Do not pollute audit logs because of unknown sandboxed programs. Indeed, the sandboxer's security policy might not be fitted to the set of sandboxed processes that could be spawned (e.g. from a shell).
The LANDLOCK_RESTRICT_SELF_LOGLESS flag should be used for all similar sandboxer tools by default. Only natively-sandboxed programs should not use this flag. For test purpose, parse the LL_FORCE_LOG environment variable to still log denials. Cc: Günther Noack <[email protected]> Signed-off-by: Mickaël Salaün <[email protected]> Link: https://lore.kernel.org/r/[email protected] --- Changes since v2: - New patch. --- samples/landlock/sandboxer.c | 35 ++++++++++++++++++++++++++++++++--- 1 file changed, 32 insertions(+), 3 deletions(-) diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c index 57565dfd74a2..49fd4fdb1dcf 100644 --- a/samples/landlock/sandboxer.c +++ b/samples/landlock/sandboxer.c @@ -58,6 +58,7 @@ static inline int landlock_restrict_self(const int ruleset_fd, #define ENV_TCP_BIND_NAME "LL_TCP_BIND" #define ENV_TCP_CONNECT_NAME "LL_TCP_CONNECT" #define ENV_SCOPED_NAME "LL_SCOPED" +#define ENV_FORCE_LOG_NAME "LL_FORCE_LOG" #define ENV_DELIMITER ":" static int str2num(const char *numstr, __u64 *num_dst) @@ -288,7 +289,7 @@ static bool check_ruleset_scope(const char *const env_var, /* clang-format on */ -#define LANDLOCK_ABI_LAST 6 +#define LANDLOCK_ABI_LAST 7 #define XSTR(s) #s #define STR(s) XSTR(s) @@ -315,6 +316,9 @@ static const char help[] = " - \"a\" to restrict opening abstract unix sockets\n" " - \"s\" to restrict sending signals\n" "\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" + "\n" "Example:\n" ENV_FS_RO_NAME "=\"${PATH}:/lib:/usr:/proc:/etc:/dev/urandom\" " ENV_FS_RW_NAME "=\"/dev/null:/dev/full:/dev/zero:/dev/pts:/tmp\" " @@ -333,7 +337,7 @@ 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; + char *env_port_name, *env_force_log; __u64 access_fs_ro = ACCESS_FS_ROUGHLY_READ, access_fs_rw = ACCESS_FS_ROUGHLY_READ | ACCESS_FS_ROUGHLY_WRITE; @@ -344,6 +348,8 @@ int main(const int argc, char *const argv[], char *const *const envp) .scoped = LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET | LANDLOCK_SCOPE_SIGNAL, }; + /* Do not pollute audit logs because of unknown sandboxed programs. */ + int restrict_flags = LANDLOCK_RESTRICT_SELF_LOGLESS; if (argc < 2) { fprintf(stderr, help, argv[0]); @@ -415,6 +421,12 @@ int main(const int argc, char *const argv[], char *const *const envp) /* Removes LANDLOCK_SCOPE_* for ABI < 6 */ ruleset_attr.scoped &= ~(LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET | LANDLOCK_SCOPE_SIGNAL); + __attribute__((fallthrough)); + case 6: + /* Removes LANDLOCK_RESTRICT_SELF_LOGLESS for ABI < 7 */ + restrict_flags &= ~LANDLOCK_RESTRICT_SELF_LOGLESS; + + /* Must be printed for any ABI < LANDLOCK_ABI_LAST. */ fprintf(stderr, "Hint: You should update the running kernel " "to leverage Landlock features " @@ -449,6 +461,23 @@ int main(const int argc, char *const argv[], char *const *const envp) if (check_ruleset_scope(ENV_SCOPED_NAME, &ruleset_attr)) return 1; + /* Enables optional logs. */ + env_force_log = getenv(ENV_FORCE_LOG_NAME); + if (env_force_log) { + if (strcmp(env_force_log, "1") != 0) { + fprintf(stderr, + "Unknown value for " ENV_FORCE_LOG_NAME "\n"); + return 1; + } + if (!(restrict_flags & LANDLOCK_RESTRICT_SELF_LOGLESS)) { + fprintf(stderr, + "Audit logs not supported by current kernel\n"); + return 1; + } + restrict_flags &= ~LANDLOCK_RESTRICT_SELF_LOGLESS; + unsetenv(ENV_FORCE_LOG_NAME); + } + ruleset_fd = landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0); if (ruleset_fd < 0) { @@ -476,7 +505,7 @@ int main(const int argc, char *const argv[], char *const *const envp) perror("Failed to restrict privileges"); goto err_close_ruleset; } - if (landlock_restrict_self(ruleset_fd, 0)) { + if (landlock_restrict_self(ruleset_fd, restrict_flags)) { perror("Failed to enforce ruleset"); goto err_close_ruleset; } -- 2.47.0
