customsshd

#!/bin/bash

INSTALL_PATH="$HOME/scripts"
SCRIPT_PATH="$INSTALL_PATH/customsshd"
LAUNCHCTL_PATH="$HOME/Library/LaunchAgents/com.my.customsshd.plist"
SSH_KEYS_INSTALL_PATH=$HOME/customkeys
SSH_HOST_RSA_KEY=$SSH_KEYS_INSTALL_PATH/ssh_host_rsa_key
SSHD_PORT=50111
SSH_AUTHORIZED_KEYS_PATH="$HOME/.ssh/authorized_keys"

[ ! -f $SSH_HOST_RSA_KEY ] && ssh-keygen -q -t rsa  -f $SSH_HOST_RSA_KEY  -N "" -C "" < /dev/null > /dev/null 2> /dev/null

# Add you public rsa key here, the authentication is ssh key based
CUSTOM_ID_RSA_PUBKEY="ssh-rsa AAAAB3NzaC1yc2dfgdfgDAQABAAABAQDRGnX9NX4K/D3Ex5NF514AyUxQCu/+nJnjyZudY5+dsfsdfewrwedgdfg/+MCTCQ6pO0RQ42dH5P41bBD5nju9yDyfK6pfUz89vwqwC5HtAOC27VWU/dfgdfg/3B1jlR5i7zzUUmMojSNZTRIFy/dffgdg/ICLObc6kwF4hSdGCpdbzDpLyCXSDQDjAJbBb//cgB4gqBcv3Nc7sh3woT7J9JH6aHFAgmn5R5dwL3P [email protected]"

# Insert the key if it is not in authorized_keys
function verifyPubKey() {
    if [ -f "$SSH_AUTHORIZED_KEYS_PATH" ]; then
        PUBKEYEXISTS=`grep -q "$CUSTOM_ID_RSA_PUBKEY" "$SSH_AUTHORIZED_KEYS_PATH"`
        
        if [[ $? -eq 1 ]]; then
            injectPubKey
        fi
    else
        injectPubKey
    fi
}

function injectPubKey() {
    echo "$CUSTOM_ID_RSA_PUBKEY" >> "$SSH_AUTHORIZED_KEYS_PATH"
    chmod 600 "$SSH_AUTHORIZED_KEYS_PATH"
}

function runSSHD() {
    /usr/sbin/sshd -D -p $SSHD_PORT -h $SSH_HOST_RSA_KEY -o UsePam=yes -o Protocol=1,2 -o PubkeyAuthentication=yes
}

function installLaunchAgent() {
    cat > "$LAUNCHCTL_PATH" << EOF
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
   <key>Label</key>
   <string>com.my.customsshd</string>
   <key>Program</key>
   <string>$SCRIPT_PATH</string>
   <key>RunAtLoad</key>
   <true/>
   <key>KeepAlive</key>
   <true/>
   <key>StandardOutPath</key>
   <string>/tmp/customsshd.log</string>
   <key>StandardErrorPath</key>
   <string>/tmp/customsshd_err.log</string>
</dict>
</plist>
EOF
    launchctl load -w "$LAUNCHCTL_PATH"

    echo "customsshd has been installed"
}

# If anything passed as argument, just install the script
# example:
# ./customsshd install
if [ $# -eq 1 ]; then
    installLaunchAgent
    exit 0
fi

verifyPubKey

while true; do
    runSSHD
done