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+----- Thread: Modify strings of executable file (Windows) (/showthread.php?tid=6294284)
Modify strings of executable file (Windows) - loomixx - Mar 14, 2025
I need to increase the length of a string inside a binary, but I keep running into issues. Here’s what I’ve tried so far:
1. Replacing the string while keeping the same length - it works fine as long as the new string is the same size as the old one.
2. Shortening the string - it also works if I replace unused space with 00.
Heres what i tried:
I wrote simple hello world in C.
The target string was "Hello, World!" (in hex 48 65 6C 6C 6F 2C 20 57 6F 72 6C 64 21)
I changed it via HxD to:
48 65 6C 6C 6F 2C 20 57 6F 00 00 00 00
It resulted in "Hello, Wo" (since \0 terminates it).
The program printed "Hello, Wo", which I expected
The problem comes when I increase the string length. If I change original string to this:
48 65 6C 6C 6F 2C 20 57 6F 72 6C 64 21 21
(added an extra "!"), the program just refuses to run.
It seems like I’m overwriting something critical, or the binary expects a fixed size.
How do I properly increase a string’s length in an executable without breaking it? Is this even possible?