/*
 * 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 my 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;

        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;
}