/*
* 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_next = NULL,
.smk_known = "?",
.smk_secid = 2,
.smk_cipso = NULL,
};
struct smack_known smack_known_hat = {
.smk_next = &smack_known_huh,
.smk_known = "^",
.smk_secid = 3,
.smk_cipso = NULL,
};
struct smack_known smack_known_star = {
.smk_next = &smack_known_hat,
.smk_known = "*",
.smk_secid = 4,
.smk_cipso = NULL,
};
struct smack_known smack_known_floor = {
.smk_next = &smack_known_star,
.smk_known = "_",
.smk_secid = 5,
.smk_cipso = NULL,
};
struct smack_known smack_known_invalid = {
.smk_next = &smack_known_floor,
.smk_known = "",
.smk_secid = 6,
.smk_cipso = NULL,
};
struct smack_known smack_known_web = {
.smk_next = &smack_known_invalid,
.smk_known = "@",
.smk_secid = 7,
.smk_cipso = NULL,
};
struct smack_known *smack_known = &smack_known_web;
/*
* The initial value needs to be bigger than any of the
* known values above.
*/
static u32 smack_next_secid = 10;
/**
* 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
*
* 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)
{
u32 may = MAY_NOT;
struct smk_list_entry *sp;
struct smack_rule *srp;
/*
* 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)
return -EACCES;
/*
* 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)
return 0;
/*
* 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)
return 0;
/*
* 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)
return 0;
/*
* 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)
return 0;
if (subject_label == smack_known_hat.smk_known ||
strcmp(subject_label, smack_known_hat.smk_known) == 0)
return 0;
}
/*
* 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.
*/
for (sp = smack_list; sp != NULL; sp = sp->smk_next) {
srp = &sp->smk_rule;
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;
}
}
}
/*
* This is a bit map operation.
*/
if ((request & may) == request)
return 0;
return -EACCES;
}
/**
* 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
*
* 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)
{
int rc;
rc = smk_access(current_security(), obj_label, mode);
if (rc == 0)
return 0;
/*
* 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)
return rc;
if (capable(CAP_MAC_OVERRIDE))
return 0;
return rc;
}
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] == '/') {
smack[i] = '\0';
found = 1;
} else
smack[i] = string[i];
}
if (smack[0] == '\0')
return NULL;
mutex_lock(&smack_known_lock);
for (skp = smack_known; skp != NULL; skp = skp->smk_next)
if (strncmp(skp->smk_known, smack, SMK_MAXLEN) == 0)
break;
if (skp == NULL) {
skp = kzalloc(sizeof(struct smack_known), GFP_KERNEL);
if (skp != NULL) {
skp->smk_next = smack_known;
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.
*/
smp_mb();
smack_known = skp;
}
}
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;
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;
for (skp = smack_known; skp != NULL; skp = skp->smk_next)
if (skp->smk_secid == secid)
return skp->smk_known;
/*
* If we got this far someone asked for the translation
* of a secid that is not on the list.
*/
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;
for (skp = smack_known; skp != NULL; skp = skp->smk_next)
if (strncmp(skp->smk_known, smack, SMK_MAXLEN) == 0)
return skp->smk_secid;
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;
for (kp = smack_known; final == NULL && kp != NULL; kp = kp->smk_next) {
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);
}
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;
for (kp = smack_known; kp != NULL; kp = kp->smk_next)
if (kp->smk_known == smack ||
strcmp(kp->smk_known, smack) == 0)
break;
if (kp == NULL || kp->smk_cipso == NULL)
return -ENOENT;
memcpy(cp, kp->smk_cipso, sizeof(struct smack_cipso));
return 0;
}
