Honor a custom user and group specified for the entrypoint via the OCI image config `User` field instead of ignoring it.
User and group name lookups, including supplementary groups, are resolved from /etc/passwd and /etc/group in the container file system. This behaviour matches the OCI image spec. [0] [0] https://specs.opencontainers.org/image-spec/config/?v=v1.1.1#properties Signed-off-by: Filip Schauer <[email protected]> Tested-by: Maximiliano Sandoval <[email protected]> --- This requires the following patch for LXC in order to work properly: https://github.com/lxc/lxc/pull/4626 Changes since v1: * Move OCI User resolving code to separate sub * chomp $line before interpreting fields * Prevent rootfs escape when following /etc/passwd & /etc/group symlinks * Fix $username search in get_supplementary_groups src/PVE/LXC/Create.pm | 82 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 82 insertions(+) diff --git a/src/PVE/LXC/Create.pm b/src/PVE/LXC/Create.pm index 9956cf9..5ed1c29 100644 --- a/src/PVE/LXC/Create.pm +++ b/src/PVE/LXC/Create.pm @@ -3,6 +3,7 @@ package PVE::LXC::Create; use strict; use warnings; +use Cwd qw(abs_path); use File::Basename; use File::Path qw(make_path); use Fcntl; @@ -768,6 +769,13 @@ sub restore_oci_archive { } } + if (my $userstr = $oci_config_get_checked_scalar->('User')) { + my ($uid, $gid, $groups) = resolve_oci_user($userstr, $rootdir); + push $conf->{lxc}->@*, ['lxc.init.uid', $uid] if defined($uid); + push $conf->{lxc}->@*, ['lxc.init.gid', $gid] if defined($gid); + push $conf->{lxc}->@*, ['lxc.init.groups', $groups] if defined($groups); + } + if (my $working_dir = $oci_config_get_checked_scalar->('WorkingDir')) { push $conf->{lxc}->@*, ['lxc.init.cwd', $working_dir]; } @@ -782,4 +790,78 @@ sub restore_oci_archive { return $conf; # it's a reference anyway, so return mostly for convenience. } +sub resolve_oci_user { + my ($userstr, $rootdir) = @_; + + my ($user, $group) = $userstr =~ /^([^:]+)(?::([^:]+))?$/ + or die "OCI config value for 'User' has an invalid format\n"; + + my ($etc_passwd, $etc_group) = @{ + PVE::Tools::run_fork(sub { + # Prevent symlinks from escaping out of container rootdir + chroot($rootdir) or die "failed to change root to: $rootdir: $!\n"; + chdir('/') or die "failed to change to root directory\n"; + my $etc_passwd = abs_path('/etc/passwd') + or die "cannot resolve /etc/passwd path in container rootfs\n"; + my $etc_group = abs_path('/etc/group') + or die "cannot resolve /etc/group path in container rootfs\n"; + + return [$rootdir . $etc_passwd, $rootdir . $etc_group]; + }) + }; + + # Scan file, match column $match_index against $match_val, return value at $ret_index + my $lookup_field = sub { + my ($file, $match_index, $match_val, $ret_index) = @_; + + open(my $fh, '<', $file) or return undef; + while (my $line = <$fh>) { + chomp $line; + my @fields = split(/:/, $line); + if (defined($fields[$match_index]) && $fields[$match_index] eq $match_val) { + return $fields[$ret_index]; + } + } + return undef; + }; + + my $get_supplementary_groups = sub { + my ($username) = @_; + + my @groups; + open(my $fh, '<', $etc_group) or return undef; + while (my $line = <$fh>) { + chomp $line; + my (undef, undef, $gid, $user_list) = split(/:/, $line); + next if !defined($gid) || !defined($user_list); + my @users = split(/,/, $user_list); + push @groups, $gid if grep { $_ eq $username } @users; + } + return join(',', @groups); + }; + + my ($uid, $username, $gid, $groups); + + if ($user =~ /^\d+$/) { + $uid = $user; + $username = $lookup_field->($etc_passwd, 2, $uid, 0); + } else { + $username = $user; + $uid = $lookup_field->($etc_passwd, 0, $username, 2); + } + + if (defined($group)) { + if ($group =~ /^\d+$/) { + $gid = $group; + } else { + $gid = $lookup_field->($etc_group, 0, $group, 2); + } + } else { + $gid = $lookup_field->($etc_passwd, 2, $uid, 3) if defined($uid); + $groups = $get_supplementary_groups->($username) if defined($username); + } + + return ($uid, $gid, $groups); +} + 1; -- 2.47.3 _______________________________________________ pve-devel mailing list [email protected] https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-devel
