--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mupdf-source/thirdparty/curl/lib/vtls/gtls.c	Mon Sep 15 11:43:07 2025 +0200
@@ -0,0 +1,1881 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 1998 - 2019, 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.
+ *
+ ***************************************************************************/
+
+/*
+ * Source file for all GnuTLS-specific code for the TLS/SSL layer. No code
+ * but vtls.c should ever call or use these functions.
+ *
+ * Note: don't use the GnuTLS' *_t variable type names in this source code,
+ * since they were not present in 1.0.X.
+ */
+
+#include "curl_setup.h"
+
+#ifdef USE_GNUTLS
+
+#include <gnutls/abstract.h>
+#include <gnutls/gnutls.h>
+#include <gnutls/x509.h>
+
+#ifdef USE_GNUTLS_NETTLE
+#include <gnutls/crypto.h>
+#include <nettle/md5.h>
+#include <nettle/sha2.h>
+#else
+#include <gcrypt.h>
+#endif
+
+#include "urldata.h"
+#include "sendf.h"
+#include "inet_pton.h"
+#include "gtls.h"
+#include "vtls.h"
+#include "parsedate.h"
+#include "connect.h" /* for the connect timeout */
+#include "select.h"
+#include "strcase.h"
+#include "warnless.h"
+#include "x509asn1.h"
+#include "multiif.h"
+#include "curl_printf.h"
+#include "curl_memory.h"
+/* The last #include file should be: */
+#include "memdebug.h"
+
+/* Enable GnuTLS debugging by defining GTLSDEBUG */
+/*#define GTLSDEBUG */
+
+#ifdef GTLSDEBUG
+static void tls_log_func(int level, const char *str)
+{
+    fprintf(stderr, "|<%d>| %s", level, str);
+}
+#endif
+static bool gtls_inited = FALSE;
+
+#if defined(GNUTLS_VERSION_NUMBER)
+#  if (GNUTLS_VERSION_NUMBER >= 0x020c00)
+#    undef gnutls_transport_set_lowat
+#    define gnutls_transport_set_lowat(A,B) Curl_nop_stmt
+#    define USE_GNUTLS_PRIORITY_SET_DIRECT 1
+#  endif
+#  if (GNUTLS_VERSION_NUMBER >= 0x020c03)
+#    define GNUTLS_MAPS_WINSOCK_ERRORS 1
+#  endif
+
+#  if HAVE_GNUTLS_ALPN_SET_PROTOCOLS
+#    define HAS_ALPN
+#  endif
+
+#  if HAVE_GNUTLS_OCSP_REQ_INIT
+#    define HAS_OCSP
+#  endif
+
+#  if (GNUTLS_VERSION_NUMBER >= 0x030306)
+#    define HAS_CAPATH
+#  endif
+#endif
+
+#if (GNUTLS_VERSION_NUMBER >= 0x030603)
+#define HAS_TLS13
+#endif
+
+#ifdef HAS_OCSP
+# include <gnutls/ocsp.h>
+#endif
+
+struct ssl_backend_data {
+  gnutls_session_t session;
+  gnutls_certificate_credentials_t cred;
+#ifdef USE_TLS_SRP
+  gnutls_srp_client_credentials_t srp_client_cred;
+#endif
+};
+
+#define BACKEND connssl->backend
+
+/*
+ * Custom push and pull callback functions used by GNU TLS to read and write
+ * to the socket.  These functions are simple wrappers to send() and recv()
+ * (although here using the sread/swrite macros as defined by
+ * curl_setup_once.h).
+ * We use custom functions rather than the GNU TLS defaults because it allows
+ * us to get specific about the fourth "flags" argument, and to use arbitrary
+ * private data with gnutls_transport_set_ptr if we wish.
+ *
+ * When these custom push and pull callbacks fail, GNU TLS checks its own
+ * session-specific error variable, and when not set also its own global
+ * errno variable, in order to take appropriate action. GNU TLS does not
+ * require that the transport is actually a socket. This implies that for
+ * Windows builds these callbacks should ideally set the session-specific
+ * error variable using function gnutls_transport_set_errno or as a last
+ * resort global errno variable using gnutls_transport_set_global_errno,
+ * with a transport agnostic error value. This implies that some winsock
+ * error translation must take place in these callbacks.
+ *
+ * Paragraph above applies to GNU TLS versions older than 2.12.3, since
+ * this version GNU TLS does its own internal winsock error translation
+ * using system_errno() function.
+ */
+
+#if defined(USE_WINSOCK) && !defined(GNUTLS_MAPS_WINSOCK_ERRORS)
+#  define gtls_EINTR  4
+#  define gtls_EIO    5
+#  define gtls_EAGAIN 11
+static int gtls_mapped_sockerrno(void)
+{
+  switch(SOCKERRNO) {
+  case WSAEWOULDBLOCK:
+    return gtls_EAGAIN;
+  case WSAEINTR:
+    return gtls_EINTR;
+  default:
+    break;
+  }
+  return gtls_EIO;
+}
+#endif
+
+static ssize_t Curl_gtls_push(void *s, const void *buf, size_t len)
+{
+  curl_socket_t sock = *(curl_socket_t *)s;
+  ssize_t ret = swrite(sock, buf, len);
+#if defined(USE_WINSOCK) && !defined(GNUTLS_MAPS_WINSOCK_ERRORS)
+  if(ret < 0)
+    gnutls_transport_set_global_errno(gtls_mapped_sockerrno());
+#endif
+  return ret;
+}
+
+static ssize_t Curl_gtls_pull(void *s, void *buf, size_t len)
+{
+  curl_socket_t sock = *(curl_socket_t *)s;
+  ssize_t ret = sread(sock, buf, len);
+#if defined(USE_WINSOCK) && !defined(GNUTLS_MAPS_WINSOCK_ERRORS)
+  if(ret < 0)
+    gnutls_transport_set_global_errno(gtls_mapped_sockerrno());
+#endif
+  return ret;
+}
+
+static ssize_t Curl_gtls_push_ssl(void *s, const void *buf, size_t len)
+{
+  return gnutls_record_send((gnutls_session_t) s, buf, len);
+}
+
+static ssize_t Curl_gtls_pull_ssl(void *s, void *buf, size_t len)
+{
+  return gnutls_record_recv((gnutls_session_t) s, buf, len);
+}
+
+/* Curl_gtls_init()
+ *
+ * Global GnuTLS init, called from Curl_ssl_init(). This calls functions that
+ * are not thread-safe and thus this function itself is not thread-safe and
+ * must only be called from within curl_global_init() to keep the thread
+ * situation under control!
+ */
+static int Curl_gtls_init(void)
+{
+  int ret = 1;
+  if(!gtls_inited) {
+    ret = gnutls_global_init()?0:1;
+#ifdef GTLSDEBUG
+    gnutls_global_set_log_function(tls_log_func);
+    gnutls_global_set_log_level(2);
+#endif
+    gtls_inited = TRUE;
+  }
+  return ret;
+}
+
+static void Curl_gtls_cleanup(void)
+{
+  if(gtls_inited) {
+    gnutls_global_deinit();
+    gtls_inited = FALSE;
+  }
+}
+
+#ifndef CURL_DISABLE_VERBOSE_STRINGS
+static void showtime(struct Curl_easy *data,
+                     const char *text,
+                     time_t stamp)
+{
+  struct tm buffer;
+  const struct tm *tm = &buffer;
+  char str[96];
+  CURLcode result = Curl_gmtime(stamp, &buffer);
+  if(result)
+    return;
+
+  msnprintf(str,
+            sizeof(str),
+            "\t %s: %s, %02d %s %4d %02d:%02d:%02d GMT",
+            text,
+            Curl_wkday[tm->tm_wday?tm->tm_wday-1:6],
+            tm->tm_mday,
+            Curl_month[tm->tm_mon],
+            tm->tm_year + 1900,
+            tm->tm_hour,
+            tm->tm_min,
+            tm->tm_sec);
+  infof(data, "%s\n", str);
+}
+#endif
+
+static gnutls_datum_t load_file(const char *file)
+{
+  FILE *f;
+  gnutls_datum_t loaded_file = { NULL, 0 };
+  long filelen;
+  void *ptr;
+
+  f = fopen(file, "rb");
+  if(!f)
+    return loaded_file;
+  if(fseek(f, 0, SEEK_END) != 0
+     || (filelen = ftell(f)) < 0
+     || fseek(f, 0, SEEK_SET) != 0
+     || !(ptr = malloc((size_t)filelen)))
+    goto out;
+  if(fread(ptr, 1, (size_t)filelen, f) < (size_t)filelen) {
+    free(ptr);
+    goto out;
+  }
+
+  loaded_file.data = ptr;
+  loaded_file.size = (unsigned int)filelen;
+out:
+  fclose(f);
+  return loaded_file;
+}
+
+static void unload_file(gnutls_datum_t data)
+{
+  free(data.data);
+}
+
+
+/* this function does a SSL/TLS (re-)handshake */
+static CURLcode handshake(struct connectdata *conn,
+                          int sockindex,
+                          bool duringconnect,
+                          bool nonblocking)
+{
+  struct Curl_easy *data = conn->data;
+  struct ssl_connect_data *connssl = &conn->ssl[sockindex];
+  gnutls_session_t session = BACKEND->session;
+  curl_socket_t sockfd = conn->sock[sockindex];
+
+  for(;;) {
+    time_t timeout_ms;
+    int rc;
+
+    /* check allowed time left */
+    timeout_ms = Curl_timeleft(data, NULL, duringconnect);
+
+    if(timeout_ms < 0) {
+      /* no need to continue if time already is up */
+      failf(data, "SSL connection timeout");
+      return CURLE_OPERATION_TIMEDOUT;
+    }
+
+    /* if ssl is expecting something, check if it's available. */
+    if(connssl->connecting_state == ssl_connect_2_reading
+       || connssl->connecting_state == ssl_connect_2_writing) {
+      int what;
+      curl_socket_t writefd = ssl_connect_2_writing ==
+        connssl->connecting_state?sockfd:CURL_SOCKET_BAD;
+      curl_socket_t readfd = ssl_connect_2_reading ==
+        connssl->connecting_state?sockfd:CURL_SOCKET_BAD;
+
+      what = Curl_socket_check(readfd, CURL_SOCKET_BAD, writefd,
+                               nonblocking?0:
+                               timeout_ms?timeout_ms:1000);
+      if(what < 0) {
+        /* fatal error */
+        failf(data, "select/poll on SSL socket, errno: %d", SOCKERRNO);
+        return CURLE_SSL_CONNECT_ERROR;
+      }
+      else if(0 == what) {
+        if(nonblocking)
+          return CURLE_OK;
+        else if(timeout_ms) {
+          /* timeout */
+          failf(data, "SSL connection timeout at %ld", (long)timeout_ms);
+          return CURLE_OPERATION_TIMEDOUT;
+        }
+      }
+      /* socket is readable or writable */
+    }
+
+    rc = gnutls_handshake(session);
+
+    if((rc == GNUTLS_E_AGAIN) || (rc == GNUTLS_E_INTERRUPTED)) {
+      connssl->connecting_state =
+        gnutls_record_get_direction(session)?
+        ssl_connect_2_writing:ssl_connect_2_reading;
+      continue;
+    }
+    else if((rc < 0) && !gnutls_error_is_fatal(rc)) {
+      const char *strerr = NULL;
+
+      if(rc == GNUTLS_E_WARNING_ALERT_RECEIVED) {
+        int alert = gnutls_alert_get(session);
+        strerr = gnutls_alert_get_name(alert);
+      }
+
+      if(strerr == NULL)
+        strerr = gnutls_strerror(rc);
+
+      infof(data, "gnutls_handshake() warning: %s\n", strerr);
+      continue;
+    }
+    else if(rc < 0) {
+      const char *strerr = NULL;
+
+      if(rc == GNUTLS_E_FATAL_ALERT_RECEIVED) {
+        int alert = gnutls_alert_get(session);
+        strerr = gnutls_alert_get_name(alert);
+      }
+
+      if(strerr == NULL)
+        strerr = gnutls_strerror(rc);
+
+      failf(data, "gnutls_handshake() failed: %s", strerr);
+      return CURLE_SSL_CONNECT_ERROR;
+    }
+
+    /* Reset our connect state machine */
+    connssl->connecting_state = ssl_connect_1;
+    return CURLE_OK;
+  }
+}
+
+static gnutls_x509_crt_fmt_t do_file_type(const char *type)
+{
+  if(!type || !type[0])
+    return GNUTLS_X509_FMT_PEM;
+  if(strcasecompare(type, "PEM"))
+    return GNUTLS_X509_FMT_PEM;
+  if(strcasecompare(type, "DER"))
+    return GNUTLS_X509_FMT_DER;
+  return -1;
+}
+
+#ifndef USE_GNUTLS_PRIORITY_SET_DIRECT
+static CURLcode
+set_ssl_version_min_max(int *list, size_t list_size, struct connectdata *conn)
+{
+  struct Curl_easy *data = conn->data;
+  long ssl_version = SSL_CONN_CONFIG(version);
+  long ssl_version_max = SSL_CONN_CONFIG(version_max);
+  long i = ssl_version;
+  long protocol_priority_idx = 0;
+
+  switch(ssl_version_max) {
+    case CURL_SSLVERSION_MAX_NONE:
+    case CURL_SSLVERSION_MAX_DEFAULT:
+#ifdef HAS_TLS13
+      ssl_version_max = CURL_SSLVERSION_MAX_TLSv1_3;
+#endif
+      ssl_version_max = CURL_SSLVERSION_MAX_TLSv1_2;
+      break;
+  }
+
+  for(; i <= (ssl_version_max >> 16) &&
+        protocol_priority_idx < list_size; ++i) {
+    switch(i) {
+      case CURL_SSLVERSION_TLSv1_0:
+        protocol_priority[protocol_priority_idx++] = GNUTLS_TLS1_0;
+        break;
+      case CURL_SSLVERSION_TLSv1_1:
+        protocol_priority[protocol_priority_idx++] = GNUTLS_TLS1_1;
+        break;
+      case CURL_SSLVERSION_TLSv1_2:
+        protocol_priority[protocol_priority_idx++] = GNUTLS_TLS1_2;
+        break;
+      case CURL_SSLVERSION_TLSv1_3:
+#ifdef HAS_TLS13
+        protocol_priority[protocol_priority_idx++] = GNUTLS_TLS1_3;
+        break;
+#else
+        failf(data, "GnuTLS: TLS 1.3 is not yet supported");
+        return CURLE_SSL_CONNECT_ERROR;
+#endif
+    }
+  }
+  return CURLE_OK;
+}
+#else
+#define GNUTLS_CIPHERS "NORMAL:-ARCFOUR-128:-CTYPE-ALL:+CTYPE-X509"
+/* If GnuTLS was compiled without support for SRP it will error out if SRP is
+   requested in the priority string, so treat it specially
+ */
+#define GNUTLS_SRP "+SRP"
+
+static CURLcode
+set_ssl_version_min_max(const char **prioritylist, struct connectdata *conn)
+{
+  struct Curl_easy *data = conn->data;
+  long ssl_version = SSL_CONN_CONFIG(version);
+  long ssl_version_max = SSL_CONN_CONFIG(version_max);
+
+  if(ssl_version_max == CURL_SSLVERSION_MAX_NONE) {
+    ssl_version_max = CURL_SSLVERSION_MAX_DEFAULT;
+  }
+  switch(ssl_version | ssl_version_max) {
+    case CURL_SSLVERSION_TLSv1_0 | CURL_SSLVERSION_MAX_TLSv1_0:
+      *prioritylist = GNUTLS_CIPHERS ":-VERS-SSL3.0:-VERS-TLS-ALL:"
+                      "+VERS-TLS1.0:" GNUTLS_SRP;
+      return CURLE_OK;
+    case CURL_SSLVERSION_TLSv1_0 | CURL_SSLVERSION_MAX_TLSv1_1:
+      *prioritylist = GNUTLS_CIPHERS ":-VERS-SSL3.0:-VERS-TLS-ALL:"
+                      "+VERS-TLS1.0:+VERS-TLS1.1:" GNUTLS_SRP;
+      return CURLE_OK;
+    case CURL_SSLVERSION_TLSv1_0 | CURL_SSLVERSION_MAX_TLSv1_2:
+      *prioritylist = GNUTLS_CIPHERS ":-VERS-SSL3.0:-VERS-TLS-ALL:"
+                      "+VERS-TLS1.0:+VERS-TLS1.1:+VERS-TLS1.2:" GNUTLS_SRP;
+      return CURLE_OK;
+    case CURL_SSLVERSION_TLSv1_1 | CURL_SSLVERSION_MAX_TLSv1_1:
+      *prioritylist = GNUTLS_CIPHERS ":-VERS-SSL3.0:-VERS-TLS-ALL:"
+                      "+VERS-TLS1.1:" GNUTLS_SRP;
+      return CURLE_OK;
+    case CURL_SSLVERSION_TLSv1_1 | CURL_SSLVERSION_MAX_TLSv1_2:
+      *prioritylist = GNUTLS_CIPHERS ":-VERS-SSL3.0:-VERS-TLS-ALL:"
+                      "+VERS-TLS1.1:+VERS-TLS1.2:" GNUTLS_SRP;
+      return CURLE_OK;
+    case CURL_SSLVERSION_TLSv1_2 | CURL_SSLVERSION_MAX_TLSv1_2:
+      *prioritylist = GNUTLS_CIPHERS ":-VERS-SSL3.0:-VERS-TLS-ALL:"
+                      "+VERS-TLS1.2:" GNUTLS_SRP;
+      return CURLE_OK;
+    case CURL_SSLVERSION_TLSv1_3 | CURL_SSLVERSION_MAX_TLSv1_3:
+#ifdef HAS_TLS13
+       *prioritylist = GNUTLS_CIPHERS ":-VERS-SSL3.0:-VERS-TLS-ALL:"
+                       "+VERS-TLS1.3:" GNUTLS_SRP;
+      return CURLE_OK;
+#else
+       failf(data, "GnuTLS: TLS 1.3 is not yet supported");
+      return CURLE_SSL_CONNECT_ERROR;
+#endif
+    case CURL_SSLVERSION_TLSv1_0 | CURL_SSLVERSION_MAX_DEFAULT:
+      *prioritylist = GNUTLS_CIPHERS ":-VERS-SSL3.0:-VERS-TLS-ALL:"
+                      "+VERS-TLS1.0:+VERS-TLS1.1:+VERS-TLS1.2:"
+#ifdef HAS_TLS13
+                      "+VERS-TLS1.3:"
+#endif
+                      GNUTLS_SRP;
+      return CURLE_OK;
+    case CURL_SSLVERSION_TLSv1_1 | CURL_SSLVERSION_MAX_DEFAULT:
+      *prioritylist = GNUTLS_CIPHERS ":-VERS-SSL3.0:-VERS-TLS-ALL:"
+                      "+VERS-TLS1.1:+VERS-TLS1.2:"
+#ifdef HAS_TLS13
+                      "+VERS-TLS1.3:"
+#endif
+                      GNUTLS_SRP;
+      return CURLE_OK;
+    case CURL_SSLVERSION_TLSv1_2 | CURL_SSLVERSION_MAX_DEFAULT:
+      *prioritylist = GNUTLS_CIPHERS ":-VERS-SSL3.0:-VERS-TLS-ALL:"
+                      "+VERS-TLS1.2:"
+#ifdef HAS_TLS13
+                      "+VERS-TLS1.3:"
+#endif
+                      GNUTLS_SRP;
+      return CURLE_OK;
+    case CURL_SSLVERSION_TLSv1_3 | CURL_SSLVERSION_MAX_DEFAULT:
+      *prioritylist = GNUTLS_CIPHERS ":-VERS-SSL3.0:-VERS-TLS-ALL:"
+                      "+VERS-TLS1.2:"
+#ifdef HAS_TLS13
+                      "+VERS-TLS1.3:"
+#endif
+                      GNUTLS_SRP;
+      return CURLE_OK;
+  }
+
+  failf(data, "GnuTLS: cannot set ssl protocol");
+  return CURLE_SSL_CONNECT_ERROR;
+}
+#endif
+
+static CURLcode
+gtls_connect_step1(struct connectdata *conn,
+                   int sockindex)
+{
+  struct Curl_easy *data = conn->data;
+  struct ssl_connect_data *connssl = &conn->ssl[sockindex];
+  unsigned int init_flags;
+  gnutls_session_t session;
+  int rc;
+  bool sni = TRUE; /* default is SNI enabled */
+  void *transport_ptr = NULL;
+  gnutls_push_func gnutls_transport_push = NULL;
+  gnutls_pull_func gnutls_transport_pull = NULL;
+#ifdef ENABLE_IPV6
+  struct in6_addr addr;
+#else
+  struct in_addr addr;
+#endif
+#ifndef USE_GNUTLS_PRIORITY_SET_DIRECT
+  static const int cipher_priority[] = {
+  /* These two ciphers were added to GnuTLS as late as ver. 3.0.1,
+     but this code path is only ever used for ver. < 2.12.0.
+     GNUTLS_CIPHER_AES_128_GCM,
+     GNUTLS_CIPHER_AES_256_GCM,
+  */
+    GNUTLS_CIPHER_AES_128_CBC,
+    GNUTLS_CIPHER_AES_256_CBC,
+    GNUTLS_CIPHER_CAMELLIA_128_CBC,
+    GNUTLS_CIPHER_CAMELLIA_256_CBC,
+    GNUTLS_CIPHER_3DES_CBC,
+  };
+  static const int cert_type_priority[] = { GNUTLS_CRT_X509, 0 };
+  int protocol_priority[] = { 0, 0, 0, 0 };
+#else
+  const char *prioritylist;
+  const char *err = NULL;
+#endif
+
+  const char * const hostname = SSL_IS_PROXY() ? conn->http_proxy.host.name :
+    conn->host.name;
+
+  if(connssl->state == ssl_connection_complete)
+    /* to make us tolerant against being called more than once for the
+       same connection */
+    return CURLE_OK;
+
+  if(!gtls_inited)
+    Curl_gtls_init();
+
+  if(SSL_CONN_CONFIG(version) == CURL_SSLVERSION_SSLv2) {
+    failf(data, "GnuTLS does not support SSLv2");
+    return CURLE_SSL_CONNECT_ERROR;
+  }
+  else if(SSL_CONN_CONFIG(version) == CURL_SSLVERSION_SSLv3)
+    sni = FALSE; /* SSLv3 has no SNI */
+
+  /* allocate a cred struct */
+  rc = gnutls_certificate_allocate_credentials(&BACKEND->cred);
+  if(rc != GNUTLS_E_SUCCESS) {
+    failf(data, "gnutls_cert_all_cred() failed: %s", gnutls_strerror(rc));
+    return CURLE_SSL_CONNECT_ERROR;
+  }
+
+#ifdef USE_TLS_SRP
+  if(SSL_SET_OPTION(authtype) == CURL_TLSAUTH_SRP) {
+    infof(data, "Using TLS-SRP username: %s\n", SSL_SET_OPTION(username));
+
+    rc = gnutls_srp_allocate_client_credentials(
+           &BACKEND->srp_client_cred);
+    if(rc != GNUTLS_E_SUCCESS) {
+      failf(data, "gnutls_srp_allocate_client_cred() failed: %s",
+            gnutls_strerror(rc));
+      return CURLE_OUT_OF_MEMORY;
+    }
+
+    rc = gnutls_srp_set_client_credentials(BACKEND->srp_client_cred,
+                                           SSL_SET_OPTION(username),
+                                           SSL_SET_OPTION(password));
+    if(rc != GNUTLS_E_SUCCESS) {
+      failf(data, "gnutls_srp_set_client_cred() failed: %s",
+            gnutls_strerror(rc));
+      return CURLE_BAD_FUNCTION_ARGUMENT;
+    }
+  }
+#endif
+
+  if(SSL_CONN_CONFIG(CAfile)) {
+    /* set the trusted CA cert bundle file */
+    gnutls_certificate_set_verify_flags(BACKEND->cred,
+                                        GNUTLS_VERIFY_ALLOW_X509_V1_CA_CRT);
+
+    rc = gnutls_certificate_set_x509_trust_file(BACKEND->cred,
+                                                SSL_CONN_CONFIG(CAfile),
+                                                GNUTLS_X509_FMT_PEM);
+    if(rc < 0) {
+      infof(data, "error reading ca cert file %s (%s)\n",
+            SSL_CONN_CONFIG(CAfile), gnutls_strerror(rc));
+      if(SSL_CONN_CONFIG(verifypeer))
+        return CURLE_SSL_CACERT_BADFILE;
+    }
+    else
+      infof(data, "found %d certificates in %s\n", rc,
+            SSL_CONN_CONFIG(CAfile));
+  }
+
+#ifdef HAS_CAPATH
+  if(SSL_CONN_CONFIG(CApath)) {
+    /* set the trusted CA cert directory */
+    rc = gnutls_certificate_set_x509_trust_dir(BACKEND->cred,
+                                               SSL_CONN_CONFIG(CApath),
+                                               GNUTLS_X509_FMT_PEM);
+    if(rc < 0) {
+      infof(data, "error reading ca cert file %s (%s)\n",
+            SSL_CONN_CONFIG(CApath), gnutls_strerror(rc));
+      if(SSL_CONN_CONFIG(verifypeer))
+        return CURLE_SSL_CACERT_BADFILE;
+    }
+    else
+      infof(data, "found %d certificates in %s\n",
+            rc, SSL_CONN_CONFIG(CApath));
+  }
+#endif
+
+#ifdef CURL_CA_FALLBACK
+  /* use system ca certificate store as fallback */
+  if(SSL_CONN_CONFIG(verifypeer) &&
+     !(SSL_CONN_CONFIG(CAfile) || SSL_CONN_CONFIG(CApath))) {
+    gnutls_certificate_set_x509_system_trust(BACKEND->cred);
+  }
+#endif
+
+  if(SSL_SET_OPTION(CRLfile)) {
+    /* set the CRL list file */
+    rc = gnutls_certificate_set_x509_crl_file(BACKEND->cred,
+                                              SSL_SET_OPTION(CRLfile),
+                                              GNUTLS_X509_FMT_PEM);
+    if(rc < 0) {
+      failf(data, "error reading crl file %s (%s)",
+            SSL_SET_OPTION(CRLfile), gnutls_strerror(rc));
+      return CURLE_SSL_CRL_BADFILE;
+    }
+    else
+      infof(data, "found %d CRL in %s\n",
+            rc, SSL_SET_OPTION(CRLfile));
+  }
+
+  /* Initialize TLS session as a client */
+  init_flags = GNUTLS_CLIENT;
+
+#if defined(GNUTLS_NO_TICKETS)
+  /* Disable TLS session tickets */
+  init_flags |= GNUTLS_NO_TICKETS;
+#endif
+
+  rc = gnutls_init(&BACKEND->session, init_flags);
+  if(rc != GNUTLS_E_SUCCESS) {
+    failf(data, "gnutls_init() failed: %d", rc);
+    return CURLE_SSL_CONNECT_ERROR;
+  }
+
+  /* convenient assign */
+  session = BACKEND->session;
+
+  if((0 == Curl_inet_pton(AF_INET, hostname, &addr)) &&
+#ifdef ENABLE_IPV6
+     (0 == Curl_inet_pton(AF_INET6, hostname, &addr)) &&
+#endif
+     sni &&
+     (gnutls_server_name_set(session, GNUTLS_NAME_DNS, hostname,
+                             strlen(hostname)) < 0))
+    infof(data, "WARNING: failed to configure server name indication (SNI) "
+          "TLS extension\n");
+
+  /* Use default priorities */
+  rc = gnutls_set_default_priority(session);
+  if(rc != GNUTLS_E_SUCCESS)
+    return CURLE_SSL_CONNECT_ERROR;
+
+#ifndef USE_GNUTLS_PRIORITY_SET_DIRECT
+  rc = gnutls_cipher_set_priority(session, cipher_priority);
+  if(rc != GNUTLS_E_SUCCESS)
+    return CURLE_SSL_CONNECT_ERROR;
+
+  /* Sets the priority on the certificate types supported by gnutls. Priority
+   is higher for types specified before others. After specifying the types
+   you want, you must append a 0. */
+  rc = gnutls_certificate_type_set_priority(session, cert_type_priority);
+  if(rc != GNUTLS_E_SUCCESS)
+    return CURLE_SSL_CONNECT_ERROR;
+
+  if(SSL_CONN_CONFIG(cipher_list) != NULL) {
+    failf(data, "can't pass a custom cipher list to older GnuTLS"
+          " versions");
+    return CURLE_SSL_CONNECT_ERROR;
+  }
+
+  switch(SSL_CONN_CONFIG(version)) {
+    case CURL_SSLVERSION_SSLv3:
+      protocol_priority[0] = GNUTLS_SSL3;
+      break;
+    case CURL_SSLVERSION_DEFAULT:
+    case CURL_SSLVERSION_TLSv1:
+      protocol_priority[0] = GNUTLS_TLS1_0;
+      protocol_priority[1] = GNUTLS_TLS1_1;
+      protocol_priority[2] = GNUTLS_TLS1_2;
+#ifdef HAS_TLS13
+      protocol_priority[3] = GNUTLS_TLS1_3;
+#endif
+      break;
+    case CURL_SSLVERSION_TLSv1_0:
+    case CURL_SSLVERSION_TLSv1_1:
+    case CURL_SSLVERSION_TLSv1_2:
+    case CURL_SSLVERSION_TLSv1_3:
+      {
+        CURLcode result = set_ssl_version_min_max(protocol_priority,
+                sizeof(protocol_priority)/sizeof(protocol_priority[0]), conn);
+        if(result != CURLE_OK)
+          return result;
+        break;
+      }
+    case CURL_SSLVERSION_SSLv2:
+      failf(data, "GnuTLS does not support SSLv2");
+      return CURLE_SSL_CONNECT_ERROR;
+    default:
+      failf(data, "Unrecognized parameter passed via CURLOPT_SSLVERSION");
+      return CURLE_SSL_CONNECT_ERROR;
+  }
+  rc = gnutls_protocol_set_priority(session, protocol_priority);
+  if(rc != GNUTLS_E_SUCCESS) {
+    failf(data, "Did you pass a valid GnuTLS cipher list?");
+    return CURLE_SSL_CONNECT_ERROR;
+  }
+
+#else
+  /* Ensure +SRP comes at the *end* of all relevant strings so that it can be
+   * removed if a run-time error indicates that SRP is not supported by this
+   * GnuTLS version */
+  switch(SSL_CONN_CONFIG(version)) {
+    case CURL_SSLVERSION_SSLv3:
+      prioritylist = GNUTLS_CIPHERS ":-VERS-TLS-ALL:+VERS-SSL3.0";
+      break;
+    case CURL_SSLVERSION_DEFAULT:
+    case CURL_SSLVERSION_TLSv1:
+      prioritylist = GNUTLS_CIPHERS ":-VERS-SSL3.0:"
+#ifdef HAS_TLS13
+                     "+VERS-TLS1.3:"
+#endif
+                     GNUTLS_SRP;
+      break;
+    case CURL_SSLVERSION_TLSv1_0:
+    case CURL_SSLVERSION_TLSv1_1:
+    case CURL_SSLVERSION_TLSv1_2:
+    case CURL_SSLVERSION_TLSv1_3:
+      {
+        CURLcode result = set_ssl_version_min_max(&prioritylist, conn);
+        if(result != CURLE_OK)
+          return result;
+        break;
+      }
+    case CURL_SSLVERSION_SSLv2:
+      failf(data, "GnuTLS does not support SSLv2");
+      return CURLE_SSL_CONNECT_ERROR;
+    default:
+      failf(data, "Unrecognized parameter passed via CURLOPT_SSLVERSION");
+      return CURLE_SSL_CONNECT_ERROR;
+  }
+  rc = gnutls_priority_set_direct(session, prioritylist, &err);
+  if((rc == GNUTLS_E_INVALID_REQUEST) && err) {
+    if(!strcmp(err, GNUTLS_SRP)) {
+      /* This GnuTLS was probably compiled without support for SRP.
+       * Note that fact and try again without it. */
+      int validprioritylen = curlx_uztosi(err - prioritylist);
+      char *prioritycopy = strdup(prioritylist);
+      if(!prioritycopy)
+        return CURLE_OUT_OF_MEMORY;
+
+      infof(data, "This GnuTLS does not support SRP\n");
+      if(validprioritylen)
+        /* Remove the :+SRP */
+        prioritycopy[validprioritylen - 1] = 0;
+      rc = gnutls_priority_set_direct(session, prioritycopy, &err);
+      free(prioritycopy);
+    }
+  }
+  if(rc != GNUTLS_E_SUCCESS) {
+    failf(data, "Error %d setting GnuTLS cipher list starting with %s",
+          rc, err);
+    return CURLE_SSL_CONNECT_ERROR;
+  }
+#endif
+
+#ifdef HAS_ALPN
+  if(conn->bits.tls_enable_alpn) {
+    int cur = 0;
+    gnutls_datum_t protocols[2];
+
+#ifdef USE_NGHTTP2
+    if(data->set.httpversion >= CURL_HTTP_VERSION_2 &&
+       (!SSL_IS_PROXY() || !conn->bits.tunnel_proxy)) {
+      protocols[cur].data = (unsigned char *)NGHTTP2_PROTO_VERSION_ID;
+      protocols[cur].size = NGHTTP2_PROTO_VERSION_ID_LEN;
+      cur++;
+      infof(data, "ALPN, offering %s\n", NGHTTP2_PROTO_VERSION_ID);
+    }
+#endif
+
+    protocols[cur].data = (unsigned char *)ALPN_HTTP_1_1;
+    protocols[cur].size = ALPN_HTTP_1_1_LENGTH;
+    cur++;
+    infof(data, "ALPN, offering %s\n", ALPN_HTTP_1_1);
+
+    gnutls_alpn_set_protocols(session, protocols, cur, 0);
+  }
+#endif
+
+  if(SSL_SET_OPTION(cert)) {
+    if(SSL_SET_OPTION(key_passwd)) {
+#if HAVE_GNUTLS_CERTIFICATE_SET_X509_KEY_FILE2
+      const unsigned int supported_key_encryption_algorithms =
+        GNUTLS_PKCS_USE_PKCS12_3DES | GNUTLS_PKCS_USE_PKCS12_ARCFOUR |
+        GNUTLS_PKCS_USE_PKCS12_RC2_40 | GNUTLS_PKCS_USE_PBES2_3DES |
+        GNUTLS_PKCS_USE_PBES2_AES_128 | GNUTLS_PKCS_USE_PBES2_AES_192 |
+        GNUTLS_PKCS_USE_PBES2_AES_256;
+      rc = gnutls_certificate_set_x509_key_file2(
+           BACKEND->cred,
+           SSL_SET_OPTION(cert),
+           SSL_SET_OPTION(key) ?
+           SSL_SET_OPTION(key) : SSL_SET_OPTION(cert),
+           do_file_type(SSL_SET_OPTION(cert_type)),
+           SSL_SET_OPTION(key_passwd),
+           supported_key_encryption_algorithms);
+      if(rc != GNUTLS_E_SUCCESS) {
+        failf(data,
+              "error reading X.509 potentially-encrypted key file: %s",
+              gnutls_strerror(rc));
+        return CURLE_SSL_CONNECT_ERROR;
+      }
+#else
+      failf(data, "gnutls lacks support for encrypted key files");
+      return CURLE_SSL_CONNECT_ERROR;
+#endif
+    }
+    else {
+      if(gnutls_certificate_set_x509_key_file(
+           BACKEND->cred,
+           SSL_SET_OPTION(cert),
+           SSL_SET_OPTION(key) ?
+           SSL_SET_OPTION(key) : SSL_SET_OPTION(cert),
+           do_file_type(SSL_SET_OPTION(cert_type)) ) !=
+         GNUTLS_E_SUCCESS) {
+        failf(data, "error reading X.509 key or certificate file");
+        return CURLE_SSL_CONNECT_ERROR;
+      }
+    }
+  }
+
+#ifdef USE_TLS_SRP
+  /* put the credentials to the current session */
+  if(SSL_SET_OPTION(authtype) == CURL_TLSAUTH_SRP) {
+    rc = gnutls_credentials_set(session, GNUTLS_CRD_SRP,
+                                BACKEND->srp_client_cred);
+    if(rc != GNUTLS_E_SUCCESS) {
+      failf(data, "gnutls_credentials_set() failed: %s", gnutls_strerror(rc));
+      return CURLE_SSL_CONNECT_ERROR;
+    }
+  }
+  else
+#endif
+  {
+    rc = gnutls_credentials_set(session, GNUTLS_CRD_CERTIFICATE,
+                                BACKEND->cred);
+    if(rc != GNUTLS_E_SUCCESS) {
+      failf(data, "gnutls_credentials_set() failed: %s", gnutls_strerror(rc));
+      return CURLE_SSL_CONNECT_ERROR;
+    }
+  }
+
+  if(conn->proxy_ssl[sockindex].use) {
+    transport_ptr = conn->proxy_ssl[sockindex].backend->session;
+    gnutls_transport_push = Curl_gtls_push_ssl;
+    gnutls_transport_pull = Curl_gtls_pull_ssl;
+  }
+  else {
+    /* file descriptor for the socket */
+    transport_ptr = &conn->sock[sockindex];
+    gnutls_transport_push = Curl_gtls_push;
+    gnutls_transport_pull = Curl_gtls_pull;
+  }
+
+  /* set the connection handle */
+  gnutls_transport_set_ptr(session, transport_ptr);
+
+  /* register callback functions to send and receive data. */
+  gnutls_transport_set_push_function(session, gnutls_transport_push);
+  gnutls_transport_set_pull_function(session, gnutls_transport_pull);
+
+  /* lowat must be set to zero when using custom push and pull functions. */
+  gnutls_transport_set_lowat(session, 0);
+
+#ifdef HAS_OCSP
+  if(SSL_CONN_CONFIG(verifystatus)) {
+    rc = gnutls_ocsp_status_request_enable_client(session, NULL, 0, NULL);
+    if(rc != GNUTLS_E_SUCCESS) {
+      failf(data, "gnutls_ocsp_status_request_enable_client() failed: %d", rc);
+      return CURLE_SSL_CONNECT_ERROR;
+    }
+  }
+#endif
+
+  /* This might be a reconnect, so we check for a session ID in the cache
+     to speed up things */
+  if(SSL_SET_OPTION(primary.sessionid)) {
+    void *ssl_sessionid;
+    size_t ssl_idsize;
+
+    Curl_ssl_sessionid_lock(conn);
+    if(!Curl_ssl_getsessionid(conn, &ssl_sessionid, &ssl_idsize, sockindex)) {
+      /* we got a session id, use it! */
+      gnutls_session_set_data(session, ssl_sessionid, ssl_idsize);
+
+      /* Informational message */
+      infof(data, "SSL re-using session ID\n");
+    }
+    Curl_ssl_sessionid_unlock(conn);
+  }
+
+  return CURLE_OK;
+}
+
+static CURLcode pkp_pin_peer_pubkey(struct Curl_easy *data,
+                                    gnutls_x509_crt_t cert,
+                                    const char *pinnedpubkey)
+{
+  /* Scratch */
+  size_t len1 = 0, len2 = 0;
+  unsigned char *buff1 = NULL;
+
+  gnutls_pubkey_t key = NULL;
+
+  /* Result is returned to caller */
+  CURLcode result = CURLE_SSL_PINNEDPUBKEYNOTMATCH;
+
+  /* if a path wasn't specified, don't pin */
+  if(NULL == pinnedpubkey)
+    return CURLE_OK;
+
+  if(NULL == cert)
+    return result;
+
+  do {
+    int ret;
+
+    /* Begin Gyrations to get the public key     */
+    gnutls_pubkey_init(&key);
+
+    ret = gnutls_pubkey_import_x509(key, cert, 0);
+    if(ret < 0)
+      break; /* failed */
+
+    ret = gnutls_pubkey_export(key, GNUTLS_X509_FMT_DER, NULL, &len1);
+    if(ret != GNUTLS_E_SHORT_MEMORY_BUFFER || len1 == 0)
+      break; /* failed */
+
+    buff1 = malloc(len1);
+    if(NULL == buff1)
+      break; /* failed */
+
+    len2 = len1;
+
+    ret = gnutls_pubkey_export(key, GNUTLS_X509_FMT_DER, buff1, &len2);
+    if(ret < 0 || len1 != len2)
+      break; /* failed */
+
+    /* End Gyrations */
+
+    /* The one good exit point */
+    result = Curl_pin_peer_pubkey(data, pinnedpubkey, buff1, len1);
+  } while(0);
+
+  if(NULL != key)
+    gnutls_pubkey_deinit(key);
+
+  Curl_safefree(buff1);
+
+  return result;
+}
+
+static Curl_recv gtls_recv;
+static Curl_send gtls_send;
+
+static CURLcode
+gtls_connect_step3(struct connectdata *conn,
+                   int sockindex)
+{
+  unsigned int cert_list_size;
+  const gnutls_datum_t *chainp;
+  unsigned int verify_status = 0;
+  gnutls_x509_crt_t x509_cert, x509_issuer;
+  gnutls_datum_t issuerp;
+  char certbuf[256] = ""; /* big enough? */
+  size_t size;
+  time_t certclock;
+  const char *ptr;
+  struct Curl_easy *data = conn->data;
+  struct ssl_connect_data *connssl = &conn->ssl[sockindex];
+  gnutls_session_t session = BACKEND->session;
+  int rc;
+#ifdef HAS_ALPN
+  gnutls_datum_t proto;
+#endif
+  CURLcode result = CURLE_OK;
+#ifndef CURL_DISABLE_VERBOSE_STRINGS
+  unsigned int algo;
+  unsigned int bits;
+  gnutls_protocol_t version = gnutls_protocol_get_version(session);
+#endif
+  const char * const hostname = SSL_IS_PROXY() ? conn->http_proxy.host.name :
+    conn->host.name;
+
+  /* the name of the cipher suite used, e.g. ECDHE_RSA_AES_256_GCM_SHA384. */
+  ptr = gnutls_cipher_suite_get_name(gnutls_kx_get(session),
+                                     gnutls_cipher_get(session),
+                                     gnutls_mac_get(session));
+
+  infof(data, "SSL connection using %s / %s\n",
+        gnutls_protocol_get_name(version), ptr);
+
+  /* This function will return the peer's raw certificate (chain) as sent by
+     the peer. These certificates are in raw format (DER encoded for
+     X.509). In case of a X.509 then a certificate list may be present. The
+     first certificate in the list is the peer's certificate, following the
+     issuer's certificate, then the issuer's issuer etc. */
+
+  chainp = gnutls_certificate_get_peers(session, &cert_list_size);
+  if(!chainp) {
+    if(SSL_CONN_CONFIG(verifypeer) ||
+       SSL_CONN_CONFIG(verifyhost) ||
+       SSL_SET_OPTION(issuercert)) {
+#ifdef USE_TLS_SRP
+      if(SSL_SET_OPTION(authtype) == CURL_TLSAUTH_SRP
+         && SSL_SET_OPTION(username) != NULL
+         && !SSL_CONN_CONFIG(verifypeer)
+         && gnutls_cipher_get(session)) {
+        /* no peer cert, but auth is ok if we have SRP user and cipher and no
+           peer verify */
+      }
+      else {
+#endif
+        failf(data, "failed to get server cert");
+        return CURLE_PEER_FAILED_VERIFICATION;
+#ifdef USE_TLS_SRP
+      }
+#endif
+    }
+    infof(data, "\t common name: WARNING couldn't obtain\n");
+  }
+
+  if(data->set.ssl.certinfo && chainp) {
+    unsigned int i;
+
+    result = Curl_ssl_init_certinfo(data, cert_list_size);
+    if(result)
+      return result;
+
+    for(i = 0; i < cert_list_size; i++) {
+      const char *beg = (const char *) chainp[i].data;
+      const char *end = beg + chainp[i].size;
+
+      result = Curl_extract_certinfo(conn, i, beg, end);
+      if(result)
+        return result;
+    }
+  }
+
+  if(SSL_CONN_CONFIG(verifypeer)) {
+    /* This function will try to verify the peer's certificate and return its
+       status (trusted, invalid etc.). The value of status should be one or
+       more of the gnutls_certificate_status_t enumerated elements bitwise
+       or'd. To avoid denial of service attacks some default upper limits
+       regarding the certificate key size and chain size are set. To override
+       them use gnutls_certificate_set_verify_limits(). */
+
+    rc = gnutls_certificate_verify_peers2(session, &verify_status);
+    if(rc < 0) {
+      failf(data, "server cert verify failed: %d", rc);
+      return CURLE_SSL_CONNECT_ERROR;
+    }
+
+    /* verify_status is a bitmask of gnutls_certificate_status bits */
+    if(verify_status & GNUTLS_CERT_INVALID) {
+      if(SSL_CONN_CONFIG(verifypeer)) {
+        failf(data, "server certificate verification failed. CAfile: %s "
+              "CRLfile: %s", SSL_CONN_CONFIG(CAfile) ? SSL_CONN_CONFIG(CAfile):
+              "none",
+              SSL_SET_OPTION(CRLfile)?SSL_SET_OPTION(CRLfile):"none");
+        return CURLE_PEER_FAILED_VERIFICATION;
+      }
+      else
+        infof(data, "\t server certificate verification FAILED\n");
+    }
+    else
+      infof(data, "\t server certificate verification OK\n");
+  }
+  else
+    infof(data, "\t server certificate verification SKIPPED\n");
+
+#ifdef HAS_OCSP
+  if(SSL_CONN_CONFIG(verifystatus)) {
+    if(gnutls_ocsp_status_request_is_checked(session, 0) == 0) {
+      gnutls_datum_t status_request;
+      gnutls_ocsp_resp_t ocsp_resp;
+
+      gnutls_ocsp_cert_status_t status;
+      gnutls_x509_crl_reason_t reason;
+
+      rc = gnutls_ocsp_status_request_get(session, &status_request);
+
+      infof(data, "\t server certificate status verification FAILED\n");
+
+      if(rc == GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE) {
+        failf(data, "No OCSP response received");
+        return CURLE_SSL_INVALIDCERTSTATUS;
+      }
+
+      if(rc < 0) {
+        failf(data, "Invalid OCSP response received");
+        return CURLE_SSL_INVALIDCERTSTATUS;
+      }
+
+      gnutls_ocsp_resp_init(&ocsp_resp);
+
+      rc = gnutls_ocsp_resp_import(ocsp_resp, &status_request);
+      if(rc < 0) {
+        failf(data, "Invalid OCSP response received");
+        return CURLE_SSL_INVALIDCERTSTATUS;
+      }
+
+      (void)gnutls_ocsp_resp_get_single(ocsp_resp, 0, NULL, NULL, NULL, NULL,
+                                        &status, NULL, NULL, NULL, &reason);
+
+      switch(status) {
+      case GNUTLS_OCSP_CERT_GOOD:
+        break;
+
+      case GNUTLS_OCSP_CERT_REVOKED: {
+        const char *crl_reason;
+
+        switch(reason) {
+          default:
+          case GNUTLS_X509_CRLREASON_UNSPECIFIED:
+            crl_reason = "unspecified reason";
+            break;
+
+          case GNUTLS_X509_CRLREASON_KEYCOMPROMISE:
+            crl_reason = "private key compromised";
+            break;
+
+          case GNUTLS_X509_CRLREASON_CACOMPROMISE:
+            crl_reason = "CA compromised";
+            break;
+
+          case GNUTLS_X509_CRLREASON_AFFILIATIONCHANGED:
+            crl_reason = "affiliation has changed";
+            break;
+
+          case GNUTLS_X509_CRLREASON_SUPERSEDED:
+            crl_reason = "certificate superseded";
+            break;
+
+          case GNUTLS_X509_CRLREASON_CESSATIONOFOPERATION:
+            crl_reason = "operation has ceased";
+            break;
+
+          case GNUTLS_X509_CRLREASON_CERTIFICATEHOLD:
+            crl_reason = "certificate is on hold";
+            break;
+
+          case GNUTLS_X509_CRLREASON_REMOVEFROMCRL:
+            crl_reason = "will be removed from delta CRL";
+            break;
+
+          case GNUTLS_X509_CRLREASON_PRIVILEGEWITHDRAWN:
+            crl_reason = "privilege withdrawn";
+            break;
+
+          case GNUTLS_X509_CRLREASON_AACOMPROMISE:
+            crl_reason = "AA compromised";
+            break;
+        }
+
+        failf(data, "Server certificate was revoked: %s", crl_reason);
+        break;
+      }
+
+      default:
+      case GNUTLS_OCSP_CERT_UNKNOWN:
+        failf(data, "Server certificate status is unknown");
+        break;
+      }
+
+      gnutls_ocsp_resp_deinit(ocsp_resp);
+
+      return CURLE_SSL_INVALIDCERTSTATUS;
+    }
+    else
+      infof(data, "\t server certificate status verification OK\n");
+  }
+  else
+    infof(data, "\t server certificate status verification SKIPPED\n");
+#endif
+
+  /* initialize an X.509 certificate structure. */
+  gnutls_x509_crt_init(&x509_cert);
+
+  if(chainp)
+    /* convert the given DER or PEM encoded Certificate to the native
+       gnutls_x509_crt_t format */
+    gnutls_x509_crt_import(x509_cert, chainp, GNUTLS_X509_FMT_DER);
+
+  if(SSL_SET_OPTION(issuercert)) {
+    gnutls_x509_crt_init(&x509_issuer);
+    issuerp = load_file(SSL_SET_OPTION(issuercert));
+    gnutls_x509_crt_import(x509_issuer, &issuerp, GNUTLS_X509_FMT_PEM);
+    rc = gnutls_x509_crt_check_issuer(x509_cert, x509_issuer);
+    gnutls_x509_crt_deinit(x509_issuer);
+    unload_file(issuerp);
+    if(rc <= 0) {
+      failf(data, "server certificate issuer check failed (IssuerCert: %s)",
+            SSL_SET_OPTION(issuercert)?SSL_SET_OPTION(issuercert):"none");
+      gnutls_x509_crt_deinit(x509_cert);
+      return CURLE_SSL_ISSUER_ERROR;
+    }
+    infof(data, "\t server certificate issuer check OK (Issuer Cert: %s)\n",
+          SSL_SET_OPTION(issuercert)?SSL_SET_OPTION(issuercert):"none");
+  }
+
+  size = sizeof(certbuf);
+  rc = gnutls_x509_crt_get_dn_by_oid(x509_cert, GNUTLS_OID_X520_COMMON_NAME,
+                                     0, /* the first and only one */
+                                     FALSE,
+                                     certbuf,
+                                     &size);
+  if(rc) {
+    infof(data, "error fetching CN from cert:%s\n",
+          gnutls_strerror(rc));
+  }
+
+  /* This function will check if the given certificate's subject matches the
+     given hostname. This is a basic implementation of the matching described
+     in RFC2818 (HTTPS), which takes into account wildcards, and the subject
+     alternative name PKIX extension. Returns non zero on success, and zero on
+     failure. */
+  rc = gnutls_x509_crt_check_hostname(x509_cert, hostname);
+#if GNUTLS_VERSION_NUMBER < 0x030306
+  /* Before 3.3.6, gnutls_x509_crt_check_hostname() didn't check IP
+     addresses. */
+  if(!rc) {
+#ifdef ENABLE_IPV6
+    #define use_addr in6_addr
+#else
+    #define use_addr in_addr
+#endif
+    unsigned char addrbuf[sizeof(struct use_addr)];
+    size_t addrlen = 0;
+
+    if(Curl_inet_pton(AF_INET, hostname, addrbuf) > 0)
+      addrlen = 4;
+#ifdef ENABLE_IPV6
+    else if(Curl_inet_pton(AF_INET6, hostname, addrbuf) > 0)
+      addrlen = 16;
+#endif
+
+    if(addrlen) {
+      unsigned char certaddr[sizeof(struct use_addr)];
+      int i;
+
+      for(i = 0; ; i++) {
+        size_t certaddrlen = sizeof(certaddr);
+        int ret = gnutls_x509_crt_get_subject_alt_name(x509_cert, i, certaddr,
+                                                       &certaddrlen, NULL);
+        /* If this happens, it wasn't an IP address. */
+        if(ret == GNUTLS_E_SHORT_MEMORY_BUFFER)
+          continue;
+        if(ret < 0)
+          break;
+        if(ret != GNUTLS_SAN_IPADDRESS)
+          continue;
+        if(certaddrlen == addrlen && !memcmp(addrbuf, certaddr, addrlen)) {
+          rc = 1;
+          break;
+        }
+      }
+    }
+  }
+#endif
+  if(!rc) {
+    const char * const dispname = SSL_IS_PROXY() ?
+      conn->http_proxy.host.dispname : conn->host.dispname;
+
+    if(SSL_CONN_CONFIG(verifyhost)) {
+      failf(data, "SSL: certificate subject name (%s) does not match "
+            "target host name '%s'", certbuf, dispname);
+      gnutls_x509_crt_deinit(x509_cert);
+      return CURLE_PEER_FAILED_VERIFICATION;
+    }
+    else
+      infof(data, "\t common name: %s (does not match '%s')\n",
+            certbuf, dispname);
+  }
+  else
+    infof(data, "\t common name: %s (matched)\n", certbuf);
+
+  /* Check for time-based validity */
+  certclock = gnutls_x509_crt_get_expiration_time(x509_cert);
+
+  if(certclock == (time_t)-1) {
+    if(SSL_CONN_CONFIG(verifypeer)) {
+      failf(data, "server cert expiration date verify failed");
+      gnutls_x509_crt_deinit(x509_cert);
+      return CURLE_SSL_CONNECT_ERROR;
+    }
+    else
+      infof(data, "\t server certificate expiration date verify FAILED\n");
+  }
+  else {
+    if(certclock < time(NULL)) {
+      if(SSL_CONN_CONFIG(verifypeer)) {
+        failf(data, "server certificate expiration date has passed.");
+        gnutls_x509_crt_deinit(x509_cert);
+        return CURLE_PEER_FAILED_VERIFICATION;
+      }
+      else
+        infof(data, "\t server certificate expiration date FAILED\n");
+    }
+    else
+      infof(data, "\t server certificate expiration date OK\n");
+  }
+
+  certclock = gnutls_x509_crt_get_activation_time(x509_cert);
+
+  if(certclock == (time_t)-1) {
+    if(SSL_CONN_CONFIG(verifypeer)) {
+      failf(data, "server cert activation date verify failed");
+      gnutls_x509_crt_deinit(x509_cert);
+      return CURLE_SSL_CONNECT_ERROR;
+    }
+    else
+      infof(data, "\t server certificate activation date verify FAILED\n");
+  }
+  else {
+    if(certclock > time(NULL)) {
+      if(SSL_CONN_CONFIG(verifypeer)) {
+        failf(data, "server certificate not activated yet.");
+        gnutls_x509_crt_deinit(x509_cert);
+        return CURLE_PEER_FAILED_VERIFICATION;
+      }
+      else
+        infof(data, "\t server certificate activation date FAILED\n");
+    }
+    else
+      infof(data, "\t server certificate activation date OK\n");
+  }
+
+  ptr = SSL_IS_PROXY() ? data->set.str[STRING_SSL_PINNEDPUBLICKEY_PROXY] :
+        data->set.str[STRING_SSL_PINNEDPUBLICKEY_ORIG];
+  if(ptr) {
+    result = pkp_pin_peer_pubkey(data, x509_cert, ptr);
+    if(result != CURLE_OK) {
+      failf(data, "SSL: public key does not match pinned public key!");
+      gnutls_x509_crt_deinit(x509_cert);
+      return result;
+    }
+  }
+
+  /* Show:
+
+  - subject
+  - start date
+  - expire date
+  - common name
+  - issuer
+
+  */
+
+#ifndef CURL_DISABLE_VERBOSE_STRINGS
+  /* public key algorithm's parameters */
+  algo = gnutls_x509_crt_get_pk_algorithm(x509_cert, &bits);
+  infof(data, "\t certificate public key: %s\n",
+        gnutls_pk_algorithm_get_name(algo));
+
+  /* version of the X.509 certificate. */
+  infof(data, "\t certificate version: #%d\n",
+        gnutls_x509_crt_get_version(x509_cert));
+
+
+  size = sizeof(certbuf);
+  gnutls_x509_crt_get_dn(x509_cert, certbuf, &size);
+  infof(data, "\t subject: %s\n", certbuf);
+
+  certclock = gnutls_x509_crt_get_activation_time(x509_cert);
+  showtime(data, "start date", certclock);
+
+  certclock = gnutls_x509_crt_get_expiration_time(x509_cert);
+  showtime(data, "expire date", certclock);
+
+  size = sizeof(certbuf);
+  gnutls_x509_crt_get_issuer_dn(x509_cert, certbuf, &size);
+  infof(data, "\t issuer: %s\n", certbuf);
+#endif
+
+  gnutls_x509_crt_deinit(x509_cert);
+
+#ifdef HAS_ALPN
+  if(conn->bits.tls_enable_alpn) {
+    rc = gnutls_alpn_get_selected_protocol(session, &proto);
+    if(rc == 0) {
+      infof(data, "ALPN, server accepted to use %.*s\n", proto.size,
+          proto.data);
+
+#ifdef USE_NGHTTP2
+      if(proto.size == NGHTTP2_PROTO_VERSION_ID_LEN &&
+         !memcmp(NGHTTP2_PROTO_VERSION_ID, proto.data,
+                 NGHTTP2_PROTO_VERSION_ID_LEN)) {
+        conn->negnpn = CURL_HTTP_VERSION_2;
+      }
+      else
+#endif
+      if(proto.size == ALPN_HTTP_1_1_LENGTH &&
+         !memcmp(ALPN_HTTP_1_1, proto.data, ALPN_HTTP_1_1_LENGTH)) {
+        conn->negnpn = CURL_HTTP_VERSION_1_1;
+      }
+    }
+    else
+      infof(data, "ALPN, server did not agree to a protocol\n");
+
+    Curl_multiuse_state(conn, conn->negnpn == CURL_HTTP_VERSION_2 ?
+                        BUNDLE_MULTIPLEX : BUNDLE_NO_MULTIUSE);
+  }
+#endif
+
+  conn->ssl[sockindex].state = ssl_connection_complete;
+  conn->recv[sockindex] = gtls_recv;
+  conn->send[sockindex] = gtls_send;
+
+  if(SSL_SET_OPTION(primary.sessionid)) {
+    /* we always unconditionally get the session id here, as even if we
+       already got it from the cache and asked to use it in the connection, it
+       might've been rejected and then a new one is in use now and we need to
+       detect that. */
+    void *connect_sessionid;
+    size_t connect_idsize = 0;
+
+    /* get the session ID data size */
+    gnutls_session_get_data(session, NULL, &connect_idsize);
+    connect_sessionid = malloc(connect_idsize); /* get a buffer for it */
+
+    if(connect_sessionid) {
+      bool incache;
+      void *ssl_sessionid;
+
+      /* extract session ID to the allocated buffer */
+      gnutls_session_get_data(session, connect_sessionid, &connect_idsize);
+
+      Curl_ssl_sessionid_lock(conn);
+      incache = !(Curl_ssl_getsessionid(conn, &ssl_sessionid, NULL,
+                                        sockindex));
+      if(incache) {
+        /* there was one before in the cache, so instead of risking that the
+           previous one was rejected, we just kill that and store the new */
+        Curl_ssl_delsessionid(conn, ssl_sessionid);
+      }
+
+      /* store this session id */
+      result = Curl_ssl_addsessionid(conn, connect_sessionid, connect_idsize,
+                                     sockindex);
+      Curl_ssl_sessionid_unlock(conn);
+      if(result) {
+        free(connect_sessionid);
+        result = CURLE_OUT_OF_MEMORY;
+      }
+    }
+    else
+      result = CURLE_OUT_OF_MEMORY;
+  }
+
+  return result;
+}
+
+
+/*
+ * This function is called after the TCP connect has completed. Setup the TLS
+ * layer and do all necessary magic.
+ */
+/* We use connssl->connecting_state to keep track of the connection status;
+   there are three states: 'ssl_connect_1' (not started yet or complete),
+   'ssl_connect_2_reading' (waiting for data from server), and
+   'ssl_connect_2_writing' (waiting to be able to write).
+ */
+static CURLcode
+gtls_connect_common(struct connectdata *conn,
+                    int sockindex,
+                    bool nonblocking,
+                    bool *done)
+{
+  int rc;
+  struct ssl_connect_data *connssl = &conn->ssl[sockindex];
+
+  /* Initiate the connection, if not already done */
+  if(ssl_connect_1 == connssl->connecting_state) {
+    rc = gtls_connect_step1(conn, sockindex);
+    if(rc)
+      return rc;
+  }
+
+  rc = handshake(conn, sockindex, TRUE, nonblocking);
+  if(rc)
+    /* handshake() sets its own error message with failf() */
+    return rc;
+
+  /* Finish connecting once the handshake is done */
+  if(ssl_connect_1 == connssl->connecting_state) {
+    rc = gtls_connect_step3(conn, sockindex);
+    if(rc)
+      return rc;
+  }
+
+  *done = ssl_connect_1 == connssl->connecting_state;
+
+  return CURLE_OK;
+}
+
+static CURLcode Curl_gtls_connect_nonblocking(struct connectdata *conn,
+                                              int sockindex, bool *done)
+{
+  return gtls_connect_common(conn, sockindex, TRUE, done);
+}
+
+static CURLcode Curl_gtls_connect(struct connectdata *conn, int sockindex)
+{
+  CURLcode result;
+  bool done = FALSE;
+
+  result = gtls_connect_common(conn, sockindex, FALSE, &done);
+  if(result)
+    return result;
+
+  DEBUGASSERT(done);
+
+  return CURLE_OK;
+}
+
+static bool Curl_gtls_data_pending(const struct connectdata *conn,
+                                   int connindex)
+{
+  const struct ssl_connect_data *connssl = &conn->ssl[connindex];
+  bool res = FALSE;
+  if(BACKEND->session &&
+     0 != gnutls_record_check_pending(BACKEND->session))
+    res = TRUE;
+
+  connssl = &conn->proxy_ssl[connindex];
+  if(BACKEND->session &&
+     0 != gnutls_record_check_pending(BACKEND->session))
+    res = TRUE;
+
+  return res;
+}
+
+static ssize_t gtls_send(struct connectdata *conn,
+                         int sockindex,
+                         const void *mem,
+                         size_t len,
+                         CURLcode *curlcode)
+{
+  struct ssl_connect_data *connssl = &conn->ssl[sockindex];
+  ssize_t rc = gnutls_record_send(BACKEND->session, mem, len);
+
+  if(rc < 0) {
+    *curlcode = (rc == GNUTLS_E_AGAIN)
+      ? CURLE_AGAIN
+      : CURLE_SEND_ERROR;
+
+    rc = -1;
+  }
+
+  return rc;
+}
+
+static void close_one(struct ssl_connect_data *connssl)
+{
+  if(BACKEND->session) {
+    gnutls_bye(BACKEND->session, GNUTLS_SHUT_RDWR);
+    gnutls_deinit(BACKEND->session);
+    BACKEND->session = NULL;
+  }
+  if(BACKEND->cred) {
+    gnutls_certificate_free_credentials(BACKEND->cred);
+    BACKEND->cred = NULL;
+  }
+#ifdef USE_TLS_SRP
+  if(BACKEND->srp_client_cred) {
+    gnutls_srp_free_client_credentials(BACKEND->srp_client_cred);
+    BACKEND->srp_client_cred = NULL;
+  }
+#endif
+}
+
+static void Curl_gtls_close(struct connectdata *conn, int sockindex)
+{
+  close_one(&conn->ssl[sockindex]);
+  close_one(&conn->proxy_ssl[sockindex]);
+}
+
+/*
+ * This function is called to shut down the SSL layer but keep the
+ * socket open (CCC - Clear Command Channel)
+ */
+static int Curl_gtls_shutdown(struct connectdata *conn, int sockindex)
+{
+  struct ssl_connect_data *connssl = &conn->ssl[sockindex];
+  int retval = 0;
+  struct Curl_easy *data = conn->data;
+
+#ifndef CURL_DISABLE_FTP
+  /* This has only been tested on the proftpd server, and the mod_tls code
+     sends a close notify alert without waiting for a close notify alert in
+     response. Thus we wait for a close notify alert from the server, but
+     we do not send one. Let's hope other servers do the same... */
+
+  if(data->set.ftp_ccc == CURLFTPSSL_CCC_ACTIVE)
+      gnutls_bye(BACKEND->session, GNUTLS_SHUT_WR);
+#endif
+
+  if(BACKEND->session) {
+    ssize_t result;
+    bool done = FALSE;
+    char buf[120];
+
+    while(!done) {
+      int what = SOCKET_READABLE(conn->sock[sockindex],
+                                 SSL_SHUTDOWN_TIMEOUT);
+      if(what > 0) {
+        /* Something to read, let's do it and hope that it is the close
+           notify alert from the server */
+        result = gnutls_record_recv(BACKEND->session,
+                                    buf, sizeof(buf));
+        switch(result) {
+        case 0:
+          /* This is the expected response. There was no data but only
+             the close notify alert */
+          done = TRUE;
+          break;
+        case GNUTLS_E_AGAIN:
+        case GNUTLS_E_INTERRUPTED:
+          infof(data, "GNUTLS_E_AGAIN || GNUTLS_E_INTERRUPTED\n");
+          break;
+        default:
+          retval = -1;
+          done = TRUE;
+          break;
+        }
+      }
+      else if(0 == what) {
+        /* timeout */
+        failf(data, "SSL shutdown timeout");
+        done = TRUE;
+      }
+      else {
+        /* anything that gets here is fatally bad */
+        failf(data, "select/poll on SSL socket, errno: %d", SOCKERRNO);
+        retval = -1;
+        done = TRUE;
+      }
+    }
+    gnutls_deinit(BACKEND->session);
+  }
+  gnutls_certificate_free_credentials(BACKEND->cred);
+
+#ifdef USE_TLS_SRP
+  if(SSL_SET_OPTION(authtype) == CURL_TLSAUTH_SRP
+     && SSL_SET_OPTION(username) != NULL)
+    gnutls_srp_free_client_credentials(BACKEND->srp_client_cred);
+#endif
+
+  BACKEND->cred = NULL;
+  BACKEND->session = NULL;
+
+  return retval;
+}
+
+static ssize_t gtls_recv(struct connectdata *conn, /* connection data */
+                         int num,                  /* socketindex */
+                         char *buf,                /* store read data here */
+                         size_t buffersize,        /* max amount to read */
+                         CURLcode *curlcode)
+{
+  struct ssl_connect_data *connssl = &conn->ssl[num];
+  ssize_t ret;
+
+  ret = gnutls_record_recv(BACKEND->session, buf, buffersize);
+  if((ret == GNUTLS_E_AGAIN) || (ret == GNUTLS_E_INTERRUPTED)) {
+    *curlcode = CURLE_AGAIN;
+    return -1;
+  }
+
+  if(ret == GNUTLS_E_REHANDSHAKE) {
+    /* BLOCKING call, this is bad but a work-around for now. Fixing this "the
+       proper way" takes a whole lot of work. */
+    CURLcode result = handshake(conn, num, FALSE, FALSE);
+    if(result)
+      /* handshake() writes error message on its own */
+      *curlcode = result;
+    else
+      *curlcode = CURLE_AGAIN; /* then return as if this was a wouldblock */
+    return -1;
+  }
+
+  if(ret < 0) {
+    failf(conn->data, "GnuTLS recv error (%d): %s",
+
+          (int)ret, gnutls_strerror((int)ret));
+    *curlcode = CURLE_RECV_ERROR;
+    return -1;
+  }
+
+  return ret;
+}
+
+static void Curl_gtls_session_free(void *ptr)
+{
+  free(ptr);
+}
+
+static size_t Curl_gtls_version(char *buffer, size_t size)
+{
+  return msnprintf(buffer, size, "GnuTLS/%s", gnutls_check_version(NULL));
+}
+
+#ifndef USE_GNUTLS_NETTLE
+static int Curl_gtls_seed(struct Curl_easy *data)
+{
+  /* we have the "SSL is seeded" boolean static to prevent multiple
+     time-consuming seedings in vain */
+  static bool ssl_seeded = FALSE;
+
+  /* Quickly add a bit of entropy */
+  gcry_fast_random_poll();
+
+  if(!ssl_seeded || data->set.str[STRING_SSL_RANDOM_FILE] ||
+     data->set.str[STRING_SSL_EGDSOCKET]) {
+    ssl_seeded = TRUE;
+  }
+  return 0;
+}
+#endif
+
+/* data might be NULL! */
+static CURLcode Curl_gtls_random(struct Curl_easy *data,
+                                 unsigned char *entropy, size_t length)
+{
+#if defined(USE_GNUTLS_NETTLE)
+  int rc;
+  (void)data;
+  rc = gnutls_rnd(GNUTLS_RND_RANDOM, entropy, length);
+  return rc?CURLE_FAILED_INIT:CURLE_OK;
+#elif defined(USE_GNUTLS)
+  if(data)
+    Curl_gtls_seed(data); /* Initiate the seed if not already done */
+  gcry_randomize(entropy, length, GCRY_STRONG_RANDOM);
+#endif
+  return CURLE_OK;
+}
+
+static CURLcode Curl_gtls_md5sum(unsigned char *tmp, /* input */
+                                 size_t tmplen,
+                                 unsigned char *md5sum, /* output */
+                                 size_t md5len)
+{
+#if defined(USE_GNUTLS_NETTLE)
+  struct md5_ctx MD5pw;
+  md5_init(&MD5pw);
+  md5_update(&MD5pw, (unsigned int)tmplen, tmp);
+  md5_digest(&MD5pw, (unsigned int)md5len, md5sum);
+#elif defined(USE_GNUTLS)
+  gcry_md_hd_t MD5pw;
+  gcry_md_open(&MD5pw, GCRY_MD_MD5, 0);
+  gcry_md_write(MD5pw, tmp, tmplen);
+  memcpy(md5sum, gcry_md_read(MD5pw, 0), md5len);
+  gcry_md_close(MD5pw);
+#endif
+  return CURLE_OK;
+}
+
+static CURLcode Curl_gtls_sha256sum(const unsigned char *tmp, /* input */
+                                size_t tmplen,
+                                unsigned char *sha256sum, /* output */
+                                size_t sha256len)
+{
+#if defined(USE_GNUTLS_NETTLE)
+  struct sha256_ctx SHA256pw;
+  sha256_init(&SHA256pw);
+  sha256_update(&SHA256pw, (unsigned int)tmplen, tmp);
+  sha256_digest(&SHA256pw, (unsigned int)sha256len, sha256sum);
+#elif defined(USE_GNUTLS)
+  gcry_md_hd_t SHA256pw;
+  gcry_md_open(&SHA256pw, GCRY_MD_SHA256, 0);
+  gcry_md_write(SHA256pw, tmp, tmplen);
+  memcpy(sha256sum, gcry_md_read(SHA256pw, 0), sha256len);
+  gcry_md_close(SHA256pw);
+#endif
+  return CURLE_OK;
+}
+
+static bool Curl_gtls_cert_status_request(void)
+{
+#ifdef HAS_OCSP
+  return TRUE;
+#else
+  return FALSE;
+#endif
+}
+
+static void *Curl_gtls_get_internals(struct ssl_connect_data *connssl,
+                                     CURLINFO info UNUSED_PARAM)
+{
+  (void)info;
+  return BACKEND->session;
+}
+
+const struct Curl_ssl Curl_ssl_gnutls = {
+  { CURLSSLBACKEND_GNUTLS, "gnutls" }, /* info */
+
+  SSLSUPP_CA_PATH  |
+  SSLSUPP_CERTINFO |
+  SSLSUPP_PINNEDPUBKEY |
+  SSLSUPP_HTTPS_PROXY,
+
+  sizeof(struct ssl_backend_data),
+
+  Curl_gtls_init,                /* init */
+  Curl_gtls_cleanup,             /* cleanup */
+  Curl_gtls_version,             /* version */
+  Curl_none_check_cxn,           /* check_cxn */
+  Curl_gtls_shutdown,            /* shutdown */
+  Curl_gtls_data_pending,        /* data_pending */
+  Curl_gtls_random,              /* random */
+  Curl_gtls_cert_status_request, /* cert_status_request */
+  Curl_gtls_connect,             /* connect */
+  Curl_gtls_connect_nonblocking, /* connect_nonblocking */
+  Curl_gtls_get_internals,       /* get_internals */
+  Curl_gtls_close,               /* close_one */
+  Curl_none_close_all,           /* close_all */
+  Curl_gtls_session_free,        /* session_free */
+  Curl_none_set_engine,          /* set_engine */
+  Curl_none_set_engine_default,  /* set_engine_default */
+  Curl_none_engines_list,        /* engines_list */
+  Curl_none_false_start,         /* false_start */
+  Curl_gtls_md5sum,              /* md5sum */
+  Curl_gtls_sha256sum            /* sha256sum */
+};
+
+#endif /* USE_GNUTLS */