[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(-)

Comments

Mickaël Salaün June 19, 2024, 12:20 p.m. UTC | #1

Could you please send a v2 for this patch? I'd like this issue to be
fixed, especially before any other Landlock feature get merged.

On Mon, Apr 08, 2024 at 05:47:45PM +0800, Ivanov Mikhail wrote:
> 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(-)
> 
> -- 
> 2.34.1
> 
>