Fix from 0.9.8-stable.

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

diff --git a/crypto/rsa/rsa_oaep.c b/crypto/rsa/rsa_oaep.c
index e3f7c608ec8cf47af734ea56c722ed9d56214013..e238d10e5cc6fc517e0a6ce4cb42f453da2552ad 100644 (file)
--- a/crypto/rsa/rsa_oaep.c
+++ b/crypto/rsa/rsa_oaep.c
@@ -28,7 +28,7 @@
 #include <openssl/rand.h>
 #include <openssl/sha.h>
 
-int MGF1(unsigned char *mask, long len,
+static int MGF1(unsigned char *mask, long len,
        const unsigned char *seed, long seedlen);
 
 int RSA_padding_add_PKCS1_OAEP(unsigned char *to, int tlen,
@@ -52,13 +52,6 @@ int RSA_padding_add_PKCS1_OAEP(unsigned char *to, int tlen,
                return 0;
                }
 
-       dbmask = OPENSSL_malloc(emlen - SHA_DIGEST_LENGTH);
-       if (dbmask == NULL)
-               {
-               RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP, ERR_R_MALLOC_FAILURE);
-               return 0;
-               }
-
        to[0] = 0;
        seed = to + 1;
        db = to + SHA_DIGEST_LENGTH + 1;
@@ -76,11 +69,20 @@ int RSA_padding_add_PKCS1_OAEP(unsigned char *to, int tlen,
           20);
 #endif
 
-       MGF1(dbmask, emlen - SHA_DIGEST_LENGTH, seed, 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);
+               return 0;
+               }
+
+       if (MGF1(dbmask, emlen - SHA_DIGEST_LENGTH, seed, SHA_DIGEST_LENGTH) < 0)
+               return 0;
        for (i = 0; i < emlen - SHA_DIGEST_LENGTH; i++)
                db[i] ^= dbmask[i];
 
-       MGF1(seedmask, SHA_DIGEST_LENGTH, db, emlen - SHA_DIGEST_LENGTH);
+       if (MGF1(seedmask, SHA_DIGEST_LENGTH, db, emlen - SHA_DIGEST_LENGTH) < 0)
+               return 0;
        for (i = 0; i < SHA_DIGEST_LENGTH; i++)
                seed[i] ^= seedmask[i];
 
@@ -96,6 +98,7 @@ 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)
@@ -106,8 +109,6 @@ 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
@@ -115,22 +116,32 @@ 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;
                }
 
-       MGF1(seed, SHA_DIGEST_LENGTH, maskeddb, dblen);
-       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;
+
+       if (MGF1(seed, SHA_DIGEST_LENGTH, maskeddb, dblen))
+               return -1;
+       for (i = 0; i < SHA_DIGEST_LENGTH; i++)
+               seed[i] ^= padded_from[i];
   
-       MGF1(db, dblen, seed, SHA_DIGEST_LENGTH);
+       if (MGF1(db, dblen, seed, SHA_DIGEST_LENGTH))
+               return -1;
        for (i = 0; i < dblen; i++)
                db[i] ^= maskeddb[i];
 
@@ -143,13 +154,13 @@ 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);
@@ -170,28 +181,32 @@ decoding_err:
        return -1;
        }
 
-int MGF1(unsigned char *mask, long len,
-       const unsigned char *seed, long seedlen)
+int PKCS1_MGF1(unsigned char *mask, long len,
+       const unsigned char *seed, long seedlen, const EVP_MD *dgst)
        {
        long i, outlen = 0;
        unsigned char cnt[4];
        EVP_MD_CTX c;
-       unsigned char md[SHA_DIGEST_LENGTH];
+       unsigned char md[EVP_MAX_MD_SIZE];
+       int mdlen;
 
        EVP_MD_CTX_init(&c);
+       mdlen = EVP_MD_size(dgst);
+       if (mdlen < 0)
+               return -1;
        for (i = 0; outlen < len; i++)
                {
                cnt[0] = (unsigned char)((i >> 24) & 255);
                cnt[1] = (unsigned char)((i >> 16) & 255);
                cnt[2] = (unsigned char)((i >> 8)) & 255;
                cnt[3] = (unsigned char)(i & 255);
-               EVP_DigestInit_ex(&c,EVP_sha1(), NULL);
+               EVP_DigestInit_ex(&c,dgst, NULL);
                EVP_DigestUpdate(&c, seed, seedlen);
                EVP_DigestUpdate(&c, cnt, 4);
-               if (outlen + SHA_DIGEST_LENGTH <= len)
+               if (outlen + mdlen <= len)
                        {
                        EVP_DigestFinal_ex(&c, mask + outlen, NULL);
-                       outlen += SHA_DIGEST_LENGTH;
+                       outlen += mdlen;
                        }
                else
                        {
@@ -203,4 +218,10 @@ int MGF1(unsigned char *mask, long len,
        EVP_MD_CTX_cleanup(&c);
        return 0;
        }
+
+static int MGF1(unsigned char *mask, long len, const unsigned char *seed,
+                long seedlen)
+       {
+       return PKCS1_MGF1(mask, len, seed, seedlen, EVP_sha1());
+       }
 #endif