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272cd7a8c6
This patch is targeted for the smack-next tree. Smack access checks suffer from two significant performance issues. In cases where there are large numbers of rules the search of the single list of rules is wasteful. Comparing the string values of the smack labels is less efficient than a numeric comparison would. These changes take advantage of the Smack label list, which maintains the mapping of Smack labels to secids and optional CIPSO labels. Because the labels are kept perpetually, an access check can be done strictly based on the address of the label in the list without ever looking at the label itself. Rather than keeping one global list of rules the rules with a particular subject label can be based off of that label list entry. The access check need never look at entries that do not use the current subject label. This requires that packets coming off the network with CIPSO direct Smack labels that have never been seen before be treated carefully. The only case where they could be delivered is where the receiving socket has an IPIN star label, so that case is explicitly addressed. On a system with 39,800 rules (200 labels in all permutations) a system with this patch runs an access speed test in 5% of the time of the old version. That should be a best case improvement. If all of the rules are associated with the same subject label and all of the accesses are for processes with that label (unlikely) the improvement is about 30%. Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
547 lines
13 KiB
C
547 lines
13 KiB
C
/*
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* Copyright (C) 2007 Casey Schaufler <casey@schaufler-ca.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.
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*
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* Author:
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* Casey Schaufler <casey@schaufler-ca.com>
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*
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*/
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#include <linux/types.h>
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#include <linux/slab.h>
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#include <linux/fs.h>
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#include <linux/sched.h>
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#include "smack.h"
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struct smack_known smack_known_huh = {
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.smk_known = "?",
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.smk_secid = 2,
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.smk_cipso = NULL,
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};
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struct smack_known smack_known_hat = {
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.smk_known = "^",
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.smk_secid = 3,
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.smk_cipso = NULL,
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};
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struct smack_known smack_known_star = {
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.smk_known = "*",
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.smk_secid = 4,
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.smk_cipso = NULL,
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};
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struct smack_known smack_known_floor = {
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.smk_known = "_",
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.smk_secid = 5,
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.smk_cipso = NULL,
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};
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struct smack_known smack_known_invalid = {
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.smk_known = "",
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.smk_secid = 6,
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.smk_cipso = NULL,
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};
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struct smack_known smack_known_web = {
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.smk_known = "@",
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.smk_secid = 7,
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.smk_cipso = NULL,
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};
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LIST_HEAD(smack_known_list);
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/*
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* The initial value needs to be bigger than any of the
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* known values above.
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*/
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static u32 smack_next_secid = 10;
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/*
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* what events do we log
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* can be overwritten at run-time by /smack/logging
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*/
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int log_policy = SMACK_AUDIT_DENIED;
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/**
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* smk_access_entry - look up matching access rule
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* @subject_label: a pointer to the subject's Smack label
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* @object_label: a pointer to the object's Smack label
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* @rule_list: the list of rules to search
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*
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* This function looks up the subject/object pair in the
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* access rule list and returns the access mode. If no
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* entry is found returns -ENOENT.
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*
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* NOTE:
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*
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* Earlier versions of this function allowed for labels that
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* were not on the label list. This was done to allow for
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* labels to come over the network that had never been seen
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* before on this host. Unless the receiving socket has the
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* star label this will always result in a failure check. The
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* star labeled socket case is now handled in the networking
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* hooks so there is no case where the label is not on the
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* label list. Checking to see if the address of two labels
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* is the same is now a reliable test.
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*
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* Do the object check first because that is more
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* likely to differ.
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*/
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int smk_access_entry(char *subject_label, char *object_label,
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struct list_head *rule_list)
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{
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int may = -ENOENT;
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struct smack_rule *srp;
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list_for_each_entry_rcu(srp, rule_list, list) {
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if (srp->smk_object == object_label &&
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srp->smk_subject == subject_label) {
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may = srp->smk_access;
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break;
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}
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}
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return may;
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}
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/**
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* smk_access - determine if a subject has a specific access to an object
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* @subject_label: a pointer to the subject's Smack label
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* @object_label: a pointer to the object's Smack label
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* @request: the access requested, in "MAY" format
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* @a : a pointer to the audit data
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*
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* This function looks up the subject/object pair in the
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* access rule list and returns 0 if the access is permitted,
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* non zero otherwise.
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*
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* Smack labels are shared on smack_list
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*/
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int smk_access(char *subject_label, char *object_label, int request,
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struct smk_audit_info *a)
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{
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struct smack_known *skp;
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int may = MAY_NOT;
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int rc = 0;
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/*
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* Hardcoded comparisons.
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*
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* A star subject can't access any object.
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*/
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if (subject_label == smack_known_star.smk_known) {
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rc = -EACCES;
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goto out_audit;
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}
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/*
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* An internet object can be accessed by any subject.
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* Tasks cannot be assigned the internet label.
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* An internet subject can access any object.
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*/
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if (object_label == smack_known_web.smk_known ||
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subject_label == smack_known_web.smk_known)
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goto out_audit;
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/*
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* A star object can be accessed by any subject.
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*/
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if (object_label == smack_known_star.smk_known)
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goto out_audit;
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/*
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* An object can be accessed in any way by a subject
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* with the same label.
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*/
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if (subject_label == object_label)
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goto out_audit;
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/*
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* A hat subject can read any object.
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* A floor object can be read by any subject.
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*/
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if ((request & MAY_ANYREAD) == request) {
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if (object_label == smack_known_floor.smk_known)
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goto out_audit;
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if (subject_label == smack_known_hat.smk_known)
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goto out_audit;
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}
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/*
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* Beyond here an explicit relationship is required.
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* If the requested access is contained in the available
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* access (e.g. read is included in readwrite) it's
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* good. A negative response from smk_access_entry()
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* indicates there is no entry for this pair.
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*/
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skp = smk_find_entry(subject_label);
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rcu_read_lock();
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may = smk_access_entry(subject_label, object_label, &skp->smk_rules);
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rcu_read_unlock();
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if (may > 0 && (request & may) == request)
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goto out_audit;
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rc = -EACCES;
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out_audit:
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#ifdef CONFIG_AUDIT
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if (a)
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smack_log(subject_label, object_label, request, rc, a);
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#endif
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return rc;
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}
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/**
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* smk_curacc - determine if current has a specific access to an object
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* @obj_label: a pointer to the object's Smack label
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* @mode: the access requested, in "MAY" format
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* @a : common audit data
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*
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* This function checks the current subject label/object label pair
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* in the access rule list and returns 0 if the access is permitted,
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* non zero otherwise. It allows that current may have the capability
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* to override the rules.
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*/
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int smk_curacc(char *obj_label, u32 mode, struct smk_audit_info *a)
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{
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struct task_smack *tsp = current_security();
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char *sp = smk_of_task(tsp);
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int may;
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int rc;
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/*
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* Check the global rule list
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*/
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rc = smk_access(sp, obj_label, mode, NULL);
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if (rc == 0) {
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/*
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* If there is an entry in the task's rule list
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* it can further restrict access.
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*/
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may = smk_access_entry(sp, obj_label, &tsp->smk_rules);
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if (may < 0)
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goto out_audit;
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if ((mode & may) == mode)
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goto out_audit;
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rc = -EACCES;
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}
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/*
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* Return if a specific label has been designated as the
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* only one that gets privilege and current does not
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* have that label.
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*/
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if (smack_onlycap != NULL && smack_onlycap != sp)
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goto out_audit;
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if (capable(CAP_MAC_OVERRIDE))
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rc = 0;
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out_audit:
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#ifdef CONFIG_AUDIT
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if (a)
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smack_log(sp, obj_label, mode, rc, a);
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#endif
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return rc;
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}
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#ifdef CONFIG_AUDIT
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/**
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* smack_str_from_perm : helper to transalate an int to a
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* readable string
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* @string : the string to fill
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* @access : the int
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*
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*/
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static inline void smack_str_from_perm(char *string, int access)
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{
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int i = 0;
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if (access & MAY_READ)
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string[i++] = 'r';
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if (access & MAY_WRITE)
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string[i++] = 'w';
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if (access & MAY_EXEC)
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string[i++] = 'x';
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if (access & MAY_APPEND)
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string[i++] = 'a';
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string[i] = '\0';
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}
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/**
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* smack_log_callback - SMACK specific information
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* will be called by generic audit code
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* @ab : the audit_buffer
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* @a : audit_data
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*
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*/
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static void smack_log_callback(struct audit_buffer *ab, void *a)
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{
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struct common_audit_data *ad = a;
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struct smack_audit_data *sad = &ad->smack_audit_data;
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audit_log_format(ab, "lsm=SMACK fn=%s action=%s",
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ad->smack_audit_data.function,
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sad->result ? "denied" : "granted");
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audit_log_format(ab, " subject=");
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audit_log_untrustedstring(ab, sad->subject);
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audit_log_format(ab, " object=");
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audit_log_untrustedstring(ab, sad->object);
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audit_log_format(ab, " requested=%s", sad->request);
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}
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/**
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* smack_log - Audit the granting or denial of permissions.
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* @subject_label : smack label of the requester
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* @object_label : smack label of the object being accessed
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* @request: requested permissions
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* @result: result from smk_access
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* @a: auxiliary audit data
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*
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* Audit the granting or denial of permissions in accordance
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* with the policy.
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*/
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void smack_log(char *subject_label, char *object_label, int request,
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int result, struct smk_audit_info *ad)
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{
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char request_buffer[SMK_NUM_ACCESS_TYPE + 1];
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struct smack_audit_data *sad;
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struct common_audit_data *a = &ad->a;
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/* check if we have to log the current event */
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if (result != 0 && (log_policy & SMACK_AUDIT_DENIED) == 0)
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return;
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if (result == 0 && (log_policy & SMACK_AUDIT_ACCEPT) == 0)
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return;
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if (a->smack_audit_data.function == NULL)
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a->smack_audit_data.function = "unknown";
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/* end preparing the audit data */
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sad = &a->smack_audit_data;
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smack_str_from_perm(request_buffer, request);
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sad->subject = subject_label;
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sad->object = object_label;
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sad->request = request_buffer;
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sad->result = result;
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a->lsm_pre_audit = smack_log_callback;
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common_lsm_audit(a);
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}
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#else /* #ifdef CONFIG_AUDIT */
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void smack_log(char *subject_label, char *object_label, int request,
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int result, struct smk_audit_info *ad)
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{
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}
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#endif
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static DEFINE_MUTEX(smack_known_lock);
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/**
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* smk_find_entry - find a label on the list, return the list entry
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* @string: a text string that might be a Smack label
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*
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* Returns a pointer to the entry in the label list that
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* matches the passed string.
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*/
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struct smack_known *smk_find_entry(const char *string)
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{
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struct smack_known *skp;
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list_for_each_entry_rcu(skp, &smack_known_list, list) {
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if (strncmp(skp->smk_known, string, SMK_MAXLEN) == 0)
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return skp;
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}
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return NULL;
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}
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/**
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* smk_import_entry - import a label, return the list entry
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* @string: a text string that might be a Smack label
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* @len: the maximum size, or zero if it is NULL terminated.
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*
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* Returns a pointer to the entry in the label list that
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* matches the passed string, adding it if necessary.
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*/
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struct smack_known *smk_import_entry(const char *string, int len)
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{
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struct smack_known *skp;
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char smack[SMK_LABELLEN];
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int found;
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int i;
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if (len <= 0 || len > SMK_MAXLEN)
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len = SMK_MAXLEN;
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for (i = 0, found = 0; i < SMK_LABELLEN; i++) {
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if (found)
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smack[i] = '\0';
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else if (i >= len || string[i] > '~' || string[i] <= ' ' ||
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string[i] == '/' || string[i] == '"' ||
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string[i] == '\\' || string[i] == '\'') {
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smack[i] = '\0';
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found = 1;
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} else
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smack[i] = string[i];
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}
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if (smack[0] == '\0')
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return NULL;
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mutex_lock(&smack_known_lock);
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skp = smk_find_entry(smack);
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if (skp == NULL) {
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skp = kzalloc(sizeof(struct smack_known), GFP_KERNEL);
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if (skp != NULL) {
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strncpy(skp->smk_known, smack, SMK_MAXLEN);
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skp->smk_secid = smack_next_secid++;
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skp->smk_cipso = NULL;
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INIT_LIST_HEAD(&skp->smk_rules);
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spin_lock_init(&skp->smk_cipsolock);
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mutex_init(&skp->smk_rules_lock);
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/*
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* Make sure that the entry is actually
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* filled before putting it on the list.
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*/
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list_add_rcu(&skp->list, &smack_known_list);
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}
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}
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mutex_unlock(&smack_known_lock);
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return skp;
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}
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/**
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* smk_import - import a smack label
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* @string: a text string that might be a Smack label
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* @len: the maximum size, or zero if it is NULL terminated.
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*
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* Returns a pointer to the label in the label list that
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* matches the passed string, adding it if necessary.
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*/
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char *smk_import(const char *string, int len)
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{
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struct smack_known *skp;
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/* labels cannot begin with a '-' */
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if (string[0] == '-')
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return NULL;
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skp = smk_import_entry(string, len);
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if (skp == NULL)
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return NULL;
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return skp->smk_known;
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}
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/**
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* smack_from_secid - find the Smack label associated with a secid
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* @secid: an integer that might be associated with a Smack label
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*
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* Returns a pointer to the appropriate Smack label if there is one,
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* otherwise a pointer to the invalid Smack label.
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*/
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char *smack_from_secid(const u32 secid)
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{
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struct smack_known *skp;
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rcu_read_lock();
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list_for_each_entry_rcu(skp, &smack_known_list, list) {
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if (skp->smk_secid == secid) {
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rcu_read_unlock();
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return skp->smk_known;
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}
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}
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/*
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* If we got this far someone asked for the translation
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* of a secid that is not on the list.
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*/
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rcu_read_unlock();
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return smack_known_invalid.smk_known;
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}
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/**
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* smack_to_secid - find the secid associated with a Smack label
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* @smack: the Smack label
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*
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* Returns the appropriate secid if there is one,
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* otherwise 0
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*/
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u32 smack_to_secid(const char *smack)
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{
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struct smack_known *skp;
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rcu_read_lock();
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list_for_each_entry_rcu(skp, &smack_known_list, list) {
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if (strncmp(skp->smk_known, smack, SMK_MAXLEN) == 0) {
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rcu_read_unlock();
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return skp->smk_secid;
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}
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}
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rcu_read_unlock();
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return 0;
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}
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/**
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* smack_from_cipso - find the Smack label associated with a CIPSO option
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* @level: Bell & LaPadula level from the network
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* @cp: Bell & LaPadula categories from the network
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*
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* This is a simple lookup in the label table.
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*
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* Return the matching label from the label list or NULL.
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*/
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char *smack_from_cipso(u32 level, char *cp)
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{
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struct smack_known *kp;
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char *final = NULL;
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rcu_read_lock();
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list_for_each_entry(kp, &smack_known_list, list) {
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if (kp->smk_cipso == NULL)
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continue;
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spin_lock_bh(&kp->smk_cipsolock);
|
|
|
|
if (kp->smk_cipso->smk_level == level &&
|
|
memcmp(kp->smk_cipso->smk_catset, cp, SMK_LABELLEN) == 0)
|
|
final = kp->smk_known;
|
|
|
|
spin_unlock_bh(&kp->smk_cipsolock);
|
|
|
|
if (final != NULL)
|
|
break;
|
|
}
|
|
rcu_read_unlock();
|
|
|
|
return final;
|
|
}
|
|
|
|
/**
|
|
* smack_to_cipso - find the CIPSO option to go with a Smack label
|
|
* @smack: a pointer to the smack label in question
|
|
* @cp: where to put the result
|
|
*
|
|
* Returns zero if a value is available, non-zero otherwise.
|
|
*/
|
|
int smack_to_cipso(const char *smack, struct smack_cipso *cp)
|
|
{
|
|
struct smack_known *kp;
|
|
int found = 0;
|
|
|
|
rcu_read_lock();
|
|
list_for_each_entry_rcu(kp, &smack_known_list, list) {
|
|
if (kp->smk_known == smack ||
|
|
strcmp(kp->smk_known, smack) == 0) {
|
|
found = 1;
|
|
break;
|
|
}
|
|
}
|
|
rcu_read_unlock();
|
|
|
|
if (found == 0 || kp->smk_cipso == NULL)
|
|
return -ENOENT;
|
|
|
|
memcpy(cp, kp->smk_cipso, sizeof(struct smack_cipso));
|
|
return 0;
|
|
}
|