node_exporter/https/README.md

# HTTPS Package for Prometheus

The `https` directory contains a Go package and a sample configuration file for
running `node_exporter` with HTTPS instead of HTTP. We currently support TLS 1.3
and TLS 1.2.

To run a server with TLS, use the flag `--web.config`.

e.g. `./node_exporter --web.config="web-config.yml"`
If the config is kept within the https directory.

The config file should be written in YAML format, and is reloaded on each connection to check for new certificates and/or authentication policy.

## Sample Config

```
tls_server_config:
  # Certificate and key files for server to use to authenticate to client.
  cert_file: <filename>
  key_file: <filename>

  # Server policy for client authentication. Maps to ClientAuth Policies.
  # For more detail on clientAuth options: [ClientAuthType](https://golang.org/pkg/crypto/tls/#ClientAuthType)
  [ client_auth_type: <string> | default = "NoClientCert" ]

  # CA certificate for client certificate authentication to the server.
  [ client_ca_file: <filename> ]

  # Minimum TLS version that is acceptable.
  [ min_version: <string> | default = "TLS12" ]

  # Maximum TLS version that is acceptable.
  [ max_version: <string> | default = "TLS13" ]

  # List of supported cipher suites for TLS versions up to TLS 1.2. If empty,
  # Go default cipher suites are used. Available cipher suites are documented
  # in the go documentation:
  # https://golang.org/pkg/crypto/tls/#pkg-constants
  [ cipher_suites:
    [ - <string> ] ]

  # prefer_server_cipher_suites controls whether the server selects the
  # client's most preferred ciphersuite, or the server's most preferred
  # ciphersuite. If true then the server's preference, as expressed in
  # the order of elements in cipher_suites, is used.
  [ prefer_server_cipher_suites: <bool> | default = true ]

  # Elliptic curves that will be used in an ECDHE handshake, in preference
  # order. Available curves are documented in the go documentation:
  # https://golang.org/pkg/crypto/tls/#CurveID
  [ curve_preferences:
    [ - <string> ] ]

http_server_config:
  # Enable HTTP/2 support. Note that HTTP/2 is only supported with TLS.
  # This can not be changed on the fly.
  [ http2: <bool> | default = true ]

# Usernames and hashed passwords that have full access to the web
# server via basic authentication. If empty, no basic authentication is
# required. Passwords are hashed with bcrypt.
basic_auth_users:
  [ <string>: <secret> ... ]
```

## About bcrypt

There are several tools out there to generate bcrypt passwords, e.g.
[htpasswd](https://httpd.apache.org/docs/2.4/programs/htpasswd.html):

`htpasswd -nBC 10 "" | tr -d ':\n'`

That command will prompt you for a password and output the hashed password,
which will look something like:
`$2y$10$X0h1gDsPszWURQaxFh.zoubFi6DXncSjhoQNJgRrnGs7EsimhC7zG`

The cost (10 in the example) influences the time it takes for computing the
hash. A higher cost will en up slowing down the authentication process.
Depending on the machine, a cost of 10 will take about ~70ms where a cost of
18 can take up to a few seconds. That hash will be computed on every
password-protected request.