Add CMAC (Cipher-based MAC) to MAC API

* cipher/Makefile.am: Add 'cipher-cmac.c' and 'mac-cmac.c'.
* cipher/cipher-cmac.c: New.
* cipher/cipher-internal.h (gcry_cipher_handle.u_mode): Add 'cmac'.
* cipher/cipher.c (gcry_cipher_open): Rename to...
(_gcry_cipher_open_internal): ...this and add CMAC.
(gcry_cipher_open): New wrapper that disallows use of internal
modes (CMAC) from outside.
(cipher_setkey, cipher_encrypt, cipher_decrypt)
(_gcry_cipher_authenticate, _gcry_cipher_gettag)
(_gcry_cipher_checktag): Add handling for CMAC mode.
(cipher_reset): Do not reset 'marks.key' and do not clear subkeys in
'u_mode' in CMAC mode.
* cipher/mac-cmac.c: New.
* cipher/mac-internal.h: Add CMAC support and algorithms.
* cipher/mac.c: Add CMAC algorithms.
* doc/gcrypt.texi: Add documentation for CMAC.
* src/cipher.h (gcry_cipher_internal_modes): New.
(_gcry_cipher_open_internal, _gcry_cipher_cmac_authenticate)
(_gcry_cipher_cmac_get_tag, _gcry_cipher_cmac_check_tag)
(_gcry_cipher_cmac_set_subkeys): New prototypes.
* src/gcrypt.h.in (gcry_mac_algos): Add CMAC algorithms.
* tests/basic.c (check_mac): Add CMAC test vectors.
--

Patch adds CMAC (Cipher-based MAC) as defined in RFC 4493 and NIST
Special Publication 800-38B.

Internally CMAC is added to cipher module, but is available to outside
only through MAC API.

[v2]:
 - Add documentation.
[v3]:
 - CMAC algorithm ids start from 201.
 - Coding style fixes.

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

1 files changed, 67 insertions, 1 deletions

diff --git a/cipher/cipher.c b/cipher/cipher.c
index 80aa7a74..b68703e3 100644
--- a/cipher/cipher.c
+++ b/cipher/cipher.c
@@ -344,6 +344,24 @@ gcry_error_t
 gcry_cipher_open (gcry_cipher_hd_t *handle,
 		  int algo, int mode, unsigned int flags)
 {
+  gcry_err_code_t err;
+  gcry_cipher_hd_t h = NULL;
+
+  if (mode >= GCRY_CIPHER_MODE_INTERNAL)
+    err = GPG_ERR_INV_CIPHER_MODE;
+  else
+    err = _gcry_cipher_open_internal (&h, algo, mode, flags);
+
+  *handle = err ? NULL : h;
+
+  return gcry_error (err);
+}
+
+
+gcry_err_code_t
+_gcry_cipher_open_internal (gcry_cipher_hd_t *handle,
+			    int algo, int mode, unsigned int flags)
+{
   int secure = (flags & GCRY_CIPHER_SECURE);
   gcry_cipher_spec_t *spec;
   gcry_cipher_hd_t h = NULL;
@@ -388,6 +406,7 @@ gcry_cipher_open (gcry_cipher_hd_t *handle,
       case GCRY_CIPHER_MODE_OFB:
       case GCRY_CIPHER_MODE_CTR:
       case GCRY_CIPHER_MODE_AESWRAP:
+      case GCRY_CIPHER_MODE_CMAC:
 	if (!spec->encrypt || !spec->decrypt)
 	  err = GPG_ERR_INV_CIPHER_MODE;
 	break;
@@ -567,10 +586,20 @@ cipher_setkey (gcry_cipher_hd_t c, byte *key, size_t keylen)
               (void *) &c->context.c,
               c->spec->contextsize);
       c->marks.key = 1;
+
+      switch (c->mode)
+        {
+        case GCRY_CIPHER_MODE_CMAC:
+          _gcry_cipher_cmac_set_subkeys (c);
+          break;
+        default:
+          break;
+        };
     }
   else
     c->marks.key = 0;
 
+
   return gcry_error (ret);
 }
 
@@ -613,6 +642,10 @@ cipher_setiv (gcry_cipher_hd_t c, const byte *iv, size_t ivlen)
 static void
 cipher_reset (gcry_cipher_hd_t c)
 {
+  unsigned int marks_key;
+
+  marks_key = c->marks.key;
+
   memcpy (&c->context.c,
 	  (char *) &c->context.c + c->spec->contextsize,
 	  c->spec->contextsize);
@@ -620,8 +653,21 @@ cipher_reset (gcry_cipher_hd_t c)
   memset (c->u_iv.iv, 0, c->spec->blocksize);
   memset (c->lastiv, 0, c->spec->blocksize);
   memset (c->u_ctr.ctr, 0, c->spec->blocksize);
-  memset (&c->u_mode, 0, sizeof c->u_mode);
   c->unused = 0;
+
+  c->marks.key = marks_key;
+
+  switch (c->mode)
+    {
+    case GCRY_CIPHER_MODE_CMAC:
+      /* Only clear 'tag' for cmac, keep subkeys. */
+      c->u_mode.cmac.tag = 0;
+      break;
+
+    default:
+      memset (&c->u_mode, 0, sizeof c->u_mode);
+      break;
+    }
 }
 
 
@@ -717,6 +763,10 @@ cipher_encrypt (gcry_cipher_hd_t c, byte *outbuf, size_t outbuflen,
       rc = _gcry_cipher_ccm_encrypt (c, outbuf, outbuflen, inbuf, inbuflen);
       break;
 
+    case GCRY_CIPHER_MODE_CMAC:
+      rc = GPG_ERR_INV_CIPHER_MODE;
+      break;
+
     case GCRY_CIPHER_MODE_STREAM:
       c->spec->stencrypt (&c->context.c,
                           outbuf, (byte*)/*arggg*/inbuf, inbuflen);
@@ -817,6 +867,10 @@ cipher_decrypt (gcry_cipher_hd_t c, byte *outbuf, size_t outbuflen,
       rc = _gcry_cipher_ccm_decrypt (c, outbuf, outbuflen, inbuf, inbuflen);
       break;
 
+    case GCRY_CIPHER_MODE_CMAC:
+      rc = GPG_ERR_INV_CIPHER_MODE;
+      break;
+
     case GCRY_CIPHER_MODE_STREAM:
       c->spec->stdecrypt (&c->context.c,
                           outbuf, (byte*)/*arggg*/inbuf, inbuflen);
@@ -942,6 +996,10 @@ _gcry_cipher_authenticate (gcry_cipher_hd_t hd, const void *abuf,
       rc = _gcry_cipher_ccm_authenticate (hd, abuf, abuflen);
       break;
 
+    case GCRY_CIPHER_MODE_CMAC:
+      rc = _gcry_cipher_cmac_authenticate (hd, abuf, abuflen);
+      break;
+
     default:
       log_error ("gcry_cipher_authenticate: invalid mode %d\n", hd->mode);
       rc = GPG_ERR_INV_CIPHER_MODE;
@@ -962,6 +1020,10 @@ _gcry_cipher_gettag (gcry_cipher_hd_t hd, void *outtag, size_t taglen)
       rc = _gcry_cipher_ccm_get_tag (hd, outtag, taglen);
       break;
 
+    case GCRY_CIPHER_MODE_CMAC:
+      rc = _gcry_cipher_cmac_get_tag (hd, outtag, taglen);
+      break;
+
     default:
       log_error ("gcry_cipher_gettag: invalid mode %d\n", hd->mode);
       rc = GPG_ERR_INV_CIPHER_MODE;
@@ -982,6 +1044,10 @@ _gcry_cipher_checktag (gcry_cipher_hd_t hd, const void *intag, size_t taglen)
       rc = _gcry_cipher_ccm_check_tag (hd, intag, taglen);
       break;
 
+    case GCRY_CIPHER_MODE_CMAC:
+      rc = _gcry_cipher_cmac_check_tag (hd, intag, taglen);
+      break;
+
     default:
       log_error ("gcry_cipher_checktag: invalid mode %d\n", hd->mode);
       rc = GPG_ERR_INV_CIPHER_MODE;