In today’s digital landscape, ensuring the security of your web applications is paramount. One critical aspect of this security is the management of SSL/TLS certificates. Expired certificates can lead to service disruptions and can compromise the trustworthiness of your applications. To prevent such scenarios, it’s essential to have a robust monitoring system in place. Prometheus, a leading open-source monitoring solution, can be effectively used to track SSL certificate expiry dates and alert you before they expire.
Why Monitor SSL Certificates?
SSL certificates are crucial for encrypting data between clients and servers. However, they come with an expiration date, and if not renewed in time, they can lead to:
- Service Downtime: Users may be unable to access your services.
- Security Risks: Expired certificates can be exploited by attackers.
- Loss of Trust: Users may lose confidence in your service’s security.
Setting Up Prometheus for SSL Monitoring
To monitor SSL certificates with Prometheus, you can use the blackbox_exporter, a Prometheus exporter that allows probing of endpoints over HTTP, HTTPS, DNS, TCP, ICMP, and more. Here’s a step-by-step guide to setting it up:
Step 1: Install Blackbox Exporter
First, download and install the Blackbox Exporter. You can find the latest release on GitHub.
wget https://github.com/prometheus/blackbox_exporter/releases/download/v0.21.0/blackbox_exporter-0.21.0.linux-amd64.tar.gz
tar xvfz blackbox_exporter-0.21.0.linux-amd64.tar.gz
cd blackbox_exporter-0.21.0.linux-amd64
./blackbox_exporter
Step 2: Configure Blackbox Exporter
Create a configuration file blackbox.yml for the Blackbox Exporter. This file will define how the exporter probes your endpoints.
modules:
http_2xx:
prober: http
timeout: 5s
http:
valid_http_versions: [ "HTTP/1.1", "HTTP/2" ]
valid_status_codes: [] # Defaults to 2xx
method: GET
fail_if_ssl: false
fail_if_not_ssl: false
tls_config:
insecure_skip_verify: false
ssl_cert:
prober: http
timeout: 5s
http:
fail_if_ssl: false
fail_if_not_ssl: false
tls_config:
insecure_skip_verify: false
preferred_ip_protocol: "ip4"
Step 3: Configure Prometheus
Next, configure Prometheus to scrape metrics from the Blackbox Exporter. Add the following job to your prometheus.yml configuration file:
scrape_configs:
- job_name: 'blackbox'
metrics_path: /probe
params:
module: [ssl_cert] # Use the 'ssl_cert' module
static_configs:
- targets:
- https://yourdomain.com # Replace with your domain
relabel_configs:
- source_labels: [__address__]
target_label: __param_target
- source_labels: [__param_target]
target_label: instance
- target_label: __address__
replacement: 127.0.0.1:9115 # Blackbox Exporter's address
Step 4: Set Up Alerts
To ensure you are notified before a certificate expires, set up alerting rules in Prometheus. Create a file alert_rules.yml:
groups:
- name: ssl_cert_expiry
rules:
- alert: SSLCertificateExpiry
expr: probe_ssl_earliest_cert_expiry - time() < 86400 * 30
for: 10m
labels:
severity: warning
annotations:
summary: "SSL Certificate for {{ $labels.instance }} is expiring soon"
description: "The SSL certificate for {{ $labels.instance }} will expire in less than 30 days."
Include this alerting rule in your Prometheus configuration:
rule_files:
- "alert_rules.yml"
Step 5: Test Your Setup
Restart both the Blackbox Exporter and Prometheus to apply the new configurations. Verify that Prometheus is scraping the metrics and that alerts are firing as expected when certificates are nearing expiration.
Conclusion
By integrating Prometheus with the Blackbox Exporter, you can effectively monitor SSL certificate expiry dates and ensure timely renewals. This setup not only helps in maintaining service uptime but also enhances the security posture of your applications. With the right alerting mechanisms in place, you can proactively manage SSL certificates and avoid potential disruptions.