as in head

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

diff --git a/crypto/rsa/rsa_oaep.c b/crypto/rsa/rsa_oaep.c
index d402a200b9cb3017b4bfd7febf12b671cdeb96e3..1849e55cd5de0980afabbccc828f47e24105e4ef 100644 (file)
--- a/crypto/rsa/rsa_oaep.c
+++ b/crypto/rsa/rsa_oaep.c
@@ -2,22 +2,7 @@
 /* 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) */
-
-/* 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.
- */
-
+/* EME_OAEP as defined in RFC 2437 (PKCS #1 v2.0) */
 
 #if !defined(NO_SHA) && !defined(NO_SHA1)
 #include <stdio.h>
@@ -27,12 +12,10 @@
 #include <openssl/sha.h>
 #include <openssl/rand.h>
 
-int MGF1(unsigned char *mask, long len,
-       const unsigned char *seed, long seedlen);
+int MGF1(unsigned char *mask, long len, unsigned char *seed, long seedlen);
 
 int RSA_padding_add_PKCS1_OAEP(unsigned char *to, int tlen,
-       const unsigned char *from, int flen,
-       const unsigned char *param, int plen)
+            unsigned char *from, int flen, unsigned char *param, int plen)
     {
     int i, emlen = tlen - 1;
     unsigned char *db, *seed;
@@ -88,20 +71,22 @@ int RSA_padding_add_PKCS1_OAEP(unsigned char *to, int tlen,
     }
 
 int RSA_padding_check_PKCS1_OAEP(unsigned char *to, int tlen,
-       const unsigned char *from, int flen, int num,
-       const unsigned char *param, int plen)
+            unsigned char *from, int flen, int num, unsigned char *param,
+            int plen)
     {
     int i, dblen, mlen = -1;
-    const unsigned char *maskeddb;
+    unsigned char *maskeddb;
     int lzero;
-    unsigned char *db, seed[SHA_DIGEST_LENGTH], phash[SHA_DIGEST_LENGTH];
+    unsigned char *db = NULL, seed[SHA_DIGEST_LENGTH], phash[SHA_DIGEST_LENGTH];
 
     if (--num < 2 * SHA_DIGEST_LENGTH + 1)
-       {
-       RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP, RSA_R_OAEP_DECODING_ERROR);
-       return (-1);
-       }
+       goto decoding_err;
 
+    lzero = num - flen;
+    if (lzero < 0)
+       goto decoding_err;
+    maskeddb = from - lzero + SHA_DIGEST_LENGTH;
+    
     dblen = num - SHA_DIGEST_LENGTH;
     db = OPENSSL_malloc(dblen);
     if (db == NULL)
@@ -110,9 +95,6 @@ int RSA_padding_check_PKCS1_OAEP(unsigned char *to, int tlen,
        return (-1);
        }
 
-    lzero = num - flen;
-    maskeddb = from - lzero + SHA_DIGEST_LENGTH;
-    
     MGF1(seed, SHA_DIGEST_LENGTH, maskeddb, dblen);
     for (i = lzero; i < SHA_DIGEST_LENGTH; i++)
        seed[i] ^= from[i - lzero];
@@ -124,21 +106,20 @@ int RSA_padding_check_PKCS1_OAEP(unsigned char *to, int tlen,
     SHA1(param, plen, phash);
 
     if (memcmp(db, phash, SHA_DIGEST_LENGTH) != 0)
-       RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP, RSA_R_OAEP_DECODING_ERROR);
+       goto decoding_err;
     else
        {
        for (i = SHA_DIGEST_LENGTH; i < dblen; i++)
            if (db[i] != 0x00)
                break;
        if (db[i] != 0x01 || i++ >= dblen)
-           RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP,
-                  RSA_R_OAEP_DECODING_ERROR);
+         goto decoding_err;
        else
            {
            mlen = dblen - i;
            if (tlen < mlen)
                {
-               RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP, RSA_R_DATA_TOO_LARGE);
+               RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP, RSA_R_DATA_TOO_LARGE);
                mlen = -1;
                }
            else
@@ -147,10 +128,16 @@ int RSA_padding_check_PKCS1_OAEP(unsigned char *to, int tlen,
        }
     OPENSSL_free(db);
     return (mlen);
+
+decoding_err:
+    /* to avoid chosen ciphertext attacks, the error message should not reveal
+     * which kind of decoding error happened */
+    RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP, RSA_R_OAEP_DECODING_ERROR);
+    if (db != NULL) OPENSSL_free(db);
+    return -1;
     }
 
-int MGF1(unsigned char *mask, long len,
-       const unsigned char *seed, long seedlen)
+int MGF1(unsigned char *mask, long len, unsigned char *seed, long seedlen)
     {
     long i, outlen = 0;
     unsigned char cnt[4];