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User-friendly C Library to perform TCP streams reassembly and IPv4/6 defragmentation
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README.md

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Introduction

What is libntoh?

Libntoh aims to be an user-friendly library to provide a easy way to perform defragmentation and reassembly of network/transport/(more?) protocols.

Why libntoh?

It's true there are some libraries which aims to do the same things (like libnids), but libntoh is intended to provide a flexible, thread-safe and highly configurable environment for the final user. And most of all, libntoh is released under Modified BSD License to avoid many license issues.

Which protocols does libntoh support?

Currently libntoh performs IPv4/IPv6 defragmentation and TCP reassembly over IPv4 and IPv6.

Mailing List

There is a mailing list for libntoh development issues: libntoh-dev@safetybits.net

Getting the source

$ git clone git://github.com/sch3m4/libntoh.git
Cloning into 'libntoh'...
remote: Counting objects: 962, done.
remote: Total 962 (delta 0), reused 0 (delta 0), pack-reused 962
Receiving objects: 100% (962/962), 1.01 MiB | 121.00 KiB/s, done.
Resolving deltas: 100% (483/483), done.
Checking connectivity... hecho.
$

Dependencies

To successfully compile libntoh you only need gcc, make, cmake, pkg-config and libpthread-dev.

Debian-like OS:

$ sudo apt-get install cmake libpthread-dev gcc make build-essential pkg-config

If you want to generate the source code documentation, you will also need doxygen:

$ sudo apt-get install doxygen

Note: pkg-config isn't really needed but it helps. (See "ntohexample" compilation)

You need CMake to compile libntoh and ntohexample.

Compilation instructions

$ cd libntoh/src
../src$ ./build.sh
[i] pkg-config found: /usr/bin/pkg-config
[i] cmake found: /usr/bin/cmake
[i] make found: /usr/bin/make
[i] PKG_CONFIG_PATH set to: /usr/local/lib/pkgconfig

-- The C compiler identification is GNU 4.8.4
-- The CXX compiler identification is GNU 4.8.4
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Looking for include file pthread.h
-- Looking for include file pthread.h - found
-- Looking for pthread_create
-- Looking for pthread_create - not found
-- Looking for pthread_create in pthreads
-- Looking for pthread_create in pthreads - not found
-- Looking for pthread_create in pthread
-- Looking for pthread_create in pthread - found
-- Found Threads: TRUE  
-- Configuring done
-- Generating done
-- Build files have been written to: /tmp/libntoh/src/build
Scanning dependencies of target ntoh
[ 16%] Building C object CMakeFiles/ntoh.dir/libntoh.c.o
[ 33%] Building C object CMakeFiles/ntoh.dir/tcpreassembly.c.o
[ 50%] Building C object CMakeFiles/ntoh.dir/ipv4defrag.c.o
[ 66%] Building C object CMakeFiles/ntoh.dir/ipv6defrag.c.o
[ 83%] Building C object CMakeFiles/ntoh.dir/common.c.o
[100%] Building C object CMakeFiles/ntoh.dir/sfhash.c.o
Linking C shared library libntoh.so
[100%] Built target ntoh
Do you want to perform the installation? [y/n]: y
[sudo] password for chema: 
[100%] Built target ntoh
Install the project...
-- Install configuration: "Release"
-- Installing: /usr/local/lib/libntoh.so
-- Installing: /usr/local/include/libntoh/libntoh.h
-- Installing: /usr/local/include/libntoh/tcpreassembly.h
-- Installing: /usr/local/include/libntoh/sfhash.h
-- Installing: /usr/local/include/libntoh/ipv4defrag.h
-- Installing: /usr/local/include/libntoh/ipv6defrag.h
-- Installing: /usr/local/include/libntoh/common.h
-- Installing: /usr/local/lib/pkgconfig/ntoh.pc
$

For a more detailed description refer to https://github.com/sch3m4/libntoh/wiki

Libntoh Examples

You can find a working source code example for each supported protocol in "examples" folder:

libntoh$ ls examples/ -R
examples/:
c

examples/c:
ipv4  ipv6  tcp_ipv4  tcp_ipv6

examples/c/ipv4:
build.sh  CMakeLists.txt  example.c

examples/c/ipv6:
build.sh  CMakeLists.txt  example.c

examples/c/tcp_ipv4:
build.sh  CMakeLists.txt  example.c

examples/c/tcp_ipv6:
build.sh  CMakeLists.txt  example.c

The default installation prefix for libntoh is "/usr/local", so if you plan to link against libntoh using pkg-config remember to add "/usr/local/lib/pkgconfig" to PKG_CONFIG_PATH:

$ export PKG_CONFIG_PATH=/usr/local/lib/pkgconfig
$ pkg-config --libs --cflags ntoh -I/usr/local/include/libntoh  -L/usr/local/lib -lntoh

On the other hand you can change the installation prefix by defining CMAKE_INSTALL_PREFIX:

$ cmake ../ -DCMAKE_INSTALL_PREFIX=/usr

So the new installation prefix will be "/usr"

For more information, refer to the wiki page.

TCP/IPv4 Example Output:

$ sudo ./ntohexample 
###########################
#     libntoh Example     #
# ----------------------- #
# Written by Chema Garcia #
# ----------------------- #
#  http://safetybits.net  #
#   chema@safetybits.net  #
###########################

[i] libntoh version: 0.4a

[+] Usage: ./ntohexample <options>

+ Options:
      -i | --iface <val> -----> Interface to read packets from
      -f | --file <val> ------> File path to read packets from
      -F | --filter <val> ----> Capture filter (default: "ip and tcp")
      -c | --client ----------> Receive client data only
      -s | --server ----------> Receive server data only

$ sudo ./ntohexample -i eth0 -F "tcp and host 10.0.0.1 and port 22"

###########################
#     libntoh Example     #
# ----------------------- #
# Written by Chema Garcia #
# ----------------------- #
#  http://safetybits.net  #
#   chema@safetybits.net  #
###########################

[i] libntoh version: 0.4a

[i] Source: eth0 / Ethernet
[i] Filter: tcp and host 10.0.0.1 and port 22
[i] Receive data from client: Yes
[i] Receive data from server: Yes
[i] Max. TCP streams allowed: 1024
[i] Max. IPv4 flows allowed: 1024


[SYN Sent] 10.0.0.2:40819 (SYN Sent | Window: 233600) ---> 10.0.0.1:22 (Listen | Window: 0)

[SYN Rcv] 10.0.0.1:22 (SYN Rcv | Window: 4194240) ---> 10.0.0.2:40819 (SYN Sent | Window: 233600)

[Established] 10.0.0.2:40819 (Established | Window: 233600) ---> 10.0.0.1:22 (Established | Window: 4194240)

[Established] 10.0.0.1:22 (Established | Window: 4194240) ---> 10.0.0.2:40819 (Established | Window: 233600)
      + Data segment | Bytes: 49 SEQ: 1 ACK: 1 Next SEQ: 50

[Established] 10.0.0.2:40819 (Established | Window: 233600) ---> 10.0.0.1:22 (Established | Window: 4193384)
      + Data segment | Bytes: 32 SEQ: 1 ACK: 50 Next SEQ: 33

[Established] 10.0.0.1:22 (Established | Window: 4194240) ---> 10.0.0.2:40819 (Established | Window: 233600)
      + Data segment | Bytes: 856 SEQ: 50 ACK: 33 Next SEQ: 906

[Established] 10.0.0.2:40819 (Established | Window: 233600) ---> 10.0.0.1:22 (Established | Window: 4194240)
      + Data segment | Bytes: 1272 SEQ: 33 ACK: 906 Next SEQ: 1305

[Established] 10.0.0.2:40819 (Established | Window: 233600) ---> 10.0.0.1:22 (Established | Window: 4193928)
      + Data segment | Bytes: 80 SEQ: 1305 ACK: 906 Next SEQ: 1385

[Established] 10.0.0.1:22 (Established | Window: 4194240) ---> 10.0.0.2:40819 (Established | Window: 233600)
      + Data segment | Bytes: 312 SEQ: 906 ACK: 1385 Next SEQ: 1218

[Established] 10.0.0.2:40819 (Established | Window: 233600) ---> 10.0.0.1:22 (Established | Window: 4194240)
      + Data segment | Bytes: 16 SEQ: 1385 ACK: 1218 Next SEQ: 1401

[Established] 10.0.0.2:40819 (Established | Window: 233600) ---> 10.0.0.1:22 (Established | Window: 4194192)
      + Data segment | Bytes: 48 SEQ: 1401 ACK: 1218 Next SEQ: 1449

[Established] 10.0.0.1:22 (Established | Window: 4194240) ---> 10.0.0.2:40819 (Established | Window: 233600)
      + Data segment | Bytes: 48 SEQ: 1218 ACK: 1449 Next SEQ: 1266

[Established] 10.0.0.2:40819 (Established | Window: 233600) ---> 10.0.0.1:22 (Established | Window: 4194176)
      + Data segment | Bytes: 64 SEQ: 1449 ACK: 1266 Next SEQ: 1513

[Established] 10.0.0.1:22 (Established | Window: 4194240) ---> 10.0.0.2:40819 (Established | Window: 233600)
      + Data segment | Bytes: 64 SEQ: 1266 ACK: 1513 Next SEQ: 1330

[Established] 10.0.0.2:40819 (Established | Window: 233600) ---> 10.0.0.1:22 (Established | Window: 4193920)
      + Data segment | Bytes: 368 SEQ: 1513 ACK: 1330 Next SEQ: 1881

[Established] 10.0.0.1:22 (Established | Window: 4194240) ---> 10.0.0.2:40819 (Established | Window: 233600)
      + Data segment | Bytes: 320 SEQ: 1330 ACK: 1881 Next SEQ: 1650

[Established] 10.0.0.2:40819 (Established | Window: 233600) ---> 10.0.0.1:22 (Established | Window: 4194208)
      + Data segment | Bytes: 640 SEQ: 1881 ACK: 1650 Next SEQ: 2521

[Established] 10.0.0.1:22 (Established | Window: 4194240) ---> 10.0.0.2:40819 (Established | Window: 233600)
      + Data segment | Bytes: 32 SEQ: 1650 ACK: 2521 Next SEQ: 1682

[Established] 10.0.0.2:40819 (Established | Window: 233600) ---> 10.0.0.1:22 (Established | Window: 4194192)
      + Data segment | Bytes: 128 SEQ: 2521 ACK: 1682 Next SEQ: 2649

[Established] 10.0.0.1:22 (Established | Window: 4194240) ---> 10.0.0.2:40819 (Established | Window: 233488)
      + Data segment | Bytes: 48 SEQ: 1682 ACK: 2649 Next SEQ: 1730

[Established] 10.0.0.2:40819 (Established | Window: 233600) ---> 10.0.0.1:22 (Established | Window: 4194160)
      + Data segment | Bytes: 112 SEQ: 2649 ACK: 1730 Next SEQ: 2761

[Established] 10.0.0.1:22 (Established | Window: 4194208) ---> 10.0.0.2:40819 (Established | Window: 233600)
      + Data segment | Bytes: 80 SEQ: 1730 ACK: 2761 Next SEQ: 1810

[Established] 10.0.0.1:22 (Established | Window: 4194240) ---> 10.0.0.2:40819 (Established | Window: 233600)
      + Data segment | Bytes: 32 SEQ: 1810 ACK: 2761 Next SEQ: 1842

[Established] 10.0.0.1:22 (Established | Window: 4194240) ---> 10.0.0.2:40819 (Established | Window: 233568)
      + Data segment | Bytes: 160 SEQ: 1842 ACK: 2761 Next SEQ: 2002

[Established] 10.0.0.2:40819 (Established | Window: 233536) ---> 10.0.0.1:22 (Established | Window: 4194240)
      + Data segment | Bytes: 32 SEQ: 2761 ACK: 2002 Next SEQ: 2793

[Established] 10.0.0.2:40819 (Established | Window: 233600) ---> 10.0.0.1:22 (Established | Window: 4194240)
      + Data segment | Bytes: 64 SEQ: 2793 ACK: 2002 Next SEQ: 2857

[Closing] 10.0.0.2:40819 (Fin Wait1 | Window: 233600) ---> 10.0.0.1:22 (Close Wait | Window: 4194240)

[Closing] 10.0.0.1:22 (Last ACK | Window: 4194240) ---> 10.0.0.2:40819 (Closing | Window: 233600)

[Closed] 10.0.0.2:40819 (Time Wait | Window: 233600) ---> 10.0.0.1:22 (Closed | Window: 4194240)

[+] Capture finished!
$
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