From ee34d8cfbd0fbf7ba7429531d4bee1c43b074d8b Mon Sep 17 00:00:00 2001 From: Jouni Malinen Date: Thu, 25 Apr 2019 19:23:05 +0300 Subject: [PATCH 3/6] OpenSSL: Use BN_bn2binpad() or BN_bn2bin_padded() if available This converts crypto_bignum_to_bin() to use the OpenSSL/BoringSSL functions BN_bn2binpad()/BN_bn2bin_padded(), when available, to avoid differences in runtime and memory access patterns depending on the leading bytes of the BIGNUM value. OpenSSL 1.0.2 and LibreSSL do not include such functions, so those cases are still using the previous implementation where the BN_num_bytes() call may result in different memory access pattern. Signed-off-by: Jouni Malinen (cherry picked from commit 1e237903f5b5d3117342daf006c5878cdb45e3d3) --- src/crypto/crypto_openssl.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) --- a/src/crypto/crypto_openssl.c +++ b/src/crypto/crypto_openssl.c @@ -1295,7 +1295,13 @@ void crypto_bignum_deinit(struct crypto_ int crypto_bignum_to_bin(const struct crypto_bignum *a, u8 *buf, size_t buflen, size_t padlen) { +#ifdef OPENSSL_IS_BORINGSSL +#else /* OPENSSL_IS_BORINGSSL */ +#if OPENSSL_VERSION_NUMBER >= 0x10100000L && !defined(LIBRESSL_VERSION_NUMBER) +#else int num_bytes, offset; +#endif +#endif /* OPENSSL_IS_BORINGSSL */ if (TEST_FAIL()) return -1; @@ -1303,6 +1309,14 @@ int crypto_bignum_to_bin(const struct cr if (padlen > buflen) return -1; +#ifdef OPENSSL_IS_BORINGSSL + if (BN_bn2bin_padded(buf, padlen, (const BIGNUM *) a) == 0) + return -1; + return padlen; +#else /* OPENSSL_IS_BORINGSSL */ +#if OPENSSL_VERSION_NUMBER >= 0x10100000L && !defined(LIBRESSL_VERSION_NUMBER) + return BN_bn2binpad((const BIGNUM *) a, buf, padlen); +#else num_bytes = BN_num_bytes((const BIGNUM *) a); if ((size_t) num_bytes > buflen) return -1; @@ -1315,6 +1329,8 @@ int crypto_bignum_to_bin(const struct cr BN_bn2bin((const BIGNUM *) a, buf + offset); return num_bytes + offset; +#endif +#endif /* OPENSSL_IS_BORINGSSL */ }