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My friend was typing a long message in IE to one of his old schoolmates that he had just found on Internet. He spent about an hour writing and rewriting and when finally hit the Send button he got a page saying that connection was probably lost. Going back in URL history brought the empty edit box and all data was lost. Or was it? He called me and I immediately advised him to save a crash dump of iexplore.exe using Task Manager (Vista). I also asked him for a word he used to start his message. It was “Hello” in Russian. I got his dump file and opened it in WinDbg. Because the language of his message was Russian I assumed that it was still there in local buffers or heap entries in UNICODE format so I typed “ello” in Notepad and saved this in a Unicode text file. Loading it in a binary editor (I used Visual C++) showed the following sequence of bytes:
40 04 38 04 32 04 35 04 42 04
Then I did a search in WinDbg for this sequence from the first loaded module address till the end of user space:
0:000> lm
start end module name
003c0000 0045b000 iexplore
[...]
0:000> s 003c0000 L?7FFFFFFF 40 04 38 04 32 04 35 04 42 04
[...]
048971e4 40 04 38 04 32 04 35 04-42 04 2c 00 20 00 1c 04 @.8.2.5.B.,. ...
[...]
08530fe4 40 04 38 04 32 04 35 04-42 04 2c 00 20 00 1c 04 @.8.2.5.B.,. ...
[...]
201ea65c 40 04 38 04 32 04 35 04-42 04 2c 00 20 00 1c 04 @.8.2.5.B.,. ...
[...]
The number of found entries was big and I decided to output every entry into a file using the following script:
.foreach ( address { s-[1]b 003c0000 L?7FFFFFFF 40 04 38 04 32 04 35 04 42 04 }) {.writemem c:\dmitry\ieout${address}.txt ${address}-10 ${address}+1000}
I got numerous files:
C:\dmitry>dir ieout*.txt
[...]
09/06/2008 08:53 4112 ieout0x048971e4.txt
09/06/2008 08:53 4112 ieout0x0489784c.txt
09/06/2008 08:53 4112 ieout0x0489b854.txt
09/06/2008 08:53 4112 ieout0x0489bc5c.txt
[...]
I combined all of them into one big file and sent it to my friend:
C:\dmitry>type ieout0x*.txt >ieoutall.txt
The file contained not only the final message but all intermediate typing histories too. He was very happy.
- Dmitry Vostokov @ DumpAnalysis.org -
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June 10th, 2008 at 9:56 am
Great read. This is an innovative and unique way to put the debugger to good use.
June 10th, 2008 at 12:35 pm
Thanks! This was indeed my first use of WinDbg in data recovery. I tried strings.exe from sysinternals on a dump file but it didn’t pull out correct Unicode data. Perhaps that tool works well only with English Unicode.
June 11th, 2008 at 2:14 am
why you not use
{s -u 003c0000 L?7FFFFFFF “ello” }
?
June 11th, 2008 at 7:40 am
Because it was not “ello” but its Russian equivalent. It uses different charset. For example, du on addresses containing Russian Unicode strings doesn’t show Russian characters in command output window.