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[thirdparty/openssl.git] / crypto / x509v3 / pcy_tree.c

/* pcy_tree.c */
/* Written by Dr Stephen N Henson (steve@openssl.org) for the OpenSSL
 * project 2004.
 */
/* ====================================================================
 * Copyright (c) 2004 The OpenSSL Project.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer. 
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. All advertising materials mentioning features or use of this
 *    software must display the following acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
 *
 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For written permission, please contact
 *    licensing@OpenSSL.org.
 *
 * 5. Products derived from this software may not be called "OpenSSL"
 *    nor may "OpenSSL" appear in their names without prior written
 *    permission of the OpenSSL Project.
 *
 * 6. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
 *
 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 * ====================================================================
 *
 * This product includes cryptographic software written by Eric Young
 * (eay@cryptsoft.com).  This product includes software written by Tim
 * Hudson (tjh@cryptsoft.com).
 *
 */

#include "cryptlib.h"
#include <openssl/x509.h>
#include <openssl/x509v3.h>

#include "pcy_int.h"

/* Enable this to print out the complete policy tree at various point during
 * evaluation.
 */

/*#define OPENSSL_POLICY_DEBUG*/

#ifdef OPENSSL_POLICY_DEBUG

static void expected_print(BIO *err, X509_POLICY_LEVEL *lev,
                                X509_POLICY_NODE *node, int indent)
        {
        if (        (lev->flags & X509_V_FLAG_INHIBIT_MAP)
                || !(node->data->flags & POLICY_DATA_FLAG_MAP_MASK))
                BIO_puts(err, "  Not Mapped\n");
        else
                {
                int i;
                STACK_OF(ASN1_OBJECT) *pset = node->data->expected_policy_set;
                ASN1_OBJECT *oid;
                BIO_puts(err, "  Expected: ");
                for (i = 0; i < sk_ASN1_OBJECT_num(pset); i++)
                        {
                        oid = sk_ASN1_OBJECT_value(pset, i);
                        if (i)
                                BIO_puts(err, ", ");
                        i2a_ASN1_OBJECT(err, oid);
                        }
                BIO_puts(err, "\n");
                }
        }

static void tree_print(char *str, X509_POLICY_TREE *tree,
                        X509_POLICY_LEVEL *curr)
        {
        X509_POLICY_LEVEL *plev;
        X509_POLICY_NODE *node;
        int i;
        BIO *err;
        err = BIO_new_fp(stderr, BIO_NOCLOSE);
        if (!curr)
                curr = tree->levels + tree->nlevel;
        else
                curr++;
        BIO_printf(err, "Level print after %s\n", str);
        BIO_printf(err, "Printing Up to Level %ld\n", curr - tree->levels);
        for (plev = tree->levels; plev != curr; plev++)
                {
                BIO_printf(err, "Level %ld, flags = %x\n",
                                plev - tree->levels, plev->flags);
                for (i = 0; i < sk_X509_POLICY_NODE_num(plev->nodes); i++)
                        {
                        node = sk_X509_POLICY_NODE_value(plev->nodes, i);
                        X509_POLICY_NODE_print(err, node, 2);
                        expected_print(err, plev, node, 2);
                        BIO_printf(err, "  Flags: %x\n", node->data->flags);
                        }
                if (plev->anyPolicy)
                        X509_POLICY_NODE_print(err, plev->anyPolicy, 2);
                }

        BIO_free(err);

        }
#else

#define tree_print(a,b,c) /* */

#endif

/*-
 * Initialize policy tree. Return values:
 *  0 Some internal error occurred.
 * -1 Inconsistent or invalid extensions in certificates.
 *  1 Tree initialized OK.
 *  2 Policy tree is empty.
 *  5 Tree OK and requireExplicitPolicy true.
 *  6 Tree empty and requireExplicitPolicy true.
 */

static int tree_init(X509_POLICY_TREE **ptree, STACK_OF(X509) *certs,
                        unsigned int flags)
        {
        X509_POLICY_TREE *tree;
        X509_POLICY_LEVEL *level;
        const X509_POLICY_CACHE *cache;
        X509_POLICY_DATA *data = NULL;
        X509 *x;
        int ret = 1;
        int i, n;
        int explicit_policy;
        int any_skip;
        int map_skip;
        *ptree = NULL;
        n = sk_X509_num(certs);

#if 0
        /* Disable policy mapping for now... */
        flags |= X509_V_FLAG_INHIBIT_MAP;
#endif

        if (flags & X509_V_FLAG_EXPLICIT_POLICY)
                explicit_policy = 0;
        else
                explicit_policy = n + 1;

        if (flags & X509_V_FLAG_INHIBIT_ANY)
                any_skip = 0;
        else
                any_skip = n + 1;

        if (flags & X509_V_FLAG_INHIBIT_MAP)
                map_skip = 0;
        else
                map_skip = n + 1;

        /* Can't do anything with just a trust anchor */
        if (n == 1)
                return 1;
        /* First setup policy cache in all certificates apart from the
         * trust anchor. Note any bad cache results on the way. Also can
         * calculate explicit_policy value at this point.
         */
        for (i = n - 2; i >= 0; i--)
                {
                x = sk_X509_value(certs, i);
                X509_check_purpose(x, -1, -1);
                cache = policy_cache_set(x);
                /* If cache NULL something bad happened: return immediately */
                if (cache == NULL)
                        return 0;
                /* If inconsistent extensions keep a note of it but continue */
                if (x->ex_flags & EXFLAG_INVALID_POLICY)
                        ret = -1;
                /* Otherwise if we have no data (hence no CertificatePolicies)
                 * and haven't already set an inconsistent code note it.
                 */
                else if ((ret == 1) && !cache->data)
                        ret = 2;
                if (explicit_policy > 0)
                        {
                        if (!(x->ex_flags & EXFLAG_SI))
                                explicit_policy--;
                        if ((cache->explicit_skip != -1)
                                && (cache->explicit_skip < explicit_policy))
                                explicit_policy = cache->explicit_skip;
                        }
                }

        if (ret != 1)
                {
                if (ret == 2 && !explicit_policy)
                        return 6;
                return ret;
                }


        /* If we get this far initialize the tree */

        tree = OPENSSL_malloc(sizeof(X509_POLICY_TREE));

        if (!tree)
                return 0;

        tree->flags = 0;
        tree->levels = OPENSSL_malloc(sizeof(X509_POLICY_LEVEL) * n);
        tree->nlevel = 0;
        tree->extra_data = NULL;
        tree->auth_policies = NULL;
        tree->user_policies = NULL;

        if (!tree->levels)
                {
                OPENSSL_free(tree);
                return 0;
                }

        memset(tree->levels, 0, n * sizeof(X509_POLICY_LEVEL));

        tree->nlevel = n;

        level = tree->levels;

        /* Root data: initialize to anyPolicy */

        data = policy_data_new(NULL, OBJ_nid2obj(NID_any_policy), 0);

        if (!data || !level_add_node(level, data, NULL, tree))
                goto bad_tree;

        for (i = n - 2; i >= 0; i--)
                {
                level++;
                x = sk_X509_value(certs, i);
                cache = policy_cache_set(x);
                CRYPTO_add(&x->references, 1, CRYPTO_LOCK_X509);
                level->cert = x;

                if (!cache->anyPolicy)
                                level->flags |= X509_V_FLAG_INHIBIT_ANY;

                /* Determine inhibit any and inhibit map flags */
                if (any_skip == 0)
                        {
                        /* Any matching allowed if certificate is self
                         * issued and not the last in the chain.
                         */
                        if (!(x->ex_flags & EXFLAG_SI) || (i == 0))
                                level->flags |= X509_V_FLAG_INHIBIT_ANY;
                        }
                else
                        {
                        if (!(x->ex_flags & EXFLAG_SI))
                                any_skip--;
                        if ((cache->any_skip >= 0)
                                && (cache->any_skip < any_skip))
                                any_skip = cache->any_skip;
                        }

                if (map_skip == 0)
                        level->flags |= X509_V_FLAG_INHIBIT_MAP;
                else
                        {
                        if (!(x->ex_flags & EXFLAG_SI))
                                map_skip--;
                        if ((cache->map_skip >= 0)
                                && (cache->map_skip < map_skip))
                                map_skip = cache->map_skip;
                        }

                }

        *ptree = tree;

        if (explicit_policy)
                return 1;
        else
                return 5;

        bad_tree:

        X509_policy_tree_free(tree);

        return 0;

        }

static int tree_link_matching_nodes(X509_POLICY_LEVEL *curr,
                                const X509_POLICY_DATA *data)
        {
        X509_POLICY_LEVEL *last = curr - 1;
        X509_POLICY_NODE *node;
        int i, matched = 0;
        /* Iterate through all in nodes linking matches */
        for (i = 0; i < sk_X509_POLICY_NODE_num(last->nodes); i++)
                {
                node = sk_X509_POLICY_NODE_value(last->nodes, i);
                if (policy_node_match(last, node, data->valid_policy))
                        {
                        if (!level_add_node(curr, data, node, NULL))
                                return 0;
                        matched = 1;
                        }
                }
        if (!matched && last->anyPolicy)
                {
                if (!level_add_node(curr, data, last->anyPolicy, NULL))
                        return 0;
                }
        return 1;
        }

/* This corresponds to RFC3280 6.1.3(d)(1):
 * link any data from CertificatePolicies onto matching parent
 * or anyPolicy if no match.
 */

static int tree_link_nodes(X509_POLICY_LEVEL *curr,
                                const X509_POLICY_CACHE *cache)
        {
        int i;
        X509_POLICY_DATA *data;

        for (i = 0; i < sk_X509_POLICY_DATA_num(cache->data); i++)
                {
                data = sk_X509_POLICY_DATA_value(cache->data, i);
                /* If a node is mapped any it doesn't have a corresponding
                 * CertificatePolicies entry. 
                 * However such an identical node would be created
                 * if anyPolicy matching is enabled because there would be
                 * no match with the parent valid_policy_set. So we create
                 * link because then it will have the mapping flags
                 * right and we can prune it later.
                 */
#if 0
                if ((data->flags & POLICY_DATA_FLAG_MAPPED_ANY)
                        && !(curr->flags & X509_V_FLAG_INHIBIT_ANY))
                        continue;
#endif
                /* Look for matching nodes in previous level */
                if (!tree_link_matching_nodes(curr, data))
                                return 0;
                }
        return 1;
        }

/* This corresponds to RFC3280 6.1.3(d)(2):
 * Create new data for any unmatched policies in the parent and link
 * to anyPolicy.
 */

static int tree_add_unmatched(X509_POLICY_LEVEL *curr,
                        const X509_POLICY_CACHE *cache,
                        const ASN1_OBJECT *id,
                        X509_POLICY_NODE *node,
                        X509_POLICY_TREE *tree)
        {
        X509_POLICY_DATA *data;
        if (id == NULL)
                id = node->data->valid_policy;
        /* Create a new node with qualifiers from anyPolicy and
         * id from unmatched node.
         */
        data = policy_data_new(NULL, id, node_critical(node));

        if (data == NULL)
                return 0;
        /* Curr may not have anyPolicy */
        data->qualifier_set = cache->anyPolicy->qualifier_set;
        data->flags |= POLICY_DATA_FLAG_SHARED_QUALIFIERS;
        if (!level_add_node(curr, data, node, tree))
                {
                policy_data_free(data);
                return 0;
                }

        return 1;
        }

static int tree_link_unmatched(X509_POLICY_LEVEL *curr,
                        const X509_POLICY_CACHE *cache,
                        X509_POLICY_NODE *node,
                        X509_POLICY_TREE *tree)
        {
        const X509_POLICY_LEVEL *last = curr - 1;
        int i;

        if (        (last->flags & X509_V_FLAG_INHIBIT_MAP)
                || !(node->data->flags & POLICY_DATA_FLAG_MAPPED))
                {
                /* If no policy mapping: matched if one child present */
                if (node->nchild)
                        return 1;
                if (!tree_add_unmatched(curr, cache, NULL, node, tree))
                        return 0;
                /* Add it */
                }
        else
                {
                /* If mapping: matched if one child per expected policy set */
                STACK_OF(ASN1_OBJECT) *expset = node->data->expected_policy_set;
                if (node->nchild == sk_ASN1_OBJECT_num(expset))
                        return 1;
                /* Locate unmatched nodes */
                for (i = 0; i < sk_ASN1_OBJECT_num(expset); i++)
                        {
                        ASN1_OBJECT *oid = sk_ASN1_OBJECT_value(expset, i);
                        if (level_find_node(curr, node, oid))
                                continue;
                        if (!tree_add_unmatched(curr, cache, oid, node, tree))
                                return 0;
                        }

                }

        return 1;

        }

static int tree_link_any(X509_POLICY_LEVEL *curr,
                        const X509_POLICY_CACHE *cache,
                        X509_POLICY_TREE *tree)
        {
        int i;
        /*X509_POLICY_DATA *data;*/
        X509_POLICY_NODE *node;
        X509_POLICY_LEVEL *last = curr - 1;

        for (i = 0; i < sk_X509_POLICY_NODE_num(last->nodes); i++)
                {
                node = sk_X509_POLICY_NODE_value(last->nodes, i);

                if (!tree_link_unmatched(curr, cache, node, tree))
                        return 0;

#if 0

                /* Skip any node with any children: we only want unmathced
                 * nodes.
                 *
                 * Note: need something better for policy mapping
                 * because each node may have multiple children 
                 */
                if (node->nchild)
                        continue;

                /* Create a new node with qualifiers from anyPolicy and
                 * id from unmatched node.
                 */
                data = policy_data_new(NULL, node->data->valid_policy, 
                                                node_critical(node));

                if (data == NULL)
                        return 0;
                /* Curr may not have anyPolicy */
                data->qualifier_set = cache->anyPolicy->qualifier_set;
                data->flags |= POLICY_DATA_FLAG_SHARED_QUALIFIERS;
                if (!level_add_node(curr, data, node, tree))
                        {
                        policy_data_free(data);
                        return 0;
                        }

#endif

                }
        /* Finally add link to anyPolicy */
        if (last->anyPolicy)
                {
                if (!level_add_node(curr, cache->anyPolicy,
                                                last->anyPolicy, NULL))
                        return 0;
                }
        return 1;
        }

/* Prune the tree: delete any child mapped child data on the current level
 * then proceed up the tree deleting any data with no children. If we ever
 * have no data on a level we can halt because the tree will be empty.
 */

static int tree_prune(X509_POLICY_TREE *tree, X509_POLICY_LEVEL *curr)
        {
        STACK_OF(X509_POLICY_NODE) *nodes;
        X509_POLICY_NODE *node;
        int i;
        nodes = curr->nodes;
        if (curr->flags & X509_V_FLAG_INHIBIT_MAP)
                {
                for (i = sk_X509_POLICY_NODE_num(nodes) - 1; i >= 0; i--)
                        {
                        node = sk_X509_POLICY_NODE_value(nodes, i);
                        /* Delete any mapped data: see RFC3280 XXXX */
                        if (node->data->flags & POLICY_DATA_FLAG_MAP_MASK)
                                {
                                node->parent->nchild--;
                                OPENSSL_free(node);
                                (void)sk_X509_POLICY_NODE_delete(nodes,i);
                                }
                        }
                }

        for(;;) {
                --curr;
                nodes = curr->nodes;
                for (i = sk_X509_POLICY_NODE_num(nodes) - 1; i >= 0; i--)
                        {
                        node = sk_X509_POLICY_NODE_value(nodes, i);
                        if (node->nchild == 0)
                                {
                                node->parent->nchild--;
                                OPENSSL_free(node);
                                (void)sk_X509_POLICY_NODE_delete(nodes, i);
                                }
                        }
                if (curr->anyPolicy && !curr->anyPolicy->nchild)
                        {
                        if (curr->anyPolicy->parent)
                                curr->anyPolicy->parent->nchild--;
                        OPENSSL_free(curr->anyPolicy);
                        curr->anyPolicy = NULL;
                        }
                if (curr == tree->levels)
                        {
                        /* If we zapped anyPolicy at top then tree is empty */
                        if (!curr->anyPolicy)
                                        return 2;
                        return 1;
                        }
                }

        return 1;

        }

static int tree_add_auth_node(STACK_OF(X509_POLICY_NODE) **pnodes,
                                                 X509_POLICY_NODE *pcy)
        {
        if (!*pnodes)
                {
                *pnodes = policy_node_cmp_new();
                if (!*pnodes)
                        return 0;
                }
        else if (sk_X509_POLICY_NODE_find(*pnodes, pcy) != -1)
                return 1;

        if (!sk_X509_POLICY_NODE_push(*pnodes, pcy))
                return 0;

        return 1;

        }

/* Calculate the authority set based on policy tree.
 * The 'pnodes' parameter is used as a store for the set of policy nodes
 * used to calculate the user set. If the authority set is not anyPolicy
 * then pnodes will just point to the authority set. If however the authority
 * set is anyPolicy then the set of valid policies (other than anyPolicy)
 * is store in pnodes. The return value of '2' is used in this case to indicate
 * that pnodes should be freed.
 */

static int tree_calculate_authority_set(X509_POLICY_TREE *tree,
                                        STACK_OF(X509_POLICY_NODE) **pnodes)
        {
        X509_POLICY_LEVEL *curr;
        X509_POLICY_NODE *node, *anyptr;
        STACK_OF(X509_POLICY_NODE) **addnodes;
        int i, j;
        curr = tree->levels + tree->nlevel - 1;

        /* If last level contains anyPolicy set is anyPolicy */
        if (curr->anyPolicy)
                {
                if (!tree_add_auth_node(&tree->auth_policies, curr->anyPolicy))
                        return 0;
                addnodes = pnodes;
                }
        else
                /* Add policies to authority set */
                addnodes = &tree->auth_policies;

        curr = tree->levels;
        for (i = 1; i < tree->nlevel; i++)
                {
                /* If no anyPolicy node on this this level it can't
                 * appear on lower levels so end search.
                 */
                if (!(anyptr = curr->anyPolicy))
                        break;
                curr++;
                for (j = 0; j < sk_X509_POLICY_NODE_num(curr->nodes); j++)
                        {
                        node = sk_X509_POLICY_NODE_value(curr->nodes, j);
                        if ((node->parent == anyptr)
                                && !tree_add_auth_node(addnodes, node))
                                        return 0;
                        }
                }

        if (addnodes == pnodes)
                return 2;

        *pnodes = tree->auth_policies;

        return 1;
        }

static int tree_calculate_user_set(X509_POLICY_TREE *tree,
                                STACK_OF(ASN1_OBJECT) *policy_oids,
                                STACK_OF(X509_POLICY_NODE) *auth_nodes)
        {
        int i;
        X509_POLICY_NODE *node;
        ASN1_OBJECT *oid;

        X509_POLICY_NODE *anyPolicy;
        X509_POLICY_DATA *extra;

        /* Check if anyPolicy present in authority constrained policy set:
         * this will happen if it is a leaf node.
         */

        if (sk_ASN1_OBJECT_num(policy_oids) <= 0)
                return 1;

        anyPolicy = tree->levels[tree->nlevel - 1].anyPolicy;

        for (i = 0; i < sk_ASN1_OBJECT_num(policy_oids); i++)
                {
                oid = sk_ASN1_OBJECT_value(policy_oids, i);
                if (OBJ_obj2nid(oid) == NID_any_policy)
                        {
                        tree->flags |= POLICY_FLAG_ANY_POLICY;
                        return 1;
                        }
                }

        for (i = 0; i < sk_ASN1_OBJECT_num(policy_oids); i++)
                {
                oid = sk_ASN1_OBJECT_value(policy_oids, i);
                node = tree_find_sk(auth_nodes, oid);
                if (!node)
                        {
                        if (!anyPolicy)
                                continue;
                        /* Create a new node with policy ID from user set
                         * and qualifiers from anyPolicy.
                         */
                        extra = policy_data_new(NULL, oid,
                                                node_critical(anyPolicy));
                        if (!extra)
                                return 0;
                        extra->qualifier_set = anyPolicy->data->qualifier_set;
                        extra->flags = POLICY_DATA_FLAG_SHARED_QUALIFIERS
                                                | POLICY_DATA_FLAG_EXTRA_NODE;
                        node = level_add_node(NULL, extra, anyPolicy->parent,
                                                tree);
                        }
                if (!tree->user_policies)
                        {
                        tree->user_policies = sk_X509_POLICY_NODE_new_null();
                        if (!tree->user_policies)
                                return 1;
                        }
                if (!sk_X509_POLICY_NODE_push(tree->user_policies, node))
                        return 0;
                }
        return 1;

        }

static int tree_evaluate(X509_POLICY_TREE *tree)
        {
        int ret, i;
        X509_POLICY_LEVEL *curr = tree->levels + 1;
        const X509_POLICY_CACHE *cache;

        for(i = 1; i < tree->nlevel; i++, curr++)
                {
                cache = policy_cache_set(curr->cert);
                if (!tree_link_nodes(curr, cache))
                        return 0;

                if (!(curr->flags & X509_V_FLAG_INHIBIT_ANY)
                        && !tree_link_any(curr, cache, tree))
                        return 0;
        tree_print("before tree_prune()", tree, curr);
                ret = tree_prune(tree, curr);
                if (ret != 1)
                        return ret;
                }

        return 1;

        }

static void exnode_free(X509_POLICY_NODE *node)
        {
        if (node->data && (node->data->flags & POLICY_DATA_FLAG_EXTRA_NODE))
                OPENSSL_free(node);
        }


void X509_policy_tree_free(X509_POLICY_TREE *tree)
        {
        X509_POLICY_LEVEL *curr;
        int i;

        if (!tree)
                return;

        sk_X509_POLICY_NODE_free(tree->auth_policies);
        sk_X509_POLICY_NODE_pop_free(tree->user_policies, exnode_free);

        for(i = 0, curr = tree->levels; i < tree->nlevel; i++, curr++)
                {
                if (curr->cert)
                        X509_free(curr->cert);
                if (curr->nodes)
                        sk_X509_POLICY_NODE_pop_free(curr->nodes,
                                                policy_node_free);
                if (curr->anyPolicy)
                        policy_node_free(curr->anyPolicy);
                }

        if (tree->extra_data)
                sk_X509_POLICY_DATA_pop_free(tree->extra_data,
                                                policy_data_free);

        OPENSSL_free(tree->levels);
        OPENSSL_free(tree);

        }

/*-
 * Application policy checking function.
 * Return codes:
 *  0   Internal Error.
 *  1   Successful.
 * -1   One or more certificates contain invalid or inconsistent extensions
 * -2   User constrained policy set empty and requireExplicit true.
 */

int X509_policy_check(X509_POLICY_TREE **ptree, int *pexplicit_policy,
                        STACK_OF(X509) *certs,
                        STACK_OF(ASN1_OBJECT) *policy_oids,
                        unsigned int flags)
        {
        int ret;
        X509_POLICY_TREE *tree = NULL;
        STACK_OF(X509_POLICY_NODE) *nodes, *auth_nodes = NULL;
        *ptree = NULL;

        *pexplicit_policy = 0;
        ret = tree_init(&tree, certs, flags);

        switch (ret)
                {

                /* Tree empty requireExplicit False: OK */
                case 2:
                return 1;

                /* Some internal error */
                case -1:
                return -1;

                /* Some internal error */
                case 0:
                return 0;

                /* Tree empty requireExplicit True: Error */

                case 6:
                *pexplicit_policy = 1;
                return -2;

                /* Tree OK requireExplicit True: OK and continue */
                case 5:
                *pexplicit_policy = 1;
                break;

                /* Tree OK: continue */

                case 1:
                if (!tree)
                        /*
                         * tree_init() returns success and a null tree
                         * if it's just looking at a trust anchor.
                         * I'm not sure that returning success here is
                         * correct, but I'm sure that reporting this
                         * as an internal error which our caller
                         * interprets as a malloc failure is wrong.
                         */
                        return 1;
                break;
                }

        if (!tree) goto error;
        ret = tree_evaluate(tree);

        tree_print("tree_evaluate()", tree, NULL);

        if (ret <= 0)
                goto error;

        /* Return value 2 means tree empty */
        if (ret == 2)
                {
                X509_policy_tree_free(tree);
                if (*pexplicit_policy)
                        return -2;
                else
                        return 1;
                }

        /* Tree is not empty: continue */

        ret = tree_calculate_authority_set(tree, &auth_nodes);

        if (!ret)
                goto error;

        if (!tree_calculate_user_set(tree, policy_oids, auth_nodes))
                goto error;
        
        if (ret == 2)
                sk_X509_POLICY_NODE_free(auth_nodes);

        if (tree)
                *ptree = tree;

        if (*pexplicit_policy)
                {
                nodes = X509_policy_tree_get0_user_policies(tree);
                if (sk_X509_POLICY_NODE_num(nodes) <= 0)
                        return -2;
                }

        return 1;

        error:

        X509_policy_tree_free(tree);

        return 0;

        }