/* 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"
#include "services.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)
{
        u32 i;
        int s[COND_EXPR_MAXDEPTH];
        int sp = -1;

        if (expr->len == 0)
                return -1;

        for (i = 0; i < expr->len; i++) {
                struct cond_expr_node *node = &expr->nodes[i];

                switch (node->expr_type) {
                case COND_BOOL:
                        if (sp == (COND_EXPR_MAXDEPTH - 1))
                                return -1;
                        sp++;
                        s[sp] = p->bool_val_to_struct[node->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.
 */
static void evaluate_cond_node(struct policydb *p, struct cond_node *node)
{
        struct avtab_node *avnode;
        int new_state;
        u32 i;

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

                for (i = 0; i < node->false_list.len; i++) {
                        avnode = node->false_list.nodes[i];
                        /* -1 or 1 */
                        if (new_state)
                                avnode->key.specified &= ~AVTAB_ENABLED;
                        else
                                avnode->key.specified |= AVTAB_ENABLED;
                }
        }
}

void evaluate_cond_nodes(struct policydb *p)
{
        u32 i;

        for (i = 0; i < p->cond_list_len; i++)
                evaluate_cond_node(p, &p->cond_list[i]);
}

void cond_policydb_init(struct policydb *p)
{
        p->bool_val_to_struct = NULL;
        p->cond_list = NULL;
        p->cond_list_len = 0;

        avtab_init(&p->te_cond_avtab);
}

static void cond_node_destroy(struct cond_node *node)
{
        kfree(node->expr.nodes);
        /* the avtab_ptr_t nodes are destroyed by the avtab */
        kfree(node->true_list.nodes);
        kfree(node->false_list.nodes);
}

static void cond_list_destroy(struct policydb *p)
{
        u32 i;

        for (i = 0; i < p->cond_list_len; i++)
                cond_node_destroy(&p->cond_list[i]);
        kfree(p->cond_list);
}

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

int cond_init_bool_indexes(struct policydb *p)
{
        kfree(p->bool_val_to_struct);
        p->bool_val_to_struct = kmalloc_array(p->p_bools.nprim,
                                              sizeof(*p->bool_val_to_struct),
                                              GFP_KERNEL);
        if (!p->bool_val_to_struct)
                return -ENOMEM;
        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->sym_val_to_name[SYM_BOOLS][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 symtab *s, void *fp)
{
        char *key = NULL;
        struct cond_bool_datum *booldatum;
        __le32 buf[3];
        u32 len;
        int rc;

        booldatum = kzalloc(sizeof(*booldatum), GFP_KERNEL);
        if (!booldatum)
                return -ENOMEM;

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

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

        rc = -EINVAL;
        if (!bool_isvalid(booldatum))
                goto err;

        len = le32_to_cpu(buf[2]);
        if (((len == 0) || (len == (u32)-1)))
                goto err;

        rc = -ENOMEM;
        key = kmalloc(len + 1, GFP_KERNEL);
        if (!key)
                goto err;
        rc = next_entry(key, fp, len);
        if (rc)
                goto err;
        key[len] = '\0';
        rc = symtab_insert(s, key, booldatum);
        if (rc)
                goto err;

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

struct cond_insertf_data {
        struct policydb *p;
        struct avtab_node **dst;
        struct cond_av_list *other;
};

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;
        struct avtab_node *node_ptr;
        u32 i;
        bool 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)) {
                        pr_err("SELinux: type rule already exists outside of a conditional.\n");
                        return -EINVAL;
                }
                /*
                 * 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)) {
                                        pr_err("SELinux: too many conflicting type rules.\n");
                                        return -EINVAL;
                                }
                                found = false;
                                for (i = 0; i < other->len; i++) {
                                        if (other->nodes[i] == node_ptr) {
                                                found = true;
                                                break;
                                        }
                                }
                                if (!found) {
                                        pr_err("SELinux: conflicting type rules.\n");
                                        return -EINVAL;
                                }
                        }
                } else {
                        if (avtab_search(&p->te_cond_avtab, k)) {
                                pr_err("SELinux: conflicting type rules when adding type rule for true.\n");
                                return -EINVAL;
                        }
                }
        }

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

        *data->dst = node_ptr;
        return 0;
}

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

        rc = next_entry(buf, fp, sizeof(u32));
        if (rc)
                return rc;

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

        list->nodes = kcalloc(len, sizeof(*list->nodes), GFP_KERNEL);
        if (!list->nodes)
                return -ENOMEM;

        data.p = p;
        data.other = other;
        for (i = 0; i < len; i++) {
                data.dst = &list->nodes[i];
                rc = avtab_read_item(&p->te_cond_avtab, fp, p, cond_insertf,
                                     &data);
                if (rc) {
                        kfree(list->nodes);
                        list->nodes = NULL;
                        return rc;
                }
        }

        list->len = len;
        return 0;
}

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

        if (expr->bool > p->p_bools.nprim) {
                pr_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 i, len;
        int rc;

        rc = next_entry(buf, fp, sizeof(u32) * 2);
        if (rc)
                return rc;

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

        /* expr */
        len = le32_to_cpu(buf[1]);
        node->expr.nodes = kcalloc(len, sizeof(*node->expr.nodes), GFP_KERNEL);
        if (!node->expr.nodes)
                return -ENOMEM;

        node->expr.len = len;

        for (i = 0; i < len; i++) {
                struct cond_expr_node *expr = &node->expr.nodes[i];

                rc = next_entry(buf, fp, sizeof(u32) * 2);
                if (rc)
                        return rc;

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

                if (!expr_node_isvalid(p, expr))
                        return -EINVAL;
        }

        rc = cond_read_av_list(p, fp, &node->true_list, NULL);
        if (rc)
                return rc;
        return cond_read_av_list(p, fp, &node->false_list, &node->true_list);
}

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

        rc = next_entry(buf, fp, sizeof(buf));
        if (rc)
                return rc;

        len = le32_to_cpu(buf[0]);

        p->cond_list = kcalloc(len, sizeof(*p->cond_list), GFP_KERNEL);
        if (!p->cond_list)
                return -ENOMEM;

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

        p->cond_list_len = len;

        for (i = 0; i < len; i++) {
                rc = cond_read_node(p, &p->cond_list[i], fp);
                if (rc)
                        goto err;
        }
        return 0;
err:
        cond_list_destroy(p);
        p->cond_list = NULL;
        return rc;
}

int cond_write_bool(void *vkey, void *datum, void *ptr)
{
        char *key = vkey;
        struct cond_bool_datum *booldatum = datum;
        struct policy_data *pd = ptr;
        void *fp = pd->fp;
        __le32 buf[3];
        u32 len;
        int rc;

        len = strlen(key);
        buf[0] = cpu_to_le32(booldatum->value);
        buf[1] = cpu_to_le32(booldatum->state);
        buf[2] = cpu_to_le32(len);
        rc = put_entry(buf, sizeof(u32), 3, fp);
        if (rc)
                return rc;
        rc = put_entry(key, 1, len, fp);
        if (rc)
                return rc;
        return 0;
}

/*
 * cond_write_cond_av_list doesn't write out the av_list nodes.
 * Instead it writes out the key/value pairs from the avtab. This
 * is necessary because there is no way to uniquely identifying rules
 * in the avtab so it is not possible to associate individual rules
 * in the avtab with a conditional without saving them as part of
 * the conditional. This means that the avtab with the conditional
 * rules will not be saved but will be rebuilt on policy load.
 */
static int cond_write_av_list(struct policydb *p,
                              struct cond_av_list *list, struct policy_file *fp)
{
        __le32 buf[1];
        u32 i;
        int rc;

        buf[0] = cpu_to_le32(list->len);
        rc = put_entry(buf, sizeof(u32), 1, fp);
        if (rc)
                return rc;

        for (i = 0; i < list->len; i++) {
                rc = avtab_write_item(p, list->nodes[i], fp);
                if (rc)
                        return rc;
        }

        return 0;
}

static int cond_write_node(struct policydb *p, struct cond_node *node,
                    struct policy_file *fp)
{
        __le32 buf[2];
        int rc;
        u32 i;

        buf[0] = cpu_to_le32(node->cur_state);
        rc = put_entry(buf, sizeof(u32), 1, fp);
        if (rc)
                return rc;

        buf[0] = cpu_to_le32(node->expr.len);
        rc = put_entry(buf, sizeof(u32), 1, fp);
        if (rc)
                return rc;

        for (i = 0; i < node->expr.len; i++) {
                buf[0] = cpu_to_le32(node->expr.nodes[i].expr_type);
                buf[1] = cpu_to_le32(node->expr.nodes[i].bool);
                rc = put_entry(buf, sizeof(u32), 2, fp);
                if (rc)
                        return rc;
        }

        rc = cond_write_av_list(p, &node->true_list, fp);
        if (rc)
                return rc;
        rc = cond_write_av_list(p, &node->false_list, fp);
        if (rc)
                return rc;

        return 0;
}

int cond_write_list(struct policydb *p, void *fp)
{
        u32 i;
        __le32 buf[1];
        int rc;

        buf[0] = cpu_to_le32(p->cond_list_len);
        rc = put_entry(buf, sizeof(u32), 1, fp);
        if (rc)
                return rc;

        for (i = 0; i < p->cond_list_len; i++) {
                rc = cond_write_node(p, &p->cond_list[i], fp);
                if (rc)
                        return rc;
        }

        return 0;
}

void cond_compute_xperms(struct avtab *ctab, struct avtab_key *key,
                struct extended_perms_decision *xpermd)
{
        struct avtab_node *node;

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

        for (node = avtab_search_node(ctab, key); node;
                        node = avtab_search_node_next(node, key->specified)) {
                if (node->key.specified & AVTAB_ENABLED)
                        services_compute_xperms_decision(xpermd, node);
        }
        return;

}
/* 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 extended_perms *xperms)
{
        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.u.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.u.data;
                if ((u16)(AVTAB_AUDITALLOW|AVTAB_ENABLED) ==
                    (node->key.specified & (AVTAB_AUDITALLOW|AVTAB_ENABLED)))
                        avd->auditallow |= node->datum.u.data;
                if (xperms && (node->key.specified & AVTAB_ENABLED) &&
                                (node->key.specified & AVTAB_XPERMS))
                        services_compute_xperms_drivers(xperms, node);
        }
}