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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,
.smk_cipso = NULL,
};
struct smack_known smack_known_hat = {
.smk_known = "^",
.smk_secid = 3,
.smk_cipso = NULL,
};
struct smack_known smack_known_star = {
.smk_known = "*",
.smk_secid = 4,
.smk_cipso = NULL,
};
struct smack_known smack_known_floor = {
.smk_known = "_",
.smk_secid = 5,
.smk_cipso = NULL,
};
struct smack_known smack_known_invalid = {
.smk_known = "",
.smk_secid = 6,
.smk_cipso = NULL,
};
struct smack_known smack_known_web = {
.smk_known = "@",
.smk_secid = 7,
.smk_cipso = NULL,
};
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.
*/
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 == object_label &&
srp->smk_subject == subject_label) {
may = srp->smk_access;
break;
}
}
return may;
}
/**
* smk_access - determine if a subject has a specific access to an object
* @subject_label: a pointer to the subject's Smack label
* @object_label: a pointer to the object's Smack label
* @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(char *subject_label, char *object_label, int request,
struct smk_audit_info *a)
{
struct smack_known *skp;
int may = MAY_NOT;
int rc = 0;
/*
* Hardcoded comparisons.
*
* A star subject can't access any object.
*/
if (subject_label == smack_known_star.smk_known) {
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_label == smack_known_web.smk_known ||
subject_label == smack_known_web.smk_known)
goto out_audit;
/*
* A star object can be accessed by any subject.
*/
if (object_label == smack_known_star.smk_known)
goto out_audit;
/*
* An object can be accessed in any way by a subject
* with the same label.
*/
if (subject_label == object_label)
goto out_audit;
/*
* A hat subject can read any object.
* A floor object can be read by any subject.
*/
if ((request & MAY_ANYREAD) == request) {
if (object_label == smack_known_floor.smk_known)
goto out_audit;
if (subject_label == smack_known_hat.smk_known)
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.
*/
skp = smk_find_entry(subject_label);
rcu_read_lock();
may = smk_access_entry(subject_label, object_label, &skp->smk_rules);
rcu_read_unlock();
if (may > 0 && (request & may) == request)
goto out_audit;
rc = -EACCES;
out_audit:
#ifdef CONFIG_AUDIT
if (a)
smack_log(subject_label, object_label, request, rc, a);
#endif
return rc;
}
/**
* smk_curacc - determine if current has a specific access to an object
* @obj_label: a pointer to the object's Smack label
* @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(char *obj_label, u32 mode, struct smk_audit_info *a)
{
struct task_smack *tsp = current_security();
char *sp = smk_of_task(tsp);
int may;
int rc;
/*
* Check the global rule list
*/
rc = smk_access(sp, obj_label, 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(sp, obj_label, &tsp->smk_rules);
if (may < 0)
goto out_audit;
if ((mode & may) == mode)
goto out_audit;
rc = -EACCES;
}
/*
* Return if a specific label has been designated as the
* only one that gets privilege and current does not
* have that label.
*/
if (smack_onlycap != NULL && smack_onlycap != sp)
goto out_audit;
if (capable(CAP_MAC_OVERRIDE))
rc = 0;
out_audit:
#ifdef CONFIG_AUDIT
if (a)
smack_log(sp, obj_label, mode, rc, a);
#endif
return rc;
}
#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 & MAY_WRITE)
string[i++] = 'w';
if (access & MAY_EXEC)
string[i++] = 'x';
if (access & MAY_APPEND)
string[i++] = 'a';
string[i] = '\0';
}
/**
* smack_log_callback - SMACK specific information
* will be called by generic audit code
* @ab : the audit_buffer
* @a : audit_data
*
*/
static void smack_log_callback(struct audit_buffer *ab, void *a)
{
struct common_audit_data *ad = a;
struct smack_audit_data *sad = &ad->smack_audit_data;
audit_log_format(ab, "lsm=SMACK fn=%s action=%s",
ad->smack_audit_data.function,
sad->result ? "denied" : "granted");
audit_log_format(ab, " subject=");
audit_log_untrustedstring(ab, sad->subject);
audit_log_format(ab, " object=");
audit_log_untrustedstring(ab, sad->object);
audit_log_format(ab, " requested=%s", sad->request);
}
/**
* smack_log - Audit the granting or denial of permissions.
* @subject_label : smack label of the requester
* @object_label : smack label of the object being accessed
* @request: requested permissions
* @result: result from smk_access
* @a: auxiliary audit data
*
* Audit the granting or denial of permissions in accordance
* with the policy.
*/
void smack_log(char *subject_label, char *object_label, int request,
int result, struct smk_audit_info *ad)
{
char
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