Add Counter with CBC-MAC mode (CCM)

* cipher/Makefile.am: Add 'cipher-ccm.c'.
* cipher/cipher-ccm.c: New.
* cipher/cipher-internal.h (gcry_cipher_handle): Add 'u_mode'.
(_gcry_cipher_ccm_encrypt, _gcry_cipher_ccm_decrypt)
(_gcry_cipher_ccm_set_nonce, _gcry_cipher_ccm_authenticate)
(_gcry_cipher_ccm_get_tag, _gcry_cipher_ccm_check_tag)
(_gcry_cipher_ccm_set_lengths): New prototypes.
* cipher/cipher.c (gcry_cipher_open, cipher_encrypt, cipher_decrypt)
(_gcry_cipher_setiv, _gcry_cipher_authenticate, _gcry_cipher_gettag)
(_gcry_cipher_checktag, gry_cipher_ctl): Add handling for CCM mode.
* doc/gcrypt.texi: Add documentation for GCRY_CIPHER_MODE_CCM.
* src/gcrypt.h.in (gcry_cipher_modes): Add 'GCRY_CIPHER_MODE_CCM'.
(gcry_ctl_cmds): Add 'GCRYCTL_SET_CCM_LENGTHS'.
(GCRY_CCM_BLOCK_LEN): New.
* tests/basic.c (check_ccm_cipher): New.
(check_cipher_modes): Call 'check_ccm_cipher'.
* tests/benchmark.c (ccm_aead_init): New.
(cipher_bench): Add handling for AEAD modes and add CCM benchmarking.
--

Patch adds CCM (Counter with CBC-MAC) mode as defined in RFC 3610 and NIST
Special Publication 800-38C.

Example for encrypting message (split in two buffers; buf1, buf2) and
authenticating additional non-encrypted data (split in two buffers; aadbuf1,
aadbuf2) with authentication tag length of eigth bytes:

  size_t params[3];
  taglen = 8;

  gcry_cipher_setkey(h, key, len(key));

  gcry_cipher_setiv(h, nonce, len(nonce));

  params[0] = len(buf1) + len(buf2);       /* 0: enclen */
  params[1] = len(aadbuf1) + len(aadbuf2); /* 1: aadlen */
  params[2] = taglen;                      /* 2: authtaglen */
  gcry_cipher_ctl(h, GCRYCTL_SET_CCM_LENGTHS, params, sizeof(size_t) * 3);

  gcry_cipher_authenticate(h, aadbuf1, len(aadbuf1));
  gcry_cipher_authenticate(h, aadbuf2, len(aadbuf2));

  gcry_cipher_encrypt(h, buf1, len(buf1), buf1, len(buf1));
  gcry_cipher_encrypt(h, buf2, len(buf2), buf2, len(buf2));

  gcry_cipher_gettag(h, tag, taglen);

Example for decrypting above message and checking authentication tag:

  size_t params[3];
  taglen = 8;

  gcry_cipher_setkey(h, key, len(key));

  gcry_cipher_setiv(h, nonce, len(nonce));

  params[0] = len(buf1) + len(buf2);       /* 0: enclen */
  params[1] = len(aadbuf1) + len(aadbuf2); /* 1: aadlen */
  params[2] = taglen;                      /* 2: authtaglen */
  gcry_cipher_ctl(h, GCRYCTL_SET_CCM_LENGTHS, params, sizeof(size_t) * 3);

  gcry_cipher_authenticate(h, aadbuf1, len(aadbuf1));
  gcry_cipher_authenticate(h, aadbuf2, len(aadbuf2));

  gcry_cipher_decrypt(h, buf1, len(buf1), buf1, len(buf1));
  gcry_cipher_decrypt(h, buf2, len(buf2), buf2, len(buf2));

  err = gcry_cipher_checktag(h, tag, taglen);
  if (gpg_err_code (err) == GPG_ERR_CHECKSUM)
    { /* Authentication failed. */ }
  else if (err == 0)
    { /* Authentication ok. */ }

Example for encrypting message without additional authenticated data:

  size_t params[3];
  taglen = 10;

  gcry_cipher_setkey(h, key, len(key));

  gcry_cipher_setiv(h, nonce, len(nonce));

  params[0] = len(buf1); /* 0: enclen */
  params[1] = 0;         /* 1: aadlen */
  params[2] = taglen;    /* 2: authtaglen */
  gcry_cipher_ctl(h, GCRYCTL_SET_CCM_LENGTHS, params, sizeof(size_t) * 3);

  gcry_cipher_encrypt(h, buf1, len(buf1), buf1, len(buf1));

  gcry_cipher_gettag(h, tag, taglen);

To reset CCM state for cipher handle, one can either set new nonce or use
'gcry_cipher_reset'.

This implementation reuses existing CTR mode code for encryption/decryption
and is there for able to process multiple buffers that are not multiple of
blocksize. AAD data maybe also be passed into gcry_cipher_authenticate
in non-blocksize chunks.

[v4]: GCRYCTL_SET_CCM_PARAMS => GCRY_SET_CCM_LENGTHS

Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>

1 files changed, 12 insertions, 4 deletions

diff --git a/doc/gcrypt.texi b/doc/gcrypt.texi
index 0049fa04..91fe399c 100644
--- a/doc/gcrypt.texi
+++ b/doc/gcrypt.texi
@@ -1635,6 +1635,12 @@ may be specified 64 bit (8 byte) shorter than then input buffer.  As
 per specs the input length must be at least 128 bits and the length
 must be a multiple of 64 bits.
 
+@item  GCRY_CIPHER_MODE_CCM
+@cindex CCM, Counter with CBC-MAC mode
+Counter with CBC-MAC mode is an Authenticated Encryption with
+Associated Data (AEAD) block cipher mode, which is specified in
+'NIST Special Publication 800-38C' and RFC 3610.
+
 @end table
 
 @node Working with cipher handles
@@ -1661,11 +1667,13 @@ The cipher mode to use must be specified via @var{mode}.  See
 @xref{Available cipher modes}, for a list of supported cipher modes
 and the according constants.  Note that some modes are incompatible
 with some algorithms - in particular, stream mode
-(@code{GCRY_CIPHER_MODE_STREAM}) only works with stream ciphers. Any
-block cipher mode (@code{GCRY_CIPHER_MODE_ECB},
+(@code{GCRY_CIPHER_MODE_STREAM}) only works with stream ciphers. The
+block cipher modes (@code{GCRY_CIPHER_MODE_ECB},
 @code{GCRY_CIPHER_MODE_CBC}, @code{GCRY_CIPHER_MODE_CFB},
-@code{GCRY_CIPHER_MODE_OFB} or @code{GCRY_CIPHER_MODE_CTR}) will work
-with any block cipher algorithm.
+@code{GCRY_CIPHER_MODE_OFB} and @code{GCRY_CIPHER_MODE_CTR}) will work
+with any block cipher algorithm. The @code{GCRY_CIPHER_MODE_CCM} will
+only work with block cipher algorithms which have the block size of
+16 bytes.
 
 The third argument @var{flags} can either be passed as @code{0} or as
 the bit-wise OR of the following constants.