# SSL Certificate Exporter The [blackbox_exporter](https://github.com/prometheus/blackbox_exporter) allows you to test the expiry date of a certificate as part of its HTTP(S) probe - which is great. It doesn't, however, tell you which certificate in the chain is nearing expiry or give you any other information that might be useful when sending alerts. For instance, there's a definite value in knowing, upon first receiving an alert, if it's a certificate you manage directly or one further up the chain. It's also not always necessarily clear from the address you're polling what kind of certificate renewal you're looking at. Is it a Let's Encrypt, in which case it should be handled by automation? Or your organisation's wildcard? Maybe the domain is managed by a third-party and you need to submit a ticket to get it renewed. Whatever it is, the SSL exporter gives you visibility over those dimensions at the point at which you receive an alert. It also allows you to produce more meaningful visualisations and consoles. ## Table of Contents - [SSL Certificate Exporter](#ssl-certificate-exporter) - [Building](#building) - [Docker](#docker) - [Flags](#flags) - [Metrics](#metrics) - [Prometheus](#prometheus) - [Configuration](#configuration) - [Targets](#targets) - [Valid targets](#valid-targets) - [Invalid targets](#invalid-targets) - [Example Queries](#example-queries) - [Client authentication](#client-authentication) - [Proxying](#proxying) - [Limitations](#limitations) - [Acknowledgements](#acknowledgements) Created by [gh-md-toc](https://github.com/ekalinin/github-markdown-toc) ## Building make ./ssl_exporter Similarly to the blackbox_exporter, visiting [http://localhost:9219/probe?target=example.com:443](http://localhost:9219/probe?target=example.com:443) will return certificate metrics for example.com. The `ssl_tls_connect_success` metric indicates if the probe has been successful. ### Docker docker pull ribbybibby/ssl-exporter docker run -p 9219:9219 ribbybibby/ssl-exporter:latest ### Release process - Update the `VERSION` file in this repository and commit to master - [This github action](.github/workflows/release.yaml) will add a changelog and upload binaries in response to a release being created in Github - Dockerhub will build and tag a new container image in response to tags of the format `/^v[0-9.]+$/` ## Flags ./ssl_exporter --help - **`--tls.insecure`:** Skip certificate verification (default false). This is insecure but does allow you to collect metrics in the case where a certificate has expired. That being said, I feel that it's more important to catch verification failures than it is to identify an expired certificate, especially as the former includes the latter. - **`--tls.cacert`:** Provide the path to an alternative bundle of root CA certificates. By default the exporter will use the host's root CA set. - **`--tls.client-auth`:** Enable client authentication (default false). When enabled the exporter will present the certificate and key configured by `--tls.cert` and `tls.key` to the other side of the connection. - **`--tls.cert`:** The path to a local certificate for client authentication (default "cert.pem"). Only used when `--tls.client-auth` is toggled on. - **`--tls.key`:** The path to a local key for client authentication (default "key.pem"). Only used when `--tls.client-auth` is toggled on. - **`--web.listen-address`:** The port (default ":9219"). - **`--web.metrics-path`:** The path metrics are exposed under (default "/metrics") - **`--web.probe-path`:** The path the probe endpoint is exposed under (default "/probe") ## Metrics | Metric | Meaning | Labels | | ----------------------- | ----------------------------------------------------------------------------------- | --------------------------------------------------- | | ssl_cert_not_after | The date after which the certificate expires. Expressed as a Unix Epoch Time. | serial_no, issuer_cn, cn, dnsnames, ips, emails, ou | | ssl_cert_not_before | The date before which the certificate is not valid. Expressed as a Unix Epoch Time. | serial_no, issuer_cn, cn, dnsnames, ips, emails, ou | | ssl_client_protocol | The protocol used by the exporter to connect to the target. Boolean. | protocol | | ssl_tls_connect_success | Was the TLS connection successful? Boolean. | | | ssl_tls_version_info | The TLS version used. Always 1. | version | ## Prometheus ### Configuration Just like with the blackbox_exporter, you should pass the targets to a single instance of the exporter in a scrape config with a clever bit of relabelling. This allows you to leverage service discovery and keeps configuration centralised to your Prometheus config. ```yml scrape_configs: - job_name: "ssl" metrics_path: /probe static_configs: - targets: - example.com:443 - prometheus.io:443 relabel_configs: - source_labels: [__address__] target_label: __param_target - source_labels: [__param_target] target_label: instance - target_label: __address__ replacement: 127.0.0.1:9219 # SSL exporter. ``` ### Targets The exporter uses the provided uri to decide which client (http or tcp) to use when connecting to the target. The uri must contain either a protocol scheme (`https://`), a port (`:443`), or both (`https://example.com:443`). If the `https://` scheme is provided then the exporter will use a http client to connect to the target. This allows you to take advantage of some features not available when using tcp, like host-based proxying. The exporter doesn't understand any other L7 protocols, so it will produce an error for others, like `ldaps://` or `ftps://`. If there's only a port, then a tcp client is used to make the TLS connection. This should allow you to connect to any TLS target, regardless of L7 protocol. If neither are given, the exporter assumes a https connection on port `443` (the most common case). #### Valid targets - `https://example.com` - `https://example.com:443` - `example.com:443` - `example.com:636` - `example.com` #### Invalid targets - `ldaps://example.com` - `ldaps://example.com:636` ### Example Queries Certificates that expire within 7 days: ``` ssl_cert_not_after - time() < 86400 * 7 ``` Wildcard certificates that are expiring: ``` ssl_cert_not_after{cn=~"\*.*"} - time() < 86400 * 7 ``` Number of certificates in the chain: ``` count(ssl_cert_not_after) by (instance, serial_no, issuer_cn) ``` Identify instances that have failed to create a valid SSL connection: ``` ssl_tls_connect_success == 0 ``` ## Client authentication The exporter optionally supports client authentication, which can be toggled on by providing the `--tls.client-auth` flag. By default, it will use the host system's root CA bundle and attempt to use `./cert.pem` and `./key.pem` as the client certificate and key, respectively. You can override these defaults with `--tls.cacert`, `--tls.cert` and `--tls.key`. If you do enable client authentication, keep in mind that the certificate will be passed to all targets, even those that don't necessarily require client authentication. I'm not sure what the implications of that are but I think you'd probably want to avoid passing a certificate to an unrelated server. Also, if you want to scrape targets with different client certificate requirements, you'll need to run different instances of the exporter for each. This seemed like a better approach than overloading the exporter with the ability to pass different certificates per-target. ## Proxying The https client used by the exporter supports the use of proxy servers discovered by the environment variables `HTTP_PROXY`, `HTTPS_PROXY` and `ALL_PROXY`. For instance: $ export HTTPS_PROXY=localhost:8888 $ ./ssl_exporter In order to use the https client, targets must be provided to the exporter with the protocol in the uri (`https://:`). ## Grafana You can find a simple dashboard [here](grafana/dashboard.json) that tracks certificate expiration dates and target connection errors. ## Acknowledgements The overall structure and implementation of this exporter is based on the [consul_exporter](https://github.com/prometheus/consul_exporter). The probing functionality borrows from the blackbox_exporter.