1 files changed, 254 insertions, 0 deletions

diff --git a/src/lib/util/crypto_symmetric.c b/src/lib/util/crypto_symmetric.c
new file mode 100644
index 000000000..c08b84c17
--- /dev/null
+++ b/src/lib/util/crypto_symmetric.c
@@ -0,0 +1,254 @@
+/*
+     This file is part of GNUnet.
+     Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2013 GNUnet e.V.
+
+     GNUnet is free software: you can redistribute it and/or modify it
+     under the terms of the GNU Affero General Public License as published
+     by the Free Software Foundation, either version 3 of the License,
+     or (at your option) any later version.
+
+     GNUnet 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
+     Affero General Public License for more details.
+
+     You should have received a copy of the GNU Affero General Public License
+     along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+     SPDX-License-Identifier: AGPL3.0-or-later
+ */
+
+/**
+ * @file util/crypto_symmetric.c
+ * @brief Symmetric encryption services; combined cipher AES+TWOFISH (256-bit each)
+ * @author Christian Grothoff
+ * @author Ioana Patrascu
+ */
+
+
+#include "platform.h"
+#include "gnunet_util_lib.h"
+#include <gcrypt.h>
+
+#define LOG(kind, ...) GNUNET_log_from (kind, "util-crypto-symmetric", \
+                                        __VA_ARGS__)
+
+/**
+ * Create a new SessionKey (for symmetric encryption).
+ *
+ * @param key session key to initialize
+ */
+void
+GNUNET_CRYPTO_symmetric_create_session_key (struct
+                                            GNUNET_CRYPTO_SymmetricSessionKey *
+                                            key)
+{
+  gcry_randomize (key->aes_key,
+                  GNUNET_CRYPTO_AES_KEY_LENGTH,
+                  GCRY_STRONG_RANDOM);
+  gcry_randomize (key->twofish_key,
+                  GNUNET_CRYPTO_AES_KEY_LENGTH,
+                  GCRY_STRONG_RANDOM);
+}
+
+
+/**
+ * Initialize AES cipher.
+ *
+ * @param handle handle to initialize
+ * @param sessionkey session key to use
+ * @param iv initialization vector to use
+ * @return #GNUNET_OK on success, #GNUNET_SYSERR on error
+ */
+static int
+setup_cipher_aes (gcry_cipher_hd_t *handle,
+                  const struct GNUNET_CRYPTO_SymmetricSessionKey *sessionkey,
+                  const struct GNUNET_CRYPTO_SymmetricInitializationVector *iv)
+{
+  int rc;
+
+  GNUNET_assert (0 ==
+                 gcry_cipher_open (handle, GCRY_CIPHER_AES256,
+                                   GCRY_CIPHER_MODE_CFB, 0));
+  rc = gcry_cipher_setkey (*handle,
+                           sessionkey->aes_key,
+                           sizeof(sessionkey->aes_key));
+  GNUNET_assert ((0 == rc) || ((char) rc == GPG_ERR_WEAK_KEY));
+  rc = gcry_cipher_setiv (*handle,
+                          iv->aes_iv,
+                          sizeof(iv->aes_iv));
+  GNUNET_assert ((0 == rc) || ((char) rc == GPG_ERR_WEAK_KEY));
+  return GNUNET_OK;
+}
+
+
+/**
+ * Initialize TWOFISH cipher.
+ *
+ * @param handle handle to initialize
+ * @param sessionkey session key to use
+ * @param iv initialization vector to use
+ * @return #GNUNET_OK on success, #GNUNET_SYSERR on error
+ */
+static int
+setup_cipher_twofish (gcry_cipher_hd_t *handle,
+                      const struct
+                      GNUNET_CRYPTO_SymmetricSessionKey *sessionkey,
+                      const struct
+                      GNUNET_CRYPTO_SymmetricInitializationVector *iv)
+{
+  int rc;
+
+  GNUNET_assert (0 ==
+                 gcry_cipher_open (handle, GCRY_CIPHER_TWOFISH,
+                                   GCRY_CIPHER_MODE_CFB, 0));
+  rc = gcry_cipher_setkey (*handle,
+                           sessionkey->twofish_key,
+                           sizeof(sessionkey->twofish_key));
+  GNUNET_assert ((0 == rc) || ((char) rc == GPG_ERR_WEAK_KEY));
+  rc = gcry_cipher_setiv (*handle,
+                          iv->twofish_iv,
+                          sizeof(iv->twofish_iv));
+  GNUNET_assert ((0 == rc) || ((char) rc == GPG_ERR_WEAK_KEY));
+  return GNUNET_OK;
+}
+
+
+/**
+ * Encrypt a block with a symmetric session key.
+ *
+ * @param block the block to encrypt
+ * @param size the size of the @a block
+ * @param sessionkey the key used to encrypt
+ * @param iv the initialization vector to use, use INITVALUE for streams
+ * @param result the output parameter in which to store the encrypted result
+ *               can be the same or overlap with @c block
+ * @returns the size of the encrypted block, -1 for errors.
+ *          Due to the use of CFB and therefore an effective stream cipher,
+ *          this size should be the same as @c len.
+ */
+ssize_t
+GNUNET_CRYPTO_symmetric_encrypt (const void *block,
+                                 size_t size,
+                                 const struct
+                                 GNUNET_CRYPTO_SymmetricSessionKey *sessionkey,
+                                 const struct
+                                 GNUNET_CRYPTO_SymmetricInitializationVector *iv,
+                                 void *result)
+{
+  gcry_cipher_hd_t handle;
+  char tmp[GNUNET_NZL(size)];
+
+  if (GNUNET_OK != setup_cipher_aes (&handle, sessionkey, iv))
+    return -1;
+  GNUNET_assert (0 == gcry_cipher_encrypt (handle, tmp, size, block, size));
+  gcry_cipher_close (handle);
+  if (GNUNET_OK != setup_cipher_twofish (&handle, sessionkey, iv))
+    return -1;
+  GNUNET_assert (0 == gcry_cipher_encrypt (handle, result, size, tmp, size));
+  gcry_cipher_close (handle);
+  memset (tmp, 0, sizeof(tmp));
+  return size;
+}
+
+
+/**
+ * Decrypt a given block with the session key.
+ *
+ * @param block the data to decrypt, encoded as returned by encrypt
+ * @param size the size of the @a block to decrypt
+ * @param sessionkey the key used to decrypt
+ * @param iv the initialization vector to use, use INITVALUE for streams
+ * @param result address to store the result at
+ *               can be the same or overlap with @c block
+ * @return -1 on failure, size of decrypted block on success.
+ *         Due to the use of CFB and therefore an effective stream cipher,
+ *         this size should be the same as @c size.
+ */
+ssize_t
+GNUNET_CRYPTO_symmetric_decrypt (const void *block,
+                                 size_t size,
+                                 const struct
+                                 GNUNET_CRYPTO_SymmetricSessionKey *sessionkey,
+                                 const struct
+                                 GNUNET_CRYPTO_SymmetricInitializationVector *iv,
+                                 void *result)
+{
+  gcry_cipher_hd_t handle;
+  char tmp[size];
+
+  if (GNUNET_OK != setup_cipher_twofish (&handle, sessionkey, iv))
+    return -1;
+  GNUNET_assert (0 == gcry_cipher_decrypt (handle, tmp, size, block, size));
+  gcry_cipher_close (handle);
+  if (GNUNET_OK != setup_cipher_aes (&handle, sessionkey, iv))
+    return -1;
+  GNUNET_assert (0 == gcry_cipher_decrypt (handle, result, size, tmp, size));
+  gcry_cipher_close (handle);
+  memset (tmp, 0, sizeof(tmp));
+  return size;
+}
+
+
+/**
+ * @brief Derive an IV
+ *
+ * @param iv initialization vector
+ * @param skey session key
+ * @param salt salt for the derivation
+ * @param salt_len size of the @a salt
+ * @param ... pairs of void * & size_t for context chunks, terminated by NULL
+ */
+void
+GNUNET_CRYPTO_symmetric_derive_iv (struct
+                                   GNUNET_CRYPTO_SymmetricInitializationVector *
+                                   iv,
+                                   const struct
+                                   GNUNET_CRYPTO_SymmetricSessionKey *skey,
+                                   const void *salt,
+                                   size_t salt_len,
+                                   ...)
+{
+  va_list argp;
+
+  va_start (argp, salt_len);
+  GNUNET_CRYPTO_symmetric_derive_iv_v (iv, skey, salt, salt_len, argp);
+  va_end (argp);
+}
+
+
+void
+GNUNET_CRYPTO_symmetric_derive_iv_v (struct
+                                     GNUNET_CRYPTO_SymmetricInitializationVector
+                                     *iv,
+                                     const struct
+                                     GNUNET_CRYPTO_SymmetricSessionKey *skey,
+                                     const void *salt,
+                                     size_t salt_len,
+                                     va_list argp)
+{
+  char aes_salt[salt_len + 4];
+  char twofish_salt[salt_len + 4];
+
+  GNUNET_memcpy (aes_salt, salt, salt_len);
+  GNUNET_memcpy (&aes_salt[salt_len], "AES!", 4);
+  GNUNET_memcpy (twofish_salt, salt, salt_len);
+  GNUNET_memcpy (&twofish_salt[salt_len], "FISH", 4);
+  GNUNET_CRYPTO_kdf_v (iv->aes_iv,
+                       sizeof(iv->aes_iv),
+                       aes_salt,
+                       salt_len + 4,
+                       skey->aes_key,
+                       sizeof(skey->aes_key),
+                       argp);
+  GNUNET_CRYPTO_kdf_v (iv->twofish_iv,
+                       sizeof(iv->twofish_iv),
+                       twofish_salt,
+                       salt_len + 4,
+                       skey->twofish_key,
+                       sizeof(skey->twofish_key),
+                       argp);
+}
+
+
+/* end of crypto_symmetric.c */