From: beck Date: Wed, 26 Apr 2023 18:56:52 +0000 (+0000) Subject: Import policy.c from BoringSSL as x509_policy.c X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=25478f0306a141c41bb38ecdf548f2446bedb642;p=openbsd Import policy.c from BoringSSL as x509_policy.c This is an implementation of the X509 policy processing using a DAG instead of a tree to avoid the problem of exponential expansion of the policy tree as specified in RFC 5280 For details see: https://boringssl-review.googlesource.com/c/boringssl/+/55762 ok tb@ jsing@ --- diff --git a/lib/libcrypto/x509/x509_policy.c b/lib/libcrypto/x509/x509_policy.c new file mode 100644 index 00000000000..b0c27126c4e --- /dev/null +++ b/lib/libcrypto/x509/x509_policy.c @@ -0,0 +1,790 @@ +/* Copyright (c) 2022, Google Inc. + * + * Permission to use, copy, modify, and/or distribute this software for any + * purpose with or without fee is hereby granted, provided that the above + * copyright notice and this permission notice appear in all copies. + * + * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES + * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF + * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY + * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES + * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION + * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN + * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */ + +#include + +#include + +#include +#include +#include +#include + +#include "../internal.h" +#include "../x509v3/internal.h" +#include "internal.h" + + +// This file computes the X.509 policy tree, as described in RFC 5280, section +// 6.1. It differs in that: +// +// (1) It does not track "qualifier_set". This is not needed as it is not +// output by this implementation. +// +// (2) It builds a directed acyclic graph, rather than a tree. When a given +// policy matches multiple parents, RFC 5280 makes a separate node for +// each parent. This representation condenses them into one node with +// multiple parents. Thus we refer to this structure as a "policy graph", +// rather than a "policy tree". +// +// (3) "expected_policy_set" is not tracked explicitly and built temporarily +// as part of building the graph. +// +// (4) anyPolicy nodes are not tracked explicitly. +// +// (5) Some pruning steps are deferred to when policies are evaluated, as a +// reachability pass. + +// An X509_POLICY_NODE is a node in the policy graph. It corresponds to a node +// from RFC 5280, section 6.1.2, step (a), but we store some fields differently. +typedef struct x509_policy_node_st { + // policy is the "valid_policy" field from RFC 5280. + ASN1_OBJECT *policy; + + // parent_policies, if non-empty, is the list of "valid_policy" values for all + // nodes which are a parent of this node. In this case, no entry in this list + // will be anyPolicy. This list is in no particular order and may contain + // duplicates if the corresponding certificate had duplicate mappings. + // + // If empty, this node has a single parent, anyPolicy. The node is then a root + // policies, and is in authorities-constrained-policy-set if it has a path to + // a leaf node. + // + // Note it is not possible for a policy to have both anyPolicy and a + // concrete policy as a parent. Section 6.1.3, step (d.1.ii) only runs if + // there was no match in step (d.1.i). We do not need to represent a parent + // list of, say, {anyPolicy, OID1, OID2}. + STACK_OF(ASN1_OBJECT) *parent_policies; + + // mapped is one if this node matches a policy mapping in the certificate and + // zero otherwise. + int mapped; + + // reachable is one if this node is reachable from some valid policy in the + // end-entity certificate. It is computed during |has_explicit_policy|. + int reachable; +} X509_POLICY_NODE; + +DEFINE_STACK_OF(X509_POLICY_NODE) + +// An X509_POLICY_LEVEL is the collection of nodes at the same depth in the +// policy graph. This structure can also be used to represent a level's +// "expected_policy_set" values. See |process_policy_mappings|. +typedef struct x509_policy_level_st { + // nodes is the list of nodes at this depth, except for the anyPolicy node, if + // any. This list is sorted by policy OID for efficient lookup. + STACK_OF(X509_POLICY_NODE) *nodes; + + // has_any_policy is one if there is an anyPolicy node at this depth, and zero + // otherwise. + int has_any_policy; +} X509_POLICY_LEVEL; + +DEFINE_STACK_OF(X509_POLICY_LEVEL) + +static int is_any_policy(const ASN1_OBJECT *obj) { + return OBJ_obj2nid(obj) == NID_any_policy; +} + +static void x509_policy_node_free(X509_POLICY_NODE *node) { + if (node != NULL) { + ASN1_OBJECT_free(node->policy); + sk_ASN1_OBJECT_pop_free(node->parent_policies, ASN1_OBJECT_free); + OPENSSL_free(node); + } +} + +static X509_POLICY_NODE *x509_policy_node_new(const ASN1_OBJECT *policy) { + assert(!is_any_policy(policy)); + X509_POLICY_NODE *node = OPENSSL_malloc(sizeof(X509_POLICY_NODE)); + if (node == NULL) { + return NULL; + } + OPENSSL_memset(node, 0, sizeof(X509_POLICY_NODE)); + node->policy = OBJ_dup(policy); + node->parent_policies = sk_ASN1_OBJECT_new_null(); + if (node->policy == NULL || node->parent_policies == NULL) { + x509_policy_node_free(node); + return NULL; + } + return node; +} + +static int x509_policy_node_cmp(const X509_POLICY_NODE *const *a, + const X509_POLICY_NODE *const *b) { + return OBJ_cmp((*a)->policy, (*b)->policy); +} + +static void x509_policy_level_free(X509_POLICY_LEVEL *level) { + if (level != NULL) { + sk_X509_POLICY_NODE_pop_free(level->nodes, x509_policy_node_free); + OPENSSL_free(level); + } +} + +static X509_POLICY_LEVEL *x509_policy_level_new(void) { + X509_POLICY_LEVEL *level = OPENSSL_malloc(sizeof(X509_POLICY_LEVEL)); + if (level == NULL) { + return NULL; + } + OPENSSL_memset(level, 0, sizeof(X509_POLICY_LEVEL)); + level->nodes = sk_X509_POLICY_NODE_new(x509_policy_node_cmp); + if (level->nodes == NULL) { + x509_policy_level_free(level); + return NULL; + } + return level; +} + +static int x509_policy_level_is_empty(const X509_POLICY_LEVEL *level) { + return !level->has_any_policy && sk_X509_POLICY_NODE_num(level->nodes) == 0; +} + +static void x509_policy_level_clear(X509_POLICY_LEVEL *level) { + level->has_any_policy = 0; + for (size_t i = 0; i < sk_X509_POLICY_NODE_num(level->nodes); i++) { + x509_policy_node_free(sk_X509_POLICY_NODE_value(level->nodes, i)); + } + sk_X509_POLICY_NODE_zero(level->nodes); +} + +// x509_policy_level_find returns the node in |level| corresponding to |policy|, +// or NULL if none exists. +static X509_POLICY_NODE *x509_policy_level_find(X509_POLICY_LEVEL *level, + const ASN1_OBJECT *policy) { + assert(sk_X509_POLICY_NODE_is_sorted(level->nodes)); + X509_POLICY_NODE node; + node.policy = (ASN1_OBJECT *)policy; + size_t idx; + if (!sk_X509_POLICY_NODE_find(level->nodes, &idx, &node)) { + return NULL; + } + return sk_X509_POLICY_NODE_value(level->nodes, idx); +} + +// x509_policy_level_add_nodes adds the nodes in |nodes| to |level|. It returns +// one on success and zero on error. No policy in |nodes| may already be present +// in |level|. This function modifies |nodes| to avoid making a copy, but the +// caller is still responsible for releasing |nodes| itself. +// +// This function is used to add nodes to |level| in bulk, and avoid resorting +// |level| after each addition. +static int x509_policy_level_add_nodes(X509_POLICY_LEVEL *level, + STACK_OF(X509_POLICY_NODE) *nodes) { + for (size_t i = 0; i < sk_X509_POLICY_NODE_num(nodes); i++) { + X509_POLICY_NODE *node = sk_X509_POLICY_NODE_value(nodes, i); + if (!sk_X509_POLICY_NODE_push(level->nodes, node)) { + return 0; + } + sk_X509_POLICY_NODE_set(nodes, i, NULL); + } + sk_X509_POLICY_NODE_sort(level->nodes); + +#if !defined(NDEBUG) + // There should be no duplicate nodes. + for (size_t i = 1; i < sk_X509_POLICY_NODE_num(level->nodes); i++) { + assert(OBJ_cmp(sk_X509_POLICY_NODE_value(level->nodes, i - 1)->policy, + sk_X509_POLICY_NODE_value(level->nodes, i)->policy) != 0); + } +#endif + return 1; +} + +static int policyinfo_cmp(const POLICYINFO *const *a, + const POLICYINFO *const *b) { + return OBJ_cmp((*a)->policyid, (*b)->policyid); +} + +static int delete_if_not_in_policies(X509_POLICY_NODE *node, void *data) { + const CERTIFICATEPOLICIES *policies = data; + assert(sk_POLICYINFO_is_sorted(policies)); + POLICYINFO info; + info.policyid = node->policy; + if (sk_POLICYINFO_find(policies, NULL, &info)) { + return 0; + } + x509_policy_node_free(node); + return 1; +} + +// process_certificate_policies updates |level| to incorporate |x509|'s +// certificate policies extension. This implements steps (d) and (e) of RFC +// 5280, section 6.1.3. |level| must contain the previous level's +// "expected_policy_set" information. For all but the top-most level, this is +// the output of |process_policy_mappings|. |any_policy_allowed| specifies +// whether anyPolicy is allowed or inhibited, taking into account the exception +// for self-issued certificates. +static int process_certificate_policies(const X509 *x509, + X509_POLICY_LEVEL *level, + int any_policy_allowed) { + int ret = 0; + int critical; + STACK_OF(X509_POLICY_NODE) *new_nodes = NULL; + CERTIFICATEPOLICIES *policies = + X509_get_ext_d2i(x509, NID_certificate_policies, &critical, NULL); + if (policies == NULL) { + if (critical != -1) { + return 0; // Syntax error in the extension. + } + + // RFC 5280, section 6.1.3, step (e). + x509_policy_level_clear(level); + return 1; + } + + // certificatePolicies may not be empty. See RFC 5280, section 4.2.1.4. + // TODO(https://crbug.com/boringssl/443): Move this check into the parser. + if (sk_POLICYINFO_num(policies) == 0) { + OPENSSL_PUT_ERROR(X509, X509_R_INVALID_POLICY_EXTENSION); + goto err; + } + + sk_POLICYINFO_set_cmp_func(policies, policyinfo_cmp); + sk_POLICYINFO_sort(policies); + int cert_has_any_policy = 0; + for (size_t i = 0; i < sk_POLICYINFO_num(policies); i++) { + const POLICYINFO *policy = sk_POLICYINFO_value(policies, i); + if (is_any_policy(policy->policyid)) { + cert_has_any_policy = 1; + } + if (i > 0 && OBJ_cmp(sk_POLICYINFO_value(policies, i - 1)->policyid, + policy->policyid) == 0) { + // Per RFC 5280, section 4.2.1.4, |policies| may not have duplicates. + OPENSSL_PUT_ERROR(X509, X509_R_INVALID_POLICY_EXTENSION); + goto err; + } + } + + // This does the same thing as RFC 5280, section 6.1.3, step (d), though in + // a slighty different order. |level| currently contains "expected_policy_set" + // values of the previous level. See |process_policy_mappings| for details. + const int previous_level_has_any_policy = level->has_any_policy; + + // First, we handle steps (d.1.i) and (d.2). The net effect of these two steps + // is to intersect |level| with |policies|, ignoring anyPolicy if it is + // inhibited. + if (!cert_has_any_policy || !any_policy_allowed) { + sk_X509_POLICY_NODE_delete_if(level->nodes, delete_if_not_in_policies, + policies); + level->has_any_policy = 0; + } + + // Step (d.1.ii) may attach new nodes to the previous level's anyPolicy node. + if (previous_level_has_any_policy) { + new_nodes = sk_X509_POLICY_NODE_new_null(); + if (new_nodes == NULL) { + goto err; + } + for (size_t i = 0; i < sk_POLICYINFO_num(policies); i++) { + const POLICYINFO *policy = sk_POLICYINFO_value(policies, i); + // Though we've reordered the steps slightly, |policy| is in |level| if + // and only if it would have been a match in step (d.1.ii). + if (!is_any_policy(policy->policyid) && + x509_policy_level_find(level, policy->policyid) == NULL) { + X509_POLICY_NODE *node = x509_policy_node_new(policy->policyid); + if (node == NULL || // + !sk_X509_POLICY_NODE_push(new_nodes, node)) { + x509_policy_node_free(node); + goto err; + } + } + } + if (!x509_policy_level_add_nodes(level, new_nodes)) { + goto err; + } + } + + ret = 1; + +err: + sk_X509_POLICY_NODE_pop_free(new_nodes, x509_policy_node_free); + CERTIFICATEPOLICIES_free(policies); + return ret; +} + +static int compare_issuer_policy(const POLICY_MAPPING *const *a, + const POLICY_MAPPING *const *b) { + return OBJ_cmp((*a)->issuerDomainPolicy, (*b)->issuerDomainPolicy); +} + +static int compare_subject_policy(const POLICY_MAPPING *const *a, + const POLICY_MAPPING *const *b) { + return OBJ_cmp((*a)->subjectDomainPolicy, (*b)->subjectDomainPolicy); +} + +static int delete_if_mapped(X509_POLICY_NODE *node, void *data) { + const POLICY_MAPPINGS *mappings = data; + // |mappings| must have been sorted by |compare_issuer_policy|. + assert(sk_POLICY_MAPPING_is_sorted(mappings)); + POLICY_MAPPING mapping; + mapping.issuerDomainPolicy = node->policy; + if (!sk_POLICY_MAPPING_find(mappings, /*out_index=*/NULL, &mapping)) { + return 0; + } + x509_policy_node_free(node); + return 1; +} + +// process_policy_mappings processes the policy mappings extension of |cert|, +// whose corresponding graph level is |level|. |mapping_allowed| specifies +// whether policy mapping is inhibited at this point. On success, it returns an +// |X509_POLICY_LEVEL| containing the "expected_policy_set" for |level|. On +// error, it returns NULL. This implements steps (a) and (b) of RFC 5280, +// section 6.1.4. +// +// We represent the "expected_policy_set" as an |X509_POLICY_LEVEL|. +// |has_any_policy| indicates whether there is an anyPolicy node with +// "expected_policy_set" of {anyPolicy}. If a node with policy oid P1 contains +// P2 in its "expected_policy_set", the level will contain a node of policy P2 +// with P1 in |parent_policies|. +// +// This is equivalent to the |X509_POLICY_LEVEL| that would result if the next +// certificats contained anyPolicy. |process_certificate_policies| will filter +// this result down to compute the actual level. +static X509_POLICY_LEVEL *process_policy_mappings(const X509 *cert, + X509_POLICY_LEVEL *level, + int mapping_allowed) { + int ok = 0; + STACK_OF(X509_POLICY_NODE) *new_nodes = NULL; + X509_POLICY_LEVEL *next = NULL; + int critical; + POLICY_MAPPINGS *mappings = + X509_get_ext_d2i(cert, NID_policy_mappings, &critical, NULL); + if (mappings == NULL && critical != -1) { + // Syntax error in the policy mappings extension. + goto err; + } + + if (mappings != NULL) { + // PolicyMappings may not be empty. See RFC 5280, section 4.2.1.5. + // TODO(https://crbug.com/boringssl/443): Move this check into the parser. + if (sk_POLICY_MAPPING_num(mappings) == 0) { + OPENSSL_PUT_ERROR(X509, X509_R_INVALID_POLICY_EXTENSION); + goto err; + } + + // RFC 5280, section 6.1.4, step (a). + for (size_t i = 0; i < sk_POLICY_MAPPING_num(mappings); i++) { + POLICY_MAPPING *mapping = sk_POLICY_MAPPING_value(mappings, i); + if (is_any_policy(mapping->issuerDomainPolicy) || + is_any_policy(mapping->subjectDomainPolicy)) { + goto err; + } + } + + // Sort to group by issuerDomainPolicy. + sk_POLICY_MAPPING_set_cmp_func(mappings, compare_issuer_policy); + sk_POLICY_MAPPING_sort(mappings); + + if (mapping_allowed) { + // Mark nodes as mapped, and add any nodes to |level| which may be needed + // as part of RFC 5280, section 6.1.4, step (b.1). + new_nodes = sk_X509_POLICY_NODE_new_null(); + if (new_nodes == NULL) { + goto err; + } + const ASN1_OBJECT *last_policy = NULL; + for (size_t i = 0; i < sk_POLICY_MAPPING_num(mappings); i++) { + const POLICY_MAPPING *mapping = sk_POLICY_MAPPING_value(mappings, i); + // There may be multiple mappings with the same |issuerDomainPolicy|. + if (last_policy != NULL && + OBJ_cmp(mapping->issuerDomainPolicy, last_policy) == 0) { + continue; + } + last_policy = mapping->issuerDomainPolicy; + + X509_POLICY_NODE *node = + x509_policy_level_find(level, mapping->issuerDomainPolicy); + if (node == NULL) { + if (!level->has_any_policy) { + continue; + } + node = x509_policy_node_new(mapping->issuerDomainPolicy); + if (node == NULL || // + !sk_X509_POLICY_NODE_push(new_nodes, node)) { + x509_policy_node_free(node); + goto err; + } + } + node->mapped = 1; + } + if (!x509_policy_level_add_nodes(level, new_nodes)) { + goto err; + } + } else { + // RFC 5280, section 6.1.4, step (b.2). If mapping is inhibited, delete + // all mapped nodes. + sk_X509_POLICY_NODE_delete_if(level->nodes, delete_if_mapped, mappings); + sk_POLICY_MAPPING_pop_free(mappings, POLICY_MAPPING_free); + mappings = NULL; + } + } + + // If a node was not mapped, it retains the original "explicit_policy_set" + // value, itself. Add those to |mappings|. + if (mappings == NULL) { + mappings = sk_POLICY_MAPPING_new_null(); + if (mappings == NULL) { + goto err; + } + } + for (size_t i = 0; i < sk_X509_POLICY_NODE_num(level->nodes); i++) { + X509_POLICY_NODE *node = sk_X509_POLICY_NODE_value(level->nodes, i); + if (!node->mapped) { + POLICY_MAPPING *mapping = POLICY_MAPPING_new(); + if (mapping == NULL) { + goto err; + } + mapping->issuerDomainPolicy = OBJ_dup(node->policy); + mapping->subjectDomainPolicy = OBJ_dup(node->policy); + if (mapping->issuerDomainPolicy == NULL || + mapping->subjectDomainPolicy == NULL || + !sk_POLICY_MAPPING_push(mappings, mapping)) { + POLICY_MAPPING_free(mapping); + goto err; + } + } + } + + // Sort to group by subjectDomainPolicy. + sk_POLICY_MAPPING_set_cmp_func(mappings, compare_subject_policy); + sk_POLICY_MAPPING_sort(mappings); + + // Convert |mappings| to our "expected_policy_set" representation. + next = x509_policy_level_new(); + if (next == NULL) { + goto err; + } + next->has_any_policy = level->has_any_policy; + + X509_POLICY_NODE *last_node = NULL; + for (size_t i = 0; i < sk_POLICY_MAPPING_num(mappings); i++) { + POLICY_MAPPING *mapping = sk_POLICY_MAPPING_value(mappings, i); + // Skip mappings where |issuerDomainPolicy| does not appear in the graph. + if (!level->has_any_policy && + x509_policy_level_find(level, mapping->issuerDomainPolicy) == NULL) { + continue; + } + + if (last_node == NULL || + OBJ_cmp(last_node->policy, mapping->subjectDomainPolicy) != 0) { + last_node = x509_policy_node_new(mapping->subjectDomainPolicy); + if (last_node == NULL || + !sk_X509_POLICY_NODE_push(next->nodes, last_node)) { + x509_policy_node_free(last_node); + goto err; + } + } + + if (!sk_ASN1_OBJECT_push(last_node->parent_policies, + mapping->issuerDomainPolicy)) { + goto err; + } + mapping->issuerDomainPolicy = NULL; + } + + sk_X509_POLICY_NODE_sort(next->nodes); + ok = 1; + +err: + if (!ok) { + x509_policy_level_free(next); + next = NULL; + } + + sk_POLICY_MAPPING_pop_free(mappings, POLICY_MAPPING_free); + sk_X509_POLICY_NODE_pop_free(new_nodes, x509_policy_node_free); + return next; +} + +// apply_skip_certs, if |skip_certs| is non-NULL, sets |*value| to the minimum +// of its current value and |skip_certs|. It returns one on success and zero if +// |skip_certs| is negative. +static int apply_skip_certs(const ASN1_INTEGER *skip_certs, size_t *value) { + if (skip_certs == NULL) { + return 1; + } + + // TODO(https://crbug.com/boringssl/443): Move this check into the parser. + if (skip_certs->type & V_ASN1_NEG) { + OPENSSL_PUT_ERROR(X509, X509_R_INVALID_POLICY_EXTENSION); + return 0; + } + + // If |skip_certs| does not fit in |uint64_t|, it must exceed |*value|. + uint64_t u64; + if (ASN1_INTEGER_get_uint64(&u64, skip_certs) && u64 < *value) { + *value = (size_t)u64; + } + ERR_clear_error(); + return 1; +} + +// process_policy_constraints updates |*explicit_policy|, |*policy_mapping|, and +// |*inhibit_any_policy| according to |x509|'s policy constraints and inhibit +// anyPolicy extensions. It returns one on success and zero on error. This +// implements steps (i) and (j) of RFC 5280, section 6.1.4. +static int process_policy_constraints(const X509 *x509, size_t *explicit_policy, + size_t *policy_mapping, + size_t *inhibit_any_policy) { + int critical; + POLICY_CONSTRAINTS *constraints = + X509_get_ext_d2i(x509, NID_policy_constraints, &critical, NULL); + if (constraints == NULL && critical != -1) { + return 0; + } + if (constraints != NULL) { + if (constraints->requireExplicitPolicy == NULL && + constraints->inhibitPolicyMapping == NULL) { + // Per RFC 5280, section 4.2.1.11, at least one of the fields must be + // present. + OPENSSL_PUT_ERROR(X509, X509_R_INVALID_POLICY_EXTENSION); + POLICY_CONSTRAINTS_free(constraints); + return 0; + } + int ok = + apply_skip_certs(constraints->requireExplicitPolicy, explicit_policy) && + apply_skip_certs(constraints->inhibitPolicyMapping, policy_mapping); + POLICY_CONSTRAINTS_free(constraints); + if (!ok) { + return 0; + } + } + + ASN1_INTEGER *inhibit_any_policy_ext = + X509_get_ext_d2i(x509, NID_inhibit_any_policy, &critical, NULL); + if (inhibit_any_policy_ext == NULL && critical != -1) { + return 0; + } + int ok = apply_skip_certs(inhibit_any_policy_ext, inhibit_any_policy); + ASN1_INTEGER_free(inhibit_any_policy_ext); + return ok; +} + +// has_explicit_policy returns one if the set of authority-space policy OIDs +// |levels| has some non-empty intersection with |user_policies|, and zero +// otherwise. This mirrors the logic in RFC 5280, section 6.1.5, step (g). This +// function modifies |levels| and should only be called at the end of policy +// evaluation. +static int has_explicit_policy(STACK_OF(X509_POLICY_LEVEL) *levels, + const STACK_OF(ASN1_OBJECT) *user_policies) { + assert(user_policies == NULL || sk_ASN1_OBJECT_is_sorted(user_policies)); + + // Step (g.i). If the policy graph is empty, the intersection is empty. + size_t num_levels = sk_X509_POLICY_LEVEL_num(levels); + X509_POLICY_LEVEL *level = sk_X509_POLICY_LEVEL_value(levels, num_levels - 1); + if (x509_policy_level_is_empty(level)) { + return 0; + } + + // If |user_policies| is empty, we interpret it as having a single anyPolicy + // value. The caller may also have supplied anyPolicy explicitly. + int user_has_any_policy = sk_ASN1_OBJECT_num(user_policies) == 0; + for (size_t i = 0; i < sk_ASN1_OBJECT_num(user_policies); i++) { + if (is_any_policy(sk_ASN1_OBJECT_value(user_policies, i))) { + user_has_any_policy = 1; + break; + } + } + + // Step (g.ii). If the policy graph is not empty and the user set contains + // anyPolicy, the intersection is the entire (non-empty) graph. + if (user_has_any_policy) { + return 1; + } + + // Step (g.iii) does not delete anyPolicy nodes, so if the graph has + // anyPolicy, some explicit policy will survive. The actual intersection may + // synthesize some nodes in step (g.iii.3), but we do not return the policy + // list itself, so we skip actually computing this. + if (level->has_any_policy) { + return 1; + } + + // We defer pruning the tree, so as we look for nodes with parent anyPolicy, + // step (g.iii.1), we must limit to nodes reachable from the bottommost level. + // Start by marking each of those nodes as reachable. + for (size_t i = 0; i < sk_X509_POLICY_NODE_num(level->nodes); i++) { + sk_X509_POLICY_NODE_value(level->nodes, i)->reachable = 1; + } + + for (size_t i = num_levels - 1; i < num_levels; i--) { + level = sk_X509_POLICY_LEVEL_value(levels, i); + for (size_t j = 0; j < sk_X509_POLICY_NODE_num(level->nodes); j++) { + X509_POLICY_NODE *node = sk_X509_POLICY_NODE_value(level->nodes, j); + if (!node->reachable) { + continue; + } + if (sk_ASN1_OBJECT_num(node->parent_policies) == 0) { + // |node|'s parent is anyPolicy and is part of "valid_policy_node_set". + // If it exists in |user_policies|, the intersection is non-empty and we + // can return immediately. + if (sk_ASN1_OBJECT_find(user_policies, /*out_index=*/NULL, + node->policy)) { + return 1; + } + } else if (i > 0) { + // |node|'s parents are concrete policies. Mark the parents reachable, + // to be inspected by the next loop iteration. + X509_POLICY_LEVEL *prev = sk_X509_POLICY_LEVEL_value(levels, i - 1); + for (size_t k = 0; k < sk_ASN1_OBJECT_num(node->parent_policies); k++) { + X509_POLICY_NODE *parent = x509_policy_level_find( + prev, sk_ASN1_OBJECT_value(node->parent_policies, k)); + if (parent != NULL) { + parent->reachable = 1; + } + } + } + } + } + + return 0; +} + +static int asn1_object_cmp(const ASN1_OBJECT *const *a, + const ASN1_OBJECT *const *b) { + return OBJ_cmp(*a, *b); +} + +int X509_policy_check(const STACK_OF(X509) *certs, + const STACK_OF(ASN1_OBJECT) *user_policies, + unsigned long flags, X509 **out_current_cert) { + *out_current_cert = NULL; + int ret = X509_V_ERR_OUT_OF_MEM; + X509_POLICY_LEVEL *level = NULL; + STACK_OF(X509_POLICY_LEVEL) *levels = NULL; + STACK_OF(ASN1_OBJECT) *user_policies_sorted = NULL; + size_t num_certs = sk_X509_num(certs); + + // Skip policy checking if the chain is just the trust anchor. + if (num_certs <= 1) { + return X509_V_OK; + } + + // See RFC 5280, section 6.1.2, steps (d) through (f). + size_t explicit_policy = + (flags & X509_V_FLAG_EXPLICIT_POLICY) ? 0 : num_certs + 1; + size_t inhibit_any_policy = + (flags & X509_V_FLAG_INHIBIT_ANY) ? 0 : num_certs + 1; + size_t policy_mapping = + (flags & X509_V_FLAG_INHIBIT_MAP) ? 0 : num_certs + 1; + + levels = sk_X509_POLICY_LEVEL_new_null(); + if (levels == NULL) { + goto err; + } + + for (size_t i = num_certs - 2; i < num_certs; i--) { + X509 *cert = sk_X509_value(certs, i); + if (!x509v3_cache_extensions(cert)) { + goto err; + } + const int is_self_issued = (cert->ex_flags & EXFLAG_SI) != 0; + + if (level == NULL) { + assert(i == num_certs - 2); + level = x509_policy_level_new(); + if (level == NULL) { + goto err; + } + level->has_any_policy = 1; + } + + // RFC 5280, section 6.1.3, steps (d) and (e). |any_policy_allowed| is + // computed as in step (d.2). + const int any_policy_allowed = + inhibit_any_policy > 0 || (i > 0 && is_self_issued); + if (!process_certificate_policies(cert, level, any_policy_allowed)) { + ret = X509_V_ERR_INVALID_POLICY_EXTENSION; + *out_current_cert = cert; + goto err; + } + + // RFC 5280, section 6.1.3, step (f). + if (explicit_policy == 0 && x509_policy_level_is_empty(level)) { + ret = X509_V_ERR_NO_EXPLICIT_POLICY; + goto err; + } + + // Insert into the list. + if (!sk_X509_POLICY_LEVEL_push(levels, level)) { + goto err; + } + X509_POLICY_LEVEL *current_level = level; + level = NULL; + + // If this is not the leaf certificate, we go to section 6.1.4. If it + // is the leaf certificate, we go to section 6.1.5 instead. + if (i != 0) { + // RFC 5280, section 6.1.4, steps (a) and (b). + level = process_policy_mappings(cert, current_level, policy_mapping > 0); + if (level == NULL) { + ret = X509_V_ERR_INVALID_POLICY_EXTENSION; + *out_current_cert = cert; + goto err; + } + } + + // RFC 5280, section 6.1.4, step (h-j) for non-leaves, and section 6.1.5, + // step (a-b) for leaves. In the leaf case, RFC 5280 says only to update + // |explicit_policy|, but |policy_mapping| and |inhibit_any_policy| are no + // longer read at this point, so we use the same process. + if (i == 0 || !is_self_issued) { + if (explicit_policy > 0) { + explicit_policy--; + } + if (policy_mapping > 0) { + policy_mapping--; + } + if (inhibit_any_policy > 0) { + inhibit_any_policy--; + } + } + if (!process_policy_constraints(cert, &explicit_policy, &policy_mapping, + &inhibit_any_policy)) { + ret = X509_V_ERR_INVALID_POLICY_EXTENSION; + *out_current_cert = cert; + goto err; + } + } + + // RFC 5280, section 6.1.5, step (g). We do not output the policy set, so it + // is only necessary to check if the user-constrained-policy-set is not empty. + if (explicit_policy == 0) { + // Build a sorted copy of |user_policies| for more efficient lookup. + if (user_policies != NULL) { + user_policies_sorted = sk_ASN1_OBJECT_dup(user_policies); + if (user_policies_sorted == NULL) { + goto err; + } + sk_ASN1_OBJECT_set_cmp_func(user_policies_sorted, asn1_object_cmp); + sk_ASN1_OBJECT_sort(user_policies_sorted); + } + + if (!has_explicit_policy(levels, user_policies_sorted)) { + ret = X509_V_ERR_NO_EXPLICIT_POLICY; + goto err; + } + } + + ret = X509_V_OK; + +err: + x509_policy_level_free(level); + // |user_policies_sorted|'s contents are owned by |user_policies|, so we do + // not use |sk_ASN1_OBJECT_pop_free|. + sk_ASN1_OBJECT_free(user_policies_sorted); + sk_X509_POLICY_LEVEL_pop_free(levels, x509_policy_level_free); + return ret; +}