/* Authors: Karl MacMillan <kmacmillan@tresys.com>
 *          Frank Mayer <mayerf@tresys.com>
 *
 * Copyright (C) 2003 - 2004 Tresys Technology, LLC
 *      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.
 */

#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/spinlock.h>
#include <linux/slab.h>

#include "security.h"
#include "conditional.h"

/*
 * cond_evaluate_expr evaluates a conditional expr
 * in reverse polish notation. It returns true (1), false (0),
 * or undefined (-1). Undefined occurs when the expression
 * exceeds the stack depth of COND_EXPR_MAXDEPTH.
 */
static int cond_evaluate_expr(struct policydb *p, struct cond_expr *expr)
{

        struct cond_expr *cur;
        int s[COND_EXPR_MAXDEPTH];
        int sp = -1;

        for (cur = expr; cur; cur = cur->next) {
                switch (cur->expr_type) {
                case COND_BOOL:
                        if (sp == (COND_EXPR_MAXDEPTH - 1))
                                return -1;
                        sp++;
                        s[sp] = p->bool_val_to_struct[cur->bool - 1]->state;
                        break;
                case COND_NOT:
                        if (sp < 0)
                                return -1;
                        s[sp] = !s[sp];
                        break;
                case COND_OR:
                        if (sp < 1)
                                return -1;
                        sp--;
                        s[sp] |= s[sp + 1];
                        break;
                case COND_AND:
                        if (sp < 1)
                                return -1;
                        sp--;
                        s[sp] &= s[sp + 1];
                        break;
                case COND_XOR:
                        if (sp < 1)
                                return -1;
                        sp--;
                        s[sp] ^= s[sp + 1];
                        break;
                case COND_EQ:
                        if (sp < 1)
                                return -1;
                        sp--;
                        s[sp] = (s[sp] == s[sp + 1]);
                        break;
                case COND_NEQ:
                        if (sp < 1)
                                return -1;
                        sp--;
                        s[sp] = (s[sp] != s[sp + 1]);
                        break;
                default:
                        return -1;
                }
        }
        return s[0];
}

/*
 * evaluate_cond_node evaluates the conditional stored in
 * a struct cond_node and if the result is different than the
 * current state of the node it sets the rules in the true/false
 * list appropriately. If the result of the expression is undefined
 * all of the rules are disabled for safety.
 */
int evaluate_cond_node(struct policydb *p, struct cond_node *node)
{
        int new_state;
        struct cond_av_list *cur;

        new_state = cond_evaluate_expr(p, node->expr);
        if (new_state != node->cur_state) {
                node->cur_state = new_state;
                if (new_state == -1)
                        printk(KERN_ERR "SELinux: expression result was undefined - disabling all rules.\n");
                /* turn the rules on or off */
                for (cur = node->true_list; cur; cur = cur->next) {
                        if (new_state <= 0)
                                cur->node->key.specified &= ~AVTAB_ENABLED;
                        else
                                cur->node->key.specified |= AVTAB_ENABLED;
                }

                for (cur = node->false_list; cur; cur = cur->next) {
                        /* -1 or 1 */
                        if (new_state)
                                cur->node->key.specified &= ~AVTAB_ENABLED;
                        else
                                cur->node->key.specified |= AVTAB_ENABLED;
                }
        }
        return 0;
}

int cond_policydb_init(struct policydb *p)
{
        p->bool_val_to_struct = NULL;
        p->cond_list = NULL;
        if (avtab_init(&p->te_cond_avtab))
                return -1;

        return 0;
}

static void cond_av_list_destroy(struct cond_av_list *list)
{
        struct cond_av_list *cur, *next;
        for (cur = list; cur; cur = next) {
                next = cur->next;
                /* the avtab_ptr_t node is destroy by the avtab */
                kfree(cur);
        }
}

static void cond_node_destroy(struct cond_node *node)
{
        struct cond_expr *cur_expr, *next_expr;

        for (cur_expr = node->expr; cur_expr; cur_expr = next_expr) {
                next_expr = cur_expr->next;
                kfree(cur_expr);
        }
        cond_av_list_destroy(node->true_list);
        cond_av_list_destroy(node->false_list);
        kfree(node);
}

static void cond_list_destroy(struct cond_node *list)
{
        struct cond_node *next, *cur;

        if (list == NULL)
                return;

        for (cur = list; cur; cur = next) {
                next = cur->next;
                cond_node_destroy(cur);
        }
}

void cond_policydb_destroy(struct policydb *p)
{
        kfree(p->bool_val_to_struct);
        avtab_destroy(&p->te_cond_avtab);
        cond_list_destroy(p->cond_list);
}

int cond_init_bool_indexes(struct policydb *p)
{
        kfree(p->bool_val_to_struct);
        p->bool_val_to_struct = (struct cond_bool_datum **)
                kmalloc(p->p_bools.nprim * sizeof(struct cond_bool_datum *), GFP_KERNEL);
        if (!p->bool_val_to_struct)
                return -1;
        return 0;
}

int cond_destroy_bool(void *key, void *datum, void *p)
{
        kfree(key);
        kfree(datum);
        return 0;
}

int cond_index_bool(void *key, void *datum, void *datap)
{
        struct policydb *p;
        struct cond_bool_datum *booldatum;

        booldatum = datum;
        p = datap;

        if (!booldatum->value || booldatum->value > p->p_bools.nprim)
                return -EINVAL;

        p->p_bool_val_to_name[booldatum->value - 1] = key;
        p->bool_val_to_struct[booldatum->value - 1] = booldatum;

        return 0;
}

static int bool_isvalid(struct cond_bool_datum *b)
{
        if (!(b->state == 0 || b->state == 1))
                return 0;
        return 1;
}

int cond_read_bool(struct policydb *p, struct hashtab *h, void *fp)
{
        char *key = NULL;
        struct cond_bool_datum *booldatum;
        __le32 buf[3];
        u32 len;
        int rc;

        booldatum = kzalloc(sizeof(struct cond_bool_datum), GFP_KERNEL);
        if (!booldatum)
                return -1;

        rc = next_entry(buf, fp, sizeof buf);
        if (rc < 0)
                goto err;

        booldatum->value = le32_to_cpu(buf[0]);
        booldatum->state = le32_to_cpu(buf[1]);

        if (!bool_isvalid(booldatum))
                goto err;

        len = le32_to_cpu(buf[2]);

        key = kmalloc(len + 1, GFP_KERNEL);
        if (!key)
                goto err;
        rc = next_entry(key, fp, len);
        if (rc < 0)
                goto err;
        key[len] = '\0';
        if (hashtab_insert(h, key, booldatum))
                goto err;

        return 0;
err:
        cond_destroy_bool(key, booldatum, NULL);
        return -1;
}

struct cond_insertf_data {
        struct policydb *p;
        struct cond_av_list *other;
        struct cond_av_list *head;
        struct cond_av_list *tail;
};

static int cond_insertf(struct avtab *a, struct avtab_key *k, struct avtab_datum *d, void *ptr)
{
        struct cond_insertf_data *data = ptr;
        struct policydb *p = data->p;
        struct cond_av_list *other = data->other, *list, *cur;
        struct avtab_node *node_ptr;
        u8 found;


        /*
         * For type rules we have to make certain there aren't any
         * conflicting rules by searching the te_avtab and the
         * cond_te_avtab.
         */
        if (k->specified & AVTAB_TYPE) {
                if (avtab_search(&p->te_avtab, k)) {
                        printk(KERN_ERR "SELinux: type rule already exists outside of a conditional.\n");
                        goto err;
                }
                /*
                 * If we are reading the false list other will be a pointer to
                 * the true list. We can have duplicate entries if there is only
                 * 1 other entry and it is in our true list.
                 *
                 * If we are reading the true list (other == NULL) there shouldn't
                 * be any other entries.
                 */
                if (other) {
                        node_ptr = avtab_search_node(&p->te_cond_avtab, k);
                        if (node_ptr) {
                                if (avtab_search_node_next(node_ptr, k->specified)) {
                                        printk(KERN_ERR "SELinux: too many conflicting type rules.\n");
                                        goto err;
                                }
                                found = 0;
                                for (cur = other; cur; cur = cur->next) {
                                        if (cur->node == node_ptr) {
                                                found = 1;
                                                break;
                                        }
                                }
                                if (!found) {
                                        printk(KERN_ERR "SELinux: conflicting type rules.\n");
                                        goto err;
                                }
                        }
                } else {
                        if (avtab_search(&p->te_cond_avtab, k)) {
                                printk(KERN_ERR "SELinux: conflicting type rules when adding type rule for true.\n");
                                goto err;
                        }
                }
        }

        node_ptr = avtab_insert_nonunique(&p->te_cond_avtab, k, d);
        if (!node_ptr) {
                printk(KERN_ERR "SELinux: could not insert rule.\n");
                goto err;
        }

        list = kzalloc(sizeof(struct cond_av_list), GFP_KERNEL);
        if (!list)
                goto err;

        list->node = node_ptr;
        if (!data->head)
                data->head = list;
        else
                data->tail->next = list;
        data->tail = list;
        return 0;

err:
        cond_av_list_destroy(data->head);
        data->head = NULL;
        return -1;
}

static int cond_read_av_list(struct policydb *p, void *fp, struct cond_av_list **ret_list, struct cond_av_list *other)
{
        int i, rc;
        __le32 buf[1];
        u32 len;
        struct cond_insertf_data data;

        *ret_list = NULL;

        len = 0;
        rc = next_entry(buf, fp, sizeof(u32));
        if (rc < 0)
                return -1;

        len = le32_to_cpu(buf[0]);
        if (len == 0)
                return 0;

        data.p = p;
        data.other = other;
        data.head = NULL;
        data.tail = NULL;
        for (i = 0; i < len; i++) {
                rc = avtab_read_item(&p->te_cond_avtab, fp, p, cond_insertf,
                                     &data);
                if (rc)
                        return rc;

        }

        *ret_list = data.head;
        return 0;
}

static int expr_isvalid(struct policydb *p, struct cond_expr *expr)
{
        if (expr->expr_type <= 0 || expr->expr_type > COND_LAST) {
                printk(KERN_ERR "SELinux: conditional expressions uses unknown operator.\n");
                return 0;
        }

        if (expr->bool > p->p_bools.nprim) {
                printk(KERN_ERR "SELinux: conditional expressions uses unknown bool.\n");
                return 0;
        }
        return 1;
}

static int cond_read_node(struct policydb *p, struct cond_node *node, void *fp)
{
        __le32 buf[2];
        u32 len, i;
        int rc;
        struct cond_expr *expr = NULL, *last = NULL;

        rc = next_entry(buf, fp, sizeof(u32));
        if (rc < 0)
                return -1;

        node->cur_state = le32_to_cpu(buf[0]);

        len = 0;
        rc = next_entry(buf, fp, sizeof(u32));
        if (rc < 0)
                return -1;

        /* expr */
        len = le32_to_cpu(buf[0]);

        for (i = 0; i < len; i++) {
                rc = next_entry(buf, fp, sizeof(u32) * 2);
                if (rc < 0)
                        goto err;

                expr = kzalloc(sizeof(struct cond_expr), GFP_KERNEL);
                if (!expr)
                        goto err;

                expr->expr_type = le32_to_cpu(buf[0]);
                expr->bool = le32_to_cpu(buf[1]);

                if (!expr_isvalid(p, expr)) {
                        kfree(expr);
                        goto err;
                }

                if (i == 0)
                        node->expr = expr;
                else
                        last->next = expr;
                last = expr;
        }

        if (cond_read_av_list(p, fp, &node->true_list, NULL) != 0)
                goto err;
        if (cond_read_av_list(p, fp, &node->false_list, node->true_list) != 0)
                goto err;
        return 0;
err:
        cond_node_destroy(node);
        return -1;
}

int cond_read_list(struct policydb *p, void *fp)
{
        struct cond_node *node, *last = NULL;
        __le32 buf[1];
        u32 i, len;
        int rc;

        rc = next_entry(buf, fp, sizeof buf);
        if (rc < 0)
                return -1;

        len = le32_to_cpu(buf[0]);

        rc = avtab_alloc(&(p->te_cond_avtab), p->te_avtab.nel);
        if (rc)
                goto err;

        for (i = 0; i < len; i++) {
                node = kzalloc(sizeof(struct cond_node), GFP_KERNEL);
                if (!node)
                        goto err;

                if (cond_read_node(p, node, fp) != 0)
                        goto err;

                if (i == 0)
                        p->cond_list = node;
                else
                        last->next = node;
                last = node;
        }
        return 0;
err:
        cond_list_destroy(p->cond_list);
        p->cond_list = NULL;
        return -1;
}

/* Determine whether additional permissions are granted by the conditional
 * av table, and if so, add them to the result
 */
void cond_compute_av(struct avtab *ctab, struct avtab_key *key, struct av_decision *avd)
{
        struct avtab_node *node;

        if (!ctab || !key || !avd)
                return;

        for (node = avtab_search_node(ctab, key); node;
                                node = avtab_search_node_next(node, key->specified)) {
                if ((u16)(AVTAB_ALLOWED|AVTAB_ENABLED) ==
                    (node->key.specified & (AVTAB_ALLOWED|AVTAB_ENABLED)))
                        avd->allowed |= node->datum.data;
                if ((u16)(AVTAB_AUDITDENY|AVTAB_ENABLED) ==
                    (node->key.specified & (AVTAB_AUDITDENY|AVTAB_ENABLED)))
                        /* Since a '0' in an auditdeny mask represents a
                         * permission we do NOT want to audit (dontaudit), we use
                         * the '&' operand to ensure that all '0's in the mask
                         * are retained (much unlike the allow and auditallow cases).
                         */
                        avd->auditdeny &= node->datum.data;
                if ((u16)(AVTAB_AUDITALLOW|AVTAB_ENABLED) ==
                    (node->key.specified & (AVTAB_AUDITALLOW|AVTAB_ENABLED)))
                        avd->auditallow |= node->datum.data;
        }
        return;
}