Add LANDLOCK_ACCESS_FS_REFER to the "roughly write" access rights and
leverage the Landlock ABI version to only try to enforce it if it is
supported by the running kernel.
Reviewed-by: Paul Moore <[email protected]>
Signed-off-by: Mickaël Salaün <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
---
Changes since v2:
* Format with clang-format and rebase.
Changes since v1:
* Add Reviewed-by: Paul Moore.
---
samples/landlock/sandboxer.c | 40 ++++++++++++++++++++++++------------
1 file changed, 27 insertions(+), 13 deletions(-)
diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c
index c089e9cdaf32..3e404e51ec64 100644
--- a/samples/landlock/sandboxer.c
+++ b/samples/landlock/sandboxer.c
@@ -159,7 +159,11 @@ static int populate_ruleset(const char *const env_var, const int ruleset_fd,
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 */
@@ -167,10 +171,11 @@ 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) {
@@ -196,12 +201,11 @@ int main(const int argc, char *const argv[], char *const *const envp)
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,
@@ -221,13 +225,23 @@ int main(const int argc, char *const argv[], char *const *const envp)
}
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)) {
--
2.35.1