📁 //snap/core20/2866/sbin/pam-auth-update
#!/usr/bin/perl -w
# pam-auth-update: update /etc/pam.d/common-* from /usr/share/pam-configs
#
# Update the /etc/pam.d/common-* files based on the per-package profiles
# provided in /usr/share/pam-configs/ taking into consideration user's
# preferences (as determined via debconf prompting).
#
# Written by Steve Langasek <steve.langasek@canonical.com>
#
# Copyright (C) 2008 Canonical Ltd.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of version 3 of the GNU General Public License as
# published by the Free Software Foundation.
#
# # This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301,
# USA.
use strict;
use Debconf::Client::ConfModule ':all';
use IPC::Open2 'open2';
version('2.0');
my $capb=capb('backup escape');
my $inputdir = '/usr/share/pam-configs';
my $template = 'libpam-runtime/profiles';
my $errtemplate = 'libpam-runtime/conflicts';
my $overridetemplate = 'libpam-runtime/override';
my $blanktemplate = 'libpam-runtime/no_profiles_chosen';
my $titletemplate = 'libpam-runtime/title';
my $confdir = '/etc/pam.d';
my $savedir = '/var/lib/pam';
my (%profiles, @sorted, @enabled, @conflicts, @new, %removals, %to_enable);
my $force = 0;
my $package = 0;
my $priority = 'high';
my %md5sums = (
'auth' => ['8d4fe17e66ba25de16a117035d1396aa'],
'account' => ['3c0c362eaf3421848b679d63fd48c3fa'],
'password' => [
'50fce2113dfda83ac8bdd5a6e706caec',
'4bd7610f2e85f8ddaef79c7db7cb49eb',
'9ba753d0824276b44bcadfee1f87b6bc',
],
'session' => [
'240fb92986c885b327cdb21dd641da8c',
'4a25673e8b36f1805219027d3be02cd2',
'73144a2f4e609a922a51e301cd66a57e',
],
'session-noninteractive' => [
'ad2b78ce1498dd637ef36469430b6ac6',
'a20e8df3469bfe25c13a3b39161b30f0',
],
);
opendir(DIR, $inputdir) || die "could not open config directory: $!";
while (my $profile = readdir(DIR)) {
next if ($profile eq '.' || $profile eq '..' || $profile =~ m/~$/ || $profile =~ m/^#.+#$/);
%{$profiles{$profile}} = parse_pam_profile($inputdir . '/' . $profile);
}
closedir DIR;
# use a '--force' arg to specify that /etc/pam.d should be overwritten;
# used only on upgrades where the postinst has already determined that the
# checksums match. Module packages other than libpam-runtime itself must
# NEVER use this option! Document with big skullses and crossboneses! It
# needs to be exposed for libpam-runtime because that's the package that
# decides whether we have a pristine config to be converted, and knows
# whether the version being upgraded from is one for which the conversion
# should be done.
while ($#ARGV >= 0) {
my $opt = shift;
if ($opt eq '--force') {
$force = 1;
} elsif ($opt eq '--package') {
$package = 1;
} elsif ($opt eq '--remove') {
while ($#ARGV >= 0) {
last if ($ARGV[0] =~ /^--/);
$removals{shift @ARGV} = 1;
}
# --remove implies --package
$package = 1 if (keys(%removals));
} elsif ($opt eq '--enable') {
while ($#ARGV >= 0) {
last if ($ARGV[0] =~ /^--/);
$to_enable{shift @ARGV} = 1;
}
# --enable implies --package
$package = 1 if (keys(%to_enable));
}
}
$priority = 'medium' if ($package);
x_loadtemplatefile('/var/lib/dpkg/info/libpam-runtime.templates','libpam-runtime');
# always sort by priority, so we have consistency and don't have to
# shuffle later
@sorted = sort { $profiles{$b}->{'Priority'} <=> $profiles{$a}->{'Priority'}
|| $b cmp $a }
keys(%profiles);
# If we're being called for package removal, filter out those options here
@sorted = grep { !$removals{$_} } @sorted;
subst($template, 'profile_names', join(', ',@sorted));
subst($template, 'profiles',
join(', ', map { $profiles{$_}->{'Name'} } @sorted));
my $diff = diff_profiles($confdir,$savedir);
if ($diff) {
@enabled = grep { !$removals{$_} } @{$diff->{'mods'}};
} else {
@enabled = split(/, /,get($template));
}
# find out what we've seen, so we can ignore those defaults
my %seen;
if (-e $savedir . '/seen') {
open(SEEN,$savedir . '/seen') or die("open(${savedir}/seen) failed: $!");
while (<SEEN>) {
chomp;
$seen{$_} = 1;
}
close(SEEN);
}
# filter out any options that are no longer available for any reason
@enabled = grep { $profiles{$_} } @enabled;
# an empty module set is an error, so in that case grab all the defaults
if (!@enabled) {
%seen = ();
$priority = 'high' unless ($force);
}
# add configs to enable
push(@enabled,
grep { $to_enable{$_} } @sorted);
# add any previously-unseen configs
push(@enabled,
grep { $profiles{$_}->{'Default'} eq 'yes' && !$seen{$_} } @sorted);
@enabled = sort { $profiles{$b}->{'Priority'} <=> $profiles{$a}->{'Priority'}
|| $b cmp $a }
@enabled;
my $prev = '';
@enabled = grep { $_ ne $prev && (($prev) = $_) } @enabled;
# Do we have any new options to show? If not, we shouldn't reprompt the
# user, at any priority level, unless explicitly called.
@new = grep { !$seen{$_} } @sorted;
settitle($titletemplate);
# if diff_profiles() fails, and we weren't passed a 'force' argument
# (because this isn't an upgrade from an old version, or the checksum
# didn't match, or we're being called by some other module package), prompt
# the user whether to override. If the user declines (the default), we
# never again manage this config unless manually called with '--force'.
if (!$diff && !$force) {
input('high',$overridetemplate);
go();
$force = 1 if (get($overridetemplate) eq 'true');
}
if (!$diff && !$force) {
print STDERR <<EOF;
pam-auth-update: Local modifications to /etc/pam.d/common-*, not updating.
pam-auth-update: Run pam-auth-update --force to override.
EOF
exit;
}
umask(0022);
do {
@conflicts = ();
if (@new || !$package) {
fset($template,'seen','false');
}
set($template,join(', ', @enabled));
input($priority,$template);
go();
@enabled = split(/, /, get($template));
# in case of conflicts, automatically unset the lower priority
# item of each pair
foreach my $elem (@enabled)
{
for (my $i=$#enabled; $i >= 0; $i--)
{
my $conflict = $enabled[$i];
if ($profiles{$elem}->{'Conflicts'}->{$conflict}) {
splice(@enabled,$i,1);
my $desc = $profiles{$elem}->{'Name'}
. ', ' . $profiles{$conflict}->{'Name'};
push(@conflicts,$desc);
}
}
}
if (@conflicts) {
subst($errtemplate, 'conflicts', join("\\n", @conflicts));
input('high',$errtemplate);
}
set($template, join(', ', @enabled));
if (!@enabled) {
input('high',$blanktemplate);
# we can only end up here by user error, but give them another
# shot at selecting a correct config anyway.
fset($template,'seen','false');
}
} while (@conflicts || !@enabled);
# the decision has been made about what configs to use, so even if
# something fails after this, we shouldn't go munging the default
# options again. Save the list of known configs to /var/lib/pam.
open(SEEN,"> $savedir/seen") or die("open(${savedir}/seen) failed: $!");
for my $i (@sorted) {
print SEEN "$i\n";
}
close(SEEN) or die("close(${savedir}/seen) failed: $!");
# @enabled now contains our list of profiles to use for piecing together
# a config
# we have:
# - templates into which we insert the specialness
# - magic comments denoting the beginning and end of our managed block;
# looking at only the functional config lines would potentially let us
# handle more cases, at the expense of much greater complexity, so
# pass on this at least for the first round
# - a representation of the autogenerated config stored in /var/lib/pam,
# that we can diff against in order to account for changed options or
# manually dropped modules
# - a hash describing the local modifications the user has made to the
# config; these are always preserved unless manually overridden with
# the --force option
write_profiles(\%profiles, \@enabled, $confdir, $savedir, $diff, $force);
# take a single line from a stock config, and merge it with the
# information about local admin edits
sub merge_one_line
{
my ($line,$diff,$count) = @_;
my (@opts,$modline);
my ($adds,$removes);
$line =~ /^((\[[^]]+\]|\w+)\s+\S+)\s*(.*)/;
@opts = split(/\s+/,$3);
$modline = $1;
$modline =~ s/end/$count/g;
if ($diff) {
my $mod = $modline;
$mod =~ s/(\[[^0-9]*)[0-9]+(.*\])/$1$2/g;
$adds = \%{$diff->{'add'}{$mod}};
$removes = \%{$diff->{'remove'}{$mod}};
} else {
$adds = $removes = undef;
}
for (my $i = 0; $i <= $#opts; $i++) {
if ($adds->{$opts[$i]}) {
delete $adds->{$opts[$i]};
}
if ($removes->{$opts[$i]}) {
splice(@opts,$i,1);
$i--;
}
}
return $modline . " " . join(' ',@opts,sort keys(%{$adds})) . "\n";
}
# return the lines for a given config name, type, and position in the stack
sub lines_for_module_and_type
{
my ($profiles, $mod, $type, $modpos) = @_;
if ($modpos == 0 && $profiles->{$mod}{$type . '-Initial'}) {
return $profiles->{$mod}{$type . '-Initial'};
}
return $profiles->{$mod}{$type};
}
# create a single PAM config from the indicated template and selections,
# writing to a new file
sub create_from_template
{
my($template,$dest,$profiles,$enabled,$diff,$type) = @_;
my $state = 0;
my $uctype = ucfirst($type);
$type =~ s/-noninteractive//;
open(INPUT,$template) || return 0;
open(OUTPUT,">$dest") || return 0;
while (<INPUT>) {
if ($state == 1) {
if (/^# here's the fallback if no module succeeds/) {
print OUTPUT;
$state++;
}
next;
}
if ($state == 3) {
if (/^# end of pam-auth-update config/) {
print OUTPUT;
$state++;
}
next;
}
print OUTPUT;
my ($pattern,$val);
if ($state == 0) {
$pattern = '^# here are the per-package modules \(the "Primary" block\)';
$val = 'Primary';
} elsif ($state == 2) {
$pattern = '^# and here are more per-package modules \(the "Additional" block\)';
$val = 'Additional';
} else {
next;
}
if (/$pattern/) {
my $i = 0;
my $count = 0;
# first we need to get a count of lines that we're
# going to output, so we can fix up the jumps correctly
for my $mod (@{$enabled}) {
my $output;
next if (!$profiles->{$mod}{$uctype . '-Type'});
next if $profiles->{$mod}{$uctype . '-Type'} ne $val;
$output = lines_for_module_and_type($profiles, $mod, $uctype, $i++);
# bypasses a perl warning about @_, sigh
my @tmparr = split("\n+",$output);
$count += @tmparr;
}
# in case anything tries to jump in the 'additional'
# block, let's try not to jump off the stack...
$count-- if ($val eq 'Additional');
# no primary block, so output a stock pam_permit line
# to keep the stack intact
if ($val eq 'Primary' && $count == 0)
{
print OUTPUT "$type\t[default=1]\t\t\tpam_permit.so\n";
}
$i = 0;
for my $mod (@{$enabled}) {
my $output;
my @output;
next if (!$profiles->{$mod}{$uctype . '-Type'});
next if $profiles->{$mod}{$uctype . '-Type'} ne $val;
$output = lines_for_module_and_type($profiles, $mod, $uctype, $i++);
for my $line (split("\n",$output)) {
$line = merge_one_line($line,$diff,
$count);
print OUTPUT "$type\t$line";
$count--;
}
}
$state++;
}
}
close(INPUT);
close(OUTPUT) or die("close($dest) failed: $!");
if ($state < 4) {
unlink($dest);
return 0;
}
return 1;
}
# take a template file, strip out everything between the markers, and
# return the md5sum of the remaining contents. Used for testing for
# local modifications of the boilerplate.
sub get_template_md5sum
{
my($template) = @_;
my $state = 0;
open(INPUT,$template) || return '';
my($md5sum_fd,$output_fd);
my $pid = open2($md5sum_fd, $output_fd, 'md5sum');
return '' if (!$pid);
while (<INPUT>) {
if ($state == 1) {
if (/^# here's the fallback if no module succeeds/) {
print $output_fd $_;
$state++;
}
next;
}
if ($state == 3) {
if (/^# end of pam-auth-update config/) {
print $output_fd $_;
$state++;
}
next;
}
print $output_fd $_;
my ($pattern,$val);
if ($state == 0) {
$pattern = '^# here are the per-package modules \(the "Primary" block\)';
} elsif ($state == 2) {
$pattern = '^# and here are more per-package modules \(the "Additional" block\)';
} else {
next;
}
if (/$pattern/) {
$state++;
}
}
close(INPUT);
close($output_fd);
my $md5sum = <$md5sum_fd>;
close($md5sum_fd);
waitpid $pid, 0;
$md5sum = (split(/\s+/,$md5sum))[0];
return $md5sum;
}
# merge a set of module declarations into a set of new config files,
# using the information returned from diff_profiles().
sub write_profiles
{
my($profiles,$enabled,$confdir,$savedir,$diff,$force) = @_;
if (! -d $savedir) {
mkdir($savedir);
}
# because we can't atomically replace both /var/lib/pam/$foo and
# /etc/pam.d/common-$foo at the same time, take steps to make this
# somewhat robust
for my $type ('auth','account','password','session',
'session-noninteractive')
{
my $target = $confdir . '/common-' . $type;
my $template = $target;
my $dest = $template . '.pam-new';
my $diff = $diff;
if ($diff) {
$diff = \%{$diff->{$type}};
}
# Detect if the template is unmodified, and if so, use
# the version from /usr/share. Depends on knowing the
# md5sums of the originals.
my $md5sum = get_template_md5sum($template);
for my $i (@{$md5sums{$type}}) {
if ($md5sum eq $i) {
$template = '/usr/share/pam/common-' . $type;
last;
}
}
# first, write out the new config
if (!create_from_template($template,$dest,$profiles,$enabled,
$diff,$type))
{
if (!$force) {
return 0;
}
$template = '/usr/share/pam/common-' . $type;
if (!create_from_template($template,$dest,$profiles,
$enabled,$diff,$type))
{
return 0;
}
}
# then write out the saved config
if (!open(OUTPUT, "> $savedir/$type.new")) {
unlink($dest);
return 0;
}
my $i = 0;
my $uctype = ucfirst($type);
for my $mod (@{$enabled}) {
my $output;
next if (!$profiles->{$mod}{$uctype . '-Type'});
next if ($profiles->{$mod}{$uctype . '-Type'} eq 'Additional');
$output = lines_for_module_and_type($profiles, $mod, $uctype, $i++);
if ($output) {
print OUTPUT "Module: $mod\n";
print OUTPUT $output . "\n";
}
}
# no primary block, so output a stock pam_permit line
if ($i == 0)
{
print OUTPUT "Module: null\n";
print OUTPUT "[default=1]\t\t\tpam_permit.so\n";
}
$i = 0;
for my $mod (@{$enabled}) {
my $output;
next if (!$profiles->{$mod}{$uctype . '-Type'});
next if ($profiles->{$mod}{$uctype . '-Type'} eq 'Primary');
$output = lines_for_module_and_type($profiles, $mod, $uctype, $i++);
if ($output) {
print OUTPUT "Module: $mod\n";
print OUTPUT $output . "\n";
}
}
close(OUTPUT) or die("close($dest) failed: $!");
# then do the renames, back-to-back
# we have to use system because File::Copy is in
# perl-modules, not perl-base
if (-e $target && $force) {
system('cp','-f',$target,$target . '.pam-old') == 0
or die("cp -f ${target} ${target}.pam.old failed");
}
rename($dest,$target)
or die("rename($dest, $target) failed: $!");
rename("$savedir/${type}.new","$savedir/$type")
or die("rename(${savedir}/${type}.new, ${savedir}/${type}) failed: $!");
}
# at the end of a successful write, reset the 'seen' flag and the
# value of the debconf override question.
fset($overridetemplate,'seen','false');
set($overridetemplate,'false');
}
# reconcile the current config in /etc/pam.d with the saved ones in
# /var/lib/pam; returns a hash of profile names and the corresponding
# options that should be added/removed relative to the stock config.
# returns false if any of the markers are missing that permit a merge,
# or on any other failure.
sub diff_profiles
{
my ($sourcedir,$savedir) = @_;
my (%diff);
@{$diff{'mods'}} = ();
# Load the saved config from /var/lib/pam, then iterate through all
# lines in the current config that are in the managed block.
# If anything fails here, just return immediately since we then
# have nothing to merge; instead, the caller will decide later
# whether to force an overwrite.
for my $type ('auth','account','password','session',
'session-noninteractive')
{
my (@saved,$modname);
open(SAVED,$savedir . '/' . $type) || return 0;
while (<SAVED>) {
if (/^Module: (.*)/) {
$modname = $1;
next;
}
chomp;
# trim out the destination of any jumps; this saves
# us from having to re-parse everything just to fix
# up the jump lengths, when changes to these will
# already show up as inconsistencies elsewhere
s/(\[[^0-9]*)[0-9]+(.*\])/$1$2/g;
s/(\[.*)end(.*\])/$1$2/g;
my (@temp) = ($modname,$_);
push(@saved,\@temp);
}
close(SAVED);
my $state = 0;
my (@prev_opts,$curmod);
my $realtype = $type;
$realtype =~ s/-noninteractive//;
open(CURRENT,$sourcedir . '/common-' . $type) || return 0;
while (<CURRENT>) {
if ($state == 0) {
$state = 1
if (/^# here are the per-package modules \(the "Primary" block\)/);
next;
}
if ($state == 1) {
s/^$realtype\s+//;
if (/^# here's the fallback if no module succeeds/) {
$state = 2;
next;
}
}
if ($state == 2) {
$state = 3
if (/^# and here are more per-package modules \(the "Additional" block\)/);
next;
}
if ($state == 3) {
last if (/^# end of pam-auth-update config/);
s/^$realtype\s+//;
}
my $found = 0;
my $curopts;
while (!$found && $#saved >= 0) {
my $line;
($modname,$line) = @{$saved[0]};
shift(@saved);
$line =~ /^((\[[^]]+\]|\w+)\s+\S+)\s*(.*)/;
@prev_opts = split(/\s+/,$3);
$curmod = $1;
# FIXME: the key isn't derived from the config
# name, so collisions are possible if more
# than one config references the same module
$_ =~ s/(\[[^0-9]*)[0-9]+(.*\])/$1$2/g;
# check if this is a match for the current line
if ($_ =~ /^\Q$curmod\E\s*(.*)$/) {
$found = 1;
$curopts = $1;
push(@{$diff{'mods'}},$modname);
}
}
# there's a line in the live config that doesn't
# correspond to anything from the saved config.
# treat this as a failure; it's very error-prone
# to decide what to do with an added line that
# didn't come from a package.
return 0 if (!$found);
for my $opt (split(/\s+/,$curopts)) {
my $found = 0;
for (my $i = 0; $i <= $#prev_opts; $i++) {
if ($prev_opts[$i] eq $opt) {
$found = 1;
splice(@prev_opts,$i,1);
}
}
$diff{$type}{'add'}{$curmod}{$opt} = 1 if (!$found);
}
for my $opt (@prev_opts) {
$diff{$type}{'remove'}{$curmod}{$opt} = 1;
}
}
close(CURRENT);
# we couldn't parse the config, so the merge fails
return 0 if ($state < 3);
}
return \%diff;
}
# simple function to parse a provided config file, in pseudo-RFC822
# format,
sub parse_pam_profile
{
my ($profile) = $_[0];
my $fieldname;
my %profile;
open(PROFILE, $profile) || die "could not read profile $profile: $!";
while (<PROFILE>) {
if (/^(\S+):\s+(.*)\s*$/) {
$fieldname = $1;
# compatibility with the first implementation round;
# "Auth-Final" is now just called "Auth"
$fieldname =~ s/-Final$//;
if ($fieldname eq 'Conflicts') {
foreach my $elem (split(/, /, $2)) {
$profile{'Conflicts'}->{$elem} = 1;
}
} else {
$profile{$fieldname} = $2;
}
} else {
chomp;
s/^\s+//;
s/\s+$//;
$profile{$fieldname} .= "\n$_" if ($_);
$profile{$fieldname} =~ s/^[\n\s]+//;
}
}
close(PROFILE);
if (!defined($profile{'Session-Interactive-Only'})) {
$profile{'Session-noninteractive-Type'} = $profile{'Session-Type'};
$profile{'Session-noninteractive'} = $profile{'Session'};
$profile{'Session-noninteractive-Initial'} = $profile{'Session-Initial'};
}
return %profile;
}