Factor cipher mode code out to separate files.

This is a preparation for adding more modes which are more complicated
and thus ask for separate file.  For uniformity we do this for all
modes except ECB.  It has also the advantage that it makes CPU specific
variants of the code more easy to implement (e.g. the XOR operations).

1 files changed, 187 insertions, 0 deletions

diff --git a/cipher/cipher-cbc.c b/cipher/cipher-cbc.c
new file mode 100644
index 00000000..b8525898
--- /dev/null
+++ b/cipher/cipher-cbc.c
@@ -0,0 +1,187 @@
+/* cipher-cbc.c  - Generic CBC mode implementation
+ * Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003
+ *               2005, 2007, 2008, 2009, 2011 Free Software Foundation, Inc.
+ *
+ * This file is part of Libgcrypt.
+ *
+ * Libgcrypt 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.
+ *
+ * Libgcrypt 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.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <config.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+
+#include "g10lib.h"
+#include "cipher.h"
+#include "ath.h"
+#include "./cipher-internal.h"
+
+
+
+gcry_err_code_t
+_gcry_cipher_cbc_encrypt (gcry_cipher_hd_t c,
+                          unsigned char *outbuf, unsigned int outbuflen,
+                          const unsigned char *inbuf, unsigned int inbuflen)
+{
+  unsigned int n;
+  unsigned char *ivp;
+  int i;
+  size_t blocksize = c->cipher->blocksize;
+  unsigned nblocks = inbuflen / blocksize;
+
+  if (outbuflen < ((c->flags & GCRY_CIPHER_CBC_MAC)? blocksize : inbuflen))
+    return GPG_ERR_BUFFER_TOO_SHORT;
+
+  if ((inbuflen % c->cipher->blocksize)
+      && !(inbuflen > c->cipher->blocksize
+           && (c->flags & GCRY_CIPHER_CBC_CTS)))
+    return GPG_ERR_INV_LENGTH;
+
+  if ((c->flags & GCRY_CIPHER_CBC_CTS) && inbuflen > blocksize)
+    {
+      if ((inbuflen % blocksize) == 0)
+	nblocks--;
+    }
+
+  if (c->bulk.cbc_enc)
+    {
+      c->bulk.cbc_enc (&c->context.c, c->u_iv.iv, outbuf, inbuf, nblocks,
+                       (c->flags & GCRY_CIPHER_CBC_MAC));
+      inbuf  += nblocks * blocksize;
+      if (!(c->flags & GCRY_CIPHER_CBC_MAC))
+        outbuf += nblocks * blocksize;
+    }
+  else
+    {
+      for (n=0; n < nblocks; n++ )
+        {
+          for (ivp=c->u_iv.iv,i=0; i < blocksize; i++ )
+            outbuf[i] = inbuf[i] ^ *ivp++;
+          c->cipher->encrypt ( &c->context.c, outbuf, outbuf );
+          memcpy (c->u_iv.iv, outbuf, blocksize );
+          inbuf  += blocksize;
+          if (!(c->flags & GCRY_CIPHER_CBC_MAC))
+            outbuf += blocksize;
+        }
+    }
+
+  if ((c->flags & GCRY_CIPHER_CBC_CTS) && inbuflen > blocksize)
+    {
+      /* We have to be careful here, since outbuf might be equal to
+         inbuf.  */
+      int restbytes;
+      unsigned char b;
+
+      if ((inbuflen % blocksize) == 0)
+        restbytes = blocksize;
+      else
+        restbytes = inbuflen % blocksize;
+
+      outbuf -= blocksize;
+      for (ivp = c->u_iv.iv, i = 0; i < restbytes; i++)
+        {
+          b = inbuf[i];
+          outbuf[blocksize + i] = outbuf[i];
+          outbuf[i] = b ^ *ivp++;
+        }
+      for (; i < blocksize; i++)
+        outbuf[i] = 0 ^ *ivp++;
+
+      c->cipher->encrypt (&c->context.c, outbuf, outbuf);
+      memcpy (c->u_iv.iv, outbuf, blocksize);
+    }
+
+  return 0;
+}
+
+
+gcry_err_code_t
+_gcry_cipher_cbc_decrypt (gcry_cipher_hd_t c,
+                          unsigned char *outbuf, unsigned int outbuflen,
+                          const unsigned char *inbuf, unsigned int inbuflen)
+{
+  unsigned int n;
+  unsigned char *ivp;
+  int i;
+  size_t blocksize = c->cipher->blocksize;
+  unsigned int nblocks = inbuflen / blocksize;
+
+  if (outbuflen < inbuflen)
+    return GPG_ERR_BUFFER_TOO_SHORT;
+
+  if ((inbuflen % c->cipher->blocksize)
+      && !(inbuflen > c->cipher->blocksize
+           && (c->flags & GCRY_CIPHER_CBC_CTS)))
+    return GPG_ERR_INV_LENGTH;
+
+  if ((c->flags & GCRY_CIPHER_CBC_CTS) && inbuflen > blocksize)
+    {
+      nblocks--;
+      if ((inbuflen % blocksize) == 0)
+	nblocks--;
+      memcpy (c->lastiv, c->u_iv.iv, blocksize);
+    }
+
+  if (c->bulk.cbc_dec)
+    {
+      c->bulk.cbc_dec (&c->context.c, c->u_iv.iv, outbuf, inbuf, nblocks);
+      inbuf  += nblocks * blocksize;
+      outbuf += nblocks * blocksize;
+    }
+  else
+    {
+      for (n=0; n < nblocks; n++ )
+        {
+          /* Because outbuf and inbuf might be the same, we have to
+           * save the original ciphertext block.  We use LASTIV for
+           * this here because it is not used otherwise. */
+          memcpy (c->lastiv, inbuf, blocksize);
+          c->cipher->decrypt ( &c->context.c, outbuf, inbuf );
+          for (ivp=c->u_iv.iv,i=0; i < blocksize; i++ )
+	    outbuf[i] ^= *ivp++;
+          memcpy(c->u_iv.iv, c->lastiv, blocksize );
+          inbuf  += c->cipher->blocksize;
+          outbuf += c->cipher->blocksize;
+        }
+    }
+
+  if ((c->flags & GCRY_CIPHER_CBC_CTS) && inbuflen > blocksize)
+    {
+      int restbytes;
+
+      if ((inbuflen % blocksize) == 0)
+        restbytes = blocksize;
+      else
+        restbytes = inbuflen % blocksize;
+
+      memcpy (c->lastiv, c->u_iv.iv, blocksize );         /* Save Cn-2. */
+      memcpy (c->u_iv.iv, inbuf + blocksize, restbytes ); /* Save Cn. */
+
+      c->cipher->decrypt ( &c->context.c, outbuf, inbuf );
+      for (ivp=c->u_iv.iv,i=0; i < restbytes; i++ )
+        outbuf[i] ^= *ivp++;
+
+      memcpy(outbuf + blocksize, outbuf, restbytes);
+      for(i=restbytes; i < blocksize; i++)
+        c->u_iv.iv[i] = outbuf[i];
+      c->cipher->decrypt (&c->context.c, outbuf, c->u_iv.iv);
+      for(ivp=c->lastiv,i=0; i < blocksize; i++ )
+        outbuf[i] ^= *ivp++;
+      /* c->lastiv is now really lastlastiv, does this matter? */
+    }
+
+  return 0;
+}