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/*
* Copyright (C) 2007 Casey Schaufler <casey@schaufler-ca.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, version 2.
*
* Author:
* Casey Schaufler <casey@schaufler-ca.com>
*
*/
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/sched.h>
#include "smack.h"
struct smack_known smack_known_huh = {
.smk_known = "?",
.smk_secid = 2,
};
struct smack_known smack_known_hat = {
.smk_known = "^",
.smk_secid = 3,
};
struct smack_known smack_known_star = {
.smk_known = "*",
.smk_secid = 4,
};
struct smack_known smack_known_floor = {
.smk_known = "_",
.smk_secid = 5,
};
struct smack_known smack_known_web = {
.smk_known = "@",
.smk_secid = 7,
};
LIST_HEAD(smack_known_list);
/*
* The initial value needs to be bigger than any of the
* known values above.
*/
static u32 smack_next_secid = 10;
/*
* what events do we log
* can be overwritten at run-time by /smack/logging
*/
int log_policy = SMACK_AUDIT_DENIED;
/**
* smk_access_entry - look up matching access rule
* @subject_label: a pointer to the subject's Smack label
* @object_label: a pointer to the object's Smack label
* @rule_list: the list of rules to search
*
* This function looks up the subject/object pair in the
* access rule list and returns the access mode. If no
* entry is found returns -ENOENT.
*
* NOTE:
*
* Earlier versions of this function allowed for labels that
* were not on the label list. This was done to allow for
* labels to come over the network that had never been seen
* before on this host. Unless the receiving socket has the
* star label this will always result in a failure check. The
* star labeled socket case is now handled in the networking
* hooks so there is no case where the label is not on the
* label list. Checking to see if the address of two labels
* is the same is now a reliable test.
*
* Do the object check first because that is more
* likely to differ.
*
* Allowing write access implies allowing locking.
*/
int smk_access_entry(char *subject_label, char *object_label,
struct list_head *rule_list)
{
int may = -ENOENT;
struct smack_rule *srp;
list_for_each_entry_rcu(srp, rule_list, list) {
if (srp->smk_object->smk_known == object_label &&
srp->smk_subject->smk_known == subject_label) {
may = srp->smk_access;
break;
}
}
/*
* MAY_WRITE implies MAY_LOCK.
*/
if ((may & MAY_WRITE) == MAY_WRITE)
may |= MAY_LOCK;
return may;
}
/**
* smk_access - determine if a subject has a specific access to an object
* @subject: a pointer to the subject's Smack label entry
* @object: a pointer to the object's Smack label entry
* @request: the access requested, in "MAY" format
* @a : a pointer to the audit data
*
* This function looks up the subject/object pair in the
* access rule list and returns 0 if the access is permitted,
* non zero otherwise.
*
* Smack labels are shared on smack_list
*/
int smk_access(struct smack_known *subject, struct smack_known *object,
int request, struct smk_audit_info *a)
{
int may = MAY_NOT;
int rc = 0;
/*
* Hardcoded comparisons.
*/
/*
* A star subject can't access any object.
*/
if (subject == &smack_known_star) {
rc = -EACCES;
goto out_audit;
}
/*
* An internet object can be accessed by any subject.
* Tasks cannot be assigned the internet label.
* An internet subject can access any object.
*/
if (object == &smack_known_web || subject == &smack_known_web)
goto out_audit;
/*
* A star object can be accessed by any subject.
*/
if (object == &smack_known_star)
goto out_audit;
/*
* An object can be accessed in any way by a subject
* with the same label.
*/
if (subject->smk_known == object->smk_known)
goto out_audit;
/*
* A hat subject can read or lock any object.
* A floor object can be read or locked by any subject.
*/
if ((request & MAY_ANYREAD) == request ||
(request & MAY_LOCK) == request) {
if (object == &smack_known_floor)
goto out_audit;
if (subject == &smack_known_hat)
goto out_audit;
}
/*
* Beyond here an explicit relationship is required.
* If the requested access is contained in the available
* access (e.g. read is included in readwrite) it's
* good. A negative response from smk_access_entry()
* indicates there is no entry for this pair.
*/
rcu_read_lock();
may = smk_access_entry(subject->smk_known, object->smk_known,
&subject->smk_rules);
rcu_read_unlock();
if (may <= 0 || (request & may) != request) {
rc = -EACCES;
goto out_audit;
}
#ifdef CONFIG_SECURITY_SMACK_BRINGUP
/*
* Return a positive value if using bringup mode.
* This allows the hooks to identify checks that
* succeed because of "b" rules.
*/
if (may & MAY_BRINGUP)
rc = SMACK_BRINGUP_ALLOW;
#endif
out_audit:
#ifdef CONFIG_SECURITY_SMACK_BRINGUP
if (rc < 0) {
if (object == smack_unconfined)
rc = SMACK_UNCONFINED_OBJECT;
if (subject == smack_unconfined)
rc = SMACK_UNCONFINED_SUBJECT;
}
#endif
#ifdef CONFIG_AUDIT
if (a)
smack_log(subject->smk_known, object->smk_known,
request, rc, a);
#endif
return rc;
}
/**
* smk_tskacc - determine if a task has a specific access to an object
* @tsp: a pointer to the subject's task
* @obj_known: a pointer to the object's label entry
* @mode: the access requested, in "MAY" format
* @a : common audit data
*
* This function checks the subject task's label/object label pair
* in the access rule list and returns 0 if the access is permitted,
* non zero otherwise. It allows that the task may have the capability
* to override the rules.
*/
int smk_tskacc(struct task_smack *tsp, struct smack_known *obj_known,
u32 mode, struct smk_audit_info *a)
{
struct smack_known *sbj_known = smk_of_task(tsp);
int may;
int rc;
/*
* Check the global rule list
*/
rc = smk_access(sbj_known, obj_known, mode, NULL);
if (rc >= 0) {
/*
* If there is an entry in the task's rule list
* it can further restrict access.
*/
may = smk_access_entry(sbj_known->smk_known,
obj_known->smk_known,
&tsp->smk_rules);
if (may < 0)
goto out_audit;
if ((mode & may) == mode)
goto out_audit;
rc = -EACCES;
}
/*
* Allow for priviliged to override policy.
*/
if (rc != 0 && smack_privileged(CAP_MAC_OVERRIDE))
rc = 0;
out_audit:
#ifdef CONFIG_AUDIT
if (a)
smack_log(sbj_known->smk_known, obj_known->smk_known,
mode, rc, a);
#endif
return rc;
}
/**
* smk_curacc - determine if current has a specific access to an object
* @obj_known: a pointer to the object's Smack label entry
* @mode: the access requested, in "MAY" format
* @a : common audit data
*
* This function checks the current subject label/object label pair
* in the access rule list and returns 0 if the access is permitted,
* non zero otherwise. It allows that current may have the capability
* to override the rules.
*/
int smk_curacc(struct smack_known *obj_known,
u32 mode, struct smk_audit_info *a)
{
struct task_smack *tsp = current_security();
return smk_tskacc(tsp, obj_known, mode, a);
}
#ifdef CONFIG_AUDIT
/**
* smack_str_from_perm : helper to transalate an int to a
* readable string
* @string : the string to fill
* @access : the int
*
*/
static inline void smack_str_from_perm(char *string, int access)
{
int i = 0;
if (access & MAY_READ)
string[i++] = 'r';
if (access
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