On 08/09/2022 21:58, Günther Noack wrote:
Update the sandboxer sample to restrict truncate actions. This is
automatically enabled by default if the running kernel supports
LANDLOCK_ACCESS_FS_TRUNCATE, expect for the paths listed in the
except for
LL_FS_RW environment variable.
Signed-off-by: Günther Noack <gnoack3000@xxxxxxxxx>
---
samples/landlock/sandboxer.c | 23 ++++++++++++++---------
1 file changed, 14 insertions(+), 9 deletions(-)
diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c
index 3e404e51ec64..771b6b10d519 100644
--- a/samples/landlock/sandboxer.c
+++ b/samples/landlock/sandboxer.c
@@ -76,7 +76,8 @@ static int parse_path(char *env_path, const char ***const path_list)
#define ACCESS_FILE ( \
LANDLOCK_ACCESS_FS_EXECUTE | \
LANDLOCK_ACCESS_FS_WRITE_FILE | \
- LANDLOCK_ACCESS_FS_READ_FILE)
+ LANDLOCK_ACCESS_FS_READ_FILE | \
+ LANDLOCK_ACCESS_FS_TRUNCATE)
/* clang-format on */
@@ -160,10 +161,8 @@ static int populate_ruleset(const char *const env_var, const int ruleset_fd,
LANDLOCK_ACCESS_FS_MAKE_FIFO | \
LANDLOCK_ACCESS_FS_MAKE_BLOCK | \
LANDLOCK_ACCESS_FS_MAKE_SYM | \
- LANDLOCK_ACCESS_FS_REFER)
-
-#define ACCESS_ABI_2 ( \
- LANDLOCK_ACCESS_FS_REFER)
+ LANDLOCK_ACCESS_FS_REFER | \
+ LANDLOCK_ACCESS_FS_TRUNCATE)
/* clang-format on */
@@ -226,11 +225,17 @@ int main(const int argc, char *const argv[], char *const *const envp)
return 1;
}
/* 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;
+ switch (abi) {
+ case 1:
+ /* Removes LANDLOCK_ACCESS_FS_REFER for ABI < 2 */
+ ruleset_attr.handled_access_fs &= ~LANDLOCK_ACCESS_FS_REFER;
+ __attribute__((fallthrough));
+ case 2:
+ /* Removes LANDLOCK_ACCESS_FS_TRUNCATE for ABI < 3 */
+ ruleset_attr.handled_access_fs &= ~LANDLOCK_ACCESS_FS_TRUNCATE;
}
+ access_fs_ro &= ruleset_attr.handled_access_fs;
+ access_fs_rw &= ruleset_attr.handled_access_fs;
ruleset_fd =
landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
