diff options
Diffstat (limited to 'freebsd/crypto/openssl/crypto/rsa/rsa_oaep.c')
| -rw-r--r-- | freebsd/crypto/openssl/crypto/rsa/rsa_oaep.c | 92 |
1 files changed, 56 insertions, 36 deletions
diff --git a/freebsd/crypto/openssl/crypto/rsa/rsa_oaep.c b/freebsd/crypto/openssl/crypto/rsa/rsa_oaep.c index 7e00779b..a5e97506 100644 --- a/freebsd/crypto/openssl/crypto/rsa/rsa_oaep.c +++ b/freebsd/crypto/openssl/crypto/rsa/rsa_oaep.c @@ -1,7 +1,7 @@ #include <machine/rtems-bsd-user-space.h> /* - * 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 @@ -122,7 +122,7 @@ int RSA_padding_check_PKCS1_OAEP_mgf1(unsigned char *to, int tlen, const EVP_MD *mgf1md) { int i, dblen = 0, mlen = -1, one_index = 0, msg_index; - unsigned int good, found_one_byte; + unsigned int good = 0, found_one_byte, mask; const unsigned char *maskedseed, *maskeddb; /* * |em| is the encoded message, zero-padded to exactly |num| bytes: em = @@ -145,12 +145,15 @@ 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. */ - if (num < flen || num < 2 * mdlen + 2) - goto decoding_err; + if (num < flen || num < 2 * mdlen + 2) { + RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP_MGF1, + RSA_R_OAEP_DECODING_ERROR); + return -1; + } dblen = num - mdlen - 1; db = OPENSSL_malloc(dblen); @@ -159,24 +162,24 @@ int RSA_padding_check_PKCS1_OAEP_mgf1(unsigned char *to, int tlen, goto cleanup; } - if (flen != num) { - em = OPENSSL_zalloc(num); - if (em == NULL) { - RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP_MGF1, - ERR_R_MALLOC_FAILURE); - goto cleanup; - } + em = OPENSSL_malloc(num); + if (em == NULL) { + RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP_MGF1, + ERR_R_MALLOC_FAILURE); + goto cleanup; + } - /* - * Caller is encouraged to pass zero-padded message created with - * BN_bn2binpad, but if it doesn't, we do this zero-padding copy - * to avoid leaking that information. The copy still leaks some - * side-channel information, but it's impossible to have a fixed - * memory access pattern since we can't read out of the bounds of - * |from|. - */ - memcpy(em + num - flen, from, flen); - from = em; + /* + * Caller is encouraged to pass zero-padded message created with + * BN_bn2binpad. Trouble is that since we can't read out of |from|'s + * bounds, it's impossible to have an invariant memory access pattern + * in case |from| was not zero-padded in advance. + */ + for (from += flen, em += num, i = 0; i < num; i++) { + mask = ~constant_time_is_zero(flen); + flen -= 1 & mask; + from -= 1 & mask; + *--em = *from & mask; } /* @@ -184,10 +187,10 @@ int RSA_padding_check_PKCS1_OAEP_mgf1(unsigned char *to, int tlen, * 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; @@ -224,32 +227,49 @@ int RSA_padding_check_PKCS1_OAEP_mgf1(unsigned char *to, int tlen, * so plaintext-awareness ensures timing side-channels are no longer a * concern. */ - if (!good) - goto decoding_err; - msg_index = one_index + 1; mlen = dblen - msg_index; - if (tlen < mlen) { - RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP_MGF1, RSA_R_DATA_TOO_LARGE); - mlen = -1; - } else { - memcpy(to, db + msg_index, mlen); - goto cleanup; + /* + * For good measure, do this check in constant time as well. + */ + good &= constant_time_ge(tlen, mlen); + + /* + * 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 - 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]); } - decoding_err: /* * To avoid chosen ciphertext attacks, the error message should not * reveal which kind of decoding error happened. */ RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP_MGF1, RSA_R_OAEP_DECODING_ERROR); + err_clear_last_constant_time(1 & good); cleanup: OPENSSL_cleanse(seed, sizeof(seed)); OPENSSL_clear_free(db, dblen); OPENSSL_clear_free(em, num); - return mlen; + + return constant_time_select_int(good, mlen, -1); } int PKCS1_MGF1(unsigned char *mask, long len, |