Batch symmetric ciphering?

Paolo Casagranda
Fri, 12 Jan 2001 08:46:31 +0100

Thank you VERY MUCH for your suggestions. I succeeded in automating
symmetric ciphering under Windows NT (I've heard that under W2000 it's the
I send the lines of code I used, maybe they could be useful to someone.

Automating gpg through pipe WinNT:

 BOOL fSuccess;
 HANDLE hChildStdinRd, hChildStdinWr;
 HANDLE hSaveStdin, hChildStdinWrDup;
 DWORD dwProcessId;

 // Set the bInheritHandle flag so pipe handles are inherited.
 saAttr.nLength = sizeof(SECURITY_ATTRIBUTES);
 saAttr.bInheritHandle = TRUE;
 saAttr.lpSecurityDescriptor = NULL;

 // The steps for redirecting child process's STDIN:
 // 1. Save current STDIN, to be restored later.
 // 2. Create anonymous pipe to be STDIN for child process.
 // 3. Set STDIN of the parent to be the read handle to the
 // pipe, so it is inherited by the child process.
 // 4. Create a noninheritable duplicate of the write handle,
 // and close the inheritable write handle.

 // Save the handle to the current STDIN.
 hSaveStdin = GetStdHandle(STD_INPUT_HANDLE);

 // Create a pipe for the child process's STDIN.
 if( !CreatePipe(&hChildStdinRd, &hChildStdinWr, &saAttr, 0) )
  TRACE0( _T("Stdin pipe creation failed\n") );
  return FALSE;
 // Set a read handle to the pipe to be STDIN.
 if( !SetStdHandle(STD_INPUT_HANDLE, hChildStdinRd) )
  TRACE0( _T("Redirecting Stdin failed\n") );
  return FALSE;
 // Duplicate the write handle to the pipe so it is not inherited.
 fSuccess = DuplicateHandle(GetCurrentProcess(), hChildStdinWr,
 GetCurrentProcess(), &hChildStdinWrDup,
 0, FALSE, // not inherited
 if( !fSuccess )
  TRACE0( _T("DuplicateHandle failed\n") );
  return FALSE;

 // Now create the child process.

 // Set up members of STARTUPINFO structure.
 ZeroMemory( &siStartInfo, sizeof(STARTUPINFO) );
 siStartInfo.cb = sizeof(STARTUPINFO);
 siStartInfo.dwFlags = STARTF_USESTDHANDLES;
 siStartInfo.hStdInput = hChildStdinRd;

 // Create the child process.
 BOOL ret = CreateProcess( NULL,
 "d:\\exe\\gpg.exe --yes --batch --passphrase-fd 0 --output
d:\\prove\\encrypted.cfr --symmetric d:\\prove\\d24_final.doc", //
applicatin name
 NULL, // process security attributes
 NULL, // primary thread security attributes
 TRUE, // handles are inherited
 DETACHED_PROCESS, // creation flags
 NULL, // use parent's environment
 NULL, // use parent's current directory
 &siStartInfo, // STARTUPINFO pointer
 &piProcInfo); // receives PROCESS_INFORMATION
 if( ret )
 dwProcessId = piProcInfo.dwProcessId;
 HANDLE hProcessHandle = piProcInfo.hProcess;

 // After process creation, restore the saved STDIN and STDOUT.
 if( !SetStdHandle(STD_INPUT_HANDLE, hSaveStdin) )
  TRACE0( _T("Re-redirecting Stdin failed\n") );
  return FALSE;
 // After process creation, restore the saved STDIN and STDOUT.
 if( !SetStdHandle(STD_INPUT_HANDLE, hSaveStdin) )
  TRACE0( _T("Re-redirecting Stdin failed\n") );
  return FALSE;

 // Passphrase...
 char *lpBuffer = "zuzzurro\n";
 DWORD dwwt;

 BOOL b =WriteFile(
   hChildStdinWrDup,                    // handle to file
   lpBuffer,                // data buffer
   9,     // number of bytes to write
   &dwwt,  // number of bytes written

 if(b) MessageBox("OK");
  DWORD dwErr = GetLastError();
  CString str;
  str.Format("Error %lu", dwErr);

 ::WaitForSingleObject(hProcessHandle, INFINITE); // Wait for process to end

----- Original Message -----
From: "Werner Koch" <>
To: "Paolo Casagranda" <>
Cc: <>
Sent: giovedý 11 gennaio 2001 9.54
Subject: Re: Batch symmetric ciphering?

> On Thu, 11 Jan 2001, Paolo Casagranda wrote:
> > I re-post my question (second and last time, I promise).
> > My question is: How can I cipher with SYMMETRIC keys in batch mode? (To
> > automate the task, under MS Windows)
> You have to use --passphrase-fd n and pipe the passphrase to file
> descriptor n. The default command shell of Windows 95 does not
> allow to do this. IIRC, it is possible under NT.
> TYou may want to write a small wrapper program. Have a look at the
> API: CreateProcess and CreatePipe
> Werner
> --
> Werner Koch <>
> GNU Privacy Guard (
> Free Software Foundation Europe (
> [Please see X-* mail header for OpenPGP key info]
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