559 lines
14 KiB
C
559 lines
14 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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sad = a->smack_audit_data;
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if (sad->function == NULL)
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sad->function = "unknown";
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/* end preparing the 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_parse_smack - parse smack label from a text string
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* @string: a text string that might contain a Smack label
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* @len: the maximum size, or zero if it is NULL terminated.
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* @smack: parsed smack label, or NULL if parse error
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*/
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void smk_parse_smack(const char *string, int len, char *smack)
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{
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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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}
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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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smk_parse_smack(string, len, smack);
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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);
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if (kp->smk_cipso->smk_level == level &&
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memcmp(kp->smk_cipso->smk_catset, cp, SMK_LABELLEN) == 0)
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final = kp->smk_known;
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spin_unlock_bh(&kp->smk_cipsolock);
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if (final != NULL)
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break;
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}
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rcu_read_unlock();
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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;
|
|
}
|