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authorMickaël Salaün <mic@digikod.net>2022-05-06 18:10:59 +0200
committerMickaël Salaün <mic@digikod.net>2022-05-23 13:28:00 +0200
commit76b902f874ff4de9c1078489d4c7678a64105ea6 (patch)
tree2b890621d9978d414c76f83952e29608833b88c1
parentf4056b9266b571c63f30cda70c2d89f7b7e8bb7b (diff)
downloadlinux-76b902f874ff4de9c1078489d4c7678a64105ea6.tar.bz2
samples/landlock: Add support for file reparenting
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 <paul@paul-moore.com> Signed-off-by: Mickaël Salaün <mic@digikod.net> Link: https://lore.kernel.org/r/20220506161102.525323-10-mic@digikod.net
-rw-r--r--samples/landlock/sandboxer.c40
1 files 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 @@ 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 */
@@ -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)) {