Friends of Waccamaw Library Newsletter: August 2020

Conferencia: Bad Guys Never Sleep. Entrevista: Nueva Dimensión. Podcast: Ciberseguriad & Gaming.

Ayer hice dos publicaciones porque no quería dejar pasar más tiempo antes de dejar constancia que la estafa de los Bitcoins usando mi imagen era eso: una estafa. Así que hoy el post que os traigo es cortito, solo unos vídeos que he subido a mi canal Youtube para que los veáis si se os han escapado.

Figura 1: Conferencia: Bad Guys Never Sleep.
Entrevista: Nueva Dimensión. Podcast: Ciberseguriad & Gaming.

El primero de ellos ya lo saqué ayer, pero como no os había hablado de él, os lo vuelvo a dejar. Se trata de la conferencia que di en México vía VC y en la que hablaba de cómo los malos, con el objetivo de lucrarse utilizan cualquier técnica que sea necesaria - sencilla o compleja, nueva o antigua - para cometer sus delitos.

Figura 2: Bad Guys Never Sleep

Curiosamente, en esa charla hablaba de las estafa de los BitCoins usando la imagen de personas populares, que al cabo del tiempo han hecho con mi imagen. Así que ten mucho cuidado con tu dinero y no te creas todas las Fake News que veas por la red.

El segundo vídeo que so dejo es una entrevista que me hizo hace muy pocos días el periodista Juan Gómez para el programa de radio Nueva Dimensión donde hablamos de de hacking, de los riesgos de privacidad, la inteligencia artificial usada para suplantar personas, etcétera...

Figura 3: Entrevista a Chema Alonso en Nueva Dimensión

Mucho e lo que hablamos se basa en la conferencia que dicté como Keynote en el Security Innovation Day 2019 de ElevenPaths, que si no las visto la tienes aquí mismo. Mucho de lo que cuento en la entrevista lo puedes ver en directo con demos.

Figura 4: Keynote de Chema Alonso en Security Innovation Day 2019

Y por último, un nuevo Podcast de ElevenPaths Radio, en este caso con Josep Albors de ESET y Andrés Naranjo, aka TheXXLMan, hablando de Ciberseguridad & Gaming, que, estoy convencido, a los gamers os resultará más que interesante.

Figura 5: ElevenPaths Radio: Ciberseguridad & Gaming

Y nada más, si queréis contactar con alguno de nosotros, ya sabéis que gracias a ESET puedes conseguir 100 Tempos gratis en MyPublicInbox.

Saludos Malignos!

Autor: Chema Alonso (Contactar con Chema Alonso)

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Reversing Rust String And Str Datatypes

Lets build an app that uses several data-types in order to see how is stored from a low level perspective.

Rust string data-types

The two first main objects are "str" and String, lets check also the constructors.

Imports and functions

Even such a basic program links several libraries and occupy 2,568Kb, it's really not using the imports and expots the runtime functions even the main.

Even a simple string operation needs 544 functions on rust:

Main function

If you expected see a clear main function I regret to say that rust doesn't seem a real low-level language In spite of having a full control of the memory.

Ghidra turns crazy when tries to do the recursive parsing of the rust code, and finally we have the libc _start function, the endless loop after main is the way Ghidra decompiles the HLT instruction.

If we jump to main, we see a function call, the first parameter is rust_main as I named it below:

If we search "hello world" on the Defined Strings sections, matches at the end of a large string

After doing "clear code bytes" we can see the string and the reference:

We can see that the literal is stored in an non null terminated string, or most likely an array of bytes. we have a bunch of byte arrays and pointed from the code to the beginning.
Let's follow the ref. [ctrl]+[shift]+[f] and we got the references that points to the rust main function.

After several naming thanks to the Ghidra comments that identify the rust runtime functions, the rust main looks more understandable.
See below the ref to "hello world" that is passed to the string allocated hard-coding the size, because is non-null terminated string and there is no way to size this, this also helps to the rust performance, and avoid the c/c++ problems when you forgot the write the null byte for example miscalculating the size on a memcpy.

Regarding the string object, the allocator internals will reveal the structure in static.
alloc_string function call a function that calls a function that calls a function and so on, so this is the stack (also on static using the Ghidra code comments)

1. _$LT$alloc..string..String$u20$as$u20$core..convert..From$LT$$RF$str$GT$$GT$::from::h752d6ce1f15e4125
2. alloc::str::_$LT$impl$u20$alloc..borrow..ToOwned$u20$for$u20$str$GT$::to_owned::h649c495e0f441934
3. alloc::slice::_$LT$impl$u20$alloc..borrow..ToOwned$u20$for$u20$$u5b$T$u5d$$GT$::to_owned::h1eac45d28
4. alloc::slice::_$LT$impl$u20$$u5b$T$u5d$$GT$::to_vec::h25257986b8057640
5. alloc::slice::hack::to_vec::h37a40daa915357ad
6. core::slice::_$LT$impl$u20$$u5b$T$u5d$$GT$::len::h2af5e6c76291f524
7. alloc::vec::Vec$LT$T$GT$::extend_from_slice::h190290413e8e57a2
8. _$LT$alloc..vec..Vec$LT$T$GT$$u20$as$u20$alloc..vec..SpecExtend$LT$$RF$T$C$core..slice..Iter$LT$T$GT$$GT$$GT$::spec_extend::h451c2f92a49f9caa
...

Well I'm not gonna talk about the performance impact on stack but really to program well reusing code grants the maintainability and its good, and I'm sure that the rust developed had measured that and don't compensate to hardcode directly every constructor.

At this point we have two options, check the rust source code, or try to figure out the string object in dynamic with gdb.

Source code

Let's explain this group of substructures having rust source code in the hand.
The string object is defined at string.rs and it's simply an u8 type vector.

And the definition of vector can be found at vec.rs and is composed by a raw vector an the len which is the usize datatype.

The RawVector is a struct that helds the pointer to the null terminated string stored on an Unique object, and also contains the allocation pointer, here raw_vec.rs definition.

The cap field is the capacity of the allocation and a is the allocator:

Finally the Unique object structure contains a pointer to the null terminated string, and also a one byte marker core::marker::PhantomData

Dynamic analysis

The first parameter of the constructor is the interesting one, and in x64 arch is on RDI register, the extrange sequence RDI,RSI,RDX,RCX it sounds like ACDC with a bit of imagination (di-si-d-c)

So the RDI parámeter is the pointer to the string object:

So RDI contains the stack address pointer that points the the heap address 0x5578f030.
Remember to disable ASLR to correlate the addresses with Ghidra, there is also a plugin to do the synchronization.

Having symbols we can do:
p mystring

and we get the following structure:

String::String {
vec: alloc::vec::Vec {
buf: alloc::raw_vec::RawVec {
ptr: core::ptr::unique::Unique {
pointer: 0x555555790130 "hello world\000",
_marker: core::marker::PhantomData
},
cap: 11,
a: alloc::alloc::Global
},
len: 11
}
}

If the binary was compiled with symbols we can walk the substructures in this way:

(gdb) p mystring.vec.buf.ptr
$6 = core::ptr::unique::Unique {pointer: 0x555555790130 "hello world\000", _marker: core::marker::PhantomData}

(gdb) p mystring.vec.len

$8 = 11

If we try to get the pointer of each substructure we would find out that the the pointer is the same:

If we look at this pointer, we have two dwords that are the pointer to the null terminated string, and also 0xb which is the size, this structure is a vector.

The pionter to the c string is 0x555555790130

This seems the c++ string but, let's look a bit deeper:

RawVector
Vector:
(gdb) x/wx 0x7fffffffdf50
0x7fffffffdf50: 0x55790130 -> low dword c string pointer
0x7fffffffdf54: 0x00005555 -> hight dword c string pointer
0x7fffffffdf58: 0x0000000b -> len

0x7fffffffdf5c: 0x00000000
0x7fffffffdf60: 0x0000000b -> low cap (capacity)
0x7fffffffdf64: 0x00000000 -> hight cap
0x7fffffffdf68: 0xf722fe27 -> low a (allocator)
0x7fffffffdf6c: 0x00007fff -> hight a
0x7fffffffdf70: 0x00000005

So in this case the whole object is in stack except the null-terminated string.

SQL Injection Attacks And Defense | By Justin Clarke | Pdf Free

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Friends of Waccamaw Library Newsletter

Sunday, August 30, 2020