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-rw-r--r--samples/landlock/sandboxer.c132
1 files changed, 81 insertions, 51 deletions
diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c
index 8859fc193542..3e404e51ec64 100644
--- a/samples/landlock/sandboxer.c
+++ b/samples/landlock/sandboxer.c
@@ -22,9 +22,9 @@
#include <unistd.h>
#ifndef landlock_create_ruleset
-static inline int landlock_create_ruleset(
- const struct landlock_ruleset_attr *const attr,
- const size_t size, const __u32 flags)
+static inline int
+landlock_create_ruleset(const struct landlock_ruleset_attr *const attr,
+ const size_t size, const __u32 flags)
{
return syscall(__NR_landlock_create_ruleset, attr, size, flags);
}
@@ -32,17 +32,18 @@ static inline int landlock_create_ruleset(
#ifndef landlock_add_rule
static inline int landlock_add_rule(const int ruleset_fd,
- const enum landlock_rule_type rule_type,
- const void *const rule_attr, const __u32 flags)
+ const enum landlock_rule_type rule_type,
+ const void *const rule_attr,
+ const __u32 flags)
{
- return syscall(__NR_landlock_add_rule, ruleset_fd, rule_type,
- rule_attr, flags);
+ return syscall(__NR_landlock_add_rule, ruleset_fd, rule_type, rule_attr,
+ flags);
}
#endif
#ifndef landlock_restrict_self
static inline int landlock_restrict_self(const int ruleset_fd,
- const __u32 flags)
+ const __u32 flags)
{
return syscall(__NR_landlock_restrict_self, ruleset_fd, flags);
}
@@ -70,14 +71,17 @@ static int parse_path(char *env_path, const char ***const path_list)
return num_paths;
}
+/* clang-format off */
+
#define ACCESS_FILE ( \
LANDLOCK_ACCESS_FS_EXECUTE | \
LANDLOCK_ACCESS_FS_WRITE_FILE | \
LANDLOCK_ACCESS_FS_READ_FILE)
-static int populate_ruleset(
- const char *const env_var, const int ruleset_fd,
- const __u64 allowed_access)
+/* clang-format on */
+
+static int populate_ruleset(const char *const env_var, const int ruleset_fd,
+ const __u64 allowed_access)
{
int num_paths, i, ret = 1;
char *env_path_name;
@@ -107,12 +111,10 @@ static int populate_ruleset(
for (i = 0; i < num_paths; i++) {
struct stat statbuf;
- path_beneath.parent_fd = open(path_list[i], O_PATH |
- O_CLOEXEC);
+ path_beneath.parent_fd = open(path_list[i], O_PATH | O_CLOEXEC);
if (path_beneath.parent_fd < 0) {
fprintf(stderr, "Failed to open \"%s\": %s\n",
- path_list[i],
- strerror(errno));
+ path_list[i], strerror(errno));
goto out_free_name;
}
if (fstat(path_beneath.parent_fd, &statbuf)) {
@@ -123,9 +125,10 @@ static int populate_ruleset(
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)) {
- fprintf(stderr, "Failed to update the ruleset with \"%s\": %s\n",
- path_list[i], strerror(errno));
+ &path_beneath, 0)) {
+ fprintf(stderr,
+ "Failed to update the ruleset with \"%s\": %s\n",
+ path_list[i], strerror(errno));
close(path_beneath.parent_fd);
goto out_free_name;
}
@@ -139,6 +142,8 @@ out_free_name:
return ret;
}
+/* clang-format off */
+
#define ACCESS_FS_ROUGHLY_READ ( \
LANDLOCK_ACCESS_FS_EXECUTE | \
LANDLOCK_ACCESS_FS_READ_FILE | \
@@ -154,64 +159,89 @@ out_free_name:
LANDLOCK_ACCESS_FS_MAKE_SOCK | \
LANDLOCK_ACCESS_FS_MAKE_FIFO | \
LANDLOCK_ACCESS_FS_MAKE_BLOCK | \
- LANDLOCK_ACCESS_FS_MAKE_SYM)
+ LANDLOCK_ACCESS_FS_MAKE_SYM | \
+ LANDLOCK_ACCESS_FS_REFER)
+
+#define ACCESS_ABI_2 ( \
+ LANDLOCK_ACCESS_FS_REFER)
+
+/* clang-format on */
int main(const int argc, char *const argv[], char *const *const envp)
{
const char *cmd_path;
char *const *cmd_argv;
- int ruleset_fd;
+ int ruleset_fd, abi;
+ __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_ROUGHLY_READ |
- ACCESS_FS_ROUGHLY_WRITE,
+ .handled_access_fs = access_fs_rw,
};
if (argc < 2) {
- fprintf(stderr, "usage: %s=\"...\" %s=\"...\" %s <cmd> [args]...\n\n",
- ENV_FS_RO_NAME, ENV_FS_RW_NAME, argv[0]);
- fprintf(stderr, "Launch a command in a restricted environment.\n\n");
+ fprintf(stderr,
+ "usage: %s=\"...\" %s=\"...\" %s <cmd> [args]...\n\n",
+ ENV_FS_RO_NAME, ENV_FS_RW_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, "* %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",
- ENV_FS_RW_NAME);
- fprintf(stderr, "\nexample:\n"
- "%s=\"/bin:/lib:/usr:/proc:/etc:/dev/urandom\" "
- "%s=\"/dev/null:/dev/full:/dev/zero:/dev/pts:/tmp\" "
- "%s bash -i\n",
- ENV_FS_RO_NAME, ENV_FS_RW_NAME, argv[0]);
+ 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",
+ ENV_FS_RW_NAME);
+ fprintf(stderr,
+ "\nexample:\n"
+ "%s=\"/bin:/lib:/usr:/proc:/etc:/dev/urandom\" "
+ "%s=\"/dev/null:/dev/full:/dev/zero:/dev/pts:/tmp\" "
+ "%s bash -i\n",
+ ENV_FS_RO_NAME, ENV_FS_RW_NAME, argv[0]);
return 1;
}
- ruleset_fd = landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
- if (ruleset_fd < 0) {
+ abi = landlock_create_ruleset(NULL, 0, LANDLOCK_CREATE_RULESET_VERSION);
+ if (abi < 0) {
const int err = errno;
- perror("Failed to create a ruleset");
+ perror("Failed to check Landlock compatibility");
switch (err) {
case ENOSYS:
- fprintf(stderr, "Hint: Landlock is not supported by the current kernel. "
- "To support it, build the kernel with "
- "CONFIG_SECURITY_LANDLOCK=y and prepend "
- "\"landlock,\" to the content of CONFIG_LSM.\n");
+ fprintf(stderr,
+ "Hint: Landlock is not supported by the current kernel. "
+ "To support it, build the kernel with "
+ "CONFIG_SECURITY_LANDLOCK=y and prepend "
+ "\"landlock,\" to the content of CONFIG_LSM.\n");
break;
case EOPNOTSUPP:
- fprintf(stderr, "Hint: Landlock is currently disabled. "
- "It can be enabled in the kernel configuration by "
- "prepending \"landlock,\" to the content of CONFIG_LSM, "
- "or at boot time by setting the same content to the "
- "\"lsm\" kernel parameter.\n");
+ fprintf(stderr,
+ "Hint: Landlock is currently disabled. "
+ "It can be enabled in the kernel configuration by "
+ "prepending \"landlock,\" to the content of CONFIG_LSM, "
+ "or at boot time by setting the same content to the "
+ "\"lsm\" kernel parameter.\n");
break;
}
return 1;
}
- if (populate_ruleset(ENV_FS_RO_NAME, ruleset_fd,
- ACCESS_FS_ROUGHLY_READ)) {
+ /* Best-effort security. */
+ if (abi < 2) {
+ ruleset_attr.handled_access_fs &= ~ACCESS_ABI_2;
+ access_fs_ro &= ~ACCESS_ABI_2;
+ access_fs_rw &= ~ACCESS_ABI_2;
+ }
+
+ 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)) {
goto err_close_ruleset;
}
- if (populate_ruleset(ENV_FS_RW_NAME, ruleset_fd,
- ACCESS_FS_ROUGHLY_READ | ACCESS_FS_ROUGHLY_WRITE)) {
+ if (populate_ruleset(ENV_FS_RW_NAME, ruleset_fd, access_fs_rw)) {
goto err_close_ruleset;
}
if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {
@@ -228,7 +258,7 @@ int main(const int argc, char *const argv[], char *const *const envp)
cmd_argv = argv + 1;
execvpe(cmd_path, cmd_argv, envp);
fprintf(stderr, "Failed to execute \"%s\": %s\n", cmd_path,
- strerror(errno));
+ strerror(errno));
fprintf(stderr, "Hint: access to the binary, the interpreter or "
"shared libraries may be denied.\n");
return 1;
Copyright © 1996 – 2023 Jason A. Donenfeld. All Rights Reverse Engineered.