Datasets:
Devilishcode
/
hacking

Dataset card Data Studio Files
xet
 Community
text
stringlengths
0
1.99k
```
Uh, oh - something went wrong. Let's take a look in GDB to see what
happened.
```
root@cheribsd-morello-purecap:~/vuln # gdb -q ./heap2 heap2.core
Reading symbols from ./heap2...
[New LWP 100064]
Core was generated by `./heap2'.
Program terminated with signal SIGPROT, CHERI protection violation.
Capability tag fault.
#0 strlen (str=0x40c0f000 [rwRW,0x40c0f000-0x40c0f040] (invalid) "CHERI2")
at /home/user/cheri/cheribsd/lib/libc/string/strlen.c:143
```
So what did that `malloc_revoke()` function do? This is a function
provided by the CHERI SDK that forces a cleanup of the quarantine list in
the allocator. This means that the capability corresponding to `ptr1` has
its tag bit cleared. From the CHERI man pages [5], `malloc_revoke()`
"triggers a full flush of the quarantine and scan of memory to ensure that
all references to memory previously quarantined by free(3) or realloc(3)
are revoked upon successful return". Ultimately, we can see that `strlen()`
was called (presumably by `printf()` due to the `%s` format specifier) with
an invalid capability.
## Where next?
I hope you've enjoyed this figurative toe-dip into CHERI both as a concept,
and also after getting our hands dirty with some solid examples.
Personally, I think the platform has some solid design ideas that will
certainly make classic exploitation techniques harder. I'm hesitant to say
that any of those existing techniques have been rendered obsolescent
because, as far as I'm aware, CHERI is yet to be battle tested as a
security mechanism on a target that's of significant interest to exploit
developers; like a flagship smartphone or a games console.
If you'd like to dive deeper into CHERI, then I recommend checking out the
Morello documentation more closely [2]. There's also the "CHERI Exercises"
repo on GitHub [6] by the CHERI team at Cambridge University which
highlights more scenarios where CHERI introduces new complications for
exploit writers. This article should give you a solid foundation to be able
to tackle those exercises.
Remember that CHERI doesn't stop at Morello with Aarch64! CHERI
specifications also exist for MIPS and RISC-V, with x86_64 in the works too.
In particular, there is the CherIoT (CHERI Internet-Of-Things) project [7]
which uses the RISC-V CHERI extension to power an IoT platform. This
project makes extensive use of the compartmentalisation feature of CHERI
that I briefly mentioned earlier in the article. This is a method of
process isolation using sealed capabilities without having to separate
processes into different memory spaces.
It's also worth taking a look at the output of `./cheribuild.py
--list-targets` - there are already build definitions for things like
Apache, Nginx, KDE Plasma, Wayland, FFmpeg, and even DOOM!
## Closing Thoughts
First of all, if you've made it this far - thank you! I hope you found this
read worth your time and that you learnt something - even if it was just to
scratch that itch to understand a little better what this CHERI thing is
all about. That's certainly why I chose to take a look at it. If CHERI
takes off in the consumer space in the future, I think bug hunters and
xdevs alike will enjoy the new challenged posed by it. And if it doesn't
take off, then it will still remain an interesting experiment that we can
continue to play with in VMs.
Obligatory shoutouts go to netspooky, dnoiz, hermit, gren, srsns, bane,
remy, computeruser, zeta, chill, buses, rqu, iximeow, ilya, kyo and The
Binary Golf Association (you should go play Binary Golf [8]).
## Links and References
[1] https://www.arm.com/architecture/cpu/morello
[2] https://developer.arm.com/documentation/ddi0606/ak
[3] https://github.com/CTSRD-CHERI/cheribuild
[4] https://ctsrd-cheri.github.io/cheribsd-getting-started/features/
temporal.html
[5] https://man.cheribsd.org/cgi-bin/man.cgi/dev/malloc_revoke_enabled.3
[6] https://github.com/CTSRD-CHERI/cheri-exercises/tree/master
[7] https://cheriot.org/
[8] https://binary.golf/
|=-----------------------------------------------------------------------=|
|=-------------=[ 5 - High-Performance Network Scanning ]=---------------=|
|=-------------------------=[ With AF_XDP ]=-----------------------------=|
|=-----------------------------------------------------------------------=|
|=---------------------------=[ c3l3si4n ]=------------------------------=|
|=-----------------------------------------------------------------------=|
-- Table of contents
0 - Introduction
1 - The Slow Path: Traditional Scanning Methods
1.0 - Per-Connection Syscall Overhead
1.1 - Inefficient Packet Filtering with AF_PACKET
2 - Kernel Bypass and Fastpath Architectures