// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef NET_SSL_SSL_CONFIG_SERVICE_H_
#define NET_SSL_SSL_CONFIG_SERVICE_H_

#include <optional>
#include <string_view>
#include <vector>

#include "base/observer_list.h"
#include "net/base/net_export.h"
#include "net/ssl/ssl_config.h"
#include "third_party/abseil-cpp/absl/container/flat_hash_set.h"

namespace net {

// Represents a given named group in TLS, used in supported_groups and
// key_share.
struct NET_EXPORT SSLNamedGroupInfo {
  // NamedGroup enum codepoint for the group, from
  // https://datatracker.ietf.org/doc/html/rfc8446#section-4.2.7.
  uint16_t group_id = 0u;
  // Whether the group should be sent in the key_share extension for the
  // initial ClientHello.
  bool send_key_share = false;

  bool operator==(const SSLNamedGroupInfo&) const = default;

  bool IsPostQuantum() const;
};

// Configuration options for SSL connections.
struct NET_EXPORT SSLContextConfig {
  SSLContextConfig();
  SSLContextConfig(const SSLContextConfig&);
  SSLContextConfig(SSLContextConfig&&);
  ~SSLContextConfig();
  SSLContextConfig& operator=(const SSLContextConfig&);
  SSLContextConfig& operator=(SSLContextConfig&&);

  bool operator==(const SSLContextConfig&) const;

  // Returns a copy of the list of group IDs given by `supported_named_groups`.
  // If `key_shares_only` is false, the returned vector is the list of groups to
  // include in the supported_groups extension. If `key_shares_only` is true,
  // only the groups that have `send_key_share == true` are included in the
  // returned vector, which will be the list of groups to include in the
  // key_share extension.
  std::vector<uint16_t> GetSupportedGroups(bool key_shares_only = false) const;

  // Helper function to select TLS Trust Anchor IDs to advertise in the TLS
  // handshake, so that the server can serve a certificate that the client
  // trusts. `server_advertised_trust_anchor_ids` is a list of Trust Anchor IDs,
  // in binary representation, that the server has provided out-of-band (e.g. in
  // a DNS record). The intersection with `trust_anchor_ids` is returned in wire
  // format (a series of 8-bit length prefixed non-empty strings) such that it
  // can be passed into BoringSSL.
  std::vector<uint8_t> SelectTrustAnchorIDs(
      const std::vector<std::vector<uint8_t>>&
          server_advertised_trust_anchor_ids) const;

  // The minimum and maximum protocol versions that are enabled.
  // (Use the SSL_PROTOCOL_VERSION_xxx enumerators defined in ssl_config.h.)
  // SSL 2.0/3.0 and TLS 1.0/1.1 are not supported. If version_max <
  // version_min, it means no protocol versions are enabled.
  uint16_t version_min = kDefaultSSLVersionMin;
  uint16_t version_max = kDefaultSSLVersionMax;

  // A list of cipher suites which should be explicitly prevented from being
  // used in addition to those disabled by the net built-in policy.
  //
  // Though cipher suites are sent in TLS as "uint8_t CipherSuite[2]", in
  // big-endian form, they should be declared in host byte order, with the
  // first uint8_t occupying the most significant byte.
  // Ex: To disable TLS_RSA_WITH_RC4_128_MD5, specify 0x0004, while to
  // disable TLS_ECDH_ECDSA_WITH_RC4_128_SHA, specify 0xC002.
  std::vector<uint16_t> disabled_cipher_suites;

  // This configures a compliance policy that sets the cipher order for
  // TLS 1.3 to prefer AES-256-GCM over AES-128-GCM over ChaCha20-Poly1305.
  bool tls13_cipher_prefer_aes_256 = false;

  // Ordered list of NamedGroups that are supported, used to configure
  // supported_groups and key_share. Set to `kDefaultSSLSupportedGroups` by
  // default.
  std::vector<SSLNamedGroupInfo> supported_named_groups;

  // Controls whether ECH is enabled.
  bool ech_enabled = true;

  // TLS Trust Anchor IDs that are configured as trusted, as a list of Trust
  // Anchor IDs in binary representation.
  absl::flat_hash_set<std::vector<uint8_t>> trust_anchor_ids;

  // MTC TLS Trust Anchor IDs that are configured as trusted, as a list of
  // Trust Anchor IDs in binary representation.
  std::vector<std::vector<uint8_t>> mtc_trust_anchor_ids;
};

// The interface for retrieving global SSL configuration.  This interface
// does not cover setting the SSL configuration, as on some systems, the
// SSLConfigService objects may not have direct access to the configuration, or
// live longer than the configuration preferences.
class NET_EXPORT SSLConfigService {
 public:
  // Observer is notified when SSL config settings have changed.
  class NET_EXPORT Observer {
   public:
    // Notify observers if SSL settings have changed.
    virtual void OnSSLContextConfigChanged() = 0;

   protected:
    virtual ~Observer() = default;
  };

  SSLConfigService();
  virtual ~SSLConfigService();

  // May not be thread-safe, should only be called on the IO thread.
  virtual SSLContextConfig GetSSLContextConfig() = 0;

  // Returns true if connections to |hostname| can reuse, or are permitted to
  // reuse, connections on which a client cert has been negotiated. Note that
  // this must return true for both hostnames being pooled - that is to say this
  // function must return true for both the hostname of the existing connection
  // and the potential hostname to pool before allowing the connection to be
  // reused.
  //
  // NOTE: Pooling connections with ambient authority can create security issues
  // with that ambient authority and privacy issues in that embedders (and
  // users) may not have been consulted to send a client cert to |hostname|.
  // Implementations of this method should only return true if they have
  // received affirmative consent (e.g. through preferences or Enterprise
  // policy).
  //
  // NOTE: For Web Platform clients, this violates the Fetch Standard's policies
  // around connection pools: https://fetch.spec.whatwg.org/#connections.
  // Implementations that return true should take steps to limit the Web
  // Platform visibility of this, such as only allowing it to be used for
  // Enterprise or internal configurations.
  //
  // DEPRECATED: For the reasons above, this method is temporary and will be
  // removed in a future release. Please leave a comment on
  // https://crbug.com/855690 if you believe this is needed.
  virtual bool CanShareConnectionWithClientCerts(
      std::string_view hostname) const = 0;

  // Add an observer of this service.
  void AddObserver(Observer* observer);

  // Remove an observer of this service.
  void RemoveObserver(Observer* observer);

  // Calls the OnSSLContextConfigChanged method of registered observers. Should
  // only be called on the IO thread.
  void NotifySSLContextConfigChange();

 protected:
  // Process before/after config update. If |force_notification| is true,
  // NotifySSLContextConfigChange will be called regardless of whether
  // |orig_config| and |new_config| are equal.
  void ProcessConfigUpdate(const SSLContextConfig& orig_config,
                           const SSLContextConfig& new_config,
                           bool force_notification);

 private:
  base::ObserverList<Observer>::Unchecked observer_list_;
};

}  // namespace net

#endif  // NET_SSL_SSL_CONFIG_SERVICE_H_