[PATCH 1/2] Drop _gcry_cipher_ofb_decrypt as it duplicates _gcry_cipher_ofb_encrypt

[Jussi Kivilinna]

From: Dmitry Eremin-Solenikov <dbaryshkov at gmail.com>

* cipher/cipher.c (cipher_decrypt): Use _gcry_cipher_ofb_encrypt for OFB
  decryption.
* cipher/cipher-internal.h: Remove _gcry_cipher_ofb_decrypt declaration.
* cipher/cipher-ofb.c (_gcry_cipher_ofb_decrypt): Remove.
  (_gcry_cipher_ofb_encrypt): remove copying of IV to lastiv, it's
  unused there.

Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov at gmail.com>
---
 cipher/cipher-internal.h |    4 ---
 cipher/cipher-ofb.c      |   69 ----------------------------------------------
 cipher/cipher.c          |    2 +
 3 files changed, 1 insertion(+), 74 deletions(-)

diff --git a/cipher/cipher-internal.h b/cipher/cipher-internal.h
index 981caa8..f528c84 100644
--- a/cipher/cipher-internal.h
+++ b/cipher/cipher-internal.h
@@ -173,10 +173,6 @@ gcry_err_code_t _gcry_cipher_ofb_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_ofb_decrypt
-/*           */ (gcry_cipher_hd_t c,
-                 unsigned char *outbuf, unsigned int outbuflen,
-                 const unsigned char *inbuf, unsigned int inbuflen);
 
 /*-- cipher-ctr.c --*/
 gcry_err_code_t _gcry_cipher_ctr_encrypt
diff --git a/cipher/cipher-ofb.c b/cipher/cipher-ofb.c
index 333a748..c6d84dd 100644
--- a/cipher/cipher-ofb.c
+++ b/cipher/cipher-ofb.c
@@ -70,7 +70,6 @@ _gcry_cipher_ofb_encrypt (gcry_cipher_hd_t c,
   while ( inbuflen >= blocksize )
     {
       /* Encrypt the IV (and save the current one). */
-      buf_cpy( c->lastiv, c->u_iv.iv, blocksize );
       nburn = enc_fn ( &c->context.c, c->u_iv.iv, c->u_iv.iv );
       burn = nburn > burn ? nburn : burn;
       buf_xor(outbuf, c->u_iv.iv, inbuf, blocksize);
@@ -80,74 +79,6 @@ _gcry_cipher_ofb_encrypt (gcry_cipher_hd_t c,
     }
   if ( inbuflen )
     { /* process the remaining bytes */
-      buf_cpy( c->lastiv, c->u_iv.iv, blocksize );
-      nburn = enc_fn ( &c->context.c, c->u_iv.iv, c->u_iv.iv );
-      burn = nburn > burn ? nburn : burn;
-      c->unused = blocksize;
-      c->unused -= inbuflen;
-      buf_xor(outbuf, c->u_iv.iv, inbuf, inbuflen);
-      outbuf += inbuflen;
-      inbuf += inbuflen;
-      inbuflen = 0;
-    }
-
-  if (burn > 0)
-    _gcry_burn_stack (burn + 4 * sizeof(void *));
-
-  return 0;
-}
-
-
-gcry_err_code_t
-_gcry_cipher_ofb_decrypt (gcry_cipher_hd_t c,
-                          unsigned char *outbuf, unsigned int outbuflen,
-                          const unsigned char *inbuf, unsigned int inbuflen)
-{
-  unsigned char *ivp;
-  gcry_cipher_encrypt_t enc_fn = c->spec->encrypt;
-  size_t blocksize = c->spec->blocksize;
-  unsigned int burn, nburn;
-
-  if (outbuflen < inbuflen)
-    return GPG_ERR_BUFFER_TOO_SHORT;
-
-  if( inbuflen <= c->unused )
-    {
-      /* Short enough to be encoded by the remaining XOR mask. */
-      ivp = c->u_iv.iv + blocksize - c->unused;
-      buf_xor(outbuf, ivp, inbuf, inbuflen);
-      c->unused -= inbuflen;
-      return 0;
-    }
-
-  burn = 0;
-
-  if ( c->unused )
-    {
-      inbuflen -= c->unused;
-      ivp = c->u_iv.iv + blocksize - c->unused;
-      buf_xor(outbuf, ivp, inbuf, c->unused);
-      outbuf += c->unused;
-      inbuf += c->unused;
-      c->unused = 0;
-    }
-
-  /* Now we can process complete blocks. */
-  while ( inbuflen >= blocksize )
-    {
-      /* Encrypt the IV (and save the current one). */
-      buf_cpy( c->lastiv, c->u_iv.iv, blocksize );
-      nburn = enc_fn ( &c->context.c, c->u_iv.iv, c->u_iv.iv );
-      burn = nburn > burn ? nburn : burn;
-      buf_xor(outbuf, c->u_iv.iv, inbuf, blocksize);
-      outbuf += blocksize;
-      inbuf += blocksize;
-      inbuflen -= blocksize;
-    }
-  if ( inbuflen )
-    { /* Process the remaining bytes. */
-      /* Encrypt the IV (and save the current one). */
-      buf_cpy( c->lastiv, c->u_iv.iv, blocksize );
       nburn = enc_fn ( &c->context.c, c->u_iv.iv, c->u_iv.iv );
       burn = nburn > burn ? nburn : burn;
       c->unused = blocksize;
diff --git a/cipher/cipher.c b/cipher/cipher.c
index c0d1d0b..df6d202 100644
--- a/cipher/cipher.c
+++ b/cipher/cipher.c
@@ -814,7 +814,7 @@ cipher_decrypt (gcry_cipher_hd_t c, byte *outbuf, unsigned int outbuflen,
       break;
 
     case GCRY_CIPHER_MODE_OFB:
-      rc = _gcry_cipher_ofb_decrypt (c, outbuf, outbuflen, inbuf, inbuflen);
+      rc = _gcry_cipher_ofb_encrypt (c, outbuf, outbuflen, inbuf, inbuflen);
       break;
 
     case GCRY_CIPHER_MODE_CTR: