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, 47 insertions, 1 deletions

diff --git a/cipher/cipher-internal.h b/cipher/cipher-internal.h
index b60ef386..981caa83 100644
--- a/cipher/cipher-internal.h
+++ b/cipher/cipher-internal.h
@@ -100,7 +100,8 @@ struct gcry_cipher_handle
 
   /* The initialization vector.  For best performance we make sure
      that it is properly aligned.  In particular some implementations
-     of bulk operations expect an 16 byte aligned IV.  */
+     of bulk operations expect an 16 byte aligned IV.  IV is also used
+     to store CBC-MAC in CCM mode; counter IV is stored in U_CTR.  */
   union {
     cipher_context_alignment_t iv_align;
     unsigned char iv[MAX_BLOCKSIZE];
@@ -117,6 +118,26 @@ struct gcry_cipher_handle
   unsigned char lastiv[MAX_BLOCKSIZE];
   int unused;  /* Number of unused bytes in LASTIV. */
 
+  union {
+    /* Mode specific storage for CCM mode. */
+    struct {
+      size_t encryptlen;
+      size_t aadlen;
+      unsigned int authlen;
+
+      /* Space to save partial input lengths for MAC. */
+      unsigned char macbuf[GCRY_CCM_BLOCK_LEN];
+      int mac_unused;  /* Number of unprocessed bytes in MACBUF. */
+
+      unsigned char s0[GCRY_CCM_BLOCK_LEN];
+
+      unsigned int nonce:1;/* Set to 1 if nonce has been set.  */
+      unsigned int lengths:1; /* Set to 1 if CCM length parameters has been
+                                 processed.  */
+      unsigned int tag:1; /* Set to 1 if tag has been finalized.  */
+    } ccm;
+  } u_mode;
+
   /* What follows are two contexts of the cipher in use.  The first
      one needs to be aligned well enough for the cipher operation
      whereas the second one is a copy created by cipher_setkey and
@@ -175,5 +196,30 @@ gcry_err_code_t _gcry_cipher_aeswrap_decrypt
                    const byte *inbuf, unsigned int inbuflen);
 
 
+/*-- cipher-ccm.c --*/
+gcry_err_code_t _gcry_cipher_ccm_encrypt
+/*           */ (gcry_cipher_hd_t c,
+                 unsigned char *outbuf, unsigned int outbuflen,
+                 const unsigned char *inbuf, unsigned int inbuflen);
+gcry_err_code_t _gcry_cipher_ccm_decrypt
+/*           */ (gcry_cipher_hd_t c,
+                 unsigned char *outbuf, unsigned int outbuflen,
+                 const unsigned char *inbuf, unsigned int inbuflen);
+gcry_err_code_t _gcry_cipher_ccm_set_nonce
+/*           */ (gcry_cipher_hd_t c, const unsigned char *nonce,
+                 size_t noncelen);
+gcry_err_code_t _gcry_cipher_ccm_authenticate
+/*           */ (gcry_cipher_hd_t c, const unsigned char *abuf, size_t abuflen);
+gcry_err_code_t _gcry_cipher_ccm_set_lengths
+/*           */ (gcry_cipher_hd_t c, size_t encryptedlen, size_t aadlen,
+                 size_t taglen);
+gcry_err_code_t _gcry_cipher_ccm_get_tag
+/*           */ (gcry_cipher_hd_t c,
+                 unsigned char *outtag, size_t taglen);
+gcry_err_code_t _gcry_cipher_ccm_check_tag
+/*           */ (gcry_cipher_hd_t c,
+                 const unsigned char *intag, size_t taglen);
+
+
 
 #endif /*G10_CIPHER_INTERNAL_H*/