CODEWITHSUNDEEP
bashshellsyntaxshdd
Reiki Yamya
Reiki Yamya

Reputation: 95

system() fails while the command runs fine in the terminal

This is frustrating. I am writing a C program where I need to create a self modifying dd, i.e., the dd is capable of modifying itself on the run [ifd = open(stdin) and ofd = open (/proc/self/mem)]

When I run the following, directly in terminal, the setarch command sets the ADDR_NO_RANDOMIZE flag and a self modifying dd gets succesfully created. However, when I run it through system() it fails with an error.

system( "setarch x86_64 -R dd of=/proc/self/mem bs=1 seek=$(( 0x555555554000 + 0xa823 )) conv=notrunc 10<&0 11<&1");

Maybe I am missing something very obvious as I am not very good at shell programming.

The error is as follows:

dd: unrecognized operand ‘10’
Try 'dd --help' for more information.

Note: I have used 10 and 11 to duplicate stdin and stdout File Descriptors in my code.

Thanks a-million!

Upvotes: 0

Views: 82

Answers (1)

that other guy
that other guy

Reputation: 123430

POSIX sh only guarantees support for FDs from 0 to 9.

If you need FDs higher than that, you should run your command in bash or another shell that supports this:

system("bash -c 'setarch x86_64 -R dd of=/proc/self/mem "
       "bs=1 seek=$(( SEGMENT + OFFSET )) conv=notrunc 10<&0 11<&1'");

Upvotes: 4

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