[0/2] Forbid illegitimate binding via listen(2)

Message

Mikhail Ivanov April 8, 2024, 9:47 a.m. UTC

listen(2) can be called without explicit bind(2) call. For a TCP socket
it would result in assigning random port(in some range) to this socket
by the kernel. If Landlock sandbox supports LANDLOCK_ACCESS_NET_BIND_TCP,
this may lead to implicit access to a prohibited (by Landlock sandbox)
port. Malicious sandboxed process can accidentally impersonate a
legitimate server process (if listen(2) assigns it a server port number).

Patch adds hook on socket_listen() that prevents such scenario by checking
LANDLOCK_ACCESS_NET_BIND_TCP access for port 0.

Few tests were added to cover this case.

Code coverage(gcov):
* security/landlock:
lines......: 94.5% (745 of 788 lines)
functions..: 97.1% (100 of 103 functions)

Ivanov Mikhail (2):
  landlock: Add hook on socket_listen()
  selftests/landlock: Create 'listen_zero', 'deny_listen_zero' tests

 security/landlock/net.c                     | 104 +++++++++++++++++---
 tools/testing/selftests/landlock/net_test.c |  89 +++++++++++++++++
 2 files changed, 177 insertions(+), 16 deletions(-)