Revert "ikiwiki-mass-rebuild: Fix tty hijacking vulnerability by using su.

[git.ikiwiki.info.git] / ikiwiki-mass-rebuild

diff --git a/ikiwiki-mass-rebuild b/ikiwiki-mass-rebuild
index bbef4946bb5b76d4aa6f5a291b253ada42309529..f13033e7f821d7cbae3a7c761147aa27dedf2b45 100755 (executable)
--- a/ikiwiki-mass-rebuild
+++ b/ikiwiki-mass-rebuild
@@ -2,45 +2,80 @@
 use warnings;
 use strict;
 
-my $etcfile="/etc/ikiwiki/wikilist";
+sub supplemental_groups {
+       my $user=shift;
+
+       my @list;
+       while (my @fields=getgrent()) {
+               if (grep { $_ eq $user } split(' ', $fields[3])) {
+                       push @list, $fields[2];
+               }
+       }
 
-sub root {
-       $> == 0;
+       return @list;
 }
 
-sub username {
-       (getpwuid($>))[0];
+sub samelists {
+       my %a=map { $_ => 1 } split(' ', shift());
+       my %b=map { $_ => 1 } split(' ', shift());
+
+       foreach my $i (keys %b) {
+               if (! exists $a{$i}) {
+                       return 0;
+               }
+       }
+       foreach my $i (keys %a) {
+               if (! exists $b{$i}) {
+                       return 0;
+               }
+       }
+       return 1;
 }
 
 sub processline {
+       my $user=shift;
        my $setup=shift;
        
+       if (! getpwnam("$user")) {
+               print STDERR "warning: user $user does not exist\n";
+               return
+       }
        if (! -f "$setup") {
                print STDERR "warning: $setup does not exist, skipping\n";
                return;
        }
-       print "Processing $setup as user ".username()." ...\n";
-       my $ret=system("ikiwiki", "-setup", $setup, @ARGV);
-       if ($ret != 0) {
-               print STDERR "warning: processing $setup failed with code $ret\n";
+       print "Processing $setup as user $user ...\n";
+       # su is not used because it passes arguments through the shell,
+       # which is not safe for untrusted setup file names.
+       defined(my $pid = fork) or die "Can’t fork: $!";
+       if (! $pid) {
+               my ($uuid, $ugid) = (getpwnam($user))[2, 3];
+               my $grouplist=join(" ", $ugid, sort {$a <=> $b} $ugid, supplemental_groups($user));
+               if (! samelists(($)=$grouplist), $grouplist)) {
+                       die "failed to set egid $grouplist (got back $))";
+               }
+               $(=$ugid;
+               $<=$uuid;
+               $>=$uuid;
+               if ($< != $uuid || $> != $uuid || $( != $ugid) {
+                       die "failed to drop permissions to $user";
+               }
+               %ENV=(
+                       PATH => $ENV{PATH},
+                       HOME => (getpwnam($user))[7],
+               );
+               exec("ikiwiki", "-setup", $setup, @ARGV);
+               die "failed to run ikiwiki: $!";
        }
-}
-
-my %users;
-sub processuser {
-       my $user=shift;
-       next if $user=~/^-/ || $users{$user};
-       $users{$user}=1;
-       my $ret=system("su", $user, "-s", "/bin/sh", "-c", "--", "$0 --nonglobal @ARGV");
-       if ($ret != 0) {
-               print STDERR "warning: processing for $user failed with code $ret\n";
+       waitpid($pid,0);
+       if ($?) {
+               print STDERR "Processing $setup as user $user failed with code $?\n";
        }
 }
 
 sub processlist {
        my $file=shift;
-
-       return unless -e $file;
+       my $forceuser=shift;
 
        my $list;
        open ($list, "<$file") || die "$file: $!";
@@ -49,28 +84,22 @@ sub processlist {
                s/^\s+//;
                s/\s+$//;
                next if /^#/ || ! length;
-               if (/^([-\w]+)\s+([^\s]+)$/) {
+
+               if (/^([^\s]+)\s+([^\s]+)$/) {
                        my $user=$1;
                        my $setup=$2;
-                       if (root()) {
-                               processuser($user);
-                       }
-                       else {
-                               if (username() eq $user) {
-                                       processline($setup);
-                               }
+                       if (defined $forceuser && $forceuser ne $user) {
+                               print STDERR "warning: in $file line $., attempt to set user to $user, but user forced to $forceuser. Skipping\n";
                        }
+                       processline($user, $setup);
                }
-               elsif (/^([-\w]+)$/) {
+               elsif (/^([^\s]+)$/) {
                        my $user=$1;
-                       if (root()) {
-                               processuser($user);
-                       }
-                       else {
-                               my $home=(getpwnam($user))[7];
-                               if (defined $home && -d $home) {
-                                       my $dotfile="$home/.ikiwiki/wikilist";
-                                       processlist($dotfile);
+                       my $home=(getpwnam($user))[7];
+                       if (defined $home && -d $home) {
+                               my $dotfile="$home/.ikiwiki/wikilist";
+                               if (-e $dotfile) {
+                                       processlist($dotfile, $user);
                                }
                        }
                }
@@ -78,13 +107,9 @@ sub processlist {
        close $list;
 }
 
-if (@ARGV && $ARGV[0] eq "--nonglobal") {
-       shift;
-       # avoid recursively processing if the wikilist file has a root
-       # user in it
-       if (root()) {
-               exit 1;
-       }
+my $wikilist="/etc/ikiwiki/wikilist";
+
+if (-e $wikilist) {
+       processlist($wikilist);
 }
 
-processlist($etcfile);