[aescrypt] PATCH: Detect that some destination files (plain or .aes) cannot be written prior to collecting password.

[Kaz Kylheku]

Patch for detecting that destination files cannot be written prior to 
asking for password.

If any file exists, and can be opened for reading, then a simple message 
is issued for that file and the operation is canceled, e.g:

    Output file C:\foo.txt exists already

If a file exists, but cannot be opened for reading then the reason is 
added to the error message. For example:

    Output file C:\foo.txt exists already:
    Access is denied.



diff -urp AESCrypt_source_v309-ORIG/AESCrypt/AESCryptWorkerThreads.cpp 
AESCrypt_source_v309/AESCrypt/AESCryptWorkerThreads.cpp
--- 
AESCrypt_source_v309-ORIG/AESCrypt/AESCryptWorkerThreads.cpp	2013-03-09 
23:13:54.000000000 -0800
+++ AESCrypt_source_v309/AESCrypt/AESCryptWorkerThreads.cpp	2013-09-06 
02:16:14.849193800 -0700
@@ -104,23 +104,17 @@ void AESCryptWorkerThreads::ProcessFiles
  {
      PasswdDialog dlg;

-    // Prompt the user for a password
-    if (dlg.DoModal(::GetActiveWindow(), (encrypt ? 1 : 0)) == IDOK)
-    {
-        if (StartThread(file_list,
-                        dlg.passwd,
-                        encrypt) == false)
-        {
-            // We were unable to start a thread, so we must clean up
-            // the file list.
-            delete file_list;
-        }
-    }
-    else
-    {
-        // The user canceled the operation, so delete the file list
-        delete file_list;
-    }
+	if (CheckOverwriteFiles(file_list, encrypt) && // files are not in the 
way
+		dlg.DoModal(::GetActiveWindow(), (encrypt ? 1 : 0)) == IDOK && // 
prompt for password
+		StartThread(file_list, dlg.passwd, encrypt)) // start thread
+	{
+		// Thread started successfully and now owns file_list
+		return;
+	}
+
+	// The operation did not proceed so ownership of the file
+	// list did not pass to the thread; we must delete it.
+	delete file_list;
  }

  /*
@@ -283,6 +277,32 @@ DWORD WINAPI ThreadInit(LPVOID lpParamet
  }

  /*
+ * CheckOverwriteFiles
+ *
+ * Returns false if any of the destination files of the given
+ * file list already exist or cannot be used.
+ */
+bool AESCryptWorkerThreads::CheckOverwriteFiles(
+	                              StringList *file_list,
+			                      bool encrypt)
+{
+	for (StringListIter i = file_list->begin(); i != file_list->end(); 
i++) {
+		const String &name = *i;
+		String dest = encrypt ? name + _T(".aes") : name.substr(0, 
name.length() - 4);
+		BufferedFile check_file;
+		DWORD result_code = check_file.OpenFile(dest.c_str(), false, 
OPEN_EXISTING);
+
+		if (result_code != ERROR_FILE_NOT_FOUND) {
+            ::ReportError(  _T("Output file ") + dest + _T(" exists 
already"),
+                            result_code);
+			return false;
+		}
+	}
+
+	return true;
+}
+
+/*
   * EncryptFiles
   *
   * This function is called by the worker thread to encrypt a list of 
files.
diff -urp AESCrypt_source_v309-ORIG/AESCrypt/AESCryptWorkerThreads.h 
AESCrypt_source_v309/AESCrypt/AESCryptWorkerThreads.h
--- 
AESCrypt_source_v309-ORIG/AESCrypt/AESCryptWorkerThreads.h	2013-03-09 
23:13:54.000000000 -0800
+++ AESCrypt_source_v309/AESCrypt/AESCryptWorkerThreads.h	2013-09-06 
01:43:02.101147000 -0700
@@ -27,6 +27,9 @@ class AESCryptWorkerThreads

          inline void DoMessageLoop();

+		bool CheckOverwriteFiles( StringList *file_list,
+			                      bool encrypt);
+
          void EncryptFiles(  StringList *file_list,
  							TCHAR *passwd);

diff -urp AESCrypt_source_v309-ORIG/AESCrypt/stdafx.h 
AESCrypt_source_v309/AESCrypt/stdafx.h
--- AESCrypt_source_v309-ORIG/AESCrypt/stdafx.h	2013-03-09 
23:13:54.000000000 -0800
+++ AESCrypt_source_v309/AESCrypt/stdafx.h	2013-09-06 01:26:21.891136400 
-0700
@@ -41,7 +41,9 @@

  // STL
  #include <list>
-typedef std::list< std::basic_string<TCHAR> > StringList;
+typedef std::basic_string<TCHAR> String;
+typedef std::list< String > StringList;
+typedef std::list< String >::iterator StringListIter;

  // Win32
  #include <commctrl.h>