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Revise signing preferences.

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We currently preferentially sign the largest hash available and
advertise such a preference for signatures we accept. We're just as
happy with SHA-256 and, all else equal, a smaller hash would be epsilon
more performant. We also currently claim, in TLS 1.3, we prefer P-384
over P-256 which is off.

Instead order SHA-256 first, next the larger SHA-2 hashes, and leave
SHA-1 at the bottom. Within a hash, order ECDSA > RSA-PSS > RSA-PKCS1.

This has the added consequence that we will preferentially pair P-256
with SHA-256 in signatures we generate instead of larger hashes that get
truncated anyway.

Change-Id: If4aee068ba6829e8c0ef7948f56e67a5213e4c50
Reviewed-on: https://boringssl-review.googlesource.com/11821
Reviewed-by: Adam Langley <agl@google.com>
This commit is contained in:
David Benjamin 2016-10-26 12:45:35 -04:00 committed by Adam Langley
parent 9415a14acf
commit 3a322f5e48
2 changed files with 49 additions and 38 deletions
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4
ssl/ssl_test.cc
View File

@ -1900,8 +1900,8 @@ static bool TestClientHello() {
0xc0, 0x28, 0x00, 0x39, 0x00, 0x6b, 0x00, 0x9c, 0x00, 0x9d, 0x00, 0x2f,
0x00, 0x3c, 0x00, 0x35, 0x00, 0x3d, 0x00, 0x0a, 0x01, 0x00, 0x00, 0x37,
0xff, 0x01, 0x00, 0x01, 0x00, 0x00, 0x17, 0x00, 0x00, 0x00, 0x23, 0x00,
0x00, 0x00, 0x0d, 0x00, 0x14, 0x00, 0x12, 0x08, 0x06, 0x06, 0x01, 0x08,
0x05, 0x05, 0x01, 0x05, 0x03, 0x08, 0x04, 0x04, 0x01, 0x04, 0x03, 0x02,
0x00, 0x00, 0x0d, 0x00, 0x14, 0x00, 0x12, 0x04, 0x03, 0x08, 0x04, 0x04,
0x01, 0x05, 0x03, 0x08, 0x05, 0x05, 0x01, 0x08, 0x06, 0x06, 0x01, 0x02,
0x01, 0x00, 0x0b, 0x00, 0x02, 0x01, 0x00, 0x00, 0x0a, 0x00, 0x08, 0x00,
0x06, 0x00, 0x1d, 0x00, 0x17, 0x00, 0x18,
};

83
ssl/t1_lib.c
View File

@ -442,62 +442,73 @@ int tls1_check_group_id(SSL *ssl, uint16_t group_id) {
}
/* kVerifySignatureAlgorithms is the default list of accepted signature
* algorithms for verifying. */
* algorithms for verifying.
*
* For now, RSA-PSS signature algorithms are not enabled on Android's system
* BoringSSL. Once the change in Chrome has stuck and the values are finalized,
* restore them. */
static const uint16_t kVerifySignatureAlgorithms[] = {
/* For now, do not enable RSA-PSS signature algorithms on Android's system
* BoringSSL. Once TLS 1.3 is finalized and the change in Chrome has stuck,
* restore them. */
/* Prefer SHA-256 algorithms. */
SSL_SIGN_ECDSA_SECP256R1_SHA256,
#if !defined(BORINGSSL_ANDROID_SYSTEM)
SSL_SIGN_RSA_PSS_SHA512,
SSL_SIGN_RSA_PSS_SHA256,
#endif
SSL_SIGN_RSA_PKCS1_SHA512,
SSL_SIGN_RSA_PKCS1_SHA256,
/* Larger hashes are acceptable. */
SSL_SIGN_ECDSA_SECP384R1_SHA384,
#if !defined(BORINGSSL_ANDROID_SYSTEM)
SSL_SIGN_RSA_PSS_SHA384,
#endif
SSL_SIGN_RSA_PKCS1_SHA384,
/* TODO(davidben): Remove this entry and SSL_CURVE_SECP521R1 from
* kDefaultGroups. */
#if defined(BORINGSSL_ANDROID_SYSTEM)
SSL_SIGN_ECDSA_SECP521R1_SHA512,
#endif
#if !defined(BORINGSSL_ANDROID_SYSTEM)
SSL_SIGN_RSA_PSS_SHA384,
#endif
SSL_SIGN_RSA_PKCS1_SHA384,
SSL_SIGN_ECDSA_SECP384R1_SHA384,
#if !defined(BORINGSSL_ANDROID_SYSTEM)
SSL_SIGN_RSA_PSS_SHA256,
#endif
SSL_SIGN_RSA_PKCS1_SHA256,
SSL_SIGN_ECDSA_SECP256R1_SHA256,
SSL_SIGN_RSA_PKCS1_SHA1,
};
/* kSignSignatureAlgorithms is the default list of supported signature
* algorithms for signing. */
static const uint16_t kSignSignatureAlgorithms[] = {
/* For now, do not enable RSA-PSS signature algorithms on Android's system
* BoringSSL. Once TLS 1.3 is finalized and the change in Chrome has stuck,
* restore them. */
#if !defined(BORINGSSL_ANDROID_SYSTEM)
SSL_SIGN_RSA_PSS_SHA512,
#endif
SSL_SIGN_RSA_PKCS1_SHA512,
SSL_SIGN_ECDSA_SECP521R1_SHA512,
#if !defined(BORINGSSL_ANDROID_SYSTEM)
SSL_SIGN_RSA_PSS_SHA384,
#endif
SSL_SIGN_RSA_PKCS1_SHA384,
SSL_SIGN_ECDSA_SECP384R1_SHA384,
/* For now, SHA-1 is still accepted but least preferable. */
SSL_SIGN_RSA_PKCS1_SHA1,
};
/* kSignSignatureAlgorithms is the default list of supported signature
* algorithms for signing.
*
* For now, RSA-PSS signature algorithms are not enabled on Android's system
* BoringSSL. Once the change in Chrome has stuck and the values are finalized,
* restore them. */
static const uint16_t kSignSignatureAlgorithms[] = {
/* Prefer SHA-256 algorithms. */
SSL_SIGN_ECDSA_SECP256R1_SHA256,
#if !defined(BORINGSSL_ANDROID_SYSTEM)
SSL_SIGN_RSA_PSS_SHA256,
#endif
SSL_SIGN_RSA_PKCS1_SHA256,
SSL_SIGN_ECDSA_SECP256R1_SHA256,
SSL_SIGN_RSA_PKCS1_SHA1,
/* If needed, sign larger hashes.
*
* TODO(davidben): Determine which of these may be pruned. */
SSL_SIGN_ECDSA_SECP384R1_SHA384,
#if !defined(BORINGSSL_ANDROID_SYSTEM)
SSL_SIGN_RSA_PSS_SHA384,
#endif
SSL_SIGN_RSA_PKCS1_SHA384,
SSL_SIGN_ECDSA_SECP521R1_SHA512,
#if !defined(BORINGSSL_ANDROID_SYSTEM)
SSL_SIGN_RSA_PSS_SHA512,
#endif
SSL_SIGN_RSA_PKCS1_SHA512,
/* If the peer supports nothing else, sign with SHA-1. */
SSL_SIGN_ECDSA_SHA1,
SSL_SIGN_RSA_PKCS1_SHA1,
};
size_t tls12_get_verify_sigalgs(const SSL *ssl, const uint16_t **out) {