From: Eric Biggers ebiggers@google.com
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 a49de377e051 ("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 c7381b012872 ("crypto: akcipher - new verify API for public key algorithms").
Fixes: a49de377e051 ("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 --- crypto/rsa-pkcs1pad.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/crypto/rsa-pkcs1pad.c b/crypto/rsa-pkcs1pad.c index 7b223adebabf6..6b556ddeb3a00 100644 --- a/crypto/rsa-pkcs1pad.c +++ b/crypto/rsa-pkcs1pad.c @@ -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);