Configure exposed credentials checks 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.

Create a custom rule checking for exposed credentials

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 with exposed credentials check 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.

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 credential 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 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" \-H "Authorization: Bearer <API_TOKEN>" \-d '{  "name": "Custom Ruleset A",  "kind": "custom",  "description": "This ruleset includes a rule checking for exposed credentials.",  "rules": [    {      "action": "log",      "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",        "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": []
}

This 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 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" \-H "Authorization: Bearer <API_TOKEN>" \-d '{  "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"          }        }      },      "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"            }          }        },        "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": []
}