mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-12-18 00:26:47 +07:00
e10337daef
The capable() hook returns an error number. -EPERM is actually the same as -1, so this doesn't make a difference in behavior. Signed-off-by: Jann Horn <jannh@google.com> Signed-off-by: Micah Morton <mortonm@chromium.org>
172 lines
4.7 KiB
C
172 lines
4.7 KiB
C
// SPDX-License-Identifier: GPL-2.0
|
|
/*
|
|
* SafeSetID Linux Security Module
|
|
*
|
|
* Author: Micah Morton <mortonm@chromium.org>
|
|
*
|
|
* Copyright (C) 2018 The Chromium OS Authors.
|
|
*
|
|
* This program is free software; you can redistribute it and/or modify
|
|
* it under the terms of the GNU General Public License version 2, as
|
|
* published by the Free Software Foundation.
|
|
*
|
|
*/
|
|
|
|
#define pr_fmt(fmt) "SafeSetID: " fmt
|
|
|
|
#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;
|
|
|
|
struct setuid_ruleset __rcu *safesetid_setuid_rules;
|
|
|
|
/* Compute a decision for a transition from @src to @dst under @policy. */
|
|
enum sid_policy_type _setuid_policy_lookup(struct setuid_ruleset *policy,
|
|
kuid_t src, kuid_t dst)
|
|
{
|
|
struct setuid_rule *rule;
|
|
enum sid_policy_type result = SIDPOL_DEFAULT;
|
|
|
|
hash_for_each_possible(policy->rules, rule, next, __kuid_val(src)) {
|
|
if (!uid_eq(rule->src_uid, src))
|
|
continue;
|
|
if (uid_eq(rule->dst_uid, dst))
|
|
return SIDPOL_ALLOWED;
|
|
result = SIDPOL_CONSTRAINED;
|
|
}
|
|
return result;
|
|
}
|
|
|
|
/*
|
|
* Compute a decision for a transition from @src to @dst under the active
|
|
* policy.
|
|
*/
|
|
static enum sid_policy_type setuid_policy_lookup(kuid_t src, kuid_t dst)
|
|
{
|
|
enum sid_policy_type result = SIDPOL_DEFAULT;
|
|
struct setuid_ruleset *pol;
|
|
|
|
rcu_read_lock();
|
|
pol = rcu_dereference(safesetid_setuid_rules);
|
|
if (pol)
|
|
result = _setuid_policy_lookup(pol, src, dst);
|
|
rcu_read_unlock();
|
|
return result;
|
|
}
|
|
|
|
static int safesetid_security_capable(const struct cred *cred,
|
|
struct user_namespace *ns,
|
|
int cap,
|
|
unsigned int opts)
|
|
{
|
|
/* We're only interested in CAP_SETUID. */
|
|
if (cap != CAP_SETUID)
|
|
return 0;
|
|
|
|
/*
|
|
* If CAP_SETUID is currently used for a set*uid() syscall, we want to
|
|
* let it go through here; the real security check happens later, in the
|
|
* task_fix_setuid hook.
|
|
*/
|
|
if ((opts & CAP_OPT_INSETID) != 0)
|
|
return 0;
|
|
|
|
/*
|
|
* If no policy applies to this task, allow the use of CAP_SETUID for
|
|
* other purposes.
|
|
*/
|
|
if (setuid_policy_lookup(cred->uid, INVALID_UID) == SIDPOL_DEFAULT)
|
|
return 0;
|
|
|
|
/*
|
|
* Reject use of CAP_SETUID for functionality other than calling
|
|
* set*uid() (e.g. setting up userns uid mappings).
|
|
*/
|
|
pr_warn("Operation requires CAP_SETUID, which is not available to UID %u for operations besides approved set*uid transitions\n",
|
|
__kuid_val(cred->uid));
|
|
return -EPERM;
|
|
}
|
|
|
|
/*
|
|
* Check whether a caller with old credentials @old is allowed to switch to
|
|
* credentials that contain @new_uid.
|
|
*/
|
|
static bool uid_permitted_for_cred(const struct cred *old, kuid_t new_uid)
|
|
{
|
|
bool permitted;
|
|
|
|
/* If our old creds already had this UID in it, it's fine. */
|
|
if (uid_eq(new_uid, old->uid) || uid_eq(new_uid, old->euid) ||
|
|
uid_eq(new_uid, old->suid))
|
|
return true;
|
|
|
|
/*
|
|
* Transitions to new UIDs require a check against the policy of the old
|
|
* RUID.
|
|
*/
|
|
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),
|
|
__kuid_val(old->suid), __kuid_val(new_uid));
|
|
}
|
|
return permitted;
|
|
}
|
|
|
|
/*
|
|
* Check whether there is either an exception for user under old cred struct to
|
|
* set*uid to user under new cred struct, or the UID transition is allowed (by
|
|
* Linux set*uid rules) even without CAP_SETUID.
|
|
*/
|
|
static int safesetid_task_fix_setuid(struct cred *new,
|
|
const struct cred *old,
|
|
int flags)
|
|
{
|
|
|
|
/* Do nothing if there are no setuid restrictions for our old RUID. */
|
|
if (setuid_policy_lookup(old->uid, INVALID_UID) == SIDPOL_DEFAULT)
|
|
return 0;
|
|
|
|
if (uid_permitted_for_cred(old, new->uid) &&
|
|
uid_permitted_for_cred(old, new->euid) &&
|
|
uid_permitted_for_cred(old, new->suid) &&
|
|
uid_permitted_for_cred(old, new->fsuid))
|
|
return 0;
|
|
|
|
/*
|
|
* Kill this process to avoid potential security vulnerabilities
|
|
* that could arise from a missing whitelist entry preventing a
|
|
* privileged process from dropping to a lesser-privileged one.
|
|
*/
|
|
force_sig(SIGKILL);
|
|
return -EACCES;
|
|
}
|
|
|
|
static struct security_hook_list safesetid_security_hooks[] = {
|
|
LSM_HOOK_INIT(task_fix_setuid, safesetid_task_fix_setuid),
|
|
LSM_HOOK_INIT(capable, safesetid_security_capable)
|
|
};
|
|
|
|
static int __init safesetid_security_init(void)
|
|
{
|
|
security_add_hooks(safesetid_security_hooks,
|
|
ARRAY_SIZE(safesetid_security_hooks), "safesetid");
|
|
|
|
/* Report that SafeSetID successfully initialized */
|
|
safesetid_initialized = 1;
|
|
|
|
return 0;
|
|
}
|
|
|
|
DEFINE_LSM(safesetid_security_init) = {
|
|
.init = safesetid_security_init,
|
|
.name = "safesetid",
|
|
};
|