Badly formed messages that don't specify a protocol in
signed/encrypted parts, end up with a protocol of NULL. strcasecmp in
notmuch_crypto_get_context then segfaults when trying to check it
against known protocols. If the protocol is NULL, just return an
empty context immediately (with appropriate message.)
{
notmuch_crypto_context_t *cryptoctx = NULL;
+ if (! protocol) {
+ fprintf (stderr, "Cryptographic protocol is empty.\n");
+ return cryptoctx;
+ }
+
/* As per RFC 1847 section 2.1: "the [protocol] value token is
* comprised of the type and sub-type tokens of the Content-Type".
* As per RFC 1521 section 2: "Content-Type values, subtypes, and