/*
* 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/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 - 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.
*
* Even though Smack labels are usually shared on smack_list
* labels that come in off the network can't be imported
* and added to the list for locking reasons.
*
* Therefore, it is necessary to check the contents of the labels,
* not just the pointer values. Of course, in most cases the labels
* will be on the list, so checking the pointers may be a worthwhile
* optimization.
*/
int smk_access(char *subject_label, char *object_label, int request,
struct smk_audit_info *a)
{
u32 may = MAY_NOT;
struct smack_rule *srp;
int rc = 0;
/*
* Hardcoded comparisons.
*
* A star subject can't access any object.
*/
if (subject_label == smack_known_star.smk_known ||
strcmp(subject_label, smack_known_star.smk_known) == 0) {
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 ||
strcmp(object_label, smack_known_web.smk_known) == 0 ||
strcmp(subject_label, smack_known_web.smk_known) == 0)
goto out_audit;
/*
* A star object can be accessed by any subject.
*/
if (object_label == smack_known_star.smk_known ||
strcmp(object_label, smack_known_star.smk_known) == 0)
goto out_audit;
/*
* An object can be accessed in any way by a subject
* with the same label.
*/
if (subject_label == object_label ||
strcmp(subject_label, object_label) == 0)
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 ||
strcmp(object_label, smack_known_floor.smk_known) == 0)
goto out_audit;
if (subject_label == smack_known_hat.smk_known ||
strcmp(subject_label, smack_known_hat.smk_known) == 0)
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.
*/
rcu_read_lock();
list_for_each_entry_rcu(srp, &smack_rule_list, list) {
if (srp->smk_subject == subject_label ||
strcmp(srp->smk_subject, subject_label) == 0) {
if (srp->smk_object == object_label ||
strcmp(srp->smk_object, object_label) == 0) {
may = srp->smk_access;
break;
}
}
}
rcu_read_unlock();
/*
* This is a bit map operation.
*/
if ((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)
{
int rc;
char *sp = current_security();
rc = smk_access(sp, obj_label, mode, NULL);
if (rc == 0)
goto out_audit;
/*
* 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 != current->cred->security)
goto out_audit;
if (capable(CAP_MAC_OVERRIDE))
return 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 request_buffer[SMK_NUM_ACCESS_TYPE + 1];
struct smack_audit_data *sad;
struct common_audit_data *a = &ad->a;
/* check if we have to log the current event */
if (result != 0 && (log_policy & SMACK_AUDIT_DENIED) == 0)
return;
if (result == 0 && (log_policy & SMACK_AUDIT_ACCEPT) == 0)
return;
if (a->smack_audit_data.function == NULL)
a->smack_audit_data.function = "unknown";
/* end preparing the audit data */
sad = &a->smack_audit_data;
smack_str_from_perm(request_buffer, request);
sad->subject = subject_label;
sad->object = object_label;
sad->request = request_buffer;
sad->result = result;
a->lsm_pre_audit = smack_log_callback;
common_lsm_audit(a);
}
#else /* #ifdef CONFIG_AUDIT */
void smack_log(char *subject_label, char *object_label, int request,
int result, struct smk_audit_info *ad)
{
}
#endif
static DEFINE_MUTEX(smack_known_lock);
/**
* smk_import_entry - import a label, return the list entry
* @string: a text string that might be a Smack label
* @len: the maximum size, or zero if it is NULL terminated.
*
* Returns a pointer to the entry in the label list that
* matches the passed string, adding it if necessary.
*/
struct smack_known *smk_import_entry(const char *string, int len)
{
struct smack_known *skp;
char smack[SMK_LABELLEN];
int found;
int i;
if (len <= 0 || len > SMK_MAXLEN)
len = SMK_MAXLEN;
for (i = 0, found = 0; i < SMK_LABELLEN; i++) {
if (found)
smack[i] = '\0';
else if (i >= len || string[i] > '~' || string[i] <= ' ' ||
string[i] == '/' || string[i] == '"' ||
string[i] == '\\' || string[i] == '\'') {
smack[i] = '\0';
found = 1;
} else
smack[i] = string[i];
}
if (smack[0] == '\0')
return NULL;
mutex_lock(&smack_known_lock);
found = 0;
list_for_each_entry_rcu(skp, &smack_known_list, list) {
if (strncmp(skp->smk_known, smack, SMK_MAXLEN) == 0) {
found = 1;
break;
}
}
if (found == 0) {
skp = kzalloc(sizeof(struct smack_known), GFP_KERNEL);
if (skp != NULL) {
strncpy(skp->smk_known, smack, SMK_MAXLEN);
skp->smk_secid = smack_next_secid++;
skp->smk_cipso = NULL;
spin_lock_init(&skp->smk_cipsolock);
/*
* Make sure that the entry is actually
* filled before putting it on the list.
*/
list_add_rcu(&skp->list, &smack_known_list);
}
}
mutex_unlock(&smack_known_lock);
return skp;
}
/**
* smk_import - import a smack label
* @string: a text string that might be a Smack label
* @len: the maximum size, or zero if it is NULL terminated.
*
* Returns a pointer to the label in the label list that
* matches the passed string, adding it if necessary.
*/
char *smk_import(const char *string, int len)
{
struct smack_known *skp;
/* labels cannot begin with a '-' */
if (string[0] == '-')
return NULL;
skp = smk_import_entry(string, len);
if (skp == NULL)
return NULL;
return skp->smk_known;
}
/**
* smack_from_secid - find the Smack label associated with a secid
* @secid: an integer that might be associated with a Smack label
*
* Returns a pointer to the appropraite Smack label if there is one,
* otherwise a pointer to the invalid Smack label.
*/
char *smack_from_secid(const u32 secid)
{
struct smack_known *skp;
rcu_read_lock();
list_for_each_entry_rcu(skp, &smack_known_list, list) {
if (skp->smk_secid == secid) {
rcu_read_unlock();
return skp->smk_known;
}
}
/*
* If we got this far someone asked for the translation
* of a secid that is not on the list.
*/
rcu_read_unlock();
return smack_known_invalid.smk_known;
}
/**
* smack_to_secid - find the secid associated with a Smack label
* @smack: the Smack label
*
* Returns the appropriate secid if there is one,
* otherwise 0
*/
u32 smack_to_secid(const char *smack)
{
struct smack_known *skp;
rcu_read_lock();
list_for_each_entry_rcu(skp, &smack_known_list, list) {
if (strncmp(skp->smk_known, smack, SMK_MAXLEN) == 0) {
rcu_read_unlock();
return skp->smk_secid;
}
}
rcu_read_unlock();
return 0;
}
/**
* smack_from_cipso - find the Smack label associated with a CIPSO option
* @level: Bell & LaPadula level from the network
* @cp: Bell & LaPadula categories from the network
* @result: where to put the Smack value
*
* This is a simple lookup in the label table.
*
* This is an odd duck as far as smack handling goes in that
* it sends back a copy of the smack label rather than a pointer
* to the master list. This is done because it is possible for
* a foreign host to send a smack label that is new to this
* machine and hence not on the list. That would not be an
* issue except that adding an entry to the master list can't
* be done at that point.
*/
void smack_from_cipso(u32 level, char *cp, char *result)
{
struct smack_known *kp;
char *final = NULL;
rcu_read_lock();
list_for_each_entry(kp, &smack_known_list, list) {
if (kp->smk_cipso == NULL)
continue;
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);
}
rcu_read_unlock();
if (final == NULL)
final = smack_known_huh.smk_known;
strncpy(result, final, SMK_MAXLEN);
return;
}
/**
* 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;
}
