2019-01-16 23:46:06 +08:00
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/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* SafeSetID Linux Security Module
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*
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* Author: Micah Morton <mortonm@chromium.org>
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*
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* Copyright (C) 2018 The Chromium OS Authors.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2, as
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* published by the Free Software Foundation.
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*
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*/
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#ifndef _SAFESETID_H
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#define _SAFESETID_H
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#include <linux/types.h>
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2019-04-11 00:55:34 +08:00
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#include <linux/uidgid.h>
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#include <linux/hashtable.h>
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2019-01-16 23:46:06 +08:00
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/* Flag indicating whether initialization completed */
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extern int safesetid_initialized;
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2019-04-11 00:55:34 +08:00
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enum sid_policy_type {
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SIDPOL_DEFAULT, /* source ID is unaffected by policy */
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SIDPOL_CONSTRAINED, /* source ID is affected by policy */
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SIDPOL_ALLOWED /* target ID explicitly allowed */
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};
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/*
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* Hash table entry to store safesetid policy signifying that 'src_uid'
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LSM: SafeSetID: rewrite userspace API to atomic updates
The current API of the SafeSetID LSM uses one write() per rule, and applies
each written rule instantly. This has several downsides:
- While a policy is being loaded, once a single parent-child pair has been
loaded, the parent is restricted to that specific child, even if
subsequent rules would allow transitions to other child UIDs. This means
that during policy loading, set*uid() can randomly fail.
- To replace the policy without rebooting, it is necessary to first flush
all old rules. This creates a time window in which no constraints are
placed on the use of CAP_SETUID.
- If we want to perform sanity checks on the final policy, this requires
that the policy isn't constructed in a piecemeal fashion without telling
the kernel when it's done.
Other kernel APIs - including things like the userns code and netfilter -
avoid this problem by performing updates atomically. Luckily, SafeSetID
hasn't landed in a stable (upstream) release yet, so maybe it's not too
late to completely change the API.
The new API for SafeSetID is: If you want to change the policy, open
"safesetid/whitelist_policy" and write the entire policy,
newline-delimited, in there.
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Micah Morton <mortonm@chromium.org>
2019-04-11 00:56:05 +08:00
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* can setuid to 'dst_uid'.
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2019-04-11 00:55:34 +08:00
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*/
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LSM: SafeSetID: rewrite userspace API to atomic updates
The current API of the SafeSetID LSM uses one write() per rule, and applies
each written rule instantly. This has several downsides:
- While a policy is being loaded, once a single parent-child pair has been
loaded, the parent is restricted to that specific child, even if
subsequent rules would allow transitions to other child UIDs. This means
that during policy loading, set*uid() can randomly fail.
- To replace the policy without rebooting, it is necessary to first flush
all old rules. This creates a time window in which no constraints are
placed on the use of CAP_SETUID.
- If we want to perform sanity checks on the final policy, this requires
that the policy isn't constructed in a piecemeal fashion without telling
the kernel when it's done.
Other kernel APIs - including things like the userns code and netfilter -
avoid this problem by performing updates atomically. Luckily, SafeSetID
hasn't landed in a stable (upstream) release yet, so maybe it's not too
late to completely change the API.
The new API for SafeSetID is: If you want to change the policy, open
"safesetid/whitelist_policy" and write the entire policy,
newline-delimited, in there.
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Micah Morton <mortonm@chromium.org>
2019-04-11 00:56:05 +08:00
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struct setuid_rule {
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2019-04-11 00:55:34 +08:00
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struct hlist_node next;
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kuid_t src_uid;
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kuid_t dst_uid;
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};
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LSM: SafeSetID: rewrite userspace API to atomic updates
The current API of the SafeSetID LSM uses one write() per rule, and applies
each written rule instantly. This has several downsides:
- While a policy is being loaded, once a single parent-child pair has been
loaded, the parent is restricted to that specific child, even if
subsequent rules would allow transitions to other child UIDs. This means
that during policy loading, set*uid() can randomly fail.
- To replace the policy without rebooting, it is necessary to first flush
all old rules. This creates a time window in which no constraints are
placed on the use of CAP_SETUID.
- If we want to perform sanity checks on the final policy, this requires
that the policy isn't constructed in a piecemeal fashion without telling
the kernel when it's done.
Other kernel APIs - including things like the userns code and netfilter -
avoid this problem by performing updates atomically. Luckily, SafeSetID
hasn't landed in a stable (upstream) release yet, so maybe it's not too
late to completely change the API.
The new API for SafeSetID is: If you want to change the policy, open
"safesetid/whitelist_policy" and write the entire policy,
newline-delimited, in there.
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Micah Morton <mortonm@chromium.org>
2019-04-11 00:56:05 +08:00
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#define SETID_HASH_BITS 8 /* 256 buckets in hash table */
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struct setuid_ruleset {
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DECLARE_HASHTABLE(rules, SETID_HASH_BITS);
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struct rcu_head rcu;
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};
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enum sid_policy_type _setuid_policy_lookup(struct setuid_ruleset *policy,
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kuid_t src, kuid_t dst);
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2019-01-16 23:46:06 +08:00
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LSM: SafeSetID: rewrite userspace API to atomic updates
The current API of the SafeSetID LSM uses one write() per rule, and applies
each written rule instantly. This has several downsides:
- While a policy is being loaded, once a single parent-child pair has been
loaded, the parent is restricted to that specific child, even if
subsequent rules would allow transitions to other child UIDs. This means
that during policy loading, set*uid() can randomly fail.
- To replace the policy without rebooting, it is necessary to first flush
all old rules. This creates a time window in which no constraints are
placed on the use of CAP_SETUID.
- If we want to perform sanity checks on the final policy, this requires
that the policy isn't constructed in a piecemeal fashion without telling
the kernel when it's done.
Other kernel APIs - including things like the userns code and netfilter -
avoid this problem by performing updates atomically. Luckily, SafeSetID
hasn't landed in a stable (upstream) release yet, so maybe it's not too
late to completely change the API.
The new API for SafeSetID is: If you want to change the policy, open
"safesetid/whitelist_policy" and write the entire policy,
newline-delimited, in there.
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Micah Morton <mortonm@chromium.org>
2019-04-11 00:56:05 +08:00
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extern struct setuid_ruleset __rcu *safesetid_setuid_rules;
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2019-01-16 23:46:06 +08:00
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#endif /* _SAFESETID_H */
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