Toolbox Aid

August 8th, 2024 8:02 PM Mr. Q Categories: Command, github, Synology

In environments where direct installation of software is restricted or unavailable, compiling binaries from source can be an effective solution. Synology NAS users often face challenges when trying to use certain utilities, such as ssh-agent and ssh-add, due to the limited software availability. This guide demonstrates how to leverage Docker to compile ssh-agent and ssh-add from the OpenSSH source code within a Docker container and then transfer these compiled binaries to a Synology NAS for execution.

To compile ssh-agent and ssh-add, which are part of the OpenSSH suite, you’ll need to download and compile the OpenSSH source code. Here’s how you can do this inside a Docker container.

Step 1: Prepare the Docker Container

1. Start a Docker Container:

• Use a Linux image with development tools. Ubuntu or Alpine can work, but Ubuntu may be easier for compiling due to more comprehensive package support.

   docker run -it --name dev-container --rm ubuntu:latest /bin/bash

2. Install Dependencies:

• Install the necessary tools and libraries required for building OpenSSH.

   apt update
   apt install -y build-essential wget zlib1g-dev libssl-dev libpam0g-dev

Step 2: Download the OpenSSH Source Code

1. Download the Latest OpenSSH Source:

• Use wget to download the OpenSSH source code from the official site.

   wget https://cdn.openbsd.org/pub/OpenBSD/OpenSSH/portable/openssh-9.4p1.tar.gz

Replace the version number with the latest version available at the time.

2. Extract the Source Code:

• Extract the downloaded tarball.

   tar -xzvf openssh-9.4p1.tar.gz
   cd openssh-9.4p1

Step 3: Compile ssh-agent and ssh-add

1. Configure the Build:

• Run the configure script to prepare the build environment.

   ./configure

If you only want to build ssh-agent and ssh-add, you can customize the build process, but for simplicity, let’s proceed with the full build.

2. Compile the Code:

• Compile the entire OpenSSH suite.

   make

This will compile all the components, including ssh-agent and ssh-add.

Step 4: Extract the Compiled Binaries

1. Locate the Binaries:

• After compilation, the binaries for ssh-agent and ssh-add should be in the ssh-agent/ and ssh-add/ directories, respectively.

1. Copy the Binaries to Your Host System:

• Use docker cp to copy the binaries from the Docker container to your host system or Synology NAS.

   docker cp dev-container:/path/to/openssh-9.4p1/ssh-agent /path/to/your/destination/on/nas
   docker cp dev-container:/path/to/openssh-9.4p1/ssh-add /path/to/your/destination/on/nas

Replace /path/to/openssh-9.4p1/ssh-agent with the actual path to the binary inside the container, and /path/to/your/destination/on/nas with the path where you want to store the binaries on your NAS.

Step 5: Use the Binaries on Your NAS

1. Set Permissions:

• Ensure the binaries have execution permissions.

   chmod +x /path/to/your/destination/on/nas/ssh-agent
   chmod +x /path/to/your/destination/on/nas/ssh-add

2. Run the Binaries:

• You can now use ssh-agent and ssh-add directly on your Synology NAS.

Additional Considerations

• Dependencies: Make sure that any libraries required by ssh-agent and ssh-add are available on your NAS.
• Static Compilation: If your NAS does not have all necessary shared libraries, consider statically compiling the binaries by adding -static to the CFLAGS in the Makefile.

This approach will give you the ssh-agent and ssh-add binaries compiled from source, which you can transfer and use on your NAS.

Summary:

This guide provided a step-by-step approach to compiling the ssh-agent and ssh-add utilities from the OpenSSH source code within a Docker container. By utilizing Docker, users can create a controlled environment with all the necessary dependencies, ensuring a successful compilation process. Once compiled, the binaries were transferred to a Synology NAS, enabling their use on the NAS without requiring direct installation. This method is particularly useful for users who need custom-built tools in environments with limited package management options.