diff options
| author | Dr. Stephen Henson <steve@openssl.org> | 2008-05-19 21:33:55 +0000 |
|---|---|---|
| committer | Dr. Stephen Henson <steve@openssl.org> | 2008-05-19 21:33:55 +0000 |
| commit | 94fd382f8b4abdc3e65e5be584b76c2b37017d7a (patch) | |
| tree | 53e8a78208541e7dfad6e21d7859b367c3122c05 /crypto/rsa | |
| parent | 4bd4afa34e4c67279edee29c93b03bd7ed144d88 (diff) | |
Fix two invalid memory reads in RSA OAEP mode.
Submitted by: Ivan Nestlerode <inestlerode@us.ibm.com>
Reviewed by: steve
Diffstat (limited to 'crypto/rsa')
| -rw-r--r-- | crypto/rsa/rsa_oaep.c | 23 |
1 files changed, 15 insertions, 8 deletions
diff --git a/crypto/rsa/rsa_oaep.c b/crypto/rsa/rsa_oaep.c index 45d6f6ef8a..3652677a99 100644 --- a/crypto/rsa/rsa_oaep.c +++ b/crypto/rsa/rsa_oaep.c @@ -96,6 +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) @@ -106,8 +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 @@ -115,20 +114,28 @@ 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_CHECK_PKCS1_OAEP, ERR_R_MALLOC_FAILURE); return -1; } + /* 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 = lzero; i < SHA_DIGEST_LENGTH; i++) - seed[i] ^= from[i - lzero]; + for (i = 0; i < SHA_DIGEST_LENGTH; i++) + seed[i] ^= padded_from[i]; MGF1(db, dblen, seed, SHA_DIGEST_LENGTH); for (i = 0; i < dblen; i++) @@ -143,13 +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); |