josch/mmdebstrap
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let test_unshare_userns error out itself if necessary

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This commit is contained in:
Johannes Schauer Marin Rodrigues 2023-03-16 08:14:39 +01:00
parent 055e1719b9
commit 55cae49ec7
Signed by: josch
GPG key ID: F2CBA5C78FBD83E1
1 changed files with 19 additions and 42 deletions
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mmdebstrap
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@ -305,23 +305,18 @@ sub shellescape {
sub test_unshare_userns {
my $verbose = shift;
my $fail = shift;
local *maybe_warn = sub {
local *maybe_error = sub {
my $msg = shift;
if ($verbose) {
if ($fail) {
error $msg;
} else {
warning $msg;
}
} else {
debug $msg;
}
};
if ($EFFECTIVE_USER_ID == 0) {
maybe_warn("cannot unshare user namespace when executing as root");
maybe_error("cannot unshare user namespace when executing as root");
return 0;
}
# arguments to syscalls have to be stored in their own variable or
@ -335,7 +330,7 @@ sub test_unshare_userns {
if ($ret == 0) {
exit 0;
} else {
maybe_warn("unshare syscall failed: $!");
maybe_error("unshare syscall failed: $!");
exit 1;
}
}
@ -348,28 +343,28 @@ sub test_unshare_userns {
system "newuidmap 2>/dev/null";
if (($? >> 8) != 1) {
if (($? >> 8) == 127) {
maybe_warn("cannot find newuidmap");
maybe_error("cannot find newuidmap");
} else {
maybe_warn("newuidmap returned unknown exit status: $?");
maybe_error("newuidmap returned unknown exit status: $?");
}
return 0;
}
system "newgidmap 2>/dev/null";
if (($? >> 8) != 1) {
if (($? >> 8) == 127) {
maybe_warn("cannot find newgidmap");
maybe_error("cannot find newgidmap");
} else {
maybe_warn("newgidmap returned unknown exit status: $?");
maybe_error("newgidmap returned unknown exit status: $?");
}
return 0;
}
my @idmap = read_subuid_subgid($verbose);
if (scalar @idmap == 0) {
maybe_warn("failed to parse /etc/subuid and /etc/subgid");
maybe_error("failed to parse /etc/subuid and /etc/subgid");
return 0;
}
# too much can go wrong when doing the dance required to unsharing the user
# namespace, so instead of adding more complexity to support maybe_warn()
# namespace, so instead of adding more complexity to support maybe_error()
# to a function that is already too complex, we use eval()
eval {
$pid = get_unshare_cmd(
@ -384,12 +379,12 @@ sub test_unshare_userns {
);
waitpid $pid, 0;
if ($? != 0) {
maybe_warn("failed to unshare the user namespace");
maybe_error("failed to unshare the user namespace");
return 0;
}
};
if ($@) {
maybe_warn($@);
maybe_error($@);
return 0;
}
return 1;
@ -4372,8 +4367,8 @@ sub main() {
# lxc-usernsexec -- lxc-unshare -s 'MOUNT|PID|UTSNAME|IPC' ...
# but without needing lxc
if (scalar @ARGV >= 1 && $ARGV[0] eq "--unshare-helper") {
if ($EFFECTIVE_USER_ID != 0 && !test_unshare_userns(1)) {
exit 1;
if ($EFFECTIVE_USER_ID != 0) {
test_unshare_userns(1);
}
my @idmap = ();
if ($EFFECTIVE_USER_ID != 0) {
@ -4840,26 +4835,8 @@ sub main() {
}
# ...or we are not root and then we need to be able to unshare the user
# namespace.
if ($EFFECTIVE_USER_ID != 0 && !test_unshare_userns(1, 1)) {
my $procfile = '/proc/sys/kernel/unprivileged_userns_clone';
open(my $fh, '<', $procfile)
or error "failed to open $procfile: $!";
chomp(
my $content = do { local $/; <$fh> }
);
close($fh);
if ($content ne "1") {
info "/proc/sys/kernel/unprivileged_userns_clone is set to"
. " $content";
info "Try running:";
info " sudo sysctl -w kernel.unprivileged_userns_clone=1";
info "or permanently enable unprivileged usernamespaces by"
. " putting the setting into /etc/sysctl.d/";
info "THIS SETTING HAS SECURITY IMPLICATIONS!";
info "Refer to https://bugs.debian.org/cgi-bin/"
. "bugreport.cgi?bug=898446";
}
exit 1;
if ($EFFECTIVE_USER_ID != 0) {
test_unshare_userns(1);
}
} elsif ($options->{mode} eq 'chrootless') {
if ($EFFECTIVE_USER_ID == 0) {
@ -6692,9 +6669,9 @@ decides which way this is achieved.
This mode automatically selects a fitting mode. If the effective user id is the
one of the superuser, then the B<sudo> mode is chosen. Otherwise, the
B<unshare> mode is picked if the system has the sysctl
C<kernel.unprivileged_userns_clone> set to C<1>. Should that not be the case
and if the fakechroot binary exists, the B<fakechroot> mode is chosen.
B<unshare> mode is picked if F</etc/subuid> and F</etc/subgid> are set up
correctly. Should that not be the case and if the fakechroot binary exists, the
B<fakechroot> mode is chosen.
=item B<sudo>, B<root>