security/smack/smack_access.c - arm/linux - Git at Google

 /*
  * 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_unset = {
 	.smk_next	= NULL,
 	.smk_known	= "UNSET",
 	.smk_secid	= 1,
 	.smk_cipso	= NULL,
 };

 struct smack_known smack_known_huh = {
 	.smk_next	= &smack_known_unset,
 	.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 = &smack_known_invalid;

 /*
  * 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;
 	/*
 	 * 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
  * @object_label: a pointer to the object's Smack label
  * @request: 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->cred->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;
 }
	/*
	* 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_unset = {
	.smk_next = NULL,
	.smk_known = "UNSET",
	.smk_secid = 1,
	.smk_cipso = NULL,
	};

	struct smack_known smack_known_huh = {
	.smk_next = &smack_known_unset,
	.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 = &smack_known_invalid;

	/*
	* 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;
	/*
	* 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
	* @object_label: a pointer to the object's Smack label
	* @request: 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->cred->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;
	}