swipswaps / lime

LiME (formerly DMD) is a Loadable Kernel Module (LKM), which allows the acquisition of volatile memory from Linux and Linux-based devices, such as those powered by Android. The tool supports acquiring memory either to the file system of the device or over the network. LiME is unique in that it is the first tool that allows full memory captures from Android devices. It also minimizes its interaction between user and kernel space processes during acquisition, which allows it to produce memory captures that are more forensically sound than those of other tools designed for Linux memory acquisition.

LiME ~ Linux Memory Extractor

A Loadable Kernel Module (LKM) which allows for volatile memory acquisition from Linux and Linux-based devices, such as Android. This makes LiME unique as it is the first tool that allows for full memory captures on Android devices. It also minimizes its interaction between user and kernel space processes during acquisition, which allows it to produce memory captures that are more forensically sound than those of other tools designed for Linux memory acquisition.

Table of Contents

• Features
• Usage
• Examples
• Presentation

Features

• Full Android memory acquisition
• Acquisition over network interface
• Minimal process footprint
• Hash of dumped memory

Usage

Detailed documentation on LiME's usage and internals can be found in the "doc" directory of the project.

LiME utilizes the insmod command to load the module, passing required arguments for its execution.

insmod ./lime.ko "path=<outfile | tcp:<port>> format=<raw|padded|lime> [digest=<digest>] [dio=<0|1>]"

path (required):     outfile ~ name of file to write to on local system (SD Card)
                     tcp:port ~ network port to communicate over
        
format (required):   padded ~ pads all non-System RAM ranges with 0s
                     lime ~ each range prepended with fixed-size header containing address space info
                     raw ~ concatenates all System RAM ranges (warning : original position of dumped memory is likely to be lost)

digest (optional):   Hash the RAM and provide a .digest file with the sum.
                     Supports kernel version 2.6.11 and up. See below for
                     available digest options.

compress (optional): 1 ~ compress output with zlib
                     0 ~ do not compress (default)

dio (optional):      1 ~ attempt to enable Direct IO
                     0 ~ do not attempt Direct IO (default)
        
localhostonly (optional):  1 ~ restricts the tcp to only listen on localhost,
                           0 ~ binds on all interfaces (default)

timeout (optional): 1000 ~ max amount of milliseconds tolerated to read a page (default).
                           If a page exceeds the timeout all the memory region are skipped.
                       0 ~ disable the timeout so the slow region will be acquired.

                           This feature is only available on kernel versions >= 2.6.35. 

Examples

In this example we use adb to load LiME and then start it with acquisition performed over the network

$ adb push lime.ko /sdcard/lime.ko
$ adb forward tcp:4444 tcp:4444
$ adb shell
$ su
# insmod /sdcard/lime.ko "path=tcp:4444 format=lime"

Now on the host machine, we can establish the connection and acquire memory using netcat

$ nc localhost 4444 > ram.lime

Acquiring to sdcard

# insmod /sdcard/lime.ko "path=/sdcard/ram.lime format=lime"

Available Digests

Really LiME will support any digest algorithm that the kernel library can. Collecting a digest file when dumping over tcp will require 2 separate connections.

$ nc localhost 4444 > ram.lime
$ nc localhost 4444 > ram.sha1

For a quick reference here is a list of supported digests.

All kernel versions

crc32c
md4, md5
sha1, sha224, sha256, sha384, sha512
wp512, wp384, wp256

4.10 and up

sha3-224, sha3-256, sha3-384, sha3-512

3.0 and up

rmd128, rmd160, rmd256, rmd320

Compression

Compression can reduce significantly the time required to acquire a memory capture. It can achieve the speedup of 4x over uncompressed transfers with a few memory overhead (~ 24 KB).

The RAM file will be in the zlib format, which is different from the gzip or zip formats. The reason is that the deflate library embedded in the kernel do not support them.

To decompress it you can use pigz or any zlib-compatible library.

$ nc localhost 4444 | unpigz > ram.lime

Note that only the RAM file is compressed. The digest file is not compressed, and the hash value will match the uncompressed data.

Presentation

LiME was first presented at Shmoocon 2012 by Joe Sylve.
Youtube~ Android Mind Reading: Memory Acquisition and Analysis with DMD and Volatility