This commit adds network demo. It's possible to allow a sandboxer to bind/connect to a list of particular ports restricting network actions to the rest of ports. Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@xxxxxxxxxx> Link: https://lore.kernel.org/r/20230920092641.832134-12-konstantin.meskhidze@xxxxxxxxxx [mic: Define __SANE_USERSPACE_TYPES__ to select int-ll64.h and avoid format warnings for PowerPC] Signed-off-by: Mickaël Salaün <mic@xxxxxxxxxxx> --- Changes since v12: * Defines __SANE_USERSPACE_TYPES__ to avoid warnings for PowerPC. Changes since v11: * Changes ENV_PATH_TOKEN to ENV_DELIMITER. * Refactors populate_ruleset_net(): - Deletes parse_port_num() helper. - Uses strsep() instead of strtok(). * Fixes wrong printf format. Changes since v10: * Refactors populate_ruleset_net() helper. * Code style minor fix. Changes since v9: * Deletes ports converting. * Minor fixes. Changes since v8: * Convert ports to __be16. * Minor fixes. Changes since v7: * Removes network support if ABI < 4. * Removes network support if not set by a user. Changes since v6: * Removes network support if ABI < 3. Changes since v5: * Makes network ports sandboxing optional. * Fixes some logic errors. * Formats code with clang-format-14. Changes since v4: * Adds ENV_TCP_BIND_NAME "LL_TCP_BIND" and ENV_TCP_CONNECT_NAME "LL_TCP_CONNECT" variables to insert TCP ports. * Renames populate_ruleset() to populate_ruleset_fs(). * Adds populate_ruleset_net() and parse_port_num() helpers. * Refactors main() to support network sandboxing. --- samples/landlock/sandboxer.c | 115 ++++++++++++++++++++++++++++++----- 1 file changed, 100 insertions(+), 15 deletions(-) diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c index e2056c8b902c..08596c0ef070 100644 --- a/samples/landlock/sandboxer.c +++ b/samples/landlock/sandboxer.c @@ -8,6 +8,8 @@ */ #define _GNU_SOURCE +#define __SANE_USERSPACE_TYPES__ +#include <arpa/inet.h> #include <errno.h> #include <fcntl.h> #include <linux/landlock.h> @@ -51,7 +53,9 @@ static inline int landlock_restrict_self(const int ruleset_fd, #define ENV_FS_RO_NAME "LL_FS_RO" #define ENV_FS_RW_NAME "LL_FS_RW" -#define ENV_PATH_TOKEN ":" +#define ENV_TCP_BIND_NAME "LL_TCP_BIND" +#define ENV_TCP_CONNECT_NAME "LL_TCP_CONNECT" +#define ENV_DELIMITER ":" static int parse_path(char *env_path, const char ***const path_list) { @@ -60,13 +64,13 @@ static int parse_path(char *env_path, const char ***const path_list) if (env_path) { num_paths++; for (i = 0; env_path[i]; i++) { - if (env_path[i] == ENV_PATH_TOKEN[0]) + if (env_path[i] == ENV_DELIMITER[0]) num_paths++; } } *path_list = malloc(num_paths * sizeof(**path_list)); for (i = 0; i < num_paths; i++) - (*path_list)[i] = strsep(&env_path, ENV_PATH_TOKEN); + (*path_list)[i] = strsep(&env_path, ENV_DELIMITER); return num_paths; } @@ -81,8 +85,8 @@ static int parse_path(char *env_path, const char ***const path_list) /* clang-format on */ -static int populate_ruleset(const char *const env_var, const int ruleset_fd, - const __u64 allowed_access) +static int populate_ruleset_fs(const char *const env_var, const int ruleset_fd, + const __u64 allowed_access) { int num_paths, i, ret = 1; char *env_path_name; @@ -143,6 +147,39 @@ static int populate_ruleset(const char *const env_var, const int ruleset_fd, return ret; } +static int populate_ruleset_net(const char *const env_var, const int ruleset_fd, + const __u64 allowed_access) +{ + int ret = 1; + char *env_port_name, *strport; + struct landlock_net_port_attr net_port = { + .allowed_access = allowed_access, + .port = 0, + }; + + env_port_name = getenv(env_var); + if (!env_port_name) + return 0; + env_port_name = strdup(env_port_name); + unsetenv(env_var); + + while ((strport = strsep(&env_port_name, ENV_DELIMITER))) { + net_port.port = atoi(strport); + if (landlock_add_rule(ruleset_fd, LANDLOCK_RULE_NET_PORT, + &net_port, 0)) { + fprintf(stderr, + "Failed to update the ruleset with port \"%llu\": %s\n", + net_port.port, strerror(errno)); + goto out_free_name; + } + } + ret = 0; + +out_free_name: + free(env_port_name); + return ret; +} + /* clang-format off */ #define ACCESS_FS_ROUGHLY_READ ( \ @@ -166,39 +203,58 @@ static int populate_ruleset(const char *const env_var, const int ruleset_fd, /* clang-format on */ -#define LANDLOCK_ABI_LAST 3 +#define LANDLOCK_ABI_LAST 4 int main(const int argc, char *const argv[], char *const *const envp) { const char *cmd_path; char *const *cmd_argv; int ruleset_fd, abi; + char *env_port_name; __u64 access_fs_ro = ACCESS_FS_ROUGHLY_READ, access_fs_rw = ACCESS_FS_ROUGHLY_READ | ACCESS_FS_ROUGHLY_WRITE; + struct landlock_ruleset_attr ruleset_attr = { .handled_access_fs = access_fs_rw, + .handled_access_net = LANDLOCK_ACCESS_NET_BIND_TCP | + LANDLOCK_ACCESS_NET_CONNECT_TCP, }; if (argc < 2) { fprintf(stderr, - "usage: %s=\"...\" %s=\"...\" %s <cmd> [args]...\n\n", - ENV_FS_RO_NAME, ENV_FS_RW_NAME, argv[0]); + "usage: %s=\"...\" %s=\"...\" %s=\"...\" %s=\"...\"%s " + "<cmd> [args]...\n\n", + ENV_FS_RO_NAME, ENV_FS_RW_NAME, ENV_TCP_BIND_NAME, + ENV_TCP_CONNECT_NAME, argv[0]); fprintf(stderr, "Launch a command in a restricted environment.\n\n"); - fprintf(stderr, "Environment variables containing paths, " - "each separated by a colon:\n"); + fprintf(stderr, + "Environment variables containing paths and ports " + "each separated by a colon:\n"); fprintf(stderr, "* %s: list of paths allowed to be used in a read-only way.\n", ENV_FS_RO_NAME); fprintf(stderr, - "* %s: list of paths allowed to be used in a read-write way.\n", + "* %s: list of paths allowed to be used in a read-write way.\n\n", ENV_FS_RW_NAME); + fprintf(stderr, + "Environment variables containing ports are optional " + "and could be skipped.\n"); + fprintf(stderr, + "* %s: list of ports allowed to bind (server).\n", + ENV_TCP_BIND_NAME); + fprintf(stderr, + "* %s: list of ports allowed to connect (client).\n", + ENV_TCP_CONNECT_NAME); fprintf(stderr, "\nexample:\n" "%s=\"/bin:/lib:/usr:/proc:/etc:/dev/urandom\" " "%s=\"/dev/null:/dev/full:/dev/zero:/dev/pts:/tmp\" " + "%s=\"9418\" " + "%s=\"80:443\" " "%s bash -i\n\n", - ENV_FS_RO_NAME, ENV_FS_RW_NAME, argv[0]); + ENV_FS_RO_NAME, ENV_FS_RW_NAME, ENV_TCP_BIND_NAME, + ENV_TCP_CONNECT_NAME, argv[0]); fprintf(stderr, "This sandboxer can use Landlock features " "up to ABI version %d.\n", @@ -255,7 +311,12 @@ int main(const int argc, char *const argv[], char *const *const envp) case 2: /* Removes LANDLOCK_ACCESS_FS_TRUNCATE for ABI < 3 */ ruleset_attr.handled_access_fs &= ~LANDLOCK_ACCESS_FS_TRUNCATE; - + __attribute__((fallthrough)); + case 3: + /* Removes network support for ABI < 4 */ + ruleset_attr.handled_access_net &= + ~(LANDLOCK_ACCESS_NET_BIND_TCP | + LANDLOCK_ACCESS_NET_CONNECT_TCP); fprintf(stderr, "Hint: You should update the running kernel " "to leverage Landlock features " @@ -274,18 +335,42 @@ int main(const int argc, char *const argv[], char *const *const envp) access_fs_ro &= ruleset_attr.handled_access_fs; access_fs_rw &= ruleset_attr.handled_access_fs; + /* Removes bind access attribute if not supported by a user. */ + env_port_name = getenv(ENV_TCP_BIND_NAME); + if (!env_port_name) { + ruleset_attr.handled_access_net &= + ~LANDLOCK_ACCESS_NET_BIND_TCP; + } + /* Removes connect access attribute if not supported by a user. */ + env_port_name = getenv(ENV_TCP_CONNECT_NAME); + if (!env_port_name) { + ruleset_attr.handled_access_net &= + ~LANDLOCK_ACCESS_NET_CONNECT_TCP; + } + ruleset_fd = landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0); if (ruleset_fd < 0) { perror("Failed to create a ruleset"); return 1; } - if (populate_ruleset(ENV_FS_RO_NAME, ruleset_fd, access_fs_ro)) { + + if (populate_ruleset_fs(ENV_FS_RO_NAME, ruleset_fd, access_fs_ro)) { + goto err_close_ruleset; + } + if (populate_ruleset_fs(ENV_FS_RW_NAME, ruleset_fd, access_fs_rw)) { goto err_close_ruleset; } - if (populate_ruleset(ENV_FS_RW_NAME, ruleset_fd, access_fs_rw)) { + + if (populate_ruleset_net(ENV_TCP_BIND_NAME, ruleset_fd, + LANDLOCK_ACCESS_NET_BIND_TCP)) { + goto err_close_ruleset; + } + if (populate_ruleset_net(ENV_TCP_CONNECT_NAME, ruleset_fd, + LANDLOCK_ACCESS_NET_CONNECT_TCP)) { goto err_close_ruleset; } + if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) { perror("Failed to restrict privileges"); goto err_close_ruleset; -- 2.25.1
