415 lines
11 KiB
C
415 lines
11 KiB
C
/*
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* Copyright (C) 2008 IBM Corporation
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* Author: Mimi Zohar <zohar@us.ibm.com>
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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 as published by
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* the Free Software Foundation, version 2 of the License.
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*
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* ima_policy.c
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* - initialize default measure policy rules
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*
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*/
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#include <linux/module.h>
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#include <linux/list.h>
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#include <linux/security.h>
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#include <linux/magic.h>
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#include <linux/parser.h>
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#include "ima.h"
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/* flags definitions */
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#define IMA_FUNC 0x0001
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#define IMA_MASK 0x0002
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#define IMA_FSMAGIC 0x0004
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#define IMA_UID 0x0008
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enum ima_action { UNKNOWN = -1, DONT_MEASURE = 0, MEASURE };
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#define MAX_LSM_RULES 6
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enum lsm_rule_types { LSM_OBJ_USER, LSM_OBJ_ROLE, LSM_OBJ_TYPE,
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LSM_SUBJ_USER, LSM_SUBJ_ROLE, LSM_SUBJ_TYPE
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};
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struct ima_measure_rule_entry {
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struct list_head list;
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enum ima_action action;
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unsigned int flags;
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enum ima_hooks func;
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int mask;
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unsigned long fsmagic;
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uid_t uid;
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struct {
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void *rule; /* LSM file metadata specific */
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int type; /* audit type */
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} lsm[MAX_LSM_RULES];
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};
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/* Without LSM specific knowledge, the default policy can only be
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* written in terms of .action, .func, .mask, .fsmagic, and .uid
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*/
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static struct ima_measure_rule_entry default_rules[] = {
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{.action = DONT_MEASURE,.fsmagic = PROC_SUPER_MAGIC,
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.flags = IMA_FSMAGIC},
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{.action = DONT_MEASURE,.fsmagic = SYSFS_MAGIC,.flags = IMA_FSMAGIC},
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{.action = DONT_MEASURE,.fsmagic = DEBUGFS_MAGIC,.flags = IMA_FSMAGIC},
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{.action = DONT_MEASURE,.fsmagic = TMPFS_MAGIC,.flags = IMA_FSMAGIC},
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{.action = DONT_MEASURE,.fsmagic = SECURITYFS_MAGIC,
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.flags = IMA_FSMAGIC},
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{.action = DONT_MEASURE,.fsmagic = 0xF97CFF8C,.flags = IMA_FSMAGIC},
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{.action = MEASURE,.func = FILE_MMAP,.mask = MAY_EXEC,
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.flags = IMA_FUNC | IMA_MASK},
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{.action = MEASURE,.func = BPRM_CHECK,.mask = MAY_EXEC,
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.flags = IMA_FUNC | IMA_MASK},
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{.action = MEASURE,.func = PATH_CHECK,.mask = MAY_READ,.uid = 0,
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.flags = IMA_FUNC | IMA_MASK | IMA_UID}
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};
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static LIST_HEAD(measure_default_rules);
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static LIST_HEAD(measure_policy_rules);
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static struct list_head *ima_measure;
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static DEFINE_MUTEX(ima_measure_mutex);
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/**
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* ima_match_rules - determine whether an inode matches the measure rule.
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* @rule: a pointer to a rule
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* @inode: a pointer to an inode
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* @func: LIM hook identifier
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* @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC)
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*
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* Returns true on rule match, false on failure.
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*/
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static bool ima_match_rules(struct ima_measure_rule_entry *rule,
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struct inode *inode, enum ima_hooks func, int mask)
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{
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struct task_struct *tsk = current;
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int i;
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if ((rule->flags & IMA_FUNC) && rule->func != func)
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return false;
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if ((rule->flags & IMA_MASK) && rule->mask != mask)
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return false;
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if ((rule->flags & IMA_FSMAGIC)
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&& rule->fsmagic != inode->i_sb->s_magic)
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return false;
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if ((rule->flags & IMA_UID) && rule->uid != tsk->cred->uid)
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return false;
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for (i = 0; i < MAX_LSM_RULES; i++) {
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int rc;
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u32 osid, sid;
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if (!rule->lsm[i].rule)
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continue;
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switch (i) {
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case LSM_OBJ_USER:
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case LSM_OBJ_ROLE:
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case LSM_OBJ_TYPE:
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security_inode_getsecid(inode, &osid);
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rc = security_filter_rule_match(osid,
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rule->lsm[i].type,
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AUDIT_EQUAL,
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rule->lsm[i].rule,
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NULL);
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break;
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case LSM_SUBJ_USER:
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case LSM_SUBJ_ROLE:
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case LSM_SUBJ_TYPE:
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security_task_getsecid(tsk, &sid);
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rc = security_filter_rule_match(sid,
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rule->lsm[i].type,
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AUDIT_EQUAL,
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rule->lsm[i].rule,
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NULL);
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default:
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break;
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}
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if (!rc)
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return false;
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}
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return true;
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}
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/**
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* ima_match_policy - decision based on LSM and other conditions
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* @inode: pointer to an inode for which the policy decision is being made
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* @func: IMA hook identifier
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* @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC)
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*
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* Measure decision based on func/mask/fsmagic and LSM(subj/obj/type)
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* conditions.
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*
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* (There is no need for locking when walking the policy list,
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* as elements in the list are never deleted, nor does the list
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* change.)
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*/
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int ima_match_policy(struct inode *inode, enum ima_hooks func, int mask)
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{
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struct ima_measure_rule_entry *entry;
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list_for_each_entry(entry, ima_measure, list) {
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bool rc;
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rc = ima_match_rules(entry, inode, func, mask);
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if (rc)
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return entry->action;
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}
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return 0;
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}
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/**
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* ima_init_policy - initialize the default measure rules.
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*
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* ima_measure points to either the measure_default_rules or the
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* the new measure_policy_rules.
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*/
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void ima_init_policy(void)
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{
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int i;
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for (i = 0; i < ARRAY_SIZE(default_rules); i++)
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list_add_tail(&default_rules[i].list, &measure_default_rules);
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ima_measure = &measure_default_rules;
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}
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/**
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* ima_update_policy - update default_rules with new measure rules
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*
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* Called on file .release to update the default rules with a complete new
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* policy. Once updated, the policy is locked, no additional rules can be
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* added to the policy.
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*/
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void ima_update_policy(void)
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{
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const char *op = "policy_update";
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const char *cause = "already exists";
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int result = 1;
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int audit_info = 0;
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if (ima_measure == &measure_default_rules) {
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ima_measure = &measure_policy_rules;
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cause = "complete";
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result = 0;
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}
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integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
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NULL, op, cause, result, audit_info);
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}
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enum {
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Opt_err = -1,
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Opt_measure = 1, Opt_dont_measure,
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Opt_obj_user, Opt_obj_role, Opt_obj_type,
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Opt_subj_user, Opt_subj_role, Opt_subj_type,
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Opt_func, Opt_mask, Opt_fsmagic, Opt_uid
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};
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static match_table_t policy_tokens = {
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{Opt_measure, "measure"},
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{Opt_dont_measure, "dont_measure"},
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{Opt_obj_user, "obj_user=%s"},
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{Opt_obj_role, "obj_role=%s"},
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{Opt_obj_type, "obj_type=%s"},
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{Opt_subj_user, "subj_user=%s"},
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{Opt_subj_role, "subj_role=%s"},
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{Opt_subj_type, "subj_type=%s"},
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{Opt_func, "func=%s"},
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{Opt_mask, "mask=%s"},
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{Opt_fsmagic, "fsmagic=%s"},
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{Opt_uid, "uid=%s"},
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{Opt_err, NULL}
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};
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static int ima_lsm_rule_init(struct ima_measure_rule_entry *entry,
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char *args, int lsm_rule, int audit_type)
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{
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int result;
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entry->lsm[lsm_rule].type = audit_type;
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result = security_filter_rule_init(entry->lsm[lsm_rule].type,
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AUDIT_EQUAL, args,
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&entry->lsm[lsm_rule].rule);
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return result;
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}
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static int ima_parse_rule(char *rule, struct ima_measure_rule_entry *entry)
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{
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struct audit_buffer *ab;
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char *p;
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int result = 0;
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ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_INTEGRITY_RULE);
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entry->action = -1;
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while ((p = strsep(&rule, " \n")) != NULL) {
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substring_t args[MAX_OPT_ARGS];
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int token;
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unsigned long lnum;
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if (result < 0)
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break;
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if (!*p)
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continue;
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token = match_token(p, policy_tokens, args);
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switch (token) {
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case Opt_measure:
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audit_log_format(ab, "%s ", "measure");
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entry->action = MEASURE;
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break;
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case Opt_dont_measure:
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audit_log_format(ab, "%s ", "dont_measure");
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entry->action = DONT_MEASURE;
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break;
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case Opt_func:
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audit_log_format(ab, "func=%s ", args[0].from);
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if (strcmp(args[0].from, "PATH_CHECK") == 0)
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entry->func = PATH_CHECK;
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else if (strcmp(args[0].from, "FILE_MMAP") == 0)
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entry->func = FILE_MMAP;
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else if (strcmp(args[0].from, "BPRM_CHECK") == 0)
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entry->func = BPRM_CHECK;
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else
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result = -EINVAL;
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if (!result)
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entry->flags |= IMA_FUNC;
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break;
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case Opt_mask:
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audit_log_format(ab, "mask=%s ", args[0].from);
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if ((strcmp(args[0].from, "MAY_EXEC")) == 0)
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entry->mask = MAY_EXEC;
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else if (strcmp(args[0].from, "MAY_WRITE") == 0)
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entry->mask = MAY_WRITE;
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else if (strcmp(args[0].from, "MAY_READ") == 0)
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entry->mask = MAY_READ;
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else if (strcmp(args[0].from, "MAY_APPEND") == 0)
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entry->mask = MAY_APPEND;
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else
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result = -EINVAL;
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if (!result)
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entry->flags |= IMA_MASK;
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break;
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case Opt_fsmagic:
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audit_log_format(ab, "fsmagic=%s ", args[0].from);
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result = strict_strtoul(args[0].from, 16,
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&entry->fsmagic);
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if (!result)
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entry->flags |= IMA_FSMAGIC;
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break;
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case Opt_uid:
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audit_log_format(ab, "uid=%s ", args[0].from);
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result = strict_strtoul(args[0].from, 10, &lnum);
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if (!result) {
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entry->uid = (uid_t) lnum;
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if (entry->uid != lnum)
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result = -EINVAL;
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else
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entry->flags |= IMA_UID;
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}
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break;
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case Opt_obj_user:
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audit_log_format(ab, "obj_user=%s ", args[0].from);
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result = ima_lsm_rule_init(entry, args[0].from,
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LSM_OBJ_USER,
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AUDIT_OBJ_USER);
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break;
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case Opt_obj_role:
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audit_log_format(ab, "obj_role=%s ", args[0].from);
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result = ima_lsm_rule_init(entry, args[0].from,
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LSM_OBJ_ROLE,
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AUDIT_OBJ_ROLE);
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break;
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case Opt_obj_type:
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audit_log_format(ab, "obj_type=%s ", args[0].from);
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result = ima_lsm_rule_init(entry, args[0].from,
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LSM_OBJ_TYPE,
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AUDIT_OBJ_TYPE);
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break;
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case Opt_subj_user:
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audit_log_format(ab, "subj_user=%s ", args[0].from);
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result = ima_lsm_rule_init(entry, args[0].from,
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LSM_SUBJ_USER,
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AUDIT_SUBJ_USER);
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break;
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case Opt_subj_role:
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audit_log_format(ab, "subj_role=%s ", args[0].from);
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result = ima_lsm_rule_init(entry, args[0].from,
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LSM_SUBJ_ROLE,
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AUDIT_SUBJ_ROLE);
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break;
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case Opt_subj_type:
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audit_log_format(ab, "subj_type=%s ", args[0].from);
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result = ima_lsm_rule_init(entry, args[0].from,
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LSM_SUBJ_TYPE,
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AUDIT_SUBJ_TYPE);
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break;
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case Opt_err:
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audit_log_format(ab, "UNKNOWN=%s ", p);
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break;
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}
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}
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if (entry->action == UNKNOWN)
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result = -EINVAL;
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audit_log_format(ab, "res=%d", !result ? 0 : 1);
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audit_log_end(ab);
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return result;
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}
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/**
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* ima_parse_add_rule - add a rule to measure_policy_rules
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* @rule - ima measurement policy rule
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*
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* Uses a mutex to protect the policy list from multiple concurrent writers.
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* Returns 0 on success, an error code on failure.
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*/
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int ima_parse_add_rule(char *rule)
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{
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const char *op = "update_policy";
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struct ima_measure_rule_entry *entry;
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int result = 0;
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int audit_info = 0;
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/* Prevent installed policy from changing */
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if (ima_measure != &measure_default_rules) {
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integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
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NULL, op, "already exists",
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-EACCES, audit_info);
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return -EACCES;
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}
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entry = kzalloc(sizeof(*entry), GFP_KERNEL);
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if (!entry) {
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integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
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NULL, op, "-ENOMEM", -ENOMEM, audit_info);
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return -ENOMEM;
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}
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INIT_LIST_HEAD(&entry->list);
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result = ima_parse_rule(rule, entry);
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if (!result) {
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mutex_lock(&ima_measure_mutex);
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list_add_tail(&entry->list, &measure_policy_rules);
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mutex_unlock(&ima_measure_mutex);
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} else {
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kfree(entry);
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integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
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NULL, op, "invalid policy", result,
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audit_info);
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}
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return result;
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}
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/* ima_delete_rules called to cleanup invalid policy */
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void ima_delete_rules(void)
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{
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struct ima_measure_rule_entry *entry, *tmp;
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mutex_lock(&ima_measure_mutex);
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list_for_each_entry_safe(entry, tmp, &measure_policy_rules, list) {
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list_del(&entry->list);
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kfree(entry);
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}
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mutex_unlock(&ima_measure_mutex);
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}
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