String decoding error

[a4865g]

Hi,
The demo execution is no problem.

But I change the secret string = "[OBFS_ENC]nnnnnnn", it makes string decoding error.

Like this:

Thanks!

[4g3nt47]

Hi there!

Thank you for the report, and my apologies for the late response.

I've looked into this and it seems the issue is not with the obfuscator, but on how the compiler bundles the string. For some reasons, if the target string is 6 or 7 characters long, the compiler does not add a null byte at the end of the string, which is what the encoder relies on to calculate length of target strings. This is how the binary is compiled when using a 7 character string as secret;

In the above image, the text in red box is the target string. Notice it was truncated to 6 characters, and instead of a null byte, it was followed with 0x01. No null byte appeared until 4 more characters, making the obfuscator believe the target string is 11 bytes long, which leads to incorrect output.

When trying with any input that does not have a length of 6 or 7, the binary is compiled as expected. In the below example I used nnnn as secret, and you can see the null bytes immediately after;

Weird enough, this seems to only happen in the demo, not in the actual project I wrote the obfuscator for. You can see an example with 7 character target string in line 105 of https://github.com/4g3nt47/Striker/blob/master/agent/C/src/striker.c

I honestly don't understand how this is happening, but I will keep looking. Thank you 😊