Prepare to use TLS in local dev

.gitignore

@@ -21,3 +21,7 @@
 # Go workspace file
 go.work
 
+# Certs
+*.crt
+*.key
+*.csr

.mosquitto/.gitignore

@@ -1 +1,4 @@
 passwd
+*.crt
+*.key
+*.csr

Makefile

@@ -1,3 +1,15 @@
+check-deps:
+	@echo "Checking system dependencies..."
+	@command -v openssl > /dev/null || (echo "OpenSSL cli is not installed."; exit 1)
+	@echo "System dependencies met."
+.PHONEY: check-deps
+
+# https://mosquitto.org/man/mosquitto-tls-7.html
+# FOR LOCAL DEV ONLY! These certs do not use encryption. Use let's encrypt or a real cert.
+gen-local-tls:
+	./scripts/gen-local-tls-certs.sh
+.PHONEY: gen-local-tls
+
 start-dev:
 	docker compose up -d
 .PHONEY: start-dev

README.md

@@ -5,7 +5,7 @@ Learning MQTT with Golang by doing. This repo is a simple example of using a Gol
 
 ## Development
 
-Start the local development environment with:
+For local development we use [Mosquitto](https://mosquitto.org/). Start the local development environment with:
 
 ```
 make start-dev

scripts/gen-local-tls-certs.sh

@@ -0,0 +1,68 @@
+#!/usr/bin/env bash
+
+# https://mosquitto.org/man/mosquitto-tls-7.html
+set -euo pipefail
+
+# Set working directory to project root
+cd "$(dirname "$0")/../"
+CDIR=$(pwd -P)
+export CDIR
+
+MOSQUITTO_CERTS_DIR="${CDIR}/.mosquitto/certs"
+TLS_CERT_DURATION="${TLS_CERT_DURATION:-365}"
+CA_COMMON_NAME="${CA_COMMON_NAME:-runcible.io}"
+HOSTNAME=$(hostname)
+
+warn(){
+    echo -e "\nFOR LOCAL DEVELOPMENT ONLY!!! These certs do not follow best practices.\n\
+Keys are not encypted! Seriously, don't use this for anything other than local development.\n"
+}
+
+generate_ca_cert(){
+    echo "Generating CA key in ${MOSQUITTO_CERTS_DIR}..."
+    openssl genpkey -algorithm RSA -out "${MOSQUITTO_CERTS_DIR}/ca.key"
+
+    echo "Generating CA cert..."
+    openssl req -x509 -new -nodes -key "${MOSQUITTO_CERTS_DIR}/ca.key" -sha256 -days "${TLS_CERT_DURATION}" \
+    -extensions v3_ca -out "${MOSQUITTO_CERTS_DIR}/ca.crt" -subj "/C=US/O=Runcible/CN=${CA_COMMON_NAME}"
+    
+    echo "CA cert generation complete."
+}
+
+generate_server_cert(){
+    echo "Generating server key..."
+    openssl genrsa -out "${MOSQUITTO_CERTS_DIR}/server.key" 2048
+    
+    echo "Generating cert signing request for CA..."
+    openssl req -out "${MOSQUITTO_CERTS_DIR}/server.csr" -key "${MOSQUITTO_CERTS_DIR}/server.key" -new \
+    -subj "/C=US/O=Runcible/CN=${HOSTNAME}"
+    
+    echo "Sending server CSR to CA..."
+    openssl x509 -req -in "${MOSQUITTO_CERTS_DIR}/server.csr" -CA "${MOSQUITTO_CERTS_DIR}/ca.crt" \
+    -CAkey "${MOSQUITTO_CERTS_DIR}/ca.key" -CAcreateserial -out "${MOSQUITTO_CERTS_DIR}/server.crt" \
+    -days "${TLS_CERT_DURATION}"
+    
+    echo "Server cert generation complete."
+}
+
+generate_client_cert(){
+    echo "Creating client cert in $CDIR"
+    echo "Generating client key..."
+    openssl genrsa -out "${CDIR}/client.key" 2048
+
+    echo "Generating client CSR for CA..."
+    openssl req -out "${CDIR}/client.csr" -key "${CDIR}/client.key" -new -subj "/C=US/O=Runcible/CN=localhost"
+
+    echo "Sending client CSR to CA..."
+    openssl x509 -req -in "${CDIR}/client.csr" -CA "${MOSQUITTO_CERTS_DIR}/ca.crt" -CAkey "${MOSQUITTO_CERTS_DIR}/ca.key" \
+    -CAcreateserial -out "${CDIR}/client.crt" -days "${TLS_CERT_DURATION}"
+
+    echo "Client cert generation complete."
+}
+
+
+warn
+generate_ca_cert
+generate_server_cert
+generate_client_cert
+warn