So if we analyze the address of bp-110H will see something interesting. Let’s look close char v50 // is located in bp-110h. There we have the variable v50, which is a char, that means there is the key for validation. The technique for producing the offline key is formed with the data that the user enters, and this function compares the serial key. The function is translated in pseudocode. To translate ASM into pseudocode and view the code, press F5. Go to IDA and copy the EIP address 0x00364800. He tried to explain what was wrong with this program there. The essential register, EIP, is where we need to concentrate right now. Look at the EAX register in 圆4dgb, if it has AAAA overwritten, the memory has been overwritten with my character. To produce 2000 A characters, I wrote an easy Python program.įilename = " crack.txt " junk = " \x41 " * 2000 buffer = junk textfile = open ( filename, ' w ' ) textfile. Sending 0x41 (A) into the Licensed E-mail and Registration Code fields will cause a buffer exceed, which is what we need. It’s now our turn to identify software with poor coding. Start address at passfab.exe is the value we need. ![]() Edit > Segments > Rebase program is the first step for rebasing an address in IDA. It’s time to Rebase program the memory from IDA, which implies that the entire program will be shifted by the designated numbers of bytes. Now that you’ve viewed the memory map using ALT+M, scroll down till you see something similar.Ĭopy the initial address 0x00320000, ASLR may cause you to see a different address, but the idea is the same. All of the addresses in the IDA Tools are reconfigured using this address, where passfab starts. Because this software has ASLR Address Stack Layer Randomize protection enabled, which means the address is always changing, we need to get the hex address, for example, 0x01234567, where the passfab.exe program starts. Run as administrator on 圆4dbg because PassFab only works with this privilege. The first step is to load a program in 圆4dbg, which is simple to do (press ALT+A to connect the program). For static analysis, I use IDA PRO 6.8 Version, and for dynamic analysis, I use 圆4dbg. Let’s get our hands dirty: To disassemble the software and recreate each step, we need a few tools. Although this program can be exploited without endangering users, I was still able to steal all of the (Serial Keys) using this buffer. As a result of a change in memory caused by exceeding the initial storage allocation, extra data leak into other storage locations and may corrupt or replace the data they contain. I’ll define buffer overflow vulnerability for the first time.īuffer Overflow: The buffer serves as a temporary storage location for data. ![]() Hello, my name is Moldovan Darius, also known as Here is a Proof of Concept that shows how I was able to break the PassFab software using the buffer overflow bug.
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