Update "OAEP reconsidered" comment

[openssl.git] / crypto / rsa / rsa_oaep.c

diff --git a/crypto/rsa/rsa_oaep.c b/crypto/rsa/rsa_oaep.c
index e3c7444ac44b3ca1d8289252bd87715237c94e64..d402a200b9cb3017b4bfd7febf12b671cdeb96e3 100644 (file)
--- a/crypto/rsa/rsa_oaep.c
+++ b/crypto/rsa/rsa_oaep.c
@@ -2,9 +2,24 @@
 /* Written by Ulf Moeller. This software is distributed on an "AS IS"
    basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. */
 
-/* EME_OAEP as defined in RFC 2437 (PKCS #1 v2.0) */
-
-#ifndef NO_SHA
+/* EME-OAEP as defined in RFC 2437 (PKCS #1 v2.0) */
+
+/* See Victor Shoup, "OAEP reconsidered," Nov. 2000,
+ * <URL: http://www.shoup.net/papers/oaep.ps.Z>
+ * for problems with the security proof for the
+ * original OAEP scheme, which EME-OAEP is based on.
+ * 
+ * A new proof can be found in E. Fujisaki, T. Okamoto,
+ * D. Pointcheval, J. Stern, "RSA-OEAP is Still Alive!",
+ * Dec. 2000, <URL: http://eprint.iacr.org/2000/061/>.
+ * The new proof has stronger requirements for the
+ * underlying permutation: "partial-one-wayness" instead
+ * of one-wayness.  For the RSA function, this is
+ * an equivalent notion.
+ */
+
+
+#if !defined(NO_SHA) && !defined(NO_SHA1)
 #include <stdio.h>
 #include "cryptlib.h"
 #include <openssl/bn.h>
@@ -12,10 +27,12 @@
 #include <openssl/sha.h>
 #include <openssl/rand.h>
 
-int MGF1(unsigned char *mask, long len, unsigned char *seed, long seedlen);
+int MGF1(unsigned char *mask, long len,
+       const unsigned char *seed, long seedlen);
 
 int RSA_padding_add_PKCS1_OAEP(unsigned char *to, int tlen,
-            unsigned char *from, int flen, unsigned char *param, int plen)
+       const unsigned char *from, int flen,
+       const unsigned char *param, int plen)
     {
     int i, emlen = tlen - 1;
     unsigned char *db, *seed;
@@ -34,7 +51,7 @@ int RSA_padding_add_PKCS1_OAEP(unsigned char *to, int tlen,
        return (0);
        }
     
-    dbmask = Malloc(emlen - SHA_DIGEST_LENGTH);
+    dbmask = OPENSSL_malloc(emlen - SHA_DIGEST_LENGTH);
     if (dbmask == NULL)
        {
        RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP, ERR_R_MALLOC_FAILURE);
@@ -50,7 +67,8 @@ int RSA_padding_add_PKCS1_OAEP(unsigned char *to, int tlen,
           emlen - flen - 2 * SHA_DIGEST_LENGTH - 1);
     db[emlen - flen - SHA_DIGEST_LENGTH - 1] = 0x01;
     memcpy(db + emlen - flen - SHA_DIGEST_LENGTH, from, (unsigned int) flen);
-    RAND_bytes(seed, SHA_DIGEST_LENGTH);
+    if (RAND_bytes(seed, SHA_DIGEST_LENGTH) <= 0)
+       return (0);
 #ifdef PKCS_TESTVECT
     memcpy(seed,
           "\xaa\xfd\x12\xf6\x59\xca\xe6\x34\x89\xb4\x79\xe5\x07\x6d\xde\xc2\xf0\x6c\xb5\x8f",
@@ -65,37 +83,39 @@ int RSA_padding_add_PKCS1_OAEP(unsigned char *to, int tlen,
     for (i = 0; i < SHA_DIGEST_LENGTH; i++)
        seed[i] ^= seedmask[i];
 
-    Free(dbmask);
+    OPENSSL_free(dbmask);
     return (1);
     }
 
 int RSA_padding_check_PKCS1_OAEP(unsigned char *to, int tlen,
-            unsigned char *from, int flen, int num, unsigned char *param,
-            int plen)
+       const unsigned char *from, int flen, int num,
+       const unsigned char *param, int plen)
     {
     int i, dblen, mlen = -1;
-    unsigned char *maskeddb;
+    const unsigned char *maskeddb;
+    int lzero;
     unsigned char *db, seed[SHA_DIGEST_LENGTH], phash[SHA_DIGEST_LENGTH];
 
-    if (flen < 2 * SHA_DIGEST_LENGTH + 1)
+    if (--num < 2 * SHA_DIGEST_LENGTH + 1)
        {
        RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP, RSA_R_OAEP_DECODING_ERROR);
        return (-1);
        }
 
-    dblen = flen - SHA_DIGEST_LENGTH;
-    db = Malloc(dblen);
+    dblen = num - SHA_DIGEST_LENGTH;
+    db = OPENSSL_malloc(dblen);
     if (db == NULL)
        {
        RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP, ERR_R_MALLOC_FAILURE);
        return (-1);
        }
 
-    maskeddb = from + SHA_DIGEST_LENGTH;
+    lzero = num - flen;
+    maskeddb = from - lzero + SHA_DIGEST_LENGTH;
     
     MGF1(seed, SHA_DIGEST_LENGTH, maskeddb, dblen);
-    for (i = 0; i < SHA_DIGEST_LENGTH; i++)
-       seed[i] ^= from[i];
+    for (i = lzero; i < SHA_DIGEST_LENGTH; i++)
+       seed[i] ^= from[i - lzero];
   
     MGF1(db, dblen, seed, SHA_DIGEST_LENGTH);
     for (i = 0; i < dblen; i++)
@@ -125,11 +145,12 @@ int RSA_padding_check_PKCS1_OAEP(unsigned char *to, int tlen,
                memcpy(to, db + i, mlen);
            }
        }
-    Free(db);
+    OPENSSL_free(db);
     return (mlen);
     }
 
-int MGF1(unsigned char *mask, long len, unsigned char *seed, long seedlen)
+int MGF1(unsigned char *mask, long len,
+       const unsigned char *seed, long seedlen)
     {
     long i, outlen = 0;
     unsigned char cnt[4];