This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed- xenial' to 'verification-done-xenial'. If the problem still exists, change the tag 'verification-needed-xenial' to 'verification-failed- xenial'.
If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you! ** Tags added: verification-needed-xenial ** Tags added: verification-needed-zesty -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1721676 Title: implement errno action logging in seccomp for strict mode with snaps Status in Snappy: In Progress Status in linux package in Ubuntu: Fix Released Status in linux source package in Xenial: Fix Committed Status in linux source package in Zesty: Fix Committed Status in linux source package in Artful: Fix Released Bug description: A requirement for snappy is that security sandbox violations against policy are logged. In this manner learning tools can be written to parse the logs, etc and make developing on snappy easier. The current default seccomp action, in strict mode. is to kill the snap's thread that violated the policy but this is unfriendly to the developer and to the user. The desired action is to block the illegal system call and return an error with errno set to EPERM. However, seccomp does not emit log events when it takes that action. Seccomp should be updated to emit log events when taking the SECCOMP_RET_ERRNO action and then snappy can switch to the using that action when blocking illegal system calls. [Impact] Snapd needs a way to log SECCOMP_RET_ERRNO seccomp actions in order to have a more friendly strict mode. Such functionality has been merged upstream into 4.14-rc2. No libseccomp changes are needed at this time since snap-confine loads the BPF filter directly into the kernel without using libseccomp. [Test Case] Running the libseccomp "live" tests will exercise the kernel's seccomp enforcement and help to help catch any regressions. Note that on Artful, there's an existing test failure (20-live- basic_die%%002-00001): $ sudo apt build-dep -y libseccomp $ sudo apt install -y cython $ apt source libseccomp $ cd libseccomp-* $ autoreconf -ivf && ./configure --enable-python && make check-build $ (cd tests && ./regression -T live) All tests should pass on zesty (12 tests) and xenial (10 tests). On artful, you'll see one pre-existing failure: ... Test 20-live-basic_die%%002-00001 result: FAILURE 20-live-basic_die TRAP rc=159 ... Regression Test Summary tests run: 12 tests skipped: 0 tests passed: 11 tests failed: 1 tests errored: 0 ============================================================ ---------------------------- Running the seccomp kernel selftests is also a great to exercise seccomp and the kernel patch set proposed for the SRU includes additional seccomp selftests. To build, enter into the root of the kernel source tree and build the seccomp test binary: $ make -C tools/testing/selftests TARGETS=seccomp Now you can execute tools/testing/selftests/seccomp/seccomp_bpf or even copy it to a test machine and run it there. On Xenial, 54/54 tests should pass and 58/58 should pass on Zesty. ---------------------------- Now we can run a single test to verify that SECCOMP_RET_ERRNO is logged when the application opts into it. First, verify that "errno" is listed in the actions_logged sysctl: $ cat /proc/sys/kernel/seccomp/actions_logged kill trap errno trace log Now, build and run the test program: $ gcc -o lp1721676-kernel-test lp1721676-kernel-test.c $ ./lp1721676-kernel-test SUCCESS: getpid() failed as expected: Operation not permitted It should have generated a message like this in /var/log/syslog: kernel: [79338.804966] audit: type=1326 audit(1507259221.875:27): auid=1000 uid=1000 gid=1000 ses=5 pid=3091 comm="lp1721676-kerne" exe="/home/tyhicks/lp1721676-kernel-test" sig=0 arch=c000003e syscall=39 compat=0 ip=0x7fb91829c499 code=0x50000 Disable errno logging in the sysctl: $ echo kill trap trace log | sudo tee /proc/sys/kernel/seccomp/actions_logged kill trap trace log Rerun the test program and ensure that nothing was logged this time. [Regression Potential] The kernel patches received a lot of review between Kees and some others interested in improved seccomp logging. I authored the patches and feel comfortable/confident with my backported versions. They do not change the behavior of seccomp logging by default but offer ways applications to opt into more logging and, on the flipside, ways for the administrator to quite any additional logging. To manage notifications about this bug go to: https://bugs.launchpad.net/snappy/+bug/1721676/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
