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Stop allowing SHA-224 in TLS 1.2.

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Take the mappings for MD5 and SHA-224 values out of the code altogether. This
aligns with the current TLS 1.3 draft.

For MD5, this is a no-op. It is not currently possible to configure accepted
signature algorithms, MD5 wasn't in the hardcoded list, and we already had a
test ensuring we enforced our preferences correctly. MD5 also wasn't in the
default list of hashes our keys could sign and no one overrides it with a
different hash.

For SHA-224, this is not quite a no-op. The hardcoded accepted signature
algorithms list included SHA-224, so this will break servers relying on that.
However, Chrome's metrics have zero data points of servers picking SHA-224 and
no other major browser includes it. Thus that should be safe.

SHA-224 was also in the default list of hashes we are willing to sign. For
client certificates, Chromium's abstractions already did not allow signing
SHA-224, so this is a no-op there. For servers, this will break any clients
which only accept SHA-224. But no major browsers do this and I am not aware of
any client implementation which does such ridiculous thing.

(SHA-1's still in there. Getting rid of that one is going to take more effort.)

Change-Id: I6a765fdeea9e19348e409d58a0eac770b318e599
Reviewed-on: https://boringssl-review.googlesource.com/7020
Reviewed-by: Adam Langley <agl@google.com>
This commit is contained in:
David Benjamin 2016-01-29 15:28:58 -05:00 committed by Adam Langley
parent 5fa8f5bc9a
commit 72f7e21087
2 changed files with 7 additions and 15 deletions
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21
ssl/t1_lib.c
View File

@ -510,7 +510,6 @@ static const uint8_t tls12_sigalgs[] = {
tlsext_sigalg(TLSEXT_hash_sha512)
tlsext_sigalg(TLSEXT_hash_sha384)
tlsext_sigalg(TLSEXT_hash_sha256)
tlsext_sigalg(TLSEXT_hash_sha224)
tlsext_sigalg(TLSEXT_hash_sha1)
};
@ -2564,12 +2563,12 @@ typedef struct {
int id;
} tls12_lookup;
static const tls12_lookup tls12_md[] = {{NID_md5, TLSEXT_hash_md5},
{NID_sha1, TLSEXT_hash_sha1},
{NID_sha224, TLSEXT_hash_sha224},
{NID_sha256, TLSEXT_hash_sha256},
{NID_sha384, TLSEXT_hash_sha384},
{NID_sha512, TLSEXT_hash_sha512}};
static const tls12_lookup tls12_md[] = {
{NID_sha1, TLSEXT_hash_sha1},
{NID_sha256, TLSEXT_hash_sha256},
{NID_sha384, TLSEXT_hash_sha384},
{NID_sha512, TLSEXT_hash_sha512},
};
static const tls12_lookup tls12_sig[] = {{EVP_PKEY_RSA, TLSEXT_signature_rsa},
{EVP_PKEY_EC, TLSEXT_signature_ecdsa}};
@ -2603,15 +2602,9 @@ int tls12_add_sigandhash(SSL *ssl, CBB *out, const EVP_MD *md) {
const EVP_MD *tls12_get_hash(uint8_t hash_alg) {
switch (hash_alg) {
case TLSEXT_hash_md5:
return EVP_md5();
case TLSEXT_hash_sha1:
return EVP_sha1();
case TLSEXT_hash_sha224:
return EVP_sha224();
case TLSEXT_hash_sha256:
return EVP_sha256();
@ -2697,7 +2690,7 @@ const EVP_MD *tls1_choose_signing_digest(SSL *ssl) {
size_t i, j;
static const int kDefaultDigestList[] = {NID_sha256, NID_sha384, NID_sha512,
NID_sha224, NID_sha1};
NID_sha1};
const int *digest_nids = kDefaultDigestList;
size_t num_digest_nids =

1
ssl/test/runner/runner.go
View File

@ -4109,7 +4109,6 @@ var testHashes = []struct {
id uint8
}{
{"SHA1", hashSHA1},
{"SHA224", hashSHA224},
{"SHA256", hashSHA256},
{"SHA384", hashSHA384},
{"SHA512", hashSHA512},