--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mupdf-source/thirdparty/curl/lib/vtls/gskit.c	Mon Sep 15 11:43:07 2025 +0200
@@ -0,0 +1,1381 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 1998 - 2018, 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"
+
+#ifdef USE_GSKIT
+
+#include <gskssl.h>
+#include <qsoasync.h>
+
+/* Some symbols are undefined/unsupported on OS400 versions < V7R1. */
+#ifndef GSK_SSL_EXTN_SERVERNAME_REQUEST
+#define GSK_SSL_EXTN_SERVERNAME_REQUEST         230
+#endif
+
+#ifndef GSK_TLSV10_CIPHER_SPECS
+#define GSK_TLSV10_CIPHER_SPECS                 236
+#endif
+
+#ifndef GSK_TLSV11_CIPHER_SPECS
+#define GSK_TLSV11_CIPHER_SPECS                 237
+#endif
+
+#ifndef GSK_TLSV12_CIPHER_SPECS
+#define GSK_TLSV12_CIPHER_SPECS                 238
+#endif
+
+#ifndef GSK_PROTOCOL_TLSV11
+#define GSK_PROTOCOL_TLSV11                     437
+#endif
+
+#ifndef GSK_PROTOCOL_TLSV12
+#define GSK_PROTOCOL_TLSV12                     438
+#endif
+
+#ifndef GSK_FALSE
+#define GSK_FALSE                               0
+#endif
+
+#ifndef GSK_TRUE
+#define GSK_TRUE                                1
+#endif
+
+
+#include <limits.h>
+
+#include <curl/curl.h>
+#include "urldata.h"
+#include "sendf.h"
+#include "gskit.h"
+#include "vtls.h"
+#include "connect.h" /* for the connect timeout */
+#include "select.h"
+#include "strcase.h"
+#include "x509asn1.h"
+#include "curl_printf.h"
+
+#include "curl_memory.h"
+/* The last #include file should be: */
+#include "memdebug.h"
+
+
+/* Directions. */
+#define SOS_READ        0x01
+#define SOS_WRITE       0x02
+
+/* SSL version flags. */
+#define CURL_GSKPROTO_SSLV2     0
+#define CURL_GSKPROTO_SSLV2_MASK        (1 << CURL_GSKPROTO_SSLV2)
+#define CURL_GSKPROTO_SSLV3     1
+#define CURL_GSKPROTO_SSLV3_MASK        (1 << CURL_GSKPROTO_SSLV3)
+#define CURL_GSKPROTO_TLSV10    2
+#define CURL_GSKPROTO_TLSV10_MASK        (1 << CURL_GSKPROTO_TLSV10)
+#define CURL_GSKPROTO_TLSV11    3
+#define CURL_GSKPROTO_TLSV11_MASK        (1 << CURL_GSKPROTO_TLSV11)
+#define CURL_GSKPROTO_TLSV12    4
+#define CURL_GSKPROTO_TLSV12_MASK        (1 << CURL_GSKPROTO_TLSV12)
+#define CURL_GSKPROTO_LAST      5
+
+struct ssl_backend_data {
+  gsk_handle handle;
+  int iocport;
+  int localfd;
+  int remotefd;
+};
+
+#define BACKEND connssl->backend
+
+/* Supported ciphers. */
+typedef struct {
+  const char *name;            /* Cipher name. */
+  const char *gsktoken;        /* Corresponding token for GSKit String. */
+  unsigned int versions;       /* SSL version flags. */
+}  gskit_cipher;
+
+static const gskit_cipher  ciphertable[] = {
+  { "null-md5",         "01",
+      CURL_GSKPROTO_SSLV3_MASK | CURL_GSKPROTO_TLSV10_MASK |
+      CURL_GSKPROTO_TLSV11_MASK | CURL_GSKPROTO_TLSV12_MASK },
+  { "null-sha",         "02",
+      CURL_GSKPROTO_SSLV3_MASK | CURL_GSKPROTO_TLSV10_MASK |
+      CURL_GSKPROTO_TLSV11_MASK | CURL_GSKPROTO_TLSV12_MASK },
+  { "exp-rc4-md5",      "03",
+      CURL_GSKPROTO_SSLV3_MASK | CURL_GSKPROTO_TLSV10_MASK },
+  { "rc4-md5",          "04",
+      CURL_GSKPROTO_SSLV3_MASK | CURL_GSKPROTO_TLSV10_MASK |
+      CURL_GSKPROTO_TLSV11_MASK | CURL_GSKPROTO_TLSV12_MASK },
+  { "rc4-sha",          "05",
+      CURL_GSKPROTO_SSLV3_MASK | CURL_GSKPROTO_TLSV10_MASK |
+      CURL_GSKPROTO_TLSV11_MASK | CURL_GSKPROTO_TLSV12_MASK },
+  { "exp-rc2-cbc-md5",  "06",
+      CURL_GSKPROTO_SSLV3_MASK | CURL_GSKPROTO_TLSV10_MASK },
+  { "exp-des-cbc-sha",  "09",
+      CURL_GSKPROTO_SSLV3_MASK | CURL_GSKPROTO_TLSV10_MASK |
+      CURL_GSKPROTO_TLSV11_MASK },
+  { "des-cbc3-sha",     "0A",
+      CURL_GSKPROTO_SSLV3_MASK | CURL_GSKPROTO_TLSV10_MASK |
+      CURL_GSKPROTO_TLSV11_MASK | CURL_GSKPROTO_TLSV12_MASK },
+  { "aes128-sha",       "2F",
+      CURL_GSKPROTO_TLSV10_MASK | CURL_GSKPROTO_TLSV11_MASK |
+      CURL_GSKPROTO_TLSV12_MASK },
+  { "aes256-sha",       "35",
+      CURL_GSKPROTO_TLSV10_MASK | CURL_GSKPROTO_TLSV11_MASK |
+      CURL_GSKPROTO_TLSV12_MASK },
+  { "null-sha256",      "3B",   CURL_GSKPROTO_TLSV12_MASK },
+  { "aes128-sha256",    "3C",   CURL_GSKPROTO_TLSV12_MASK },
+  { "aes256-sha256",    "3D",   CURL_GSKPROTO_TLSV12_MASK },
+  { "aes128-gcm-sha256",
+                        "9C",   CURL_GSKPROTO_TLSV12_MASK },
+  { "aes256-gcm-sha384",
+                        "9D",   CURL_GSKPROTO_TLSV12_MASK },
+  { "rc4-md5",          "1",    CURL_GSKPROTO_SSLV2_MASK },
+  { "exp-rc4-md5",      "2",    CURL_GSKPROTO_SSLV2_MASK },
+  { "rc2-md5",          "3",    CURL_GSKPROTO_SSLV2_MASK },
+  { "exp-rc2-md5",      "4",    CURL_GSKPROTO_SSLV2_MASK },
+  { "des-cbc-md5",      "6",    CURL_GSKPROTO_SSLV2_MASK },
+  { "des-cbc3-md5",     "7",    CURL_GSKPROTO_SSLV2_MASK },
+  { (const char *) NULL, (const char *) NULL, 0       }
+};
+
+
+static bool is_separator(char c)
+{
+  /* Return whether character is a cipher list separator. */
+  switch(c) {
+  case ' ':
+  case '\t':
+  case ':':
+  case ',':
+  case ';':
+    return true;
+  }
+  return false;
+}
+
+
+static CURLcode gskit_status(struct Curl_easy *data, int rc,
+                             const char *procname, CURLcode defcode)
+{
+  /* Process GSKit status and map it to a CURLcode. */
+  switch(rc) {
+  case GSK_OK:
+  case GSK_OS400_ASYNCHRONOUS_SOC_INIT:
+    return CURLE_OK;
+  case GSK_KEYRING_OPEN_ERROR:
+  case GSK_OS400_ERROR_NO_ACCESS:
+    return CURLE_SSL_CACERT_BADFILE;
+  case GSK_INSUFFICIENT_STORAGE:
+    return CURLE_OUT_OF_MEMORY;
+  case GSK_ERROR_BAD_V2_CIPHER:
+  case GSK_ERROR_BAD_V3_CIPHER:
+  case GSK_ERROR_NO_CIPHERS:
+    return CURLE_SSL_CIPHER;
+  case GSK_OS400_ERROR_NOT_TRUSTED_ROOT:
+  case GSK_ERROR_CERT_VALIDATION:
+    return CURLE_PEER_FAILED_VERIFICATION;
+  case GSK_OS400_ERROR_TIMED_OUT:
+    return CURLE_OPERATION_TIMEDOUT;
+  case GSK_WOULD_BLOCK:
+    return CURLE_AGAIN;
+  case GSK_OS400_ERROR_NOT_REGISTERED:
+    break;
+  case GSK_ERROR_IO:
+    switch(errno) {
+    case ENOMEM:
+      return CURLE_OUT_OF_MEMORY;
+    default:
+      failf(data, "%s I/O error: %s", procname, strerror(errno));
+      break;
+    }
+    break;
+  default:
+    failf(data, "%s: %s", procname, gsk_strerror(rc));
+    break;
+  }
+  return defcode;
+}
+
+
+static CURLcode set_enum(struct Curl_easy *data, gsk_handle h,
+                GSK_ENUM_ID id, GSK_ENUM_VALUE value, bool unsupported_ok)
+{
+  int rc = gsk_attribute_set_enum(h, id, value);
+
+  switch(rc) {
+  case GSK_OK:
+    return CURLE_OK;
+  case GSK_ERROR_IO:
+    failf(data, "gsk_attribute_set_enum() I/O error: %s", strerror(errno));
+    break;
+  case GSK_ATTRIBUTE_INVALID_ID:
+    if(unsupported_ok)
+      return CURLE_UNSUPPORTED_PROTOCOL;
+  default:
+    failf(data, "gsk_attribute_set_enum(): %s", gsk_strerror(rc));
+    break;
+  }
+  return CURLE_SSL_CONNECT_ERROR;
+}
+
+
+static CURLcode set_buffer(struct Curl_easy *data, gsk_handle h,
+                        GSK_BUF_ID id, const char *buffer, bool unsupported_ok)
+{
+  int rc = gsk_attribute_set_buffer(h, id, buffer, 0);
+
+  switch(rc) {
+  case GSK_OK:
+    return CURLE_OK;
+  case GSK_ERROR_IO:
+    failf(data, "gsk_attribute_set_buffer() I/O error: %s", strerror(errno));
+    break;
+  case GSK_ATTRIBUTE_INVALID_ID:
+    if(unsupported_ok)
+      return CURLE_UNSUPPORTED_PROTOCOL;
+  default:
+    failf(data, "gsk_attribute_set_buffer(): %s", gsk_strerror(rc));
+    break;
+  }
+  return CURLE_SSL_CONNECT_ERROR;
+}
+
+
+static CURLcode set_numeric(struct Curl_easy *data,
+                            gsk_handle h, GSK_NUM_ID id, int value)
+{
+  int rc = gsk_attribute_set_numeric_value(h, id, value);
+
+  switch(rc) {
+  case GSK_OK:
+    return CURLE_OK;
+  case GSK_ERROR_IO:
+    failf(data, "gsk_attribute_set_numeric_value() I/O error: %s",
+          strerror(errno));
+    break;
+  default:
+    failf(data, "gsk_attribute_set_numeric_value(): %s", gsk_strerror(rc));
+    break;
+  }
+  return CURLE_SSL_CONNECT_ERROR;
+}
+
+
+static CURLcode set_callback(struct Curl_easy *data,
+                             gsk_handle h, GSK_CALLBACK_ID id, void *info)
+{
+  int rc = gsk_attribute_set_callback(h, id, info);
+
+  switch(rc) {
+  case GSK_OK:
+    return CURLE_OK;
+  case GSK_ERROR_IO:
+    failf(data, "gsk_attribute_set_callback() I/O error: %s", strerror(errno));
+    break;
+  default:
+    failf(data, "gsk_attribute_set_callback(): %s", gsk_strerror(rc));
+    break;
+  }
+  return CURLE_SSL_CONNECT_ERROR;
+}
+
+
+static CURLcode set_ciphers(struct connectdata *conn,
+                                        gsk_handle h, unsigned int *protoflags)
+{
+  struct Curl_easy *data = conn->data;
+  const char *cipherlist = SSL_CONN_CONFIG(cipher_list);
+  const char *clp;
+  const gskit_cipher *ctp;
+  int i;
+  int l;
+  bool unsupported;
+  CURLcode result;
+  struct {
+    char *buf;
+    char *ptr;
+  } ciphers[CURL_GSKPROTO_LAST];
+
+  /* Compile cipher list into GSKit-compatible cipher lists. */
+
+  if(!cipherlist)
+    return CURLE_OK;
+  while(is_separator(*cipherlist))     /* Skip initial separators. */
+    cipherlist++;
+  if(!*cipherlist)
+    return CURLE_OK;
+
+  /* We allocate GSKit buffers of the same size as the input string: since
+     GSKit tokens are always shorter than their cipher names, allocated buffers
+     will always be large enough to accommodate the result. */
+  l = strlen(cipherlist) + 1;
+  memset((char *) ciphers, 0, sizeof(ciphers));
+  for(i = 0; i < CURL_GSKPROTO_LAST; i++) {
+    ciphers[i].buf = malloc(l);
+    if(!ciphers[i].buf) {
+      while(i--)
+        free(ciphers[i].buf);
+      return CURLE_OUT_OF_MEMORY;
+    }
+    ciphers[i].ptr = ciphers[i].buf;
+    *ciphers[i].ptr = '\0';
+  }
+
+  /* Process each cipher in input string. */
+  unsupported = FALSE;
+  result = CURLE_OK;
+  for(;;) {
+    for(clp = cipherlist; *cipherlist && !is_separator(*cipherlist);)
+      cipherlist++;
+    l = cipherlist - clp;
+    if(!l)
+      break;
+    /* Search the cipher in our table. */
+    for(ctp = ciphertable; ctp->name; ctp++)
+      if(strncasecompare(ctp->name, clp, l) && !ctp->name[l])
+        break;
+    if(!ctp->name) {
+      failf(data, "Unknown cipher %.*s", l, clp);
+      result = CURLE_SSL_CIPHER;
+    }
+    else {
+      unsupported |= !(ctp->versions & (CURL_GSKPROTO_SSLV2_MASK |
+                        CURL_GSKPROTO_SSLV3_MASK | CURL_GSKPROTO_TLSV10_MASK));
+      for(i = 0; i < CURL_GSKPROTO_LAST; i++) {
+        if(ctp->versions & (1 << i)) {
+          strcpy(ciphers[i].ptr, ctp->gsktoken);
+          ciphers[i].ptr += strlen(ctp->gsktoken);
+        }
+      }
+    }
+
+   /* Advance to next cipher name or end of string. */
+    while(is_separator(*cipherlist))
+      cipherlist++;
+  }
+
+  /* Disable protocols with empty cipher lists. */
+  for(i = 0; i < CURL_GSKPROTO_LAST; i++) {
+    if(!(*protoflags & (1 << i)) || !ciphers[i].buf[0]) {
+      *protoflags &= ~(1 << i);
+      ciphers[i].buf[0] = '\0';
+    }
+  }
+
+  /* Try to set-up TLSv1.1 and TLSv2.1 ciphers. */
+  if(*protoflags & CURL_GSKPROTO_TLSV11_MASK) {
+    result = set_buffer(data, h, GSK_TLSV11_CIPHER_SPECS,
+                        ciphers[CURL_GSKPROTO_TLSV11].buf, TRUE);
+    if(result == CURLE_UNSUPPORTED_PROTOCOL) {
+      result = CURLE_OK;
+      if(unsupported) {
+        failf(data, "TLSv1.1-only ciphers are not yet supported");
+        result = CURLE_SSL_CIPHER;
+      }
+    }
+  }
+  if(!result && (*protoflags & CURL_GSKPROTO_TLSV12_MASK)) {
+    result = set_buffer(data, h, GSK_TLSV12_CIPHER_SPECS,
+                        ciphers[CURL_GSKPROTO_TLSV12].buf, TRUE);
+    if(result == CURLE_UNSUPPORTED_PROTOCOL) {
+      result = CURLE_OK;
+      if(unsupported) {
+        failf(data, "TLSv1.2-only ciphers are not yet supported");
+        result = CURLE_SSL_CIPHER;
+      }
+    }
+  }
+
+  /* Try to set-up TLSv1.0 ciphers. If not successful, concatenate them to
+     the SSLv3 ciphers. OS/400 prior to version 7.1 will understand it. */
+  if(!result && (*protoflags & CURL_GSKPROTO_TLSV10_MASK)) {
+    result = set_buffer(data, h, GSK_TLSV10_CIPHER_SPECS,
+                        ciphers[CURL_GSKPROTO_TLSV10].buf, TRUE);
+    if(result == CURLE_UNSUPPORTED_PROTOCOL) {
+      result = CURLE_OK;
+      strcpy(ciphers[CURL_GSKPROTO_SSLV3].ptr,
+             ciphers[CURL_GSKPROTO_TLSV10].ptr);
+    }
+  }
+
+  /* Set-up other ciphers. */
+  if(!result && (*protoflags & CURL_GSKPROTO_SSLV3_MASK))
+    result = set_buffer(data, h, GSK_V3_CIPHER_SPECS,
+                        ciphers[CURL_GSKPROTO_SSLV3].buf, FALSE);
+  if(!result && (*protoflags & CURL_GSKPROTO_SSLV2_MASK))
+    result = set_buffer(data, h, GSK_V2_CIPHER_SPECS,
+                        ciphers[CURL_GSKPROTO_SSLV2].buf, FALSE);
+
+  /* Clean-up. */
+  for(i = 0; i < CURL_GSKPROTO_LAST; i++)
+    free(ciphers[i].buf);
+
+  return result;
+}
+
+
+static int Curl_gskit_init(void)
+{
+  /* No initialisation needed. */
+
+  return 1;
+}
+
+
+static void Curl_gskit_cleanup(void)
+{
+  /* Nothing to do. */
+}
+
+
+static CURLcode init_environment(struct Curl_easy *data,
+                                 gsk_handle *envir, const char *appid,
+                                 const char *file, const char *label,
+                                 const char *password)
+{
+  int rc;
+  CURLcode result;
+  gsk_handle h;
+
+  /* Creates the GSKit environment. */
+
+  rc = gsk_environment_open(&h);
+  switch(rc) {
+  case GSK_OK:
+    break;
+  case GSK_INSUFFICIENT_STORAGE:
+    return CURLE_OUT_OF_MEMORY;
+  default:
+    failf(data, "gsk_environment_open(): %s", gsk_strerror(rc));
+    return CURLE_SSL_CONNECT_ERROR;
+  }
+
+  result = set_enum(data, h, GSK_SESSION_TYPE, GSK_CLIENT_SESSION, FALSE);
+  if(!result && appid)
+    result = set_buffer(data, h, GSK_OS400_APPLICATION_ID, appid, FALSE);
+  if(!result && file)
+    result = set_buffer(data, h, GSK_KEYRING_FILE, file, FALSE);
+  if(!result && label)
+    result = set_buffer(data, h, GSK_KEYRING_LABEL, label, FALSE);
+  if(!result && password)
+    result = set_buffer(data, h, GSK_KEYRING_PW, password, FALSE);
+
+  if(!result) {
+    /* Locate CAs, Client certificate and key according to our settings.
+       Note: this call may be blocking for some tenths of seconds. */
+    result = gskit_status(data, gsk_environment_init(h),
+                          "gsk_environment_init()", CURLE_SSL_CERTPROBLEM);
+    if(!result) {
+      *envir = h;
+      return result;
+    }
+  }
+  /* Error: rollback. */
+  gsk_environment_close(&h);
+  return result;
+}
+
+
+static void cancel_async_handshake(struct connectdata *conn, int sockindex)
+{
+  struct ssl_connect_data *connssl = &conn->ssl[sockindex];
+  Qso_OverlappedIO_t cstat;
+
+  if(QsoCancelOperation(conn->sock[sockindex], 0) > 0)
+    QsoWaitForIOCompletion(BACKEND->iocport, &cstat, (struct timeval *) NULL);
+}
+
+
+static void close_async_handshake(struct ssl_connect_data *connssl)
+{
+  QsoDestroyIOCompletionPort(BACKEND->iocport);
+  BACKEND->iocport = -1;
+}
+
+/* SSL over SSL
+ * Problems:
+ * 1) GSKit can only perform SSL on an AF_INET or AF_INET6 stream socket. To
+ *    pipe an SSL stream into another, it is therefore needed to have a pair
+ *    of such communicating sockets and handle the pipelining explicitly.
+ * 2) OS/400 socketpair() is only implemented for domain AF_UNIX, thus cannot
+ *    be used to produce the pipeline.
+ * The solution is to simulate socketpair() for AF_INET with low-level API
+ *    listen(), bind() and connect().
+ */
+
+static int
+inetsocketpair(int sv[2])
+{
+  int lfd;      /* Listening socket. */
+  int sfd;      /* Server socket. */
+  int cfd;      /* Client socket. */
+  int len;
+  struct sockaddr_in addr1;
+  struct sockaddr_in addr2;
+
+  /* Create listening socket on a local dynamic port. */
+  lfd = socket(AF_INET, SOCK_STREAM, 0);
+  if(lfd < 0)
+    return -1;
+  memset((char *) &addr1, 0, sizeof(addr1));
+  addr1.sin_family = AF_INET;
+  addr1.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
+  addr1.sin_port = 0;
+  if(bind(lfd, (struct sockaddr *) &addr1, sizeof(addr1)) ||
+     listen(lfd, 2) < 0) {
+    close(lfd);
+    return -1;
+  }
+
+  /* Get the allocated port. */
+  len = sizeof(addr1);
+  if(getsockname(lfd, (struct sockaddr *) &addr1, &len) < 0) {
+    close(lfd);
+    return -1;
+  }
+
+  /* Create the client socket. */
+  cfd = socket(AF_INET, SOCK_STREAM, 0);
+  if(cfd < 0) {
+    close(lfd);
+    return -1;
+  }
+
+  /* Request unblocking connection to the listening socket. */
+  curlx_nonblock(cfd, TRUE);
+  if(connect(cfd, (struct sockaddr *) &addr1, sizeof(addr1)) < 0 &&
+     errno != EINPROGRESS) {
+    close(lfd);
+    close(cfd);
+    return -1;
+  }
+
+  /* Get the client dynamic port for intrusion check below. */
+  len = sizeof(addr2);
+  if(getsockname(cfd, (struct sockaddr *) &addr2, &len) < 0) {
+    close(lfd);
+    close(cfd);
+    return -1;
+  }
+
+  /* Accept the incoming connection and get the server socket. */
+  curlx_nonblock(lfd, TRUE);
+  for(;;) {
+    len = sizeof(addr1);
+    sfd = accept(lfd, (struct sockaddr *) &addr1, &len);
+    if(sfd < 0) {
+      close(lfd);
+      close(cfd);
+      return -1;
+    }
+
+    /* Check for possible intrusion from an external process. */
+    if(addr1.sin_addr.s_addr == addr2.sin_addr.s_addr &&
+       addr1.sin_port == addr2.sin_port)
+      break;
+
+    /* Intrusion: reject incoming connection. */
+    close(sfd);
+  }
+
+  /* Done, return sockets and succeed. */
+  close(lfd);
+  curlx_nonblock(cfd, FALSE);
+  sv[0] = cfd;
+  sv[1] = sfd;
+  return 0;
+}
+
+static int pipe_ssloverssl(struct connectdata *conn, int sockindex,
+                           int directions)
+{
+  struct ssl_connect_data *connssl = &conn->ssl[sockindex];
+  struct ssl_connect_data *connproxyssl = &conn->proxy_ssl[sockindex];
+  fd_set fds_read;
+  fd_set fds_write;
+  int n;
+  int m;
+  int i;
+  int ret = 0;
+  struct timeval tv = {0, 0};
+  char buf[CURL_MAX_WRITE_SIZE];
+
+  if(!connssl->use || !connproxyssl->use)
+    return 0;   /* No SSL over SSL: OK. */
+
+  FD_ZERO(&fds_read);
+  FD_ZERO(&fds_write);
+  n = -1;
+  if(directions & SOS_READ) {
+    FD_SET(BACKEND->remotefd, &fds_write);
+    n = BACKEND->remotefd;
+  }
+  if(directions & SOS_WRITE) {
+    FD_SET(BACKEND->remotefd, &fds_read);
+    n = BACKEND->remotefd;
+    FD_SET(conn->sock[sockindex], &fds_write);
+    if(n < conn->sock[sockindex])
+      n = conn->sock[sockindex];
+  }
+  i = select(n + 1, &fds_read, &fds_write, NULL, &tv);
+  if(i < 0)
+    return -1;  /* Select error. */
+
+  if(FD_ISSET(BACKEND->remotefd, &fds_write)) {
+    /* Try getting data from HTTPS proxy and pipe it upstream. */
+    n = 0;
+    i = gsk_secure_soc_read(connproxyssl->backend->handle,
+                            buf, sizeof(buf), &n);
+    switch(i) {
+    case GSK_OK:
+      if(n) {
+        i = write(BACKEND->remotefd, buf, n);
+        if(i < 0)
+          return -1;
+        ret = 1;
+      }
+      break;
+    case GSK_OS400_ERROR_TIMED_OUT:
+    case GSK_WOULD_BLOCK:
+      break;
+    default:
+      return -1;
+    }
+  }
+
+  if(FD_ISSET(BACKEND->remotefd, &fds_read) &&
+     FD_ISSET(conn->sock[sockindex], &fds_write)) {
+    /* Pipe data to HTTPS proxy. */
+    n = read(BACKEND->remotefd, buf, sizeof(buf));
+    if(n < 0)
+      return -1;
+    if(n) {
+      i = gsk_secure_soc_write(connproxyssl->backend->handle, buf, n, &m);
+      if(i != GSK_OK || n != m)
+        return -1;
+      ret = 1;
+    }
+  }
+
+  return ret;  /* OK */
+}
+
+
+static void close_one(struct ssl_connect_data *connssl,
+                      struct connectdata *conn, int sockindex)
+{
+  if(BACKEND->handle) {
+    gskit_status(conn->data, gsk_secure_soc_close(&BACKEND->handle),
+              "gsk_secure_soc_close()", 0);
+    /* Last chance to drain output. */
+    while(pipe_ssloverssl(conn, sockindex, SOS_WRITE) > 0)
+      ;
+    BACKEND->handle = (gsk_handle) NULL;
+    if(BACKEND->localfd >= 0) {
+      close(BACKEND->localfd);
+      BACKEND->localfd = -1;
+    }
+    if(BACKEND->remotefd >= 0) {
+      close(BACKEND->remotefd);
+      BACKEND->remotefd = -1;
+    }
+  }
+  if(BACKEND->iocport >= 0)
+    close_async_handshake(connssl);
+}
+
+
+static ssize_t gskit_send(struct connectdata *conn, int sockindex,
+                           const void *mem, size_t len, CURLcode *curlcode)
+{
+  struct ssl_connect_data *connssl = &conn->ssl[sockindex];
+  struct Curl_easy *data = conn->data;
+  CURLcode cc = CURLE_SEND_ERROR;
+  int written;
+
+  if(pipe_ssloverssl(conn, sockindex, SOS_WRITE) >= 0) {
+    cc = gskit_status(data,
+                      gsk_secure_soc_write(BACKEND->handle,
+                                           (char *) mem, (int) len, &written),
+                      "gsk_secure_soc_write()", CURLE_SEND_ERROR);
+    if(cc == CURLE_OK)
+      if(pipe_ssloverssl(conn, sockindex, SOS_WRITE) < 0)
+        cc = CURLE_SEND_ERROR;
+  }
+  if(cc != CURLE_OK) {
+    *curlcode = cc;
+    written = -1;
+  }
+  return (ssize_t) written; /* number of bytes */
+}
+
+
+static ssize_t gskit_recv(struct connectdata *conn, int num, char *buf,
+                           size_t buffersize, CURLcode *curlcode)
+{
+  struct ssl_connect_data *connssl = &conn->ssl[num];
+  struct Curl_easy *data = conn->data;
+  int nread;
+  CURLcode cc = CURLE_RECV_ERROR;
+
+  if(pipe_ssloverssl(conn, num, SOS_READ) >= 0) {
+    int buffsize = buffersize > (size_t) INT_MAX? INT_MAX: (int) buffersize;
+    cc = gskit_status(data, gsk_secure_soc_read(BACKEND->handle,
+                                                buf, buffsize, &nread),
+                      "gsk_secure_soc_read()", CURLE_RECV_ERROR);
+  }
+  switch(cc) {
+  case CURLE_OK:
+    break;
+  case CURLE_OPERATION_TIMEDOUT:
+    cc = CURLE_AGAIN;
+  default:
+    *curlcode = cc;
+    nread = -1;
+    break;
+  }
+  return (ssize_t) nread;
+}
+
+static CURLcode
+set_ssl_version_min_max(unsigned int *protoflags, 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;
+  switch(ssl_version_max) {
+    case CURL_SSLVERSION_MAX_NONE:
+    case CURL_SSLVERSION_MAX_DEFAULT:
+      ssl_version_max = CURL_SSLVERSION_TLSv1_2;
+      break;
+  }
+  for(; i <= (ssl_version_max >> 16); ++i) {
+    switch(i) {
+      case CURL_SSLVERSION_TLSv1_0:
+        *protoflags |= CURL_GSKPROTO_TLSV10_MASK;
+        break;
+      case CURL_SSLVERSION_TLSv1_1:
+        *protoflags |= CURL_GSKPROTO_TLSV11_MASK;
+        break;
+      case CURL_SSLVERSION_TLSv1_2:
+        *protoflags |= CURL_GSKPROTO_TLSV11_MASK;
+        break;
+      case CURL_SSLVERSION_TLSv1_3:
+        failf(data, "GSKit: TLS 1.3 is not yet supported");
+        return CURLE_SSL_CONNECT_ERROR;
+    }
+  }
+
+  return CURLE_OK;
+}
+
+static CURLcode gskit_connect_step1(struct connectdata *conn, int sockindex)
+{
+  struct Curl_easy *data = conn->data;
+  struct ssl_connect_data *connssl = &conn->ssl[sockindex];
+  gsk_handle envir;
+  CURLcode result;
+  int rc;
+  const char * const keyringfile = SSL_CONN_CONFIG(CAfile);
+  const char * const keyringpwd = SSL_SET_OPTION(key_passwd);
+  const char * const keyringlabel = SSL_SET_OPTION(cert);
+  const long int ssl_version = SSL_CONN_CONFIG(version);
+  const bool verifypeer = SSL_CONN_CONFIG(verifypeer);
+  const char * const hostname = SSL_IS_PROXY()? conn->http_proxy.host.name:
+    conn->host.name;
+  const char *sni;
+  unsigned int protoflags = 0;
+  Qso_OverlappedIO_t commarea;
+  int sockpair[2];
+  static const int sobufsize = CURL_MAX_WRITE_SIZE;
+
+  /* Create SSL environment, start (preferably asynchronous) handshake. */
+
+  BACKEND->handle = (gsk_handle) NULL;
+  BACKEND->iocport = -1;
+  BACKEND->localfd = -1;
+  BACKEND->remotefd = -1;
+
+  /* GSKit supports two ways of specifying an SSL context: either by
+   *  application identifier (that should have been defined at the system
+   *  level) or by keyring file, password and certificate label.
+   * Local certificate name (CURLOPT_SSLCERT) is used to hold either the
+   *  application identifier of the certificate label.
+   * Key password (CURLOPT_KEYPASSWD) holds the keyring password.
+   * It is not possible to have different keyrings for the CAs and the
+   *  local certificate. We thus use the CA file (CURLOPT_CAINFO) to identify
+   *  the keyring file.
+   * If no key password is given and the keyring is the system keyring,
+   *  application identifier mode is tried first, as recommended in IBM doc.
+   */
+
+  envir = (gsk_handle) NULL;
+
+  if(keyringlabel && *keyringlabel && !keyringpwd &&
+      !strcmp(keyringfile, CURL_CA_BUNDLE)) {
+    /* Try application identifier mode. */
+    init_environment(data, &envir, keyringlabel, (const char *) NULL,
+                     (const char *) NULL, (const char *) NULL);
+  }
+
+  if(!envir) {
+    /* Use keyring mode. */
+    result = init_environment(data, &envir, (const char *) NULL,
+                              keyringfile, keyringlabel, keyringpwd);
+    if(result)
+      return result;
+  }
+
+  /* Create secure session. */
+  result = gskit_status(data, gsk_secure_soc_open(envir, &BACKEND->handle),
+                        "gsk_secure_soc_open()", CURLE_SSL_CONNECT_ERROR);
+  gsk_environment_close(&envir);
+  if(result)
+    return result;
+
+  /* Establish a pipelining socket pair for SSL over SSL. */
+  if(conn->proxy_ssl[sockindex].use) {
+    if(inetsocketpair(sockpair))
+      return CURLE_SSL_CONNECT_ERROR;
+    BACKEND->localfd = sockpair[0];
+    BACKEND->remotefd = sockpair[1];
+    setsockopt(BACKEND->localfd, SOL_SOCKET, SO_RCVBUF,
+               (void *) sobufsize, sizeof(sobufsize));
+    setsockopt(BACKEND->remotefd, SOL_SOCKET, SO_RCVBUF,
+               (void *) sobufsize, sizeof(sobufsize));
+    setsockopt(BACKEND->localfd, SOL_SOCKET, SO_SNDBUF,
+               (void *) sobufsize, sizeof(sobufsize));
+    setsockopt(BACKEND->remotefd, SOL_SOCKET, SO_SNDBUF,
+               (void *) sobufsize, sizeof(sobufsize));
+    curlx_nonblock(BACKEND->localfd, TRUE);
+    curlx_nonblock(BACKEND->remotefd, TRUE);
+  }
+
+  /* Determine which SSL/TLS version should be enabled. */
+  sni = hostname;
+  switch(ssl_version) {
+  case CURL_SSLVERSION_SSLv2:
+    protoflags = CURL_GSKPROTO_SSLV2_MASK;
+    sni = NULL;
+    break;
+  case CURL_SSLVERSION_SSLv3:
+    protoflags = CURL_GSKPROTO_SSLV3_MASK;
+    sni = NULL;
+    break;
+  case CURL_SSLVERSION_DEFAULT:
+  case CURL_SSLVERSION_TLSv1:
+    protoflags = CURL_GSKPROTO_TLSV10_MASK |
+                 CURL_GSKPROTO_TLSV11_MASK | CURL_GSKPROTO_TLSV12_MASK;
+    break;
+  case CURL_SSLVERSION_TLSv1_0:
+  case CURL_SSLVERSION_TLSv1_1:
+  case CURL_SSLVERSION_TLSv1_2:
+  case CURL_SSLVERSION_TLSv1_3:
+    result = set_ssl_version_min_max(&protoflags, conn);
+    if(result != CURLE_OK)
+      return result;
+    break;
+  default:
+    failf(data, "Unrecognized parameter passed via CURLOPT_SSLVERSION");
+    return CURLE_SSL_CONNECT_ERROR;
+  }
+
+  /* Process SNI. Ignore if not supported (on OS400 < V7R1). */
+  if(sni) {
+    result = set_buffer(data, BACKEND->handle,
+                        GSK_SSL_EXTN_SERVERNAME_REQUEST, sni, TRUE);
+    if(result == CURLE_UNSUPPORTED_PROTOCOL)
+      result = CURLE_OK;
+  }
+
+  /* Set session parameters. */
+  if(!result) {
+    /* Compute the handshake timeout. Since GSKit granularity is 1 second,
+       we round up the required value. */
+    long timeout = Curl_timeleft(data, NULL, TRUE);
+    if(timeout < 0)
+      result = CURLE_OPERATION_TIMEDOUT;
+    else
+      result = set_numeric(data, BACKEND->handle, GSK_HANDSHAKE_TIMEOUT,
+                           (timeout + 999) / 1000);
+  }
+  if(!result)
+    result = set_numeric(data, BACKEND->handle, GSK_OS400_READ_TIMEOUT, 1);
+  if(!result)
+    result = set_numeric(data, BACKEND->handle, GSK_FD, BACKEND->localfd >= 0?
+                         BACKEND->localfd: conn->sock[sockindex]);
+  if(!result)
+    result = set_ciphers(conn, BACKEND->handle, &protoflags);
+  if(!protoflags) {
+    failf(data, "No SSL protocol/cipher combination enabled");
+    result = CURLE_SSL_CIPHER;
+  }
+  if(!result)
+    result = set_enum(data, BACKEND->handle, GSK_PROTOCOL_SSLV2,
+                      (protoflags & CURL_GSKPROTO_SSLV2_MASK)?
+                      GSK_PROTOCOL_SSLV2_ON: GSK_PROTOCOL_SSLV2_OFF, FALSE);
+  if(!result)
+    result = set_enum(data, BACKEND->handle, GSK_PROTOCOL_SSLV3,
+                      (protoflags & CURL_GSKPROTO_SSLV3_MASK)?
+                      GSK_PROTOCOL_SSLV3_ON: GSK_PROTOCOL_SSLV3_OFF, FALSE);
+  if(!result)
+    result = set_enum(data, BACKEND->handle, GSK_PROTOCOL_TLSV1,
+                      (protoflags & CURL_GSKPROTO_TLSV10_MASK)?
+                      GSK_PROTOCOL_TLSV1_ON: GSK_PROTOCOL_TLSV1_OFF, FALSE);
+  if(!result) {
+    result = set_enum(data, BACKEND->handle, GSK_PROTOCOL_TLSV11,
+                      (protoflags & CURL_GSKPROTO_TLSV11_MASK)?
+                      GSK_TRUE: GSK_FALSE, TRUE);
+    if(result == CURLE_UNSUPPORTED_PROTOCOL) {
+      result = CURLE_OK;
+      if(protoflags == CURL_GSKPROTO_TLSV11_MASK) {
+        failf(data, "TLS 1.1 not yet supported");
+        result = CURLE_SSL_CIPHER;
+      }
+    }
+  }
+  if(!result) {
+    result = set_enum(data, BACKEND->handle, GSK_PROTOCOL_TLSV12,
+                      (protoflags & CURL_GSKPROTO_TLSV12_MASK)?
+                      GSK_TRUE: GSK_FALSE, TRUE);
+    if(result == CURLE_UNSUPPORTED_PROTOCOL) {
+      result = CURLE_OK;
+      if(protoflags == CURL_GSKPROTO_TLSV12_MASK) {
+        failf(data, "TLS 1.2 not yet supported");
+        result = CURLE_SSL_CIPHER;
+      }
+    }
+  }
+  if(!result)
+    result = set_enum(data, BACKEND->handle, GSK_SERVER_AUTH_TYPE,
+                      verifypeer? GSK_SERVER_AUTH_FULL:
+                      GSK_SERVER_AUTH_PASSTHRU, FALSE);
+
+  if(!result) {
+    /* Start handshake. Try asynchronous first. */
+    memset(&commarea, 0, sizeof(commarea));
+    BACKEND->iocport = QsoCreateIOCompletionPort();
+    if(BACKEND->iocport != -1) {
+      result = gskit_status(data,
+                            gsk_secure_soc_startInit(BACKEND->handle,
+                                                     BACKEND->iocport,
+                                                     &commarea),
+                            "gsk_secure_soc_startInit()",
+                            CURLE_SSL_CONNECT_ERROR);
+      if(!result) {
+        connssl->connecting_state = ssl_connect_2;
+        return CURLE_OK;
+      }
+      else
+        close_async_handshake(connssl);
+    }
+    else if(errno != ENOBUFS)
+      result = gskit_status(data, GSK_ERROR_IO,
+                            "QsoCreateIOCompletionPort()", 0);
+    else if(conn->proxy_ssl[sockindex].use) {
+      /* Cannot pipeline while handshaking synchronously. */
+      result = CURLE_SSL_CONNECT_ERROR;
+    }
+    else {
+      /* No more completion port available. Use synchronous IO. */
+      result = gskit_status(data, gsk_secure_soc_init(BACKEND->handle),
+                            "gsk_secure_soc_init()", CURLE_SSL_CONNECT_ERROR);
+      if(!result) {
+        connssl->connecting_state = ssl_connect_3;
+        return CURLE_OK;
+      }
+    }
+  }
+
+  /* Error: rollback. */
+  close_one(connssl, conn, sockindex);
+  return result;
+}
+
+
+static CURLcode gskit_connect_step2(struct connectdata *conn, int sockindex,
+                                    bool nonblocking)
+{
+  struct Curl_easy *data = conn->data;
+  struct ssl_connect_data *connssl = &conn->ssl[sockindex];
+  Qso_OverlappedIO_t cstat;
+  struct timeval stmv;
+  CURLcode result;
+
+  /* Poll or wait for end of SSL asynchronous handshake. */
+
+  for(;;) {
+    long timeout_ms = nonblocking? 0: Curl_timeleft(data, NULL, TRUE);
+    if(timeout_ms < 0)
+      timeout_ms = 0;
+    stmv.tv_sec = timeout_ms / 1000;
+    stmv.tv_usec = (timeout_ms - stmv.tv_sec * 1000) * 1000;
+    switch(QsoWaitForIOCompletion(BACKEND->iocport, &cstat, &stmv)) {
+    case 1:             /* Operation complete. */
+      break;
+    case -1:            /* An error occurred: handshake still in progress. */
+      if(errno == EINTR) {
+        if(nonblocking)
+          return CURLE_OK;
+        continue;       /* Retry. */
+      }
+      if(errno != ETIME) {
+        failf(data, "QsoWaitForIOCompletion() I/O error: %s", strerror(errno));
+        cancel_async_handshake(conn, sockindex);
+        close_async_handshake(connssl);
+        return CURLE_SSL_CONNECT_ERROR;
+      }
+      /* FALL INTO... */
+    case 0:             /* Handshake in progress, timeout occurred. */
+      if(nonblocking)
+        return CURLE_OK;
+      cancel_async_handshake(conn, sockindex);
+      close_async_handshake(connssl);
+      return CURLE_OPERATION_TIMEDOUT;
+    }
+    break;
+  }
+  result = gskit_status(data, cstat.returnValue, "SSL handshake",
+                        CURLE_SSL_CONNECT_ERROR);
+  if(!result)
+    connssl->connecting_state = ssl_connect_3;
+  close_async_handshake(connssl);
+  return result;
+}
+
+
+static CURLcode gskit_connect_step3(struct connectdata *conn, int sockindex)
+{
+  struct Curl_easy *data = conn->data;
+  struct ssl_connect_data *connssl = &conn->ssl[sockindex];
+  const gsk_cert_data_elem *cdev;
+  int cdec;
+  const gsk_cert_data_elem *p;
+  const char *cert = (const char *) NULL;
+  const char *certend;
+  const char *ptr;
+  CURLcode result;
+
+  /* SSL handshake done: gather certificate info and verify host. */
+
+  if(gskit_status(data, gsk_attribute_get_cert_info(BACKEND->handle,
+                                                    GSK_PARTNER_CERT_INFO,
+                                                    &cdev, &cdec),
+                  "gsk_attribute_get_cert_info()", CURLE_SSL_CONNECT_ERROR) ==
+     CURLE_OK) {
+    int i;
+
+    infof(data, "Server certificate:\n");
+    p = cdev;
+    for(i = 0; i++ < cdec; p++)
+      switch(p->cert_data_id) {
+      case CERT_BODY_DER:
+        cert = p->cert_data_p;
+        certend = cert + cdev->cert_data_l;
+        break;
+      case CERT_DN_PRINTABLE:
+        infof(data, "\t subject: %.*s\n", p->cert_data_l, p->cert_data_p);
+        break;
+      case CERT_ISSUER_DN_PRINTABLE:
+        infof(data, "\t issuer: %.*s\n", p->cert_data_l, p->cert_data_p);
+        break;
+      case CERT_VALID_FROM:
+        infof(data, "\t start date: %.*s\n", p->cert_data_l, p->cert_data_p);
+        break;
+      case CERT_VALID_TO:
+        infof(data, "\t expire date: %.*s\n", p->cert_data_l, p->cert_data_p);
+        break;
+    }
+  }
+
+  /* Verify host. */
+  result = Curl_verifyhost(conn, cert, certend);
+  if(result)
+    return result;
+
+  /* The only place GSKit can get the whole CA chain is a validation
+     callback where no user data pointer is available. Therefore it's not
+     possible to copy this chain into our structures for CAINFO.
+     However the server certificate may be available, thus we can return
+     info about it. */
+  if(data->set.ssl.certinfo) {
+    result = Curl_ssl_init_certinfo(data, 1);
+    if(result)
+      return result;
+
+    if(cert) {
+      result = Curl_extract_certinfo(conn, 0, cert, certend);
+      if(result)
+        return result;
+    }
+  }
+
+  /* Check pinned public key. */
+  ptr = SSL_IS_PROXY() ? data->set.str[STRING_SSL_PINNEDPUBLICKEY_PROXY] :
+                         data->set.str[STRING_SSL_PINNEDPUBLICKEY_ORIG];
+  if(!result && ptr) {
+    curl_X509certificate x509;
+    curl_asn1Element *p;
+
+    if(Curl_parseX509(&x509, cert, certend))
+      return CURLE_SSL_PINNEDPUBKEYNOTMATCH;
+    p = &x509.subjectPublicKeyInfo;
+    result = Curl_pin_peer_pubkey(data, ptr, p->header, p->end - p->header);
+    if(result) {
+      failf(data, "SSL: public key does not match pinned public key!");
+      return result;
+    }
+  }
+
+  connssl->connecting_state = ssl_connect_done;
+  return CURLE_OK;
+}
+
+
+static CURLcode gskit_connect_common(struct connectdata *conn, int sockindex,
+                                     bool nonblocking, bool *done)
+{
+  struct Curl_easy *data = conn->data;
+  struct ssl_connect_data *connssl = &conn->ssl[sockindex];
+  long timeout_ms;
+  CURLcode result = CURLE_OK;
+
+  *done = connssl->state == ssl_connection_complete;
+  if(*done)
+    return CURLE_OK;
+
+  /* Step 1: create session, start handshake. */
+  if(connssl->connecting_state == ssl_connect_1) {
+    /* check allowed time left */
+    timeout_ms = Curl_timeleft(data, NULL, TRUE);
+
+    if(timeout_ms < 0) {
+      /* no need to continue if time already is up */
+      failf(data, "SSL connection timeout");
+      result = CURLE_OPERATION_TIMEDOUT;
+    }
+    else
+      result = gskit_connect_step1(conn, sockindex);
+  }
+
+  /* Handle handshake pipelining. */
+  if(!result)
+    if(pipe_ssloverssl(conn, sockindex, SOS_READ | SOS_WRITE) < 0)
+      result = CURLE_SSL_CONNECT_ERROR;
+
+  /* Step 2: check if handshake is over. */
+  if(!result && connssl->connecting_state == ssl_connect_2) {
+    /* check allowed time left */
+    timeout_ms = Curl_timeleft(data, NULL, TRUE);
+
+    if(timeout_ms < 0) {
+      /* no need to continue if time already is up */
+      failf(data, "SSL connection timeout");
+      result = CURLE_OPERATION_TIMEDOUT;
+    }
+    else
+      result = gskit_connect_step2(conn, sockindex, nonblocking);
+  }
+
+  /* Handle handshake pipelining. */
+  if(!result)
+    if(pipe_ssloverssl(conn, sockindex, SOS_READ | SOS_WRITE) < 0)
+      result = CURLE_SSL_CONNECT_ERROR;
+
+  /* Step 3: gather certificate info, verify host. */
+  if(!result && connssl->connecting_state == ssl_connect_3)
+    result = gskit_connect_step3(conn, sockindex);
+
+  if(result)
+    close_one(connssl, conn, sockindex);
+  else if(connssl->connecting_state == ssl_connect_done) {
+    connssl->state = ssl_connection_complete;
+    connssl->connecting_state = ssl_connect_1;
+    conn->recv[sockindex] = gskit_recv;
+    conn->send[sockindex] = gskit_send;
+    *done = TRUE;
+  }
+
+  return result;
+}
+
+
+static CURLcode Curl_gskit_connect_nonblocking(struct connectdata *conn,
+                                               int sockindex, bool *done)
+{
+  CURLcode result;
+
+  result = gskit_connect_common(conn, sockindex, TRUE, done);
+  if(*done || result)
+    conn->ssl[sockindex].connecting_state = ssl_connect_1;
+  return result;
+}
+
+
+static CURLcode Curl_gskit_connect(struct connectdata *conn, int sockindex)
+{
+  CURLcode result;
+  bool done;
+
+  conn->ssl[sockindex].connecting_state = ssl_connect_1;
+  result = gskit_connect_common(conn, sockindex, FALSE, &done);
+  if(result)
+    return result;
+
+  DEBUGASSERT(done);
+
+  return CURLE_OK;
+}
+
+
+static void Curl_gskit_close(struct connectdata *conn, int sockindex)
+{
+  close_one(&conn->ssl[sockindex], conn, sockindex);
+  close_one(&conn->proxy_ssl[sockindex], conn, sockindex);
+}
+
+
+static int Curl_gskit_shutdown(struct connectdata *conn, int sockindex)
+{
+  struct ssl_connect_data *connssl = &conn->ssl[sockindex];
+  struct Curl_easy *data = conn->data;
+  int what;
+  int rc;
+  char buf[120];
+
+  if(!BACKEND->handle)
+    return 0;
+
+#ifndef CURL_DISABLE_FTP
+  if(data->set.ftp_ccc != CURLFTPSSL_CCC_ACTIVE)
+    return 0;
+#endif
+
+  close_one(connssl, conn, sockindex);
+  rc = 0;
+  what = SOCKET_READABLE(conn->sock[sockindex],
+                         SSL_SHUTDOWN_TIMEOUT);
+
+  for(;;) {
+    ssize_t nread;
+
+    if(what < 0) {
+      /* anything that gets here is fatally bad */
+      failf(data, "select/poll on SSL socket, errno: %d", SOCKERRNO);
+      rc = -1;
+      break;
+    }
+
+    if(!what) {                                /* timeout */
+      failf(data, "SSL shutdown timeout");
+      break;
+    }
+
+    /* Something to read, let's do it and hope that it is the close
+       notify alert from the server. No way to gsk_secure_soc_read() now, so
+       use read(). */
+
+    nread = read(conn->sock[sockindex], buf, sizeof(buf));
+
+    if(nread < 0) {
+      failf(data, "read: %s", strerror(errno));
+      rc = -1;
+    }
+
+    if(nread <= 0)
+      break;
+
+    what = SOCKET_READABLE(conn->sock[sockindex], 0);
+  }
+
+  return rc;
+}
+
+
+static size_t Curl_gskit_version(char *buffer, size_t size)
+{
+  return msnprintf(buffer, size, "GSKit");
+}
+
+
+static int Curl_gskit_check_cxn(struct connectdata *cxn)
+{
+  struct ssl_connect_data *connssl = &cxn->ssl[FIRSTSOCKET];
+  int err;
+  int errlen;
+
+  /* The only thing that can be tested here is at the socket level. */
+
+  if(!BACKEND->handle)
+    return 0; /* connection has been closed */
+
+  err = 0;
+  errlen = sizeof(err);
+
+  if(getsockopt(cxn->sock[FIRSTSOCKET], SOL_SOCKET, SO_ERROR,
+                 (unsigned char *) &err, &errlen) ||
+     errlen != sizeof(err) || err)
+    return 0; /* connection has been closed */
+
+  return -1;  /* connection status unknown */
+}
+
+static void *Curl_gskit_get_internals(struct ssl_connect_data *connssl,
+                                      CURLINFO info UNUSED_PARAM)
+{
+  (void)info;
+  return BACKEND->handle;
+}
+
+const struct Curl_ssl Curl_ssl_gskit = {
+  { CURLSSLBACKEND_GSKIT, "gskit" }, /* info */
+
+  SSLSUPP_CERTINFO |
+  SSLSUPP_PINNEDPUBKEY,
+
+  sizeof(struct ssl_backend_data),
+
+  Curl_gskit_init,                /* init */
+  Curl_gskit_cleanup,             /* cleanup */
+  Curl_gskit_version,             /* version */
+  Curl_gskit_check_cxn,           /* check_cxn */
+  Curl_gskit_shutdown,            /* shutdown */
+  Curl_none_data_pending,         /* data_pending */
+  Curl_none_random,               /* random */
+  Curl_none_cert_status_request,  /* cert_status_request */
+  Curl_gskit_connect,             /* connect */
+  Curl_gskit_connect_nonblocking, /* connect_nonblocking */
+  Curl_gskit_get_internals,       /* get_internals */
+  Curl_gskit_close,               /* close_one */
+  Curl_none_close_all,            /* close_all */
+  /* No session handling for GSKit */
+  Curl_none_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_none_md5sum,               /* md5sum */
+  NULL                            /* sha256sum */
+};
+
+#endif /* USE_GSKIT */