#!/usr/local/bin/perl
# -*- Perl -*-

# written by jason steiner, jsteiner@anwsun.phya.utoledo.edu, Jan 1993
#
# if you use or make improvements to this program i would appreciate
# copies of your modifications & your PGP public key.
#

# Modified by Greg Spencer, greg@graphics.cornell.edu, May 1994
# Mostly just cleaned up things and added stuff like automatic
# addition and detection (and ignoring) of keys to be added to keyring,
# and signal catching, as well as environment variable control of
# most site-specific stuff.
# 
# Must set the following environment variable:
# 
# PGPCOMMAND set to the pgp decryption command
# 
# PAGER set to the desired pager command
#
# NOTE that this program NEVER writes sensitive data to a disk file.
# it will only slurp it into memory, so if you have a HUGE file, you might
# have problems.

# setup some variables
($pgpcommand = $ENV{'PGPCOMMAND'}) || ($pgpcommand = "/usr/local/bin/pgp");

# just used for tmpfile names...
($logname = $ENV{'LOGNAME'}) || ($logname = "nobody");

($pager = $ENV{'PAGER'}) || ($pager="/usr/local/bin/less -i -n -s -S -c -M");

$|=1;
$topgp = 0;
$tokey = 0;
$pgpused = 0;
($tmpdir = $ENV{'TMPDIR'}) || ($tmpdir = "/tmp");

#temporary file name
$tmpfile  = "${tmpdir}/.pgp1.$logname.$$";
$tmpfile2 = "${tmpdir}/.pgp2.$logname.$$";

# trap signals so we do not leave
# garbage around
sub catcher {
	local ($sig) = @_;

	print "Caught a SIG$sig -- exiting\n";
	close (TMPFILE);
	close (OUTPUT);
	close (PAGER);
	unlink ($tmpfile);
	unlink ($tmpfile2);
}

$SIG{'INT'}  = 'catcher';
$SIG{'QUIT'} = 'catcher';
$SIG{'HUP'}  = 'catcher';
$SIG{'KILL'} = 'catcher';

# make sure nobody can read stuff
umask 077;

# prepare a data area
@tmpdata = ();
@newkeys = ();

while (<>) {
	if (!$topgp && m/^-----BEGIN PGP .*-----/ && !m/^-----BEGIN PGP PUBLIC KEY BLOCK-----/) {
		$topgp = 1;
		$pgpused = 1;
		unlink ($tmpfile);
		open (TMPFILE, ">$tmpfile") || (unlink ($tmpfile) && die "Cannot open $tmpfile for output.\n");
	}
	if (!$topgp) {
		push(@tmpdata, $_);
	} 
	if ((!$tokey) && (m/^-----BEGIN PGP PUBLIC KEY BLOCK-----/)) {
		$contains_keys = 1;
		$tokey = 1;
	}
	if ($tokey) {
		push (@newkeys, $_);
		if (m/^-----END PGP PUBLIC KEY BLOCK-----/) {
			$tokey = 0;
		}
	}
	if ($topgp) {
		print TMPFILE $_; # OK to write this to a file -- it is encrypted!
		if (m/^-----END PGP .*-----/ && !m/^-----END PGP PUBLIC KEY BLOCK-----/) {
			$topgp = 0;
			close TMPFILE;
			open (CLEAR, "$pgpcommand -f < $tmpfile |") || 
			(unlink($tmpfile) && die "Cannot open pipe to PGP.\n");
			$blocktype = $_;
			$blocktype =~s/^-----END (PGP .*)-----/$1/;
			$blocktype =~s/PGP MESSAGE/DECRYPTED MESSAGE/;
			$blocktype =~s/PGP SIGNATURE/SIGNED MESSAGE/;
			chop ($blocktype);
			push (@tmpdata, "-----BEGIN $blocktype-----\n");
			while (<CLEAR>) {
				push (@tmpdata, $_);
				if ((!$tokey) && (m/^-----BEGIN PGP PUBLIC KEY BLOCK-----/)) {
					$contains_keys = 1;
					$tokey = 1;
				}
				if ($tokey) {
					push (@newkeys, $_);
					if (m/^-----END PGP PUBLIC KEY BLOCK-----/) {
						$tokey = 0;
					}
				}
			}
			close CLEAR;
			print STDERR "\n";
			unlink ($tmpfile);
			push (@tmpdata, "-----END $blocktype-----\n");
		}
	}
}

select (STDIN);  $|=1;
select (STDERR); $|=1;
select (STDOUT); $|=1;

# This handles things if we found keys that need
# adding to our keyring
# note that we are only writing the KEYS to the file.
if ($contains_keys) { 
	print STDERR "PGP Keys found, attempting to add...\n";

	open (TMPFILE2, ">$tmpfile2");
	foreach $_ (@newkeys) {
		print TMPFILE2;
	}
	close (TMPFILE2);

	# strange things happen if we do not 
	# read/write directly from /dev/tty (perl bug??)
	system ("$pgpcommand -ka $tmpfile2 >/dev/tty </dev/tty 2>&1");
	unlink ($tmpfile2);	# get rid of it asap
	$pgpused = 1;
}

# do "press any key to continue"
# only if we had some output from PGP
# (like a verified signature)
# again with the /dev/tty thing (weird!)
if ($pgpused) {
	$q='';
	open (TTY, "</dev/tty")	|| (unlink ($tmpfile1) && die "Couldn't open /dev/tty\n");
	select(TTY); $| = 1;
	print STDERR "\n\nPress any key to continue...\n";
	$q = getc (TTY);
	select (STDIN);
}

# copy the contents of @tmpdata to the pager we want to use.
open (PAGER, "|$pager") || (unlink ($tmpfile1) && die "Cannot open pipe to $pager.\n");

# output the decoded thing to the pager
foreach $_ (@tmpdata) {
	print PAGER;
}
@tmpdata = ();

close OUTPUT;
close PAGER;

# cleanup
unlink ($tmpfile);