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Topic created on: August 10, 2007 00:41 CDT by jaffersathik2010 .

Hi All,

Right now I am trying to analyze a application called 'share' (a p2p application).

IDA successfully disassemble the 'share' application , but when I run the application inside the debugger, it throws exceptions. I enabled stealth plugin properly but still it fails.

What should I do to run the application inside the debugger successfully ? Have anybody tried the same?

Thanks in advance.

--Jaffer

igorsk		August 10, 2007 02:54.46 CDT
Which exeptions does it throw? Did you try passing them to the application? Share is written in Delphi, and I think Delphi uses some exceptions for internal purposes.

jms		August 11, 2007 01:42.51 CDT
Yeah and most programs (try anything commercial) throw unwarranted exceptions, your debugger might just be catching them. Write an ollyscript to get past all of them if it's getting annoying, now if it is throwing exceptions and then the program is dying, they may have some anti-debugging in their code.

jaffersathik2010		August 12, 2007 23:43.19 CDT
Hi igorsk and jms, Thank you very much for your ideas. I tried passing exceptions to the applications and finally managed to run the application from the debugger. But now facing another problem. I was trying to put a breakpoint at the 'recv()' function but could not see any instrution calling the 'recv' function (windows dll function) at all. I only got the follwing instructions: Jmp ds:recv /JMP can't be used to call a function / Note: Earlier I had worked on 'winny application' where I got the instruction 'Call recv' - which calls the recv fucntion, but in 'share' i cound not able to see the such instuctions. I welcome any kind of suggessions. Thanks, Jaffer

anonymouse		August 13, 2007 10:58.43 CDT
> jaffersathik2010: Hi igorsk and jms, > > Jmp ds:recv /JMP can\'t be used to call a function / who said so ? check any importtable api calls they are all jumps why jump cant call ? try assembling this in a sample project and see if the call works or not `00409AA0 6A 00 PUSH 0 00409AA2 68 70A14000 PUSH 0040A170 00409AA7 68 70A24000 PUSH 0040A270 00409AAC 6A 00 PUSH 0 00409AAE 68 979A4000 PUSH 00409A97 00409AB3 - E9 BEC99577 JMP USER32.MessageBoxA` user proper address viz dont copy paste 409a97 but do push offset Caption where Caption is defined a Caption db "an experiment trying to jump over hoops",13,10 [/code]

jaffersathik2010		August 14, 2007 00:11.14 CDT
Hi, Till today I dont know JMP can be used to call a function!! Thanks a lot . Thanks, Jaffer.

fileoffset		August 15, 2007 01:39.09 CDT
The reason it is possible to JMP to an API call correctly, is because many compilers build an API "Jump Table". This Jump Table is used as a trampoline to call API. The reason it works is because the location of the JMP is CALLed at the original address, thus pushing the correct return address on the stack, e.g: 0: push 0 1: push "blah" 2: push "blah" 3: push 0 4: call 100 <- the call pushes the correct return address 5: xor eax, eax on the stack, i.e 5 6: ret 100: jmp MessageBoxA <- the jmp only redirects to the correct API and so is transparent

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