text: #ifndef HEADER_CURL_VTLS_H
  #define HEADER_CURL_VTLS_H
  /***************************************************************************
   *                                  _   _ ____  _
   *  Project                     ___| | | |  _ \| |
   *                             / __| | | | |_) | |
   *                            | (__| |_| |  _ <| |___
   *                             \___|\___/|_| \_\_____|
   *
   * Copyright (C) 1998 - 2020, Daniel Stenberg, <daniel@haxx.se>, et al.
   *
   * This software is licensed as described in the file COPYING, which
   * you should have received as part of this distribution. The terms
   * are also available at https://curl.haxx.se/docs/copyright.html.
   *
   * You may opt to use, copy, modify, merge, publish, distribute and/or sell
   * copies of the Software, and permit persons to whom the Software is
   * furnished to do so, under the terms of the COPYING file.
   *
   * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
   * KIND, either express or implied.
   *
   ***************************************************************************/
  #include "curl_setup.h"
  
  struct connectdata;
  struct ssl_connect_data;
  
  #define SSLSUPP_CA_PATH      (1<<0) /* supports CAPATH */
  #define SSLSUPP_CERTINFO     (1<<1) /* supports CURLOPT_CERTINFO */
  #define SSLSUPP_PINNEDPUBKEY (1<<2) /* supports CURLOPT_PINNEDPUBLICKEY */
  #define SSLSUPP_SSL_CTX      (1<<3) /* supports CURLOPT_SSL_CTX */
  #define SSLSUPP_HTTPS_PROXY  (1<<4) /* supports access via HTTPS proxies */
  #define SSLSUPP_TLS13_CIPHERSUITES (1<<5) /* supports TLS 1.3 ciphersuites */
  
  struct Curl_ssl {
    /*
     * This *must* be the first entry to allow returning the list of available
     * backends in curl_global_sslset().
     */
    curl_ssl_backend info;
    unsigned int supports; /* bitfield, see above */
    size_t sizeof_ssl_backend_data;
  
    int (*init)(void);
    void (*cleanup)(void);
  
    size_t (*version)(char *buffer, size_t size);
    int (*check_cxn)(struct connectdata *cxn);
    int (*shut_down)(struct connectdata *conn, int sockindex);
    bool (*data_pending)(const struct connectdata *conn,
                         int connindex);
  
    /* return 0 if a find random is filled in */
    CURLcode (*random)(struct Curl_easy *data, unsigned char *entropy,
                       size_t length);
    bool (*cert_status_request)(void);
  
    CURLcode (*connect_blocking)(struct connectdata *conn, int sockindex);
    CURLcode (*connect_nonblocking)(struct connectdata *conn, int sockindex,
                                    bool *done);
    void *(*get_internals)(struct ssl_connect_data *connssl, CURLINFO info);
    void (*close_one)(struct connectdata *conn, int sockindex);
    void (*close_all)(struct Curl_easy *data);
    void (*session_free)(void *ptr);
  
    CURLcode (*set_engine)(struct Curl_easy *data, const char *engine);
    CURLcode (*set_engine_default)(struct Curl_easy *data);
    struct curl_slist *(*engines_list)(struct Curl_easy *data);
  
    bool (*false_start)(void);
  
    CURLcode (*md5sum)(unsigned char *input, size_t inputlen,
                       unsigned char *md5sum, size_t md5sumlen);
    CURLcode (*sha256sum)(const unsigned char *input, size_t inputlen,
                      unsigned char *sha256sum, size_t sha256sumlen);
  };
  
  #ifdef USE_SSL
  extern const struct Curl_ssl *Curl_ssl;
  #endif
  
  int Curl_none_init(void);
  void Curl_none_cleanup(void);
  int Curl_none_shutdown(struct connectdata *conn, int sockindex);
  int Curl_none_check_cxn(struct connectdata *conn);
  CURLcode Curl_none_random(struct Curl_easy *data, unsigned char *entropy,
                            size_t length);
  void Curl_none_close_all(struct Curl_easy *data);
  void Curl_none_session_free(void *ptr);
  bool Curl_none_data_pending(const struct connectdata *conn, int connindex);
  bool Curl_none_cert_status_request(void);
  CURLcode Curl_none_set_engine(struct Curl_easy *data, const char *engine);
  CURLcode Curl_none_set_engine_default(struct Curl_easy *data);
  struct curl_slist *Curl_none_engines_list(struct Curl_easy *data);
  bool Curl_none_false_start(void);
  bool Curl_ssl_tls13_ciphersuites(void);
  CURLcode Curl_none_md5sum(unsigned char *input, size_t inputlen,
                            unsigned char *md5sum, size_t md5len);
  
  #include "openssl.h"        /* OpenSSL versions */
  #include "gtls.h"           /* GnuTLS versions */
  #include "nssg.h"           /* NSS versions */
  #include "gskit.h"          /* Global Secure ToolKit versions */
  #include "wolfssl.h"        /* wolfSSL versions */
  #include "schannel.h"       /* Schannel SSPI version */
  #include "sectransp.h"      /* SecureTransport (Darwin) version */
  #include "mbedtls.h"        /* mbedTLS versions */
  #include "mesalink.h"       /* MesaLink versions */
  #include "bearssl.h"        /* BearSSL versions */
  
  #ifndef MAX_PINNED_PUBKEY_SIZE
  #define MAX_PINNED_PUBKEY_SIZE 1048576 /* 1MB */
  #endif
  
  #ifndef MD5_DIGEST_LENGTH
  #ifndef LIBWOLFSSL_VERSION_HEX /* because WolfSSL borks this */
  #define MD5_DIGEST_LENGTH 16 /* fixed size */
  #endif
  #endif
  
  #ifndef CURL_SHA256_DIGEST_LENGTH
  #define CURL_SHA256_DIGEST_LENGTH 32 /* fixed size */
  #endif
  
  /* see https://tools.ietf.org/html/draft-ietf-tls-applayerprotoneg-04 */
  #define ALPN_HTTP_1_1_LENGTH 8
  #define ALPN_HTTP_1_1 "http/1.1"
  
  /* set of helper macros for the backends to access the correct fields. For the
     proxy or for the remote host - to properly support HTTPS proxy */
  
  #define SSL_IS_PROXY() (CURLPROXY_HTTPS == conn->http_proxy.proxytype && \
    ssl_connection_complete != conn->proxy_ssl[conn->sock[SECONDARYSOCKET] == \
    CURL_SOCKET_BAD ? FIRSTSOCKET : SECONDARYSOCKET].state)
  #define SSL_SET_OPTION(var) (SSL_IS_PROXY() ? data->set.proxy_ssl.var : \
                               data->set.ssl.var)
  #define SSL_CONN_CONFIG(var) (SSL_IS_PROXY() ?          \
    conn->proxy_ssl_config.var : conn->ssl_config.var)
  
  bool Curl_ssl_config_matches(struct ssl_primary_config* data,
                               struct ssl_primary_config* needle);
  bool Curl_clone_primary_ssl_config(struct ssl_primary_config *source,
                                     struct ssl_primary_config *dest);
  void Curl_free_primary_ssl_config(struct ssl_primary_config* sslc);
  int Curl_ssl_getsock(struct connectdata *conn, curl_socket_t *socks);
  
  int Curl_ssl_backend(void);
  
  #ifdef USE_SSL
  int Curl_ssl_init(void);
  void Curl_ssl_cleanup(void);
  CURLcode Curl_ssl_connect(struct connectdata *conn, int sockindex);
  CURLcode Curl_ssl_connect_nonblocking(struct connectdata *conn,
                                        int sockindex,
                                        bool *done);
  /* tell the SSL stuff to close down all open information regarding
     connections (and thus session ID caching etc) */
  void Curl_ssl_close_all(struct Curl_easy *data);
  void Curl_ssl_close(struct connectdata *conn, int sockindex);
  CURLcode Curl_ssl_shutdown(struct connectdata *conn, int sockindex);
  CURLcode Curl_ssl_set_engine(struct Curl_easy *data, const char *engine);
  /* Sets engine as default for all SSL operations */
  CURLcode Curl_ssl_set_engine_default(struct Curl_easy *data);
  struct curl_slist *Curl_ssl_engines_list(struct Curl_easy *data);
  
  /* init the SSL session ID cache */
  CURLcode Curl_ssl_initsessions(struct Curl_easy *, size_t);
  size_t Curl_ssl_version(char *buffer, size_t size);
  bool Curl_ssl_data_pending(const struct connectdata *conn,
                             int connindex);
  int Curl_ssl_check_cxn(struct connectdata *conn);
  
  /* Certificate information list handling. */
  
  void Curl_ssl_free_certinfo(struct Curl_easy *data);
  CURLcode Curl_ssl_init_certinfo(struct Curl_easy *data, int num);
  CURLcode Curl_ssl_push_certinfo_len(struct Curl_easy *data, int certnum,
                                      const char *label, const char *value,
                                      size_t valuelen);
  CURLcode Curl_ssl_push_certinfo(struct Curl_easy *data, int certnum,
                                  const char *label, const char *value);
  
  /* Functions to be used by SSL library adaptation functions */
  
  /* Lock session cache mutex.
   * Call this before calling other Curl_ssl_*session* functions
   * Caller should unlock this mutex as soon as possible, as it may block
   * other SSL connection from making progress.
   * The purpose of explicitly locking SSL session cache data is to allow
   * individual SSL engines to manage session lifetime in their specific way.
   */
  void Curl_ssl_sessionid_lock(struct connectdata *conn);
  
  /* Unlock session cache mutex */
  void Curl_ssl_sessionid_unlock(struct connectdata *conn);
  
  /* extract a session ID
   * Sessionid mutex must be locked (see Curl_ssl_sessionid_lock).
   * Caller must make sure that the ownership of returned sessionid object
   * is properly taken (e.g. its refcount is incremented
   * under sessionid mutex).
   */
  bool Curl_ssl_getsessionid(struct connectdata *conn,
                             void **ssl_sessionid,
                             size_t *idsize, /* set 0 if unknown */
                             int sockindex);
  /* add a new session ID
   * Sessionid mutex must be locked (see Curl_ssl_sessionid_lock).
   * Caller must ensure that it has properly shared ownership of this sessionid
   * object with cache (e.g. incrementing refcount on success)
   */
  CURLcode Curl_ssl_addsessionid(struct connectdata *conn,
                                 void *ssl_sessionid,
                                 size_t idsize,
                                 int sockindex);
  /* Kill a single session ID entry in the cache
   * Sessionid mutex must be locked (see Curl_ssl_sessionid_lock).
   * This will call engine-specific curlssl_session_free function, which must
   * take sessionid object ownership from sessionid cache
   * (e.g. decrement refcount).
   */
  void Curl_ssl_kill_session(struct curl_ssl_session *session);
  /* delete a session from the cache
   * Sessionid mutex must be locked (see Curl_ssl_sessionid_lock).
   * This will call engine-specific curlssl_session_free function, which must
   * take sessionid object ownership from sessionid cache
   * (e.g. decrement refcount).
   */
  void Curl_ssl_delsessionid(struct connectdata *conn, void *ssl_sessionid);
  
  /* get N random bytes into the buffer */
  CURLcode Curl_ssl_random(struct Curl_easy *data, unsigned char *buffer,
                           size_t length);
  CURLcode Curl_ssl_md5sum(unsigned char *tmp, /* input */
                           size_t tmplen,
                           unsigned char *md5sum, /* output */
                           size_t md5len);
  /* Check pinned public key. */
  CURLcode Curl_pin_peer_pubkey(struct Curl_easy *data,
                                const char *pinnedpubkey,
                                const unsigned char *pubkey, size_t pubkeylen);
  
  bool Curl_ssl_cert_status_request(void);
  
  bool Curl_ssl_false_start(void);
  
  #define SSL_SHUTDOWN_TIMEOUT 10000 /* ms */
  
  #else /* if not USE_SSL */
  
  /* When SSL support is not present, just define away these function calls */
  #define Curl_ssl_init() 1
  #define Curl_ssl_cleanup() Curl_nop_stmt
  #define Curl_ssl_connect(x,y) CURLE_NOT_BUILT_IN
  #define Curl_ssl_close_all(x) Curl_nop_stmt
  #define Curl_ssl_close(x,y) Curl_nop_stmt
  #define Curl_ssl_shutdown(x,y) CURLE_NOT_BUILT_IN
  #define Curl_ssl_set_engine(x,y) CURLE_NOT_BUILT_IN
  #define Curl_ssl_set_engine_default(x) CURLE_NOT_BUILT_IN
  #define Curl_ssl_engines_list(x) NULL
  #define Curl_ssl_send(a,b,c,d,e) -1
  #define Curl_ssl_recv(a,b,c,d,e) -1
  #define Curl_ssl_initsessions(x,y) CURLE_OK
  #define Curl_ssl_data_pending(x,y) 0
  #define Curl_ssl_check_cxn(x) 0
  #define Curl_ssl_free_certinfo(x) Curl_nop_stmt
  #define Curl_ssl_connect_nonblocking(x,y,z) CURLE_NOT_BUILT_IN
  #define Curl_ssl_kill_session(x) Curl_nop_stmt
  #define Curl_ssl_random(x,y,z) ((void)x, CURLE_NOT_BUILT_IN)
  #define Curl_ssl_cert_status_request() FALSE
  #define Curl_ssl_false_start() FALSE
  #define Curl_ssl_tls13_ciphersuites() FALSE
  #endif
  
  #endif /* HEADER_CURL_VTLS_H */
  