+ # check the file has only one clear-signed section
+ my $fh;
+ unless (open $fh, "<", $file) {
+ msg("log,mail", "Could not open $file\n");
+ return "";
+ }
+ unless (<$fh> eq "-----BEGIN PGP SIGNED MESSAGE-----\n") {
+ msg("log,mail", "$file: does not start with a clearsigned message\n");
+ return "";
+ }
+ my $pgplines = 1;
+ while (<$fh>) {
+ if (/\A- /) {
+ msg("log,mail", "$file: dash-escaped messages are not accepted\n");
+ return "";
+ }
+ elsif ($_ eq "-----BEGIN PGP SIGNATURE-----\n"
+ || $_ eq "-----END PGP SIGNATURE-----\n") {
+ $pgplines++;
+ }
+ elsif (/\A--/) {
+ msg("log,mail", "$file: unexpected OpenPGP armor\n");
+ return "";
+ }
+ elsif ($pgplines > 3 && /\S/) {
+ msg("log,mail", "$file: found text after end of signature\n");
+ return "";
+ }
+ }
+ if ($pgplines != 3) {
+ msg("log,mail", "$file: doesn't seem to be a valid clearsigned OpenPGP message\n");
+ return "";
+ }
+ close $fh;
+