Date:   Mon, 7 Feb 2022 10:11:08 +0300
From:   Konstantin Meskhidze <konstantin.meskhidze@...wei.com>
To:     Mickaël Salaün <mic@...ikod.net>
CC:     <linux-security-module@...r.kernel.org>, <netdev@...r.kernel.org>,
        <netfilter@...r.kernel.org>, <yusongping@...wei.com>,
        <artem.kuzin@...wei.com>
Subject: Re: [RFC PATCH 2/2] landlock: selftests for bind and connect hooks



2/1/2022 9:31 PM, Mickaël Salaün пишет:
> 
> On 24/01/2022 09:02, Konstantin Meskhidze wrote:
>> Support 4 tests for bind and connect networks actions:
> 
> Good to see such tests!
> 
> 
>> 1. bind() a socket with no landlock restrictions.
>> 2. bind() sockets with landllock restrictions.
> 
> You can leverage the FIXTURE_VARIANT helpers to factor out this kind of 
> tests (see ptrace_test.c).

  Thanks. I will check this out.
> 
> 
>> 3. connect() a socket to listening one with no landlock restricitons.
>> 4. connect() sockets with landlock restrictions.
> 
> Same here, you can factor out code. I guess you could create helpers for 
> client and server parts.

   Ok. I got it.
> 
> We also need to test with IPv4, IPv6 and the AF_UNSPEC tricks.

   Yep. I will add AF_UNSPEC case.
> 
> Please provide the kernel test coverage and explain why the uncovered 
> code cannot be covered: 
> https://www.kernel.org/doc/html/latest/dev-tools/gcov.html

   Thanks for the link. I will check it out.
> 
> You'll probably see that there are a multiple parts of the kernel that 
> are not covered. For instance, it is important to test different 
> combinations of layered network rules (see layout1/ruleset_overlap, 
> layer_rule_unions, non_overlapping_accesses, 
> interleaved_masked_accesses… in fs_test.c). Tests in fs_test.c are more 
> complex because handling file system rules is more complex, but you can 
> get some inspiration in it, especially the edge cases.

   I got your point. I agree that we need to cover as many network rules
   combinations as possible.
> 
> We also need to test invalid user space supplied data (see layout1/inval 
> test in fs_test.c).

   Ok. I will add this kind of test. Thanks.
> 
> 
>>
>> Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@...wei.com>
>> ---
>>   .../testing/selftests/landlock/network_test.c | 346 ++++++++++++++++++
>>   1 file changed, 346 insertions(+)
>>   create mode 100644 tools/testing/selftests/landlock/network_test.c
>>
>> diff --git a/tools/testing/selftests/landlock/network_test.c 
>> b/tools/testing/selftests/landlock/network_test.c
>> new file mode 100644
>> index 000000000000..9dfe37a2fb20
>> --- /dev/null
>> +++ b/tools/testing/selftests/landlock/network_test.c
>> @@ -0,0 +1,346 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Landlock tests - Common user space base
>> + *
>> + * Copyright © 2017-2020 Mickaël Salaün <mic@...ikod.net>
>> + * Copyright © 2019-2020 ANSSI
> 
> You need to update this header with an appropriate description and the 
> copyright holder (your employer).
> 
   Ok. I got it.
> 
>> + */
>> +
>> +#define _GNU_SOURCE
>> +#include <errno.h>
>> +#include <fcntl.h>
>> +#include <linux/landlock.h>
>> +#include <string.h>
>> +#include <sys/prctl.h>
>> +#include <sys/socket.h>
>> +#include <sys/types.h>
>> +#include <netinet/in.h>
>> +#include <arpa/inet.h>
> 
> To make it determinisitic (and ease patching/diff/merging), you should 
> sort all the included files (in tests and in the kernel code).

   Sorry. Did not get your point here. Could you explain in a bit more
   details please.
> 
> 
>> +
>> +#include "common.h"
>> +
>> +#define SOCK_PORT_1 3470
>> +#define SOCK_PORT_2 3480
>> +#define SOCK_PORT_3 3490
> 
> To avoid port collision and create a clean and stable test environement 
> (to avoid flaky tests), you should create a network namespace with 
> FIXTURE_SETUP, test with TEST_F_FORK (to not polute the parent process, 
> and which works with test variants), and use the set_cap and clear_cap 
> helpers (see fs_test.c).

   Ok. I got it.
> 
> 
>> +
>> +#define IP_ADDRESS "127.0.0.1"
>> +
>> +/* Number pending connections queue tobe hold */
>> +#define BACKLOG 10
>> +
>> +TEST(socket_bind_no_restrictions) {
>> +
>> +    int sockfd;
>> +    struct sockaddr_in addr;
>> +    const int one = 1;
>> +
>> +    /* Create a socket */
>> +    sockfd = socket(AF_INET, SOCK_STREAM, 0);
>> +    ASSERT_LE(0, sockfd);
>> +    /* Allow reuse of local addresses */
>> +    ASSERT_EQ(0, setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &one, 
>> sizeof(one)));
> 
> With a dedicated namespace, SO_REUSEADDR should not be required.

   Yes. I agree. Will be refactored.
> 
> 
>> +
>> +    /* Set socket address parameters */
>> +    addr.sin_family = AF_INET;
>> +    addr.sin_port = htons(SOCK_PORT_1);
>> +    addr.sin_addr.s_addr = inet_addr(IP_ADDRESS);
>> +    memset(&(addr.sin_zero), '\0', 8);
>> +
>> +    /* Bind the socket to IP address */
>> +    ASSERT_EQ(0, bind(sockfd, (struct sockaddr *)&addr, sizeof(addr)));
>> +}
>> +
>> +TEST(sockets_bind_with_restrictions) {
>> +
>> +    int sockfd_1, sockfd_2, sockfd_3;
>> +    struct sockaddr_in addr_1, addr_2, addr_3;
>> +    const int one = 1;
>> +
>> +    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 = SOCK_PORT_1,
>> +    };
>> +    struct landlock_net_service_attr net_service_2 = {
>> +        .allowed_access = LANDLOCK_ACCESS_NET_CONNECT_TCP,
>> +        .port = SOCK_PORT_2,
>> +    };
>> +    struct landlock_net_service_attr net_service_3 = {
>> +        .allowed_access = 0,
>> +        .port = SOCK_PORT_3,
>> +    };
> 
> Good to have these three different rules!
> 
> 
>> +
>> +    const int ruleset_fd = landlock_create_ruleset(&ruleset_attr,
>> +            sizeof(ruleset_attr), 0);
>> +    ASSERT_LE(0, ruleset_fd);
>> +
>> +    /* Allow connect and bind operations to the SOCK_PORT_1 socket 
>> "object" */
> 
> You can omit "object" but use full sentences at the third person 
> (because it explains what do the next lines).

   Ok. I got it.
> 
> 
>> +    ASSERT_EQ(0, landlock_add_rule(ruleset_fd, 
>> LANDLOCK_RULE_NET_SERVICE,
>> +                &net_service_1, 0));
>> +    /* Allow connect and deny bind operations to the SOCK_PORT_2 
>> socket "object" */
>> +    ASSERT_EQ(0, landlock_add_rule(ruleset_fd, 
>> LANDLOCK_RULE_NET_SERVICE,
>> +                &net_service_2, 0));
>> +    /* Empty allowed_access (i.e. deny rules) are ignored in network 
>> actions
>> +     * for SOCK_PORT_3 socket "object"
>> +     */
>> +    ASSERT_EQ(-1, landlock_add_rule(ruleset_fd, 
>> LANDLOCK_RULE_NET_SERVICE,
>> +                &net_service_3, 0));
>> +    ASSERT_EQ(ENOMSG, errno);
>> +
>> +    /* Enforces the ruleset. */
>> +    ASSERT_EQ(0, prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0));
>> +    ASSERT_EQ(0, landlock_restrict_self(ruleset_fd, 0));
>> +    ASSERT_EQ(0, close(ruleset_fd));
>> +
>> +    /* Create a socket 1 */
>> +    sockfd_1 = socket(AF_INET, SOCK_STREAM, 0);
> 
> Please create all FD with SOCK_CLOEXEC and also close them when not 
> needed. This could also reduce the number of FD.

   Ok. Thanks for noticing. It makes sense.
> 
> 
>> +    ASSERT_LE(0, sockfd_1);
>> +    /* Allow reuse of local addresses */
>> +    ASSERT_EQ(0, setsockopt(sockfd_1, SOL_SOCKET, SO_REUSEADDR, &one, 
>> sizeof(one)));
>> +
>> +    /* Set socket 1 address parameters */
>> +    addr_1.sin_family = AF_INET;
>> +    addr_1.sin_port = htons(SOCK_PORT_1);
>> +    addr_1.sin_addr.s_addr = inet_addr(IP_ADDRESS);
>> +    memset(&(addr_1.sin_zero), '\0', 8);
>> +    /* Bind the socket 1 to IP address */
>> +    ASSERT_EQ(0, bind(sockfd_1, (struct sockaddr  *)&addr_1, 
>> sizeof(addr_1)));
>> +
>> +    /* Create a socket 2 */
>> +    sockfd_2 = socket(AF_INET, SOCK_STREAM, 0);
>> +    ASSERT_LE(0, sockfd_2);
>> +    /* Allow reuse of local addresses */
>> +    ASSERT_EQ(0, setsockopt(sockfd_2, SOL_SOCKET, SO_REUSEADDR, &one, 
>> sizeof(one)));
>> +
>> +    /* Set socket 2 address parameters */
>> +    addr_2.sin_family = AF_INET;
>> +    addr_2.sin_port = htons(SOCK_PORT_2);
>> +    addr_2.sin_addr.s_addr = inet_addr(IP_ADDRESS);
>> +    memset(&(addr_2.sin_zero), '\0', 8);
> 
> These part could be factored out with helpers or/and test variants.

   Thanks. Will be factored out.
> 
> 
>> +    /* Bind the socket 2 to IP address */
>> +    ASSERT_EQ(-1, bind(sockfd_2, (struct sockaddr *)&addr_2, 
>> sizeof(addr_2)));
>> +    ASSERT_EQ(EACCES, errno);
>> +
>> +    /* Create a socket 3 */
>> +    sockfd_3 = socket(AF_INET, SOCK_STREAM, 0);
>> +    ASSERT_LE(0, sockfd_3);
>> +    /* Allow reuse of local addresses */
>> +    ASSERT_EQ(0, setsockopt(sockfd_3, SOL_SOCKET, SO_REUSEADDR, &one, 
>> sizeof(one)));
>> +
>> +    /* Set socket 3 address parameters */
>> +    addr_3.sin_family = AF_INET;
>> +    addr_3.sin_port = htons(SOCK_PORT_3);
>> +    addr_3.sin_addr.s_addr = inet_addr(IP_ADDRESS);
>> +    memset(&(addr_3.sin_zero), '\0', 8);
>> +    /* Bind the socket 3 to IP address */
>> +    ASSERT_EQ(0, bind(sockfd_3, (struct sockaddr *)&addr_3, 
>> sizeof(addr_3)));
> 
> Why is it allowed to bind to SOCK_PORT_3 whereas net_service_3 forbids it?

   It's allowed cause net_service_3 has empty access field.

    /* Empty allowed_access (i.e. deny rules) are ignored in network
     *  actions for SOCK_PORT_3 socket "object"
     */
     ASSERT_EQ(-1, landlock_add_rule(ruleset_fd,
                                     LANDLOCK_RULE_NET_SERVICE,
                                     &net_service_3, 0));
     ASSERT_EQ(ENOMSG, errno);

   Applying this rule returns ENOMSG errno:

   /* Informs about useless rule: empty allowed_access (i.e. deny rules)
    * are ignored in network actions
    */
		if (!net_service_attr.allowed_access) {
			err = -ENOMSG;
			goto out_put_ruleset;
		}
   This means binding socket 3 is not restricted.
   For path_beneath_attr.allowed_access = 0 there is the same logic.
> 
> 
>> +}
>> +
>> +TEST(socket_connect_no_restrictions) {
>> +
>> +    int sockfd, new_fd;
>> +    struct sockaddr_in addr;
>> +    pid_t child;
>> +    int status;
>> +    const int one = 1;
>> +
>> +    /* Create a server socket */
>> +    sockfd = socket(AF_INET, SOCK_STREAM, 0);
>> +    ASSERT_LE(0, sockfd);
>> +    /* Allow reuse of local addresses */
>> +    ASSERT_EQ(0, setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &one, 
>> sizeof(one)));
>> +
>> +    /* Set socket address parameters */
>> +    addr.sin_family = AF_INET;
>> +    addr.sin_port = htons(SOCK_PORT_1);
>> +    addr.sin_addr.s_addr = inet_addr(IP_ADDRESS);
>> +    memset(&(addr.sin_zero), '\0', 8);
>> +
>> +    /* Bind the socket to IP address */
>> +    ASSERT_EQ(0, bind(sockfd, (struct sockaddr *)&addr, sizeof(addr)));
>> +
>> +    /* Make listening socket */
>> +    ASSERT_EQ(0, listen(sockfd, BACKLOG));
>> +
>> +    child = fork();
>> +    ASSERT_LE(0, child);
>> +    if (child == 0) {
>> +        int child_sockfd;
>> +        struct sockaddr_in connect_addr;
>> +
>> +        /* Close listening socket for the child */
>> +        ASSERT_EQ(0, close(sockfd));
>> +        /* Create a stream client socket */
>> +        child_sockfd = socket(AF_INET, SOCK_STREAM, 0);
>> +        ASSERT_LE(0, child_sockfd);
>> +
>> +        /* Set server's socket address parameters*/
>> +        connect_addr.sin_family = AF_INET;
>> +        connect_addr.sin_port = htons(SOCK_PORT_1);
>> +        connect_addr.sin_addr.s_addr = htonl(INADDR_ANY);
>> +        memset(&(connect_addr.sin_zero), '\0', 8);
>> +
>> +        /* Make connection to the listening socket */
>> +        ASSERT_EQ(0, connect(child_sockfd, (struct sockaddr 
>> *)&connect_addr,
>> +                       sizeof(struct sockaddr)));
>> +        _exit(_metadata->passed ? EXIT_SUCCESS : EXIT_FAILURE);
>> +        return;
>> +    }
>> +    /* Accept connection from the child */
>> +    new_fd = accept(sockfd, NULL, 0);
>> +    ASSERT_LE(0, new_fd);
>> +
>> +    /* Close connection */
>> +    ASSERT_EQ(0, close(new_fd));
>> +
>> +    ASSERT_EQ(child, waitpid(child, &status, 0));
>> +    ASSERT_EQ(1, WIFEXITED(status));
>> +    ASSERT_EQ(EXIT_SUCCESS, WEXITSTATUS(status));
>> +}
>> +
>> +TEST(sockets_connect_with_restrictions) {
>> +
>> +    int new_fd;
>> +    int sockfd_1, sockfd_2;
>> +    struct sockaddr_in addr_1, addr_2;
>> +    pid_t child_1, child_2;
>> +    int status;
>> +    const int one = 1;
>> +
>> +    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 = SOCK_PORT_1,
>> +    };
>> +    struct landlock_net_service_attr net_service_2 = {
>> +        .allowed_access = LANDLOCK_ACCESS_NET_BIND_TCP,
>> +        .port = SOCK_PORT_2,
>> +    };
>> +
>> +    const int ruleset_fd = landlock_create_ruleset(&ruleset_attr,
>> +            sizeof(ruleset_attr), 0);
>> +    ASSERT_LE(0, ruleset_fd);
>> +
>> +    /* Allow connect and bind operations to the SOCK_PORT_1 socket 
>> "object" */
>> +    ASSERT_EQ(0, landlock_add_rule(ruleset_fd, 
>> LANDLOCK_RULE_NET_SERVICE,
>> +                &net_service_1, 0));
>> +    /* Allow connect and deny bind operations to the SOCK_PORT_2 
>> socket "object" */
>> +    ASSERT_EQ(0, landlock_add_rule(ruleset_fd, 
>> LANDLOCK_RULE_NET_SERVICE,
>> +                &net_service_2, 0));
>> +
>> +    /* Enforces the ruleset. */
>> +    ASSERT_EQ(0, prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0));
>> +    ASSERT_EQ(0, landlock_restrict_self(ruleset_fd, 0));
>> +    ASSERT_EQ(0, close(ruleset_fd));
>> +
>> +    /* Create a server socket 1 */
>> +    sockfd_1 = socket(AF_INET, SOCK_STREAM, 0);
>> +    ASSERT_LE(0, sockfd_1);
>> +    /* Allow reuse of local addresses */
>> +    ASSERT_EQ(0, setsockopt(sockfd_1, SOL_SOCKET, SO_REUSEADDR, &one, 
>> sizeof(one)));
>> +
>> +    /* Set socket 1 address parameters */
>> +    addr_1.sin_family = AF_INET;
>> +    addr_1.sin_port = htons(SOCK_PORT_1);
>> +    addr_1.sin_addr.s_addr = inet_addr(IP_ADDRESS);
>> +    memset(&(addr_1.sin_zero), '\0', 8);
>> +
>> +    /* Bind the socket 1 to IP address */
>> +    ASSERT_EQ(0, bind(sockfd_1, (struct sockaddr *)&addr_1, 
>> sizeof(addr_1)));
>> +
>> +    /* Make listening socket 1 */
>> +    ASSERT_EQ(0, listen(sockfd_1, BACKLOG));
>> +
>> +    child_1 = fork();
>> +    ASSERT_LE(0, child_1);
>> +    if (child_1 == 0) {
>> +        int child_sockfd;
>> +        struct sockaddr_in connect_addr;
>> +
>> +        /* Close listening socket for the child */
>> +        ASSERT_EQ(0, close(sockfd_1));
>> +        /* Create a stream client socket */
>> +        child_sockfd = socket(AF_INET, SOCK_STREAM, 0);
>> +        ASSERT_LE(0, child_sockfd);
>> +
>> +        /* Set server's socket 1 address parameters*/
>> +        connect_addr.sin_family = AF_INET;
>> +        connect_addr.sin_port = htons(SOCK_PORT_1);
>> +        connect_addr.sin_addr.s_addr = htonl(INADDR_ANY);
>> +        memset(&(connect_addr.sin_zero), '\0', 8);
>> +
>> +        /* Make connection to the listening socket 1 */
>> +        ASSERT_EQ(0, connect(child_sockfd, (struct sockaddr 
>> *)&connect_addr,
>> +                       sizeof(struct sockaddr)));
>> +        _exit(_metadata->passed ? EXIT_SUCCESS : EXIT_FAILURE);
>> +        return;
>> +    }
>> +    /* Accept connection from the child 1 */
>> +    new_fd = accept(sockfd_1, NULL, 0);
>> +    ASSERT_LE(0, new_fd);
>> +
>> +    /* Close connection */
>> +    ASSERT_EQ(0, close(new_fd));
>> +
>> +    ASSERT_EQ(child_1, waitpid(child_1, &status, 0));
>> +    ASSERT_EQ(1, WIFEXITED(status));
>> +    ASSERT_EQ(EXIT_SUCCESS, WEXITSTATUS(status));
>> +
>> +    /* Create a server socket 2 */
>> +    sockfd_2 = socket(AF_INET, SOCK_STREAM, 0);
>> +    ASSERT_LE(0, sockfd_2);
>> +    /* Allow reuse of local addresses */
>> +    ASSERT_EQ(0, setsockopt(sockfd_2, SOL_SOCKET, SO_REUSEADDR, &one, 
>> sizeof(one)));
>> +
>> +    /* Set socket 2 address parameters */
>> +    addr_2.sin_family = AF_INET;
>> +    addr_2.sin_port = htons(SOCK_PORT_2);
>> +    addr_2.sin_addr.s_addr = inet_addr(IP_ADDRESS);
>> +    memset(&(addr_2.sin_zero), '\0', 8);
>> +
>> +    /* Bind the socket 2 to IP address */
>> +    ASSERT_EQ(0, bind(sockfd_2, (struct sockaddr *)&addr_2, 
>> sizeof(addr_2)));
>> +
>> +    /* Make listening socket 2 */
>> +    ASSERT_EQ(0, listen(sockfd_2, BACKLOG));
>> +
>> +    child_2 = fork();
>> +    ASSERT_LE(0, child_2);
>> +    if (child_2 == 0) {
>> +        int child_sockfd;
>> +        struct sockaddr_in connect_addr;
>> +
>> +        /* Close listening socket for the child */
>> +        ASSERT_EQ(0, close(sockfd_2));
>> +        /* Create a stream client socket */
>> +        child_sockfd = socket(AF_INET, SOCK_STREAM, 0);
>> +        ASSERT_LE(0, child_sockfd);
>> +
>> +        /* Set server's socket address parameters*/
>> +        connect_addr.sin_family = AF_INET;
>> +        connect_addr.sin_port = htons(SOCK_PORT_2);
>> +        connect_addr.sin_addr.s_addr = htonl(INADDR_ANY);
>> +        memset(&(connect_addr.sin_zero), '\0', 8);
>> +
>> +        /* Make connection to the listening socket */
>> +        ASSERT_EQ(-1, connect(child_sockfd, (struct sockaddr 
>> *)&connect_addr,
>> +                       sizeof(struct sockaddr)));
>> +        ASSERT_EQ(EACCES, errno);
>> +        _exit(_metadata->passed ? EXIT_SUCCESS : EXIT_FAILURE);
>> +        return;
>> +    }
>> +
>> +    ASSERT_EQ(child_2, waitpid(child_2, &status, 0));
>> +    ASSERT_EQ(1, WIFEXITED(status));
>> +    ASSERT_EQ(EXIT_SUCCESS, WEXITSTATUS(status));
>> +}
>> +
>> +TEST_HARNESS_MAIN
> .

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