[RFC PATCH v1 5/7] landlock: Log file-related requests
Mickaël Salaün
mic at digikod.net
Thu Sep 21 06:16:39 UTC 2023
Add audit support for mkdir, mknod, symlink, unlink, rmdir, truncate,
and open requests.
Signed-off-by: Mickaël Salaün <mic at digikod.net>
---
security/landlock/audit.c | 114 ++++++++++++++++++++++++++++++++++++++
security/landlock/audit.h | 32 +++++++++++
security/landlock/fs.c | 62 ++++++++++++++++++---
3 files changed, 199 insertions(+), 9 deletions(-)
diff --git a/security/landlock/audit.c b/security/landlock/audit.c
index d9589d07e126..148fc0fafef4 100644
--- a/security/landlock/audit.c
+++ b/security/landlock/audit.c
@@ -14,6 +14,25 @@
atomic64_t ruleset_and_domain_counter = ATOMIC64_INIT(0);
+static const char *op_to_string(enum landlock_operation operation)
+{
+ const char *const desc[] = {
+ [0] = "",
+ [LANDLOCK_OP_MKDIR] = "mkdir",
+ [LANDLOCK_OP_MKNOD] = "mknod",
+ [LANDLOCK_OP_SYMLINK] = "symlink",
+ [LANDLOCK_OP_UNLINK] = "unlink",
+ [LANDLOCK_OP_RMDIR] = "rmdir",
+ [LANDLOCK_OP_TRUNCATE] = "truncate",
+ [LANDLOCK_OP_OPEN] = "open",
+ };
+
+ if (WARN_ON_ONCE(operation < 0 || operation > ARRAY_SIZE(desc)))
+ return "unknown";
+
+ return desc[operation];
+}
+
#define BIT_INDEX(bit) HWEIGHT(bit - 1)
static void log_accesses(struct audit_buffer *const ab,
@@ -141,3 +160,98 @@ void landlock_log_release_ruleset(const struct landlock_ruleset *const ruleset)
audit_log_format(ab, "op=release-%s %s=%llu", name, name, id);
audit_log_end(ab);
}
+
+/* Update request.youngest_domain and request.missing_access */
+static void
+update_request(struct landlock_request *const request,
+ const struct landlock_ruleset *const domain,
+ const access_mask_t access_request,
+ const layer_mask_t (*const layer_masks)[LANDLOCK_NUM_ACCESS_FS])
+{
+ const unsigned long access_req = access_request;
+ unsigned long access_bit;
+ long youngest_denied_layer = -1;
+ const struct landlock_hierarchy *node = domain->hierarchy;
+ size_t i;
+
+ WARN_ON_ONCE(request->youngest_domain);
+ WARN_ON_ONCE(request->missing_access);
+
+ if (WARN_ON_ONCE(!access_request))
+ return;
+
+ if (WARN_ON_ONCE(!layer_masks))
+ return;
+
+ for_each_set_bit(access_bit, &access_req, ARRAY_SIZE(*layer_masks)) {
+ long domain_layer;
+
+ if (!(*layer_masks)[access_bit])
+ continue;
+
+ domain_layer = __fls((*layer_masks)[access_bit]);
+
+ /*
+ * Gets the access rights that are missing from
+ * the youngest (i.e. closest) domain.
+ */
+ if (domain_layer == youngest_denied_layer) {
+ request->missing_access |= BIT_ULL(access_bit);
+ } else if (domain_layer > youngest_denied_layer) {
+ youngest_denied_layer = domain_layer;
+ request->missing_access = BIT_ULL(access_bit);
+ }
+ }
+
+ WARN_ON_ONCE(!request->missing_access);
+ WARN_ON_ONCE(youngest_denied_layer < 0);
+
+ /* Gets the nearest domain ID that denies request.missing_access */
+ for (i = domain->num_layers - youngest_denied_layer - 1; i > 0; i--)
+ node = node->parent;
+ request->youngest_domain = node->id;
+}
+
+static void
+log_request(const int error, struct landlock_request *const request,
+ const struct landlock_ruleset *const domain,
+ const access_mask_t access_request,
+ const layer_mask_t (*const layer_masks)[LANDLOCK_NUM_ACCESS_FS])
+{
+ struct audit_buffer *ab;
+
+ if (WARN_ON_ONCE(!error))
+ return;
+ if (WARN_ON_ONCE(!request))
+ return;
+ if (WARN_ON_ONCE(!domain || !domain->hierarchy))
+ return;
+
+ /* Uses GFP_ATOMIC to not sleep. */
+ ab = audit_log_start(audit_context(), GFP_ATOMIC | __GFP_NOWARN,
+ AUDIT_LANDLOCK);
+ if (!ab)
+ return;
+
+ update_request(request, domain, access_request, layer_masks);
+
+ log_task(ab);
+ audit_log_format(ab, " domain=%llu op=%s errno=%d missing-fs-accesses=",
+ request->youngest_domain,
+ op_to_string(request->operation), -error);
+ log_accesses(ab, request->missing_access);
+ audit_log_lsm_data(ab, &request->audit);
+ audit_log_end(ab);
+}
+
+// TODO: Make it generic, not FS-centric.
+int landlock_log_request(
+ const int error, struct landlock_request *const request,
+ const struct landlock_ruleset *const domain,
+ const access_mask_t access_request,
+ const layer_mask_t (*const layer_masks)[LANDLOCK_NUM_ACCESS_FS])
+{
+ /* No need to log the access request, only the missing accesses. */
+ log_request(error, request, domain, access_request, layer_masks);
+ return error;
+}
diff --git a/security/landlock/audit.h b/security/landlock/audit.h
index bc17dc8ca6f1..8edc68b98fca 100644
--- a/security/landlock/audit.h
+++ b/security/landlock/audit.h
@@ -13,6 +13,23 @@
#include "ruleset.h"
+enum landlock_operation {
+ LANDLOCK_OP_MKDIR = 1,
+ LANDLOCK_OP_MKNOD,
+ LANDLOCK_OP_SYMLINK,
+ LANDLOCK_OP_UNLINK,
+ LANDLOCK_OP_RMDIR,
+ LANDLOCK_OP_TRUNCATE,
+ LANDLOCK_OP_OPEN,
+};
+
+struct landlock_request {
+ const enum landlock_operation operation;
+ access_mask_t missing_access;
+ u64 youngest_domain;
+ struct common_audit_data audit;
+};
+
#ifdef CONFIG_AUDIT
void landlock_log_create_ruleset(struct landlock_ruleset *const ruleset);
@@ -20,6 +37,12 @@ void landlock_log_restrict_self(struct landlock_ruleset *const domain,
struct landlock_ruleset *const ruleset);
void landlock_log_release_ruleset(const struct landlock_ruleset *const ruleset);
+int landlock_log_request(
+ const int error, struct landlock_request *const request,
+ const struct landlock_ruleset *const domain,
+ const access_mask_t access_request,
+ const layer_mask_t (*const layer_masks)[LANDLOCK_NUM_ACCESS_FS]);
+
#else /* CONFIG_AUDIT */
static inline void
@@ -38,6 +61,15 @@ landlock_log_release_ruleset(const struct landlock_ruleset *const ruleset)
{
}
+static inline int landlock_log_request(
+ const int error, struct landlock_request *const request,
+ const struct landlock_ruleset *const domain,
+ const access_mask_t access_request,
+ const layer_mask_t (*const layer_masks)[LANDLOCK_NUM_ACCESS_FS])
+{
+ return error;
+}
+
#endif /* CONFIG_AUDIT */
#endif /* _SECURITY_LANDLOCK_AUDIT_H */
diff --git a/security/landlock/fs.c b/security/landlock/fs.c
index 978e325d8708..104dfb2abc32 100644
--- a/security/landlock/fs.c
+++ b/security/landlock/fs.c
@@ -18,6 +18,7 @@
#include <linux/kernel.h>
#include <linux/limits.h>
#include <linux/list.h>
+#include <linux/lsm_audit.h>
#include <linux/lsm_hooks.h>
#include <linux/mount.h>
#include <linux/namei.h>
@@ -30,6 +31,7 @@
#include <linux/workqueue.h>
#include <uapi/linux/landlock.h>
+#include "audit.h"
#include "common.h"
#include "cred.h"
#include "fs.h"
@@ -636,7 +638,8 @@ static bool is_access_to_paths_allowed(
}
static int current_check_access_path(const struct path *const path,
- access_mask_t access_request)
+ access_mask_t access_request,
+ struct landlock_request *const request)
{
const struct landlock_ruleset *const dom =
landlock_get_current_domain();
@@ -650,7 +653,10 @@ static int current_check_access_path(const struct path *const path,
NULL, 0, NULL, NULL))
return 0;
- return -EACCES;
+ request->audit.type = LSM_AUDIT_DATA_PATH;
+ request->audit.u.path = *path;
+ return landlock_log_request(-EACCES, request, dom, access_request,
+ &layer_masks);
}
static inline access_mask_t get_mode_access(const umode_t mode)
@@ -1097,6 +1103,7 @@ static int hook_path_link(struct dentry *const old_dentry,
const struct path *const new_dir,
struct dentry *const new_dentry)
{
+ // TODO: Implement fine-grained audit
return current_check_refer_path(old_dentry, new_dir, new_dentry, false,
false);
}
@@ -1115,38 +1122,67 @@ static int hook_path_rename(const struct path *const old_dir,
static int hook_path_mkdir(const struct path *const dir,
struct dentry *const dentry, const umode_t mode)
{
- return current_check_access_path(dir, LANDLOCK_ACCESS_FS_MAKE_DIR);
+ struct landlock_request request = {
+ .operation = LANDLOCK_OP_MKDIR,
+ };
+
+ return current_check_access_path(dir, LANDLOCK_ACCESS_FS_MAKE_DIR,
+ &request);
}
static int hook_path_mknod(const struct path *const dir,
struct dentry *const dentry, const umode_t mode,
const unsigned int dev)
{
- return current_check_access_path(dir, get_mode_access(mode));
+ struct landlock_request request = {
+ .operation = LANDLOCK_OP_MKNOD,
+ };
+
+ return current_check_access_path(dir, get_mode_access(mode), &request);
}
static int hook_path_symlink(const struct path *const dir,
struct dentry *const dentry,
const char *const old_name)
{
- return current_check_access_path(dir, LANDLOCK_ACCESS_FS_MAKE_SYM);
+ struct landlock_request request = {
+ .operation = LANDLOCK_OP_SYMLINK,
+ };
+
+ return current_check_access_path(dir, LANDLOCK_ACCESS_FS_MAKE_SYM,
+ &request);
}
static int hook_path_unlink(const struct path *const dir,
struct dentry *const dentry)
{
- return current_check_access_path(dir, LANDLOCK_ACCESS_FS_REMOVE_FILE);
+ struct landlock_request request = {
+ .operation = LANDLOCK_OP_UNLINK,
+ };
+
+ return current_check_access_path(dir, LANDLOCK_ACCESS_FS_REMOVE_FILE,
+ &request);
}
static int hook_path_rmdir(const struct path *const dir,
struct dentry *const dentry)
{
- return current_check_access_path(dir, LANDLOCK_ACCESS_FS_REMOVE_DIR);
+ struct landlock_request request = {
+ .operation = LANDLOCK_OP_RMDIR,
+ };
+
+ return current_check_access_path(dir, LANDLOCK_ACCESS_FS_REMOVE_DIR,
+ &request);
}
static int hook_path_truncate(const struct path *const path)
{
- return current_check_access_path(path, LANDLOCK_ACCESS_FS_TRUNCATE);
+ struct landlock_request request = {
+ .operation = LANDLOCK_OP_TRUNCATE,
+ };
+
+ return current_check_access_path(path, LANDLOCK_ACCESS_FS_TRUNCATE,
+ &request);
}
/* File hooks */
@@ -1199,6 +1235,13 @@ static int hook_file_open(struct file *const file)
const access_mask_t optional_access = LANDLOCK_ACCESS_FS_TRUNCATE;
const struct landlock_ruleset *const dom =
landlock_get_current_domain();
+ struct landlock_request request = {
+ .operation = LANDLOCK_OP_OPEN,
+ .audit = {
+ .type = LSM_AUDIT_DATA_PATH,
+ .u.path = file->f_path,
+ },
+ };
if (!dom)
return 0;
@@ -1249,7 +1292,8 @@ static int hook_file_open(struct file *const file)
if ((open_access_request & allowed_access) == open_access_request)
return 0;
- return -EACCES;
+ return landlock_log_request(-EACCES, &request, dom, open_access_request,
+ &layer_masks);
}
static int hook_file_truncate(struct file *const file)
--
2.42.0
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