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crypto: rsa-pkcs1pad - restore signature length check

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RSA PKCS#1 v1.5 signatures are required to be the same length as the RSA
key size.  RFC8017 specifically requires the verifier to check this
(https://datatracker.ietf.org/doc/html/rfc8017#section-8.2.2).

Commit a49de377e0 ("crypto: Add hash param to pkcs1pad") changed the
kernel to allow longer signatures, but didn't explain this part of the
change; it seems to be unrelated to the rest of the commit.

Revert this change, since it doesn't appear to be correct.

We can be pretty sure that no one is relying on overly-long signatures
(which would have to be front-padded with zeroes) being supported, given
that they would have been broken since commit c7381b0128
("crypto: akcipher - new verify API for public key algorithms").

Fixes: a49de377e0 ("crypto: Add hash param to pkcs1pad")
Cc: <stable@vger.kernel.org> # v4.6+
Cc: Tadeusz Struk <tadeusz.struk@linaro.org>
Suggested-by: Vitaly Chikunov <vt@altlinux.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Eric Biggers 2022-01-18 16:13:04 -08:00 committed by Herbert Xu
parent e316f7179b
commit d3481accd9
1 changed files with 1 additions and 1 deletions
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2
crypto/rsa-pkcs1pad.c
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@ -538,7 +538,7 @@ static int pkcs1pad_verify(struct akcipher_request *req)
if (WARN_ON(req->dst) ||
WARN_ON(!req->dst_len) ||
!ctx->key_size || req->src_len < ctx->key_size)
!ctx->key_size || req->src_len != ctx->key_size)
return -EINVAL;
req_ctx->out_buf = kmalloc(ctx->key_size + req->dst_len, GFP_KERNEL);