]> git.ipfire.org Git - thirdparty/linux.git/commitdiff
samples/landlock: Add quiet flag support to sandboxer
authorTingmao Wang <m@maowtm.org>
Fri, 12 Jun 2026 01:48:50 +0000 (02:48 +0100)
committerMickaël Salaün <mic@digikod.net>
Sun, 14 Jun 2026 18:17:20 +0000 (20:17 +0200)
Adds ability to set which access bits to quiet via LL_*_QUIET_ACCESS
(FS, NET or SCOPED), and attach quiet flags to individual objects via
LL_*_QUIET for FS and NET.

Assisted-by: GitHub-Copilot:claude-opus-4.8 copilot-reviepickw
Signed-off-by: Tingmao Wang <m@maowtm.org>
Link: https://patch.msgid.link/59b94997565032bc9870044f021214a2ed6df213.1781228815.git.m@maowtm.org
[mic: Fix comment formatting]
Signed-off-by: Mickaël Salaün <mic@digikod.net>
samples/landlock/sandboxer.c

index f44db2857bbf2bf0127dbc24d29b9894fef40c43..ac71019e62122af02d58c26cc86e1695fa0976c9 100644 (file)
@@ -58,9 +58,12 @@ 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_FS_QUIET_NAME "LL_FS_QUIET"
 #define ENV_TCP_BIND_NAME "LL_TCP_BIND"
 #define ENV_TCP_CONNECT_NAME "LL_TCP_CONNECT"
+#define ENV_NET_QUIET_NAME "LL_NET_QUIET"
 #define ENV_SCOPED_NAME "LL_SCOPED"
+#define ENV_QUIET_ACCESS_NAME "LL_QUIET_ACCESS"
 #define ENV_FORCE_LOG_NAME "LL_FORCE_LOG"
 #define ENV_UDP_BIND_NAME "LL_UDP_BIND"
 #define ENV_UDP_CONNECT_SEND_NAME "LL_UDP_CONNECT_SEND"
@@ -119,7 +122,7 @@ static int parse_path(char *env_path, const char ***const path_list)
 /* clang-format on */
 
 static int populate_ruleset_fs(const char *const env_var, const int ruleset_fd,
-                              const __u64 allowed_access)
+                              const __u64 allowed_access, __u32 flags)
 {
        int num_paths, i, ret = 1;
        char *env_path_name;
@@ -169,7 +172,7 @@ static int populate_ruleset_fs(const char *const env_var, const int ruleset_fd,
                if (!S_ISDIR(statbuf.st_mode))
                        path_beneath.allowed_access &= ACCESS_FILE;
                if (landlock_add_rule(ruleset_fd, LANDLOCK_RULE_PATH_BENEATH,
-                                     &path_beneath, 0)) {
+                                     &path_beneath, flags)) {
                        fprintf(stderr,
                                "Failed to update the ruleset with \"%s\": %s\n",
                                path_list[i], strerror(errno));
@@ -187,7 +190,7 @@ out_free_name:
 }
 
 static int populate_ruleset_net(const char *const env_var, const int ruleset_fd,
-                               const __u64 allowed_access)
+                               const __u64 allowed_access, __u32 flags)
 {
        int ret = 1;
        char *env_port_name, *env_port_name_next, *strport;
@@ -215,7 +218,7 @@ static int populate_ruleset_net(const char *const env_var, const int ruleset_fd,
                }
                net_port.port = port;
                if (landlock_add_rule(ruleset_fd, LANDLOCK_RULE_NET_PORT,
-                                     &net_port, 0)) {
+                                     &net_port, flags)) {
                        fprintf(stderr,
                                "Failed to update the ruleset with port \"%llu\": %s\n",
                                net_port.port, strerror(errno));
@@ -303,6 +306,69 @@ out_unset:
 
 /* clang-format on */
 
+/*
+ * Parses ENV_QUIET_ACCESS_NAME and sets the quiet_access_fs, quiet_access_net
+ * and quiet_scoped masks of @ruleset_attr accordingly.
+ */
+static int add_quiet_access(const char *const env_var,
+                           struct landlock_ruleset_attr *const ruleset_attr)
+{
+       char *env_quiet_access, *env_quiet_access_next, *str_access;
+
+       env_quiet_access = getenv(env_var);
+       if (!env_quiet_access)
+               return 0;
+
+       env_quiet_access = strdup(env_quiet_access);
+       env_quiet_access_next = env_quiet_access;
+       unsetenv(env_var);
+
+       while ((str_access = strsep(&env_quiet_access_next, ENV_DELIMITER))) {
+               if (strcmp(str_access, "") == 0)
+                       continue;
+               else if (strcmp(str_access, "all") == 0) {
+                       ruleset_attr->quiet_access_fs =
+                               ruleset_attr->handled_access_fs;
+                       ruleset_attr->quiet_access_net =
+                               ruleset_attr->handled_access_net;
+                       ruleset_attr->quiet_scoped = ruleset_attr->scoped;
+               } else if (strcmp(str_access, "read") == 0)
+                       ruleset_attr->quiet_access_fs |= ACCESS_FS_ROUGHLY_READ;
+               else if (strcmp(str_access, "write") == 0)
+                       ruleset_attr->quiet_access_fs |=
+                               ACCESS_FS_ROUGHLY_WRITE;
+               else if (strcmp(str_access, "tcp_bind") == 0)
+                       ruleset_attr->quiet_access_net |=
+                               LANDLOCK_ACCESS_NET_BIND_TCP;
+               else if (strcmp(str_access, "tcp_connect") == 0)
+                       ruleset_attr->quiet_access_net |=
+                               LANDLOCK_ACCESS_NET_CONNECT_TCP;
+               else if (strcmp(str_access, "udp_bind") == 0)
+                       ruleset_attr->quiet_access_net |=
+                               LANDLOCK_ACCESS_NET_BIND_UDP;
+               else if (strcmp(str_access, "udp_connect") == 0)
+                       ruleset_attr->quiet_access_net |=
+                               LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP;
+               else if (strcmp(str_access, "abstract_unix_socket") == 0)
+                       ruleset_attr->quiet_scoped |=
+                               LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET;
+               else if (strcmp(str_access, "signal") == 0)
+                       ruleset_attr->quiet_scoped |= LANDLOCK_SCOPE_SIGNAL;
+               else {
+                       fprintf(stderr, "Unknown quiet access \"%s\"\n",
+                               str_access);
+                       free(env_quiet_access);
+                       return -1;
+               }
+       }
+
+       free(env_quiet_access);
+       ruleset_attr->quiet_access_fs &= ruleset_attr->handled_access_fs;
+       ruleset_attr->quiet_access_net &= ruleset_attr->handled_access_net;
+       ruleset_attr->quiet_scoped &= ruleset_attr->scoped;
+       return 0;
+}
+
 #define LANDLOCK_ABI_LAST 10
 
 #define XSTR(s) #s
@@ -337,6 +403,19 @@ static const char help[] =
        "\n"
        "A sandboxer should not log denied access requests to avoid spamming logs, "
        "but to test audit we can set " ENV_FORCE_LOG_NAME "=1\n"
+       ENV_FS_QUIET_NAME " and " ENV_NET_QUIET_NAME ", both optional, can then be used "
+       "to make access to some denied paths or network ports not trigger audit logging.\n"
+       ENV_QUIET_ACCESS_NAME " can be used to specify which accesses should be quieted "
+       "(required when " ENV_FS_QUIET_NAME " or " ENV_NET_QUIET_NAME " is set):\n"
+       "  - \"all\" to quiet all of the accesses below\n"
+       "  - \"read\" to quiet all file/dir read accesses\n"
+       "  - \"write\" to quiet all file/dir write accesses\n"
+       "  - \"tcp_bind\" to quiet tcp bind denials\n"
+       "  - \"tcp_connect\" to quiet tcp connect denials\n"
+       "  - \"udp_bind\" to quiet udp bind denials\n"
+       "  - \"udp_connect\" to quiet udp connect / send denials\n"
+       "  - \"abstract_unix_socket\" to quiet abstract unix socket denials\n"
+       "  - \"signal\" to quiet signal denials\n"
        "\n"
        "Example:\n"
        ENV_FS_RO_NAME "=\"${PATH}:/lib:/usr:/proc:/etc:/dev/urandom\" "
@@ -369,7 +448,11 @@ int main(const int argc, char *const argv[], char *const *const envp)
                                      LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP,
                .scoped = LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET |
                          LANDLOCK_SCOPE_SIGNAL,
+               .quiet_access_fs = 0,
+               .quiet_access_net = 0,
+               .quiet_scoped = 0,
        };
+       bool quiet_supported = true;
        int supported_restrict_flags = LANDLOCK_RESTRICT_SELF_LOG_NEW_EXEC_ON;
        int set_restrict_flags = 0;
 
@@ -460,6 +543,8 @@ int main(const int argc, char *const argv[], char *const *const envp)
                ruleset_attr.handled_access_net &=
                        ~(LANDLOCK_ACCESS_NET_BIND_UDP |
                          LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP);
+               /* Removes quiet flags for ABI < 10 later on. */
+               quiet_supported = false;
 
                /* Must be printed for any ABI < LANDLOCK_ABI_LAST. */
                fprintf(stderr,
@@ -526,6 +611,25 @@ int main(const int argc, char *const argv[], char *const *const envp)
                unsetenv(ENV_FORCE_LOG_NAME);
        }
 
+       /* Set the quiet access masks. */
+       if (quiet_supported) {
+               if ((getenv(ENV_FS_QUIET_NAME) || getenv(ENV_NET_QUIET_NAME)) &&
+                   !getenv(ENV_QUIET_ACCESS_NAME)) {
+                       fprintf(stderr,
+                               "%s must be set (e.g. to \"all\") when %s or %s is used\n",
+                               ENV_QUIET_ACCESS_NAME, ENV_FS_QUIET_NAME,
+                               ENV_NET_QUIET_NAME);
+                       return 1;
+               }
+               if (add_quiet_access(ENV_QUIET_ACCESS_NAME, &ruleset_attr))
+                       return 1;
+       } else if (getenv(ENV_FS_QUIET_NAME) || getenv(ENV_NET_QUIET_NAME) ||
+                  getenv(ENV_QUIET_ACCESS_NAME)) {
+               fprintf(stderr,
+                       "Quiet flags not supported by current kernel\n");
+               return 1;
+       }
+
        ruleset_fd =
                landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
        if (ruleset_fd < 0) {
@@ -533,30 +637,42 @@ int main(const int argc, char *const argv[], char *const *const envp)
                return 1;
        }
 
-       if (populate_ruleset_fs(ENV_FS_RO_NAME, ruleset_fd, access_fs_ro)) {
+       if (populate_ruleset_fs(ENV_FS_RO_NAME, ruleset_fd, access_fs_ro, 0))
                goto err_close_ruleset;
-       }
-       if (populate_ruleset_fs(ENV_FS_RW_NAME, ruleset_fd, access_fs_rw)) {
+       if (populate_ruleset_fs(ENV_FS_RW_NAME, ruleset_fd, access_fs_rw, 0))
                goto err_close_ruleset;
+
+       /* Don't require this env to be present. */
+       if (quiet_supported && getenv(ENV_FS_QUIET_NAME)) {
+               if (populate_ruleset_fs(ENV_FS_QUIET_NAME, ruleset_fd, 0,
+                                       LANDLOCK_ADD_RULE_QUIET))
+                       goto err_close_ruleset;
        }
 
        if (populate_ruleset_net(ENV_TCP_BIND_NAME, ruleset_fd,
-                                LANDLOCK_ACCESS_NET_BIND_TCP)) {
+                                LANDLOCK_ACCESS_NET_BIND_TCP, 0)) {
                goto err_close_ruleset;
        }
        if (populate_ruleset_net(ENV_TCP_CONNECT_NAME, ruleset_fd,
-                                LANDLOCK_ACCESS_NET_CONNECT_TCP)) {
+                                LANDLOCK_ACCESS_NET_CONNECT_TCP, 0)) {
                goto err_close_ruleset;
        }
        if (populate_ruleset_net(ENV_UDP_BIND_NAME, ruleset_fd,
-                                LANDLOCK_ACCESS_NET_BIND_UDP)) {
+                                LANDLOCK_ACCESS_NET_BIND_UDP, 0)) {
                goto err_close_ruleset;
        }
        if (populate_ruleset_net(ENV_UDP_CONNECT_SEND_NAME, ruleset_fd,
-                                LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP)) {
+                                LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP, 0)) {
                goto err_close_ruleset;
        }
 
+       if (quiet_supported) {
+               if (populate_ruleset_net(ENV_NET_QUIET_NAME, ruleset_fd, 0,
+                                        LANDLOCK_ADD_RULE_QUIET)) {
+                       goto err_close_ruleset;
+               }
+       }
+
        if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {
                perror("Failed to restrict privileges");
                goto err_close_ruleset;