[PATCH v2 1/1] digsig: add hash size comparision on signature verification

[Dmitry Kasatkin]

Commit b35e286a640f31d619a637332972498b51f3fd90 introduced the bug.

When pkcs_1_v1_5_decode_emsa() returns without error and hash sizes do not
match, hash comparision is not done and digsig_verify_rsa() returns no error.
This is a bug and this patch fixes it.

Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin@xxxxxxxxx>
---
 lib/digsig.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/lib/digsig.c b/lib/digsig.c
index 286d558..8c0e629 100644
--- a/lib/digsig.c
+++ b/lib/digsig.c
@@ -163,9 +163,11 @@ static int digsig_verify_rsa(struct key *key,
 	memcpy(out1 + head, p, l);
 
 	err = pkcs_1_v1_5_decode_emsa(out1, len, mblen, out2, &len);
+	if (err)
+		goto err;
 
-	if (!err && len == hlen)
-		err = memcmp(out2, h, hlen);
+	if (len != hlen || memcmp(out2, h, hlen))
+		err = -EINVAL;
 
 err:
 	mpi_free(in);
-- 
1.7.9.5

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