- 根目录:
- security
- smack
- smack_access.c
/*
* 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_invalid = {
.smk_known = "",
.smk_secid = 6,
};
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 == 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_known: a pointer to the subject's Smack label entry
* @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(struct smack_known *subject_known, char *object_label,
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_known == &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_label == smack_known_web.smk_known ||
subject_known == &smack_known_web)
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_known->smk_known == 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_known == &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_known->smk_known, object_label,
&subject_known->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_known->smk_known, 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();
struct smack_known *skp = smk_of_task(tsp);
int may;
int rc;
/*
* Check the global rule list
*/
rc = smk_access(skp, 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(skp->smk_known, obj_label,
&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(skp->smk_known, 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';
if (access & MAY_TRANSMUTE)
string[i++] = 't';
if (access & MAY_LOCK)
string[i++] = 'l';
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;
sad = a->smack_audit_data;
if (sad->function == NULL)
sad->function = "unknown";
/* end preparing the audit data */
smack_str_from_perm(request_buffer, request);
sad->subject = subject_label;
sad->object = object_label;
sad->request = request_buffer;
sad->result = result;
common_lsm_audit(a, smack_log_callback, NULL);
}
#else /* #ifdef CONFIG_AUDIT */
void smack_log(char *subject_label, char *object_label, int request,
int result, struct smk_audit_info *ad)
{
}
#endif
DEFINE_MUTEX(smack_known_lock);
struct hlist_head smack_known_hash[SMACK_HASH_SLOTS];
/**
* smk_insert_entry - insert a smack label into a hash map,
*
* this function must be called under smack_known_lock
*/
void smk_insert_entry(struct smack_known *skp)
{
unsigned int hash;
struct hlist_head *head;
hash = full_name_hash(skp->smk_known, strlen(skp->smk_known));
head = &smack_known_hash[hash & (SMACK_HASH_SLOTS - 1)];
hlist_add_head_rcu(&skp->smk_hashed, head);
list_add_rcu(&skp->list, &smack_known_list);
}
/**
* smk_find_entry - find a label on the list, return the list entry
* @string: a text string that might be a Smack label
*
* Returns a pointer to the entry in the label list that
* matches the passed string.
*/
struct smack_known *smk_find_entry(const char *string)
{
unsigned int hash;
struct hlist_head *head;
struct smack_known *skp;
hash = full_name_hash(string, strlen(string));
head = &smack_known_hash[hash & (SMACK_HASH_SLOTS - 1)];
hlist_for_each_entry_rcu(skp, head, smk_hashed)
if (strcmp(skp->smk_known, string) == 0)
return skp;
return NULL;
}
/**
* smk_parse_smack - parse smack label from a text string
* @string: a text string that might contain a Smack label
* @len: the maximum size, or zero if it is NULL terminated.
*
* Returns a pointer to the clean label, or NULL
*/
char *smk_parse_smack(const char *string, int len)
{
char *smack;
int i;
if (len <= 0)
len = strlen(string) + 1;
/*
* Reserve a leading '-' as an indicator that
* this isn't a label, but an option to interfaces
* including /smack/cipso and /smack/cipso2
*/
if (string[0] == '-')
return NULL;
for (i = 0; i < len; i++)
if (string[i] > '~' || string[i] <= ' ' || string[i] == '/' ||
string[i] == '"' || string[i] == '\\' || string[i] == '\'')
break;
if (i == 0 || i >= SMK_LONGLABEL)
return NULL;
smack = kzalloc(i + 1, GFP_KERNEL);
if (smack != NULL) {
strncpy(smack, string, i + 1);
smack[i] = '\0';
}
return smack;
}
/**
* smk_netlbl_mls - convert a catset to netlabel mls categories
* @catset: the Smack categories
* @sap: where to put the netlabel categories
*
* Allocates and fills attr.mls
* Returns 0 on success, error code on failure.
*/
int smk_netlbl_mls(int level, char *catset, struct netlbl_lsm_secattr *sap,
int len)
{
unsigned char *cp;
unsigned char m;
int cat;
int rc;
int byte;
sap->flags |= NETLBL_SECATTR_MLS_CAT;
sap->attr.mls.lvl = level;
sap->attr.mls.cat = netlbl_secattr_catmap_alloc(GFP_ATOMIC);
if (!sap->attr.mls.cat)
return -ENOMEM;
sap->attr.mls.cat->startbit = 0;
for (cat = 1, cp = catset, byte = 0; byte < len; cp++, byte++)
for (m = 0x80; m != 0; m >>= 1, cat++) {
if ((m & *cp) == 0)
continue;
rc = netlbl_secattr_catmap_setbit(sap->attr.mls.cat,
cat, GFP_ATOMIC);
if (rc < 0) {
netlbl_secattr_catmap_free(sap->attr.mls.cat);
return rc;
}
}
return 0;
}
/**
* 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;
int slen;
int rc;
smack = smk_parse_smack(string, len);
if (smack == NULL)
return NULL;
mutex_lock(&smack_known_lock);
skp = smk_find_entry(smack);
if (skp != NULL)
goto freeout;
skp = kzalloc(sizeof(*skp), GFP_KERNEL);
if (skp == NULL)
goto freeout;
skp->smk_known = smack;
skp->smk_secid = smack_next_secid++;
skp->smk_netlabel.domain = skp->smk_known;
skp->smk_netlabel.flags =
NETLBL_SECATTR_DOMAIN | NETLBL_SECATTR_MLS_LVL;
/*
* If direct labeling works use it.
* Otherwise use mapped labeling.
*/
slen = strlen(smack);
if (slen < SMK_CIPSOLEN)
rc = smk_netlbl_mls(smack_cipso_direct, skp->smk_known,
&skp->smk_netlabel, slen);
else
rc = smk_netlbl_mls(smack_cipso_mapped, (char *)&skp->smk_secid,
&skp->smk_netlabel, sizeof(skp->smk_secid));
if (rc >= 0) {
INIT_LIST_HEAD(&skp->smk_rules);
mutex_init(&skp->smk_rules_lock);
/*
* Make sure that the entry is actually
* filled before putting it on the list.
*/
smk_insert_entry(skp);
goto unlockout;
}
/*
* smk_netlbl_mls failed.
*/
kfree(skp);
skp = NULL;
freeout:
kfree(smack);
unlockout:
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 appropriate Smack label entry if there is one,
* otherwise a pointer to the invalid Smack label.
*/
struct smack_known *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;
}
}
/*
* 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;
}
/**
* 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 = smk_find_entry(smack);
if (skp == NULL)
return 0;
return skp->smk_secid;
}