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Message-ID: <fd996135-1ad5-dd3c-4b42-23013cad208d@digikod.net>
Date: Thu, 19 May 2022 16:29:49 +0200
From: Mickaël Salaün <mic@...ikod.net>
To: Konstantin Meskhidze <konstantin.meskhidze@...wei.com>
Cc: willemdebruijn.kernel@...il.com,
linux-security-module@...r.kernel.org, netdev@...r.kernel.org,
netfilter-devel@...r.kernel.org, yusongping@...wei.com,
anton.sirazetdinov@...wei.com
Subject: Re: [PATCH v5 09/15] seltests/landlock: add tests for bind() hooks
On 19/05/2022 14:10, Konstantin Meskhidze wrote:
>
>
> 5/17/2022 12:11 AM, Mickaël Salaün пишет:
>>
>> On 16/05/2022 17:20, Konstantin Meskhidze wrote:
>>> Adds selftests for bind socket action.
>>> The first is with no landlock restrictions:
>>> - bind_no_restrictions_ip4;
>>> - bind_no_restrictions_ip6;
>>> The second ones is with mixed landlock rules:
>>> - bind_with_restrictions_ip4;
>>> - bind_with_restrictions_ip6;
>>>
>>> Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@...wei.com>
>>> ---
>>>
>>> Changes since v3:
>>> * Split commit.
>>> * Add helper create_socket.
>>> * Add FIXTURE_SETUP.
>>>
>>> Changes since v4:
>>> * Adds port[MAX_SOCKET_NUM], struct sockaddr_in addr4
>>> and struct sockaddr_in addr6 in FIXTURE.
>>> * Refactoring FIXTURE_SETUP:
>>> - initializing self->port, self->addr4 and self->addr6.
>>> - adding network namespace.
>>> * Refactoring code with self->port, self->addr4 and
>>> self->addr6 variables.
>>> * Adds selftests for IP6 family:
>>> - bind_no_restrictions_ip6.
>>> - bind_with_restrictions_ip6.
>>> * Refactoring selftests/landlock/config
>>> * Moves enforce_ruleset() into common.h
>>>
>>> ---
>>> tools/testing/selftests/landlock/common.h | 9 +
>>> tools/testing/selftests/landlock/config | 5 +-
>>> tools/testing/selftests/landlock/fs_test.c | 10 -
>>> tools/testing/selftests/landlock/net_test.c | 237 ++++++++++++++++++++
>>> 4 files changed, 250 insertions(+), 11 deletions(-)
>>> create mode 100644 tools/testing/selftests/landlock/net_test.c
>>>
>>> diff --git a/tools/testing/selftests/landlock/common.h
>>> b/tools/testing/selftests/landlock/common.h
>>> index 7ba18eb23783..c5381e641dfd 100644
>>> --- a/tools/testing/selftests/landlock/common.h
>>> +++ b/tools/testing/selftests/landlock/common.h
>>> @@ -102,6 +102,15 @@ static inline int landlock_restrict_self(const
>>> int ruleset_fd,
>>> }
>>> #endif
>>>
>>> +static void enforce_ruleset(struct __test_metadata *const _metadata,
>>> + const int ruleset_fd)
>>> +{
>>> + ASSERT_EQ(0, prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0));
>>> + ASSERT_EQ(0, landlock_restrict_self(ruleset_fd, 0)) {
>>> + TH_LOG("Failed to enforce ruleset: %s", strerror(errno));
>>> + }
>>> +}
>>> +
>>
>> Please create a commit which moves all the needed code for all network
>> tests. I think there is only this helper though.
>
> Ok. I will create one additional commit for moving this helper.
> But after I have moved the helper to common.h, I got warnings while
> compiling seltests where I don't use the one (base_test and ptrace_test)
Move it after clear_cap() and use the same attributes.
[...]
>>> diff --git a/tools/testing/selftests/landlock/config
>>> b/tools/testing/selftests/landlock/config
>>> index 0f0a65287bac..b56f3274d3f5 100644
>>> --- a/tools/testing/selftests/landlock/config
>>> +++ b/tools/testing/selftests/landlock/config
>>> @@ -1,7 +1,10 @@
>>> +CONFIG_INET=y
>>> +CONFIG_IPV6=y
>>> +CONFIG_NET=y
>>> CONFIG_OVERLAY_FS=y
>>> CONFIG_SECURITY_LANDLOCK=y
>>> CONFIG_SECURITY_PATH=y
>>> CONFIG_SECURITY=y
>>> CONFIG_SHMEM=y
>>> CONFIG_TMPFS_XATTR=y
>>> -CONFIG_TMPFS=y
>>> +CONFIG_TMPFS=y
>>> \ No newline at end of file
You also need to add CONFIG_NET_NS.
[...]
>>
>>> + self->port[i] = SOCK_PORT_START + SOCK_PORT_ADD*i;
>>> + self->addr4[i].sin_family = AF_INET;
>>> + self->addr4[i].sin_port = htons(self->port[i]);
>>> + self->addr4[i].sin_addr.s_addr = htonl(INADDR_ANY);
>>
>> Could you use the local addr (127.0.0.1) instead?
>
> Why cant I use INADDR_ANY here?
You can, but it is cleaner to bind to a specified address (i.e. you
control where a connection come from), and I guess this variable/address
could be used to establish connections as well.
>>
>>> + memset(&(self->addr4[i].sin_zero), '\0', 8);
>>> + }
>>> +
>>> + /* Creates IP6 socket addresses */
>>> + for (i = 0; i < MAX_SOCKET_NUM; i++) {
>>> + self->port[i] = SOCK_PORT_START + SOCK_PORT_ADD*i;
>>> + self->addr6[i].sin6_family = AF_INET6;
>>> + self->addr6[i].sin6_port = htons(self->port[i]);
>>> + self->addr6[i].sin6_addr = in6addr_any;
>>
>> ditto
>
> Why cant I use in6addr_any here?
Same as for IPV4.
>
>>
>>> + }
>>> +
>>> + set_cap(_metadata, CAP_SYS_ADMIN);
>>> + ASSERT_EQ(0, unshare(CLONE_NEWNET));
>>> + ASSERT_EQ(0, system("ip link set dev lo up"));
>>
>> If this is really required, could you avoid calling system() but set
>> up the network in C? You can strace it to see what is going on
>> underneath.
>>
> I did check. It's a lot of code to be run under the hood (more than
> one line) and it will just will complicate the test so I suggest to
> leave just ONE line of code here.
OK
>>
>>> + clear_cap(_metadata, CAP_SYS_ADMIN);
>>> +}
>>> +
>>> +FIXTURE_TEARDOWN(socket_test)
>>> +{ }
>>> +
>>> +TEST_F_FORK(socket_test, bind_no_restrictions_ip4) {
>>> +
>>> + int sockfd;
>>> +
>>> + sockfd = create_socket(_metadata, false, false);
>>> + ASSERT_LE(0, sockfd);
>>> +
>>> + /* Binds a socket to port[0] */
>>
>> This comment is not very useful in this context considering the below
>> line. It will be even more clear with the bind_variant() call.
>>
> Ok. I will fix it.
>>
>>> + ASSERT_EQ(0, bind(sockfd, (struct sockaddr *)&self->addr4[0],
>>> sizeof(self->addr4[0])));
>>> +
>>> + ASSERT_EQ(0, close(sockfd));
>>> +}
>>> +
>>> +TEST_F_FORK(socket_test, bind_no_restrictions_ip6) {
>>> +
>>> + int sockfd;
>>> +
>>> + sockfd = create_socket(_metadata, true, false);
>>> + ASSERT_LE(0, sockfd);
>>> +
>>> + /* Binds a socket to port[0] */
>>> + ASSERT_EQ(0, bind(sockfd, (struct sockaddr *)&self->addr6[0],
>>> sizeof(self->addr6[0])));
>>> +
>>> + ASSERT_EQ(0, close(sockfd));
>>> +}
>>> +
>>> +TEST_F_FORK(socket_test, bind_with_restrictions_ip4) {
>>> +
>>> + int sockfd;
>>> +
>>> + struct landlock_ruleset_attr ruleset_attr = {
>>> + .handled_access_net = LANDLOCK_ACCESS_NET_BIND_TCP |
>>> + LANDLOCK_ACCESS_NET_CONNECT_TCP,
>>> + };
>>> + struct landlock_net_service_attr net_service_1 = {
>>> + .allowed_access = LANDLOCK_ACCESS_NET_BIND_TCP |
>>> + LANDLOCK_ACCESS_NET_CONNECT_TCP,
>>> + .port = self->port[0],
>>> + };
>>> + struct landlock_net_service_attr net_service_2 = {
>>> + .allowed_access = LANDLOCK_ACCESS_NET_CONNECT_TCP,
>>> + .port = self->port[1],
>>> + };
>>> + struct landlock_net_service_attr net_service_3 = {
>>> + .allowed_access = 0,
>>> + .port = self->port[2],
>>> + };
>>> +
>>> + const int ruleset_fd = landlock_create_ruleset(&ruleset_attr,
>>> + sizeof(ruleset_attr), 0);
>>> + ASSERT_LE(0, ruleset_fd);
>>> +
>>> + /* Allows connect and bind operations to the port[0] socket. */
>>
>> This comment is useful though because the below call is more complex.
>>
> So I can leave it as it's, cant I?
Yes, keep it, I'd just like a fair amount of useful comments. ;)
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