On 31/03/2023 19:24, Mickaël Salaün wrote:
On 23/03/2023 09:52, Konstantin Meskhidze wrote:This commit adds network rules support in the ruleset management helpers and the landlock_create_ruleset syscall. Refactor user space API to support network actions. Add new network access flags, network rule and network attributes. Increment Landlock ABI version. Expand access_masks_t to u32 to be sure network access rights can be stored. Implement socket_bind() and socket_connect() LSM hooks, which enable to restrict TCP socket binding and connection to specific ports. Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@xxxxxxxxxx> --- Changes since v9: * Changes UAPI port field to __u64. * Moves shared code into check_socket_access(). * Adds get_raw_handled_net_accesses() and get_current_net_domain() helpers. * Minor fixes. Changes since v8: * Squashes commits. * Refactors commit message. * Changes UAPI port field to __be16. * Changes logic of bind/connect hooks with AF_UNSPEC families. * Adds address length checking. * Minor fixes. Changes since v7: * Squashes commits. * Increments ABI version to 4. * Refactors commit message. * Minor fixes. Changes since v6: * Renames landlock_set_net_access_mask() to landlock_add_net_access_mask() because it OR values. * Makes landlock_add_net_access_mask() more resilient incorrect values. * Refactors landlock_get_net_access_mask(). * Renames LANDLOCK_MASK_SHIFT_NET to LANDLOCK_SHIFT_ACCESS_NET and use LANDLOCK_NUM_ACCESS_FS as value. * Updates access_masks_t to u32 to support network access actions. * Refactors landlock internal functions to support network actions with landlock_key/key_type/id types. Changes since v5: * Gets rid of partial revert from landlock_add_rule syscall. * Formats code with clang-format-14. Changes since v4: * Refactors landlock_create_ruleset() - splits ruleset and masks checks. * Refactors landlock_create_ruleset() and landlock mask setters/getters to support two rule types. * Refactors landlock_add_rule syscall add_rule_path_beneath function by factoring out get_ruleset_from_fd() and landlock_put_ruleset(). Changes since v3: * Splits commit. * Adds network rule support for internal landlock functions. * Adds set_mask and get_mask for network. * Adds rb_root root_net_port. --- include/uapi/linux/landlock.h | 49 +++++ security/landlock/Kconfig | 1 + security/landlock/Makefile | 2 + security/landlock/limits.h | 6 +- security/landlock/net.c | 198 +++++++++++++++++++ security/landlock/net.h | 26 +++ security/landlock/ruleset.c | 52 ++++- security/landlock/ruleset.h | 63 +++++- security/landlock/setup.c | 2 + security/landlock/syscalls.c | 72 ++++++- tools/testing/selftests/landlock/base_test.c | 2 +- 11 files changed, 450 insertions(+), 23 deletions(-) create mode 100644 security/landlock/net.c create mode 100644 security/landlock/net.h[...]diff --git a/security/landlock/net.c b/security/landlock/net.c[...]+static int check_addrlen(const struct sockaddr *const address, int addrlen)const int addrlen+{ + if (addrlen < offsetofend(struct sockaddr, sa_family)) + return -EINVAL; + switch (address->sa_family) { + case AF_UNSPEC: + case AF_INET: + if (addrlen < sizeof(struct sockaddr_in)) + return -EINVAL; + return 0; +#if IS_ENABLED(CONFIG_IPV6) + case AF_INET6: + if (addrlen < SIN6_LEN_RFC2133) + return -EINVAL; + return 0; +#endif + } + WARN_ON_ONCE(1); + return 0; +} + +static u16 get_port(const struct sockaddr *const address) +{ + /* Gets port value in host byte order. */ + switch (address->sa_family) { + case AF_UNSPEC: + case AF_INET: { + const struct sockaddr_in *const sockaddr = + (struct sockaddr_in *)address; + return ntohs(sockaddr->sin_port);Storing ports in big endian (in rulesets) would avoid converting them every time the kernel checks a socket port. The above comment should then be updated too.
You can then return a __be16 type here and at least also use __be16 in check_socket_access().
+ } +#if IS_ENABLED(CONFIG_IPV6) + case AF_INET6: { + const struct sockaddr_in6 *const sockaddr_ip6 = + (struct sockaddr_in6 *)address; + return ntohs(sockaddr_ip6->sin6_port); + } +#endif + } + WARN_ON_ONCE(1); + return 0; +} + +static int check_socket_access(struct socket *sock, struct sockaddr *address, int addrlen, u16 port, + access_mask_t access_request) +{ + int ret; + bool allowed = false; + layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_NET] = {}; + const struct landlock_rule *rule; + access_mask_t handled_access; + const struct landlock_id id = { + .key.data = port, + .type = LANDLOCK_KEY_NET_PORT, + }; + const struct landlock_ruleset *const domain = get_current_net_domain(); + + if (WARN_ON_ONCE(!domain)) + return 0; + if (WARN_ON_ONCE(domain->num_layers < 1)) + return -EACCES; + /* Check if it's a TCP socket. */ + if (sock->type != SOCK_STREAM) + return 0; + + ret = check_addrlen(address, addrlen); + if (ret) + return ret; + + switch (address->sa_family) { + case AF_UNSPEC: + /* + * Connecting to an address with AF_UNSPEC dissolves the TCP + * association, which have the same effect as closing the + * connection while retaining the socket object (i.e., the file + * descriptor). As for dropping privileges, closing + * connections is always allowed. + */ + if (access_request == LANDLOCK_ACCESS_NET_CONNECT_TCP) + return 0; + + /* + * For compatibility reason, accept AF_UNSPEC for bind + * accesses (mapped to AF_INET) only if the address is + * INADDR_ANY (cf. __inet_bind). Checking the address is + * required to not wrongfully return -EACCES instead of + * -EAFNOSUPPORT. + */ + if (access_request == LANDLOCK_ACCESS_NET_BIND_TCP) { + const struct sockaddr_in *const sockaddr = + (struct sockaddr_in *)address; + + if (sockaddr->sin_addr.s_addr != htonl(INADDR_ANY)) + return -EAFNOSUPPORT; + } + + fallthrough; + case AF_INET: +#if IS_ENABLED(CONFIG_IPV6) + case AF_INET6: +#endif + rule = landlock_find_rule(domain, id); + handled_access = landlock_init_layer_masks( + domain, access_request, &layer_masks, + LANDLOCK_KEY_NET_PORT); + allowed = landlock_unmask_layers(rule, handled_access, + &layer_masks, + ARRAY_SIZE(layer_masks)); + } + return allowed ? 0 : -EACCES; +} + +static int hook_socket_bind(struct socket *sock, struct sockaddr *address, + int addrlen) +{ + return check_socket_access(sock, address, addrlen, get_port(address), + LANDLOCK_ACCESS_NET_BIND_TCP); +} + +static int hook_socket_connect(struct socket *sock, struct sockaddr *address, + int addrlen) +{ + return check_socket_access(sock, address, addrlen, get_port(address), + LANDLOCK_ACCESS_NET_CONNECT_TCP); +}[...]
