Configure via API

Configure exposed credentials checks using the Rulesets API. You can do the following:

• Deploy the Cloudflare Exposed Credentials Check Managed Ruleset.
• Create custom rules that check for exposed credentials.

Recommendation: Use leaked credentials detection instead

Cloudflare recommends that you use leaked credentials detection instead of Cloudflare Exposed Credentials Check, which refers to a previous implementation.

Create a custom rule checking for exposed credentials

Note

This feature requires account-level WAF, which is available to Enterprise customers with a paid add-on.

You can create rules that check for exposed credentials using the Rulesets API. Include these rules in a custom ruleset, which you must create at the account level, and then deploy the custom ruleset to a phase.

A rule checking for exposed credentials has a match when both the rule expression and the result from the exposed credentials check are true.

To check for exposed credentials in a custom rule, include the exposed_credential_check object in the rule definition. This object must have the following properties:

• username_expression — Expression that selects the user ID used in the credentials check. This property can have up to 1024 characters.
• password_expression — Expression that selects the password used in the credentials check. This property can have up to 1024 characters.

Note

These properties have additional requirements:

• Each expression must evaluate to a string.
• You can only use the upper(), lower(), url_decode(), and lookup_json_string() functions, and you cannot nest these functions.

You can use the exposed_credential_check object in rules with one of the following actions: rewrite, log, block, challenge, or js_challenge. Cloudflare recommends that you only use exposed credentials checks with the following actions: rewrite and log.

To create and deploy a custom ruleset, follow the workflow described in Work with custom rulesets.

Example A

This POST request example creates a new custom ruleset with a rule that checks for exposed credentials. The rule has a match if both the rule expression and the exposed_credential_check result are true. When there is a match, the rule will log the request with exposed credentials in the Cloudflare logs.

curl "https://api.cloudflare.com/client/v4/accounts/{account_id}/rulesets" \
--header "Authorization: Bearer <API_TOKEN>" \
--header "Content-Type: application/json" \
--data '{
  "name": "Custom Ruleset A",
  "kind": "custom",
  "description": "This ruleset includes a rule checking for exposed credentials.",
  "rules": [
    {
      "action": "log",
      "description": "Exposed credentials check on login.php page",
      "expression": "http.request.method == \"POST\" && http.request.uri == \"/login.php\"",
      "exposed_credential_check": {
        "username_expression": "url_decode(http.request.body.form[\"username\"][0])",
        "password_expression": "url_decode(http.request.body.form[\"password\"][0])"
      }
    }
  ],
  "phase": "http_request_firewall_custom"
}'

The response returns the created ruleset. Note the presence of the exposed_credential_check object on the rule definition.

{
  "result": {
    "id": "<CUSTOM_RULESET_ID>",
    "name": "Custom Ruleset A",
    "description": "This ruleset includes a rule checking for exposed credentials.",
    "kind": "custom",
    "version": "1",
    "rules": [
      {
        "id": "<CUSTOM_RULE_ID>",
        "version": "1",
        "action": "log",
        "description": "Exposed credentials check on login.php page",
        "expression": "http.request.method == \"POST\" && http.request.uri == \"/login.php\"",
        "exposed_credential_check": {
          "username_expression": "url_decode(http.request.body.form[\"username\"][0])",
          "password_expression": "url_decode(http.request.body.form[\"password\"][0])"
        },
        "last_updated": "2021-03-19T10:48:04.057775Z",
        "ref": "<CUSTOM_RULE_REF>",
        "enabled": true
      }
    ],
    "last_updated": "2021-03-19T10:48:04.057775Z",
    "phase": "http_request_firewall_custom"
  },
  "success": true,
  "errors": [],
  "messages": []
}

The example uses the url_decode() function because fields in the request body (available in http.request.body.form) are URL-encoded when the content type is application/x-www-form-urlencoded.

After creating a custom ruleset, deploy it to a phase so that it executes. Refer to Deploy a custom ruleset for more information.

Example B

This POST request example creates a new custom ruleset with a rule that checks for exposed credentials in JSON responses. The rule has a match if both the rule expression and the exposed_credential_check result are true. When there is a match, the rule will add an Exposed-Credential-Check HTTP header to the request with value 1.

curl "https://api.cloudflare.com/client/v4/accounts/{account_id}/rulesets" \
--header "Authorization: Bearer <API_TOKEN>" \
--header "Content-Type: application/json" \
--data '{
  "name": "Custom Ruleset B",
  "kind": "custom",
  "description": "This ruleset includes a rule checking for exposed credentials.",
  "rules": [
    {
      "action": "rewrite",
      "action_parameters": {
        "headers": {
          "Exposed-Credential-Check": {
            "operation": "set",
            "value": "1"
          }
        }
      },
      "description": "Exposed credentials check on login endpoint with JSON body",
      "expression": "http.request.method == \"POST\" && http.request.uri == \"/login.php\" && any(http.request.headers[\"content-type\"][*] == \"application/json\")",
      "exposed_credential_check": {
        "username_expression": "lookup_json_string(http.request.body.raw, \"username\")",
        "password_expression": "lookup_json_string(http.request.body.raw, \"password\")"
      }
    }
  ],
  "phase": "http_request_firewall_custom"
}'

The response returns the created ruleset. Note the presence of the following elements in the rule definition:

• The rewrite action.
• The action_parameters object configuring the HTTP header added to requests with exposed credentials.
• The exposed_credential_check object.

{
  "result": {
    "id": "<CUSTOM_RULESET_ID>",
    "name": "Custom Ruleset B",
    "description": "This ruleset includes a rule checking for exposed credentials.",
    "kind": "custom",
    "version": "1",
    "rules": [
      {
        "id": "<CUSTOM_RULE_ID>",
        "version": "1",
        "action": "rewrite",
        "action_parameters": {
          "headers": {
            "Exposed-Credential-Check": {
              "operation": "set",
              "value": "1"
            }
          }
        },
        "description": "Exposed credentials check on login endpoint with JSON body",
        "expression": "http.request.method == \"POST\" && http.request.uri == \"/login.php\" && any(http.request.headers[\"content-type\"][*] == \"application/json\")",
        "exposed_credential_check": {
          "username_expression": "lookup_json_string(http.request.body.raw, \"username\")",
          "password_expression": "lookup_json_string(http.request.body.raw, \"password\")"
        },
        "last_updated": "2022-03-19T12:48:04.057775Z",
        "ref": "<CUSTOM_RULE_REF>",
        "enabled": true
      }
    ],
    "last_updated": "2022-03-19T12:48:04.057775Z",
    "phase": "http_request_firewall_custom"
  },
  "success": true,
  "errors": [],
  "messages": []
}

Next steps

After creating a custom ruleset, deploy it to the http_request_firewall_custom phase at the account level so that it executes. You will need the ruleset ID to deploy the custom ruleset. For more information, refer to Deploy a custom ruleset.