offsecnotes

GraphQL API

by frankheat

GraphQL syntax: https://portswigger.net/web-security/graphql/what-is-graphql

Serving over HTTP

HTTP GET

GraphQL query should be specified in the “query” query string.

http://myapi/graphql?query={me{name}}

HTTP POST

JSON-encoded body

{
  "query": "...",
  "operationName": "...",
  "variables": { "myVariable": "someValue", ... }
}

GraphQL endpoints

Universal queries

Sending query{__typename} to a GraphQL endpoint will return {"data": {"__typename": "query"}} in the response.

Try with POST, GET or POST with application/x-www-form-urlencoded

Common endpoint names

/graphql
/api
/api/graphql
/graphql/api
/graphql/graphql
/v1/graphql
/v1/api
/v1/api/graphql
/v1/graphql/api
/v1/graphql/graphql

More endpoint: SecLists discovery graphql

Note: Response could be “query not present” or similar. (meaning it’s present)

Discovering schema information

Using introspection

To use introspection to discover schema information, query the __schema field. (could be disabled in production environments)

{
    "query": "{__schema{queryType{name}}}"
}

Manual

Running a full introspection query 
    #Full introspection query

    query IntrospectionQuery {
        __schema {
            queryType {
                name
            }
            mutationType {
                name
            }
            subscriptionType {
                name
            }
            types {
             ...FullType
            }
            directives {
                name
                description
                args {
                    ...InputValue
            }
            onOperation  #Often needs to be deleted to run query
            onFragment   #Often needs to be deleted to run query
            onField      #Often needs to be deleted to run query
            }
        }
    }

    fragment FullType on __Type {
        kind
        name
        description
        fields(includeDeprecated: true) {
            name
            description
            args {
                ...InputValue
            }
            type {
                ...TypeRef
            }
            isDeprecated
            deprecationReason
        }
        inputFields {
            ...InputValue
        }
        interfaces {
            ...TypeRef
        }
        enumValues(includeDeprecated: true) {
            name
            description
            isDeprecated
            deprecationReason
        }
        possibleTypes {
            ...TypeRef
        }
    }

    fragment InputValue on __InputValue {
        name
        description
        type {
            ...TypeRef
        }
        defaultValue
    }

    fragment TypeRef on __Type {
        kind
        name
        ofType {
            kind
            name
            ofType {
                kind
                name
                ofType {
                    kind
                    name
                }
            }
        }
    }

If introspection is enabled but the query fails, try removing the onOperation, onFragment, and onField directives. Many endpoints don’t accept these in introspection queries.

Automatic

Burp
  1. Browse the target application for requests to a GraphQL endpoint
  2. Right-click the GraphQL request, select “Send to Repeater”
  3. In Repeater, right-click in the Request panel, choose “GraphQL > Set introspection query”
  4. Click Send. If introspection is enabled, the server will return the full API schema. If you are working with an older GraphQL server, it may fail. So right-click within the Request and select GraphQL > Set legacy introspection query and try again.
  5. In the Response panel, right-click and select “GraphQL > Save GraphQL queries to site map.” Burp saves discovered queries as nodes on the site map. You can review these queries, and send them to Intruder or Repeater for further investigation or attacks.

https://portswigger.net/burp/documentation/desktop/testing-workflow/working-with-graphql#accessing-graphql-api-schemas-using-introspection

Now you can easily view relationships between schema entities using a GraphQL visualizer: https://graphql-kit.com/graphql-voyager/

Suggestions

Suggestions are a feature of the Apollo GraphQL platform where the server suggests query amendments in error messages. Clairvoyance is a tool that uses suggestions to automatically recover all or part of a GraphQL schema, even when introspection is disabled.

Bypassing GraphQL introspection defenses

Bypassing rate limiting

Use aliases to return multiple instances of the same type of object in one request.

    #Request with aliased queries

    query isValidDiscount($code: Int) {
        isvalidDiscount(code:$code){
            valid
        }
        isValidDiscount2:isValidDiscount(code:$code){
            valid
        }
        isValidDiscount3:isValidDiscount(code:$code){
            valid
        }
    }

GraphQL CSRF

GraphQL can be exploited for CSRF attacks. POST requests with application/json content type are secure against forgery if the content type is validated.

GET requests and POST with application/x-www-form-urlencoded content type can be sent by browsers.

JS script to convert JSON to application x-www-form-urlencoded 
function jsonToUrlEncoded(jsonData) {
    const params = new URLSearchParams();

    for (const [key, value] of Object.entries(jsonData)) {
        if (typeof value === 'object') {
            params.append(key, JSON.stringify(value));
        } else {
            params.append(key, value);
        }
    }

    return params.toString();
}

// To change
const jsonData = {"query":"test","operationName":"test","variables":{"a":1,"b":2}};

const urlEncodedData = jsonToUrlEncoded(jsonData);
console.log(urlEncodedData);