/*
   * 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;
  }