+++ /dev/null
-From 16af238036a5464ae8f2420ed3af214f0de875f9 Mon Sep 17 00:00:00 2001
-From: Christian Brauner <christian.brauner@ubuntu.com>
-Date: Sat, 28 Jan 2017 13:02:34 +0100
-Subject: [PATCH] CVE-2017-5985: Ensure target netns is caller-owned
-
-Before this commit, lxc-user-nic could potentially have been tricked into
-operating on a network namespace over which the caller did not hold privilege.
-
-This commit ensures that the caller is privileged over the network namespace by
-temporarily dropping privilege.
-
-Launchpad: https://bugs.launchpad.net/ubuntu/+source/lxc/+bug/1654676
-Reported-by: Jann Horn <jannh@google.com>
-Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
-Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
----
- src/lxc/lxc_user_nic.c | 119 ++++++++++++++++++++++++++++++++++++-------------
- 1 file changed, 87 insertions(+), 32 deletions(-)
-
-diff --git a/src/lxc/lxc_user_nic.c b/src/lxc/lxc_user_nic.c
-index 409a53a1..96dc3986 100644
---- a/src/lxc/lxc_user_nic.c
-+++ b/src/lxc/lxc_user_nic.c
-@@ -50,6 +50,14 @@
- #include "utils.h"
- #include "network.h"
-
-+#define usernic_debug_stream(stream, format, ...) \
-+ do { \
-+ fprintf(stream, "%s: %d: %s: " format, __FILE__, __LINE__, \
-+ __func__, __VA_ARGS__); \
-+ } while (false)
-+
-+#define usernic_error(format, ...) usernic_debug_stream(stderr, format, __VA_ARGS__)
-+
- static void usage(char *me, bool fail)
- {
- fprintf(stderr, "Usage: %s lxcpath name pid type bridge nicname\n", me);
-@@ -670,68 +678,115 @@ again:
- }
-
- #define VETH_DEF_NAME "eth%d"
--
- static int rename_in_ns(int pid, char *oldname, char **newnamep)
- {
-- int fd = -1, ofd = -1, ret, ifindex = -1;
-+ uid_t ruid, suid, euid;
-+ int fret = -1;
-+ int fd = -1, ifindex = -1, ofd = -1, ret;
- bool grab_newname = false;
-
- ofd = lxc_preserve_ns(getpid(), "net");
- if (ofd < 0) {
-- fprintf(stderr, "Failed opening network namespace path for '%d'.", getpid());
-- return -1;
-+ usernic_error("Failed opening network namespace path for '%d'.", getpid());
-+ return fret;
- }
-
- fd = lxc_preserve_ns(pid, "net");
- if (fd < 0) {
-- fprintf(stderr, "Failed opening network namespace path for '%d'.", pid);
-- return -1;
-+ usernic_error("Failed opening network namespace path for '%d'.", pid);
-+ goto do_partial_cleanup;
-+ }
-+
-+ ret = getresuid(&ruid, &euid, &suid);
-+ if (ret < 0) {
-+ usernic_error("Failed to retrieve real, effective, and saved "
-+ "user IDs: %s\n",
-+ strerror(errno));
-+ goto do_partial_cleanup;
-+ }
-+
-+ ret = setns(fd, CLONE_NEWNET);
-+ close(fd);
-+ fd = -1;
-+ if (ret < 0) {
-+ usernic_error("Failed to setns() to the network namespace of "
-+ "the container with PID %d: %s.\n",
-+ pid, strerror(errno));
-+ goto do_partial_cleanup;
- }
-
-- if (setns(fd, 0) < 0) {
-- fprintf(stderr, "setns to container network namespace\n");
-- goto out_err;
-+ ret = setresuid(ruid, ruid, 0);
-+ if (ret < 0) {
-+ usernic_error("Failed to drop privilege by setting effective "
-+ "user id and real user id to %d, and saved user "
-+ "ID to 0: %s.\n",
-+ ruid, strerror(errno));
-+ // COMMENT(brauner): It's ok to jump to do_full_cleanup here
-+ // since setresuid() will succeed when trying to set real,
-+ // effective, and saved to values they currently have.
-+ goto do_full_cleanup;
- }
-- close(fd); fd = -1;
-+
- if (!*newnamep) {
- grab_newname = true;
- *newnamep = VETH_DEF_NAME;
-- if (!(ifindex = if_nametoindex(oldname))) {
-- fprintf(stderr, "failed to get netdev index\n");
-- goto out_err;
-+
-+ ifindex = if_nametoindex(oldname);
-+ if (!ifindex) {
-+ usernic_error("Failed to get netdev index: %s.\n", strerror(errno));
-+ goto do_full_cleanup;
- }
- }
-- if ((ret = lxc_netdev_rename_by_name(oldname, *newnamep)) < 0) {
-- fprintf(stderr, "Error %d renaming netdev %s to %s in container\n", ret, oldname, *newnamep);
-- goto out_err;
-+
-+ ret = lxc_netdev_rename_by_name(oldname, *newnamep);
-+ if (ret < 0) {
-+ usernic_error("Error %d renaming netdev %s to %s in container.\n", ret, oldname, *newnamep);
-+ goto do_full_cleanup;
- }
-+
- if (grab_newname) {
-- char ifname[IFNAMSIZ], *namep = ifname;
-+ char ifname[IFNAMSIZ];
-+ char *namep = ifname;
-+
- if (!if_indextoname(ifindex, namep)) {
-- fprintf(stderr, "Failed to get new netdev name\n");
-- goto out_err;
-+ usernic_error("Failed to get new netdev name: %s.\n", strerror(errno));
-+ goto do_full_cleanup;
- }
-+
- *newnamep = strdup(namep);
- if (!*newnamep)
-- goto out_err;
-+ goto do_full_cleanup;
- }
-- if (setns(ofd, 0) < 0) {
-- fprintf(stderr, "Error returning to original netns\n");
-- close(ofd);
-- return -1;
-+
-+ fret = 0;
-+
-+do_full_cleanup:
-+ ret = setresuid(ruid, euid, suid);
-+ if (ret < 0) {
-+ usernic_error("Failed to restore privilege by setting effective "
-+ "user id to %d, real user id to %d, and saved user "
-+ "ID to %d: %s.\n",
-+ ruid, euid, suid, strerror(errno));
-+ fret = -1;
-+ // COMMENT(brauner): setns() should fail if setresuid() doesn't
-+ // succeed but there's no harm in falling through; keeps the
-+ // code cleaner.
- }
-- close(ofd);
-
-- return 0;
-+ ret = setns(ofd, CLONE_NEWNET);
-+ if (ret < 0) {
-+ usernic_error("Failed to setns() to original network namespace "
-+ "of PID %d: %s.\n",
-+ ofd, strerror(errno));
-+ fret = -1;
-+ }
-
--out_err:
-- if (ofd >= 0)
-- close(ofd);
-- if (setns(ofd, 0) < 0)
-- fprintf(stderr, "Error returning to original network namespace\n");
-+do_partial_cleanup:
- if (fd >= 0)
- close(fd);
-- return -1;
-+ close(ofd);
-+
-+ return fret;
- }
-
- /*
---
-2.11.0
-
projects / buildroot.git / commitdiff