ssh¶

Opening Software on a Remote Server via X11¶

On the server (X11-SERVER)¶

# Install necessary packages
yum install -y xorg-x11-xauth
# This is a rough implementation;
# Should use sed for a more precisec onfiguration.
echo "unset LIBGL_ALWAYS_INDIRECT" >> ~/.bashrc
echo "export DISPLAY=:0.0" >> ~/.bashrc
sudo bash -c "echo 'X11Forwarding yes
X11UseLocalhost no
X11DisplayOffset 10' >> /etc/ssh/sshd_config"
sudo systemctl restart sshd

On the client (X11-CLIENT)¶

ssh -XYT "${X11-SERVER-IP}" xclock

Compiling OpenSSH with musl¶

Updating OpenSSH on a Linux host is a common task. According to CVE-2024-6387, this security risk affects many openssh-server compiled with glibc. In this article, I will try to compile a static OpenSSH on Alpine Linux and see whether it can run properly on RHEL.

Requirements¶

musl, pre-installed on Alpine Linux.
openssh-9.8p1
Other system packages: see below

Steps¶

1. Install Required System Packages¶

apk update && apk upgrade && apk add autoconf build-base linux-headers linux-pam-dev zlib-dev openssl-dev zlib-static musl-dev openssl-libs-static

2. Download Source Code Packages¶

Download the source code packages to the /tmp/src/ directory.

3. Compile openssh¶

rm -rf /tmp/openssh_src/
mkdir -p /tmp/openssh_src/
tar xf "${SRC_DIR}/${openssh_package}" \
   -C /tmp/openssh_src/ \
   --strip-components 1
cd /tmp/openssh_src/ || exit 99
(
   autoconf
   ./configure --prefix="${PREFIX_DIR}" \
      --sysconfdir=/etc/ssh \
      --with-zlib \
      --with-ssl-dir=/usr/include/openssl \
      --with-ldflags=-static
      make -j "$(($(nproc) + 1))" &&
      make install
) 2>&1 | tee /tmp/compile_openssh.log

4. Something To be Improved¶

sshd won't log to wtmp and btmp file
no pam intergration
no gssapi support
no kerbros support