1 files changed, 23 insertions, 15 deletions

diff --git a/src/lib/libcrypto/rsa/rsa_oaep.c b/src/lib/libcrypto/rsa/rsa_oaep.c
index d43ecaca63..3652677a99 100644
--- a/src/lib/libcrypto/rsa/rsa_oaep.c
+++ b/src/lib/libcrypto/rsa/rsa_oaep.c
@@ -28,6 +28,9 @@
 #include <openssl/rand.h>
 #include <openssl/sha.h>
 
+int MGF1(unsigned char *mask, long len,
+        const 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)
@@ -73,13 +76,11 @@ int RSA_padding_add_PKCS1_OAEP(unsigned char *to, int tlen,
            20);
 #endif
 
-        PKCS1_MGF1(dbmask, emlen - SHA_DIGEST_LENGTH, seed, SHA_DIGEST_LENGTH,
-                                                                EVP_sha1());
+        MGF1(dbmask, emlen - SHA_DIGEST_LENGTH, seed, SHA_DIGEST_LENGTH);
         for (i = 0; i < emlen - SHA_DIGEST_LENGTH; i++)
                 db[i] ^= dbmask[i];
 
-        PKCS1_MGF1(seedmask, SHA_DIGEST_LENGTH, db, emlen - SHA_DIGEST_LENGTH,
-                                                                EVP_sha1());
+        MGF1(seedmask, SHA_DIGEST_LENGTH, db, emlen - SHA_DIGEST_LENGTH);
         for (i = 0; i < SHA_DIGEST_LENGTH; i++)
                 seed[i] ^= seedmask[i];
 
@@ -95,6 +96,7 @@ int RSA_padding_check_PKCS1_OAEP(unsigned char *to, int tlen,
         const unsigned char *maskeddb;
         int lzero;
         unsigned char *db = NULL, seed[SHA_DIGEST_LENGTH], phash[SHA_DIGEST_LENGTH];
+        unsigned char *padded_from;
         int bad = 0;
 
         if (--num < 2 * SHA_DIGEST_LENGTH + 1)
@@ -105,8 +107,6 @@ int RSA_padding_check_PKCS1_OAEP(unsigned char *to, int tlen,
         lzero = num - flen;
         if (lzero < 0)
                 {
-                /* lzero == -1 */
-
                 /* signalling this error immediately after detection might allow
                  * for side-channel attacks (e.g. timing if 'plen' is huge
                  * -- cf. James H. Manger, "A Chosen Ciphertext Attack on RSA Optimal
@@ -114,22 +114,30 @@ int RSA_padding_check_PKCS1_OAEP(unsigned char *to, int tlen,
                  * so we use a 'bad' flag */
                 bad = 1;
                 lzero = 0;
+                flen = num; /* don't overflow the memcpy to padded_from */
                 }
-        maskeddb = from - lzero + SHA_DIGEST_LENGTH;
 
         dblen = num - SHA_DIGEST_LENGTH;
-        db = OPENSSL_malloc(dblen);
+        db = OPENSSL_malloc(dblen + num);
         if (db == NULL)
                 {
-                RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP, ERR_R_MALLOC_FAILURE);
+                RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP, ERR_R_MALLOC_FAILURE);
                 return -1;
                 }
 
-        PKCS1_MGF1(seed, SHA_DIGEST_LENGTH, maskeddb, dblen, EVP_sha1());
-        for (i = lzero; i < SHA_DIGEST_LENGTH; i++)
-                seed[i] ^= from[i - lzero];
+        /* Always do this zero-padding copy (even when lzero == 0)
+         * to avoid leaking timing info about the value of lzero. */
+        padded_from = db + dblen;
+        memset(padded_from, 0, lzero);
+        memcpy(padded_from + lzero, from, flen);
+
+        maskeddb = padded_from + SHA_DIGEST_LENGTH;
+
+        MGF1(seed, SHA_DIGEST_LENGTH, maskeddb, dblen);
+        for (i = 0; i < SHA_DIGEST_LENGTH; i++)
+                seed[i] ^= padded_from[i];
   
-        PKCS1_MGF1(db, dblen, seed, SHA_DIGEST_LENGTH, EVP_sha1());
+        MGF1(db, dblen, seed, SHA_DIGEST_LENGTH);
         for (i = 0; i < dblen; i++)
                 db[i] ^= maskeddb[i];
 
@@ -142,13 +150,13 @@ int RSA_padding_check_PKCS1_OAEP(unsigned char *to, int tlen,
                 for (i = SHA_DIGEST_LENGTH; i < dblen; i++)
                         if (db[i] != 0x00)
                                 break;
-                if (db[i] != 0x01 || i++ >= dblen)
+                if (i == dblen || db[i] != 0x01)
                         goto decoding_err;
                 else
                         {
                         /* everything looks OK */
 
-                        mlen = dblen - i;
+                        mlen = dblen - ++i;
                         if (tlen < mlen)
                                 {
                                 RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP, RSA_R_DATA_TOO_LARGE);