CODEWITHSUNDEEP
linuxelfdisassemblypatch
gipsh
gipsh

Reputation: 598

Is it possible to modify the value of a char* in .rodata section of an elf?

I know you can easily patch the ELF with a value of the same size. But, what if I want to change it for a bigger value? Is there a way to un-pack and re-pack the ELF?

I'm not interested in patching the binary in memory.

Upvotes: 1

Views: 1648

Answers (1)

Employed Russian
Employed Russian

Reputation: 213957

But, what if I want to change it for a bigger value?

You apparently want a longer string, not a bigger value.

is there a way to un-pack and re-pack the ELF?

Depends on what kind of ELF you are asking about. If you have a relocatable object file of type ET_REL (usually .o), then modification is fairly trivial: you simply append a new section to the end of the file (usually string contents reside in .rodata section, so you would make a (larger) copy of it, and then update corresponding section header's .sh_offset and .sh_size to point to the right place in the file.

On the other hand, for a linked ELF binary (ET_DYN or ET_EXEC), the task is so complicated as to be very hard (nearly impossible), because multiple pointers would need to be updated, and the placement in memory is not arbitrary.

Upvotes: 4

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