libmicrohttpd2

libtest_convenience_server_reply.c (26780B)

---

 /* 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) 2024 Christian Grothoff
   Copyright (C) 2024 Evgeny Grin (Karlson2k)
 
   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 libtest_convenience_server_reply.c
  * @brief convenience functions that generate
  *   replies from the server for libtest users
  * @author Christian Grothoff
  */
 #include "libtest.h"
 #include <pthread.h>
 #include <stdbool.h>
 #include <fcntl.h>
 #include <stdio.h>
 #include <unistd.h>
 #include <errno.h>
 #include <curl/curl.h>
 #include <assert.h>
 
 #ifndef CURL_VERSION_BITS
 #  define CURL_VERSION_BITS(x,y,z) ((x) << 16 | (y) << 8 | (z))
 #endif
 #ifndef CURL_AT_LEAST_VERSION
 #  define CURL_AT_LEAST_VERSION(x,y,z) \
         (LIBCURL_VERSION_NUM >= CURL_VERSION_BITS (x, y, z))
 #endif
 
 const struct MHD_Action *
 MHDT_server_reply_text (
   void *cls,
   struct MHD_Request *MHD_RESTRICT request,
   const struct MHD_String *MHD_RESTRICT path,
   enum MHD_HTTP_Method method,
   uint_fast64_t upload_size)
 {
   const char *text = cls;
 
   (void) path; (void) method; (void) upload_size; /* Unused */
 
   return MHD_action_from_response (
     request,
     MHD_response_from_buffer_static (MHD_HTTP_STATUS_OK,
                                      strlen (text),
                                      text));
 }
 
 
 const struct MHD_Action *
 MHDT_server_reply_file (
   void *cls,
   struct MHD_Request *MHD_RESTRICT request,
   const struct MHD_String *MHD_RESTRICT path,
   enum MHD_HTTP_Method method,
   uint_fast64_t upload_size)
 {
   const char *text = cls;
   size_t tlen = strlen (text);
   char fn[] = "/tmp/mhd-test-XXXXXX";
   int fd;
 
   (void) path; (void) method; (void) upload_size; /* Unused */
 
   fd = mkstemp (fn);
   if (-1 == fd)
   {
     fprintf (stderr,
              "Failed to mkstemp() temporary file\n");
     return MHD_action_abort_request (request);
   }
   if (((ssize_t) tlen) != write (fd, text, tlen))
   {
     fprintf (stderr,
              "Failed to write() temporary file in one go: %s\n",
              strerror (errno));
     return MHD_action_abort_request (request);
   }
   fsync (fd);
   if (0 != remove (fn))
   {
     fprintf (stderr,
              "Failed to remove() temporary file %s: %s\n",
              fn,
              strerror (errno));
   }
   return MHD_action_from_response (
     request,
     MHD_response_from_fd (MHD_HTTP_STATUS_OK,
                           fd,
                           0 /* offset */,
                           tlen));
 }
 
 
 const struct MHD_Action *
 MHDT_server_reply_with_header (
   void *cls,
   struct MHD_Request *MHD_RESTRICT request,
   const struct MHD_String *MHD_RESTRICT path,
   enum MHD_HTTP_Method method,
   uint_fast64_t upload_size)
 {
   const char *header = cls;
   size_t hlen = strlen (header) + 1;
   char name[hlen];
   const char *colon = strchr (header, ':');
   const char *value;
   struct MHD_Response *resp;
 
   (void) path; (void) method; (void) upload_size; /* Unused */
 
   memcpy (name,
           header,
           hlen);
   name[colon - header] = '\0';
   value = &name[colon - header + 1];
 
   resp = MHD_response_from_empty (MHD_HTTP_STATUS_NO_CONTENT);
   if (MHD_SC_OK !=
       MHD_response_add_header (resp,
                                name,
                                value))
   {
     MHD_response_destroy (resp);
     return MHD_action_abort_request (request);
   }
   return MHD_action_from_response (
     request,
     resp);
 }
 
 
 const struct MHD_Action *
 MHDT_server_reply_check_query (
   void *cls,
   struct MHD_Request *MHD_RESTRICT request,
   const struct MHD_String *MHD_RESTRICT path,
   enum MHD_HTTP_Method method,
   uint_fast64_t upload_size)
 {
   const char *equery = cls;
   size_t qlen = strlen (equery) + 1;
   char qc[qlen];
 
   (void) path; (void) method; (void) upload_size; /* Unused */
 
   memcpy (qc,
           equery,
           qlen);
   for (const char *tok = strtok (qc, "&");
        NULL != tok;
        tok = strtok (NULL, "&"))
   {
     const char *end;
     struct MHD_StringNullable sn;
     const char *val;
 
     end = strchr (tok, '=');
     if (NULL == end)
     {
       end = &tok[strlen (tok)];
       val = NULL;
     }
     else
     {
       val = end + 1;
     }
     {
       size_t alen = (size_t) (end - tok);
       char arg[alen + 1];
 
       memcpy (arg,
               tok,
               alen);
       arg[alen] = '\0';
       if (MHD_NO ==
           MHD_request_get_value (request,
                                  MHD_VK_URI_QUERY_PARAM,
                                  arg,
                                  &sn))
       {
         fprintf (stderr,
                  "NULL returned for query key %s\n",
                  arg);
         return MHD_action_abort_request (request);
       }
       if (NULL == val)
       {
         if (NULL != sn.cstr)
         {
           fprintf (stderr,
                    "NULL expected for value for query key %s, got %s\n",
                    arg,
                    sn.cstr);
           return MHD_action_abort_request (request);
         }
       }
       else
       {
         if (NULL == sn.cstr)
         {
           fprintf (stderr,
                    "%s expected for value for query key %s, got NULL\n",
                    val,
                    arg);
           return MHD_action_abort_request (request);
         }
         if (0 != strcmp (val,
                          sn.cstr))
         {
           fprintf (stderr,
                    "%s expected for value for query key %s, got %s\n",
                    val,
                    arg,
                    sn.cstr);
           return MHD_action_abort_request (request);
         }
       }
     }
   }
 
   return MHD_action_from_response (
     request,
     MHD_response_from_empty (
       MHD_HTTP_STATUS_NO_CONTENT));
 }
 
 
 const struct MHD_Action *
 MHDT_server_reply_check_header (
   void *cls,
   struct MHD_Request *MHD_RESTRICT request,
   const struct MHD_String *MHD_RESTRICT path,
   enum MHD_HTTP_Method method,
   uint_fast64_t upload_size)
 {
   const char *want = cls;
   size_t wlen = strlen (want) + 1;
   char key[wlen];
   const char *colon = strchr (want, ':');
   struct MHD_StringNullable have;
   const char *value;
 
   (void) path; (void) method; (void) upload_size; /* Unused */
 
   memcpy (key,
           want,
           wlen);
   if (NULL != colon)
   {
     key[colon - want] = '\0';
     value = &key[colon - want + 1];
   }
   else
   {
     value = NULL;
   }
   if (MHD_NO ==
       MHD_request_get_value (request,
                              MHD_VK_HEADER,
                              key,
                              &have))
   {
     fprintf (stderr,
              "Missing client header `%s'\n",
              want);
     return MHD_action_abort_request (request);
   }
   if (NULL == value)
   {
     if (NULL != have.cstr)
     {
       fprintf (stderr,
                "Have unexpected client header `%s': `%s'\n",
                key,
                have.cstr);
       return MHD_action_abort_request (request);
     }
   }
   else
   {
     if (NULL == have.cstr)
     {
       fprintf (stderr,
                "Missing value for client header `%s'\n",
                want);
       return MHD_action_abort_request (request);
     }
     if (0 != strcmp (have.cstr,
                      value))
     {
       fprintf (stderr,
                "Client HTTP header `%s' was expected to be `%s' but is `%s'\n",
                key,
                value,
                have.cstr);
       return MHD_action_abort_request (request);
     }
   }
   return MHD_action_from_response (
     request,
     MHD_response_from_empty (
       MHD_HTTP_STATUS_NO_CONTENT));
 }
 
 
 /**
  * Function to process data uploaded by a client.
  *
  * @param cls the payload we expect to be uploaded as a 0-terminated string
  * @param request the request is being processed
  * @param content_data_size the size of the @a content_data,
  *                          zero when all data have been processed
  * @param[in] content_data the uploaded content data,
  *                         may be modified in the callback,
  *                         valid only until return from the callback,
  *                         NULL when all data have been processed
  * @return action specifying how to proceed:
  *         #MHD_upload_action_continue() to continue upload (for incremental
  *         upload processing only),
  *         #MHD_upload_action_suspend() to stop reading the upload until
  *         the request is resumed,
  *         #MHD_upload_action_abort_request() to close the socket,
  *         or a response to discard the rest of the upload and transmit
  *         the response
  * @ingroup action
  */
 static const struct MHD_UploadAction *
 check_upload_cb (void *cls,
                  struct MHD_Request *request,
                  size_t content_data_size,
                  void *content_data)
 {
   const char *want = cls;
   size_t wlen = strlen (want);
 
   if (content_data_size != wlen)
   {
     fprintf (stderr,
              "Invalid body size given to full upload callback\n");
     return MHD_upload_action_abort_request (request);
   }
   if (0 != memcmp (want,
                    content_data,
                    wlen))
   {
     fprintf (stderr,
              "Invalid body data given to full upload callback\n");
     return MHD_upload_action_abort_request (request);
   }
   /* success! */
   return MHD_upload_action_from_response (
     request,
     MHD_response_from_empty (
       MHD_HTTP_STATUS_NO_CONTENT));
 }
 
 
 const struct MHD_Action *
 MHDT_server_reply_check_upload (
   void *cls,
   struct MHD_Request *MHD_RESTRICT request,
   const struct MHD_String *MHD_RESTRICT path,
   enum MHD_HTTP_Method method,
   uint_fast64_t upload_size)
 {
   const char *want = cls;
   size_t wlen = strlen (want);
 
   (void) path; (void) method; (void) upload_size; /* Unused */
 
   return MHD_action_process_upload_full (request,
                                          wlen,
                                          &check_upload_cb,
                                          (void *) want);
 }
 
 
 /**
  * Closure for #chunk_return.
  */
 struct ChunkContext
 {
   /**
    * Where we are in the buffer.
    */
   const char *pos;
 };
 
 
 /**
  * Function that returns a string in chunks.
  *
  * @param dyn_cont_cls must be a `struct ChunkContext`
  * @param ctx the context to produce the action to return,
  *            the pointer is only valid until the callback returns
  * @param pos position in the datastream to access;
  *        note that if a `struct MHD_Response` object is re-used,
  *        it is possible for the same content reader to
  *        be queried multiple times for the same data;
  *        however, if a `struct MHD_Response` is not re-used,
  *        libmicrohttpd guarantees that "pos" will be
  *        the sum of all data sizes provided by this callback
  * @param[out] buf where to copy the data
  * @param max maximum number of bytes to copy to @a buf (size of @a buf)
  * @return action to use,
  *         NULL in case of any error (the response will be aborted)
  */
 static const struct MHD_DynamicContentCreatorAction *
 chunk_return (void *cls,
               struct MHD_DynamicContentCreatorContext *ctx,
               uint_fast64_t pos,
               void *buf,
               size_t max)
 {
   struct ChunkContext *cc = cls;
   size_t imax = strlen (cc->pos);
   const char *space = strchr (cc->pos, ' ');
 
   (void) pos; // TODO: add check
 
   if (0 == imax)
     return MHD_DCC_action_finish (ctx);
   if (NULL != space)
     imax = (size_t) (space - cc->pos) + 1;
   if (imax > max)
     imax = max;
   memcpy (buf,
           cc->pos,
           imax);
   cc->pos += imax;
   return MHD_DCC_action_continue (ctx,
                                   imax);
 }
 
 
 const struct MHD_Action *
 MHDT_server_reply_chunked_text (
   void *cls,
   struct MHD_Request *MHD_RESTRICT request,
   const struct MHD_String *MHD_RESTRICT path,
   enum MHD_HTTP_Method method,
   uint_fast64_t upload_size)
 {
   const char *text = cls;
   struct ChunkContext *cc;
 
   (void) path; (void) method; (void) upload_size; /* Unused */
 
   cc = malloc (sizeof (struct ChunkContext));
   if (NULL == cc)
     return NULL;
   cc->pos = text;
 
   return MHD_action_from_response (
     request,
     MHD_response_from_callback (MHD_HTTP_STATUS_OK,
                                 MHD_SIZE_UNKNOWN,
                                 &chunk_return,
                                 cc,
                                 &free));
 }
 
 
 /**
  * Compare two strings, succeed if both are NULL.
  *
  * @param wants string we want
  * @param have string we have
  * @return true if what we @a want is what we @a have
  */
 static bool
 nstrcmp (const char *wants,
          const struct MHD_StringNullable *have)
 {
   if ( (NULL == wants) &&
        (NULL == have->cstr) &&
        (0 == have->len) )
     return true;
   if ( (NULL == wants) ||
        (NULL == have->cstr) )
     return false;
   return (0 == strcmp (wants,
                        have->cstr));
 }
 
 
 /**
  * "Stream" reader for POST data.
  * This callback is called to incrementally process parsed POST data sent by
  * the client.
  *
  * @param req the request
  * @param cls user-specified closure
  * @param name the name of the POST field
  * @param filename the name of the uploaded file, @a cstr member is NULL if not
  *                 known / not provided
  * @param content_type the mime-type of the data, cstr member is NULL if not
  *                     known / not provided
  * @param encoding the encoding of the data, cstr member is NULL if not known /
  *                 not provided
  * @param size the number of bytes in @a data available, may be zero if
  *             the @a final_data is #MHD_YES
  * @param data the pointer to @a size bytes of data at the specified
  *             @a off offset, NOT zero-terminated
  * @param off the offset of @a data in the overall value, always equal to
  *            the sum of sizes of previous calls for the same field / file;
  *            client may provide more than one field with the same name and
  *            the same filename, the new filed (or file) is indicated by zero
  *            value of @a off (and the end is indicated by @a final_data)
  * @param final_data if set to #MHD_YES then full field data is provided,
  *                   if set to #MHD_NO then more field data may be provided
  * @return action specifying how to proceed:
  *         #MHD_upload_action_continue() if all is well,
  *         #MHD_upload_action_suspend() to stop reading the upload until
  *         the request is resumed,
  *         #MHD_upload_action_abort_request() to close the socket,
  *         or a response to discard the rest of the upload and transmit
  *         the response
  * @ingroup action
  */
 static const struct MHD_UploadAction *
 post_stream_reader (struct MHD_Request *req,
                     void *cls,
                     const struct MHD_String *name,
                     const struct MHD_StringNullable *filename,
                     const struct MHD_StringNullable *content_type,
                     const struct MHD_StringNullable *encoding,
                     size_t size,
                     const void *data,
                     uint_fast64_t off,
                     enum MHD_Bool final_data)
 {
   struct MHDT_PostInstructions *pi = cls;
   struct MHDT_PostWant *wants = pi->wants;
 
   (void) encoding; // TODO: add check
 
   if (NULL != wants)
   {
     for (unsigned int i = 0; NULL != wants[i].key; i++)
     {
       struct MHDT_PostWant *want = &wants[i];
 
       if (want->satisfied)
         continue;
       if (0 != strcmp (want->key,
                        name->cstr))
         continue;
       if (! nstrcmp (want->filename,
                      filename))
         continue;
       if (! nstrcmp (want->content_type,
                      content_type))
         continue;
       if (! want->incremental)
         continue;
       if (want->value_off != off)
         continue;
       if (want->value_size < off + size)
         continue;
       if (0 != memcmp (data,
                        want->value + off,
                        size))
         continue;
       want->value_off += size;
       want->satisfied = (want->value_size == want->value_off) && final_data;
     }
   }
 
   return MHD_upload_action_continue (req);
 }
 
 
 /**
  * Iterator over name-value pairs.  This iterator can be used to
  * iterate over all of the cookies, headers, or POST-data fields of a
  * request, and also to iterate over the headers that have been added
  * to a response.
  *
  * The pointers to the strings in @a nvt are valid until the response
  * is queued. If the data is needed beyond this point, it should be copied.
  *
  * @param cls closure
  * @param nvt the name, the value and the kind of the element
  * @return #MHD_YES to continue iterating,
  *         #MHD_NO to abort the iteration
  * @ingroup request
  */
 static enum MHD_Bool
 check_complete_post_value (
   void *cls,
   enum MHD_ValueKind kind,
   const struct MHD_NameAndValue *nv)
 {
   struct MHDT_PostInstructions *pi = cls;
   struct MHDT_PostWant *wants = pi->wants;
 
   if (NULL == wants)
     return MHD_NO;
   if (MHD_VK_POSTDATA != kind)
     return MHD_NO;
   for (unsigned int i = 0; NULL != wants[i].key; i++)
   {
     struct MHDT_PostWant *want = &wants[i];
 
     if (want->satisfied)
       continue;
     if (want->incremental)
       continue;
     if (0 != strcmp (want->key,
                      nv->name.cstr))
       continue;
     if (NULL == want->value)
     {
       if (NULL == nv->value.cstr)
         want->satisfied = true;
     }
     else if (NULL == nv->value.cstr)
       continue;
     else if (0 == want->value_size)
     {
       if (0 == strcmp (nv->value.cstr,
                        want->value))
         want->satisfied = true;
     }
     else
     {
       if ((want->value_size == nv->value.len) &&
           (0 == memcmp (nv->value.cstr,
                         want->value,
                         want->value_size)))
         want->satisfied = true;
     }
   }
   return MHD_YES;
 }
 
 
 /**
  * The callback to be called when finished with processing
  * of the postprocessor upload data.
  * @param req the request
  * @param cls the closure
  * @param parsing_result the result of POST data parsing
  * @return the action to proceed
  */
 static const struct MHD_UploadAction *
 post_stream_done (struct MHD_Request *req,
                   void *cls,
                   enum MHD_PostParseResult parsing_result)
 {
   struct MHDT_PostInstructions *pi = cls;
   struct MHDT_PostWant *wants = pi->wants;
 
   if (MHD_POST_PARSE_RES_OK != parsing_result)
   {
     fprintf (stderr,
              "POST parsing was not successful. The result: %d\n",
              (int) parsing_result);
     return MHD_upload_action_abort_request (req);
   }
 
   MHD_request_get_values_cb (req,
                              MHD_VK_POSTDATA,
                              &check_complete_post_value,
                              pi);
   if (NULL != wants)
   {
     for (unsigned int i = 0; NULL != wants[i].key; i++)
     {
       struct MHDT_PostWant *want = &wants[i];
 
       if (want->satisfied)
         continue;
       fprintf (stderr,
                "Expected key-value pair `%s' missing\n",
                want->key);
       return MHD_upload_action_abort_request (req);
     }
   }
   return MHD_upload_action_from_response (
     req,
     MHD_response_from_empty (
       MHD_HTTP_STATUS_NO_CONTENT));
 }
 
 
 const struct MHD_Action *
 MHDT_server_reply_check_post (
   void *cls,
   struct MHD_Request *MHD_RESTRICT request,
   const struct MHD_String *MHD_RESTRICT path,
   enum MHD_HTTP_Method method,
   uint_fast64_t upload_size)
 {
   struct MHDT_PostInstructions *pi = cls;
 
   (void) path; /* Unused */
   (void) upload_size; // TODO: add check
 
   if (MHD_HTTP_METHOD_POST != method)
   {
     fprintf (stderr,
              "Reported HTTP method other then POST. Reported method: %u\n",
              (unsigned) method);
     return MHD_action_abort_request (req);
   }
 
   return MHD_action_parse_post (request,
                                 pi->buffer_size,
                                 pi->auto_stream_size,
                                 pi->enc,
                                 &post_stream_reader,
                                 pi,
                                 &post_stream_done,
                                 pi);
 }
 
 
 const struct MHD_Action *
 MHDT_server_reply_check_basic_auth (
   void *cls,
   struct MHD_Request *MHD_RESTRICT request,
   const struct MHD_String *MHD_RESTRICT path,
   enum MHD_HTTP_Method method,
   uint_fast64_t upload_size)
 {
   const char *cred = cls;
   union MHD_RequestInfoDynamicData dd;
   enum MHD_StatusCode sc;
   const struct MHD_AuthBasicCreds *ba;
 
   /* should not be needed, except to make gcc happy */
   memset (&dd,
           0,
           sizeof (dd));
   sc = MHD_request_get_info_dynamic (request,
                                      MHD_REQUEST_INFO_DYNAMIC_AUTH_BASIC_CREDS,
                                      &dd);
   if (MHD_SC_OK != sc)
   {
     fprintf (stderr,
              "No credentials?\n");
     return MHD_action_basic_auth_challenge_p (
       request,
       "test-realm",
       MHD_YES,
       MHD_response_from_empty (
         MHD_HTTP_STATUS_UNAUTHORIZED));
   }
   ba = dd.v_auth_basic_creds;
   assert (NULL != ba);
   if ( (0 != strncmp (ba->username.cstr,
                       cred,
                       ba->username.len)) ||
        (':' != cred[ba->username.len]) ||
        (NULL == ba->password.cstr) ||
        (0 != strcmp (ba->password.cstr,
                      &cred[ba->username.len + 1])) )
   {
     fprintf (stderr,
              "Wrong credentials (Got: %s/%s Want: %s)!\n",
              ba->username.cstr,
              ba->password.cstr,
              cred);
     return MHD_action_basic_auth_challenge_p (
       request,
       "test-realm",
       MHD_YES,
       MHD_response_from_empty (
         MHD_HTTP_STATUS_UNAUTHORIZED));
   }
   return MHD_action_from_response (
     request,
     MHD_response_from_empty (
       MHD_HTTP_STATUS_NO_CONTENT));
 }
 
 
 const struct MHD_Action *
 MHDT_server_reply_check_digest_auth (
   void *cls,
   struct MHD_Request *MHD_RESTRICT request,
   const struct MHD_String *MHD_RESTRICT path,
   enum MHD_HTTP_Method method,
   uint_fast64_t upload_size)
 {
   const char *cred = cls;
   const char *colon = strchr (cred, ':');
   char *username;
   const char *password;
   enum MHD_DigestAuthResult dar;
   const char *realm = "test-realm";
 #if CURL_AT_LEAST_VERSION (7,57,0)
   enum MHD_DigestAuthAlgo algo = MHD_DIGEST_AUTH_ALGO_SHA256;
 #else
   enum MHD_DigestAuthAlgo algo = MHD_DIGEST_AUTH_ALGO_MD5;
 #endif
   size_t digest_len = MHD_digest_get_hash_size (algo);
 
   (void) cls; /* Unused, mute compiler warning */
 
   if (0 == digest_len)
     return NULL;
   assert (NULL != colon);
   password = colon + 1;
   username = strndup (cred,
                       colon - cred);
   assert (NULL != username);
   {
     enum MHD_StatusCode sc;
     char digest[digest_len];
 
     // FIXME: why is this needed? We should not get a warning
     // even without this memset!
     memset (digest, 0, sizeof (digest));
     sc = MHD_digest_auth_calc_userdigest (algo,
                                           username,
                                           realm,
                                           password,
                                           sizeof (digest),
                                           digest);
     if (MHD_SC_OK != sc)
     {
       fprintf (stderr,
                "MHD_digest_auth_calc_userdigest: %d\n",
                (int) sc);
       free (username);
       return NULL;
     }
     dar = MHD_digest_auth_check_digest (request,
                                         realm,
                                         username,
                                         sizeof (digest),
                                         digest,
                                         0, /* maximum nonce counter; 0: default */
                                         MHD_DIGEST_AUTH_MULT_QOP_AUTH,
                                         (enum MHD_DigestAuthMultiAlgo) algo);
   }
   free (username);
   if ((MHD_DAUTH_HEADER_MISSING == dar)
       || (MHD_DAUTH_NONCE_STALE == dar))
   {
     struct MHD_Response *resp;
     enum MHD_StatusCode sc;
 
     resp = MHD_response_from_empty (
       MHD_HTTP_STATUS_UNAUTHORIZED);
     if (NULL == resp)
     {
       fprintf (stderr,
                "Failed to create response body\n");
       return NULL;
     }
     sc = MHD_response_add_auth_digest_challenge (
       resp,
       "test-realm",
       "opaque",
       NULL, /* domain */
       (MHD_DAUTH_NONCE_STALE == dar) ? MHD_YES : MHD_NO, /* indicate stale */
       MHD_DIGEST_AUTH_MULT_QOP_AUTH,
       (enum MHD_DigestAuthMultiAlgo) algo,
       MHD_NO /* userhash_support */,
       MHD_YES /* prefer UTF8 */);
     if (MHD_SC_OK != sc)
     {
       fprintf (stderr,
                "MHD_response_add_auth_digest_challenge failed: %d\n",
                (int) sc);
       return NULL;
     }
     return MHD_action_from_response (
       request,
       resp);
   }
   if (MHD_DAUTH_RESPONSE_WRONG == dar)
     return MHD_action_from_response (
       request,
       MHD_response_from_empty (MHD_HTTP_STATUS_FORBIDDEN));
 
   if (MHD_DAUTH_OK == dar)
     return MHD_action_from_response (
       request,
       MHD_response_from_empty (
         MHD_HTTP_STATUS_NO_CONTENT));
 
   return MHD_action_abort_request (request);
 }