#!/bin/sh
# mverify MSG - verify a OpenPGP or SMIME message

# Needs bash, unix2dos, gpg and openssl.

[ "$#" -eq 0 ] && set -- .

mshow -t "$1" | awk -v "msg=$1" '
{ match($0, "^ *"); indent = RLENGTH }
$2 == "text/plain" { plain++ }
$2 == "multipart/signed" { signed = +$1; si = indent; next }
signed && !content && indent == si+2 { content = +$1; next }
signed && content && !signature && indent == si+2 { signature = +$1; type = $2 }
function q(a) { gsub("\\47", "\47\\\47\47", a); return "\47"a"\47" }
END {
	if (type == "" && plain) {  // guess plain text armored signature
		exit(system("mshow -R " q(msg) " | gpg --verify"));
	} else if (type == "") {
		print("No signature found.")
		exit(100)
	} else if (type == "application/pgp-signature") {
		exit(system("bash -c " q("mshow -r -O " q(msg) " " q(content) \
			" | unix2dos | gpg --verify <(mshow -O " q(msg) \
			" " q(signature) " ) -")))
	} else if (type == "application/pkcs7-signature") {
		exit(system("mshow -r -O " q(msg) " " q(signed) \
			" | openssl smime -verify"))
	} else {
		print("Cant verify signatures of type " type ".")
		exit(2)
	}
}
'