text: #ifndef TLSE_H
  #define TLSE_H
  
  // #define DEBUG
  
  // define TLS_LEGACY_SUPPORT to support TLS 1.1/1.0 (legacy)
  // legacy support it will use an additional 272 bytes / context
  #ifndef NO_TLS_LEGACY_SUPPORT
  #define TLS_LEGACY_SUPPORT
  #endif
  // SSL_* style blocking APIs
  #ifndef NO_SSL_COMPATIBLE_INTERFACE
  #define SSL_COMPATIBLE_INTERFACE
  #endif
  // support ChaCha20/Poly1305
  #if !defined(__BIG_ENDIAN__) && ((!defined(__BYTE_ORDER)) || (__BYTE_ORDER == __LITTLE_ENDIAN))
      // not working on big endian machines
      #ifndef NO_TLS_WITH_CHACHA20_POLY1305
          #define TLS_WITH_CHACHA20_POLY1305
      #endif
  #endif
  #ifndef NO_TLS_13
  #define WITH_TLS_13
  #endif
  // support forward secrecy (Diffie-Hellman ephemeral)
  #ifndef NO_TLS_FORWARD_SECRECY
  #define TLS_FORWARD_SECRECY
  #endif
  // support client-side ECDHE
  #ifndef NO_TLS_CLIENT_ECDHE
  #define TLS_CLIENT_ECDHE
  #endif
  // suport ecdsa
  #ifndef NO_TLS_ECDSA_SUPPORTED
  #define TLS_ECDSA_SUPPORTED
  #endif
  // suport ecdsa client-side
  // #define TLS_CLIENT_ECDSA
  // TLS renegotiation is disabled by default (secured or not)
  // do not uncomment next line!
  // #define TLS_ACCEPT_SECURE_RENEGOTIATION
  // basic superficial X509v1 certificate support
  #ifndef NO_TLS_X509_V1_SUPPORT
  #define TLS_X509_V1_SUPPORT
  #endif
  
  // disable TLS_RSA_WITH_* ciphers
  #ifndef NO_TLS_ROBOT_MITIGATION
  #define TLS_ROBOT_MITIGATION
  #endif
  
  #define SSL_V30                 0x0300
  #define TLS_V10                 0x0301
  #define TLS_V11                 0x0302
  #define TLS_V12                 0x0303
  #define TLS_V13                 0x0304
  #define DTLS_V10                0xFEFF
  #define DTLS_V12                0xFEFD
  #define DTLS_V13                0xFEFC
  
  #define TLS_NEED_MORE_DATA       0
  #define TLS_GENERIC_ERROR       -1
  #define TLS_BROKEN_PACKET       -2
  #define TLS_NOT_UNDERSTOOD      -3
  #define TLS_NOT_SAFE            -4
  #define TLS_NO_COMMON_CIPHER    -5
  #define TLS_UNEXPECTED_MESSAGE  -6
  #define TLS_CLOSE_CONNECTION    -7
  #define TLS_COMPRESSION_NOT_SUPPORTED -8
  #define TLS_NO_MEMORY           -9
  #define TLS_NOT_VERIFIED        -10
  #define TLS_INTEGRITY_FAILED    -11
  #define TLS_ERROR_ALERT         -12
  #define TLS_BROKEN_CONNECTION   -13
  #define TLS_BAD_CERTIFICATE     -14
  #define TLS_UNSUPPORTED_CERTIFICATE -15
  #define TLS_NO_RENEGOTIATION    -16
  #define TLS_FEATURE_NOT_SUPPORTED   -17
  #define TLS_DECRYPTION_FAILED   -20
  
  #define TLS_AES_128_GCM_SHA256                0x1301
  #define TLS_AES_256_GCM_SHA384                0x1302
  #define TLS_CHACHA20_POLY1305_SHA256          0x1303
  #define TLS_AES_128_CCM_SHA256                0x1304
  #define TLS_AES_128_CCM_8_SHA256              0x1305
  
  #define TLS_RSA_WITH_AES_128_CBC_SHA          0x002F
  #define TLS_RSA_WITH_AES_256_CBC_SHA          0x0035
  #define TLS_RSA_WITH_AES_128_CBC_SHA256       0x003C
  #define TLS_RSA_WITH_AES_256_CBC_SHA256       0x003D
  #define TLS_RSA_WITH_AES_128_GCM_SHA256       0x009C
  #define TLS_RSA_WITH_AES_256_GCM_SHA384       0x009D
  
  // forward secrecy
  #define TLS_DHE_RSA_WITH_AES_128_CBC_SHA      0x0033
  #define TLS_DHE_RSA_WITH_AES_256_CBC_SHA      0x0039
  #define TLS_DHE_RSA_WITH_AES_128_CBC_SHA256   0x0067
  #define TLS_DHE_RSA_WITH_AES_256_CBC_SHA256   0x006B
  #define TLS_DHE_RSA_WITH_AES_128_GCM_SHA256   0x009E
  #define TLS_DHE_RSA_WITH_AES_256_GCM_SHA384   0x009F
  
  #define TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA    0xC013
  #define TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA    0xC014
  #define TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256 0xC027
  #define TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 0xC02F
  #define TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 0xC030
  
  #define TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA    0xC009
  #define TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA    0xC00A
  #define TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256 0xC023
  #define TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384 0xC024
  #define TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 0xC02B
  #define TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 0xC02C
  
  #define TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256     0xCCA8
  #define TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256   0xCCA9
  #define TLS_DHE_RSA_WITH_CHACHA20_POLY1305_SHA256       0xCCAA
  
  #define TLS_FALLBACK_SCSV                     0x5600
  
  #define TLS_UNSUPPORTED_ALGORITHM   0x00
  #define TLS_RSA_SIGN_RSA            0x01
  #define TLS_RSA_SIGN_MD5            0x04
  #define TLS_RSA_SIGN_SHA1           0x05
  #define TLS_RSA_SIGN_SHA256         0x0B
  #define TLS_RSA_SIGN_SHA384         0x0C
  #define TLS_RSA_SIGN_SHA512         0x0D
  #define TLS_ECDSA_SIGN_SHA256       0x0E
  
  #define TLS_EC_PUBLIC_KEY           0x11
  #define TLS_EC_prime192v1           0x12
  #define TLS_EC_prime192v2           0x13
  #define TLS_EC_prime192v3           0x14
  #define TLS_EC_prime239v1           0x15
  #define TLS_EC_prime239v2           0x16
  #define TLS_EC_prime239v3           0x17
  #define TLS_EC_prime256v1           0x18
  #define TLS_EC_secp224r1            21
  #define TLS_EC_secp256r1            23
  #define TLS_EC_secp384r1            24
  #define TLS_EC_secp521r1            25
  
  #define TLS_ALERT_WARNING           0x01
  #define TLS_ALERT_CRITICAL          0x02
  
  #ifdef TLS_ROBOT_MITIGATION
      #define TLS_CIPHERS_SIZE(n, mitigated)         n * 2
  #else
      #define TLS_CIPHERS_SIZE(n, mitigated)         (n + mitigated) * 2
  #endif
  
  #ifdef __cplusplus
  extern "C" {
  #endif
  
  typedef enum {
      close_notify = 0,
      unexpected_message = 10,
      bad_record_mac = 20,
      decryption_failed_RESERVED = 21,
      record_overflow = 22,
      decompression_failure = 30,
      handshake_failure = 40,
      no_certificate_RESERVED = 41,
      bad_certificate = 42,
      unsupported_certificate = 43,
      certificate_revoked = 44,
      certificate_expired = 45,
      certificate_unknown = 46,
      illegal_parameter = 47,
      unknown_ca = 48,
      access_denied = 49,
      decode_error = 50,
      decrypt_error = 51,
      export_restriction_RESERVED = 60,
      protocol_version = 70,
      insufficient_security = 71,
      internal_error = 80,
      inappropriate_fallback = 86,
      user_canceled = 90,
      no_renegotiation = 100,
      unsupported_extension = 110,
      no_error = 255
  } TLSAlertDescription;
  
  // forward declarations
  struct TLSPacket;
  struct TLSCertificate;
  struct TLSContext;
  struct ECCCurveParameters;
  typedef struct TLSContext TLS;
  typedef struct TLSCertificate Certificate;
  
  typedef int (*tls_validation_function)(struct TLSContext *context, struct TLSCertificate **certificate_chain, int len);
  
  /*
    Global initialization. Optional, as it will be called automatically;
    however, the initialization is not thread-safe, so if you intend to use TLSe
    from multiple threads, you'll need to call tls_init() once, from a single thread,
    before using the library.
   */
  void tls_init();
  unsigned char *tls_pem_decode(const unsigned char *data_in, unsigned int input_length, int cert_index, unsigned int *output_len);
  struct TLSCertificate *tls_create_certificate();
  int tls_certificate_valid_subject(struct TLSCertificate *cert, const char *subject);
  int tls_certificate_valid_subject_name(const unsigned char *cert_subject, const char *subject);
  int tls_certificate_is_valid(struct TLSCertificate *cert);
  void tls_certificate_set_copy(unsigned char **member, const unsigned char *val, int len);
  void tls_certificate_set_copy_date(unsigned char **member, const unsigned char *val, int len);
  void tls_certificate_set_key(struct TLSCertificate *cert, const unsigned char *val, int len);
  void tls_certificate_set_priv(struct TLSCertificate *cert, const unsigned char *val, int len);
  void tls_certificate_set_sign_key(struct TLSCertificate *cert, const unsigned char *val, int len);
  char *tls_certificate_to_string(struct TLSCertificate *cert, char *buffer, int len);
  void tls_certificate_set_exponent(struct TLSCertificate *cert, const unsigned char *val, int len);
  void tls_certificate_set_serial(struct TLSCertificate *cert, const unsigned char *val, int len);
  void tls_certificate_set_algorithm(struct TLSContext *context, unsigned int *algorithm, const unsigned char *val, int len);
  void tls_destroy_certificate(struct TLSCertificate *cert);
  struct TLSPacket *tls_create_packet(struct TLSContext *context, unsigned char type, unsigned short version, int payload_size_hint);
  void tls_destroy_packet(struct TLSPacket *packet);
  void tls_packet_update(struct TLSPacket *packet);
  int tls_packet_append(struct TLSPacket *packet, const unsigned char *buf, unsigned int len);
  int tls_packet_uint8(struct TLSPacket *packet, unsigned char i);
  int tls_packet_uint16(struct TLSPacket *packet, unsigned short i);
  int tls_packet_uint32(struct TLSPacket *packet, unsigned int i);
  int tls_packet_uint24(struct TLSPacket *packet, unsigned int i);
  int tls_random(unsigned char *key, int len);
  
  /*
    Get encrypted data to write, if any. Once you've sent all of it, call
    tls_buffer_clear().
   */
  const unsigned char *tls_get_write_buffer(struct TLSContext *context, unsigned int *outlen);
  
  void tls_buffer_clear(struct TLSContext *context);
  
  /* Returns 1 for established, 0 for not established yet, and -1 for a critical error. */
  int tls_established(struct TLSContext *context);
  
  /* Discards any unread decrypted data not consumed by tls_read(). */
  void tls_read_clear(struct TLSContext *context);
  
  /*
    Reads any unread decrypted data (see tls_consume_stream). If you don't read all of it,
    the remainder will be left in the internal buffers for next tls_read(). Returns -1 for
    fatal error, 0 for no more data, or otherwise the number of bytes copied into the buffer
    (up to a maximum of the given size).
   */
  int tls_read(struct TLSContext *context, unsigned char *buf, unsigned int size);
  
  struct TLSContext *tls_create_context(unsigned char is_server, unsigned short version);
  const struct ECCCurveParameters *tls_set_curve(struct TLSContext *context, const struct ECCCurveParameters *curve);
  
  /* Create a context for a given client, from a server context. Returns NULL on error. */
  struct TLSContext *tls_accept(struct TLSContext *context);
  
  int tls_set_default_dhe_pg(struct TLSContext *context, const char *p_hex_str, const char *g_hex_str);
  void tls_destroy_context(struct TLSContext *context);
  int tls_cipher_supported(struct TLSContext *context, unsigned short cipher);
  int tls_cipher_is_fs(struct TLSContext *context, unsigned short cipher);
  int tls_choose_cipher(struct TLSContext *context, const unsigned char *buf, int buf_len, int *scsv_set);
  int tls_cipher_is_ephemeral(struct TLSContext *context);
  const char *tls_cipher_name(struct TLSContext *context);
  int tls_is_ecdsa(struct TLSContext *context);
  struct TLSPacket *tls_build_client_key_exchange(struct TLSContext *context);
  struct TLSPacket *tls_build_server_key_exchange(struct TLSContext *context, int method);
  struct TLSPacket *tls_build_hello(struct TLSContext *context, int tls13_downgrade);
  struct TLSPacket *tls_certificate_request(struct TLSContext *context);
  struct TLSPacket *tls_build_verify_request(struct TLSContext *context);
  int tls_parse_hello(struct TLSContext *context, const unsigned char *buf, int buf_len, unsigned int *write_packets, unsigned int *dtls_verified);
  int tls_parse_certificate(struct TLSContext *context, const unsigned char *buf, int buf_len, int is_client);
  int tls_parse_server_key_exchange(struct TLSContext *context, const unsigned char *buf, int buf_len);
  int tls_parse_client_key_exchange(struct TLSContext *context, const unsigned char *buf, int buf_len);
  int tls_parse_server_hello_done(struct TLSContext *context, const unsigned char *buf, int buf_len);
  int tls_parse_finished(struct TLSContext *context, const unsigned char *buf, int buf_len, unsigned int *write_packets);
  int tls_parse_verify(struct TLSContext *context, const unsigned char *buf, int buf_len);
  int tls_parse_payload(struct TLSContext *context, const unsigned char *buf, int buf_len, tls_validation_function certificate_verify);
  int tls_parse_message(struct TLSContext *context, unsigned char *buf, int buf_len, tls_validation_function certificate_verify);
  int tls_certificate_verify_signature(struct TLSCertificate *cert, struct TLSCertificate *parent);
  int tls_certificate_chain_is_valid(struct TLSCertificate **certificates, int len);
  int tls_certificate_chain_is_valid_root(struct TLSContext *context, struct TLSCertificate **certificates, int len);
  
  /*
    Add a certificate or a certificate chain to the given context, in PEM form.
    Returns a negative value (TLS_GENERIC_ERROR etc.) on error, 0 if there were no
    certificates in the buffer, or the number of loaded certificates on success.
   */
  int tls_load_certificates(struct TLSContext *context, const unsigned char *pem_buffer, int pem_size);
  
  /*
    Add a private key to the given context, in PEM form. Returns a negative value
    (TLS_GENERIC_ERROR etc.) on error, 0 if there was no private key in the
    buffer, or 1 on success.
   */
  int tls_load_private_key(struct TLSContext *context, const unsigned char *pem_buffer, int pem_size);
  struct TLSPacket *tls_build_certificate(struct TLSContext *context);
  struct TLSPacket *tls_build_finished(struct TLSContext *context);
  struct TLSPacket *tls_build_change_cipher_spec(struct TLSContext *context);
  struct TLSPacket *tls_build_done(struct TLSContext *context);
  struct TLSPacket *tls_build_message(struct TLSContext *context, const unsigned char *data, unsigned int len);
  int tls_client_connect(struct TLSContext *context);
  int tls_write(struct TLSContext *context, const unsigned char *data, unsigned int len);
  struct TLSPacket *tls_build_alert(struct TLSContext *context, char critical, unsigned char code);
  
  /*
    Process a given number of input bytes from a socket. If the other side just
    presented a certificate and certificate_verify is not NULL, it will be called.
  
    Returns 0 if there's no data ready yet, a negative value (see
    TLS_GENERIC_ERROR etc.) for an error, or a positive value (the number of bytes
    used from buf) if one or more complete TLS messages were received. The data
    is copied into an internal buffer even if not all of it was consumed,
    so you should not re-send it the next time.
  
    Decrypted data, if any, should be read back with tls_read(). Can change the
    status of tls_established(). If the library has anything to send back on the
    socket (e.g. as part of the handshake), tls_get_write_buffer() will return
    non-NULL.
   */
  int tls_consume_stream(struct TLSContext *context, const unsigned char *buf, int buf_len, tls_validation_function certificate_verify);
  void tls_close_notify(struct TLSContext *context);
  void tls_alert(struct TLSContext *context, unsigned char critical, int code);
  
  /* Whether tls_consume_stream() has data in its buffer that is not processed yet. */
  int tls_pending(struct TLSContext *context);
  
  /*
    Set the context as serializable or not. Must be called before negotiation.
    Exportable contexts use a bit more memory, to be able to hold the keys.
  
    Note that imported keys are not reexportable unless TLS_REEXPORTABLE is set.
   */
  void tls_make_exportable(struct TLSContext *context, unsigned char exportable_flag);
  
  int tls_export_context(struct TLSContext *context, unsigned char *buffer, unsigned int buf_len, unsigned char small_version);
  struct TLSContext *tls_import_context(const unsigned char *buffer, unsigned int buf_len);
  int tls_is_broken(struct TLSContext *context);
  int tls_request_client_certificate(struct TLSContext *context);
  int tls_client_verified(struct TLSContext *context);
  const char *tls_sni(struct TLSContext *context);
  int tls_sni_set(struct TLSContext *context, const char *sni);
  int tls_load_root_certificates(struct TLSContext *context, const unsigned char *pem_buffer, int pem_size);
  int tls_default_verify(struct TLSContext *context, struct TLSCertificate **certificate_chain, int len);
  void tls_print_certificate(const char *fname);
  int tls_add_alpn(struct TLSContext *context, const char *alpn);
  int tls_alpn_contains(struct TLSContext *context, const char *alpn, unsigned char alpn_size);
  const char *tls_alpn(struct TLSContext *context);
  // useful when renewing certificates for servers, without the need to restart the server
  int tls_clear_certificates(struct TLSContext *context);
  int tls_make_ktls(struct TLSContext *context, int socket);
  int tls_unmake_ktls(struct TLSContext *context, int socket);
  /*
    Creates a new DTLS random cookie secret to be used in HelloVerifyRequest (server-side).
    It is recommended to call this function from time to time, to protect against some 
    DoS attacks.
  */
  void dtls_reset_cookie_secret();
  
  int tls_remote_error(struct TLSContext *context);
  
  #ifdef SSL_COMPATIBLE_INTERFACE
      #define SSL_SERVER_RSA_CERT 1
      #define SSL_SERVER_RSA_KEY  2
      typedef struct TLSContext SSL_CTX;
      typedef struct TLSContext SSL;
  
      #define SSL_FILETYPE_PEM    1
      #define SSL_VERIFY_NONE     0
      #define SSL_VERIFY_PEER     1
      #define SSL_VERIFY_FAIL_IF_NO_PEER_CERT 2
      #define SSL_VERIFY_CLIENT_ONCE  3
  
      typedef struct {
          int fd;
          tls_validation_function certificate_verify;
          void *recv;
          void *send;
          void *user_data;
      } SSLUserData;
  
      int  SSL_library_init();
      void SSL_load_error_strings();
      void OpenSSL_add_all_algorithms();
      void OpenSSL_add_all_ciphers();
      void OpenSSL_add_all_digests();
      void EVP_cleanup();
  
      int SSLv3_server_method();
      int SSLv3_client_method();
      struct TLSContext *SSL_new(struct TLSContext *context);
      int SSL_CTX_use_certificate_file(struct TLSContext *context, const char *filename, int dummy);
      int SSL_CTX_use_PrivateKey_file(struct TLSContext *context, const char *filename, int dummy);
      int SSL_CTX_check_private_key(struct TLSContext *context);
      struct TLSContext *SSL_CTX_new(int method);
      void SSL_free(struct TLSContext *context);
      void SSL_CTX_free(struct TLSContext *context);
      int SSL_get_error(struct TLSContext *context, int ret);
      int SSL_set_fd(struct TLSContext *context, int socket);
      void *SSL_set_userdata(struct TLSContext *context, void *data);
      void *SSL_userdata(struct TLSContext *context);
      int SSL_CTX_root_ca(struct TLSContext *context, const char *pem_filename);
      void SSL_CTX_set_verify(struct TLSContext *context, int mode, tls_validation_function verify_callback);
      int SSL_accept(struct TLSContext *context);
      int SSL_connect(struct TLSContext *context);
      int SSL_shutdown(struct TLSContext *context);
      int SSL_write(struct TLSContext *context, const void *buf, unsigned int len);
      int SSL_read(struct TLSContext *context, void *buf, unsigned int len);
      int SSL_pending(struct TLSContext *context);
      int SSL_set_io(struct TLSContext *context, void *recv, void *send);
  #endif
  
  #ifdef TLS_SRTP
      struct SRTPContext;
      #define SRTP_NULL           0
      #define SRTP_AES_CM         1
      #define SRTP_AUTH_NULL      0
      #define SRTP_AUTH_HMAC_SHA1 1
  
      struct SRTPContext *srtp_init(unsigned char mode, unsigned char auth_mode);
      int srtp_key(struct SRTPContext *context, const void *key, int keylen, const void *salt, int saltlen, int tag_bits);
      int srtp_inline(struct SRTPContext *context, const char *b64, int tag_bits);
      int srtp_encrypt(struct SRTPContext *context, const unsigned char *pt_header, int pt_len, const unsigned char *payload, unsigned int payload_len, unsigned char *out, int *out_buffer_len);
      int srtp_decrypt(struct SRTPContext *context, const unsigned char *pt_header, int pt_len, const unsigned char *payload, unsigned int payload_len, unsigned char *out, int *out_buffer_len);
      void srtp_destroy(struct SRTPContext *context);
  #endif
  
  #ifdef __cplusplus
  }  // extern "C"
  #endif
  
  #endif
  