About ReDemPtion

Redemption is a versatile RDP proxy, meaning one will connect to remote desktops through Redemption. This allows to centralize remote connection creating a single end point for several desktops. About the versatile part, Redemption is able to connect to VNC servers, permitting connection from Windows® to Linux, for instance. It is only known to run on Linux (Ubuntu, Debian, Arch Linux) and no effort were made to port it to Win32, MacOS or FreeBSD.

Redemption is also able to record sessions in .wrm/.mwrm files and then convert them to mp4 video.

The project also contains 2 RDP clients:

• A desktop client in projects/qtclient (supports RDP and VNC)
• A web client in projects/jsclient that uses a websocket (option that must be enabled in the proxy configuration).

1. Compilation
   1. Dependencies
   2. FFmpeg
      1. Ubuntu / Debian
      2. Other distros
   3. Compile from source
   4. Run tests
      1. Verbose tests
      2. Compilation error in test_snappy.cpp
      3. Runtime error in test_video_capture.cpp
   5. Modes and options
      1. Setting build variables
         1. Local installation
         2. Musl libc
   6. Add .cpp file
2. Run Redemption
3. Setting Redemption
   1. Migrate the configuration to the next version
4. Session recording
   1. Convert .mwrm/.wrm capture to video
5. Compile proxy_recorder
6. Packaging
7. Test files

Compilation

For automatic compilation, a Dockerfile is available. This one is based on Ubuntu, but other linux systems are supported like Debian or Alpine. For the latter, -s MUSL_LIBC=1 must be added on the line containing bjam and the libgettext package must be added in the installed package.

The following is for manual installation.

Dependencies

To compile Redemption you need the following packages:

• libboost-tools-dev (contains bjam and b2: software build tool) (https://www.bfgroup.xyz/b2/)
• libboost-test-dev (unit-test dependency)
• zlib1g-dev
• libssl-dev
• libkrb5-dev
• libsnappy-dev
• libpng-dev
• libbz2-dev
• libhyperscan-dev
• libffmpeg-dev (see below)
• gettext
• g++ >= 8.0 or clang++ >= 7.0 or other C++17 compiler

apt install libboost-tools-dev libboost-test-dev libssl-dev libkrb5-dev libsnappy-dev libpng-dev libbz2-dev libhyperscan-dev

FFmpeg

If your goal is to use the proxy without doing any video conversion (the recording is still available), you can disable FFmpeg by adding NO_FFMPEG=1 to your environment variables before compiling.

For more information on available variables, see Setting build variables.

Ubuntu / Debian

Package:

• libavcodec-dev
• libavformat-dev
• libavutil-dev
• libswscale-dev
• libx264-dev

apt install libavcodec-dev libavformat-dev libavutil-dev libswscale-dev libx264-dev

Other distros

• https://github.com/FFmpeg/FFmpeg/archive/n2.5.11.tar.gz (or later)

And set the build variables (optionally)

• FFMPEG_INC_PATH=/my/ffmpeg/include/path
• FFMPEG_LIB_PATH=/my/ffmpeg/library/path (/!\ without / terminal)
• FFMPEG_LINK_MODE=shared (static or shared, shared by default)

Compile from source

(Instruction for Debian 9).

Well, that's pretty easy once you installed the required dependencies.

Go to the redemption folder then just run (as user):

bjam exe libs

(Always put a target name, otherwise the tests will also be compiled and executed).

Then install (as administrator):

bjam install

bjam install depends on exe libs, if you have enough rights, it is not necessary to run the first command.

Binaries are located by default in /usr/local/bin. For a user install, see Local Installation.

You can choose your compiler and its version by adding toolset=${compiler} on the command line: bjam toolset=gcc exe libs / bjam toolset=clang-16 exe libs (see https://www.bfgroup.xyz/b2/manual/main/index.html#bbv2.overview.configuration and tools/bjam/user-config.jam).

You will find bjam auto-completion files for bash and zsh in the tools/bjam folder.

Note: If you intend to make changes to the proxy, it is not necessary to reinstall it each time, the executable created in the bin folder can be run directly. It is also possible to install only resources via bjam install-resources without installing the executable and library.

Run tests

Tests are compiled and run with bjam tests. You can also compile everything (exe, lib, tests + runtime) with just bjam (without specifying a target).

Each test file has its corresponding target and can be run independently:

bjam tests/utils/test_rect  # for tests/utils/test_rect.cpp
bjam test_rect              # same

In addition, each folder has an associated target name:

bjam tests/utils        # all tests in tests/utils/
bjam tests/utils.norec  # all tests in tests/utils/, but not recursively (exclude sub-directories)

For more user-friendly test output, you can look at what's in tools/bjam.

Verbose tests

By default, tests do not display log messages. These can be enabled by playing with the REDEMPTION_LOG_PRINT environment variable.

export REDEMPTION_LOG_PRINT=1
bjam tests

• REDEMPTION_LOG_PRINT=1 enable all logs
• REDEMPTION_LOG_PRINT=e for error and debug only
• REDEMPTION_LOG_PRINT=d for debug only
• REDEMPTION_LOG_PRINT=w for other than info

In debug mode and if the BOOST_STACKTRACE option is set, the Error constructor displays a call stack. This can be controlled with the environment variable REDEMPTION_FILTER_ERROR which contains a comma separated list of values to ignore.

• REDEMPTION_FILTER_ERROR= no filter
• REDEMPTION_FILTER_ERROR='*' filter all
• REDEMPTION_FILTER_ERROR=ERR_TRANSPORT_NO_MORE_DATA,ERR_SEC filter specific errors (see src/core/error.hpp).

Compilation error in test_snappy.cpp

Under some versions of Ubuntu, Snappy dev files are broken and SNAPPY_MAJOR, SNAPPY_MINOR and SNAPPY_PATCHLEVEL macros are not defined. The simplest way to fix that is editing /usr/include/snappy-stubs-public.h and define these above SNAPPY_VERSION.

Like below (change values depending on your snappy package).

// apt show libsnappy-dev | grep Version
// Version: 1.1.7-1
#define SNAPPY_MAJOR 1
#define SNAPPY_MINOR 1
#define SNAPPY_PATCHLEVEL 7

Runtime error in test_video_capture.cpp

These errors should only occur after an FFmpeg update or regression.

The tests on the video generation check the size of the output files. This way of doing is not perfect and the result depends on the version of ffmpeg and the quality of the encoders. There is no other way than to change the range of possible values.

Modes and options

Bjam is configured to offer 3 compilation modes:

• release: default
• debug: Compile in debug mode
• san: Compile in debug mode + sanitizers (asan, lsan, ubsan)

The mode is selected by adding variant=${mode} or simply ${mode} to the bjam command line.

There are also several variables for setting compiler options:

• -s cxx-color: default auto never always
• -s cxx-lto: off on fat linker-plugin
• -s cxx-relro: default off on full
• -s cxx-stack-protector: off on strong all
• ...

Complete list with bjam cxx_help.

Finally, bjam provides cxxflags and linkflags to add options to the compiler and linker. This is useful for example to remove warnings with the latest openssl versions.

bjam variant=debug -s cxx-lto=on cxxflags='-Wno-deprecated-declarations' targets...

By default, bjam compiles everything into a folder named bin, you can change this with --build-dir=new-path.

Setting build variables

List with bjam env_help.

These variables can be used as environment variables or passed on the bjam command line with -s varname=value.

Example with ffmpeg:

bjam -s FFMPEG_INC_PATH=$HOME/ffmpeg/includes ....
# or
FFMPEG_INC_PATH=$HOME/ffmpeg/includes bjam ....
# or
export FFMPEG_INC_PATH=$HOME/ffmpeg/includes bjam ....
bjam ....

Local installation

If you have already compiled anything before this step, it is best to delete your bin folder (everything will be recompiled) or remove app_path_exe.o file inside.

The paths to the installed files can be listed with bjam env_help. The minimum requirement is the following (change the install_path variable to your liking).

install_path="$HOME/redemption"
export PREFIX="$install_path"/usr/local
export ETC_PREFIX="$install_path"/etc
export VAR_PREFIX="$install_path"/var
export SESSION_PREFIX="$install_path"/var/lib
export PID_PATH="$install_path"/var/run
bjam ....

Musl libc

bjam -s MUSL_LIBC=1 ....

Add .cpp file

The compiled files are referenced in targets.jam. This is a file that is generated via ./tools/bjam/gen_targets.py and is updated with bjam targets.jam or ./tools/bjam/gen_targets.py > targets.jam.

When you added a .cpp file or there is a link error, remember to run bjam targets.jam.

Run Redemption

For a local test, the usual options are -n and -f. The first option prevents Redemption from forking in the background and the second makes sure no other instance is running.

rdpproxy -nf

And now what ? If everything went ok, you should be facing a waiting daemon ! You need two more things; first a client to connect to Redemption, second a server with RDP running (a Windows server, Windows XP Pro, etc.).

Redemption uses a hook file to get its target, username and password. This file is tools/passthrough/passthrough.py communicates with rdpproxy through a unix socket. This is referenced as "authentifier" in proxy logs.

./tools/passthrough/passthrough.py

Now, at that point you'll just have two servers waiting for connections not much fun. You still have to run some RDP client to connect to proxy. Choose whichever you like xfreerdp, rdesktop, remmina, tsclient on Linux or of course mstsc.exe if you are on Windows. All are supposed to work. If some problem occurs just report it to us so that we can correct it.

Examples with freerdp when the proxy runs on the same host as the client:

xfreerdp /v:127.0.0.1

A dialog box should open in which you can type a device ip, username and a password.

These 3 fields can be pre-filled by configuring the connection identifiers sent by your RDP client. With the default passthrough.py, the target address must be put with the login in the form username@target_ip:

xfreerdp /v:127.0.0.1 /u:username@10.10.43.11 /p:password

With the default passthrough.py at least internal services should work. Try login internal@bouncer2 or internal@card.

xfreerdp /v:127.0.0.1 /u:internal@bouncer2

passthrough.py is made to be edited and only provides the bare minimum. Here is a diagram that shows the basic interaction between these components:

flowchart LR
    client[RDP Client] --> rdpproxy[rdpproxy -nf]
    rdpproxy --> |user info|passthrough.py
    passthrough.py --> |"remote target info:<br/>username, password<br/> ..."|rdpproxy
    rdpproxy --> server[RDP Server]

Loading

Setting Redemption

Redemption's configuration can be found in a rdpproxy.ini file that is not installed (you will have to create it yourself) or via the --config-file=<path> option.

The default location of rdpproxy.ini can be found with the command rdpproxy -c |& grep rdpproxy.ini or rdpinichecker.

rdpproxy also has a --print-default-ini which displays all the default options and values in comments. You can use rdpinihecker -p to get a condensed display.

Some of these options can be modified by passthrough.py by filling in the dictionary sent to send_data(). See tools/passthrough/README.md.

Migrate the configuration to the next version

Between 2 versions, some options can be moved or deleted. tools/conf_migration_tool/rdp_conf_migrate.py allows to automatically migrate a file from an old version.

Session recording

To enable session recording, the line kv['is_rec'] = '1' in passthrough.py must be uncommented.

Convert .mwrm/.wrm capture to video

.mwrm and .wrm are the native capture formats when recording is enabled. The following line will transform a recording into an mp4 video:

redrec -u -i file.mwrm -o output_prefix

Note: use redrec -h to see the list of options.

Compile proxy_recorder

Proxy recorder is a tools used to record dialog between a client and an RDP server without any modification of the data by redemption. This allows to record reference traffic for replaying it later. It is useful for having available new parts or the RDP protocol in a reproducible way and replaying traffic when implementing the new orders. This tools is not (yet) packaged with redemption and delivered as stand-alone.

It can be compiled using static c++ libraries (usefull to use the runtime on systems where reference compiler is older) using the command line below. Links with openssl and kerberos are still dynamic and using shared libraries.

bjam -a -d2 toolset=gcc-7 proxy_recorder linkflags=-static-libstdc++

Exemple call line for proxy_recorder:

proxy_recorder --target-host 10.10.47.252 -p 3389 -P 8000 --nla-username myusername --nla-password mypassword -t dump-%d.out

Packaging

Create Debian package with

./packaging/package.sh

Test files

See test_framework directory.