make sure we don't write to seed[-1]

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

diff --git a/crypto/rsa/rsa_oaep.c b/crypto/rsa/rsa_oaep.c
index 8d306d1eadf9dcd069a4c6c914353764625b7c36..a3361dc3d76a6d6e197ba65bc99682d68a88c813 100644 (file)
--- a/crypto/rsa/rsa_oaep.c
+++ b/crypto/rsa/rsa_oaep.c
@@ -8,18 +8,18 @@
  * <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.
- *
- * Note that for RSA OAEP a security proof in the
- * random oracle model *does* exist if 160 < log_2(N/e);
- * cf. section 7.2 ("But RSA-OAEP with exponent 3 is
- * provably secure") of Shoup's paper.  (The slight
- * differences between the OAEP definition used by Shoup
- * and OAEP as defined in RFC 2437 should not affect
- * this result.)
+ * 
+ * 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)
+#if !defined(OPENSSL_NO_SHA) && !defined(OPENSSL_NO_SHA1)
 #include <stdio.h>
 #include "cryptlib.h"
 #include <openssl/bn.h>
@@ -111,6 +111,11 @@ int RSA_padding_check_PKCS1_OAEP(unsigned char *to, int tlen,
        }
 
     lzero = num - flen;
+    if (lzero < 0)
+    {
+    RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP, RSA_R_OAEP_DECODING_ERROR);
+    return (-1);
+    }
     maskeddb = from - lzero + SHA_DIGEST_LENGTH;
     
     MGF1(seed, SHA_DIGEST_LENGTH, maskeddb, dblen);