95 lines
3.4 KiB
Diff
95 lines
3.4 KiB
Diff
From 28650077f36466d9c5ee27ef2006fae3171a2430 Mon Sep 17 00:00:00 2001
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From: Lennart Poettering <lennart@poettering.net>
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Date: Mon, 30 Jun 2014 16:22:12 +0200
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Subject: [PATCH] nspawn: block open_by_handle_at() and others via seccomp
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Let's protect ourselves against the recently reported docker security
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issue. Our man page makes clear that we do not make any security
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promises anyway, but well, this one is easy to mitigate, so let's do it.
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While we are at it block a couple of more syscalls that are no good in
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containers, too.
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---
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src/nspawn/nspawn.c | 47 +++++++++++++++++++++++++++++++++++------------
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1 file changed, 35 insertions(+), 12 deletions(-)
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diff --git src/nspawn/nspawn.c src/nspawn/nspawn.c
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index fd61d07..656c1bf 100644
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--- src/nspawn/nspawn.c
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+++ src/nspawn/nspawn.c
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@@ -1864,22 +1864,25 @@ static int setup_macvlan(pid_t pid) {
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return 0;
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}
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-static int audit_still_doesnt_work_in_containers(void) {
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+static int setup_seccomp(void) {
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#ifdef HAVE_SECCOMP
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+ static const int blacklist[] = {
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+ SCMP_SYS(kexec_load),
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+ SCMP_SYS(open_by_handle_at),
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+ SCMP_SYS(init_module),
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+ SCMP_SYS(finit_module),
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+ SCMP_SYS(delete_module),
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+ SCMP_SYS(iopl),
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+ SCMP_SYS(ioperm),
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+ SCMP_SYS(swapon),
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+ SCMP_SYS(swapoff),
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+ };
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+
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scmp_filter_ctx seccomp;
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+ unsigned i;
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int r;
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- /*
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- Audit is broken in containers, much of the userspace audit
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- hookup will fail if running inside a container. We don't
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- care and just turn off creation of audit sockets.
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-
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- This will make socket(AF_NETLINK, *, NETLINK_AUDIT) fail
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- with EAFNOSUPPORT which audit userspace uses as indication
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- that audit is disabled in the kernel.
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- */
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-
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seccomp = seccomp_init(SCMP_ACT_ALLOW);
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if (!seccomp)
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return log_oom();
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@@ -1890,6 +1893,26 @@ static int audit_still_doesnt_work_in_containers(void) {
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goto finish;
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}
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+ for (i = 0; i < ELEMENTSOF(blacklist); i++) {
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+ r = seccomp_rule_add(seccomp, SCMP_ACT_ERRNO(EPERM), blacklist[i], 0);
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+ if (r == -EFAULT)
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+ continue; /* unknown syscall */
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+ if (r < 0) {
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+ log_error("Failed to block syscall: %s", strerror(-r));
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+ goto finish;
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+ }
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+ }
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+
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+ /*
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+ Audit is broken in containers, much of the userspace audit
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+ hookup will fail if running inside a container. We don't
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+ care and just turn off creation of audit sockets.
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+
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+ This will make socket(AF_NETLINK, *, NETLINK_AUDIT) fail
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+ with EAFNOSUPPORT which audit userspace uses as indication
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+ that audit is disabled in the kernel.
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+ */
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+
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r = seccomp_rule_add(
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seccomp,
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SCMP_ACT_ERRNO(EAFNOSUPPORT),
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@@ -3050,7 +3073,7 @@ int main(int argc, char *argv[]) {
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dev_setup(arg_directory);
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- if (audit_still_doesnt_work_in_containers() < 0)
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+ if (setup_seccomp() < 0)
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goto child_fail;
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if (setup_dev_console(arg_directory, console) < 0)
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--
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1.7.9.2
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