pki: Sanity-check signature matches base key type

Signed-off-by: Jakub Jelen <jjelen@redhat.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
(cherry picked from commit c79c33e224)

src/pki.c

@@ -1928,6 +1928,12 @@ int ssh_pki_signature_verify(ssh_session session,
             "Going to verify a %s type signature",
             sig->type_c);
 
+    if (key->type != sig->type) {
+        SSH_LOG(SSH_LOG_WARN,
+                "Can not verify %s signature with %s key",
+                sig->type_c, key->type_c);
+        return SSH_ERROR;
+    }
 
     if (key->type == SSH_KEYTYPE_ECDSA) {
 #if HAVE_ECC