winscp/source/core/SecureShell.cpp

//---------------------------------------------------------------------------
#include <vcl.h>
#pragma hdrstop

#include "Common.h"
#include "PuttyIntf.h"
#include "Exceptions.h"
#include "Interface.h"
#include "SecureShell.h"
#include "TextsCore.h"
#include "HelpCore.h"
#include "CoreMain.h"
#include <StrUtils.hpp>

#ifndef AUTO_WINSOCK
#include <winsock2.h>
#endif
#include <ws2ipdef.h>
//---------------------------------------------------------------------------
#pragma package(smart_init)
//---------------------------------------------------------------------------
#define MAX_BUFSIZE 32768
//---------------------------------------------------------------------------
const wchar_t HostKeyDelimiter = L';';
//---------------------------------------------------------------------------
struct TPuttyTranslation
{
  const wchar_t * Original;
  int Translation;
  UnicodeString HelpKeyword;
};
//---------------------------------------------------------------------------
__fastcall TSecureShell::TSecureShell(TSessionUI* UI,
  TSessionData * SessionData, TSessionLog * Log, TConfiguration * Configuration)
{
  FUI = UI;
  FSessionData = SessionData;
  FLog = Log;
  FConfiguration = Configuration;
  FActive = false;
  FWaiting = 0;
  FOpened = false;
  FSshImplementation = sshiUnknown;
  OutPtr = NULL;
  Pending = NULL;
  FBackendHandle = NULL;
  ResetConnection();
  FOnCaptureOutput = NULL;
  FOnReceive = NULL;
  FSocket = INVALID_SOCKET;
  FSocketEvent = CreateEvent(NULL, false, false, NULL);
  FFrozen = false;
  FSimple = false;
  FCollectPrivateKeyUsage = false;
  FWaitingForData = 0;
}
//---------------------------------------------------------------------------
__fastcall TSecureShell::~TSecureShell()
{
  DebugAssert(FWaiting == 0);
  Active = false;
  ResetConnection();
  CloseHandle(FSocketEvent);
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::ResetConnection()
{
  FreeBackend();
  ClearStdError();
  PendLen = 0;
  PendSize = 0;
  sfree(Pending);
  Pending = NULL;
  FCWriteTemp = L"";
  ResetSessionInfo();
  FAuthenticating = false;
  FAuthenticated = false;
  FStoredPasswordTried = false;
  FStoredPasswordTriedForKI = false;
  FStoredPassphraseTried = false;
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::ResetSessionInfo()
{
  FSessionInfoValid = false;
  FMaxPacketSize = NULL;
}
//---------------------------------------------------------------------------
inline void __fastcall TSecureShell::UpdateSessionInfo()
{
  if (!FSessionInfoValid)
  {
    FSshVersion = get_ssh_version(FBackendHandle);
    FSessionInfo.ProtocolBaseName = L"SSH";
    FSessionInfo.ProtocolName =
      FORMAT(L"%s-%d", (FSessionInfo.ProtocolBaseName, get_ssh_version(FBackendHandle)));
    FSessionInfo.SecurityProtocolName = FSessionInfo.ProtocolName;

    FSessionInfo.CSCompression =
      FuncToCompression(FSshVersion, get_cscomp(FBackendHandle));
    FSessionInfo.SCCompression =
      FuncToCompression(FSshVersion, get_sccomp(FBackendHandle));

    if (FSshVersion == 1)
    {
      FSessionInfo.CSCipher = CipherNames[FuncToSsh1Cipher(get_cipher(FBackendHandle))];
      FSessionInfo.SCCipher = CipherNames[FuncToSsh1Cipher(get_cipher(FBackendHandle))];
    }
    else
    {
      FSessionInfo.CSCipher = CipherNames[FuncToSsh2Cipher(get_cscipher(FBackendHandle))];
      FSessionInfo.SCCipher = CipherNames[FuncToSsh2Cipher(get_sccipher(FBackendHandle))];
    }

    FSessionInfoValid = true;
  }
}
//---------------------------------------------------------------------------
const TSessionInfo & __fastcall TSecureShell::GetSessionInfo()
{
  if (!FSessionInfoValid)
  {
    UpdateSessionInfo();
  }
  return FSessionInfo;
}
//---------------------------------------------------------------------
UnicodeString __fastcall TSecureShell::GetHostKeyFingerprint()
{
  return FSessionInfo.HostKeyFingerprint;
}
//---------------------------------------------------------------------
Conf * __fastcall TSecureShell::StoreToConfig(TSessionData * Data, bool Simple)
{
  Conf * conf = conf_new();

  DebugAssert((asOn == FORCE_ON) && (asOff == FORCE_OFF) && (asAuto == AUTO));

  #define CONF_ssh_cipherlist_MAX CIPHER_MAX
  #define CONF_DEF_INT_NONE(KEY) conf_set_int(conf, KEY, 0);
  #define CONF_DEF_STR_NONE(KEY) conf_set_str(conf, KEY, "");
  // noop, used only for these and we set the first four explicitly below and latter two are not used in our code
  #define CONF_DEF_INT_INT(KEY) DebugAssert((KEY == CONF_ssh_cipherlist) || (KEY == CONF_ssh_kexlist) || (KEY == CONF_ssh_gsslist) || (KEY == CONF_ssh_hklist) || (KEY == CONF_colours) || (KEY == CONF_wordness));
  // noop, used only for these four and they all can handle undef value
  #define CONF_DEF_STR_STR(KEY) DebugAssert((KEY == CONF_ttymodes) || (KEY == CONF_portfwd) || (KEY == CONF_environmt) || (KEY == CONF_ssh_manual_hostkeys));
  // noop, not used in our code
  #define CONF_DEF_FONT_NONE(KEY) DebugAssert((KEY == CONF_font) || (KEY == CONF_boldfont) || (KEY == CONF_widefont) || (KEY == CONF_wideboldfont));
  #define CONF_DEF_FILENAME_NONE(KEY) \
    { \
      Filename * filename = filename_from_str(""); \
      conf_set_filename(conf, KEY, filename); \
      filename_free(filename); \
    }
  #define CONF_SET_DEFAULT(VALTYPE, KEYTYPE, KEYWORD) CONF_DEF_ ## VALTYPE ## _ ## KEYTYPE(CONF_ ## KEYWORD);
  CONFIG_OPTIONS(CONF_SET_DEFAULT);
  #undef CONF_SET_DEFAULT
  #undef CONF_DEF_FILENAME_NONE
  #undef CONF_DEF_FONT_NONE
  #undef CONF_DEF_STR_STR
  #undef CONF_DEF_INT_INT
  #undef CONF_DEF_STR_NONE
  #undef CONF_DEF_INT_NONE

  // user-configurable settings
  conf_set_str(conf, CONF_host, AnsiString(Data->HostNameExpanded).c_str());
  conf_set_str(conf, CONF_username, UTF8String(Data->UserNameExpanded).c_str());
  conf_set_int(conf, CONF_port, Data->PortNumber);
  conf_set_int(conf, CONF_protocol, PROT_SSH);
  conf_set_int(conf, CONF_change_password, Data->ChangePassword);
  // always set 0, as we will handle keepalives ourselves to avoid
  // multi-threaded issues in putty timer list
  conf_set_int(conf, CONF_ping_interval, 0);
  conf_set_int(conf, CONF_compression, Data->Compression);
  conf_set_int(conf, CONF_tryagent, Data->TryAgent);
  conf_set_int(conf, CONF_agentfwd, Data->AgentFwd);
  conf_set_int(conf, CONF_addressfamily, Data->AddressFamily);
  conf_set_str(conf, CONF_ssh_rekey_data, AnsiString(Data->RekeyData).c_str());
  conf_set_int(conf, CONF_ssh_rekey_time, Data->RekeyTime);

  DebugAssert(CIPHER_MAX == CIPHER_COUNT);
  for (int c = 0; c < CIPHER_COUNT; c++)
  {
    int pcipher;
    switch (Data->Cipher[c]) {
      case cipWarn: pcipher = CIPHER_WARN; break;
      case cip3DES: pcipher = CIPHER_3DES; break;
      case cipBlowfish: pcipher = CIPHER_BLOWFISH; break;
      case cipAES: pcipher = CIPHER_AES; break;
      case cipDES: pcipher = CIPHER_DES; break;
      case cipArcfour: pcipher = CIPHER_ARCFOUR; break;
      case cipChaCha20: pcipher = CIPHER_CHACHA20; break;
      default: DebugFail();
    }
    conf_set_int_int(conf, CONF_ssh_cipherlist, c, pcipher);
  }

  DebugAssert(KEX_MAX == KEX_COUNT);
  for (int k = 0; k < KEX_COUNT; k++)
  {
    int pkex;
    switch (Data->Kex[k]) {
      case kexWarn: pkex = KEX_WARN; break;
      case kexDHGroup1: pkex = KEX_DHGROUP1; break;
      case kexDHGroup14: pkex = KEX_DHGROUP14; break;
      case kexDHGEx: pkex = KEX_DHGEX; break;
      case kexRSA: pkex = KEX_RSA; break;
      case kexECDH: pkex = KEX_ECDH; break;
      default: DebugFail();
    }
    conf_set_int_int(conf, CONF_ssh_kexlist, k, pkex);
  }

  DebugAssert(HK_MAX == HOSTKEY_COUNT);
  for (int h = 0; h < HOSTKEY_COUNT; h++)
  {
    int phk;
    switch (Data->HostKeys[h]) {
      case hkWarn: phk = HK_WARN; break;
      case hkRSA: phk = HK_RSA; break;
      case hkDSA: phk = hkDSA; break;
      case hkECDSA: phk = HK_ECDSA; break;
      case hkED25519: phk = HK_ED25519; break;
      default: DebugFail();
    }
    conf_set_int_int(conf, CONF_ssh_hklist, h, phk);
  }

  DebugAssert(ngsslibs == GSSLIB_COUNT);
  for (int g = 0; g < GSSLIB_COUNT; g++)
  {
    int pgsslib;
    switch (Data->GssLib[g]) {
      case gssGssApi32: pgsslib = 0; break;
      case gssSspi: pgsslib = 1; break;
      case gssCustom: pgsslib = 2; break;
      default: DebugFail();
    }
    conf_set_int_int(conf, CONF_ssh_gsslist, g, pgsslib);
  }
  Filename * GssLibCustomFileName = filename_from_str(UTF8String(Data->GssLibCustom).c_str());
  conf_set_filename(conf, CONF_ssh_gss_custom, GssLibCustomFileName);
  filename_free(GssLibCustomFileName);

  UnicodeString SPublicKeyFile = Data->PublicKeyFile;
  if (SPublicKeyFile.IsEmpty()) SPublicKeyFile = Configuration->DefaultKeyFile;
  // StripPathQuotes should not be needed as we do not feed quotes anymore
  SPublicKeyFile = StripPathQuotes(ExpandEnvironmentVariables(SPublicKeyFile));
  Filename * KeyFileFileName = filename_from_str(UTF8String(SPublicKeyFile).c_str());
  conf_set_filename(conf, CONF_keyfile, KeyFileFileName);
  filename_free(KeyFileFileName);

  conf_set_int(conf, CONF_sshprot, Data->SshProt);
  conf_set_int(conf, CONF_ssh2_des_cbc, Data->Ssh2DES);
  conf_set_int(conf, CONF_ssh_no_userauth, Data->SshNoUserAuth);
  conf_set_int(conf, CONF_try_tis_auth, Data->AuthTIS);
  conf_set_int(conf, CONF_try_ki_auth, Data->AuthKI);
  conf_set_int(conf, CONF_try_gssapi_auth, Data->AuthGSSAPI);
  conf_set_int(conf, CONF_gssapifwd, Data->GSSAPIFwdTGT);
  conf_set_int(conf, CONF_change_username, Data->ChangeUsername);

  conf_set_int(conf, CONF_proxy_type, Data->ProxyMethod);
  conf_set_str(conf, CONF_proxy_host, AnsiString(Data->ProxyHost).c_str());
  conf_set_int(conf, CONF_proxy_port, Data->ProxyPort);
  conf_set_str(conf, CONF_proxy_username, UTF8String(Data->ProxyUsername).c_str());
  conf_set_str(conf, CONF_proxy_password, UTF8String(Data->ProxyPassword).c_str());
  if (Data->ProxyMethod == pmCmd)
  {
    conf_set_str(conf, CONF_proxy_telnet_command, AnsiString(Data->ProxyLocalCommand).c_str());
  }
  else
  {
    conf_set_str(conf, CONF_proxy_telnet_command, AnsiString(Data->ProxyTelnetCommand).c_str());
  }
  conf_set_int(conf, CONF_proxy_dns, Data->ProxyDNS);
  conf_set_int(conf, CONF_even_proxy_localhost, Data->ProxyLocalhost);

  conf_set_int(conf, CONF_sshbug_ignore1, Data->Bug[sbIgnore1]);
  conf_set_int(conf, CONF_sshbug_plainpw1, Data->Bug[sbPlainPW1]);
  conf_set_int(conf, CONF_sshbug_rsa1, Data->Bug[sbRSA1]);
  conf_set_int(conf, CONF_sshbug_hmac2, Data->Bug[sbHMAC2]);
  conf_set_int(conf, CONF_sshbug_derivekey2, Data->Bug[sbDeriveKey2]);
  conf_set_int(conf, CONF_sshbug_rsapad2, Data->Bug[sbRSAPad2]);
  conf_set_int(conf, CONF_sshbug_rekey2, Data->Bug[sbRekey2]);
  conf_set_int(conf, CONF_sshbug_pksessid2, Data->Bug[sbPKSessID2]);
  conf_set_int(conf, CONF_sshbug_maxpkt2, Data->Bug[sbMaxPkt2]);
  conf_set_int(conf, CONF_sshbug_ignore2, Data->Bug[sbIgnore2]);
  conf_set_int(conf, CONF_sshbug_winadj, Data->Bug[sbWinAdj]);
  conf_set_int(conf, CONF_sshbug_oldgex2, Data->Bug[sbOldGex2]);
  conf_set_int(conf, CONF_sshbug_chanreq, Data->Bug[sbChanReq]);

  if (!Data->TunnelPortFwd.IsEmpty())
  {
    DebugAssert(!Simple);
    UnicodeString TunnelPortFwd = Data->TunnelPortFwd;
    while (!TunnelPortFwd.IsEmpty())
    {
      UnicodeString Buf = CutToChar(TunnelPortFwd, L',', true);
      AnsiString Key = AnsiString(CutToChar(Buf, L'\t', true));
      AnsiString Value = AnsiString(Buf);
      conf_set_str_str(conf, CONF_portfwd, Key.c_str(), Value.c_str());
    }

    // when setting up a tunnel, do not open shell/sftp
    conf_set_int(conf, CONF_ssh_no_shell, TRUE);
  }
  else
  {
    DebugAssert(Simple);
    conf_set_int(conf, CONF_ssh_simple, Data->SshSimple && Simple);

    if (Data->FSProtocol == fsSCPonly)
    {
      conf_set_int(conf, CONF_ssh_subsys, FALSE);
      if (Data->Shell.IsEmpty())
      {
        // Following forces Putty to open default shell
        // see ssh.c: do_ssh2_authconn() and ssh1_protocol()
        conf_set_str(conf, CONF_remote_cmd, "");
      }
      else
      {
        conf_set_str(conf, CONF_remote_cmd, AnsiString(Data->Shell).c_str());
      }
    }
    else
    {
      if (Data->SftpServer.IsEmpty())
      {
        conf_set_int(conf, CONF_ssh_subsys, TRUE);
        conf_set_str(conf, CONF_remote_cmd, "sftp");
      }
      else
      {
        conf_set_int(conf, CONF_ssh_subsys, FALSE);
        conf_set_str(conf, CONF_remote_cmd, AnsiString(Data->SftpServer).c_str());
      }

      if (Data->FSProtocol != fsSFTPonly)
      {
        conf_set_int(conf, CONF_ssh_subsys2, FALSE);
        if (Data->Shell.IsEmpty())
        {
          // Following forces Putty to open default shell
          // see ssh.c: do_ssh2_authconn() and ssh1_protocol()
          conf_set_str(conf, CONF_remote_cmd2, "");
          // PuTTY ignores CONF_remote_cmd2 set to "",
          // so we have to enforce it
          // (CONF_force_remote_cmd2 is our config option)
          conf_set_int(conf, CONF_force_remote_cmd2, 1);
        }
        else
        {
          conf_set_str(conf, CONF_remote_cmd2, AnsiString(Data->Shell).c_str());
        }
      }

      if ((Data->FSProtocol == fsSFTPonly) && Data->SftpServer.IsEmpty())
      {
        // see psftp_connect() from psftp.c
        conf_set_int(conf, CONF_ssh_subsys2, FALSE);
        conf_set_str(conf, CONF_remote_cmd2,
          "test -x /usr/lib/sftp-server && exec /usr/lib/sftp-server\n"
          "test -x /usr/local/lib/sftp-server && exec /usr/local/lib/sftp-server\n"
          "exec sftp-server");
      }
    }
  }

  conf_set_int(conf, CONF_connect_timeout, Data->Timeout * MSecsPerSec);
  conf_set_int(conf, CONF_sndbuf, Data->SendBuf);

  // permanent settings
  conf_set_int(conf, CONF_nopty, TRUE);
  conf_set_int(conf, CONF_tcp_keepalives, 0);
  conf_set_int(conf, CONF_ssh_show_banner, TRUE);
  conf_set_int(conf, CONF_proxy_log_to_term, FORCE_OFF);

  conf_set_str(conf, CONF_loghost, AnsiString(Data->LogicalHostName).c_str());

  return conf;
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::Open()
{
  FBackend = &ssh_backend;
  ResetConnection();

  FAuthenticating = false;
  FAuthenticated = false;
  FLastSendBufferUpdate = 0;

  // do not use UTF-8 until decided otherwise (see TSCPFileSystem::DetectUtf())
  FUtfStrings = false;

  Active = false;

  FAuthenticationLog = L"";
  FNoConnectionResponse = false;
  FUI->Information(LoadStr(STATUS_LOOKUPHOST), true);

  try
  {
    char * RealHost;
    FreeBackend(); // in case we are reconnecting
    const char * InitError;
    Conf * conf = StoreToConfig(FSessionData, Simple);
    FSendBuf = FSessionData->SendBuf;
    try
    {
      InitError = FBackend->init(this, &FBackendHandle, conf,
        AnsiString(FSessionData->HostNameExpanded).c_str(), FSessionData->PortNumber, &RealHost,
        (FSessionData->TcpNoDelay ? 1 : 0),
        conf_get_int(conf, CONF_tcp_keepalives));
    }
    __finally
    {
      conf_free(conf);
    }
    sfree(RealHost);
    if (InitError)
    {
      PuttyFatalError(InitError);
    }
    FUI->Information(LoadStr(STATUS_CONNECT), true);
    Init();

    CheckConnection(CONNECTION_FAILED);
  }
  catch (Exception & E)
  {
    if (FNoConnectionResponse && TryFtp())
    {
      Configuration->Usage->Inc(L"ProtocolSuggestions");
      // HELP_FTP_SUGGESTION won't be used as all errors that set
      // FNoConnectionResponse have already their own help keyword
      FUI->FatalError(&E, LoadStr(FTP_SUGGESTION), HELP_FTP_SUGGESTION);
    }
    else
    {
      throw;
    }
  }
  FLastDataSent = Now();

  FSessionInfo.LoginTime = Now();

  FAuthenticating = false;
  FAuthenticated = true;
  FUI->Information(LoadStr(STATUS_AUTHENTICATED), true);

  ResetSessionInfo();

  DebugAssert(!FSessionInfo.SshImplementation.IsEmpty());
  FOpened = true;

  UnicodeString SshImplementation = GetSessionInfo().SshImplementation;
  if (// e.g. "OpenSSH_5.3"
      (SshImplementation.Pos(L"OpenSSH") == 1) ||
      // Sun SSH is based on OpenSSH (suffers the same bugs)
      (SshImplementation.Pos(L"Sun_SSH") == 1))
  {
    FSshImplementation = sshiOpenSSH;
  }
  // e.g. "mod_sftp/0.9.8"
  else if (SshImplementation.Pos(L"mod_sftp") == 1)
  {
    FSshImplementation = sshiProFTPD;
  }
  // e.g. "5.25 FlowSsh: Bitvise SSH Server (WinSSHD) 6.07: free only for personal non-commercial use"
  else if (SshImplementation.Pos(L"FlowSsh") > 0)
  {
    FSshImplementation = sshiBitvise;
  }
  // e.g. "srtSSHServer_10.00"
  else if (ContainsText(SshImplementation, L"srtSSHServer"))
  {
    FSshImplementation = sshiTitan;
  }
  else if (ContainsText(FSessionInfo.SshImplementation, L"OpenVMS"))
  {
    FSshImplementation = sshiOpenVMS;
  }
  else if (ContainsText(FSessionInfo.SshImplementation, L"CerberusFTPServer"))
  {
    FSshImplementation = sshiCerberus;
  }
  else
  {
    FSshImplementation = sshiUnknown;
  }
}
//---------------------------------------------------------------------------
bool __fastcall TSecureShell::TryFtp()
{
  bool Result;
  if (!FConfiguration->TryFtpWhenSshFails)
  {
    Result = false;
  }
  else
  {
    if (((FSessionData->FSProtocol != fsSFTP) && (FSessionData->FSProtocol != fsSFTPonly)) ||
        (FSessionData->PortNumber != SshPortNumber) ||
        FSessionData->Tunnel || (FSessionData->ProxyMethod != ::pmNone))
    {
      LogEvent(L"Using non-standard protocol or port, tunnel or proxy, will not knock FTP port.");
      Result = false;
    }
    else
    {
      LogEvent(L"Knocking FTP port.");

      SOCKET Socket = socket(AF_INET, SOCK_STREAM, 0);
      Result = (Socket != INVALID_SOCKET);
      if (Result)
      {
        LPHOSTENT HostEntry = gethostbyname(AnsiString(FSessionData->HostNameExpanded).c_str());
        Result = (HostEntry != NULL);
        if (Result)
        {
          SOCKADDR_IN Address;

          memset(&Address, 0, sizeof(Address));
          Address.sin_family = AF_INET;
          int Port = FtpPortNumber;
          Address.sin_port = htons(static_cast<short>(Port));
          Address.sin_addr.s_addr = *((unsigned long *)*HostEntry->h_addr_list);

          HANDLE Event = CreateEvent(NULL, false, false, NULL);
          Result = (WSAEventSelect(Socket, (WSAEVENT)Event, FD_CONNECT | FD_CLOSE) != SOCKET_ERROR);

          if (Result)
          {
            Result =
              (connect(Socket, reinterpret_cast<sockaddr *>(&Address), sizeof(Address)) != SOCKET_ERROR) ||
              (WSAGetLastError() == WSAEWOULDBLOCK);
            if (Result)
            {
              Result = (WaitForSingleObject(Event, 2000) == WAIT_OBJECT_0);
            }
          }
          CloseHandle(Event);
        }
        closesocket(Socket);
      }

      if (Result)
      {
        LogEvent(L"FTP port opened, will suggest using FTP protocol.");
      }
      else
      {
        LogEvent(L"FTP port did not open.");
      }
    }
  }
  return Result;
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::Init()
{
  try
  {
    try
    {
      // Recent pscp checks FBackend->exitcode(FBackendHandle) in the loop
      // (see comment in putty revision 8110)
      // It seems that we do not need to do it.

      while (!get_ssh_state_session(FBackendHandle))
      {
        if (Configuration->ActualLogProtocol >= 1)
        {
          LogEvent(L"Waiting for the server to continue with the initialization");
        }
        WaitForData();
      }

      // unless this is tunnel session, it must be safe to send now
      DebugAssert(FBackend->sendok(FBackendHandle) || !FSessionData->TunnelPortFwd.IsEmpty());
    }
    catch(Exception & E)
    {
      if (FAuthenticating && !FAuthenticationLog.IsEmpty())
      {
        FUI->FatalError(&E, FMTLOAD(AUTHENTICATION_LOG, (FAuthenticationLog)));
      }
      else
      {
        throw;
      }
    }
  }
  catch(Exception & E)
  {
    if (FAuthenticating)
    {
      FUI->FatalError(&E, LoadStr(AUTHENTICATION_FAILED));
    }
    else
    {
      throw;
    }
  }
}
//---------------------------------------------------------------------------
UnicodeString __fastcall TSecureShell::ConvertFromPutty(const char * Str, int Length)
{
  int BomLength = strlen(MPEXT_BOM);
  if ((Length >= BomLength) &&
      (strncmp(Str, MPEXT_BOM, BomLength) == 0))
  {
    return UTF8ToString(Str + BomLength, Length - BomLength);
  }
  else
  {
    return AnsiToString(Str, Length);
  }
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::PuttyLogEvent(const char * AStr)
{
  UnicodeString Str = ConvertFromPutty(AStr, strlen(AStr));
  #define SERVER_VERSION_MSG L"Server version: "
  // Gross hack
  if (Str.Pos(SERVER_VERSION_MSG) == 1)
  {
    FSessionInfo.SshVersionString = Str.SubString(wcslen(SERVER_VERSION_MSG) + 1,
      Str.Length() - wcslen(SERVER_VERSION_MSG));

    const wchar_t * Ptr = wcschr(FSessionInfo.SshVersionString.c_str(), L'-');
    if (Ptr != NULL)
    {
      Ptr = wcschr(Ptr + 1, L'-');
    }
    FSessionInfo.SshImplementation = (Ptr != NULL) ? Ptr + 1 : L"";
  }
  #define FORWARDING_FAILURE_MSG L"Forwarded connection refused by server: "
  else if (Str.Pos(FORWARDING_FAILURE_MSG) == 1)
  {
    FLastTunnelError = Str.SubString(wcslen(FORWARDING_FAILURE_MSG) + 1,
      Str.Length() - wcslen(FORWARDING_FAILURE_MSG));

    static const TPuttyTranslation Translation[] = {
      { L"Administratively prohibited [%]", PFWD_TRANSL_ADMIN },
      { L"Connect failed [%]", PFWD_TRANSL_CONNECT },
    };
    TranslatePuttyMessage(Translation, LENOF(Translation), FLastTunnelError);
  }
  LogEvent(Str);
}
//---------------------------------------------------------------------------
TPromptKind __fastcall TSecureShell::IdentifyPromptKind(UnicodeString & Name)
{
  // beware of changing order
  static const TPuttyTranslation NameTranslation[] = {
    { L"SSH login name", USERNAME_TITLE },
    { L"SSH key passphrase", PASSPHRASE_TITLE },
    { L"SSH TIS authentication", SERVER_PROMPT_TITLE },
    { L"SSH CryptoCard authentication", SERVER_PROMPT_TITLE },
    { L"SSH server: %", SERVER_PROMPT_TITLE2 },
    { L"SSH server authentication", SERVER_PROMPT_TITLE },
    { L"SSH password", PASSWORD_TITLE },
    { L"New SSH password", NEW_PASSWORD_TITLE },
  };

  int Index = TranslatePuttyMessage(NameTranslation, LENOF(NameTranslation), Name);

  TPromptKind PromptKind;
  if (Index == 0) // username
  {
    PromptKind = pkUserName;
  }
  else if (Index == 1) // passphrase
  {
    PromptKind = pkPassphrase;
  }
  else if (Index == 2) // TIS
  {
    PromptKind = pkTIS;
  }
  else if (Index == 3) // CryptoCard
  {
    PromptKind = pkCryptoCard;
  }
  else if ((Index == 4) || (Index == 5))
  {
    PromptKind = pkKeybInteractive;
  }
  else if (Index == 6)
  {
    PromptKind = pkPassword;
  }
  else if (Index == 7)
  {
    PromptKind = pkNewPassword;
  }
  else
  {
    PromptKind = pkPrompt;
    DebugFail();
  }

  return PromptKind;
}

//---------------------------------------------------------------------------
bool __fastcall TSecureShell::PromptUser(bool /*ToServer*/,
  UnicodeString AName, bool /*NameRequired*/,
  UnicodeString Instructions, bool InstructionsRequired,
  TStrings * Prompts, TStrings * Results)
{
  // there can be zero prompts!

  DebugAssert(Results->Count == Prompts->Count);

  UnicodeString Name = AName;
  TPromptKind PromptKind = IdentifyPromptKind(Name);

  const TPuttyTranslation * InstructionTranslation = NULL;
  const TPuttyTranslation * PromptTranslation = NULL;
  size_t PromptTranslationCount = 1;
  UnicodeString PromptDesc;

  if (PromptKind == pkUserName)
  {
    static const TPuttyTranslation UsernamePromptTranslation[] = {
      { L"login as: ", USERNAME_PROMPT2 },
    };

    PromptTranslation = UsernamePromptTranslation;
    PromptDesc = L"username";
  }
  else if (PromptKind == pkPassphrase)
  {
    static const TPuttyTranslation PassphrasePromptTranslation[] = {
      { L"Passphrase for key \"%\": ", PROMPT_KEY_PASSPHRASE },
    };

    PromptTranslation = PassphrasePromptTranslation;
    PromptDesc = L"passphrase";
  }
  else if (PromptKind == pkTIS)
  {
    static const TPuttyTranslation TISInstructionTranslation[] = {
      { L"Using TIS authentication.%", TIS_INSTRUCTION },
    };
    static const TPuttyTranslation TISPromptTranslation[] = {
      { L"Response: ", PROMPT_PROMPT },
    };

    InstructionTranslation = TISInstructionTranslation;
    PromptTranslation = TISPromptTranslation;
    PromptDesc = L"tis";
  }
  else if (PromptKind == pkCryptoCard)
  {
    static const TPuttyTranslation CryptoCardInstructionTranslation[] = {
      { L"Using CryptoCard authentication.%", CRYPTOCARD_INSTRUCTION },
    };
    static const TPuttyTranslation CryptoCardPromptTranslation[] = {
      { L"Response: ", PROMPT_PROMPT },
    };

    InstructionTranslation = CryptoCardInstructionTranslation;
    PromptTranslation = CryptoCardPromptTranslation;
    PromptDesc = L"cryptocard";
  }
  else if (PromptKind == pkKeybInteractive)
  {
    static const TPuttyTranslation KeybInteractiveInstructionTranslation[] = {
      { L"Using keyboard-interactive authentication.%", KEYBINTER_INSTRUCTION },
    };
    static const TPuttyTranslation KeybInteractivePromptTranslation[] = {
      // as used by Linux-PAM (pam_exec/pam_exec.c, libpam/pam_get_authtok.c,
      // pam_unix/pam_unix_auth.c, pam_userdb/pam_userdb.c)
      { L"Password: ", PASSWORD_PROMPT },
    };

    InstructionTranslation = KeybInteractiveInstructionTranslation;
    PromptTranslation = KeybInteractivePromptTranslation;
    PromptDesc = L"keyboard interactive";
  }
  else if (PromptKind == pkPassword)
  {
    DebugAssert(Prompts->Count == 1);
    Prompts->Strings[0] = LoadStr(PASSWORD_PROMPT);
    PromptDesc = L"password";
  }
  else if (PromptKind == pkNewPassword)
  {
    // Can be tested with WS_FTP server
    static const TPuttyTranslation NewPasswordPromptTranslation[] = {
      { L"Current password (blank for previously entered password): ", NEW_PASSWORD_CURRENT_PROMPT },
      { L"Enter new password: ", NEW_PASSWORD_NEW_PROMPT },
      { L"Confirm new password: ", NEW_PASSWORD_CONFIRM_PROMPT },
    };
    PromptTranslation = NewPasswordPromptTranslation;
    PromptTranslationCount = LENOF(NewPasswordPromptTranslation);
    PromptDesc = L"new password";
  }
  else
  {
    PromptDesc = L"unknown";
    DebugFail();
  }

  UnicodeString InstructionsLog =
    (Instructions.IsEmpty() ? UnicodeString(L"<no instructions>") : FORMAT(L"\"%s\"", (Instructions)));
  UnicodeString PromptsLog =
    (Prompts->Count > 0 ? FORMAT(L"\"%s\"", (Prompts->Strings[0])) : UnicodeString(L"<no prompt>")) +
    (Prompts->Count > 1 ? FORMAT(L"%d more", (Prompts->Count - 1)) : UnicodeString());
  LogEvent(FORMAT(L"Prompt (%s, \"%s\", %s, %s)", (PromptDesc, AName, InstructionsLog, PromptsLog)));

  Name = Name.Trim();

  if (InstructionTranslation != NULL)
  {
    TranslatePuttyMessage(InstructionTranslation, 1, Instructions);
  }

  // some servers add leading or trailing blank line to make the prompt look prettier
  // on terminal console
  Instructions = Instructions.Trim();

  for (int Index = 0; Index < Prompts->Count; Index++)
  {
    UnicodeString Prompt = Prompts->Strings[Index];
    if (PromptTranslation != NULL)
    {
      TranslatePuttyMessage(PromptTranslation, PromptTranslationCount, Prompt);
    }
    // some servers add leading blank line to make the prompt look prettier
    // on terminal console
    Prompts->Strings[Index] = Prompt.Trim();
  }

  bool Result = false;
  if ((PromptKind == pkTIS) || (PromptKind == pkCryptoCard) ||
      (PromptKind == pkKeybInteractive))
  {
    if (FSessionData->AuthKIPassword && !FSessionData->Password.IsEmpty() &&
        !FStoredPasswordTriedForKI && (Prompts->Count == 1) &&
        FLAGCLEAR(int(Prompts->Objects[0]), pupEcho))
    {
      LogEvent(L"Using stored password.");
      FUI->Information(LoadStr(AUTH_PASSWORD), false);
      Result = true;
      Results->Strings[0] = FSessionData->Password;
      FStoredPasswordTriedForKI = true;
    }
    else if (Instructions.IsEmpty() && !InstructionsRequired && (Prompts->Count == 0))
    {
      LogEvent(L"Ignoring empty SSH server authentication request");
      Result = true;
    }
  }
  else if (PromptKind == pkPassword)
  {
    if (!FSessionData->Password.IsEmpty() && !FStoredPasswordTried)
    {
      LogEvent(L"Using stored password.");
      FUI->Information(LoadStr(AUTH_PASSWORD), false);
      Result = true;
      Results->Strings[0] = FSessionData->Password;
      FStoredPasswordTried = true;
    }
  }
  else if (PromptKind == pkPassphrase)
  {
    if (!FSessionData->Passphrase.IsEmpty() && !FStoredPassphraseTried)
    {
      LogEvent(L"Using configured passphrase.");
      Result = true;
      Results->Strings[0] = FSessionData->Passphrase;
      FStoredPassphraseTried = true;
    }
  }
  else if (PromptKind == pkNewPassword)
  {
    if (FSessionData->ChangePassword)
    {
      FUI->Information(LoadStr(AUTH_CHANGING_PASSWORD), false);

      if (!FSessionData->Password.IsEmpty() && !FSessionData->NewPassword.IsEmpty() && !FStoredPasswordTried)
      {
        LogEvent(L"Using stored password and new password.");
        Result = true;
        DebugAssert(Results->Count == 3);
        Results->Strings[0] = FSessionData->Password;
        Results->Strings[1] = FSessionData->NewPassword;
        Results->Strings[2] = FSessionData->NewPassword;
        FStoredPasswordTried = true;
      }
    }
  }

  if (!Result)
  {
    Result = FUI->PromptUser(FSessionData,
      PromptKind, Name, Instructions, Prompts, Results);

    if (Result)
    {
      if ((Prompts->Count >= 1) &&
          (FLAGSET(int(Prompts->Objects[0]), pupEcho) || Configuration->LogSensitive))
      {
        LogEvent(FORMAT(L"Response: \"%s\"", (Results->Strings[0])));
      }

      if ((PromptKind == pkUserName) && (Prompts->Count == 1))
      {
        FUserName = Results->Strings[0];
      }
    }
  }

  return Result;
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::GotHostKey()
{
  // due to re-key GotHostKey() may be called again later during session
  if (!FAuthenticating && !FAuthenticated)
  {
    FAuthenticating = true;
    if (!FSessionData->ChangePassword)
    {
      FUI->Information(LoadStr(STATUS_AUTHENTICATE), true);
    }
  }
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::CWrite(const char * Data, int Length)
{
  // some messages to stderr may indicate that something has changed with the
  // session, so reset the session info
  ResetSessionInfo();

  // We send only whole line at once, so we have to cache incoming data
  FCWriteTemp += DeleteChar(ConvertFromPutty(Data, Length), L'\r');

  UnicodeString Line;
  // Do we have at least one complete line in std error cache?
  while (FCWriteTemp.Pos(L"\n") > 0)
  {
    UnicodeString Line = CutToChar(FCWriteTemp, L'\n', false);

    FLog->Add(llStdError, Line);

    if (FAuthenticating)
    {
      TranslateAuthenticationMessage(Line);
      FAuthenticationLog += (FAuthenticationLog.IsEmpty() ? L"" : L"\n") + Line;
    }

    FUI->Information(Line, false);
  }
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::RegisterReceiveHandler(TNotifyEvent Handler)
{
  DebugAssert(FOnReceive == NULL);
  FOnReceive = Handler;
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::UnregisterReceiveHandler(TNotifyEvent Handler)
{
  DebugAssert(FOnReceive == Handler);
  DebugUsedParam(Handler);
  FOnReceive = NULL;
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::FromBackend(bool IsStdErr, const unsigned char * Data, int Length)
{
  // Note that we do not apply ConvertFromPutty to Data yet (as opposite to CWrite).
  // as there's no use for this atm.
  CheckConnection();

  if (Configuration->ActualLogProtocol >= 1)
  {
    LogEvent(FORMAT(L"Received %u bytes (%d)", (Length, int(IsStdErr))));
  }

  // Following is taken from scp.c from_backend() and modified

  if (IsStdErr)
  {
    AddStdError(ConvertInput(RawByteString(reinterpret_cast<const char *>(Data), Length)));
  }
  else
  {
    const unsigned char *p = Data;
    unsigned Len = (unsigned)Length;

    // with event-select mechanism we can now receive data even before we
    // actually expect them (OutPtr can be NULL)

    if ((OutPtr != NULL) && (OutLen > 0) && (Len > 0))
    {
      unsigned Used = OutLen;
      if (Used > Len) Used = Len;
      memmove(OutPtr, p, Used);
      OutPtr += Used; OutLen -= Used;
      p += Used; Len -= Used;
    }

    if (Len > 0)
    {
      if (PendSize < PendLen + Len)
      {
        PendSize = PendLen + Len + 4096;
        Pending = (unsigned char *)
          (Pending ? srealloc(Pending, PendSize) : smalloc(PendSize));
        if (!Pending) FatalError(L"Out of memory");
      }
      memmove(Pending + PendLen, p, Len);
      PendLen += Len;
    }

    if (FOnReceive != NULL)
    {
      if (!FFrozen)
      {
        FFrozen = true;
        try
        {
          do
          {
            FDataWhileFrozen = false;
            FOnReceive(NULL);
          }
          while (FDataWhileFrozen);
        }
        __finally
        {
          FFrozen = false;
        }
      }
      else
      {
        FDataWhileFrozen = true;
      }
    }
  }
}
//---------------------------------------------------------------------------
bool __fastcall TSecureShell::Peek(unsigned char *& Buf, int Len)
{
  bool Result = (int(PendLen) >= Len);

  if (Result)
  {
    Buf = Pending;
  }

  return Result;
}
//---------------------------------------------------------------------------
Integer __fastcall TSecureShell::Receive(unsigned char * Buf, Integer Len)
{
  CheckConnection();

  if (Len > 0)
  {
    // Following is taken from scp.c ssh_scp_recv() and modified

    OutPtr = Buf;
    OutLen = Len;

    try
    {
      /*
       * See if the pending-input block contains some of what we
       * need.
       */
      if (PendLen > 0)
      {
        unsigned PendUsed = PendLen;
        if (PendUsed > OutLen)
        {
          PendUsed = OutLen;
        }
        memmove(OutPtr, Pending, PendUsed);
        memmove(Pending, Pending + PendUsed, PendLen - PendUsed);
        OutPtr += PendUsed;
        OutLen -= PendUsed;
        PendLen -= PendUsed;
        if (PendLen == 0)
        {
          PendSize = 0;
          sfree(Pending);
          Pending = NULL;
        }
      }

      while (OutLen > 0)
      {
        if (Configuration->ActualLogProtocol >= 1)
        {
          LogEvent(FORMAT(L"Waiting for another %u bytes", (static_cast<int>(OutLen))));
        }
        WaitForData();
      }

      // This seems ambiguous
      if (Len <= 0) FatalError(LoadStr(LOST_CONNECTION));
    }
    __finally
    {
      OutPtr = NULL;
    }
  }
  if (Configuration->ActualLogProtocol >= 1)
  {
    LogEvent(FORMAT(L"Read %u bytes (%d pending)",
      (static_cast<int>(Len), static_cast<int>(PendLen))));
  }
  return Len;
}
//---------------------------------------------------------------------------
UnicodeString __fastcall TSecureShell::ReceiveLine()
{
  unsigned Index;
  RawByteString Line;
  Boolean EOL = False;

  do
  {
    // If there is any buffer of received chars
    if (PendLen > 0)
    {
      Index = 0;
      // Repeat until we walk thru whole buffer or reach end-of-line
      while ((Index < PendLen) && (!Index || (Pending[Index-1] != '\n')))
      {
        Index++;
      }
      EOL = (Boolean)(Index && (Pending[Index-1] == '\n'));
      Integer PrevLen = Line.Length();
      Line.SetLength(PrevLen + Index);
      Receive(reinterpret_cast<unsigned char *>(Line.c_str()) + PrevLen, Index);
    }

    // If buffer don't contain end-of-line character
    // we read one more which causes receiving new buffer of chars
    if (!EOL)
    {
      unsigned char Ch;
      Receive(&Ch, 1);
      Line += static_cast<char>(Ch);
      EOL = (static_cast<char>(Ch) == '\n');
    }
  }
  while (!EOL);

  // We don't want end-of-line character
  Line.SetLength(Line.Length()-1);

  UnicodeString Result = ConvertInput(Line);
  CaptureOutput(llOutput, Result);

  return Result;
}
//---------------------------------------------------------------------------
UnicodeString __fastcall TSecureShell::ConvertInput(const RawByteString & Input)
{
  UnicodeString Result;
  if (UtfStrings)
  {
    Result = UTF8ToString(Input);
  }
  else
  {
    Result = AnsiToString(Input);
  }
  return Result;
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::SendSpecial(int Code)
{
  LogEvent(FORMAT(L"Sending special code: %d", (Code)));
  CheckConnection();
  FBackend->special(FBackendHandle, (Telnet_Special)Code);
  CheckConnection();
  FLastDataSent = Now();
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::SendEOF()
{
  SendSpecial(TS_EOF);
}
//---------------------------------------------------------------------------
unsigned int __fastcall TSecureShell::TimeoutPrompt(TQueryParamsTimerEvent PoolEvent)
{
  FWaiting++;

  unsigned int Answer;
  try
  {
    TQueryParams Params(qpFatalAbort | qpAllowContinueOnError | qpIgnoreAbort);
    Params.HelpKeyword = HELP_MESSAGE_HOST_IS_NOT_COMMUNICATING;
    Params.Timer = 500;
    Params.TimerEvent = PoolEvent;
    Params.TimerMessage = MainInstructionsFirstParagraph(FMTLOAD(TIMEOUT_STILL_WAITING3, (FSessionData->Timeout)));
    Params.TimerAnswers = qaAbort;
    Params.TimerQueryType = qtInformation;
    if (FConfiguration->SessionReopenAutoStall > 0)
    {
      Params.Timeout = FConfiguration->SessionReopenAutoStall;
      Params.TimeoutAnswer = qaAbort;
    }
    Answer = FUI->QueryUser(MainInstructions(FMTLOAD(CONFIRM_PROLONG_TIMEOUT3, (FSessionData->Timeout))),
      NULL, qaRetry | qaAbort, &Params);
  }
  __finally
  {
    FWaiting--;
  }
  return Answer;
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::SendBuffer(unsigned int & Result)
{
  // for comments see PoolForData
  if (!Active)
  {
    Result = qaRetry;
  }
  else
  {
    try
    {
      if (FBackend->sendbuffer(FBackendHandle) <= MAX_BUFSIZE)
      {
        Result = qaOK;
      }
    }
    catch(...)
    {
      Result = qaRetry;
    }
  }
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::DispatchSendBuffer(int BufSize)
{
  TDateTime Start = Now();
  do
  {
    CheckConnection();
    if (Configuration->ActualLogProtocol >= 1)
    {
      LogEvent(FORMAT(L"There are %u bytes remaining in the send buffer, "
        "need to send at least another %u bytes",
        (BufSize, BufSize - MAX_BUFSIZE)));
    }
    EventSelectLoop(100, false, NULL);
    BufSize = FBackend->sendbuffer(FBackendHandle);
    if (Configuration->ActualLogProtocol >= 1)
    {
      LogEvent(FORMAT(L"There are %u bytes remaining in the send buffer", (BufSize)));
    }

    if (Now() - Start > FSessionData->TimeoutDT)
    {
      LogEvent(L"Waiting for dispatching send buffer timed out, asking user what to do.");
      unsigned int Answer = TimeoutPrompt(SendBuffer);
      switch (Answer)
      {
        case qaRetry:
          Start = Now();
          break;

        case qaOK:
          BufSize = 0;
          break;

        default:
          DebugFail();
          // fallthru

        case qaAbort:
          FatalError(MainInstructions(LoadStr(USER_TERMINATED)));
          break;
      }
    }
  }
  while (BufSize > MAX_BUFSIZE);
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::Send(const unsigned char * Buf, Integer Len)
{
  CheckConnection();
  int BufSize = FBackend->send(FBackendHandle, const_cast<char *>(reinterpret_cast<const char *>(Buf)), Len);
  if (Configuration->ActualLogProtocol >= 1)
  {
    LogEvent(FORMAT(L"Sent %u bytes", (static_cast<int>(Len))));
    LogEvent(FORMAT(L"There are %u bytes remaining in the send buffer", (BufSize)));
  }
  FLastDataSent = Now();
  // among other forces receive of pending data to free the servers's send buffer
  EventSelectLoop(0, false, NULL);

  if (BufSize > MAX_BUFSIZE)
  {
    DispatchSendBuffer(BufSize);
  }
  CheckConnection();
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::SendNull()
{
  LogEvent(L"Sending NULL.");
  unsigned char Null = 0;
  Send(&Null, 1);
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::SendLine(const UnicodeString & Line)
{
  CheckConnection();
  RawByteString Buf;
  if (UtfStrings)
  {
    Buf = RawByteString(UTF8String(Line));
  }
  else
  {
    Buf = RawByteString(AnsiString(Line));
  }
  Buf += "\n";

  FLog->Add(llInput, Line);
  Send(reinterpret_cast<const unsigned char *>(Buf.c_str()), Buf.Length());
}
//---------------------------------------------------------------------------
int __fastcall TSecureShell::TranslatePuttyMessage(
  const TPuttyTranslation * Translation, size_t Count, UnicodeString & Message,
  UnicodeString * HelpKeyword)
{
  int Result = -1;
  for (unsigned int Index = 0; Index < Count; Index++)
  {
    const wchar_t * Original = Translation[Index].Original;
    const wchar_t * Div = wcschr(Original, L'%');
    if (Div == NULL)
    {
      if (wcscmp(Message.c_str(), Original) == 0)
      {
        Message = LoadStr(Translation[Index].Translation);
        Result = int(Index);
        break;
      }
    }
    else
    {
      size_t OriginalLen = wcslen(Original);
      size_t PrefixLen = Div - Original;
      size_t SuffixLen = OriginalLen - PrefixLen - 1;
      if (((size_t)Message.Length() >= OriginalLen - 1) &&
          (wcsncmp(Message.c_str(), Original, PrefixLen) == 0) &&
          (wcsncmp(Message.c_str() + Message.Length() - SuffixLen, Div + 1, SuffixLen) == 0))
      {
        Message = FMTLOAD(Translation[Index].Translation,
          (Message.SubString(PrefixLen + 1, Message.Length() - PrefixLen - SuffixLen).TrimRight()));
        Result = int(Index);
        break;
      }
    }
  }

  if ((HelpKeyword != NULL) && (Result >= 0))
  {
    *HelpKeyword = Translation[Result].HelpKeyword;
  }

  return Result;
}
//---------------------------------------------------------------------------
int __fastcall TSecureShell::TranslateAuthenticationMessage(
  UnicodeString & Message, UnicodeString * HelpKeyword)
{
  static const TPuttyTranslation Translation[] = {
    { L"Using username \"%\".", AUTH_TRANSL_USERNAME },
    { L"Using keyboard-interactive authentication.", AUTH_TRANSL_KEYB_INTER }, // not used anymore
    { L"Authenticating with public key \"%\" from agent", AUTH_TRANSL_PUBLIC_KEY_AGENT },
    { L"Authenticating with public key \"%\"", AUTH_TRANSL_PUBLIC_KEY },
    { L"Authenticated using RSA key \"%\" from agent", AUTH_TRANSL_PUBLIC_KEY_AGENT },
    { L"Wrong passphrase", AUTH_TRANSL_WRONG_PASSPHRASE },
    { L"Wrong passphrase.", AUTH_TRANSL_WRONG_PASSPHRASE },
    { L"Access denied", AUTH_TRANSL_ACCESS_DENIED },
    { L"Trying public key authentication.", AUTH_TRANSL_TRY_PUBLIC_KEY },
    { L"Server refused our public key.", AUTH_TRANSL_KEY_REFUSED, HELP_AUTH_TRANSL_KEY_REFUSED }, // help mapping probably never used
    { L"Server refused our key", AUTH_TRANSL_KEY_REFUSED, HELP_AUTH_TRANSL_KEY_REFUSED }
  };

  int Result = TranslatePuttyMessage(Translation, LENOF(Translation), Message, HelpKeyword);

  if ((Result == 2) || (Result == 3) || (Result == 4))
  {
    FCollectPrivateKeyUsage = true;
  }

  return Result;
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::AddStdError(UnicodeString Str)
{
  FStdError += Str;

  Integer P;
  Str = DeleteChar(Str, L'\r');
  // We send only whole line at once to log, so we have to cache
  // incoming std error data
  FStdErrorTemp += Str;
  UnicodeString Line;
  // Do we have at least one complete line in std error cache?
  while ((P = FStdErrorTemp.Pos(L"\n")) > 0)
  {
    Line = FStdErrorTemp.SubString(1, P-1);
    FStdErrorTemp.Delete(1, P);
    AddStdErrorLine(Line);
  }
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::AddStdErrorLine(const UnicodeString & Str)
{
  if (FAuthenticating)
  {
    FAuthenticationLog += (FAuthenticationLog.IsEmpty() ? L"" : L"\n") + Str;
  }
  CaptureOutput(llStdError, Str);
}
//---------------------------------------------------------------------------
const UnicodeString & __fastcall TSecureShell::GetStdError()
{
  return FStdError;
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::ClearStdError()
{
  // Flush std error cache
  if (!FStdErrorTemp.IsEmpty())
  {
    if (FAuthenticating)
    {
      FAuthenticationLog +=
        (FAuthenticationLog.IsEmpty() ? L"" : L"\n") + FStdErrorTemp;
    }
    CaptureOutput(llStdError, FStdErrorTemp);
    FStdErrorTemp = L"";
  }
  FStdError = L"";
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::CaptureOutput(TLogLineType Type,
  const UnicodeString & Line)
{
  if (FOnCaptureOutput != NULL)
  {
    FOnCaptureOutput(Line, (Type == llStdError) ? cotError : cotOutput);
  }
  FLog->Add(Type, Line);
}
//---------------------------------------------------------------------------
int __fastcall TSecureShell::TranslateErrorMessage(
  UnicodeString & Message, UnicodeString * HelpKeyword)
{
  static const TPuttyTranslation Translation[] = {
    { L"Server unexpectedly closed network connection", UNEXPECTED_CLOSE_ERROR, HELP_UNEXPECTED_CLOSE_ERROR },
    { L"Network error: Connection refused", NET_TRANSL_REFUSED2, HELP_NET_TRANSL_REFUSED },
    { L"Network error: Connection reset by peer", NET_TRANSL_RESET, HELP_NET_TRANSL_RESET },
    { L"Network error: Connection timed out", NET_TRANSL_TIMEOUT2, HELP_NET_TRANSL_TIMEOUT },
    { L"Network error: No route to host", NET_TRANSL_NO_ROUTE2, HELP_NET_TRANSL_NO_ROUTE },
    { L"Network error: Software caused connection abort", NET_TRANSL_CONN_ABORTED, HELP_NET_TRANSL_CONN_ABORTED },
    { L"Host does not exist", NET_TRANSL_HOST_NOT_EXIST2, HELP_NET_TRANSL_HOST_NOT_EXIST },
    { L"Incoming packet was garbled on decryption", NET_TRANSL_PACKET_GARBLED, HELP_NET_TRANSL_PACKET_GARBLED },
  };

  int Index = TranslatePuttyMessage(Translation, LENOF(Translation), Message, HelpKeyword);

  if ((Index == 0) || (Index == 1) || (Index == 2) || (Index == 3))
  {
    FNoConnectionResponse = true;
  }

  Message = ReplaceStr(Message, L"%HOST%", FSessionData->HostNameExpanded);

  return Index;
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::PuttyFatalError(UnicodeString Error)
{
  UnicodeString HelpKeyword;
  TranslateErrorMessage(Error, &HelpKeyword);

  FatalError(Error, HelpKeyword);
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::FatalError(UnicodeString Error, UnicodeString HelpKeyword)
{
  FUI->FatalError(NULL, Error, HelpKeyword);
}
//---------------------------------------------------------------------------
void __fastcall inline TSecureShell::LogEvent(const UnicodeString & Str)
{
  if (FLog->Logging)
  {
    FLog->Add(llMessage, Str);
  }
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::SocketEventSelect(SOCKET Socket, HANDLE Event, bool Startup)
{
  int Events;

  if (Startup)
  {
    Events = (FD_CONNECT | FD_READ | FD_WRITE | FD_OOB | FD_CLOSE | FD_ACCEPT);
  }
  else
  {
    Events = 0;
  }

  if (Configuration->ActualLogProtocol >= 2)
  {
    LogEvent(FORMAT(L"Selecting events %d for socket %d", (int(Events), int(Socket))));
  }

  if (WSAEventSelect(Socket, (WSAEVENT)Event, Events) == SOCKET_ERROR)
  {
    if (Configuration->ActualLogProtocol >= 2)
    {
      LogEvent(FORMAT(L"Error selecting events %d for socket %d", (int(Events), int(Socket))));
    }

    if (Startup)
    {
      FatalError(FMTLOAD(EVENT_SELECT_ERROR, (WSAGetLastError())));
    }
  }
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::UpdateSocket(SOCKET value, bool Startup)
{
  if (!FActive && !Startup)
  {
    // no-op
    // Remove the branch eventually:
    // When TCP connection fails, PuTTY does not release the memory allocated for
    // socket. As a simple hack we call sk_tcp_close() in ssh.c to release the memory,
    // until they fix it better. Unfortunately sk_tcp_close calls do_select,
    // so we must filter that out.
  }
  else
  {
    DebugAssert(value);
    DebugAssert((FActive && (FSocket == value)) || (!FActive && Startup));

    // filter our "local proxy" connection, which have no socket
    if (value != INVALID_SOCKET)
    {
      SocketEventSelect(value, FSocketEvent, Startup);
    }
    else
    {
      DebugAssert(FSessionData->ProxyMethod == pmCmd);
    }

    if (Startup)
    {
      FSocket = value;
      FActive = true;
    }
    else
    {
      FSocket = INVALID_SOCKET;
      Discard();
    }
  }
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::UpdatePortFwdSocket(SOCKET value, bool Startup)
{
  if (Configuration->ActualLogProtocol >= 2)
  {
    LogEvent(FORMAT(L"Updating forwarding socket %d (%d)", (int(value), int(Startup))));
  }

  SocketEventSelect(value, FSocketEvent, Startup);

  if (Startup)
  {
    FPortFwdSockets.insert(value);
  }
  else
  {
    FPortFwdSockets.erase(value);
  }
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::SetActive(bool value)
{
  if (FActive != value)
  {
    if (value)
    {
      Open();
    }
    else
    {
      Close();
    }
  }
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::FreeBackend()
{
  if (FBackendHandle != NULL)
  {
    FBackend->free(FBackendHandle);
    FBackendHandle = NULL;
  }
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::Discard()
{
  bool WasActive = FActive;
  FActive = false;
  FOpened = false;

  if (WasActive)
  {
    FUI->Closed();
  }
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::Close()
{
  LogEvent(L"Closing connection.");
  DebugAssert(FActive);

  // this is particularly necessary when using local proxy command
  // (e.g. plink), otherwise it hangs in sk_localproxy_close
  SendEOF();

  FreeBackend();

  Discard();
}
//---------------------------------------------------------------------------
void inline __fastcall TSecureShell::CheckConnection(int Message)
{
  if (!FActive || get_ssh_state_closed(FBackendHandle))
  {
    UnicodeString Str;
    UnicodeString HelpKeyword;

    if (Message >= 0)
    {
      Str = LoadStr(Message);
    }
    else
    {
      Str = LoadStr(NOT_CONNECTED);
      HelpKeyword = HELP_NOT_CONNECTED;
    }

    Str = MainInstructions(Str);

    int ExitCode = get_ssh_exitcode(FBackendHandle);
    if (ExitCode >= 0)
    {
      Str += L" " + FMTLOAD(SSH_EXITCODE, (ExitCode));
    }
    FatalError(Str, HelpKeyword);
  }
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::PoolForData(WSANETWORKEVENTS & Events, unsigned int & Result)
{
  if (!Active)
  {
    // see comment below
    Result = qaRetry;
  }
  else
  {
    try
    {
      if (Configuration->ActualLogProtocol >= 2)
      {
        LogEvent(L"Pooling for data in case they finally arrives");
      }

      // in extreme condition it may happen that send buffer is full, but there
      // will be no data coming and we may not empty the send buffer because we
      // do not process FD_WRITE until we receive any FD_READ
      if (EventSelectLoop(0, false, &Events))
      {
        LogEvent(L"Data has arrived, closing query to user.");
        Result = qaOK;
      }
    }
    catch(...)
    {
      // if we let the exception out, it may popup another message dialog
      // in whole event loop, another call to PoolForData from original dialog
      // would be invoked, leading to an infinite loop.
      // by retrying we hope (that probably fatal) error would repeat in WaitForData.
      // anyway now once no actual work is done in EventSelectLoop,
      // hardly any exception can occur actually
      Result = qaRetry;
    }
  }
}
//---------------------------------------------------------------------------
class TPoolForDataEvent
{
public:
  __fastcall TPoolForDataEvent(TSecureShell * SecureShell, WSANETWORKEVENTS & Events) :
    FSecureShell(SecureShell),
    FEvents(Events)
  {
  }

  void __fastcall PoolForData(unsigned int & Result)
  {
    FSecureShell->PoolForData(FEvents, Result);
  }

private:
  TSecureShell * FSecureShell;
  WSANETWORKEVENTS & FEvents;
};
//---------------------------------------------------------------------------
void __fastcall TSecureShell::WaitForData()
{
  // see winsftp.c
  bool IncomingData;

  do
  {
    if (Configuration->ActualLogProtocol >= 2)
    {
      LogEvent(L"Looking for incoming data");
    }

    IncomingData = EventSelectLoop(FSessionData->Timeout * MSecsPerSec, true, NULL);
    if (!IncomingData)
    {
      DebugAssert(FWaitingForData == 0);
      TAutoNestingCounter NestingCounter(FWaitingForData);

      WSANETWORKEVENTS Events;
      memset(&Events, 0, sizeof(Events));
      TPoolForDataEvent Event(this, Events);

      LogEvent(L"Waiting for data timed out, asking user what to do.");
      unsigned int Answer = TimeoutPrompt(Event.PoolForData);
      switch (Answer)
      {
        case qaRetry:
          // noop
          break;

        case qaOK:
          // read event was already captured in PoolForData(),
          // make sure we do not try to select it again as it would timeout
          // unless another read event occurs
          IncomingData = true;
          HandleNetworkEvents(FSocket, Events);
          break;

        default:
          DebugFail();
          // fallthru

        case qaAbort:
          FatalError(MainInstructions(LoadStr(USER_TERMINATED)));
          break;
      }
    }
  }
  while (!IncomingData);
}
//---------------------------------------------------------------------------
bool __fastcall TSecureShell::SshFallbackCmd() const
{
  return ssh_fallback_cmd(FBackendHandle);
}
//---------------------------------------------------------------------------
bool __fastcall TSecureShell::EnumNetworkEvents(SOCKET Socket, WSANETWORKEVENTS & Events)
{
  if (Configuration->ActualLogProtocol >= 2)
  {
    LogEvent(FORMAT(L"Enumerating network events for socket %d", (int(Socket))));
  }

  // see winplink.c
  WSANETWORKEVENTS AEvents;
  if (WSAEnumNetworkEvents(Socket, NULL, &AEvents) == 0)
  {
    noise_ultralight(Socket);
    noise_ultralight(AEvents.lNetworkEvents);

    Events.lNetworkEvents |= AEvents.lNetworkEvents;
    for (int Index = 0; Index < FD_MAX_EVENTS; Index++)
    {
      if (AEvents.iErrorCode[Index] != 0)
      {
        Events.iErrorCode[Index] = AEvents.iErrorCode[Index];
      }
    }

    if (Configuration->ActualLogProtocol >= 2)
    {
      LogEvent(FORMAT(L"Enumerated %d network events making %d cumulative events for socket %d",
        (int(AEvents.lNetworkEvents), int(Events.lNetworkEvents), int(Socket))));
    }
  }
  else
  {
    if (Configuration->ActualLogProtocol >= 2)
    {
      LogEvent(FORMAT(L"Error enumerating network events for socket %d", (int(Socket))));
    }
  }

  return
    FLAGSET(Events.lNetworkEvents, FD_READ) ||
    FLAGSET(Events.lNetworkEvents, FD_CLOSE);
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::HandleNetworkEvents(SOCKET Socket, WSANETWORKEVENTS & Events)
{
  static const struct { int Bit, Mask; const wchar_t * Desc; } EventTypes[] =
  {
    { FD_WRITE_BIT, FD_WRITE, L"write" },
    { FD_OOB_BIT, FD_OOB, L"oob" },
    { FD_ACCEPT_BIT, FD_ACCEPT, L"accept" },
    { FD_CONNECT_BIT, FD_CONNECT, L"connect" },
    { FD_CLOSE_BIT, FD_CLOSE, L"close" },
    // Read goes last, as it can cause an exception.
    // Though a correct solution would be to process all events, even if one causes exception
    { FD_READ_BIT, FD_READ, L"read" },
  };

  for (unsigned int Event = 0; Event < LENOF(EventTypes); Event++)
  {
    if (FLAGSET(Events.lNetworkEvents, EventTypes[Event].Mask))
    {
      int Err = Events.iErrorCode[EventTypes[Event].Bit];
      if (Configuration->ActualLogProtocol >= 2)
      {
        LogEvent(FORMAT(L"Handling network %s event on socket %d with error %d",
          (EventTypes[Event].Desc, int(Socket), Err)));
      }
      #pragma option push -w-prc
      LPARAM SelectEvent = WSAMAKESELECTREPLY(EventTypes[Event].Mask, Err);
      #pragma option pop
      select_result((WPARAM)Socket, SelectEvent);
      CheckConnection();
    }
  }
}
//---------------------------------------------------------------------------
bool __fastcall TSecureShell::ProcessNetworkEvents(SOCKET Socket)
{
  WSANETWORKEVENTS Events;
  memset(&Events, 0, sizeof(Events));
  bool Result = EnumNetworkEvents(Socket, Events);
  HandleNetworkEvents(Socket, Events);
  return Result;
}
//---------------------------------------------------------------------------
bool __fastcall TSecureShell::EventSelectLoop(unsigned int MSec, bool ReadEventRequired,
  WSANETWORKEVENTS * Events)
{
  CheckConnection();

  bool Result = false;

  do
  {
    if (Configuration->ActualLogProtocol >= 2)
    {
      LogEvent(L"Looking for network events");
    }
    unsigned int TicksBefore = GetTickCount();
    int HandleCount;
    // note that this returns all handles, not only the session-related handles
    HANDLE * Handles = handle_get_events(&HandleCount);
    try
    {
      Handles = sresize(Handles, HandleCount + 1, HANDLE);
      Handles[HandleCount] = FSocketEvent;
      unsigned int Timeout = MSec;
      if (toplevel_callback_pending())
      {
        Timeout = 0;
      }

      unsigned int WaitResult;
      do
      {
        unsigned int TimeoutStep = std::min(GUIUpdateInterval, Timeout);
        Timeout -= TimeoutStep;
        WaitResult = WaitForMultipleObjects(HandleCount + 1, Handles, FALSE, TimeoutStep);
        FUI->ProcessGUI();
      } while ((WaitResult == WAIT_TIMEOUT) && (Timeout > 0));

      if (WaitResult < WAIT_OBJECT_0 + HandleCount)
      {
        if (handle_got_event(Handles[WaitResult - WAIT_OBJECT_0]))
        {
          Result = true;
        }
      }
      else if (WaitResult == WAIT_OBJECT_0 + HandleCount)
      {
        if (Configuration->ActualLogProtocol >= 1)
        {
          LogEvent(L"Detected network event");
        }

        if (Events == NULL)
        {
          if (ProcessNetworkEvents(FSocket))
          {
            Result = true;
          }
        }
        else
        {
          if (EnumNetworkEvents(FSocket, *Events))
          {
            Result = true;
          }
        }

        {
          TSockets::iterator i = FPortFwdSockets.begin();
          while (i != FPortFwdSockets.end())
          {
            ProcessNetworkEvents(*i);
            i++;
          }
        }
      }
      else if (WaitResult == WAIT_TIMEOUT)
      {
        if (Configuration->ActualLogProtocol >= 2)
        {
          LogEvent(L"Timeout waiting for network events");
        }

        MSec = 0;
      }
      else
      {
        if (Configuration->ActualLogProtocol >= 2)
        {
          LogEvent(FORMAT(L"Unknown waiting result %d", (int(WaitResult))));
        }

        MSec = 0;
      }
    }
    __finally
    {
      sfree(Handles);
    }

    run_toplevel_callbacks();

    unsigned int TicksAfter = GetTickCount();
    // ticks wraps once in 49.7 days
    if (TicksBefore < TicksAfter)
    {
      unsigned int Ticks = TicksAfter - TicksBefore;
      if (Ticks > MSec)
      {
        MSec = 0;
      }
      else
      {
        MSec -= Ticks;
      }
    }

    if ((FSendBuf > 0) && (TicksAfter - FLastSendBufferUpdate >= 1000))
    {
      DWORD BufferLen = 0;
      DWORD OutLen = 0;
      if (WSAIoctl(FSocket, SIO_IDEAL_SEND_BACKLOG_QUERY, NULL, 0, &BufferLen, sizeof(BufferLen), &OutLen, 0, 0) == 0)
      {
        DebugAssert(OutLen == sizeof(BufferLen));
        if (FSendBuf < static_cast<int>(BufferLen))
        {
          LogEvent(FORMAT(L"Increasing send buffer from %d to %d", (FSendBuf, static_cast<int>(BufferLen))));
          FSendBuf = BufferLen;
          setsockopt(FSocket, SOL_SOCKET, SO_SNDBUF, reinterpret_cast<const char *>(&BufferLen), sizeof(BufferLen));
        }
      }
      FLastSendBufferUpdate = TicksAfter;
    }
  }
  while (ReadEventRequired && (MSec > 0) && !Result);

  return Result;
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::Idle(unsigned int MSec)
{
  noise_regular();

  call_ssh_timer(FBackendHandle);

  // if we are actively waiting for data in WaitForData,
  // do not read here, otherwise we swallow read event and never wake
  if (FWaitingForData <= 0)
  {
    EventSelectLoop(MSec, false, NULL);
  }
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::KeepAlive()
{
  if (FActive && (FWaiting == 0))
  {
    LogEvent(L"Sending null packet to keep session alive.");
    SendSpecial(TS_PING);
  }
  else
  {
    // defer next keepalive attempt
    FLastDataSent = Now();
  }
}
//---------------------------------------------------------------------------
unsigned long __fastcall TSecureShell::MaxPacketSize()
{
  if (!FSessionInfoValid)
  {
    UpdateSessionInfo();
  }

  if (FSshVersion == 1)
  {
    return 0;
  }
  else
  {
    if (FMaxPacketSize == NULL)
    {
      FMaxPacketSize = ssh2_remmaxpkt(FBackendHandle);
    }
    return *FMaxPacketSize;
  }
}
//---------------------------------------------------------------------------
UnicodeString __fastcall TSecureShell::FuncToCompression(
  int SshVersion, const void * Compress) const
{
  enum TCompressionType { ctNone, ctZLib };
  if (SshVersion == 1)
  {
    return get_ssh1_compressing(FBackendHandle) ? L"ZLib" : L"";
  }
  else
  {
    return (ssh_compress *)Compress == &ssh_zlib ? L"ZLib" : L"";
  }
}
//---------------------------------------------------------------------------
TCipher __fastcall TSecureShell::FuncToSsh1Cipher(const void * Cipher)
{
  const ssh_cipher *CipherFuncs[] =
    {&ssh_3des, &ssh_des, &ssh_blowfish_ssh1};
  const TCipher TCiphers[] = {cip3DES, cipDES, cipBlowfish};
  DebugAssert(LENOF(CipherFuncs) == LENOF(TCiphers));
  TCipher Result = cipWarn;

  for (unsigned int Index = 0; Index < LENOF(TCiphers); Index++)
  {
    if ((ssh_cipher *)Cipher == CipherFuncs[Index])
    {
      Result = TCiphers[Index];
    }
  }

  DebugAssert(Result != cipWarn);
  return Result;
}
//---------------------------------------------------------------------------
TCipher __fastcall TSecureShell::FuncToSsh2Cipher(const void * Cipher)
{
  const ssh2_ciphers *CipherFuncs[] =
    {&ssh2_3des, &ssh2_des, &ssh2_aes, &ssh2_blowfish, &ssh2_arcfour, &ssh2_ccp};
  const TCipher TCiphers[] = {cip3DES, cipDES, cipAES, cipBlowfish, cipArcfour, cipChaCha20};
  DebugAssert(LENOF(CipherFuncs) == LENOF(TCiphers));
  TCipher Result = cipWarn;

  for (unsigned int C = 0; C < LENOF(TCiphers); C++)
  {
    for (int F = 0; F < CipherFuncs[C]->nciphers; F++)
    {
      if ((ssh2_cipher *)Cipher == CipherFuncs[C]->list[F])
      {
        Result = TCiphers[C];
      }
    }
  }

  DebugAssert(Result != cipWarn);
  return Result;
}
//---------------------------------------------------------------------------
UnicodeString __fastcall TSecureShell::FormatKeyStr(UnicodeString KeyStr)
{
  int Index = 1;
  int Digits = 0;
  while (Index <= KeyStr.Length())
  {
    if (IsHex(KeyStr[Index]))
    {
      Digits++;
      if (Digits >= 16)
      {
        KeyStr.Insert(L" ", Index + 1);
        Index++;
        Digits = 0;
      }
    }
    else
    {
      Digits = 0;
    }
    Index++;
  }
  return KeyStr;
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::GetRealHost(UnicodeString & Host, int & Port)
{
  if (FSessionData->Tunnel)
  {
    // Now that we set the CONF_loghost, the hostname is correct already
    Host = FSessionData->OrigHostName;
    Port = FSessionData->OrigPortNumber;
  }
}
//---------------------------------------------------------------------------
UnicodeString __fastcall TSecureShell::RetrieveHostKey(UnicodeString Host, int Port, const UnicodeString KeyType)
{
  AnsiString AnsiStoredKeys;
  AnsiStoredKeys.SetLength(10240);
  UnicodeString Result;
  if (retrieve_host_key(AnsiString(Host).c_str(), Port, AnsiString(KeyType).c_str(),
        AnsiStoredKeys.c_str(), AnsiStoredKeys.Length()) == 0)
  {
    PackStr(AnsiStoredKeys);
    Result = UnicodeString(AnsiStoredKeys);
  }
  return Result;
}
//---------------------------------------------------------------------------
struct TPasteKeyHandler
{
  UnicodeString KeyStr;
  UnicodeString NormalizedFingerprintMD5;
  UnicodeString NormalizedFingerprintSHA256;
  TSessionUI * UI;

  void __fastcall Paste(TObject * Sender, unsigned int & Answer);
};
//---------------------------------------------------------------------------
void __fastcall TPasteKeyHandler::Paste(TObject * /*Sender*/, unsigned int & Answer)
{
  UnicodeString ClipboardText;
  if (TextFromClipboard(ClipboardText, true))
  {
    UnicodeString NormalizedClipboardFingerprint = NormalizeFingerprint(ClipboardText);
    // case insensitive comparison, contrary to VerifyHostKey (we should change to insesitive there too)
    if (SameText(NormalizedClipboardFingerprint, NormalizedFingerprintMD5) ||
        SameText(NormalizedClipboardFingerprint, NormalizedFingerprintSHA256) ||
        SameText(ClipboardText, KeyStr))
    {
      Answer = qaYes;
    }
    else
    {
      const struct ssh_signkey * Algorithm;
      try
      {
        UnicodeString Key = ParseOpenSshPubLine(ClipboardText, Algorithm);
        if (Key == KeyStr)
        {
          Answer = qaYes;
        }
      }
      catch (...)
      {
        // swallow
      }
    }
  }

  if (Answer == 0)
  {
    UI->QueryUser(LoadStr(HOSTKEY_NOT_MATCH_CLIPBOARD), NULL, qaOK, NULL, qtError);
  }
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::VerifyHostKey(
  const UnicodeString & AHost, int Port, const UnicodeString & KeyType, const UnicodeString & KeyStr,
  const UnicodeString & Fingerprint)
{
  if (Configuration->ActualLogProtocol >= 1)
  {
    LogEvent(FORMAT(L"Verifying host key %s %s with fingerprints %s", (KeyType, FormatKeyStr(KeyStr), Fingerprint)));
  }

  GotHostKey();

  DebugAssert(KeyStr.Pos(HostKeyDelimiter) == 0);

  UnicodeString Host = AHost;
  GetRealHost(Host, Port);

  UnicodeString Buf = Fingerprint;
  UnicodeString SignKeyAlg = CutToChar(Buf, L' ', false);
  UnicodeString SignKeySize = CutToChar(Buf, L' ', false);
  UnicodeString SignKeyType = SignKeyAlg + L' ' + SignKeySize;
  UnicodeString MD5 = CutToChar(Buf, L' ', false);
  UnicodeString FingerprintMD5 = SignKeyType + L' ' + MD5;
  UnicodeString SHA256 = Buf;
  UnicodeString FingerprintSHA256 = SignKeyType + L' ' + SHA256;
  UnicodeString NormalizedFingerprintMD5 = NormalizeFingerprint(FingerprintMD5);
  UnicodeString NormalizedFingerprintSHA256 = NormalizeFingerprint(FingerprintSHA256);

  FSessionInfo.HostKeyFingerprint = FingerprintSHA256;

  if (FSessionData->FingerprintScan)
  {
    Abort();
  }

  bool Result = false;

  UnicodeString StoredKeys = RetrieveHostKey(Host, Port, KeyType);
  Buf = StoredKeys;
  while (!Result && !Buf.IsEmpty())
  {
    UnicodeString StoredKey = CutToChar(Buf, HostKeyDelimiter, false);
    // skip leading ECDH subtype identification
    int P = StoredKey.Pos(L",");
    // start from beginning or after the comma, if there's any
    bool Fingerprint = (StoredKey.SubString(P + 1, 2) != L"0x");
    // it's probably a fingerprint (stored by TSessionData::CacheHostKey)
    UnicodeString NormalizedExpectedKey;
    if (Fingerprint)
    {
      NormalizedExpectedKey = NormalizeFingerprint(StoredKey);
    }
    if ((!Fingerprint && (StoredKey == KeyStr)) ||
        (Fingerprint && ((NormalizedExpectedKey == NormalizedFingerprintMD5) || (NormalizedExpectedKey == NormalizedFingerprintSHA256))))
    {
      LogEvent(L"Host key matches cached key");
      Result = true;
    }
    else
    {
      if (Configuration->ActualLogProtocol >= 1)
      {
        UnicodeString FormattedKey = Fingerprint ? StoredKey : FormatKeyStr(StoredKey);
        LogEvent(FORMAT(L"Host key does not match cached key %s", (FormattedKey)));
      }
      else
      {
        LogEvent(L"Host key does not match cached key");
      }
    }
  }

  bool ConfiguredKeyNotMatch = false;

  if (!Result && !FSessionData->HostKey.IsEmpty() &&
      (StoredKeys.IsEmpty() || FSessionData->OverrideCachedHostKey))
  {
    UnicodeString Buf = FSessionData->HostKey;
    while (!Result && !Buf.IsEmpty())
    {
      UnicodeString ExpectedKey = CutToChar(Buf, HostKeyDelimiter, false);
      UnicodeString NormalizedExpectedKey = NormalizeFingerprint(ExpectedKey);
      if (ExpectedKey == L"*")
      {
        UnicodeString Message = LoadStr(ANY_HOSTKEY);
        FUI->Information(Message, true);
        FLog->Add(llException, Message);
        Result = true;
      }
      else if ((NormalizedExpectedKey == NormalizedFingerprintMD5) || (NormalizedExpectedKey == NormalizedFingerprintSHA256))
      {
        LogEvent(L"Host key matches configured key");
        Result = true;
      }
      else
      {
        LogEvent(FORMAT(L"Host key does not match configured key %s", (ExpectedKey)));
      }
    }

    if (!Result)
    {
      ConfiguredKeyNotMatch = true;
    }
  }

  if (!Result)
  {
    bool Verified;
    if (ConfiguredKeyNotMatch || Configuration->DisableAcceptingHostKeys)
    {
      Verified = false;
    }
    // no point offering manual verification, if we cannot persist the verified key
    else if (!Configuration->Persistent && Configuration->Scripting)
    {
      Verified = false;
    }
    else
    {
      // We should not offer caching if !Configuration->Persistent,
      // but as scripting mode is handled earlier and in GUI it hardly happens,
      // it's a small issue.
      TClipboardHandler ClipboardHandler;
      ClipboardHandler.Text = FingerprintSHA256 + L"\n" + FingerprintMD5;
      TPasteKeyHandler PasteKeyHandler;
      PasteKeyHandler.KeyStr = KeyStr;
      PasteKeyHandler.NormalizedFingerprintMD5 = NormalizedFingerprintMD5;
      PasteKeyHandler.NormalizedFingerprintSHA256 = NormalizedFingerprintSHA256;
      PasteKeyHandler.UI = FUI;

      bool Unknown = StoredKeys.IsEmpty();

      int Answers;
      int AliasesCount;
      TQueryButtonAlias Aliases[4];
      Aliases[0].Button = qaRetry;
      Aliases[0].Alias = LoadStr(COPY_KEY_BUTTON);
      Aliases[0].OnSubmit = &ClipboardHandler.Copy;
      Aliases[1].Button = qaIgnore;
      Aliases[1].Alias = LoadStr(PASTE_KEY_BUTTON);
      Aliases[1].OnSubmit = &PasteKeyHandler.Paste;
      Aliases[1].GroupWith = qaYes;
      Answers = qaYes | qaCancel | qaRetry | qaIgnore;
      AliasesCount = 2;
      if (!Unknown)
      {
        Aliases[2].Button = qaYes;
        Aliases[2].Alias = LoadStr(UPDATE_KEY_BUTTON);
        Aliases[3].Button = qaOK;
        Aliases[3].Alias = LoadStr(ADD_KEY_BUTTON);
        AliasesCount += 2;
        Answers |= qaSkip | qaOK;
      }
      else
      {
        Answers |= qaNo;
      }

      TQueryParams Params(qpWaitInBatch);
      Params.NoBatchAnswers = qaYes | qaRetry | qaSkip | qaOK;
      Params.HelpKeyword = (Unknown ? HELP_UNKNOWN_KEY : HELP_DIFFERENT_KEY);
      Params.Aliases = Aliases;
      Params.AliasesCount = AliasesCount;

      UnicodeString KeyTypeHuman = GetKeyTypeHuman(KeyType);
      UnicodeString KeyDetails = FMTLOAD(KEY_DETAILS, (SignKeyType, SHA256, MD5));
      UnicodeString Message = FMTLOAD((Unknown ? UNKNOWN_KEY4 : DIFFERENT_KEY5), (KeyTypeHuman, KeyDetails));
      if (Configuration->Scripting)
      {
        AddToList(Message, LoadStr(SCRIPTING_USE_HOSTKEY), L"\n");
      }

      unsigned int R =
        FUI->QueryUser(Message, NULL, Answers, &Params, qtWarning);
      UnicodeString StoreKeyStr = KeyStr;

      switch (R) {
        case qaOK:
          DebugAssert(!Unknown);
          StoreKeyStr = (StoredKeys + HostKeyDelimiter + StoreKeyStr);
          // fall thru
        case qaYes:
          store_host_key(AnsiString(Host).c_str(), Port, AnsiString(KeyType).c_str(), AnsiString(StoreKeyStr).c_str());
          Verified = true;
          break;

        case qaCancel:
          Verified = false;
          break;

        default:
          Verified = true;
          break;
      }
    }

    if (!Verified)
    {
      Configuration->Usage->Inc(L"HostNotVerified");

      UnicodeString Message;
      if (ConfiguredKeyNotMatch)
      {
        Message = FMTLOAD(CONFIGURED_KEY_NOT_MATCH, (FSessionData->HostKey));
      }
      else if (!Configuration->Persistent && Configuration->Scripting)
      {
        Message = LoadStr(HOSTKEY_NOT_CONFIGURED);
      }
      else
      {
        Message = LoadStr(KEY_NOT_VERIFIED);
      }

      Exception * E = new Exception(MainInstructions(Message));
      try
      {
        FUI->FatalError(E, FMTLOAD(HOSTKEY, (FingerprintSHA256)));
      }
      __finally
      {
        delete E;
      }
    }
  }

  Configuration->RememberLastFingerprint(FSessionData->SiteKey, SshFingerprintType, FingerprintSHA256);
}
//---------------------------------------------------------------------------
bool __fastcall TSecureShell::HaveHostKey(UnicodeString Host, int Port, const UnicodeString KeyType)
{
  // Return true, if we have any host key fingerprint of a particular type

  GetRealHost(Host, Port);

  UnicodeString StoredKeys = RetrieveHostKey(Host, Port, KeyType);
  bool Result = !StoredKeys.IsEmpty();

  if (!FSessionData->HostKey.IsEmpty())
  {
    UnicodeString Buf = FSessionData->HostKey;
    while (!Result && !Buf.IsEmpty())
    {
      UnicodeString ExpectedKey = CutToChar(Buf, HostKeyDelimiter, false);
      UnicodeString ExpectedKeyType = KeyTypeFromFingerprint(ExpectedKey);
      Result = SameText(ExpectedKeyType, KeyType);
    }
  }

  if (Result)
  {
    LogEvent(FORMAT(L"Have a known host key of type %s", (KeyType)));
  }

  return Result;
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::AskAlg(UnicodeString AlgType, UnicodeString AlgName)
{
  // beware of changing order
  static const TPuttyTranslation AlgTranslation[] = {
    { L"cipher", CIPHER_TYPE_BOTH2 },
    { L"client-to-server cipher", CIPHER_TYPE_CS2 },
    { L"server-to-client cipher", CIPHER_TYPE_SC2 },
    { L"key-exchange algorithm", KEY_EXCHANGE_ALG },
    { L"hostkey type", KEYKEY_TYPE },
  };

  TranslatePuttyMessage(AlgTranslation, LENOF(AlgTranslation), AlgType);

  UnicodeString Msg = FMTLOAD(ALG_BELOW_TRESHOLD, (AlgType, AlgName));

  if (FUI->QueryUser(Msg, NULL, qaYes | qaNo, NULL, qtWarning) == qaNo)
  {
    UnicodeString Error = FMTLOAD(ALG_NOT_VERIFIED, (AlgType, AlgName));
    FUI->FatalError(NULL, Error);
  }
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::DisplayBanner(const UnicodeString & Banner)
{
  FUI->DisplayBanner(Banner);
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::OldKeyfileWarning()
{
  // actually never called, see Net.cpp
  FUI->QueryUser(LoadStr(OLD_KEY), NULL, qaOK, NULL, qtWarning);
}
//---------------------------------------------------------------------------
bool __fastcall TSecureShell::GetStoredCredentialsTried()
{
  return FStoredPasswordTried || FStoredPasswordTriedForKI || FStoredPassphraseTried;
}
//---------------------------------------------------------------------------
bool __fastcall TSecureShell::GetReady()
{
  return FOpened && (FWaiting == 0);
}
//---------------------------------------------------------------------------
void __fastcall TSecureShell::CollectUsage()
{
  if (FCollectPrivateKeyUsage)
  {
    Configuration->Usage->Inc(L"OpenedSessionsPrivateKey2");
  }

  if (FSshVersion == 1)
  {
    Configuration->Usage->Inc(L"OpenedSessionsSSH1");
  }
  else if (FSshVersion == 2)
  {
    Configuration->Usage->Inc(L"OpenedSessionsSSH2");
  }

  if (SshImplementation == sshiOpenSSH)
  {
    Configuration->Usage->Inc(L"OpenedSessionsSSHOpenSSH");
  }
  else if (SshImplementation == sshiProFTPD)
  {
    Configuration->Usage->Inc(L"OpenedSessionsSSHProFTPD");
  }
  else if (SshImplementation == sshiBitvise)
  {
    Configuration->Usage->Inc(L"OpenedSessionsSSHBitvise");
  }
  else if (SshImplementation == sshiTitan)
  {
    Configuration->Usage->Inc(L"OpenedSessionsSSHTitan");
  }
  else if (SshImplementation == sshiOpenVMS)
  {
    Configuration->Usage->Inc(L"OpenedSessionsSSHOpenVMS");
  }
  else if (ContainsText(FSessionInfo.SshImplementation, L"Serv-U"))
  {
    Configuration->Usage->Inc(L"OpenedSessionsSSHServU");
  }
  else if (SshImplementation == sshiCerberus)
  {
    // Ntb, Cerberus can also be detected using vendor-id extension
    // Cerberus FTP Server 7.0.5.3 (70005003) by Cerberus, LLC
    Configuration->Usage->Inc(L"OpenedSessionsSSHCerberus");
  }
  else if (ContainsText(FSessionInfo.SshImplementation, L"WS_FTP"))
  {
    Configuration->Usage->Inc(L"OpenedSessionsSSHWSFTP");
  }
  // SSH-2.0-1.36_sshlib GlobalSCAPE
  else if (ContainsText(FSessionInfo.SshImplementation, L"GlobalSCAPE"))
  {
    Configuration->Usage->Inc(L"OpenedSessionsSSHGlobalScape");
  }
  // SSH-2.0-CompleteFTP-8.1.3
  else if (ContainsText(FSessionInfo.SshImplementation, L"CompleteFTP"))
  {
    Configuration->Usage->Inc(L"OpenedSessionsSSHComplete");
  }
  // SSH-2.0-CoreFTP-0.3.3
  else if (ContainsText(FSessionInfo.SshImplementation, L"CoreFTP"))
  {
    Configuration->Usage->Inc(L"OpenedSessionsSSHCore");
  }
  // SSH-2.0-SSHD-CORE-0.11.0 (value is configurable, this is a default)
  // (Apache Mina SSHD, e.g. on brickftp.com)
  else if (ContainsText(FSessionInfo.SshImplementation, L"SSHD-CORE"))
  {
    Configuration->Usage->Inc(L"OpenedSessionsSSHApache");
  }
  // SSH-2.0-Syncplify_Me_Server
  else if (ContainsText(FSessionInfo.SshImplementation, L"Syncplify"))
  {
    Configuration->Usage->Inc(L"OpenedSessionsSSHSyncplify");
  }
  else if (ContainsText(FSessionInfo.SshImplementation, L"zFTPServer"))
  {
    Configuration->Usage->Inc(L"OpenedSessionsSSHzFTP");
  }
  else
  {
    Configuration->Usage->Inc(L"OpenedSessionsSSHOther");
  }
}
//---------------------------------------------------------------------------
bool __fastcall TSecureShell::CanChangePassword()
{
  return
    // These major SSH servers explicitly do not support password change.
    (SshImplementation != sshiOpenSSH) && // See userauth_passwd
    (SshImplementation != sshiProFTPD); // See sftp_auth_password
}