[Aboriginal] Using native-build.sh for An Android native C compiler

Earlence Fernandes earlenceferns at gmail.com
Sat Jul 16 11:49:18 PDT 2011

Yes, it is bionic's libc.
This is what readelf says about the header:
$ readelf -h /system/lib/libc.so
ELF Header:
  Magic:   7f 45 4c 46 01 01 01 00 00 00 00 00 00 00 00 00
  Class:                             ELF32
  Data:                              2's complement, little endian
  Version:                           1 (current)
  OS/ABI:                            UNIX - System V
  ABI Version:                       0
  Type:                              DYN (Shared object file)
  Machine:                           ARM
  Version:                           0x1
  Entry point address:               0x0
  Start of program headers:          52 (bytes into file)
  Start of section headers:          273024 (bytes into file)
  Flags:                             0x5000000, Version5 EABI
  Size of this header:               52 (bytes)
  Size of program headers:           32 (bytes)
  Number of program headers:         6
  Size of section headers:           40 (bytes)
  Number of section headers:         22
  Section header string table index: 21

therefore, We can conclude
1. its a proper library for ARM EABI
2. its no an issue specific to my build (bcoz of the simple program I wrote
to read this libc.so and the result of running it with multiple builds).
3. its a ucLibC thing.

What I'm trying to do is basically compile and execute one of the root
exploits directly on the device. No! I'm not a malware writer, but we are
security researchers (http://few.vu.nl/~earlence)

That is the GingerBreak exploit that I'm trying to compile.


On Sat, Jul 16, 2011 at 8:18 PM, Rob Landley <rob at landley.net> wrote:

> On 07/16/2011 12:59 PM, Earlence Fernandes wrote:
> > Thank you for the reply.
> >
> > 1. gb is custom software (sorry I should have made a note of that).
> > 2. I rewrote a simple program with one line
> >
> > void *dlh = dlopen("/system/lib/libc.so", RTLD_NOW);
> Um, question: is that bionic's libc you're attempting to dlopen?  (It's
> an ELF binary, right?  What does readelf -a say about it?  Note that
> attemting to dlopen() a linker script may not end well.)
> Have you tried to dlopen() one of the other shared libraries that comes
> with uClibc just to make sure that the issue is dlopen() and not it
> being really confused by that particular library?
> > I tried it on my build - same problem. seg fault.
> > I tried it with the build you sent me, same problem - seg faults again.
> >
> > Is it possible to write a program precompiled with Android's dynamic
> > linker that will bootstrap the uclibc version? (I know going off topic
> > here).
> I don't understand what you're trying to do there, could you explain?
> (You can exec one program from another, if that's what you mean by
> boostrap.)
> > Or would it be possible to link the program against android ldl.a in the
> > first place?
> I expect it's possible to link it, whether the result would work
> involves knowing more about android than I do.
> > -Earlence
> Rob
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