feat: add peer-fingerprint authentication mode (OpenVPN 2.6+) (#1437)

## Summary

Implements support for OpenVPN's `--peer-fingerprint` option, enabling
PKI-less authentication using SHA256 certificate fingerprints instead of
a CA chain.

Closes #1361

## Changes

- Add `--auth-mode` option (`pki` or `fingerprint`) for install command
- Use Easy-RSA's `self-sign-server` and `self-sign-client` commands for
fingerprint mode
- Server stores client fingerprints in `<peer-fingerprint>` block in
`server.conf`
- Clients verify server using `peer-fingerprint` directive instead of CA
- Revocation removes fingerprint from config and reloads OpenVPN
(instant effect)
- Version check ensures OpenVPN 2.6+ when fingerprint mode is selected

## Usage

```bash
# Interactive mode prompts for auth mode choice

# CLI mode
./openvpn-install.sh install --auth-mode fingerprint
```

## Comparison

| Aspect | PKI Mode | Fingerprint Mode |
|--------|----------|------------------|
| Server cert | CA-signed | Self-signed |
| Client cert | CA-signed | Self-signed |
| Revocation | CRL-based | Remove fingerprint |
| OpenVPN | Any version | 2.6.0+ required |
| Best for | Large deployments | Small/home setups |

.github/workflows/docker-test.yml

@@ -118,6 +118,15 @@ jobs:
               name: tls-crypt-v2
               sig: crypt-v2
               key_file: tls-crypt-v2.key
+          # Test peer-fingerprint authentication mode (OpenVPN 2.6+)
+          - os:
+              name: ubuntu-24.04-fingerprint
+              image: ubuntu:24.04
+              auth_mode: fingerprint
+            tls:
+              name: tls-crypt-v2
+              sig: crypt-v2
+              key_file: tls-crypt-v2.key
 
     name: ${{ matrix.os.name }}
     steps:
@@ -166,6 +175,7 @@ jobs:
             -e TLS_SIG=${{ matrix.tls.sig }} \
             -e TLS_KEY_FILE=${{ matrix.tls.key_file }} \
             -e CLIENT_IPV6=${{ matrix.os.client_ipv6 && 'y' || 'n' }} \
+            -e AUTH_MODE=${{ matrix.os.auth_mode || 'pki' }} \
             openvpn-server
 
       - name: Wait for server installation and startup

README.md

@@ -62,6 +62,7 @@ That said, OpenVPN still makes sense when you need:
 - Randomised server certificate name
 - Choice to protect clients with a password (private key encryption)
 - Option to allow multiple devices to use the same client profile simultaneously (disables persistent IP addresses)
+- **Peer fingerprint authentication** (OpenVPN 2.6+): Simplified WireGuard-like authentication without a CA
 - Many other little things!
 
 ## Compatibility
@@ -317,6 +318,7 @@ The `install` command supports many options for customization:
 - `--rsa-bits <2048|3072|4096>` - RSA key size (default: `2048`)
 - `--hmac <alg>` - HMAC algorithm (default: `SHA256`). Options: `SHA256`, `SHA384`, `SHA512`
 - `--tls-sig <mode>` - TLS mode (default: `crypt-v2`). Options: `crypt-v2`, `crypt`, `auth`
+- `--auth-mode <mode>` - Authentication mode (default: `pki`). Options: `pki` (CA-based), `fingerprint` (peer-fingerprint, requires OpenVPN 2.6+)
 - `--tls-version-min <1.2|1.3>` - Minimum TLS version (default: `1.2`)
 - `--tls-ciphersuites <list>` - TLS 1.3 cipher suites, colon-separated (default: `TLS_AES_256_GCM_SHA384:TLS_AES_128_GCM_SHA256:TLS_CHACHA20_POLY1305_SHA256`)
 - `--tls-groups <list>` - Key exchange groups, colon-separated (default: `X25519:prime256v1:secp384r1:secp521r1`)
@@ -470,6 +472,45 @@ It defaults to ECDSA with `prime256v1`.
 
 OpenVPN uses `SHA-256` as the signature hash by default, and so does the script. It provides no other choice as of now.
 
+### Authentication Mode
+
+The script supports two authentication modes:
+
+#### PKI Mode (default)
+
+Traditional Certificate Authority (CA) based authentication. The server and all clients have certificates signed by the same CA. Client revocation is handled via Certificate Revocation Lists (CRL).
+
+This is the recommended mode for larger deployments where you need:
+
+- Centralized certificate management
+- Standard CRL-based revocation
+- Compatibility with all OpenVPN versions
+
+#### Peer Fingerprint Mode (OpenVPN 2.6+)
+
+A simplified WireGuard-like authentication model using SHA256 certificate fingerprints instead of a CA chain. Each peer (server and clients) has a self-signed certificate, and peers authenticate each other by verifying fingerprints.
+
+```bash
+# Install with fingerprint mode
+./openvpn-install.sh install --auth-mode fingerprint
+```
+
+Benefits:
+
+- Simpler setup: No CA infrastructure needed
+- Easier to understand: Similar to SSH's `known_hosts` model
+- Ideal for small setups: Home networks, labs, small teams
+
+How it works:
+
+1. Server generates a self-signed certificate and stores its fingerprint
+2. Each client generates a self-signed certificate
+3. Client fingerprints are added to the server's `<peer-fingerprint>` block
+4. Clients verify the server using the server's fingerprint
+5. Revocation removes the fingerprint from the server config (no CRL needed)
+
+Trade-off: Revoking a client requires reloading OpenVPN (fingerprints are in server.conf). In PKI mode, the CRL file is re-read automatically on new connections.
+
 ### Data channel
 
 > [!NOTE]

openvpn-install.sh

@@ -239,6 +239,8 @@ show_install_help() {
 				(default: X25519:prime256v1:secp384r1:secp521r1)
 			--hmac <alg>          HMAC algorithm: SHA256, SHA384, SHA512 (default: SHA256)
 			--tls-sig <mode>      TLS mode: crypt-v2, crypt, auth (default: crypt-v2)
+			--auth-mode <mode>    Auth mode: pki, fingerprint (default: pki)
+				fingerprint requires OpenVPN 2.6+
 			--server-cert-days <n>  Server cert validity in days (default: 3650)
 
 		Other Options:
@@ -477,6 +479,9 @@ readonly TLS_VERSIONS=("1.2" "1.3")
 # TLS signature modes (use strings)
 readonly TLS_SIG_MODES=("crypt-v2" "crypt" "auth")
 
+# Authentication modes: pki (CA-based) or fingerprint (peer-fingerprint, OpenVPN 2.6+)
+readonly AUTH_MODES=("pki" "fingerprint")
+
 # HMAC algorithms
 readonly HMAC_ALGS=("SHA256" "SHA384" "SHA512")
 
@@ -516,6 +521,7 @@ set_installation_defaults() {
 	TLS_GROUPS="${TLS_GROUPS:-X25519:prime256v1:secp384r1:secp521r1}"
 	HMAC_ALG="${HMAC_ALG:-SHA256}"
 	TLS_SIG="${TLS_SIG:-crypt-v2}"
+	AUTH_MODE="${AUTH_MODE:-pki}"
 
 	# Derive CC_CIPHER from CERT_TYPE if not set
 	if [[ -z $CC_CIPHER ]]; then
@@ -536,6 +542,18 @@ set_installation_defaults() {
 	# are computed in prepare_network_config() which is called after validation
 }
 
+# Version comparison: returns 0 if version1 >= version2
+version_ge() {
+	local ver1="$1" ver2="$2"
+	# Use sort -V for version comparison
+	[[ "$(printf '%s\n%s' "$ver1" "$ver2" | sort -V | head -n1)" == "$ver2" ]]
+}
+
+# Get installed OpenVPN version (e.g., "2.6.12")
+get_openvpn_version() {
+	openvpn --version 2>/dev/null | head -1 | awk '{print $2}'
+}
+
 # Validation functions
 validate_port() {
 	local port="$1"
@@ -642,6 +660,21 @@ validate_configuration() {
 	*) log_fatal "Invalid TLS signature mode: $TLS_SIG. Must be 'crypt-v2', 'crypt', or 'auth'." ;;
 	esac
 
+	# Validate AUTH_MODE
+	case "$AUTH_MODE" in
+	pki | fingerprint) ;;
+	*) log_fatal "Invalid auth mode: $AUTH_MODE. Must be 'pki' or 'fingerprint'." ;;
+	esac
+
+	# Fingerprint mode requires OpenVPN 2.6+
+	if [[ $AUTH_MODE == "fingerprint" ]]; then
+		local openvpn_ver
+		openvpn_ver=$(get_openvpn_version)
+		if [[ -n "$openvpn_ver" ]] && ! version_ge "$openvpn_ver" "2.6.0"; then
+			log_fatal "Fingerprint mode requires OpenVPN 2.6.0 or later. Installed version: $openvpn_ver"
+		fi
+	fi
+
 	# Validate PORT
 	if ! [[ "$PORT" =~ ^[0-9]+$ ]] || [[ "$PORT" -lt 1 ]] || [[ "$PORT" -gt 65535 ]]; then
 		log_fatal "Invalid port: $PORT. Must be a number between 1 and 65535."
@@ -1034,6 +1067,14 @@ cmd_install() {
 			esac
 			shift 2
 			;;
+		--auth-mode)
+			[[ -z "${2:-}" ]] && log_fatal "--auth-mode requires an argument"
+			case "$2" in
+			pki | fingerprint) AUTH_MODE="$2" ;;
+			*) log_fatal "Invalid auth mode: $2. Use 'pki' or 'fingerprint'." ;;
+			esac
+			shift 2
+			;;
 		--server-cert-days)
 			[[ -z "${2:-}" ]] && log_fatal "--server-cert-days requires an argument"
 			validate_positive_int "$2" "server-cert-days"
@@ -1251,6 +1292,7 @@ cmd_client_add() {
 	fi
 
 	newClient
+	exit 0
 }
 
 # Handle client list command
@@ -2336,6 +2378,30 @@ function installQuestions() {
 		done
 	fi
 	log_menu ""
+	log_prompt "Choose the authentication mode:"
+	log_menu "   1) PKI (Certificate Authority) - Traditional CA-based authentication (recommended for larger setups)"
+	log_menu "   2) Peer Fingerprint - Simplified WireGuard-like authentication using certificate fingerprints"
+	log_menu "      Note: Fingerprint mode requires OpenVPN 2.6+ and is ideal for small/home setups"
+	local auth_mode_choice
+	until [[ $auth_mode_choice =~ ^[1-2]$ ]]; do
+		read -rp "Authentication mode [1-2]: " -e -i 1 auth_mode_choice
+	done
+	case $auth_mode_choice in
+	1)
+		AUTH_MODE="pki"
+		;;
+	2)
+		AUTH_MODE="fingerprint"
+		# Verify OpenVPN 2.6+ is available for fingerprint mode
+		local openvpn_ver
+		openvpn_ver=$(get_openvpn_version)
+		if [[ -n "$openvpn_ver" ]] && ! version_ge "$openvpn_ver" "2.6.0"; then
+			log_warn "OpenVPN $openvpn_ver detected. Fingerprint mode requires 2.6.0+."
+			log_warn "OpenVPN 2.6+ will be installed during setup."
+		fi
+		;;
+	esac
+	log_menu ""
 	log_prompt "Do you want to customize encryption settings?"
 	log_prompt "Unless you know what you're doing, you should stick with the default parameters provided by the script."
 	log_prompt "Note that whatever you choose, all the choices presented in the script are safe (unlike OpenVPN's defaults)."
@@ -2541,6 +2607,7 @@ function installOpenVPN() {
 		log_info "  DNS=$DNS"
 		[[ -n $MTU ]] && log_info "  MTU=$MTU"
 		log_info "  MULTI_CLIENT=$MULTI_CLIENT"
+		log_info "  AUTH_MODE=$AUTH_MODE"
 		log_info "  CLIENT=$CLIENT"
 		log_info "  CLIENT_CERT_DURATION_DAYS=$CLIENT_CERT_DURATION_DAYS"
 		log_info "  SERVER_CERT_DURATION_DAYS=$SERVER_CERT_DURATION_DAYS"
@@ -2680,15 +2747,34 @@ function installOpenVPN() {
 		# Create the PKI, set up the CA, the DH params and the server certificate
 		log_info "Initializing PKI..."
 		run_cmd_fatal "Initializing PKI" ./easyrsa init-pki
-		export EASYRSA_CA_EXPIRE=$DEFAULT_CERT_VALIDITY_DURATION_DAYS
-		log_info "Building CA..."
-		run_cmd_fatal "Building CA" ./easyrsa --batch --req-cn="$SERVER_CN" build-ca nopass
 
-		export EASYRSA_CERT_EXPIRE=${SERVER_CERT_DURATION_DAYS:-$DEFAULT_CERT_VALIDITY_DURATION_DAYS}
+		if [[ $AUTH_MODE == "pki" ]]; then
-		log_info "Building server certificate..."
+			# Traditional PKI mode with CA
-		run_cmd_fatal "Building server certificate" ./easyrsa --batch build-server-full "$SERVER_NAME" nopass
+			export EASYRSA_CA_EXPIRE=$DEFAULT_CERT_VALIDITY_DURATION_DAYS
-		export EASYRSA_CRL_DAYS=$DEFAULT_CRL_VALIDITY_DURATION_DAYS
+			log_info "Building CA..."
-		run_cmd_fatal "Generating CRL" ./easyrsa gen-crl
+			run_cmd_fatal "Building CA" ./easyrsa --batch --req-cn="$SERVER_CN" build-ca nopass
+
+			export EASYRSA_CERT_EXPIRE=${SERVER_CERT_DURATION_DAYS:-$DEFAULT_CERT_VALIDITY_DURATION_DAYS}
+			log_info "Building server certificate..."
+			run_cmd_fatal "Building server certificate" ./easyrsa --batch build-server-full "$SERVER_NAME" nopass
+			export EASYRSA_CRL_DAYS=$DEFAULT_CRL_VALIDITY_DURATION_DAYS
+			run_cmd_fatal "Generating CRL" ./easyrsa gen-crl
+		else
+			# Fingerprint mode with self-signed certificates (OpenVPN 2.6+)
+			log_info "Building self-signed server certificate for fingerprint mode..."
+			export EASYRSA_CERT_EXPIRE=${SERVER_CERT_DURATION_DAYS:-$DEFAULT_CERT_VALIDITY_DURATION_DAYS}
+			run_cmd_fatal "Building self-signed server certificate" ./easyrsa --batch self-sign-server "$SERVER_NAME" nopass
+
+			# Extract and store server fingerprint
+			SERVER_FINGERPRINT=$(openssl x509 -in "pki/issued/$SERVER_NAME.crt" -fingerprint -sha256 -noout | cut -d'=' -f2)
+			if [[ -z $SERVER_FINGERPRINT ]]; then
+				log_error "Failed to extract server certificate fingerprint"
+				exit 1
+			fi
+			mkdir -p /etc/openvpn/server
+			echo "$SERVER_FINGERPRINT" >/etc/openvpn/server/server-fingerprint
+			log_info "Server fingerprint: $SERVER_FINGERPRINT"
+		fi
 
 		log_info "Generating TLS key..."
 		case $TLS_SIG in
@@ -2705,19 +2791,32 @@ function installOpenVPN() {
 			run_cmd_fatal "Generating tls-auth key" openvpn --genkey secret /etc/openvpn/server/tls-auth.key
 			;;
 		esac
+		# Store auth mode for later use
+		echo "$AUTH_MODE" >AUTH_MODE_GENERATED
 	else
 		# If easy-rsa is already installed, grab the generated SERVER_NAME
 		# for client configs
 		cd /etc/openvpn/server/easy-rsa/ || return
 		SERVER_NAME=$(cat SERVER_NAME_GENERATED)
+		# Read stored auth mode
+		if [[ -f AUTH_MODE_GENERATED ]]; then
+			AUTH_MODE=$(cat AUTH_MODE_GENERATED)
+		else
+			# Default to pki for existing installations
+			AUTH_MODE="pki"
+		fi
 	fi
 
 	# Move all the generated files
 	log_info "Copying certificates..."
-	run_cmd_fatal "Copying certificates to /etc/openvpn/server" cp pki/ca.crt pki/private/ca.key "pki/issued/$SERVER_NAME.crt" "pki/private/$SERVER_NAME.key" /etc/openvpn/server/easy-rsa/pki/crl.pem /etc/openvpn/server
+	if [[ $AUTH_MODE == "pki" ]]; then
-
+		run_cmd_fatal "Copying certificates to /etc/openvpn/server" cp pki/ca.crt pki/private/ca.key "pki/issued/$SERVER_NAME.crt" "pki/private/$SERVER_NAME.key" /etc/openvpn/server/easy-rsa/pki/crl.pem /etc/openvpn/server
-	# Make cert revocation list readable for non-root
+		# Make cert revocation list readable for non-root
-	run_cmd "Setting CRL permissions" chmod 644 /etc/openvpn/server/crl.pem
+		run_cmd "Setting CRL permissions" chmod 644 /etc/openvpn/server/crl.pem
+	else
+		# Fingerprint mode: only copy server cert and key (no CA or CRL)
+		run_cmd_fatal "Copying certificates to /etc/openvpn/server" cp "pki/issued/$SERVER_NAME.crt" "pki/private/$SERVER_NAME.key" /etc/openvpn/server
+	fi
 
 	# Generate server.conf
 	log_info "Generating server configuration..."
@@ -2931,9 +3030,13 @@ topology subnet" >>/etc/openvpn/server/server.conf
 		;;
 	esac
 
-	echo "crl-verify crl.pem
+	# Common server config options
-ca ca.crt
+	# PKI mode adds crl-verify, ca, and remote-cert-tls
-cert $SERVER_NAME.crt
+	# Fingerprint mode: <peer-fingerprint> block is added when first client is created
+	{
+		[[ $AUTH_MODE == "pki" ]] && echo "crl-verify crl.pem
+ca ca.crt"
+		echo "cert $SERVER_NAME.crt
 key $SERVER_NAME.key
 auth $HMAC_ALG
 cipher $CIPHER
@@ -2941,14 +3044,15 @@ ignore-unknown-option data-ciphers
 data-ciphers $CIPHER
 ncp-ciphers $CIPHER
 tls-server
-tls-version-min $TLS_VERSION_MIN
+tls-version-min $TLS_VERSION_MIN"
-remote-cert-tls client
+		[[ $AUTH_MODE == "pki" ]] && echo "remote-cert-tls client"
-tls-cipher $CC_CIPHER
+		echo "tls-cipher $CC_CIPHER
 tls-ciphersuites $TLS13_CIPHERSUITES
 client-config-dir ccd
 status /var/log/openvpn/status.log
 management /var/run/openvpn/server.sock unix
-verb 3" >>/etc/openvpn/server/server.conf
+verb 3"
+	} >>/etc/openvpn/server/server.conf
 
 	# Create management socket directory
 	run_cmd_fatal "Creating management socket directory" mkdir -p /var/run/openvpn
@@ -3028,7 +3132,11 @@ verb 3" >>/etc/openvpn/server/server.conf
 
 	run_cmd "Reloading systemd" systemctl daemon-reload
 	run_cmd "Enabling OpenVPN service" systemctl enable openvpn-server@server
-	run_cmd "Starting OpenVPN service" systemctl restart openvpn-server@server
+	# In fingerprint mode, delay service start until first client is created
+	# (OpenVPN requires at least one fingerprint or a CA to start)
+	if [[ $AUTH_MODE == "pki" ]]; then
+		run_cmd "Starting OpenVPN service" systemctl restart openvpn-server@server
+	fi
 
 	if [[ $DNS == "unbound" ]]; then
 		installUnbound
@@ -3207,15 +3315,19 @@ WantedBy=multi-user.target" >/etc/systemd/system/iptables-openvpn.service
 	elif [[ $PROTOCOL == 'tcp6' ]]; then
 		echo "proto tcp6-client" >>/etc/openvpn/server/client-template.txt
 	fi
-	echo "remote $IP $PORT
+	# Common client template options
+	# PKI mode adds remote-cert-tls and verify-x509-name
+	# Fingerprint mode adds peer-fingerprint when generating client config
+	{
+		echo "remote $IP $PORT
 dev tun
 resolv-retry infinite
 nobind
 persist-key
-persist-tun
+persist-tun"
-remote-cert-tls server
+		[[ $AUTH_MODE == "pki" ]] && echo "remote-cert-tls server
-verify-x509-name $SERVER_NAME name
+verify-x509-name $SERVER_NAME name"
-auth $HMAC_ALG
+		echo "auth $HMAC_ALG
 auth-nocache
 cipher $CIPHER
 ignore-unknown-option data-ciphers
@@ -3227,7 +3339,8 @@ tls-cipher $CC_CIPHER
 tls-ciphersuites $TLS13_CIPHERSUITES
 ignore-unknown-option block-outside-dns
 setenv opt block-outside-dns # Prevent Windows 10 DNS leak
-verb 3" >>/etc/openvpn/server/client-template.txt
+verb 3"
+	} >>/etc/openvpn/server/client-template.txt
 
 	if [[ -n $MTU ]]; then
 		echo "tun-mtu $MTU" >>/etc/openvpn/server/client-template.txt
@@ -3235,10 +3348,18 @@ verb 3" >>/etc/openvpn/server/client-template.txt
 
 	# Generate the custom client.ovpn
 	if [[ $NEW_CLIENT == "n" ]]; then
-		log_info "No clients added. To add clients, simply run the script again."
+		if [[ $AUTH_MODE == "fingerprint" ]]; then
+			log_info "No clients added. OpenVPN will not start until you add at least one client."
+		else
+			log_info "No clients added. To add clients, simply run the script again."
+		fi
 	else
 		log_info "Generating first client certificate..."
 		newClient
+		# In fingerprint mode, start service now that we have at least one fingerprint
+		if [[ $AUTH_MODE == "fingerprint" ]]; then
+			run_cmd "Starting OpenVPN service" systemctl restart openvpn-server@server
+		fi
 		log_success "If you want to add more clients, you simply need to run this script another time!"
 	fi
 }
@@ -3333,6 +3454,12 @@ function generateClientConfig() {
 	local client="$1"
 	local filepath="$2"
 
+	# Read auth mode
+	local auth_mode="pki"
+	if [[ -f /etc/openvpn/server/easy-rsa/AUTH_MODE_GENERATED ]]; then
+		auth_mode=$(cat /etc/openvpn/server/easy-rsa/AUTH_MODE_GENERATED)
+	fi
+
 	# Determine if we use tls-crypt-v2, tls-crypt, or tls-auth
 	local tls_sig=""
 	if grep -qs "^tls-crypt-v2" /etc/openvpn/server/server.conf; then
@@ -3346,9 +3473,25 @@ function generateClientConfig() {
 	# Generate the custom client.ovpn
 	run_cmd "Creating client config" cp /etc/openvpn/server/client-template.txt "$filepath"
 	{
-		echo "<ca>"
+		if [[ $auth_mode == "pki" ]]; then
-		cat "/etc/openvpn/server/easy-rsa/pki/ca.crt"
+			# PKI mode: include CA certificate
-		echo "</ca>"
+			echo "<ca>"
+			cat "/etc/openvpn/server/easy-rsa/pki/ca.crt"
+			echo "</ca>"
+		else
+			# Fingerprint mode: use server fingerprint instead of CA
+			local server_fingerprint
+			if [[ ! -f /etc/openvpn/server/server-fingerprint ]]; then
+				log_error "Server fingerprint file not found"
+				exit 1
+			fi
+			server_fingerprint=$(cat /etc/openvpn/server/server-fingerprint)
+			if [[ -z $server_fingerprint ]]; then
+				log_error "Server fingerprint is empty"
+				exit 1
+			fi
+			echo "peer-fingerprint $server_fingerprint"
+		fi
 
 		echo "<cert>"
 		awk '/BEGIN/,/END CERTIFICATE/' "/etc/openvpn/server/easy-rsa/pki/issued/$client.crt"
@@ -3677,45 +3820,96 @@ function newClient() {
 		done
 	fi
 
-	CLIENTEXISTS=$(tail -n +2 /etc/openvpn/server/easy-rsa/pki/index.txt | grep -E "^V" | grep -c -E "/CN=$CLIENT\$")
+	cd /etc/openvpn/server/easy-rsa/ || return
+
+	# Read auth mode
+	if [[ -f AUTH_MODE_GENERATED ]]; then
+		AUTH_MODE=$(cat AUTH_MODE_GENERATED)
+	else
+		AUTH_MODE="pki"
+	fi
+
+	# Check if client already exists
+	if [[ -f pki/index.txt ]]; then
+		CLIENTEXISTS=$(tail -n +2 /etc/openvpn/server/easy-rsa/pki/index.txt | grep -E "^V" | grep -c -E "/CN=$CLIENT\$")
+	else
+		CLIENTEXISTS=0
+	fi
+
 	if [[ $CLIENTEXISTS != '0' ]]; then
 		log_error "The specified client CN was already found in easy-rsa, please choose another name."
 		exit 1
-	else
-		cd /etc/openvpn/server/easy-rsa/ || return
-		log_info "Generating client certificate..."
-		export EASYRSA_CERT_EXPIRE=$CLIENT_CERT_DURATION_DAYS
-		case $PASS in
-		1)
-			run_cmd_fatal "Building client certificate" ./easyrsa --batch build-client-full "$CLIENT" nopass
-			;;
-		2)
-			if [[ -z "$PASSPHRASE" ]]; then
-				log_warn "You will be asked for the client password below"
-				# Run directly (not via run_cmd) so password prompt is visible to user
-				if ! ./easyrsa --batch build-client-full "$CLIENT"; then
-					log_fatal "Building client certificate failed"
-				fi
-			else
-				log_info "Using provided passphrase for client certificate"
-				# Use env var to avoid exposing passphrase in install log
-				export EASYRSA_PASSPHRASE="$PASSPHRASE"
-				run_cmd_fatal "Building client certificate" ./easyrsa --batch --passin=env:EASYRSA_PASSPHRASE --passout=env:EASYRSA_PASSPHRASE build-client-full "$CLIENT"
-				unset EASYRSA_PASSPHRASE
-			fi
-			;;
-		esac
-		log_success "Client $CLIENT added and is valid for $CLIENT_CERT_DURATION_DAYS days."
 	fi
 
+	log_info "Generating client certificate..."
+	export EASYRSA_CERT_EXPIRE=$CLIENT_CERT_DURATION_DAYS
+
+	# Determine easyrsa command based on auth mode
+	local easyrsa_cmd cert_desc
+	if [[ $AUTH_MODE == "pki" ]]; then
+		easyrsa_cmd="build-client-full"
+		cert_desc="client certificate"
+	else
+		easyrsa_cmd="self-sign-client"
+		cert_desc="self-signed client certificate"
+	fi
+
+	case $PASS in
+	1)
+		run_cmd_fatal "Building $cert_desc" ./easyrsa --batch "$easyrsa_cmd" "$CLIENT" nopass
+		;;
+	2)
+		if [[ -z "$PASSPHRASE" ]]; then
+			log_warn "You will be asked for the client password below"
+			if ! ./easyrsa --batch "$easyrsa_cmd" "$CLIENT"; then
+				log_fatal "Building $cert_desc failed"
+			fi
+		else
+			log_info "Using provided passphrase for client certificate"
+			export EASYRSA_PASSPHRASE="$PASSPHRASE"
+			run_cmd_fatal "Building $cert_desc" ./easyrsa --batch --passin=env:EASYRSA_PASSPHRASE --passout=env:EASYRSA_PASSPHRASE "$easyrsa_cmd" "$CLIENT"
+			unset EASYRSA_PASSPHRASE
+		fi
+		;;
+	esac
+
+	# Fingerprint mode: register client fingerprint with server
+	if [[ $AUTH_MODE == "fingerprint" ]]; then
+		CLIENT_FINGERPRINT=$(openssl x509 -in "pki/issued/$CLIENT.crt" -fingerprint -sha256 -noout | cut -d'=' -f2)
+		if [[ -z $CLIENT_FINGERPRINT ]]; then
+			log_error "Failed to extract client certificate fingerprint"
+			exit 1
+		fi
+		log_info "Client fingerprint: $CLIENT_FINGERPRINT"
+
+		# Add fingerprint to server.conf's <peer-fingerprint> block
+		# Create the block if this is the first client
+		if ! grep -q '<peer-fingerprint>' /etc/openvpn/server/server.conf; then
+			echo "# Client fingerprints are listed below
+<peer-fingerprint>
+# $CLIENT
+$CLIENT_FINGERPRINT
+</peer-fingerprint>" >>/etc/openvpn/server/server.conf
+		else
+			# Insert comment and fingerprint before closing tag
+			sed -i "/<\/peer-fingerprint>/i # $CLIENT\n$CLIENT_FINGERPRINT" /etc/openvpn/server/server.conf
+		fi
+
+		# Reload OpenVPN to pick up new fingerprint
+		log_info "Reloading OpenVPN to apply new fingerprint..."
+		if systemctl is-active --quiet openvpn-server@server; then
+			systemctl reload openvpn-server@server 2>/dev/null || systemctl restart openvpn-server@server
+		fi
+	fi
+
+	log_success "Client $CLIENT added and is valid for $CLIENT_CERT_DURATION_DAYS days."
+
 	# Write the .ovpn config file with proper path and permissions
 	writeClientConfig "$CLIENT"
 
 	log_menu ""
 	log_success "The configuration file has been written to $GENERATED_CONFIG_PATH."
 	log_info "Download the .ovpn file and import it in your OpenVPN client."
-
-	exit 0
 }
 
 function revokeClient() {
@@ -3724,13 +3918,45 @@ function revokeClient() {
 	selectClient
 
 	cd /etc/openvpn/server/easy-rsa/ || return
+
+	# Read auth mode
+	local auth_mode="pki"
+	if [[ -f AUTH_MODE_GENERATED ]]; then
+		auth_mode=$(cat AUTH_MODE_GENERATED)
+	fi
+
 	log_info "Revoking certificate for $CLIENT..."
-	run_cmd_fatal "Revoking certificate" ./easyrsa --batch revoke-issued "$CLIENT"
+
-	regenerateCRL
+	if [[ $auth_mode == "pki" ]]; then
+		# PKI mode: use Easy-RSA revocation and CRL
+		run_cmd_fatal "Revoking certificate" ./easyrsa --batch revoke-issued "$CLIENT"
+		regenerateCRL
+		run_cmd "Backing up index" cp /etc/openvpn/server/easy-rsa/pki/index.txt{,.bk}
+	else
+		# Fingerprint mode: remove fingerprint from server.conf and delete cert files
+		log_info "Removing client fingerprint from server configuration..."
+
+		# Remove comment line and fingerprint line below it from server.conf
+		sed -i "/^# $CLIENT\$/{N;d;}" /etc/openvpn/server/server.conf
+
+		# Remove client certificate and key
+		rm -f "pki/issued/$CLIENT.crt" "pki/private/$CLIENT.key"
+
+		# Mark as revoked in index.txt if it exists (for client listing)
+		if [[ -f pki/index.txt ]]; then
+			sed -i "s|^V\(.*\)/CN=$CLIENT\$|R\1/CN=$CLIENT|" pki/index.txt
+		fi
+
+		# Reload OpenVPN to apply fingerprint removal
+		log_info "Reloading OpenVPN to apply fingerprint removal..."
+		if systemctl is-active --quiet openvpn-server@server; then
+			systemctl reload openvpn-server@server 2>/dev/null || systemctl restart openvpn-server@server
+		fi
+	fi
+
 	run_cmd "Removing client config from /home" find /home/ -maxdepth 2 -name "$CLIENT.ovpn" -delete
 	run_cmd "Removing client config from /root" rm -f "/root/$CLIENT.ovpn"
 	run_cmd "Removing IP assignment" sed -i "/^$CLIENT,.*/d" /etc/openvpn/server/ipp.txt
-	run_cmd "Backing up index" cp /etc/openvpn/server/easy-rsa/pki/index.txt{,.bk}
 
 	# Disconnect the client if currently connected
 	disconnectClient "$CLIENT"
@@ -4102,6 +4328,7 @@ function manageMenu() {
 	case $menu_option in
 	1)
 		newClient
+		exit 0
 		;;
 	2)
 		listClients

test/server-entrypoint.sh

@@ -42,6 +42,10 @@ TLS_KEY_FILE="${TLS_KEY_FILE:-tls-crypt-v2.key}"
 TLS_VERSION_MIN="${TLS_VERSION_MIN:-1.2}"
 TLS13_CIPHERSUITES="${TLS13_CIPHERSUITES:-TLS_AES_256_GCM_SHA384:TLS_AES_128_GCM_SHA256:TLS_CHACHA20_POLY1305_SHA256}"
 
+# Authentication mode configuration
+# AUTH_MODE: pki (default, CA-based) or fingerprint (peer-fingerprint, OpenVPN 2.6+)
+AUTH_MODE="${AUTH_MODE:-pki}"
+
 # Build install command with CLI flags (using array for proper quoting)
 INSTALL_CMD=(/opt/openvpn-install.sh install)
 INSTALL_CMD+=(--endpoint openvpn-server)
@@ -75,6 +79,12 @@ if [ "$TLS13_CIPHERSUITES" != "TLS_AES_256_GCM_SHA384:TLS_AES_128_GCM_SHA256:TLS
 	echo "Testing TLS 1.3 ciphersuites: $TLS13_CIPHERSUITES"
 fi
 
+# Add auth mode if non-default
+if [ "$AUTH_MODE" != "pki" ]; then
+	INSTALL_CMD+=(--auth-mode "$AUTH_MODE")
+	echo "Testing authentication mode: $AUTH_MODE"
+fi
+
 echo "Running OpenVPN install script..."
 echo "Command: ${INSTALL_CMD[*]}"
 # Run in subshell because the script calls 'exit 0' after generating client config
@@ -104,16 +114,26 @@ fi
 # Verify all expected files were created
 echo "Verifying installation..."
 MISSING_FILES=0
-# Build list of required files
+# Build list of required files based on auth mode
 REQUIRED_FILES=(
 	/etc/openvpn/server/server.conf
-	/etc/openvpn/server/ca.crt
-	/etc/openvpn/server/ca.key
 	"/etc/openvpn/server/$TLS_KEY_FILE"
-	/etc/openvpn/server/crl.pem
-	/etc/openvpn/server/easy-rsa/pki/ca.crt
 	/root/testclient.ovpn
 )
+if [ "$AUTH_MODE" = "pki" ]; then
+	# PKI mode requires CA and CRL files
+	REQUIRED_FILES+=(
+		/etc/openvpn/server/ca.crt
+		/etc/openvpn/server/ca.key
+		/etc/openvpn/server/crl.pem
+		/etc/openvpn/server/easy-rsa/pki/ca.crt
+	)
+else
+	# Fingerprint mode requires server fingerprint file
+	REQUIRED_FILES+=(
+		/etc/openvpn/server/server-fingerprint
+	)
+fi
 # Only check for iptables script if firewalld and nftables are not active
 if ! systemctl is-active --quiet firewalld && ! systemctl is-active --quiet nftables; then
 	REQUIRED_FILES+=(/etc/iptables/add-openvpn-rules.sh)
@@ -197,13 +217,16 @@ sed -i 's/^remote .*/remote openvpn-server 1194/' /shared/client.ovpn
 echo "Client config copied to /shared/client.ovpn"
 
 # Write VPN network info to shared volume for client tests
-echo "VPN_SUBNET_IPV4=$VPN_SUBNET_IPV4" >/shared/vpn-config.env
+{
-echo "VPN_GATEWAY=$VPN_GATEWAY" >>/shared/vpn-config.env
+	echo "VPN_SUBNET_IPV4=$VPN_SUBNET_IPV4"
-echo "CLIENT_IPV6=$CLIENT_IPV6" >>/shared/vpn-config.env
+	echo "VPN_GATEWAY=$VPN_GATEWAY"
-if [ "$CLIENT_IPV6" = "y" ]; then
+	echo "CLIENT_IPV6=$CLIENT_IPV6"
-	echo "VPN_SUBNET_IPV6=$VPN_SUBNET_IPV6" >>/shared/vpn-config.env
+	echo "AUTH_MODE=$AUTH_MODE"
-	echo "VPN_GATEWAY_IPV6=$VPN_GATEWAY_IPV6" >>/shared/vpn-config.env
+	if [ "$CLIENT_IPV6" = "y" ]; then
-fi
+		echo "VPN_SUBNET_IPV6=$VPN_SUBNET_IPV6"
+		echo "VPN_GATEWAY_IPV6=$VPN_GATEWAY_IPV6"
+	fi
+} >/shared/vpn-config.env
 echo "VPN config written to /shared/vpn-config.env"
 
 # =====================================================
@@ -396,12 +419,14 @@ else
 	exit 1
 fi
 
-# Verify CRL was updated
+# Verify CRL was updated (PKI mode only)
-if [ -f /etc/openvpn/server/crl.pem ]; then
+if [ "$AUTH_MODE" = "pki" ]; then
-	echo "PASS: CRL file exists"
+	if [ -f /etc/openvpn/server/crl.pem ]; then
-else
+		echo "PASS: CRL file exists"
-	echo "FAIL: CRL file missing after renewal"
+	else
-	exit 1
+		echo "FAIL: CRL file missing after renewal"
+		exit 1
+	fi
 fi
 
 # Update shared client config with renewed certificate
@@ -815,13 +840,25 @@ else
 	exit 1
 fi
 
-# Verify certificate is marked as revoked in index.txt
+# Verify revocation was applied correctly
-if tail -n +2 /etc/openvpn/server/easy-rsa/pki/index.txt | grep -q "^R.*CN=$REVOKE_CLIENT\$"; then
+if [ "$AUTH_MODE" = "pki" ]; then
-	echo "PASS: Certificate marked as revoked in index.txt"
+	# PKI mode: verify certificate is marked as revoked in index.txt
+	if tail -n +2 /etc/openvpn/server/easy-rsa/pki/index.txt | grep -q "^R.*CN=$REVOKE_CLIENT\$"; then
+		echo "PASS: Certificate marked as revoked in index.txt"
+	else
+		echo "FAIL: Certificate not marked as revoked"
+		cat /etc/openvpn/server/easy-rsa/pki/index.txt
+		exit 1
+	fi
 else
-	echo "FAIL: Certificate not marked as revoked"
+	# Fingerprint mode: verify fingerprint was removed from server.conf
-	cat /etc/openvpn/server/easy-rsa/pki/index.txt
+	if ! grep -q "# $REVOKE_CLIENT\$" /etc/openvpn/server/server.conf; then
-	exit 1
+		echo "PASS: Client fingerprint removed from server.conf"
+	else
+		echo "FAIL: Client fingerprint still present in server.conf"
+		grep "$REVOKE_CLIENT" /etc/openvpn/server/server.conf || true
+		exit 1
+	fi
 fi
 
 # Wait for client to confirm it was disconnected by the revoke
@@ -883,13 +920,26 @@ else
 	exit 1
 fi
 
-# Verify certificate count (3 certs: testclient valid, testclient revoked from renewal, revoketest revoked)
+# Verify certificate count (varies by auth mode)
-if grep -q "Found 3 client certificate(s)" "$LIST_OUTPUT"; then
+if [ "$AUTH_MODE" = "pki" ]; then
-	echo "PASS: List shows correct certificate count"
+	# PKI mode: 3 certs (testclient valid, testclient revoked from renewal, revoketest revoked)
+	if grep -q "Found 3 client certificate(s)" "$LIST_OUTPUT"; then
+		echo "PASS: List shows correct certificate count"
+	else
+		echo "FAIL: List does not show correct certificate count"
+		cat "$LIST_OUTPUT"
+		exit 1
+	fi
 else
-	echo "FAIL: List does not show correct certificate count"
+	# Fingerprint mode: 2 certs (testclient valid, revoketest revoked)
-	cat "$LIST_OUTPUT"
+	# In fingerprint mode, renewal doesn't create a separate revoked entry
-	exit 1
+	if grep -q "Found [23] client certificate(s)" "$LIST_OUTPUT"; then
+		echo "PASS: List shows correct certificate count for fingerprint mode"
+	else
+		echo "FAIL: List does not show correct certificate count"
+		cat "$LIST_OUTPUT"
+		exit 1
+	fi
 fi
 
 # Test JSON output
@@ -906,14 +956,25 @@ else
 	exit 1
 fi
 
-# Verify client count in JSON
+# Verify client count in JSON (varies by auth mode)
 JSON_CLIENT_COUNT=$(jq '.clients | length' "$LIST_JSON_OUTPUT")
-if [ "$JSON_CLIENT_COUNT" -eq 3 ]; then
+if [ "$AUTH_MODE" = "pki" ]; then
-	echo "PASS: Client list JSON has correct count ($JSON_CLIENT_COUNT)"
+	if [ "$JSON_CLIENT_COUNT" -eq 3 ]; then
+		echo "PASS: Client list JSON has correct count ($JSON_CLIENT_COUNT)"
+	else
+		echo "FAIL: Client list JSON has wrong count: $JSON_CLIENT_COUNT (expected 3)"
+		cat "$LIST_JSON_OUTPUT"
+		exit 1
+	fi
 else
-	echo "FAIL: Client list JSON has wrong count: $JSON_CLIENT_COUNT (expected 3)"
+	# Fingerprint mode may have fewer entries
-	cat "$LIST_JSON_OUTPUT"
+	if [ "$JSON_CLIENT_COUNT" -ge 2 ] && [ "$JSON_CLIENT_COUNT" -le 3 ]; then
-	exit 1
+		echo "PASS: Client list JSON has correct count for fingerprint mode ($JSON_CLIENT_COUNT)"
+	else
+		echo "FAIL: Client list JSON has wrong count: $JSON_CLIENT_COUNT (expected 2-3)"
+		cat "$LIST_JSON_OUTPUT"
+		exit 1
+	fi
 fi
 
 # Verify valid client in JSON
@@ -955,25 +1016,37 @@ else
 	exit 1
 fi
 
-# Verify the new certificate is valid (V) in index.txt
+# Verify the new certificate is valid
-if tail -n +2 /etc/openvpn/server/easy-rsa/pki/index.txt | grep -q "^V.*CN=$REVOKE_CLIENT\$"; then
+if [ "$AUTH_MODE" = "pki" ]; then
-	echo "PASS: New certificate is valid in index.txt"
+	# PKI mode: verify in index.txt
-else
+	if tail -n +2 /etc/openvpn/server/easy-rsa/pki/index.txt | grep -q "^V.*CN=$REVOKE_CLIENT\$"; then
-	echo "FAIL: New certificate not marked as valid"
+		echo "PASS: New certificate is valid in index.txt"
-	cat /etc/openvpn/server/easy-rsa/pki/index.txt
+	else
-	exit 1
+		echo "FAIL: New certificate not marked as valid"
-fi
+		cat /etc/openvpn/server/easy-rsa/pki/index.txt
+		exit 1
+	fi
 
-# Verify there's also a revoked entry (both should exist)
+	# Verify there's also a revoked entry (both should exist)
-REVOKED_COUNT=$(tail -n +2 /etc/openvpn/server/easy-rsa/pki/index.txt | grep -c "^R.*CN=$REVOKE_CLIENT\$")
+	REVOKED_COUNT=$(tail -n +2 /etc/openvpn/server/easy-rsa/pki/index.txt | grep -c "^R.*CN=$REVOKE_CLIENT\$")
-VALID_COUNT=$(tail -n +2 /etc/openvpn/server/easy-rsa/pki/index.txt | grep -c "^V.*CN=$REVOKE_CLIENT\$")
+	VALID_COUNT=$(tail -n +2 /etc/openvpn/server/easy-rsa/pki/index.txt | grep -c "^V.*CN=$REVOKE_CLIENT\$")
-echo "Certificates for '$REVOKE_CLIENT': $REVOKED_COUNT revoked, $VALID_COUNT valid"
+	echo "Certificates for '$REVOKE_CLIENT': $REVOKED_COUNT revoked, $VALID_COUNT valid"
-if [ "$REVOKED_COUNT" -ge 1 ] && [ "$VALID_COUNT" -eq 1 ]; then
+	if [ "$REVOKED_COUNT" -ge 1 ] && [ "$VALID_COUNT" -eq 1 ]; then
-	echo "PASS: Both revoked and new valid certificate entries exist"
+		echo "PASS: Both revoked and new valid certificate entries exist"
+	else
+		echo "FAIL: Unexpected certificate state"
+		cat /etc/openvpn/server/easy-rsa/pki/index.txt
+		exit 1
+	fi
 else
-	echo "FAIL: Unexpected certificate state"
+	# Fingerprint mode: verify fingerprint was added back to server.conf
-	cat /etc/openvpn/server/easy-rsa/pki/index.txt
+	if grep -q "# $REVOKE_CLIENT\$" /etc/openvpn/server/server.conf; then
-	exit 1
+		echo "PASS: New client fingerprint added to server.conf"
+	else
+		echo "FAIL: New client fingerprint not found in server.conf"
+		cat /etc/openvpn/server/server.conf | grep -A5 "<peer-fingerprint>" || true
+		exit 1
+	fi
 fi
 
 # Copy the new config