diff options
Diffstat (limited to 'crypto/rsa/rsa_pk1.c')
-rw-r--r-- | crypto/rsa/rsa_pk1.c | 39 |
1 files changed, 21 insertions, 18 deletions
diff --git a/crypto/rsa/rsa_pk1.c b/crypto/rsa/rsa_pk1.c index 7d453ff..a1134f1 100644 --- a/crypto/rsa/rsa_pk1.c +++ b/crypto/rsa/rsa_pk1.c @@ -175,27 +175,30 @@ int RSA_padding_check_PKCS1_type_2(unsigned char *to, int tlen, if (num < 11) goto err; - em = OPENSSL_zalloc(num); - if (em == NULL) { - RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_2, ERR_R_MALLOC_FAILURE); - return -1; + if (flen != num) { + em = OPENSSL_zalloc(num); + if (em == NULL) { + RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_2, ERR_R_MALLOC_FAILURE); + return -1; + } + /* + * 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; } - /* - * Always do this zero-padding copy (even when num == flen) 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|. - * - * TODO(emilia): Consider porting BN_bn2bin_padded from BoringSSL. - */ - memcpy(em + num - flen, from, flen); - good = constant_time_is_zero(em[0]); - good &= constant_time_eq(em[1], 2); + good = constant_time_is_zero(from[0]); + good &= constant_time_eq(from[1], 2); found_zero_byte = 0; for (i = 2; i < num; i++) { - unsigned int equals0 = constant_time_is_zero(em[i]); + unsigned int equals0 = constant_time_is_zero(from[i]); zero_index = constant_time_select_int(~found_zero_byte & equals0, i, zero_index); @@ -203,7 +206,7 @@ int RSA_padding_check_PKCS1_type_2(unsigned char *to, int tlen, } /* - * PS must be at least 8 bytes long, and it starts two bytes into |em|. + * PS must be at least 8 bytes long, and it starts two bytes into |from|. * If we never found a 0-byte, then |zero_index| is 0 and the check * also fails. */ @@ -232,7 +235,7 @@ int RSA_padding_check_PKCS1_type_2(unsigned char *to, int tlen, goto err; } - memcpy(to, em + msg_index, mlen); + memcpy(to, from + msg_index, mlen); err: OPENSSL_clear_free(em, num); |