Certificate path builder for new certificate verification library

net/cert/internal/path_builder.h

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef NET_CERT_INTERNAL_PATH_BUILDER_H_
+#define NET_CERT_INTERNAL_PATH_BUILDER_H_
+
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "base/callback.h"
+#include "net/base/completion_callback.h"
+#include "net/base/net_errors.h"
+#include "net/base/net_export.h"
+#include "net/cert/internal/completion_status.h"
+#include "net/cert/internal/parsed_certificate.h"
+#include "net/der/input.h"
+#include "net/der/parse_values.h"
+
+namespace net {
+
+namespace der {
+struct GeneralizedTime;
+}
+
+class CertPathIter;
+class CertIssuerSource;
+class TrustStore;
+class SignaturePolicy;
+
+// Checks whether a certificate is trusted by building candidate paths to trust
+// anchors and verifying those paths according to RFC 5280. Each instance of
+// CertPathBuilder is used for a single verification.
+//
+// WARNING: This implementation is currently experimental.  Consult an OWNER
+// before using it.
+class NET_EXPORT CertPathBuilder {
+ public:
+  // Represents a single candidate path that was built.
+  struct NET_EXPORT ResultPath {
+    ResultPath();
+    ~ResultPath();
+
+    // Returns true if this path was successfully verified.
+    bool is_success() const { return error == OK; }
+
+    // The candidate path, in forward direction.
+    //   * path[0] is the target certificate.
+    //   * path[i+1] is a candidate issuer of path[i]. The subject matches
+    //   path[i]'s issuer, but nothing else is guaranteed unless is_success() is
+    //   true.
+    //   * path[N-1] will be a trust anchor if is_success() is true, otherwise
+    //   it may or may not be a trust anchor.
+    ParsedCertificateList path;
+
+    // A net error code result of attempting to verify this path.
+    // TODO(mattm): may want to have an independent result enum, which caller
+    // can map to a net error if they want.
+    int error = ERR_UNEXPECTED;
+  };
+
+  // Provides the overall result of path building. This includes the paths that
+  // were attempted.
+  struct NET_EXPORT Result {
+    Result();
+    ~Result();
+
+    // Returns true if there was a valid path.
+    bool is_success() const { return error() == OK; }
+
+    // Returns the net error code of the overall best result.
+    int error() const {
+      if (paths.empty())
+        return ERR_CERT_AUTHORITY_INVALID;
+      return paths[best_result_index]->error;
+    }
+
+    // List of paths that were attempted and the result for each.
+    std::vector<std::unique_ptr<ResultPath>> paths;
+
+    // Index into |paths|. Before use, |paths.empty()| must be checked.
+    // NOTE: currently the definition of "best" is fairly limited. Successful is
+    // better than unsuccessful, but otherwise nothing is guaranteed.
+    size_t best_result_index = 0;
+
+   private:
+    DISALLOW_COPY_AND_ASSIGN(Result);
+  };
+
+  // TODO(mattm): allow caller specified hook/callback to extend path
+  // verification.
+  //
+  // Creates a CertPathBuilder that attempts to find a path from |cert| to a
+  // trust anchor in |trust_store|, which satisfies |signature_policy| and is
+  // valid at |time|.  Details of attempted path(s) are stored in |*result|.
+  //
+  // The caller must keep |trust_store|, |signature_policy|, and |*result| valid
+  // for the lifetime of the CertPathBuilder.
+  CertPathBuilder(scoped_refptr<ParsedCertificate> cert,
+                  const TrustStore* trust_store,
+                  const SignaturePolicy* signature_policy,
+                  const der::GeneralizedTime& time,
+                  Result* result);
+  ~CertPathBuilder();
+
+  // Adds a CertIssuerSource to provide intermediates for use in path building.
+  // Multiple sources may be added. Must not be called after Run is called.
+  // The |*cert_issuer_source| must remain valid for the lifetime of the
+  // CertPathBuilder.
+  //
+  // (If no issuer sources are added, the target certificate will only verify if
+  // it is a trust anchor or is directly signed by a trust anchor.)
+  void AddCertIssuerSource(CertIssuerSource* cert_issuer_source);
+
+  // Begins verification of the target certificate.
+  //
+  // If the return value is SYNC then the verification is complete and the
+  // |result| value can be inspected for the status, and |callback| will not be
+  // called.
+  // If the return value is ASYNC, the |callback| will be called asynchronously
+  // once the verification is complete. |result| should not be examined or
+  // modified until the |callback| is run.
+  //
+  // If |callback| is null, verification always completes synchronously, even if
+  // it fails to find a valid path and one could have been found asynchronously.
+  //
+  // The CertPathBuilder may be deleted while an ASYNC verification is pending,
+  // in which case the verification is cancelled, |callback| will not be called,
+  // and the output Result will be in an undefined state.
+  // It is safe to delete the CertPathBuilder during the |callback|.
+  // Run must not be called more than once on each CertPathBuilder instance.
+  CompletionStatus Run(const base::Closure& callback);
+
+ private:
+  enum State {
+    STATE_NONE,
+    STATE_GET_NEXT_PATH,
+    STATE_GET_NEXT_PATH_COMPLETE,
+  };
+
+  CompletionStatus DoLoop(bool allow_async);
+
+  CompletionStatus DoGetNextPath(bool allow_async);
+  void HandleGotNextPath();
+  CompletionStatus DoGetNextPathComplete();
+
+  void AddResultPath(const ParsedCertificateList& path, bool is_success);
+
+  base::Closure callback_;
+
+  std::unique_ptr<CertPathIter> cert_path_iter_;
+  const TrustStore* trust_store_;
+  const SignaturePolicy* signature_policy_;
+  const der::GeneralizedTime time_;
+
+  // Stores the next complete path to attempt verification on. This is filled in
+  // by |cert_path_iter_| during the STATE_GET_NEXT_PATH step, and thus should
+  // only be accessed during the STATE_GET_NEXT_PATH_COMPLETE step.
+  // (Will be empty if all paths have been tried, otherwise will be a candidate
+  // path starting with the target cert and ending with a trust anchor.)
+  ParsedCertificateList next_path_;
+  State next_state_;
+
+  Result* out_result_;
+
+  DISALLOW_COPY_AND_ASSIGN(CertPathBuilder);
+};
+
+}  // namespace net
+
+#endif  // NET_CERT_INTERNAL_PATH_BUILDER_H_