Messages in this thread | | | Date | Tue, 28 Jun 2022 11:15:53 +0800 | Subject | Re: [PATCH v2 RESEND] KEYS: asymmetric: enforce SM2 signature use pkey algo | From | Tianjia Zhang <> |
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Hi Jarkko,
On 6/28/22 7:14 AM, Jarkko Sakkinen wrote: > On Mon, Jun 27, 2022 at 05:20:27PM +0800, Tianjia Zhang wrote: >> The signature verification of SM2 needs to add the Za value and >> recalculate sig->digest, which requires the detection of the pkey_algo >> in public_key_verify_signature(). As Eric Biggers said, the pkey_algo >> field in sig is attacker-controlled and should be use pkey->pkey_algo >> instead of sig->pkey_algo, and secondly, if sig->pkey_algo is NULL, it >> will also cause signature verification failure. >> >> The software_key_determine_akcipher() already forces the algorithms >> are matched, so the SM3 algorithm is enforced in the SM2 signature, >> although this has been checked, we still avoid using any algorithm >> information in the signature as input. >> >> Fixes: 215525639631 ("X.509: support OSCCA SM2-with-SM3 certificate verification") >> Reported-by: Eric Biggers <ebiggers@google.com> >> Cc: stable@vger.kernel.org # v5.10+ >> Signed-off-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com> >> --- >> crypto/asymmetric_keys/public_key.c | 6 +++--- >> 1 file changed, 3 insertions(+), 3 deletions(-) >> >> diff --git a/crypto/asymmetric_keys/public_key.c b/crypto/asymmetric_keys/public_key.c >> index 7c9e6be35c30..3f17ee860f89 100644 >> --- a/crypto/asymmetric_keys/public_key.c >> +++ b/crypto/asymmetric_keys/public_key.c >> @@ -309,7 +309,8 @@ static int cert_sig_digest_update(const struct public_key_signature *sig, >> if (ret) >> return ret; >> >> - tfm = crypto_alloc_shash(sig->hash_algo, 0, 0); >> + /* SM2 signatures always use the SM3 hash algorithm */ >> + tfm = crypto_alloc_shash("sm3", 0, 0); > > So, why this should not validate sig->hash_alog *to be* "sm3"? > > I.e. add instead guard before crypto_alloc_hash: > > if (strncmp(sig->hash_algo, "sm3") != 0) { > /* error */ > } > /* continue */ >
Thanks, it's reasonable and I'll take your advice.
Best regards, Tianjia
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