diff options
Diffstat (limited to 'deps/openssl/openssl/crypto/rsa/rsa_oaep.c')
| -rw-r--r-- | deps/openssl/openssl/crypto/rsa/rsa_oaep.c | 48 |
1 files changed, 24 insertions, 24 deletions
diff --git a/deps/openssl/openssl/crypto/rsa/rsa_oaep.c b/deps/openssl/openssl/crypto/rsa/rsa_oaep.c index 689e6dc222..48b888bf27 100644 --- a/deps/openssl/openssl/crypto/rsa/rsa_oaep.c +++ b/deps/openssl/openssl/crypto/rsa/rsa_oaep.c @@ -1,5 +1,5 @@ /* - * Copyright 1999-2018 The OpenSSL Project Authors. All Rights Reserved. + * Copyright 1999-2019 The OpenSSL Project Authors. All Rights Reserved. * * Licensed under the OpenSSL license (the "License"). You may not use * this file except in compliance with the License. You can obtain a copy @@ -143,7 +143,7 @@ int RSA_padding_check_PKCS1_OAEP_mgf1(unsigned char *to, int tlen, * |num| is the length of the modulus; |flen| is the length of the * encoded message. Therefore, for any |from| that was obtained by * decrypting a ciphertext, we must have |flen| <= |num|. Similarly, - * num < 2 * mdlen + 2 must hold for the modulus irrespective of + * |num| >= 2 * |mdlen| + 2 must hold for the modulus irrespective of * the ciphertext, see PKCS #1 v2.2, section 7.1.2. * This does not leak any side-channel information. */ @@ -179,17 +179,16 @@ int RSA_padding_check_PKCS1_OAEP_mgf1(unsigned char *to, int tlen, from -= 1 & mask; *--em = *from & mask; } - from = em; /* * The first byte must be zero, however we must not leak if this is * true. See James H. Manger, "A Chosen Ciphertext Attack on RSA * Optimal Asymmetric Encryption Padding (OAEP) [...]", CRYPTO 2001). */ - good = constant_time_is_zero(from[0]); + good = constant_time_is_zero(em[0]); - maskedseed = from + 1; - maskeddb = from + 1 + mdlen; + maskedseed = em + 1; + maskeddb = em + 1 + mdlen; if (PKCS1_MGF1(seed, mdlen, maskeddb, dblen, mgf1md)) goto cleanup; @@ -230,29 +229,30 @@ int RSA_padding_check_PKCS1_OAEP_mgf1(unsigned char *to, int tlen, mlen = dblen - msg_index; /* - * For good measure, do this check in constant tine as well. + * For good measure, do this check in constant time as well. */ good &= constant_time_ge(tlen, mlen); /* - * Even though we can't fake result's length, we can pretend copying - * |tlen| bytes where |mlen| bytes would be real. Last |tlen| of |dblen| - * bytes are viewed as circular buffer with start at |tlen|-|mlen'|, - * where |mlen'| is "saturated" |mlen| value. Deducing information - * about failure or |mlen| would take attacker's ability to observe - * memory access pattern with byte granularity *as it occurs*. It - * should be noted that failure is indistinguishable from normal - * operation if |tlen| is fixed by protocol. + * Move the result in-place by |dblen|-|mdlen|-1-|mlen| bytes to the left. + * Then if |good| move |mlen| bytes from |db|+|mdlen|+1 to |to|. + * Otherwise leave |to| unchanged. + * Copy the memory back in a way that does not reveal the size of + * the data being copied via a timing side channel. This requires copying + * parts of the buffer multiple times based on the bits set in the real + * length. Clear bits do a non-copy with identical access pattern. + * The loop below has overall complexity of O(N*log(N)). */ - tlen = constant_time_select_int(constant_time_lt(dblen, tlen), dblen, tlen); - msg_index = constant_time_select_int(good, msg_index, dblen - tlen); - mlen = dblen - msg_index; - for (from = db + msg_index, mask = good, i = 0; i < tlen; i++) { - unsigned int equals = constant_time_eq(i, mlen); - - from -= dblen & equals; /* if (i == dblen) rewind */ - mask &= mask ^ equals; /* if (i == dblen) mask = 0 */ - to[i] = constant_time_select_8(mask, from[i], to[i]); + tlen = constant_time_select_int(constant_time_lt(dblen - mdlen - 1, tlen), + dblen - mdlen - 1, tlen); + for (msg_index = 1; msg_index < dblen - mdlen - 1; msg_index <<= 1) { + mask = ~constant_time_eq(msg_index & (dblen - mdlen - 1 - mlen), 0); + for (i = mdlen + 1; i < dblen - msg_index; i++) + db[i] = constant_time_select_8(mask, db[i + msg_index], db[i]); + } + for (i = 0; i < tlen; i++) { + mask = good & constant_time_lt(i, mlen); + to[i] = constant_time_select_8(mask, db[i + mdlen + 1], to[i]); } /* |