/*

 * This file is part of PowerDNS or dnsdist.

 * Copyright -- PowerDNS.COM B.V. and its contributors

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of version 2 of the GNU General Public License as

 * published by the Free Software Foundation.

 *

 * In addition, for the avoidance of any doubt, permission is granted to

 * link this program with OpenSSL and to (re)distribute the binaries

 * produced as the result of such linking.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

 */

#pragma once

#include "config.h"

#include <memory>

#ifndef HAVE_DNSCRYPT

/* let's just define a few types and values so that the rest of

   the code can ignore whether DNSCrypt support is available */

#define DNSCRYPT_MAX_RESPONSE_PADDING_AND_MAC_SIZE (0)

class DNSCryptContext

{

};

class DNSCryptQuery

{

  DNSCryptQuery(const std::shared_ptr<DNSCryptContext>& ctx): d_ctx(ctx)

  {

  }

private:

  std::shared_ptr<DNSCryptContext> d_ctx{nullptr};

};

#else /* HAVE_DNSCRYPT */

#include <string>

#include <vector>

#include <arpa/inet.h>

#include <sodium.h>

#include "dnsname.hh"

#include "lock.hh"

#include "noinitvector.hh"

#define DNSCRYPT_PROVIDER_PUBLIC_KEY_SIZE (crypto_sign_ed25519_PUBLICKEYBYTES)

#define DNSCRYPT_PROVIDER_PRIVATE_KEY_SIZE (crypto_sign_ed25519_SECRETKEYBYTES)

#define DNSCRYPT_SIGNATURE_SIZE (crypto_sign_ed25519_BYTES)

#define DNSCRYPT_PUBLIC_KEY_SIZE (crypto_box_curve25519xsalsa20poly1305_PUBLICKEYBYTES)

#define DNSCRYPT_PRIVATE_KEY_SIZE (crypto_box_curve25519xsalsa20poly1305_SECRETKEYBYTES)

#define DNSCRYPT_NONCE_SIZE (crypto_box_curve25519xsalsa20poly1305_NONCEBYTES)

#define DNSCRYPT_BEFORENM_SIZE (crypto_box_curve25519xsalsa20poly1305_BEFORENMBYTES)

#define DNSCRYPT_MAC_SIZE (crypto_box_curve25519xsalsa20poly1305_MACBYTES)

#ifdef HAVE_CRYPTO_BOX_CURVE25519XCHACHA20POLY1305_EASY

static_assert(crypto_box_curve25519xsalsa20poly1305_PUBLICKEYBYTES == crypto_box_curve25519xchacha20poly1305_PUBLICKEYBYTES, "DNSCrypt public key size should be the same for all exchange versions");

static_assert(crypto_box_curve25519xsalsa20poly1305_SECRETKEYBYTES == crypto_box_curve25519xchacha20poly1305_SECRETKEYBYTES, "DNSCrypt private key size should be the same for all exchange versions");

static_assert(crypto_box_curve25519xchacha20poly1305_NONCEBYTES == crypto_box_curve25519xsalsa20poly1305_NONCEBYTES, "DNSCrypt nonce size should be the same for all exchange versions");

static_assert(crypto_box_curve25519xsalsa20poly1305_MACBYTES == crypto_box_curve25519xchacha20poly1305_MACBYTES, "DNSCrypt MAC size should be the same for all exchange versions");

static_assert(crypto_box_curve25519xchacha20poly1305_BEFORENMBYTES == crypto_box_curve25519xsalsa20poly1305_BEFORENMBYTES, "DNSCrypt BEFORENM size should be the same for all exchange versions");

#endif /* HAVE_CRYPTO_BOX_CURVE25519XCHACHA20POLY1305_EASY */

#define DNSCRYPT_CERT_MAGIC_SIZE (4)

#define DNSCRYPT_CERT_MAGIC_VALUE { 0x44, 0x4e, 0x53, 0x43 }

#define DNSCRYPT_CERT_PROTOCOL_MINOR_VERSION_VALUE { 0x00, 0x00 }

#define DNSCRYPT_CLIENT_MAGIC_SIZE (8)

#define DNSCRYPT_RESOLVER_MAGIC { 0x72, 0x36, 0x66, 0x6e, 0x76, 0x57, 0x6a, 0x38 }

#define DNSCRYPT_RESOLVER_MAGIC_SIZE (8)

#define DNSCRYPT_PADDED_BLOCK_SIZE (64)

#define DNSCRYPT_MAX_TCP_PADDING_SIZE (256)

#define DNSCRYPT_MAX_RESPONSE_PADDING_SIZE (256)

#define DNSCRYPT_MAX_RESPONSE_PADDING_AND_MAC_SIZE (DNSCRYPT_MAX_RESPONSE_PADDING_SIZE + DNSCRYPT_MAC_SIZE)

/* "The client must check for new certificates every hour", so let's use one hour TTL */

#define DNSCRYPT_CERTIFICATE_RESPONSE_TTL (3600)

static_assert(DNSCRYPT_CLIENT_MAGIC_SIZE <= DNSCRYPT_PUBLIC_KEY_SIZE, "DNSCrypt Client Nonce size should be smaller or equal to public key size.");

#define DNSCRYPT_CERT_ES_VERSION1_VALUE { 0x00, 0x01 }

#define DNSCRYPT_CERT_ES_VERSION2_VALUE { 0x00, 0x02 }

class DNSCryptContext;

struct DNSCryptCertSignedData

{

  unsigned char resolverPK[DNSCRYPT_PROVIDER_PUBLIC_KEY_SIZE];

  unsigned char clientMagic[DNSCRYPT_CLIENT_MAGIC_SIZE];

  uint32_t serial;

  uint32_t tsStart;

  uint32_t tsEnd;

};

class DNSCryptCert

{

public:

  uint32_t getSerial() const

  {

    return ntohl(signedData.serial);

  }

  uint32_t getTSStart() const

  {

    return signedData.tsStart;

  }

  uint32_t getTSEnd() const

  {

    return signedData.tsEnd;

  }

  bool isValid(time_t now) const

  {

    // coverity[store_truncates_time_t]

    return ntohl(getTSStart()) <= static_cast<uint32_t>(now) && static_cast<uint32_t>(now) <= ntohl(getTSEnd());

  }

  unsigned char magic[DNSCRYPT_CERT_MAGIC_SIZE];

  unsigned char esVersion[2];

  unsigned char protocolMinorVersion[2];

  unsigned char signature[DNSCRYPT_SIGNATURE_SIZE];

  struct DNSCryptCertSignedData signedData;

};

static_assert((sizeof(DNSCryptCertSignedData) + DNSCRYPT_SIGNATURE_SIZE) == 116, "Dnscrypt cert signed data size + signature size should be 116!");

static_assert(sizeof(DNSCryptCert) == 124, "Dnscrypt cert size should be 124!");

struct DNSCryptQueryHeader

{

  unsigned char clientMagic[DNSCRYPT_CLIENT_MAGIC_SIZE];

  unsigned char clientPK[DNSCRYPT_PUBLIC_KEY_SIZE];

  unsigned char clientNonce[DNSCRYPT_NONCE_SIZE / 2];

};

static_assert(sizeof(DNSCryptQueryHeader) == 52, "Dnscrypt query header size should be 52!");

struct DNSCryptResponseHeader

{

  const unsigned char resolverMagic[DNSCRYPT_RESOLVER_MAGIC_SIZE] = DNSCRYPT_RESOLVER_MAGIC;

  unsigned char nonce[DNSCRYPT_NONCE_SIZE];

};

typedef enum {

  VERSION1,

  VERSION2

} DNSCryptExchangeVersion;

class DNSCryptPrivateKey

{

public:

  DNSCryptPrivateKey();

  ~DNSCryptPrivateKey();

  void loadFromFile(const std::string& keyFile);

  void saveToFile(const std::string& keyFile) const;

  unsigned char key[DNSCRYPT_PRIVATE_KEY_SIZE];

};

struct DNSCryptCertificatePair

{

  unsigned char publicKey[DNSCRYPT_PUBLIC_KEY_SIZE];

  DNSCryptCert cert;

  DNSCryptPrivateKey privateKey;

  bool active;

};

class DNSCryptQuery

{

public:

  DNSCryptQuery(const std::shared_ptr<DNSCryptContext>& ctx): d_ctx(ctx)

  {

    memset(&d_header, 0, sizeof(d_header));

#ifdef HAVE_CRYPTO_BOX_EASY_AFTERNM

    memset(&d_sharedKey, 0, sizeof(d_sharedKey));

#endif /* HAVE_CRYPTO_BOX_EASY_AFTERNM */

  }

  ~DNSCryptQuery();

  bool isValid() const

  {

    return d_valid;

  }

  const DNSName& getQName() const

  {

    return d_qname;

  }

  uint16_t getID() const

  {

    return d_id;

  }

  const unsigned char* getClientMagic() const

  {

    return d_header.clientMagic;

  }

  bool isEncrypted() const

  {

    return d_encrypted;

  }

  void setCertificatePair(const std::shared_ptr<DNSCryptCertificatePair>& pair)

  {

    d_pair = pair;

  }

  void parsePacket(PacketBuffer& packet, bool tcp, time_t now);

  void getDecrypted(bool tcp, PacketBuffer& packet);

  void getCertificateResponse(time_t now, PacketBuffer& response) const;

  int encryptResponse(PacketBuffer& response, size_t maxResponseSize, bool tcp);

  static const size_t s_minUDPLength = 256;

private:

  DNSCryptExchangeVersion getVersion() const;

#ifdef HAVE_CRYPTO_BOX_EASY_AFTERNM

  int computeSharedKey();

#endif /* HAVE_CRYPTO_BOX_EASY_AFTERNM */

  void fillServerNonce(unsigned char* dest) const;

  uint16_t computePaddingSize(uint16_t unpaddedLen, size_t maxLen) const;

  bool parsePlaintextQuery(const PacketBuffer& packet);

  bool isEncryptedQuery(const PacketBuffer& packet, bool tcp, time_t now);

  DNSCryptQueryHeader d_header;

#ifdef HAVE_CRYPTO_BOX_EASY_AFTERNM

  unsigned char d_sharedKey[crypto_box_BEFORENMBYTES];

#endif /* HAVE_CRYPTO_BOX_EASY_AFTERNM */

  DNSName d_qname;

  std::shared_ptr<DNSCryptContext> d_ctx{nullptr};

  std::shared_ptr<DNSCryptCertificatePair> d_pair{nullptr};

  uint16_t d_id{0};

  uint16_t d_len{0};

  uint16_t d_paddedLen{0};

  bool d_encrypted{false};

  bool d_valid{false};

#ifdef HAVE_CRYPTO_BOX_EASY_AFTERNM

  bool d_sharedKeyComputed{false};

#endif /* HAVE_CRYPTO_BOX_EASY_AFTERNM */

};

class DNSCryptContext

{

public:

  static void generateProviderKeys(unsigned char publicKey[DNSCRYPT_PROVIDER_PUBLIC_KEY_SIZE], unsigned char privateKey[DNSCRYPT_PROVIDER_PRIVATE_KEY_SIZE]);

  static std::string getProviderFingerprint(unsigned char publicKey[DNSCRYPT_PROVIDER_PUBLIC_KEY_SIZE]);

  static void generateCertificate(uint32_t serial, time_t begin, time_t end, const DNSCryptExchangeVersion& version, const unsigned char providerPrivateKey[DNSCRYPT_PROVIDER_PRIVATE_KEY_SIZE], DNSCryptPrivateKey& privateKey, DNSCryptCert& cert);

  static void saveCertFromFile(const DNSCryptCert& cert, const std::string&filename);

  static std::string certificateDateToStr(uint32_t date);

  static void generateResolverKeyPair(DNSCryptPrivateKey& privK, unsigned char pubK[DNSCRYPT_PUBLIC_KEY_SIZE]);

  static void setExchangeVersion(const DNSCryptExchangeVersion& version,  unsigned char esVersion[sizeof(DNSCryptCert::esVersion)]);

  static DNSCryptExchangeVersion getExchangeVersion(const unsigned char esVersion[sizeof(DNSCryptCert::esVersion)]);

  static DNSCryptExchangeVersion getExchangeVersion(const DNSCryptCert& cert);

  struct CertKeyPaths

  {

    std::string cert;

    std::string key;

  };

  DNSCryptContext(const std::string& pName, const std::vector<CertKeyPaths>& certKeys);

  DNSCryptContext(const std::string& pName, const DNSCryptCert& certificate, const DNSCryptPrivateKey& pKey);

  ~DNSCryptContext();

  void reloadCertificates();

  void loadNewCertificate(const std::string& certFile, const std::string& keyFile, bool active=true, bool reload=false);

  void addNewCertificate(const DNSCryptCert& newCert, const DNSCryptPrivateKey& newKey, bool active=true, bool reload=false);

  void markActive(uint32_t serial);

  void markInactive(uint32_t serial);

  void removeInactiveCertificate(uint32_t serial);

  std::vector<std::shared_ptr<DNSCryptCertificatePair>> getCertificates();

  const DNSName& getProviderName() const { return providerName; }

  int encryptQuery(PacketBuffer& query, size_t maximumSize, const unsigned char clientPublicKey[DNSCRYPT_PUBLIC_KEY_SIZE], const DNSCryptPrivateKey& clientPrivateKey, const unsigned char clientNonce[DNSCRYPT_NONCE_SIZE / 2], bool tcp, const std::shared_ptr<DNSCryptCert>& cert) const;

  bool magicMatchesAPublicKey(DNSCryptQuery& query, time_t now);

  void getCertificateResponse(time_t now, const DNSName& qname, uint16_t qid, PacketBuffer& response);

private:

  static void computePublicKeyFromPrivate(const DNSCryptPrivateKey& privK, unsigned char pubK[DNSCRYPT_PUBLIC_KEY_SIZE]);

  static void loadCertFromFile(const std::string&filename, DNSCryptCert& dest);

  static std::shared_ptr<DNSCryptCertificatePair> loadCertificatePair(const std::string& certFile, const std::string& keyFile);

  void addNewCertificate(std::shared_ptr<DNSCryptCertificatePair>& newCert, bool reload=false);

  SharedLockGuarded<std::vector<std::shared_ptr<DNSCryptCertificatePair>>> d_certs;

  SharedLockGuarded<std::vector<CertKeyPaths>> d_certKeyPaths;

  DNSName providerName;

};

bool generateDNSCryptCertificate(const std::string& providerPrivateKeyFile, uint32_t serial, time_t begin, time_t end, DNSCryptExchangeVersion version, DNSCryptCert& certOut, DNSCryptPrivateKey& keyOut);

#endif