Date: Mon, 11 Sep 2023 13:13:24 +0300
From: "Konstantin Meskhidze (A)" <konstantin.meskhidze@...wei.com>
To: Mickaël Salaün <mic@...ikod.net>, Paul Moore
	<paul@...l-moore.com>
CC: <artem.kuzin@...wei.com>, <gnoack3000@...il.com>,
	<willemdebruijn.kernel@...il.com>, <yusongping@...wei.com>,
	<linux-security-module@...r.kernel.org>, <netdev@...r.kernel.org>,
	<netfilter-devel@...r.kernel.org>
Subject: Re: [PATCH v11.1] selftests/landlock: Add 11 new test suites
 dedicated to network



8/17/2023 6:08 PM, Mickaël Salaün пишет:
> On Sat, Aug 12, 2023 at 05:37:00PM +0300, Konstantin Meskhidze (A) wrote:
>> 
>> 
>> 7/12/2023 10:02 AM, Mickaël Salaün пишет:
>> > 
>> > On 06/07/2023 16:55, Mickaël Salaün wrote:
>> > > From: Konstantin Meskhidze <konstantin.meskhidze@...wei.com>
>> > > 
>> > > This patch is a revamp of the v11 tests [1] with new tests (see the
>> > > "Changes since v11" description).  I (Mickaël) only added the following
>> > > todo list and the "Changes since v11" sections in this commit message.
>> > > I think this patch is good but it would appreciate reviews.
>> > > You can find the diff of my changes here but it is not really readable:
>> > > https://git.kernel.org/mic/c/78edf722fba5 (landlock-net-v11 branch)
>> > > [1] https://lore.kernel.org/all/20230515161339.631577-11-konstantin.meskhidze@huawei.com/
>> > > TODO:
>> > > - Rename all "net_service" to "net_port".
>> > > - Fix the two kernel bugs found with the new tests.
>> > > - Update this commit message with a small description of all tests.
>> > 
>> > [...]
> 
>> > We should also add a test to make sure errno is the same with and
>> > without sandboxing when using port 0 for connect and consistent with
>> > bind (using an available port). The test fixture and variants should be
>> > quite similar to the "ipv4" ones, but we can also add AF_INET6 variants,
>> > which will result in 8 "ip" variants:
>> > 
>> > TEST_F(ip, port_zero)
>> > {
>> > 	if (variant->sandbox == TCP_SANDBOX) {
>> > 		/* Denies any connect and bind. */
>> > 	}
>> > 	/* Checks errno for port 0. */
>> > }
>> As I understand the would be the next test cases:
>> 
>> 	1. ip4, sandboxed, bind port 0 -> should return EACCES (denied by
>> landlock).
> 
> Without any allowed port, yes. This test case is useful.
> 
> By tuning /proc/sys/net/ipv4/ip_local_port_range (see
> inet_csk_find_open_port call) we should be able to pick a specific
> allowed port and test it.  We can also test for the EADDRINUSE error to
> make sure error ordering is correct (compared with -EACCES).
   Sorry, did not get this case. Could please explain it with more details?
> 
> However, I think the current LSM API don't enable to infer this random
> port because the LSM hook is called before a port is picked.  If this is
> correct, the best way to control port binding would be to always deny
> binding on port zero/random (when restricting port binding, whatever
> exception rules are in place). This explanation should be part of a
> comment for this specific exception.

   Yep, if some LSM rule (for bind) has been applied a with specific 
port, other attemps to bind with zero/random ports would be refused by 
LSM security checks.
> 
> Cc Paul
> 
>> 	2. ip4, non-sandboxed, bind port 0 -> should return 0 (should be bounded to
>> random port).
> 
> I think so but we need to make sure the random port cannot be < 1024, I
> guess with /proc/sys/net/ipv4/ip_local_port_range but I don't know for
> IPv6.

   For ipv4 when connecting to a server a client binds to a random port 
within /proc/sys/net/ipv4/ip_local_port_range, by default one my machine
this range is: cat /proc/sys/net/ipv4/ip_local_port_range
32768   60999.
But for ipv6 there is no such tuning range.

> 
>> 	3. ip6, sandboxed, bind port 0 -> should return EACCES (denied by
>> landlock).
>> 	4. ip6, non-sandboxed, bind port 0 -> should return 0 (should be bounded to
>> random port).
>> 	5. ip4, sandboxed, bind some available port, connect port 0 -> should
>> return -EACCES (denied by landlock).
> 
> Yes, but don't need to bind to anything (same for the next ones).
> 
>> 	6. ip4, non-sandboxed, bind some available port, connect port 0 -> should
>> return ECONNREFUSED.
> 
> Yes, but without any binding.
> 
>> 	7. ip6, sandboxed, bind some available port, connect port 0 -> should
>> return -EACCES (denied by landlock)
>> 	8. ip6, non-sandboxed, some bind available port, connect port 0 -> should
>> return ECONNREFUSED.
>> 
>> Correct?
> 
> Thinking more about this case, being able to add a rule with port zero
> *for a connect action* looks legitimate.  A rule with both connect and
> bind actions on port zero should then be denied.  We should fix
> add_rule_net_service() and test that (with a first layer allowing port
> zero, and a second without rule, for connect).

  So with first rule allowing port 0 connect action, the second rule 
with some another port and connect action, as a result test should allow 
that. Correct?
> 
> 
>> 
>> > 
>> > [...]
>> > 
>> > > +FIXTURE(inet)
>> > > +{
>> > > +	struct service_fixture srv0, srv1;
>> > > +};
>> > 
>> > The "inet" variants are useless and should be removed. The "inet"
>> > fixture can then be renamed to "ipv4_tcp".
>> > 
>>   So inet should be changed to ipv4_tcp and ipv6_tcp with next variants:
>> 
>>   - ipv4_tcp.no_sandbox_with_ipv4.port_endianness
>>   - ipv4_tcp.sandbox_with_ipv4.port_endianness
>>   - ipv6_tcp.no_sandbox_with_ipv6.port_endianness
>>   - ipv6_tcp.sandbox_with_ipv6.port_endianness
>> ????
>> 
>>    in this case we need double copy of TEST_F(inet, port_endianness) :
>> 	TEST_F(ipv4_tcp, port_endianness)
>> 	TEST_F(ipv6_tcp, port_endianness)
> 
> There is no need for any variant for the port_endianness test. You can
> rename "inet" to "ipv4_tcp" (and not "inet_tcp" like I said before).
> .

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