CODEWITHSUNDEEP
cassemblybuffer-overflowshellcodeexecve
John Doe
John Doe

Reputation: 61

Shellcode: perform 2 execve() calls

I am trying to write shellcode in assembly. I need to perform a /usr/bin/killall command AND a /usr/bin/wget command. I have both commands running perfectly in shellcode with the execve() syscall. But now I want to combine these 2, but this is not possible because the program exits when the first execve() call is executed. (from the man pages of execve() : execve() does not return on success).

How can I perform 2 execve() calls? Or is there another way to call both /usr/bin/killall and /usr/bin/wget from the same shell code?

Greets and thanks in advance!

Upvotes: 2

Views: 944

Answers (2)

perror
perror

Reputation: 7386

First of all, it is not possible to execute two execve() one after the other. Simply because, by definition, the execve() call will override the memory of the original process with the new one and you will never be able to switch back to the original process again.

The second option that you propose (merging /usr/bin/killall and /usr/bin/wget into the shellcode) is perfectly possible if the killall command is not killing the process executing the shellcode itself. If it is the case, I really need more information about why is this behavior is needed because it seems a bit absurd to me (but I certainly miss the context in which you are running your shellcode).

Upvotes: 1

jbr
jbr

Reputation: 6258

When you use the exec-family of functions, the program you call it with is substituted into the current process. So when the first execve-call is made, your entire process image disappears, and thus second call is never made. To get around this you must fork another process before calling execve.

Upvotes: 5

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