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authorJann Horn <jannh@google.com>2019-04-10 19:55:34 +0300
committerMicah Morton <mortonm@chromium.org>2019-07-15 18:05:48 +0300
commit1cd02a27a9473fed0294561137cfb7dcc9b3aaa0 (patch)
tree50f7aad2ffd88d37bcf508ccc772d70444fe2fff
parent7ef6b3062fb9f0b9dbaaec182495189459100807 (diff)
downloadlinux-1cd02a27a9473fed0294561137cfb7dcc9b3aaa0.tar.xz
LSM: SafeSetID: refactor policy hash table
parent_kuid and child_kuid are kuids, there is no reason to make them uint64_t. (And anyway, in the kernel, the normal name for that would be u64, not uint64_t.) check_setuid_policy_hashtable_key() and check_setuid_policy_hashtable_key_value() are basically the same thing, merge them. Also fix the comment that claimed that (1<<8)==128. Signed-off-by: Jann Horn <jannh@google.com> Signed-off-by: Micah Morton <mortonm@chromium.org>
-rw-r--r--security/safesetid/lsm.c62
-rw-r--r--security/safesetid/lsm.h19
2 files changed, 37 insertions, 44 deletions
diff --git a/security/safesetid/lsm.c b/security/safesetid/lsm.c
index 0770447d51f0..56e1b285a4ae 100644
--- a/security/safesetid/lsm.c
+++ b/security/safesetid/lsm.c
@@ -14,67 +14,40 @@
#define pr_fmt(fmt) "SafeSetID: " fmt
-#include <linux/hashtable.h>
#include <linux/lsm_hooks.h>
#include <linux/module.h>
#include <linux/ptrace.h>
#include <linux/sched/task_stack.h>
#include <linux/security.h>
+#include "lsm.h"
/* Flag indicating whether initialization completed */
int safesetid_initialized;
-#define NUM_BITS 8 /* 128 buckets in hash table */
+#define NUM_BITS 8 /* 256 buckets in hash table */
static DEFINE_HASHTABLE(safesetid_whitelist_hashtable, NUM_BITS);
-/*
- * Hash table entry to store safesetid policy signifying that 'parent' user
- * can setid to 'child' user.
- */
-struct entry {
- struct hlist_node next;
- struct hlist_node dlist; /* for deletion cleanup */
- uint64_t parent_kuid;
- uint64_t child_kuid;
-};
-
static DEFINE_SPINLOCK(safesetid_whitelist_hashtable_spinlock);
-static bool check_setuid_policy_hashtable_key(kuid_t parent)
+static enum sid_policy_type setuid_policy_lookup(kuid_t src, kuid_t dst)
{
struct entry *entry;
+ enum sid_policy_type result = SIDPOL_DEFAULT;
rcu_read_lock();
hash_for_each_possible_rcu(safesetid_whitelist_hashtable,
- entry, next, __kuid_val(parent)) {
- if (entry->parent_kuid == __kuid_val(parent)) {
+ entry, next, __kuid_val(src)) {
+ if (!uid_eq(entry->src_uid, src))
+ continue;
+ if (uid_eq(entry->dst_uid, dst)) {
rcu_read_unlock();
- return true;
+ return SIDPOL_ALLOWED;
}
+ result = SIDPOL_CONSTRAINED;
}
rcu_read_unlock();
-
- return false;
-}
-
-static bool check_setuid_policy_hashtable_key_value(kuid_t parent,
- kuid_t child)
-{
- struct entry *entry;
-
- rcu_read_lock();
- hash_for_each_possible_rcu(safesetid_whitelist_hashtable,
- entry, next, __kuid_val(parent)) {
- if (entry->parent_kuid == __kuid_val(parent) &&
- entry->child_kuid == __kuid_val(child)) {
- rcu_read_unlock();
- return true;
- }
- }
- rcu_read_unlock();
-
- return false;
+ return result;
}
static int safesetid_security_capable(const struct cred *cred,
@@ -83,7 +56,7 @@ static int safesetid_security_capable(const struct cred *cred,
unsigned int opts)
{
if (cap == CAP_SETUID &&
- check_setuid_policy_hashtable_key(cred->uid)) {
+ setuid_policy_lookup(cred->uid, INVALID_UID) != SIDPOL_DEFAULT) {
if (!(opts & CAP_OPT_INSETID)) {
/*
* Deny if we're not in a set*uid() syscall to avoid
@@ -116,7 +89,8 @@ static bool uid_permitted_for_cred(const struct cred *old, kuid_t new_uid)
* Transitions to new UIDs require a check against the policy of the old
* RUID.
*/
- permitted = check_setuid_policy_hashtable_key_value(old->uid, new_uid);
+ permitted =
+ setuid_policy_lookup(old->uid, new_uid) != SIDPOL_CONSTRAINED;
if (!permitted) {
pr_warn("UID transition ((%d,%d,%d) -> %d) blocked\n",
__kuid_val(old->uid), __kuid_val(old->euid),
@@ -136,7 +110,7 @@ static int safesetid_task_fix_setuid(struct cred *new,
{
/* Do nothing if there are no setuid restrictions for our old RUID. */
- if (!check_setuid_policy_hashtable_key(old->uid))
+ if (setuid_policy_lookup(old->uid, INVALID_UID) == SIDPOL_DEFAULT)
return 0;
if (uid_permitted_for_cred(old, new->uid) &&
@@ -159,14 +133,14 @@ int add_safesetid_whitelist_entry(kuid_t parent, kuid_t child)
struct entry *new;
/* Return if entry already exists */
- if (check_setuid_policy_hashtable_key_value(parent, child))
+ if (setuid_policy_lookup(parent, child) == SIDPOL_ALLOWED)
return 0;
new = kzalloc(sizeof(struct entry), GFP_KERNEL);
if (!new)
return -ENOMEM;
- new->parent_kuid = __kuid_val(parent);
- new->child_kuid = __kuid_val(child);
+ new->src_uid = parent;
+ new->dst_uid = child;
spin_lock(&safesetid_whitelist_hashtable_spinlock);
hash_add_rcu(safesetid_whitelist_hashtable,
&new->next,
diff --git a/security/safesetid/lsm.h b/security/safesetid/lsm.h
index c1ea3c265fcf..6806f902794c 100644
--- a/security/safesetid/lsm.h
+++ b/security/safesetid/lsm.h
@@ -15,6 +15,8 @@
#define _SAFESETID_H
#include <linux/types.h>
+#include <linux/uidgid.h>
+#include <linux/hashtable.h>
/* Flag indicating whether initialization completed */
extern int safesetid_initialized;
@@ -25,6 +27,23 @@ enum safesetid_whitelist_file_write_type {
SAFESETID_WHITELIST_FLUSH, /* Flush whitelist policies. */
};
+enum sid_policy_type {
+ SIDPOL_DEFAULT, /* source ID is unaffected by policy */
+ SIDPOL_CONSTRAINED, /* source ID is affected by policy */
+ SIDPOL_ALLOWED /* target ID explicitly allowed */
+};
+
+/*
+ * Hash table entry to store safesetid policy signifying that 'src_uid'
+ * can setid to 'dst_uid'.
+ */
+struct entry {
+ struct hlist_node next;
+ struct hlist_node dlist; /* for deletion cleanup */
+ kuid_t src_uid;
+ kuid_t dst_uid;
+};
+
/* Add entry to safesetid whitelist to allow 'parent' to setid to 'child'. */
int add_safesetid_whitelist_entry(kuid_t parent, kuid_t child);