The first use case is running the container backup subroutine for
external providers inside a user namespace. That allows them to see
the filesystem to back-up from the containers perspective and also
improves security because of isolation.
Copied and adapted the relevant parts from the pve-buildpkg
repository.
Originally-by: Wolfgang Bumiller <w.bumil...@proxmox.com>
[FE: add $idmap parameter, drop $aux_groups parameter]
Signed-off-by: Fiona Ebner <f.eb...@proxmox.com>
---
New in v3.
src/Makefile | 1 +
src/PVE/Env.pm | 136 +++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 137 insertions(+)
create mode 100644 src/PVE/Env.pm
diff --git a/src/Makefile b/src/Makefile
index 2d8bdc4..dba26e3 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -15,6 +15,7 @@ LIB_SOURCES = \
Certificate.pm \
CpuSet.pm \
Daemon.pm \
+ Env.pm \
Exception.pm \
Format.pm \
INotify.pm \
diff --git a/src/PVE/Env.pm b/src/PVE/Env.pm
new file mode 100644
index 0000000..e11bec0
--- /dev/null
+++ b/src/PVE/Env.pm
@@ -0,0 +1,136 @@
+package PVE::Env;
+
+use strict;
+use warnings;
+
+use Fcntl qw(O_WRONLY);
+use POSIX qw(EINTR);
+use Socket;
+
+require qw(syscall.ph);
+
+use constant {CLONE_NEWNS => 0x00020000,
+ CLONE_NEWUSER => 0x10000000};
+
+sub unshare($) {
+ my ($flags) = @_;
+ return 0 == syscall(272, $flags);
+}
+
+sub __set_id_map($$$) {
+ my ($pid, $what, $value) = @_;
+ sysopen(my $fd, "/proc/$pid/${what}_map", O_WRONLY)
+ or die "failed to open child process' ${what}_map\n";
+ my $rc = syswrite($fd, $value);
+ if (!$rc || $rc != length($value)) {
+ die "failed to set sub$what: $!\n";
+ }
+ close($fd);
+}
+
+sub set_id_map($$) {
+ my ($pid, $id_map) = @_;
+
+ my $gid_map = '';
+ my $uid_map = '';
+
+ for my $map ($id_map->@*) {
+ my ($type, $ct, $host, $length) = $map->@*;
+
+ $gid_map .= "$ct $host $length\n" if $type eq 'g';
+ $uid_map .= "$ct $host $length\n" if $type eq 'u';
+ }
+
+ __set_id_map($pid, 'gid', $gid_map) if $gid_map;
+ __set_id_map($pid, 'uid', $uid_map) if $uid_map;
+}
+
+sub wait_for_child($;$) {
+ my ($pid, $noerr) = @_;
+ my $interrupts = 0;
+ while (waitpid($pid, 0) != $pid) {
+ if ($! == EINTR) {
+ warn "interrupted...\n";
+ kill(($interrupts > 3 ? 9 : 15), $pid);
+ $interrupts++;
+ }
+ }
+ my $status = POSIX::WEXITSTATUS($?);
+ return $status if $noerr;
+
+ if ($? == -1) {
+ die "failed to execute\n";
+ } elsif (POSIX::WIFSIGNALED($?)) {
+ my $sig = POSIX::WTERMSIG($?);
+ die "got signal $sig\n";
+ } elsif ($status != 0) {
+ warn "exit code $status\n";
+ }
+ return $status;
+}
+
+sub forked(&%) {
+ my ($code, %opts) = @_;
+
+ pipe(my $except_r, my $except_w) or die "pipe: $!\n";
+
+ my $pid = fork();
+ die "fork failed: $!\n" if !defined($pid);
+
+ if ($pid == 0) {
+ close($except_r);
+ eval { $code->() };
+ if ($@) {
+ print {$except_w} $@;
+ $except_w->flush();
+ POSIX::_exit(1);
+ }
+ POSIX::_exit(0);
+ }
+ close($except_w);
+
+ my $err;
+ if (my $afterfork = $opts{afterfork}) {
+ eval { $afterfork->($pid); };
+ if ($err = $@) {
+ kill(15, $pid);
+ $opts{noerr} = 1;
+ }
+ }
+ if (!$err) {
+ $err = do { local $/ = undef; <$except_r> };
+ }
+ my $rv = wait_for_child($pid, $opts{noerr});
+ die $err if $err;
+ die "an unknown error occurred\n" if $rv != 0;
+ return $rv;
+}
+
+sub run_in_userns(&;$) {
+ my ($code, $id_map) = @_;
+ socketpair(my $sp, my $sc, AF_UNIX, SOCK_STREAM, PF_UNSPEC)
+ or die "socketpair: $!\n";
+ forked(sub {
+ close($sp);
+ unshare(CLONE_NEWUSER|CLONE_NEWNS) or die "unshare(NEWUSER|NEWNS):
$!\n";
+ syswrite($sc, "1\n") == 2 or die "write: $!\n";
+ shutdown($sc, 1);
+ my $two = <$sc>;
+ die "failed to sync with parent process\n" if $two ne "2\n";
+ close($sc);
+ $! = undef;
+ ($(, $)) = (0, 0); die "$!\n" if $!;
+ ($<, $>) = (0, 0); die "$!\n" if $!;
+ $code->();
+ }, afterfork => sub {
+ my ($pid) = @_;
+ close($sc);
+ my $one = <$sp>;
+ die "failed to sync with userprocess\n" if $one ne "1\n";
+ set_id_map($pid, $id_map);
+ syswrite($sp, "2\n") == 2 or die "write: $!\n";
+ close($sp);
+ });
+}
+
+1;
--
2.39.5
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