Question

I need to insert a generated file into an exe at the time of download. Currently, I create an “empty” file (filled with a repeating character) and package that with the exe. When it comes time to download, I look at the bytes for the installer, find the file by looking for the repeating character, and insert the generated file.

This process however is not working. The repeating character just does not show in the bytes. But I am certain the file is there as it is unpacked if I run the exe. Am I doing something wrong or is inserting a file into an exe even possible?

Also note that I am using Inno Setup Script v5.5.1 to compile the project into an exe.

Answer 1

If you want to change the contents of a file specified in a [Files] entry and compiled into the setup executable, then you must:

1. Make a dummy file that is at least as large as the largest content you will want to insert.
2. Fill the file (or at least the first 64 bytes or so) with something unique and easily distinguishable.
3. Mark its [Files] entry with the “nocompression noencryption dontverifychecksum” flags.

You should then be able to scan the resulting executable for the marker in #2 and then substitute the data that you want. Note however that doing this might invalidate any digital signature on the setup file, although I haven’t tested this to be sure.

Note that if the content you are inserting is smaller than the dummy file size, the extra bytes will still remain on the end of your inserted content. So whatever reads the file will have to have some way to ignore that or to recognise the end of the interesting content.