ();
   /* Check 'mqop' value */
   c_qop = params->qop;
   /* Check whether client's QOP is allowed by function parameter */
   if (((unsigned int) c_qop) !=
       (((unsigned int) c_qop) & ((unsigned int) mqop)))
     return MHD_DAUTH_WRONG_QOP;
   if (0 != (((unsigned int) c_qop) & MHD_DIGEST_AUTH_QOP_AUTH_INT))
     return MHD_DAUTH_UNSUPPORTED_QOP;
 
   digest_size = digest_get_size (da);
 
   /* ** A quick check for presence of all required parameters ** */
 
   if ((NULL == params->username.value.cstr) &&
       (NULL == params->username_ext.value.cstr))
     return MHD_DAUTH_HEADER_BROKEN;
   else if ((NULL != params->username.value.cstr) &&
            (NULL != params->username_ext.value.cstr))
     return MHD_DAUTH_HEADER_BROKEN; /* Parameters cannot be used together */
   else if ((NULL != params->username_ext.value.cstr) &&
            (mhd_DAUTH_EXT_PARAM_MIN_LEN > params->username_ext.value.len))
     return MHD_DAUTH_HEADER_BROKEN;  /* Broken extended notation */
   else if (params->userhash && (NULL == params->username.value.cstr))
     return MHD_DAUTH_HEADER_BROKEN;  /* Userhash cannot be used with extended notation */
   else if (params->userhash && (digest_size * 2 > params->username.value.len))
     return MHD_DAUTH_WRONG_USERNAME;  /* Too few chars for correct userhash */
   else if (params->userhash && (digest_size * 4 < params->username.value.len))
     return MHD_DAUTH_WRONG_USERNAME;  /* Too many chars for correct userhash */
 
   if (NULL == params->realm.value.cstr)
     return MHD_DAUTH_HEADER_BROKEN;
   else if (((NULL == userdigest) || params->userhash) &&
            (mhd_AUTH_DIGEST_MAX_PARAM_SIZE < params->realm.value.len))
     return MHD_DAUTH_TOO_LARGE; /* Realm is too large and should be used in hash calculations */
 
   if (MHD_DIGEST_AUTH_QOP_NONE != c_qop)
   {
     if (NULL == params->nc.value.cstr)
       return MHD_DAUTH_HEADER_BROKEN;
     else if (0 == params->nc.value.len)
       return MHD_DAUTH_HEADER_BROKEN;
     else if (4 * 8 < params->nc.value.len) /* Four times more than needed */
       return MHD_DAUTH_HEADER_BROKEN;
 
     if (NULL == params->cnonce.value.cstr)
       return MHD_DAUTH_HEADER_BROKEN;
     else if (0 == params->cnonce.value.len)
       return MHD_DAUTH_HEADER_BROKEN;
     else if (mhd_AUTH_DIGEST_MAX_PARAM_SIZE < params->cnonce.value.len)
       return MHD_DAUTH_TOO_LARGE;
   }
 
   /* The QOP parameter was checked already */
 
   if (NULL == params->uri.value.cstr)
     return MHD_DAUTH_HEADER_BROKEN;
   else if (0 == params->uri.value.len)
     return MHD_DAUTH_HEADER_BROKEN;
   else if (mhd_AUTH_DIGEST_MAX_PARAM_SIZE < params->uri.value.len)
     return MHD_DAUTH_TOO_LARGE;
 
   if (NULL == params->nonce.value.cstr)
     return MHD_DAUTH_HEADER_BROKEN;
   else if (0 == params->nonce.value.len)
     return MHD_DAUTH_HEADER_BROKEN;
   else if (mhd_AUTH_DIGEST_NONCE_LEN * 2 < params->nonce.value.len)
     return MHD_DAUTH_NONCE_WRONG;
 
   if (NULL == params->response.value.cstr)
     return MHD_DAUTH_HEADER_BROKEN;
   else if (0 == params->response.value.len)
     return MHD_DAUTH_HEADER_BROKEN;
   else if (digest_size * 4 < params->response.value.len)
     return MHD_DAUTH_RESPONSE_WRONG;
 
   /* ** Check simple parameters match ** */
 
   /* Check 'algorithm' */
   /* The 'algorithm' was checked at the start of the function */
   /* 'algorithm' valid */
 
   /* Check 'qop' */
   /* The 'qop' was checked at the start of the function */
   /* 'qop' valid */
 
   /* Check 'realm' */
   realm_len = strlen (realm);
   if (! is_param_equal (&params->realm,
                         realm_len,
                         realm))
     return MHD_DAUTH_WRONG_REALM;
   /* 'realm' valid */
 
   /* Check 'username' */
   username_len = strlen (username);
   if (! params->userhash)
   {
     if (NULL != params->username.value.cstr)
     { /* Username in standard notation */
       if (! is_param_equal (&params->username, username_len, username))
         return MHD_DAUTH_WRONG_USERNAME;
     }
     else
     { /* Username in extended notation */
       char *r_uname;
       size_t buf_size = params->username_ext.value.len;
       ssize_t res;
 
       mhd_assert (NULL != params->username_ext.value.cstr);
       mhd_assert (mhd_DAUTH_EXT_PARAM_MIN_LEN <= buf_size); /* It was checked already */
       buf_size += 1; /* For zero-termination */
       buf_size -= mhd_DAUTH_EXT_PARAM_MIN_LEN;
       r_uname = get_buffer_for_size (tmp1, ptmp2, &tmp2_size, buf_size);
       if (NULL == r_uname)
         return (mhd_AUTH_DIGEST_MAX_PARAM_SIZE < buf_size) ?
                MHD_DAUTH_TOO_LARGE : MHD_DAUTH_ERROR;
       res = get_rq_extended_uname_copy_z (params->username_ext.value.cstr,
                                           params->username_ext.value.len,
                                           r_uname, buf_size);
       if (0 > res)
         return MHD_DAUTH_HEADER_BROKEN; /* Broken extended notation */
       if ((username_len != (size_t) res) ||
           (0 != memcmp (username, r_uname, username_len)))
         return MHD_DAUTH_WRONG_USERNAME;
     }
   }
   else
   { /* Userhash */
     mhd_assert (NULL != params->username.value.cstr);
     calc_userhash (da,
                    username_len,
                    username,
                    realm_len,
                    realm,
                    hash1_bin);
     if (digest_has_error (da))
       return MHD_DAUTH_ERROR;
     mhd_assert (sizeof (tmp1) >= (2 * digest_size));
     mhd_bin_to_hex (hash1_bin, digest_size, tmp1);
     if (! is_param_equal_caseless (&params->username, 2 * digest_size, tmp1))
       return MHD_DAUTH_WRONG_USERNAME;
     /* To simplify the logic, the digest is reset here instead of resetting
        before the next hash calculation. */
     digest_reset (da);
   }
   /* 'username' valid */
 
   /* ** Do basic nonce and nonce-counter checks (size, timestamp) ** */
 
   /* Get 'nc' digital value */
   nc = 0;
   switch (get_rq_nc (params,
                      &nc))
   {
   case mhd_GET_RQ_NC_NONE:
     if (MHD_DIGEST_AUTH_QOP_NONE != c_qop)
       return MHD_DAUTH_HEADER_BROKEN;
     nc = 1; /* Force 'nc' value */
     break;
   case mhd_GET_RQ_NC_VALID:
     if (MHD_DIGEST_AUTH_QOP_NONE == c_qop)
       return MHD_DAUTH_HEADER_BROKEN;
     break;
   case mhd_GET_RQ_NC_TOO_LONG:
   case mhd_GET_RQ_NC_TOO_LARGE:
     return MHD_DAUTH_NONCE_STALE;
     break;
   case mhd_GET_RQ_NC_BROKEN:
     return MHD_DAUTH_HEADER_BROKEN;
     break;
   default:
     mhd_UNREACHABLE ();
     break;
   }
   if (0 == nc)
     return MHD_DAUTH_HEADER_BROKEN;
   if (0 == max_nc)
     max_nc = daemon->auth_dg.cfg.def_max_nc;
   if (max_nc < nc)
     return MHD_DAUTH_NONCE_STALE;    /* Too large 'nc' value */
   /* Got 'nc' digital value */
 
   /* Get 'nonce' with basic checks */
   unq_res = get_unquoted_param (&params->nonce, tmp1, ptmp2, &tmp2_size,
                                 &unquoted);
   if (mhd_UNQ_TOO_LARGE == unq_res)
     return MHD_DAUTH_TOO_LARGE;
   if (mhd_UNQ_OUT_OF_MEM == unq_res)
     return MHD_DAUTH_ERROR;
 
 
   switch (check_nonce_nc (daemon,
                           unquoted.size,
                           unquoted.data,
                           nc,
                           (uint_fast32_t)
                           ((mhd_monotonic_msec_counter () / 1000)
                            & UINT32_C (0xFFFFFFFF))))
   {
   case mhd_CHECK_NONCENC_OK:
     break;
   case mhd_CHECK_NONCENC_STALE:
     return MHD_DAUTH_NONCE_STALE;
   case mhd_CHECK_NONCENC_WRONG:
     return MHD_DAUTH_NONCE_WRONG;
   default:
     mhd_UNREACHABLE ();
     break;
   }
   /* The nonce was generated by MHD, is not stale and nonce-nc combination has
      not been used before */
 
   /* ** Build H(A2) and check URI match in the header and in the request ** */
 
   /* Get 'uri' */
   mhd_assert (! da->hashing);
   digest_update (da, req->method.len, req->method.cstr);
   digest_update_with_colon (da);
 #if 0
   /* TODO: add support for "auth-int" */
   digest_update_str (da, hentity);
   digest_update_with_colon (da);
 #endif
   unq_res = get_unquoted_param_copy (&params->uri, tmp1, ptmp2, &tmp2_size,
                                      &unq_copy);
   if (mhd_UNQ_TOO_LARGE == unq_res)
     return MHD_DAUTH_TOO_LARGE;
   if (mhd_UNQ_OUT_OF_MEM == unq_res)
     return MHD_DAUTH_ERROR;
 
   digest_update_buf (da, &unq_copy);
   /* The next check will modify copied URI string */
   if (! check_uri_match (req, unq_copy.size, unq_copy.data))
     return MHD_DAUTH_WRONG_URI;
   digest_calc_hash (da, hash2_bin);
 #ifdef mhd_DIGEST_HAS_EXT_ERROR
   /* Skip digest calculation external error check, the next one checks both */
 #endif /* mhd_DIGEST_HAS_EXT_ERROR */
   /* Got H(A2) */
 
   /* ** Build H(A1) ** */
   if (NULL == userdigest)
   {
     mhd_assert (! da->hashing);
     digest_reset (da);
     calc_userdigest (da,
                      username, username_len,
                      realm, realm_len,
                      password,
                      hash1_bin);
   }
   /* TODO: support '-sess' versions */
 #ifdef mhd_DIGEST_HAS_EXT_ERROR
   if (digest_has_error (da))
     return MHD_DAUTH_ERROR;
 #endif /* mhd_DIGEST_HAS_EXT_ERROR */
   /* Got H(A1) */
 
   /* **  Check 'response' ** */
 
   mhd_assert (! da->hashing);
   digest_reset (da);
   /* Update digest with H(A1) */
   mhd_assert (sizeof (tmp1) >= (digest_size * 2));
   if (NULL == userdigest)
     mhd_bin_to_hex (hash1_bin, digest_size, tmp1);
   else
     mhd_bin_to_hex (userdigest, digest_size, tmp1);
   digest_update (da, digest_size * 2, (const uint8_t *) tmp1);
 
   /* H(A1) is not needed anymore, reuse the buffer.
    * Use hash1_bin for the client's 'response' decoded to binary form. */
   unq_res = get_unquoted_param (&params->response, tmp1, ptmp2, &tmp2_size,
                                 &unquoted);
   if (mhd_UNQ_TOO_LARGE == unq_res)
     return MHD_DAUTH_TOO_LARGE;
   if (mhd_UNQ_OUT_OF_MEM == unq_res)
     return MHD_DAUTH_ERROR;
   if (digest_size != mhd_hex_to_bin (unquoted.data, unquoted.size, hash1_bin))
     return MHD_DAUTH_RESPONSE_WRONG;
 
   /* Update digest with ':' */
   digest_update_with_colon (da);
   /* Update digest with 'nonce' text value */
   unq_res = get_unquoted_param (&params->nonce, tmp1, ptmp2, &tmp2_size,
                                 &unquoted);
   if (mhd_UNQ_TOO_LARGE == unq_res)
     return MHD_DAUTH_TOO_LARGE;
   if (mhd_UNQ_OUT_OF_MEM == unq_res)
     return MHD_DAUTH_ERROR;
   digest_update_cbuf (da, &unquoted);
   /* Update digest with ':' */
   digest_update_with_colon (da);
   if (MHD_DIGEST_AUTH_QOP_NONE != c_qop)
   {
     /* Update digest with 'nc' text value */
     unq_res = get_unquoted_param (&params->nc, tmp1, ptmp2, &tmp2_size,
                                   &unquoted);
     if (mhd_UNQ_TOO_LARGE == unq_res)
       return MHD_DAUTH_TOO_LARGE;
     if (mhd_UNQ_OUT_OF_MEM == unq_res)
       return MHD_DAUTH_ERROR;
     digest_update_cbuf (da, &unquoted);
     /* Update digest with ':' */
     digest_update_with_colon (da);
     /* Update digest with 'cnonce' value */
     unq_res = get_unquoted_param (&params->cnonce, tmp1, ptmp2, &tmp2_size,
                                   &unquoted);
     if (mhd_UNQ_TOO_LARGE == unq_res)
       return MHD_DAUTH_TOO_LARGE;
     if (mhd_UNQ_OUT_OF_MEM == unq_res)
       return MHD_DAUTH_ERROR;
     digest_update_cbuf (da, &unquoted);
     /* Update digest with ':' */
     digest_update_with_colon (da);
     /* Update digest with 'qop' value */
     unq_res = get_unquoted_param (&params->qop_raw, tmp1, ptmp2, &tmp2_size,
                                   &unquoted);
     if (mhd_UNQ_TOO_LARGE == unq_res)
       return MHD_DAUTH_TOO_LARGE;
     if (mhd_UNQ_OUT_OF_MEM == unq_res)
       return MHD_DAUTH_ERROR;
     digest_update_cbuf (da, &unquoted);
     /* Update digest with ':' */
     digest_update_with_colon (da);
   }
   /* Update digest with H(A2) */
   mhd_bin_to_hex (hash2_bin, digest_size, tmp1);
   digest_update (da, digest_size * 2, (const uint8_t *) tmp1);
 
   /* H(A2) is not needed anymore, reuse the buffer.
    * Use hash2_bin for the calculated response in binary form */
   digest_calc_hash (da, hash2_bin);
 #ifdef mhd_DIGEST_HAS_EXT_ERROR
   if (digest_has_error (da))
     return MHD_DAUTH_ERROR;
 #endif /* mhd_DIGEST_HAS_EXT_ERROR */
 
   if (0 != memcmp (hash1_bin, hash2_bin, digest_size))
     return MHD_DAUTH_RESPONSE_WRONG;
 
   return MHD_DAUTH_OK;
 }
 
 
 /**
  * Authenticates the authorization header sent by the client
  *
  * If RFC2069 mode is allowed by setting bit #MHD_DIGEST_AUTH_QOP_NONE in
  * @a mqop and the client uses this mode, then server generated nonces are
  * used as one-time nonces because nonce-count is not supported in this old RFC.
  * Communication in this mode is very inefficient, especially if the client
  * requests several resources one-by-one as for every request new nonce must be
  * generated and client repeat all requests twice (the first time to get a new
  * nonce and the second time to perform an authorised request).
  *
  * @param req the request handle
  * @param realm the realm for authorization of the client
  * @param username the username to be authenticated, must be in clear text
  *                 even if userhash is used by the client
  * @param password the password used in the authentication,
  *                 must be NULL if @a userdigest is not NULL
  * @param userdigest the precalculated binary hash of the string
  *                   "username:realm:password",
  *                   must be NULL if @a password is not NULL
  * @param max_nc the maximum allowed nc (Nonce Count) value, if client's nc
  *               exceeds the specified value then MHD_DAUTH_NONCE_STALE is
  *               returned;
  *               if set to zero then daemon's default value is used
  * @param mqop the QOP to use
  * @param malgo digest algorithms allowed to use, fail if algorithm specified
  *               by the client is not allowed by this parameter
  * @return #MHD_DAUTH_OK if authenticated,
  *         error code otherwise.
  * @ingroup authentication
  */
 static enum MHD_DigestAuthResult
 digest_auth_check_all (struct MHD_Request *restrict req,
                        const char *restrict realm,
                        const char *restrict username,
                        const char *restrict password,
                        const uint8_t *restrict userdigest,
                        uint_fast32_t max_nc,
                        enum MHD_DigestAuthMultiQOP mqop,
                        enum MHD_DigestAuthMultiAlgo malgo)
 {
   enum MHD_DigestAuthResult res;
   char *buf;
   struct DigestAlgorithm da;
 
   buf = NULL;
   digest_setup_zero (&da);
   res = digest_auth_check_all_inner (req,
                                      realm,
                                      username,
                                      password,
                                      userdigest,
                                      max_nc,
                                      mqop,
                                      malgo,
                                      &buf,
                                      &da);
   digest_deinit (&da);
   if (NULL != buf)
     free (buf);
 
   return res;
 }
 
 
 /**
  * Authenticates the authorization header sent by the client.
  *
  * If RFC2069 mode is allowed by setting bit #MHD_DIGEST_AUTH_QOP_NONE in
  * @a mqop and the client uses this mode, then server generated nonces are
  * used as one-time nonces because nonce-count is not supported in this old RFC.
  * Communication in this mode is very inefficient, especially if the client
  * requests several resources one-by-one as for every request a new nonce must
  * be generated and client repeats all requests twice (first time to get a new
  * nonce and second time to perform an authorised request).
  *
  * @param request the request
  * @param realm the realm for authorization of the client
  * @param username the username to be authenticated, must be in clear text
  *                 even if userhash is used by the client
  * @param password the password matching the @a username (and the @a realm)
  * @param max_nc the maximum allowed nc (Nonce Count) value, if client's nc
  *               exceeds the specified value then MHD_DAUTH_NONCE_STALE is
  *               returned;
  *               if zero is specified then daemon default value is used.
  * @param mqop the QOP to use
  * @param malgo digest algorithms allowed to use, fail if algorithm used
  *               by the client is not allowed by this parameter
  * @return #MHD_DAUTH_OK if authenticated,
  *         the error code otherwise
  * @ingroup authentication
  */
 MHD_EXTERN_ MHD_FN_PAR_NONNULL_ALL_
 MHD_FN_PAR_CSTR_ (2) MHD_FN_PAR_CSTR_ (3) MHD_FN_PAR_CSTR_ (4)
 enum MHD_DigestAuthResult
 MHD_digest_auth_check (struct MHD_Request *MHD_RESTRICT request,
                        const char *MHD_RESTRICT realm,
                        const char *MHD_RESTRICT username,
                        const char *MHD_RESTRICT password,
                        uint_fast32_t max_nc,
                        enum MHD_DigestAuthMultiQOP mqop,
                        enum MHD_DigestAuthMultiAlgo malgo)
 {
   return digest_auth_check_all (request,
                                 realm,
                                 username,
                                 password,
                                 NULL,
                                 max_nc,
                                 mqop,
                                 malgo);
 }
 
 
 MHD_EXTERN_ MHD_FN_PAR_NONNULL_ALL_
 MHD_FN_PAR_CSTR_ (2)
 MHD_FN_PAR_CSTR_ (3)
 MHD_FN_PAR_IN_SIZE_ (5, 4) enum MHD_DigestAuthResult
 MHD_digest_auth_check_digest (struct MHD_Request *MHD_RESTRICT request,
                               const char *MHD_RESTRICT realm,
                               const char *MHD_RESTRICT username,
                               size_t userdigest_size,
                               const void *MHD_RESTRICT userdigest,
                               uint_fast32_t max_nc,
                               enum MHD_DigestAuthMultiQOP mqop,
                               enum MHD_DigestAuthMultiAlgo malgo)
 {
   if (1 != (((0 != (((unsigned int) malgo) \
                     & MHD_DIGEST_BASE_ALGO_MD5)) ? 1 : 0)
             + ((0 != (((unsigned int) malgo) \
                       & MHD_DIGEST_BASE_ALGO_SHA256)) ? 1 : 0)
             + ((0 != (((unsigned int) malgo) \
                       & MHD_DIGEST_BASE_ALGO_SHA512_256)) ? 1 : 0)))
     return MHD_DAUTH_UNSUPPORTED_ALGO;
 
 #ifndef MHD_SUPPORT_MD5
   if (0 != (((unsigned int) malgo) & MHD_DIGEST_BASE_ALGO_MD5))
     return MHD_DAUTH_UNSUPPORTED_ALGO;
 #endif /* ! MHD_SUPPORT_MD5 */
 #ifndef MHD_SUPPORT_SHA256
   if (0 != (((unsigned int) malgo) & MHD_DIGEST_BASE_ALGO_SHA256))
     return MHD_DAUTH_UNSUPPORTED_ALGO;
 #endif /* ! MHD_SUPPORT_SHA256 */
 #ifndef MHD_SUPPORT_SHA512_256
   if (0 != (((unsigned int) malgo) & MHD_DIGEST_BASE_ALGO_SHA512_256))
     return MHD_DAUTH_UNSUPPORTED_ALGO;
 #endif /* ! MHD_SUPPORT_SHA512_256 */
 
   if (digest_get_hash_size ((enum MHD_DigestAuthAlgo) malgo) !=
       userdigest_size)
     return MHD_DAUTH_INVALID_USERDIGEST_SIZE;
 
   return digest_auth_check_all (request,
                                 realm,
                                 username,
                                 NULL,
                                 (const uint8_t *) userdigest,
                                 max_nc,
                                 mqop,
                                 malgo);
 }