An omelet-egg-hunter shellcode for Cisco IOS

This shellcode looks for parts of the second stage shellcode in IP packets within the IO-Memory of Cisco networking equipment and collects them together.

The following parameters should be passed to the shellcode:

r19 - start of the IO-memory region
r21 - size of shellcode
r22 - source ip
r25 - destination address (address to which the shellcode will be copied)

r20 - 0 (cur_size)
r24 - 0 (cur_ip_id)

To build the omelet-egg-hunter you must specify three parameters:

• SIGNATURE is an unique value, by this value the omelet-egg-hunter determines the first part of the shellcode. You should also place the same value at the beginning of the 2nd stage shellcode;

• IOS_15 or IOS_12 indicates for which Cisco IOS family the shellcode will build (the offset of the IP-header in a Packet Data structure depends on this);

• COPY is the address of the function ios_move_handler that copies data with invalidation of I-Cache, D-Cache. The address of this function can be found in the Cisco IOS image by the binary pattern 7C 00 20 AC.

Build command:

> make iomem_hunter.bin -e IOS=IOS_15 -e SIGNATURE=0xC0DEC0DE -e COPY=0xAABBCCDD