feat: disconnect clients immediately on certificate revocation (#1432)

## Summary

Adds immediate client disconnect when a certificate is revoked, via
OpenVPN management interface.

Previously, revoked clients stayed connected until they voluntarily
disconnected or the server restarted.

Fixes #1199

## Changes

- Enable management interface (Unix socket at
`/var/run/openvpn/server.sock`)
- Add `disconnectClient()` function to send `kill` command on revoke
- Add `socat` dependency for socket communication

README.md

@@ -41,6 +41,7 @@ That said, OpenVPN still makes sense when you need:
 - CLI interface for automation and scripting (non-interactive mode with JSON output)
 - Certificate renewal for both client and server certificates
 - List and monitor connected clients
+- Immediate client disconnect on certificate revocation (via management interface)
 - Uses [official OpenVPN repositories](https://community.openvpn.net/openvpn/wiki/OpenvpnSoftwareRepos) when possible for the latest stable releases
 - Firewall rules and forwarding managed seamlessly (native firewalld and nftables support, iptables fallback)
 - Configurable VPN subnets (IPv4: default `10.8.0.0/24`, IPv6: default `fd42:42:42:42::/112`)
@@ -135,7 +136,7 @@ For automation and scripting, use the CLI interface:
 # List clients
 ./openvpn-install.sh client list
 
-# Revoke a client
+# Revoke a client (immediately disconnects if connected)
 ./openvpn-install.sh client revoke alice
 ```
 

openvpn-install.sh

@@ -2574,20 +2574,21 @@ function installOpenVPN() {
 		installOpenVPNRepo
 
 		log_info "Installing OpenVPN and dependencies..."
+		# socat is used for communicating with the OpenVPN management interface (client disconnect on revoke)
 		if [[ $OS =~ (debian|ubuntu) ]]; then
-			run_cmd_fatal "Installing OpenVPN" apt-get install -y openvpn iptables openssl curl ca-certificates tar dnsutils
+			run_cmd_fatal "Installing OpenVPN" apt-get install -y openvpn iptables openssl curl ca-certificates tar dnsutils socat
 		elif [[ $OS == 'centos' ]]; then
-			run_cmd_fatal "Installing OpenVPN" yum install -y openvpn iptables openssl ca-certificates curl tar bind-utils 'policycoreutils-python*'
+			run_cmd_fatal "Installing OpenVPN" yum install -y openvpn iptables openssl ca-certificates curl tar bind-utils socat 'policycoreutils-python*'
 		elif [[ $OS == 'oracle' ]]; then
-			run_cmd_fatal "Installing OpenVPN" yum install -y openvpn iptables openssl ca-certificates curl tar bind-utils policycoreutils-python-utils
+			run_cmd_fatal "Installing OpenVPN" yum install -y openvpn iptables openssl ca-certificates curl tar bind-utils socat policycoreutils-python-utils
 		elif [[ $OS == 'amzn2023' ]]; then
-			run_cmd_fatal "Installing OpenVPN" dnf install -y openvpn iptables openssl ca-certificates curl tar bind-utils
+			run_cmd_fatal "Installing OpenVPN" dnf install -y openvpn iptables openssl ca-certificates curl tar bind-utils socat
 		elif [[ $OS == 'fedora' ]]; then
-			run_cmd_fatal "Installing OpenVPN" dnf install -y openvpn iptables openssl ca-certificates curl tar bind-utils policycoreutils-python-utils
+			run_cmd_fatal "Installing OpenVPN" dnf install -y openvpn iptables openssl ca-certificates curl tar bind-utils socat policycoreutils-python-utils
 		elif [[ $OS == 'opensuse' ]]; then
-			run_cmd_fatal "Installing OpenVPN" zypper install -y openvpn iptables openssl ca-certificates curl tar bind-utils
+			run_cmd_fatal "Installing OpenVPN" zypper install -y openvpn iptables openssl ca-certificates curl tar bind-utils socat
 		elif [[ $OS == 'arch' ]]; then
-			run_cmd_fatal "Installing OpenVPN" pacman --needed --noconfirm -Syu openvpn iptables openssl ca-certificates curl tar bind
+			run_cmd_fatal "Installing OpenVPN" pacman --needed --noconfirm -Syu openvpn iptables openssl ca-certificates curl tar bind socat
 		fi
 
 		# Verify ChaCha20-Poly1305 compatibility if selected
@@ -2946,8 +2947,12 @@ 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
 
+	# Create management socket directory
+	run_cmd_fatal "Creating management socket directory" mkdir -p /var/run/openvpn
+
 	# Create client-config-dir dir
 	run_cmd_fatal "Creating client config directory" mkdir -p /etc/openvpn/server/ccd
 	# Create log dir
@@ -3727,9 +3732,30 @@ function revokeClient() {
 	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"
+
 	log_success "Certificate for client $CLIENT revoked."
 }
 
+# Disconnect a client via the management interface
+function disconnectClient() {
+	local client_name="$1"
+	local mgmt_socket="/var/run/openvpn/server.sock"
+
+	if [[ ! -S "$mgmt_socket" ]]; then
+		log_warning "Management socket not found. Client may still be connected until they reconnect."
+		return 0
+	fi
+
+	log_info "Disconnecting client $client_name..."
+	if echo "kill $client_name" | socat - UNIX-CONNECT:"$mgmt_socket" >/dev/null 2>&1; then
+		log_success "Client $client_name disconnected."
+	else
+		log_warning "Could not disconnect client (they may not be connected)."
+	fi
+}
+
 function renewClient() {
 	local client_cert_duration_days
 

test/Dockerfile.server

@@ -15,6 +15,7 @@ ENV ENABLE_NFTABLES=${ENABLE_NFTABLES}
 
 # Install basic dependencies based on the OS
 # dnsutils/bind-utils provides dig for DNS testing with Unbound
+# Note: socat is installed by openvpn-install.sh during OpenVPN installation
 RUN if command -v apt-get >/dev/null; then \
         apt-get update && apt-get install -y --no-install-recommends \
             iproute2 iptables curl procps systemd systemd-sysv dnsutils jq \

test/client-entrypoint.sh

@@ -192,36 +192,35 @@ echo "PASS: Can ping VPN gateway with revoke test client"
 # Signal server that we're connected with revoke test client
 touch /shared/revoke-client-connected
 
-# Wait for server to signal us to disconnect
-echo "Waiting for server to signal disconnect..."
-while [ ! -f /shared/revoke-client-disconnect ]; do
-	sleep 2
-done
-
-# Disconnect
-echo "Disconnecting revoke test client..."
-pkill openvpn || true
-
-# Wait for openvpn to fully exit and tun0 to be released
-WAITED=0
-MAX_WAIT_DISCONNECT=10
-while (pgrep openvpn >/dev/null || ip addr show tun0 2>/dev/null | grep -q "inet ") && [ $WAITED -lt $MAX_WAIT_DISCONNECT ]; do
+# Wait for server to revoke and auto-disconnect us via management interface
+# We detect disconnect by checking if ping to VPN gateway fails
+echo "Waiting for server to revoke certificate and disconnect us..."
+DISCONNECT_DETECTED=false
+for i in $(seq 1 60); do
+	if ! ping -c 1 -W 2 "$VPN_GATEWAY" >/dev/null 2>&1; then
+		echo "Disconnect detected: cannot ping VPN gateway"
+		DISCONNECT_DETECTED=true
+		break
+	fi
 	sleep 1
-	WAITED=$((WAITED + 1))
+	echo "Still connected, waiting for revoke/disconnect ($i/60)..."
 done
 
-# Verify disconnected
-if ip addr show tun0 2>/dev/null | grep -q "inet "; then
-	echo "FAIL: tun0 still has IP after disconnect"
+if [ "$DISCONNECT_DETECTED" = true ]; then
+	echo "PASS: Client was auto-disconnected by revoke"
+	# Kill openvpn process to clean up
+	pkill openvpn 2>/dev/null || true
+	sleep 1
+else
+	echo "FAIL: Client was not disconnected within 60 seconds"
 	exit 1
 fi
-echo "PASS: Disconnected successfully"
 
-# Signal server that we're disconnected
+# Signal server that we detected the disconnect
 touch /shared/revoke-client-disconnected
 
-# Wait for server to revoke the certificate and signal us to reconnect
-echo "Waiting for server to revoke certificate and signal reconnect..."
+# Wait for server to signal us to try reconnecting
+echo "Waiting for server to signal reconnect attempt..."
 while [ ! -f /shared/revoke-try-reconnect ]; do
 	sleep 2
 done

test/server-entrypoint.sh

@@ -135,6 +135,39 @@ fi
 
 echo "All required files present"
 
+# =====================================================
+# Verify management interface configuration
+# =====================================================
+echo ""
+echo "=== Verifying Management Interface Configuration ==="
+
+# Verify management socket is configured in server.conf
+if grep -q "management /var/run/openvpn/server.sock unix" /etc/openvpn/server/server.conf; then
+	echo "PASS: Management interface configured in server.conf"
+else
+	echo "FAIL: Management interface not found in server.conf"
+	grep "management" /etc/openvpn/server/server.conf || echo "No management directive found"
+	exit 1
+fi
+
+# Verify management socket directory exists
+if [ -d /var/run/openvpn ]; then
+	echo "PASS: Management socket directory exists"
+else
+	echo "FAIL: Management socket directory /var/run/openvpn not found"
+	exit 1
+fi
+
+# Verify socat is available (needed for management interface communication)
+if command -v socat >/dev/null 2>&1; then
+	echo "PASS: socat is available"
+else
+	echo "FAIL: socat is not installed (required for management interface)"
+	exit 1
+fi
+
+echo "=== Management Interface Configuration Verified ==="
+
 # =====================================================
 # Test duplicate client name handling
 # =====================================================
@@ -769,18 +802,8 @@ fi
 
 echo "=== Server Status Tests PASSED ==="
 
-# Signal client to disconnect before revocation
-touch /shared/revoke-client-disconnect
-
-# Wait for client to disconnect
-echo "Waiting for client to disconnect..."
-while [ ! -f /shared/revoke-client-disconnected ]; do
-	sleep 2
-done
-echo "Client disconnected"
-
-# Now revoke the certificate
-echo "Revoking certificate for '$REVOKE_CLIENT'..."
+# Now revoke the certificate (this should auto-disconnect the client via management interface)
+echo "Revoking certificate for '$REVOKE_CLIENT' (should auto-disconnect client)..."
 REVOKE_OUTPUT="/tmp/revoke-output.log"
 (bash /opt/openvpn-install.sh client revoke "$REVOKE_CLIENT" --force) 2>&1 | tee "$REVOKE_OUTPUT" || true
 
@@ -801,6 +824,22 @@ else
 	exit 1
 fi
 
+# Wait for client to confirm it was disconnected by the revoke
+echo "Waiting for client to confirm auto-disconnect..."
+DISCONNECT_WAIT=0
+while [ ! -f /shared/revoke-client-disconnected ] && [ $DISCONNECT_WAIT -lt 60 ]; do
+	sleep 2
+	DISCONNECT_WAIT=$((DISCONNECT_WAIT + 2))
+	echo "Waiting for disconnect confirmation... ($DISCONNECT_WAIT/60s)"
+done
+
+if [ -f /shared/revoke-client-disconnected ]; then
+	echo "PASS: Client was auto-disconnected by revoke command"
+else
+	echo "FAIL: Client was not disconnected within 60 seconds"
+	exit 1
+fi
+
 # Signal client to try reconnecting (should fail)
 touch /shared/revoke-try-reconnect
 
@@ -1025,8 +1064,41 @@ done
 echo "PASS: Client connected with passphrase-protected certificate"
 
 echo "=== PASSPHRASE Support Tests PASSED ==="
+
+# =====================================================
+# Test management interface is running
+# =====================================================
 echo ""
-echo "=== All Revocation Tests PASSED ==="
+echo "=== Testing Management Interface ==="
+
+MGMT_SOCKET="/var/run/openvpn/server.sock"
+
+# Verify management socket exists and is accessible
+if [ -S "$MGMT_SOCKET" ]; then
+	echo "PASS: Management socket exists at $MGMT_SOCKET"
+else
+	echo "FAIL: Management socket not found at $MGMT_SOCKET"
+	ls -la /var/run/openvpn/ || true
+	exit 1
+fi
+
+# Test that we can communicate with the management interface
+echo "Testing management interface communication..."
+MGMT_STATUS=$(echo "status" | socat - UNIX-CONNECT:"$MGMT_SOCKET" 2>&1 | head -20)
+if echo "$MGMT_STATUS" | grep -q "CLIENT LIST"; then
+	echo "PASS: Management interface is responsive"
+	echo "Status output:"
+	echo "$MGMT_STATUS"
+else
+	echo "FAIL: Management interface not responding correctly"
+	echo "Response: $MGMT_STATUS"
+	exit 1
+fi
+
+echo "=== Management Interface Tests PASSED ==="
+
+echo ""
+echo "=== All Tests PASSED ==="
 
 # Server tests complete - systemd keeps the container running via /sbin/init
 # OpenVPN service (openvpn-server@server) continues independently