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 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.
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
rewriteaction. - The
action_parametersobject configuring the HTTP header added to requests with exposed credentials. - The
exposed_credential_checkobject.
{ "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.