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/*
* Copyright (C) 2008 IBM Corporation
* Author: Mimi Zohar <zohar@us.ibm.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, version 2 of the License.
*
* ima_policy.c
* - initialize default measure policy rules
*
*/
#include <linux/module.h>
#include <linux/list.h>
#include <linux/audit.h>
#include <linux/security.h>
#include <linux/magic.h>
#include "ima.h"
/* flags definitions */
#define IMA_FUNC 0x0001
#define IMA_MASK 0x0002
#define IMA_FSMAGIC 0x0004
#define IMA_UID 0x0008
enum ima_action { DONT_MEASURE, MEASURE };
struct ima_measure_rule_entry {
struct list_head list;
enum ima_action action;
unsigned int flags;
enum ima_hooks func;
int mask;
unsigned long fsmagic;
uid_t uid;
};
static struct ima_measure_rule_entry default_rules[] = {
{.action = DONT_MEASURE,.fsmagic = PROC_SUPER_MAGIC,
.flags = IMA_FSMAGIC},
{.action = DONT_MEASURE,.fsmagic = SYSFS_MAGIC,.flags = IMA_FSMAGIC},
{.action = DONT_MEASURE,.fsmagic = DEBUGFS_MAGIC,.flags = IMA_FSMAGIC},
{.action = DONT_MEASURE,.fsmagic = TMPFS_MAGIC,.flags = IMA_FSMAGIC},
{.action = DONT_MEASURE,.fsmagic = SECURITYFS_MAGIC,
.flags = IMA_FSMAGIC},
{.action = DONT_MEASURE,.fsmagic = 0xF97CFF8C,.flags = IMA_FSMAGIC},
{.action = MEASURE,.func = FILE_MMAP,.mask = MAY_EXEC,
.flags = IMA_FUNC | IMA_MASK},
{.action = MEASURE,.func = BPRM_CHECK,.mask = MAY_EXEC,
.flags = IMA_FUNC | IMA_MASK},
{.action = MEASURE,.func = PATH_CHECK,.mask = MAY_READ,.uid = 0,
.flags = IMA_FUNC | IMA_MASK | IMA_UID}
};
static LIST_HEAD(measure_default_rules);
static struct list_head *ima_measure;
/**
* ima_match_rules - determine whether an inode matches the measure rule.
* @rule: a pointer to a rule
* @inode: a pointer to an inode
* @func: LIM hook identifier
* @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC)
*
* Returns true on rule match, false on failure.
*/
static bool ima_match_rules(struct ima_measure_rule_entry *rule,
struct inode *inode, enum ima_hooks func, int mask)
{
struct task_struct *tsk = current;
if ((rule->flags & IMA_FUNC) && rule->func != func)
return false;
if ((rule->flags & IMA_MASK) && rule->mask != mask)
return false;
if ((rule->flags & IMA_FSMAGIC)
&& rule->fsmagic != inode->i_sb->s_magic)
return false;
if ((rule->flags & IMA_UID) && rule->uid != tsk->cred->uid)
return false;
return true;
}
/**
* ima_match_policy - decision based on LSM and other conditions
* @inode: pointer to an inode for which the policy decision is being made
* @func: IMA hook identifier
* @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC)
*
* Measure decision based on func/mask/fsmagic and LSM(subj/obj/type)
* conditions.
*
* (There is no need for locking when walking the policy list,
* as elements in the list are never deleted, nor does the list
* change.)
*/
int ima_match_policy(struct inode *inode, enum ima_hooks func, int mask)
{
struct ima_measure_rule_entry *entry;
list_for_each_entry(entry, ima_measure, list) {
bool rc;
rc = ima_match_rules(entry, inode, func, mask);
if (rc)
return entry->action;
}
return 0;
}
/**
* ima_init_policy - initialize the default measure rules.
*
* (Could use the default_rules directly, but in policy patch
* ima_measure points to either the measure_default_rules or the
* the new measure_policy_rules.)
*/
void ima_init_policy(void)
{
int i;
for (i = 0; i < ARRAY_SIZE(default_rules); i++)
list_add_tail(&default_rules[i].list, &measure_default_rules);
ima_measure = &measure_default_rules;
}
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