proxy.c

 
#include <ctype.h>
#include <errno.h>
#include <limits.h>
 
#include <openssl/err.h>
 
#include "settings.h"
#include "proxy.h"
#include <freerdp/settings.h>
#include <freerdp/utils/proxy_utils.h>
#include <freerdp/crypto/crypto.h>
#include "tcp.h"
 
#include <winpr/assert.h>
#include <winpr/sysinfo.h>
#include <winpr/environment.h> /* For GetEnvironmentVariableA */
 
#define CRLF "\r\n"
 
#include <freerdp/log.h>
#define TAG FREERDP_TAG("core.proxy")
 
/* SOCKS Proxy auth methods by rfc1928 */
enum
{
  AUTH_M_NO_AUTH = 0,
  AUTH_M_GSSAPI = 1,
  AUTH_M_USR_PASS = 2
};
 
enum
{
  SOCKS_CMD_CONNECT = 1,
  SOCKS_CMD_BIND = 2,
  SOCKS_CMD_UDP_ASSOCIATE = 3
};
 
enum
{
  SOCKS_ADDR_IPV4 = 1,
  SOCKS_ADDR_FQDN = 3,
  SOCKS_ADDR_IPV6 = 4,
};
 
static const char logprefix[] = "SOCKS Proxy:";
 
/* CONN REQ replies in enum. order */
static const char* rplstat[] = { "succeeded",
                               "general SOCKS server failure",
                               "connection not allowed by ruleset",
                               "Network unreachable",
                               "Host unreachable",
                               "Connection refused",
                               "TTL expired",
                               "Command not supported",
                               "Address type not supported" };
 
static BOOL http_proxy_connect(rdpContext* context, BIO* bufferedBio, const char* proxyUsername,
                               const char* proxyPassword, const char* hostname, UINT16 port);
static BOOL socks_proxy_connect(rdpContext* context, BIO* bufferedBio, const char* proxyUsername,
                                const char* proxyPassword, const char* hostname, UINT16 port);
static void proxy_read_environment(rdpSettings* settings, char* envname);
 
BOOL proxy_prepare(rdpSettings* settings, const char** lpPeerHostname, UINT16* lpPeerPort,
                   const char** lpProxyUsername, const char** lpProxyPassword)
{
  if (freerdp_settings_get_uint32(settings, FreeRDP_ProxyType) == PROXY_TYPE_IGNORE)
    return FALSE;
 
  /* For TSGateway, find the system HTTPS proxy automatically */
  if (freerdp_settings_get_uint32(settings, FreeRDP_ProxyType) == PROXY_TYPE_NONE)
    proxy_read_environment(settings, "https_proxy");
 
  if (freerdp_settings_get_uint32(settings, FreeRDP_ProxyType) == PROXY_TYPE_NONE)
    proxy_read_environment(settings, "HTTPS_PROXY");
 
  if (freerdp_settings_get_uint32(settings, FreeRDP_ProxyType) != PROXY_TYPE_NONE)
    proxy_read_environment(settings, "no_proxy");
 
  if (freerdp_settings_get_uint32(settings, FreeRDP_ProxyType) != PROXY_TYPE_NONE)
    proxy_read_environment(settings, "NO_PROXY");
 
  if (freerdp_settings_get_uint32(settings, FreeRDP_ProxyType) != PROXY_TYPE_NONE)
  {
    *lpPeerHostname = freerdp_settings_get_string(settings, FreeRDP_ProxyHostname);
    *lpPeerPort = freerdp_settings_get_uint16(settings, FreeRDP_ProxyPort);
    *lpProxyUsername = freerdp_settings_get_string(settings, FreeRDP_ProxyUsername);
    *lpProxyPassword = freerdp_settings_get_string(settings, FreeRDP_ProxyPassword);
    return TRUE;
  }
 
  return FALSE;
}
 
static BOOL value_to_int(const char* value, LONGLONG* result, LONGLONG min, LONGLONG max)
{
  long long rc = 0;
 
  if (!value || !result)
    return FALSE;
 
  errno = 0;
  rc = _strtoi64(value, NULL, 0);
 
  if (errno != 0)
    return FALSE;
 
  if ((rc < min) || (rc > max))
    return FALSE;
 
  *result = rc;
  return TRUE;
}
 
static BOOL cidr4_match(const struct in_addr* addr, const struct in_addr* net, BYTE bits)
{
  if (bits == 0)
    return TRUE;
 
  const uint32_t mask = htonl(0xFFFFFFFFu << (32 - bits));
  const uint32_t amask = addr->s_addr & mask;
  const uint32_t nmask = net->s_addr & mask;
  return amask == nmask;
}
 
static BOOL cidr6_match(const struct in6_addr* address, const struct in6_addr* network,
                        uint8_t bits)
{
  const uint32_t* a = (const uint32_t*)address;
  const uint32_t* n = (const uint32_t*)network;
  const size_t bits_whole = bits >> 5;
  const size_t bits_incomplete = bits & 0x1F;
 
  if (bits_whole)
  {
    if (memcmp(a, n, bits_whole << 2) != 0)
      return FALSE;
  }
 
  if (bits_incomplete)
  {
    uint32_t mask = htonl((0xFFFFFFFFu) << (32 - bits_incomplete));
 
    if ((a[bits_whole] ^ n[bits_whole]) & mask)
      return FALSE;
  }
 
  return TRUE;
}
 
static BOOL option_ends_with(const char* str, const char* ext)
{
  WINPR_ASSERT(str);
  WINPR_ASSERT(ext);
  const size_t strLen = strlen(str);
  const size_t extLen = strlen(ext);
 
  if (strLen < extLen)
    return FALSE;
 
  return _strnicmp(&str[strLen - extLen], ext, extLen) == 0;
}
 
/* no_proxy has no proper definition, so use curl as reference:
 * https://about.gitlab.com/blog/2021/01/27/we-need-to-talk-no-proxy/
 */
static BOOL no_proxy_match_host(const char* val, const char* hostname)
{
  WINPR_ASSERT(val);
  WINPR_ASSERT(hostname);
 
  /* match all */
  if (_stricmp("*", val) == 0)
    return TRUE;
 
  /* Strip leading . */
  if (val[0] == '.')
    val++;
 
  /* Match suffix */
  return option_ends_with(hostname, val);
}
 
static BOOL starts_with(const char* val, const char* prefix)
{
  const size_t plen = strlen(prefix);
  const size_t vlen = strlen(val);
  if (vlen < plen)
    return FALSE;
  return _strnicmp(val, prefix, plen) == 0;
}
 
static BOOL no_proxy_match_ip(const char* val, const char* hostname)
{
  WINPR_ASSERT(val);
  WINPR_ASSERT(hostname);
 
  struct sockaddr_in sa4 = { 0 };
  struct sockaddr_in6 sa6 = { 0 };
 
  if (inet_pton(AF_INET, hostname, &sa4.sin_addr) == 1)
  {
    /* Prefix match */
    if (starts_with(hostname, val))
      return TRUE;
 
    char* sub = strchr(val, '/');
    if (sub)
      *sub++ = '\0';
 
    struct sockaddr_in mask = { 0 };
    if (inet_pton(AF_INET, val, &mask.sin_addr) == 0)
      return FALSE;
 
    /* IP address match */
    if (memcmp(&mask, &sa4, sizeof(mask)) == 0)
      return TRUE;
 
    if (sub)
    {
      const unsigned long usub = strtoul(sub, NULL, 0);
      if ((errno == 0) && (usub <= UINT8_MAX))
        return cidr4_match(&sa4.sin_addr, &mask.sin_addr, (UINT8)usub);
    }
  }
  else if (inet_pton(AF_INET6, hostname, &sa6.sin6_addr) == 1)
  {
    if (val[0] == '[')
      val++;
 
    char str[INET6_ADDRSTRLEN + 1] = { 0 };
    strncpy(str, val, INET6_ADDRSTRLEN);
 
    const size_t len = strnlen(str, INET6_ADDRSTRLEN);
    if (len > 0)
    {
      if (str[len - 1] == ']')
        str[len - 1] = '\0';
    }
 
    /* Prefix match */
    if (starts_with(hostname, str))
      return TRUE;
 
    char* sub = strchr(str, '/');
    if (sub)
      *sub++ = '\0';
 
    struct sockaddr_in6 mask = { 0 };
    if (inet_pton(AF_INET6, str, &mask.sin6_addr) == 0)
      return FALSE;
 
    /* Address match */
    if (memcmp(&mask, &sa6, sizeof(mask)) == 0)
      return TRUE;
 
    if (sub)
    {
      const unsigned long usub = strtoul(sub, NULL, 0);
      if ((errno == 0) && (usub <= UINT8_MAX))
        return cidr6_match(&sa6.sin6_addr, &mask.sin6_addr, (UINT8)usub);
    }
  }
 
  return FALSE;
}
 
static BOOL check_no_proxy(rdpSettings* settings, const char* no_proxy)
{
  const char* delimiter = ", ";
  BOOL result = FALSE;
  char* context = NULL;
 
  if (!no_proxy || !settings)
    return FALSE;
 
  char* copy = _strdup(no_proxy);
 
  if (!copy)
    return FALSE;
 
  char* current = strtok_s(copy, delimiter, &context);
 
  while (current && !result)
  {
    const size_t currentlen = strlen(current);
 
    if (currentlen > 0)
    {
      WLog_DBG(TAG, "%s => %s (%" PRIdz ")", settings->ServerHostname, current, currentlen);
 
      if (no_proxy_match_host(current, settings->ServerHostname))
        result = TRUE;
      else if (no_proxy_match_ip(current, settings->ServerHostname))
        result = TRUE;
    }
 
    current = strtok_s(NULL, delimiter, &context);
  }
 
  free(copy);
  return result;
}
 
void proxy_read_environment(rdpSettings* settings, char* envname)
{
  const DWORD envlen = GetEnvironmentVariableA(envname, NULL, 0);
 
  if (!envlen || (envlen <= 1))
    return;
 
  char* env = calloc(1, envlen);
 
  if (!env)
  {
    WLog_ERR(TAG, "Not enough memory");
    return;
  }
 
  if (GetEnvironmentVariableA(envname, env, envlen) == envlen - 1)
  {
    if (_strnicmp("NO_PROXY", envname, 9) == 0)
    {
      if (check_no_proxy(settings, env))
      {
        WLog_INFO(TAG, "deactivating proxy: %s [%s=%s]",
                  freerdp_settings_get_string(settings, FreeRDP_ServerHostname), envname,
                  env);
        if (!freerdp_settings_set_uint32(settings, FreeRDP_ProxyType, PROXY_TYPE_NONE))
          WLog_WARN(TAG, "failed to set FreeRDP_ProxyType=PROXY_TYPE_NONE");
      }
    }
    else
    {
      if (!proxy_parse_uri(settings, env))
      {
        WLog_WARN(
            TAG, "Error while parsing proxy URI from environment variable; ignoring proxy");
      }
    }
  }
 
  free(env);
}
 
BOOL proxy_parse_uri(rdpSettings* settings, const char* uri_in)
{
  BOOL rc = FALSE;
  const char* protocol = "";
  UINT16 port = 0;
 
  if (!settings || !uri_in)
    return FALSE;
 
  char* uri_copy = _strdup(uri_in);
  char* uri = uri_copy;
  if (!uri)
    goto fail;
 
  {
    char* p = strstr(uri, "://");
    if (p)
    {
      *p = '\0';
 
      if (_stricmp("no_proxy", uri) == 0)
      {
        if (!freerdp_settings_set_uint32(settings, FreeRDP_ProxyType, PROXY_TYPE_IGNORE))
          goto fail;
      }
      if (_stricmp("http", uri) == 0)
      {
        if (!freerdp_settings_set_uint32(settings, FreeRDP_ProxyType, PROXY_TYPE_HTTP))
          goto fail;
        protocol = "http";
      }
      else if (_stricmp("socks5", uri) == 0)
      {
        if (!freerdp_settings_set_uint32(settings, FreeRDP_ProxyType, PROXY_TYPE_SOCKS))
          goto fail;
        protocol = "socks5";
      }
      else
      {
        WLog_ERR(TAG, "Only HTTP and SOCKS5 proxies supported by now");
        goto fail;
      }
 
      uri = p + 3;
    }
    else
    {
      /* default proxy protocol is http */
      if (!freerdp_settings_set_uint32(settings, FreeRDP_ProxyType, PROXY_TYPE_HTTP))
        goto fail;
      protocol = "http";
    }
  }
 
  /* uri is now [user:password@]hostname:port */
  {
    char* atPtr = strrchr(uri, '@');
 
    if (atPtr)
    {
      /* got a login / password,
       *         atPtr
       *         v
       * [user:password@]hostname:port
       *    ^
       *    colonPtr
       */
      char* colonPtr = strchr(uri, ':');
 
      if (!colonPtr || (colonPtr > atPtr))
      {
        WLog_ERR(TAG, "invalid syntax for proxy (contains no password)");
        goto fail;
      }
 
      *colonPtr = '\0';
      if (!freerdp_settings_set_string(settings, FreeRDP_ProxyUsername, uri))
      {
        WLog_ERR(TAG, "unable to allocate proxy username");
        goto fail;
      }
 
      *atPtr = '\0';
 
      if (!freerdp_settings_set_string(settings, FreeRDP_ProxyPassword, colonPtr + 1))
      {
        WLog_ERR(TAG, "unable to allocate proxy password");
        goto fail;
      }
 
      uri = atPtr + 1;
    }
  }
 
  {
    char* p = strchr(uri, ':');
 
    if (p)
    {
      LONGLONG val = 0;
 
      if (!value_to_int(&p[1], &val, 0, UINT16_MAX))
      {
        WLog_ERR(TAG, "invalid syntax for proxy (invalid port)");
        goto fail;
      }
 
      if (val == 0)
      {
        WLog_ERR(TAG, "invalid syntax for proxy (port missing)");
        goto fail;
      }
 
      port = (UINT16)val;
      *p = '\0';
    }
    else
    {
      if (_stricmp("http", protocol) == 0)
      {
        /* The default is 80. Also for Proxies. */
        port = 80;
      }
      else
      {
        port = 1080;
      }
 
      WLog_DBG(TAG, "setting default proxy port: %" PRIu16, port);
    }
 
    if (!freerdp_settings_set_uint16(settings, FreeRDP_ProxyPort, port))
      goto fail;
  }
  {
    char* p = strchr(uri, '/');
    if (p)
      *p = '\0';
    if (!freerdp_settings_set_string(settings, FreeRDP_ProxyHostname, uri))
      goto fail;
  }
 
  if (_stricmp("", uri) == 0)
  {
    WLog_ERR(TAG, "invalid syntax for proxy (hostname missing)");
    goto fail;
  }
 
  if (freerdp_settings_get_string(settings, FreeRDP_ProxyUsername))
  {
    WLog_INFO(TAG, "Parsed proxy configuration: %s://%s:%s@%s:%" PRIu16, protocol,
              freerdp_settings_get_string(settings, FreeRDP_ProxyUsername), "******",
              freerdp_settings_get_string(settings, FreeRDP_ProxyHostname),
              freerdp_settings_get_uint16(settings, FreeRDP_ProxyPort));
  }
  else
  {
    WLog_INFO(TAG, "Parsed proxy configuration: %s://%s:%" PRIu16, protocol,
              freerdp_settings_get_string(settings, FreeRDP_ProxyHostname),
              freerdp_settings_get_uint16(settings, FreeRDP_ProxyPort));
  }
  rc = TRUE;
 
fail:
  if (!rc)
    WLog_WARN(TAG, "Failed to parse proxy configuration: %s://%s:%" PRIu16, protocol, uri,
              port);
  free(uri_copy);
  return rc;
}
 
BOOL proxy_connect(rdpContext* context, BIO* bufferedBio, const char* proxyUsername,
                   const char* proxyPassword, const char* hostname, UINT16 port)
{
  WINPR_ASSERT(context);
  rdpSettings* settings = context->settings;
 
  switch (freerdp_settings_get_uint32(settings, FreeRDP_ProxyType))
  {
    case PROXY_TYPE_NONE:
    case PROXY_TYPE_IGNORE:
      return TRUE;
 
    case PROXY_TYPE_HTTP:
      return http_proxy_connect(context, bufferedBio, proxyUsername, proxyPassword, hostname,
                                port);
 
    case PROXY_TYPE_SOCKS:
      return socks_proxy_connect(context, bufferedBio, proxyUsername, proxyPassword, hostname,
                                 port);
 
    default:
      WLog_ERR(TAG, "Invalid internal proxy configuration");
      return FALSE;
  }
}
 
static const char* get_response_header(char* response)
{
  char* current_pos = strchr(response, '\r');
  if (!current_pos)
    current_pos = strchr(response, '\n');
 
  if (current_pos)
    *current_pos = '\0';
 
  return response;
}
 
static BOOL http_proxy_connect(rdpContext* context, BIO* bufferedBio, const char* proxyUsername,
                               const char* proxyPassword, const char* hostname, UINT16 port)
{
  BOOL rc = FALSE;
  int status = 0;
  wStream* s = NULL;
  char port_str[10] = { 0 };
  char recv_buf[256] = { 0 };
  char* eol = NULL;
  size_t resultsize = 0;
  size_t reserveSize = 0;
  size_t portLen = 0;
  size_t hostLen = 0;
  const char connect[] = "CONNECT ";
  const char httpheader[] = " HTTP/1.1" CRLF "Host: ";
 
  WINPR_ASSERT(context);
  WINPR_ASSERT(bufferedBio);
  WINPR_ASSERT(hostname);
  const UINT32 timeout =
      freerdp_settings_get_uint32(context->settings, FreeRDP_TcpConnectTimeout);
 
  _itoa_s(port, port_str, sizeof(port_str), 10);
 
  hostLen = strlen(hostname);
  portLen = strnlen(port_str, sizeof(port_str));
  reserveSize = strlen(connect) + (hostLen + 1 + portLen) * 2 + strlen(httpheader);
  s = Stream_New(NULL, reserveSize);
  if (!s)
    goto fail;
 
  Stream_Write(s, connect, strlen(connect));
  Stream_Write(s, hostname, hostLen);
  Stream_Write_UINT8(s, ':');
  Stream_Write(s, port_str, portLen);
  Stream_Write(s, httpheader, strlen(httpheader));
  Stream_Write(s, hostname, hostLen);
  Stream_Write_UINT8(s, ':');
  Stream_Write(s, port_str, portLen);
 
  if (proxyUsername && proxyPassword)
  {
    const int length = _scprintf("%s:%s", proxyUsername, proxyPassword);
    if (length > 0)
    {
      const size_t size = (size_t)length + 1ull;
      char* creds = (char*)malloc(size);
 
      if (!creds)
        goto fail;
      else
      {
        const char basic[] = CRLF "Proxy-Authorization: Basic ";
        char* base64 = NULL;
 
        (void)sprintf_s(creds, size, "%s:%s", proxyUsername, proxyPassword);
        base64 = crypto_base64_encode((const BYTE*)creds, size - 1);
 
        if (!base64 || !Stream_EnsureRemainingCapacity(s, strlen(basic) + strlen(base64)))
        {
          free(base64);
          free(creds);
          goto fail;
        }
        Stream_Write(s, basic, strlen(basic));
        Stream_Write(s, base64, strlen(base64));
 
        free(base64);
      }
      free(creds);
    }
  }
 
  if (!Stream_EnsureRemainingCapacity(s, 4))
    goto fail;
 
  Stream_Write(s, CRLF CRLF, 4);
  ERR_clear_error();
 
  {
    const size_t pos = Stream_GetPosition(s);
    if (pos > INT32_MAX)
      goto fail;
 
    status = BIO_write(bufferedBio, Stream_Buffer(s), WINPR_ASSERTING_INT_CAST(int, pos));
  }
 
  if ((status < 0) || ((size_t)status != Stream_GetPosition(s)))
  {
    WLog_ERR(TAG, "HTTP proxy: failed to write CONNECT request");
    goto fail;
  }
 
  /* Read result until CR-LF-CR-LF.
   * Keep recv_buf a null-terminated string. */
  {
    const UINT64 start = GetTickCount64();
    while (strstr(recv_buf, CRLF CRLF) == NULL)
    {
      if (resultsize >= sizeof(recv_buf) - 1)
      {
        WLog_ERR(TAG, "HTTP Reply headers too long: %s", get_response_header(recv_buf));
        goto fail;
      }
      const size_t rdsize = sizeof(recv_buf) - resultsize - 1ULL;
 
      ERR_clear_error();
 
      WINPR_ASSERT(rdsize <= INT32_MAX);
      status = BIO_read(bufferedBio, (BYTE*)recv_buf + resultsize, (int)rdsize);
 
      if (status < 0)
      {
        /* Error? */
        if (!freerdp_shall_disconnect_context(context) && BIO_should_retry(bufferedBio))
        {
          USleep(100);
          continue;
        }
 
        WLog_ERR(TAG, "Failed reading reply from HTTP proxy (Status %d)", status);
        goto fail;
      }
      else if (status == 0)
      {
        const UINT64 now = GetTickCount64();
        const UINT64 diff = now - start;
        if (freerdp_shall_disconnect_context(context) || (now < start) || (diff > timeout))
        {
          /* Error? */
          WLog_ERR(TAG, "Failed reading reply from HTTP proxy (BIO_read returned zero)");
          goto fail;
        }
        Sleep(10);
      }
 
      resultsize += WINPR_ASSERTING_INT_CAST(size_t, status);
    }
  }
 
  /* Extract HTTP status line */
  eol = strchr(recv_buf, '\r');
 
  if (!eol)
  {
    /* should never happen */
    goto fail;
  }
 
  *eol = '\0';
  WLog_INFO(TAG, "HTTP Proxy: %s", recv_buf);
 
  if (strnlen(recv_buf, sizeof(recv_buf)) < 12)
    goto fail;
 
  recv_buf[7] = 'X';
 
  if (strncmp(recv_buf, "HTTP/1.X 200", 12) != 0)
    goto fail;
 
  rc = TRUE;
fail:
  Stream_Free(s, TRUE);
  return rc;
}
 
static int recv_socks_reply(rdpContext* context, BIO* bufferedBio, BYTE* buf, int len, char* reason,
                            BYTE checkVer)
{
  int status = 0;
 
  WINPR_ASSERT(context);
 
  const UINT32 timeout =
      freerdp_settings_get_uint32(context->settings, FreeRDP_TcpConnectTimeout);
  const UINT64 start = GetTickCount64();
  for (;;)
  {
    ERR_clear_error();
    status = BIO_read(bufferedBio, buf, len);
 
    if (status > 0)
    {
      break;
    }
    else if (status < 0)
    {
      /* Error? */
      if (!freerdp_shall_disconnect_context(context) && BIO_should_retry(bufferedBio))
      {
        USleep(100);
        continue;
      }
 
      WLog_ERR(TAG, "Failed reading %s reply from SOCKS proxy (Status %d)", reason, status);
      return -1;
    }
    else if (status == 0)
    {
      const UINT64 now = GetTickCount64();
      const UINT64 diff = now - start;
      if (freerdp_shall_disconnect_context(context) || (now < start) || (diff > timeout))
      {
        /* Error? */
        WLog_ERR(TAG, "Failed reading %s reply from SOCKS proxy (BIO_read returned zero)",
                 reason);
        return status;
      }
      Sleep(10);
    }
    else // if (status == 0)
    {
      /* Error? */
      WLog_ERR(TAG, "Failed reading %s reply from SOCKS proxy (BIO_read returned zero)",
               reason);
      return -1;
    }
  }
 
  if (status < 2)
  {
    WLog_ERR(TAG, "SOCKS Proxy reply packet too short (%s)", reason);
    return -1;
  }
 
  if (buf[0] != checkVer)
  {
    WLog_ERR(TAG, "SOCKS Proxy version is not 5 (%s)", reason);
    return -1;
  }
 
  return status;
}
 
static BOOL socks_proxy_userpass(rdpContext* context, BIO* bufferedBio, const char* proxyUsername,
                                 const char* proxyPassword)
{
  WINPR_ASSERT(context);
  WINPR_ASSERT(bufferedBio);
 
  if (!proxyUsername || !proxyPassword)
  {
    WLog_ERR(TAG, "%s invalid username (%p) or password (%p)", logprefix, proxyUsername,
             proxyPassword);
    return FALSE;
  }
 
  const size_t usernameLen = (BYTE)strnlen(proxyUsername, 256);
  if (usernameLen > 255)
  {
    WLog_ERR(TAG, "%s username too long (%" PRIuz ", max=255)", logprefix, usernameLen);
    return FALSE;
  }
 
  const size_t userpassLen = (BYTE)strnlen(proxyPassword, 256);
  if (userpassLen > 255)
  {
    WLog_ERR(TAG, "%s password too long (%" PRIuz ", max=255)", logprefix, userpassLen);
    return FALSE;
  }
 
  /* user/password v1 method */
  {
    BYTE buf[2 * 255 + 3] = { 0 };
    size_t offset = 0;
    buf[offset++] = 1;
 
    buf[offset++] = WINPR_ASSERTING_INT_CAST(uint8_t, usernameLen);
    memcpy(&buf[offset], proxyUsername, usernameLen);
    offset += usernameLen;
 
    buf[offset++] = WINPR_ASSERTING_INT_CAST(uint8_t, userpassLen);
    memcpy(&buf[offset], proxyPassword, userpassLen);
    offset += userpassLen;
 
    ERR_clear_error();
    const int ioffset = WINPR_ASSERTING_INT_CAST(int, offset);
    const int status = BIO_write(bufferedBio, buf, ioffset);
 
    if (status != ioffset)
    {
      WLog_ERR(TAG, "%s error writing user/password request", logprefix);
      return FALSE;
    }
  }
 
  BYTE buf[2] = { 0 };
  const int status = recv_socks_reply(context, bufferedBio, buf, sizeof(buf), "AUTH REQ", 1);
 
  if (status < 2)
    return FALSE;
 
  if (buf[1] != 0x00)
  {
    WLog_ERR(TAG, "%s invalid user/password", logprefix);
    return FALSE;
  }
  return TRUE;
}
 
static BOOL socks_proxy_connect(rdpContext* context, BIO* bufferedBio, const char* proxyUsername,
                                const char* proxyPassword, const char* hostname, UINT16 port)
{
  BYTE nauthMethods = 1;
  const size_t hostnlen = strnlen(hostname, 255);
 
  if (proxyUsername || proxyPassword)
    nauthMethods++;
 
  /* select auth. method */
  {
    const BYTE buf[] = { 5,            /* SOCKS version */
                       nauthMethods, /* #of methods offered */
                       AUTH_M_NO_AUTH, AUTH_M_USR_PASS };
 
    size_t writeLen = sizeof(buf);
    if (nauthMethods <= 1)
      writeLen--;
 
    ERR_clear_error();
    const int iwriteLen = WINPR_ASSERTING_INT_CAST(int, writeLen);
    const int status = BIO_write(bufferedBio, buf, iwriteLen);
 
    if (status != iwriteLen)
    {
      WLog_ERR(TAG, "SOCKS proxy: failed to write AUTH METHOD request", logprefix);
      return FALSE;
    }
  }
 
  {
    BYTE buf[2] = { 0 };
    const int status = recv_socks_reply(context, bufferedBio, buf, sizeof(buf), "AUTH REQ", 5);
 
    if (status <= 0)
      return FALSE;
 
    switch (buf[1])
    {
      case AUTH_M_NO_AUTH:
        WLog_DBG(TAG, "%s (NO AUTH) method was selected", logprefix);
        break;
 
      case AUTH_M_USR_PASS:
        if (nauthMethods < 2)
        {
          WLog_ERR(TAG, "%s USER/PASS method was not proposed to server", logprefix);
          return FALSE;
        }
        if (!socks_proxy_userpass(context, bufferedBio, proxyUsername, proxyPassword))
          return FALSE;
        break;
 
      default:
        WLog_ERR(TAG, "%s unknown method 0x%x was selected by proxy", logprefix, buf[1]);
        return FALSE;
    }
  }
  /* CONN request */
  {
    BYTE buf[262] = { 0 };
    size_t offset = 0;
    buf[offset++] = 5;                 /* SOCKS version */
    buf[offset++] = SOCKS_CMD_CONNECT; /* command */
    buf[offset++] = 0;                 /* 3rd octet is reserved x00 */
 
    if (inet_pton(AF_INET6, hostname, &buf[offset + 1]) == 1)
    {
      buf[offset++] = SOCKS_ADDR_IPV6;
      offset += 16;
    }
    else if (inet_pton(AF_INET, hostname, &buf[offset + 1]) == 1)
    {
      buf[offset++] = SOCKS_ADDR_IPV4;
      offset += 4;
    }
    else
    {
      buf[offset++] = SOCKS_ADDR_FQDN;
      buf[offset++] = WINPR_ASSERTING_INT_CAST(uint8_t, hostnlen);
      memcpy(&buf[offset], hostname, hostnlen);
      offset += hostnlen;
    }
 
    if (offset > sizeof(buf) - 2)
      return FALSE;
 
    /* follows DST.PORT in netw. format */
    buf[offset++] = (port >> 8) & 0xff;
    buf[offset++] = port & 0xff;
 
    ERR_clear_error();
    const int ioffset = WINPR_ASSERTING_INT_CAST(int, offset);
    const int status = BIO_write(bufferedBio, buf, ioffset);
 
    if ((status < 0) || (status != ioffset))
    {
      WLog_ERR(TAG, "SOCKS proxy: failed to write CONN REQ", logprefix);
      return FALSE;
    }
  }
 
  BYTE buf[255] = { 0 };
  const int status = recv_socks_reply(context, bufferedBio, buf, sizeof(buf), "CONN REQ", 5);
 
  if (status < 4)
    return FALSE;
 
  if (buf[1] == 0)
  {
    WLog_INFO(TAG, "Successfully connected to %s:%" PRIu16, hostname, port);
    return TRUE;
  }
 
  if ((buf[1] > 0) && (buf[1] < 9))
    WLog_INFO(TAG, "SOCKS Proxy replied: %s", rplstat[buf[1]]);
  else
    WLog_INFO(TAG, "SOCKS Proxy replied: %" PRIu8 " status not listed in rfc1928", buf[1]);
 
  return FALSE;
}