/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this file,
 * You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef tls_filter_h_
#define tls_filter_h_

#include <functional>
#include <memory>
#include <set>
#include <vector>

#include "test_io.h"
#include "tls_parser.h"
#include "tls_protect.h"

extern "C" {
#include "libssl_internals.h"
}

namespace nss_test {

class TlsCipherSpec;
class TlsAgent;

class TlsVersioned {
 public:
  TlsVersioned() : version_(0) {}
  explicit TlsVersioned(uint16_t version) : version_(version) {}

  bool is_dtls() const { return IsDtls(version_); }
  uint16_t version() const { return version_; }

  void WriteStream(std::ostream& stream) const;

 protected:
  uint16_t version_;
};

class TlsRecordHeader : public TlsVersioned {
 public:
  TlsRecordHeader() : TlsVersioned(), content_type_(0), sequence_number_(0) {}
  TlsRecordHeader(uint16_t version, uint8_t content_type,
                  uint64_t sequence_number)
      : TlsVersioned(version),
        content_type_(content_type),
        sequence_number_(sequence_number) {}

  uint8_t content_type() const { return content_type_; }
  uint64_t sequence_number() const { return sequence_number_; }
  size_t header_length() const { return is_dtls() ? 11 : 3; }

  // Parse the header; return true if successful; body in an outparam if OK.
  bool Parse(TlsParser* parser, DataBuffer* body);
  // Write the header and body to a buffer at the given offset.
  // Return the offset of the end of the write.
  size_t Write(DataBuffer* buffer, size_t offset, const DataBuffer& body) const;

 private:
  uint8_t content_type_;
  uint64_t sequence_number_;
};

// Abstract filter that operates on entire (D)TLS records.
class TlsRecordFilter : public PacketFilter {
 public:
  TlsRecordFilter() : agent_(nullptr), count_(0), cipher_spec_() {}

  void SetAgent(const TlsAgent* agent) { agent_ = agent; }
  const TlsAgent* agent() const { return agent_; }

  // External interface. Overrides PacketFilter.
  PacketFilter::Action Filter(const DataBuffer& input, DataBuffer* output);

  // Report how many packets were altered by the filter.
  size_t filtered_packets() const { return count_; }

  // Enable decryption. This only works properly for TLS 1.3 and above.
  // Enabling it for lower version tests will cause undefined
  // behavior.
  void EnableDecryption();
  bool Unprotect(const TlsRecordHeader& header, const DataBuffer& cipherText,
                 uint8_t* inner_content_type, DataBuffer* plaintext);
  bool Protect(const TlsRecordHeader& header, uint8_t inner_content_type,
               const DataBuffer& plaintext, DataBuffer* ciphertext);

 protected:
  // There are two filter functions which can be overriden. Both are
  // called with the header and the record but the outer one is called
  // with a raw pointer to let you write into the buffer and lets you
  // do anything with this section of the stream. The inner one
  // just lets you change the record contents. By default, the
  // outer one calls the inner one, so if you override the outer
  // one, the inner one is never called unless you call it yourself.
  virtual PacketFilter::Action FilterRecord(const TlsRecordHeader& header,
                                            const DataBuffer& record,
                                            size_t* offset, DataBuffer* output);

  // The record filter receives the record contentType, version and DTLS
  // sequence number (which is zero for TLS), plus the existing record payload.
  // It returns an action (KEEP, CHANGE, DROP).  It writes to the `changed`
  // outparam with the new record contents if it chooses to CHANGE the record.
  virtual PacketFilter::Action FilterRecord(const TlsRecordHeader& header,
                                            const DataBuffer& data,
                                            DataBuffer* changed) {
    return KEEP;
  }

 private:
  static void CipherSpecChanged(void* arg, PRBool sending,
                                ssl3CipherSpec* newSpec);

  const TlsAgent* agent_;
  size_t count_;
  std::unique_ptr<TlsCipherSpec> cipher_spec_;
};

inline std::ostream& operator<<(std::ostream& stream, TlsVersioned v) {
  v.WriteStream(stream);
  return stream;
}

inline std::ostream& operator<<(std::ostream& stream, TlsRecordHeader& hdr) {
  hdr.WriteStream(stream);
  stream << ' ';
  switch (hdr.content_type()) {
    case kTlsChangeCipherSpecType:
      stream << "CCS";
      break;
    case kTlsAlertType:
      stream << "Alert";
      break;
    case kTlsHandshakeType:
      stream << "Handshake";
      break;
    case kTlsApplicationDataType:
      stream << "Data";
      break;
    default:
      stream << '<' << hdr.content_type() << '>';
      break;
  }
  return stream << ' ' << std::hex << hdr.sequence_number() << std::dec;
}

// Abstract filter that operates on handshake messages rather than records.
// This assumes that the handshake messages are written in a block as entire
// records and that they don't span records or anything crazy like that.
class TlsHandshakeFilter : public TlsRecordFilter {
 public:
  TlsHandshakeFilter() {}

  class HandshakeHeader : public TlsVersioned {
   public:
    HandshakeHeader() : TlsVersioned(), handshake_type_(0), message_seq_(0) {}

    uint8_t handshake_type() const { return handshake_type_; }
    bool Parse(TlsParser* parser, const TlsRecordHeader& record_header,
               DataBuffer* body);
    size_t Write(DataBuffer* buffer, size_t offset,
                 const DataBuffer& body) const;
    size_t WriteFragment(DataBuffer* buffer, size_t offset,
                         const DataBuffer& body, size_t fragment_offset,
                         size_t fragment_length) const;

   private:
    // Reads the length from the record header.
    // This also reads the DTLS fragment information and checks it.
    bool ReadLength(TlsParser* parser, const TlsRecordHeader& header,
                    uint32_t* length);

    uint8_t handshake_type_;
    uint16_t message_seq_;
    // fragment_offset is always zero in these tests.
  };

 protected:
  virtual PacketFilter::Action FilterRecord(const TlsRecordHeader& header,
                                            const DataBuffer& input,
                                            DataBuffer* output);
  virtual PacketFilter::Action FilterHandshake(const HandshakeHeader& header,
                                               const DataBuffer& input,
                                               DataBuffer* output) = 0;

 private:
};

// Make a copy of the first instance of a handshake message.
class TlsInspectorRecordHandshakeMessage : public TlsHandshakeFilter {
 public:
  TlsInspectorRecordHandshakeMessage(uint8_t handshake_type)
      : handshake_type_(handshake_type), buffer_() {}

  virtual PacketFilter::Action FilterHandshake(const HandshakeHeader& header,
                                               const DataBuffer& input,
                                               DataBuffer* output);

  const DataBuffer& buffer() const { return buffer_; }

 private:
  uint8_t handshake_type_;
  DataBuffer buffer_;
};

// Replace all instances of a handshake message.
class TlsInspectorReplaceHandshakeMessage : public TlsHandshakeFilter {
 public:
  TlsInspectorReplaceHandshakeMessage(uint8_t handshake_type,
                                      const DataBuffer& replacement)
      : handshake_type_(handshake_type), buffer_(replacement) {}

  virtual PacketFilter::Action FilterHandshake(const HandshakeHeader& header,
                                               const DataBuffer& input,
                                               DataBuffer* output);

 private:
  uint8_t handshake_type_;
  DataBuffer buffer_;
};

// Make a copy of the complete conversation.
class TlsConversationRecorder : public TlsRecordFilter {
 public:
  TlsConversationRecorder(DataBuffer& buffer) : buffer_(buffer) {}

  virtual PacketFilter::Action FilterRecord(const TlsRecordHeader& header,
                                            const DataBuffer& input,
                                            DataBuffer* output);

 private:
  DataBuffer& buffer_;
};

// Runs multiple packet filters in series.
class ChainedPacketFilter : public PacketFilter {
 public:
  ChainedPacketFilter() {}
  ChainedPacketFilter(const std::vector<std::shared_ptr<PacketFilter>> filters)
      : filters_(filters.begin(), filters.end()) {}
  virtual ~ChainedPacketFilter() {}

  virtual PacketFilter::Action Filter(const DataBuffer& input,
                                      DataBuffer* output);

  // Takes ownership of the filter.
  void Add(std::shared_ptr<PacketFilter> filter) { filters_.push_back(filter); }

 private:
  std::vector<std::shared_ptr<PacketFilter>> filters_;
};

typedef std::function<bool(TlsParser* parser, const TlsVersioned& header)>
    TlsExtensionFinder;

class TlsExtensionFilter : public TlsHandshakeFilter {
 public:
  TlsExtensionFilter() : handshake_types_() {
    handshake_types_.insert(kTlsHandshakeClientHello);
    handshake_types_.insert(kTlsHandshakeServerHello);
  }

  TlsExtensionFilter(const std::set<uint8_t>& types)
      : handshake_types_(types) {}

  static bool FindExtensions(TlsParser* parser, const HandshakeHeader& header);

 protected:
  PacketFilter::Action FilterHandshake(const HandshakeHeader& header,
                                       const DataBuffer& input,
                                       DataBuffer* output) override;

  virtual PacketFilter::Action FilterExtension(uint16_t extension_type,
                                               const DataBuffer& input,
                                               DataBuffer* output) = 0;

 private:
  PacketFilter::Action FilterExtensions(TlsParser* parser,
                                        const DataBuffer& input,
                                        DataBuffer* output);

  std::set<uint8_t> handshake_types_;
};

class TlsExtensionCapture : public TlsExtensionFilter {
 public:
  TlsExtensionCapture(uint16_t ext, bool last = false)
      : extension_(ext), captured_(false), last_(last), data_() {}

  const DataBuffer& extension() const { return data_; }
  bool captured() const { return captured_; }

 protected:
  PacketFilter::Action FilterExtension(uint16_t extension_type,
                                       const DataBuffer& input,
                                       DataBuffer* output) override;

 private:
  const uint16_t extension_;
  bool captured_;
  bool last_;
  DataBuffer data_;
};

class TlsExtensionReplacer : public TlsExtensionFilter {
 public:
  TlsExtensionReplacer(uint16_t extension, const DataBuffer& data)
      : extension_(extension), data_(data) {}
  PacketFilter::Action FilterExtension(uint16_t extension_type,
                                       const DataBuffer& input,
                                       DataBuffer* output) override;

 private:
  const uint16_t extension_;
  const DataBuffer data_;
};

class TlsExtensionDropper : public TlsExtensionFilter {
 public:
  TlsExtensionDropper(uint16_t extension) : extension_(extension) {}
  PacketFilter::Action FilterExtension(uint16_t extension_type,
                                       const DataBuffer&, DataBuffer*) override;

 private:
  uint16_t extension_;
};

class TlsAgent;
typedef std::function<void(void)> VoidFunction;

class AfterRecordN : public TlsRecordFilter {
 public:
  AfterRecordN(std::shared_ptr<TlsAgent>& src, std::shared_ptr<TlsAgent>& dest,
               unsigned int record, VoidFunction func)
      : src_(src), dest_(dest), record_(record), func_(func), counter_(0) {}

  virtual PacketFilter::Action FilterRecord(const TlsRecordHeader& header,
                                            const DataBuffer& body,
                                            DataBuffer* out) override;

 private:
  std::weak_ptr<TlsAgent> src_;
  std::weak_ptr<TlsAgent> dest_;
  unsigned int record_;
  VoidFunction func_;
  unsigned int counter_;
};

// When we see the ClientKeyExchange from |client|, increment the
// ClientHelloVersion on |server|.
class TlsInspectorClientHelloVersionChanger : public TlsHandshakeFilter {
 public:
  TlsInspectorClientHelloVersionChanger(std::shared_ptr<TlsAgent>& server)
      : server_(server) {}

  virtual PacketFilter::Action FilterHandshake(const HandshakeHeader& header,
                                               const DataBuffer& input,
                                               DataBuffer* output);

 private:
  std::weak_ptr<TlsAgent> server_;
};

// This class selectively drops complete writes.  This relies on the fact that
// writes in libssl are on record boundaries.
class SelectiveDropFilter : public PacketFilter {
 public:
  SelectiveDropFilter(uint32_t pattern) : pattern_(pattern), counter_(0) {}

 protected:
  virtual PacketFilter::Action Filter(const DataBuffer& input,
                                      DataBuffer* output) override;

 private:
  const uint32_t pattern_;
  uint8_t counter_;
};

// Set the version number in the ClientHello.
class TlsInspectorClientHelloVersionSetter : public TlsHandshakeFilter {
 public:
  TlsInspectorClientHelloVersionSetter(uint16_t version) : version_(version) {}

  virtual PacketFilter::Action FilterHandshake(const HandshakeHeader& header,
                                               const DataBuffer& input,
                                               DataBuffer* output);

 private:
  uint16_t version_;
};

// Damages the last byte of a handshake message.
class TlsLastByteDamager : public TlsHandshakeFilter {
 public:
  TlsLastByteDamager(uint8_t type) : type_(type) {}
  PacketFilter::Action FilterHandshake(
      const TlsHandshakeFilter::HandshakeHeader& header,
      const DataBuffer& input, DataBuffer* output) override {
    if (header.handshake_type() != type_) {
      return KEEP;
    }

    *output = input;

    output->data()[output->len() - 1]++;
    return CHANGE;
  }

 private:
  uint8_t type_;
};

}  // namespace nss_test

#endif