policy.c | Explore in Territory

/* 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 <openssl/x509.h>

#include <assert.h>

#include <openssl/mem.h>
#include <openssl/obj.h>
#include <openssl/stack.h>

#include "../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.
X509_POLICY_NODE;

DEFINE_STACK_OF(…)

// 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|.
X509_POLICY_LEVEL;

DEFINE_STACK_OF(…)

static int is_any_policy(const ASN1_OBJECT *obj) { … }

static void x509_policy_node_free(X509_POLICY_NODE *node) { … }

static X509_POLICY_NODE *x509_policy_node_new(const ASN1_OBJECT *policy) { … }

static int x509_policy_node_cmp(const X509_POLICY_NODE *const *a,
                                const X509_POLICY_NODE *const *b) { … }

static void x509_policy_level_free(X509_POLICY_LEVEL *level) { … }

static X509_POLICY_LEVEL *x509_policy_level_new(void) { … }

static int x509_policy_level_is_empty(const X509_POLICY_LEVEL *level) { … }

static void x509_policy_level_clear(X509_POLICY_LEVEL *level) { … }

// 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) { … }

// 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) { … }

static int policyinfo_cmp(const POLICYINFO *const *a,
                          const POLICYINFO *const *b) { … }

static int delete_if_not_in_policies(X509_POLICY_NODE *node, void *data) { … }

// 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) { … }

static int compare_issuer_policy(const POLICY_MAPPING *const *a,
                                 const POLICY_MAPPING *const *b) { … }

static int compare_subject_policy(const POLICY_MAPPING *const *a,
                                  const POLICY_MAPPING *const *b) { … }

static int delete_if_mapped(X509_POLICY_NODE *node, void *data) { … }

// 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) { … }

// 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) { … }

// 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) { … }

// 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) { … }

static int asn1_object_cmp(const ASN1_OBJECT *const *a,
                           const ASN1_OBJECT *const *b) { … }

int X509_policy_check(const STACK_OF(X509) *certs,
                      const STACK_OF(ASN1_OBJECT) *user_policies,
                      unsigned long flags, X509 **out_current_cert) { … }
chromium/third_party/boringssl/src/crypto/x509/policy.c
