Hello! This is v3 RFC patch dedicated to socket protocols restriction. It is based on the landlock's mic-next branch on top of v6.11-rc1 kernel version. Objective ========= Extend Landlock with a mechanism to restrict any set of protocols in a sandboxed process. Closes: https://github.com/landlock-lsm/linux/issues/6 Motivation ========== Landlock implements the `LANDLOCK_RULE_NET_PORT` rule type, which provides fine-grained control of actions for a specific protocol. Any action or protocol that is not supported by this rule can not be controlled. As a result, protocols for which fine-grained control is not supported can be used in a sandboxed system and lead to vulnerabilities or unexpected behavior. Controlling the protocols used will allow to use only those that are necessary for the system and/or which have fine-grained Landlock control through others types of rules (e.g. TCP bind/connect control with `LANDLOCK_RULE_NET_PORT`, UNIX bind control with `LANDLOCK_RULE_PATH_BENEATH`). Consider following examples: * Server may want to use only TCP sockets for which there is fine-grained control of bind(2) and connect(2) actions [1]. * System that does not need a network or that may want to disable network for security reasons (e.g. [2]) can achieve this by restricting the use of all possible protocols. [1] https://lore.kernel.org/all/ZJvy2SViorgc+cZI@xxxxxxxxxx/ [2] https://cr.yp.to/unix/disablenetwork.html Implementation ============== This patchset adds control over the protocols used by implementing a restriction of socket creation. This is possible thanks to the new type of rule - `LANDLOCK_RULE_SOCKET`, that allows to restrict actions on sockets, and a new access right - `LANDLOCK_ACCESS_SOCKET_CREATE`, that corresponds to creating user space sockets. The key in this rule is a pair of address family and socket type (Cf. socket(2)). The right to create a socket is checked in the LSM hook, which is called in the __sock_create method. The following user space operations are subject to this check: socket(2), socketpair(2), io_uring(7). In the case of connection-based socket types, `LANDLOCK_ACCESS_SOCKET_CREATE` does not restrict the actions that result in creation of sockets used for messaging between already existing endpoints (e.g. accept(2), setsockopt(2) with option `SCTP_SOCKOPT_PEELOFF`). Current limitations =================== `SCTP_SOCKOPT_PEELOFF` should not be restricted (see test socket_creation.sctp_peeloff). SCTP socket can be connected to a multiple endpoints (one-to-many relation). Calling setsockopt(2) on such socket with option `SCTP_SOCKOPT_PEELOFF` detaches one of existing connections to a separate UDP socket. This detach is currently restrictable. Code coverage ============= Code coverage(gcov) report with the launch of all the landlock selftests: * security/landlock: lines......: 93.5% (794 of 849 lines) functions..: 95.5% (106 of 111 functions) * security/landlock/socket.c: lines......: 100.0% (33 of 33 lines) functions..: 100.0% (4 of 4 functions) General changes v2->v3 ====================== * Implementation * Accepts (AF_INET, SOCK_PACKET) as an alias for (AF_PACKET, SOCK_PACKET). * Adds check to not restrict kernel sockets. * Fixes UB in pack_socket_key(). * Refactors documentation. * Tests * Extends variants of `protocol` fixture with every protocol that can be used to create user space sockets. * Adds 5 new tests: * 3 tests to check socketpair(2), accept(2) and sctp_peeloff restriction. * 1 test to check restriction of kernel sockets. * 1 test to check AF_PACKET aliases. * Documentation * Updates Documentation/userspace-api/landlock.rst. * Commits * Rebases on mic-next. * Refactors commits. Previous versions ================= v2: https://lore.kernel.org/all/20240524093015.2402952-1-ivanov.mikhail1@xxxxxxxxxxxxxxxxxxx/ v1: https://lore.kernel.org/all/20240408093927.1759381-1-ivanov.mikhail1@xxxxxxxxxxxxxxxxxxx/ Mikhail Ivanov (19): landlock: Support socket access-control landlock: Add hook on socket creation selftests/landlock: Test basic socket restriction selftests/landlock: Test adding a rule with each supported access selftests/landlock: Test adding a rule for each unknown access selftests/landlock: Test adding a rule for unhandled access selftests/landlock: Test adding a rule for empty access selftests/landlock: Test overlapped restriction selftests/landlock: Test creating a ruleset with unknown access selftests/landlock: Test adding a rule with family and type outside the range selftests/landlock: Test unsupported protocol restriction selftests/landlock: Test that kernel space sockets are not restricted selftests/landlock: Test packet protocol alias selftests/landlock: Test socketpair(2) restriction selftests/landlock: Test SCTP peeloff restriction selftests/landlock: Test that accept(2) is not restricted samples/landlock: Replace atoi() with strtoull() in populate_ruleset_net() samples/landlock: Support socket protocol restrictions landlock: Document socket rule type support Documentation/userspace-api/landlock.rst | 46 +- include/uapi/linux/landlock.h | 61 +- samples/landlock/sandboxer.c | 135 ++- security/landlock/Makefile | 2 +- security/landlock/limits.h | 4 + security/landlock/ruleset.c | 33 +- security/landlock/ruleset.h | 45 +- security/landlock/setup.c | 2 + security/landlock/socket.c | 137 +++ security/landlock/socket.h | 19 + security/landlock/syscalls.c | 66 +- tools/testing/selftests/landlock/base_test.c | 2 +- tools/testing/selftests/landlock/common.h | 13 + tools/testing/selftests/landlock/config | 47 + tools/testing/selftests/landlock/net_test.c | 11 - .../testing/selftests/landlock/socket_test.c | 1013 +++++++++++++++++ 16 files changed, 1593 insertions(+), 43 deletions(-) create mode 100644 security/landlock/socket.c create mode 100644 security/landlock/socket.h create mode 100644 tools/testing/selftests/landlock/socket_test.c base-commit: 8400291e289ee6b2bf9779ff1c83a291501f017b -- 2.34.1
