Web API Fuzz Testing (ULTIMATE)

Web API fuzzing performs fuzz testing of API operation parameters. Fuzz testing sets operation parameters to unexpected values in an effort to cause unexpected behavior and errors in the API backend. This helps you discover bugs and potential security issues that other QA processes may miss.

We recommend that you use fuzz testing in addition to GitLab Secure's other security scanners and your own test processes. If you're using GitLab CI/CD, you can run fuzz tests as part your CI/CD workflow.

When Web API fuzzing runs

Web API fuzzing runs in the fuzz stage of the CI/CD pipeline. To ensure API fuzzing scans the latest code, your CI/CD pipeline should deploy changes to a test environment in one of the stages preceding the fuzz stage.

Note the following changes have been made to the API fuzzing template:

• In GitLab 14.0 and later, you must define a fuzz stage in your .gitlab-ci.yml file.
• In GitLab 13.12 and earlier, the API fuzzing template defines build, test, deploy, and fuzz stages. The fuzz stage runs last by default. The predefined stages were deprecated, and removed from the API-Fuzzing.latest.gitlab-ci.yml template. They will be removed in a future GitLab version.

If your pipeline is configured to deploy to the same web server on each run, running a pipeline while another is still running could cause a race condition in which one pipeline overwrites the code from another. The API to scan should be excluded from changes for the duration of a fuzzing scan. The only changes to the API should be from the fuzzing scanner. Any changes made to the API (for example, by users, scheduled tasks, database changes, code changes, other pipelines, or other scanners) during a scan could cause inaccurate results.

You can run a Web API fuzzing scan using the following methods:

• OpenAPI Specification - version 2, and 3.
• HTTP Archive (HAR)
• Postman Collection - version 2.0 or 2.1

Example projects using these methods are available:

• Example OpenAPI v2 Specification project
• Example HTTP Archive (HAR) project
• Example Postman Collection project
• Example GraphQL project
• Example SOAP project

Enable Web API fuzzing

Requirements:

• One of the following web API types:

  • REST API
  • SOAP
  • GraphQL
  • Form bodies, JSON, or XML

• One of the following assets to provide APIs to test:

  • OpenAPI v2 or v3 API definition
  • HTTP Archive (HAR) of API requests to test
  • Postman Collection v2.0 or v2.1

  WARNING: Never run fuzz testing against a production server. Not only can it perform any function that the API can, it may also trigger bugs in the API. This includes actions like modifying and deleting data. Only run fuzzing against a test server.

To enable Web API fuzzing:

• Include the API fuzzing template in your .gitlab-ci.yml file.

• From GitLab 13.10 and later, use the Web API fuzzing configuration form.

• For manual configuration instructions, see the respective section, depending on the API type:

  • OpenAPI Specification
  • HTTP Archive (HAR)
  • Postman Collection

• Otherwise, see Web API fuzzing configuration form.

In GitLab 14.0 and later, API fuzzing configuration files must be in your repository's .gitlab directory instead of your repository's root.

Web API fuzzing configuration form

Introduced in GitLab 13.10.

The API fuzzing configuration form helps you create or modify your project's API fuzzing configuration. The form lets you choose values for the most common API fuzzing options and builds a YAML snippet that you can paste in your GitLab CI/CD configuration.

Configure Web API fuzzing in the UI

To generate an API Fuzzing configuration snippet:

1. On the top bar, select Menu > Projects and find your project.
2. On the left sidebar, select Security & Compliance > Configuration.
3. In the API Fuzzing row, select Enable API Fuzzing.
4. Complete the fields. For details see Available CI/CD variables.
5. Select Generate code snippet. A modal opens with the YAML snippet corresponding to the options you've selected in the form.
6. Do one of the following:
   1. To copy the snippet to your clipboard, select Copy code only.
   2. To add the snippet to your project's .gitlab-ci.yml file, select Copy code and open .gitlab-ci.yml file. The Pipeline Editor opens.
      1. Paste the snippet into the .gitlab-ci.yml file.
      2. Select the Lint tab to confirm the edited .gitlab-ci.yml file is valid.
      3. Select the Edit tab, then select Commit changes.

When the snippet is committed to the .gitlab-ci.yml file, pipelines include an API Fuzzing job.

OpenAPI Specification

• Support for OpenAPI Specification v3.0 was introduced in GitLab 13.9.
• Support for OpenAPI Specification using YAML format was introduced in GitLab 14.0.
• Support for OpenAPI Specification v3.1 was introduced in GitLab 14.2.
• Support to generate media type application/xml was introduced in GitLab 14.8.
• Support to select media types was introduced in GitLab 14.10.

The OpenAPI Specification (formerly the Swagger Specification) is an API description format for REST APIs. This section shows you how to configure API fuzzing using an OpenAPI Specification to provide information about the target API to test. OpenAPI Specifications are provided as a file system resource or URL. Both JSON and YAML OpenAPI formats are supported.

API fuzzing uses an OpenAPI document to generate the request body. When a request body is required, the body generation is limited to these body types:

• application/x-www-form-urlencoded
• multipart/form-data
• application/json
• application/xml

OpenAPI and media types

A media type (formerly known as MIME type) is an identifier for file formats and format contents transmitted. A OpenAPI document lets you specify that a given operation can accept different media types, hence a given request can send data using different file content. As for example, a PUT /user operation to update user data could accept data in either XML (media type application/xml) or JSON (media type application/json) format. OpenAPI 2.x lets you specify the accepted media types globally or per operation, and OpenAPI 3.x lets you specify the accepted media types per operation. API Fuzzing checks the listed media types and tries to produce sample data for each supported media type.

• In GitLab 14.10 and later, the default behavior is to select one of the supported media types to use. The first supported media type is chosen from the list. This behavior is configurable.
• In GitLab 14.9 and earlier, the default behavior is to perform testing using all supported media types. This means if two media types are listed (for example, application/json and application/xml), tests are performed using JSON, and then the same tests using XML.

Testing the same operation (for example, POST /user) using different media types (for example, application/json and application/xml) is not always desirable. For example, if the target application executes the same code regardless of the request content type, it will take longer to finish the test session, and it may report duplicate vulnerabilities related to the request body depending on the target app.

The environment variable FUZZAPI_OPENAPI_ALL_MEDIA_TYPES lets you specify whether or not to use all supported media types instead of one when generating requests for a given operation. When the environmental variable FUZZAPI_OPENAPI_ALL_MEDIA_TYPES is set to any value, API Fuzzing will try to generate requests for all supported media types instead of one in a given operation. This will cause testing to take longer as testing is repeated for each provided media type.

Alternatively, the variable FUZZAPI_OPENAPI_MEDIA_TYPES is used to provide a list of media types that will each be tested. Providing more than one media type causes testing to take longer, as testing is performed for each media type selected. When the environment variable FUZZAPI_OPENAPI_MEDIA_TYPES is set to a list of media types, only the listed media types are included when creating requests.

Multiple media types in FUZZAPI_OPENAPI_MEDIA_TYPES must separated by a colon (:). For example, to limit request generation to the media types application/x-www-form-urlencoded and multipart/form-data, set the environment variable FUZZAPI_OPENAPI_MEDIA_TYPES to application/x-www-form-urlencoded:multipart/form-data. Only supported media types in this list are included when creating requests, though unsupported media types are always skipped. A media type text may contain different sections. For example, application/vnd.api+json; charset=UTF-8 is a compound of type "/" [tree "."] subtype ["+" suffix]* [";" parameter]. Parameters are not taken into account when filtering media types on request generation.

The environment variables FUZZAPI_OPENAPI_ALL_MEDIA_TYPES and FUZZAPI_OPENAPI_MEDIA_TYPES allow you to decide how to handle media types. These settings are mutually exclusive. If both are enabled, API Fuzzing reports an error.

Configure Web API fuzzing with an OpenAPI Specification

To configure API fuzzing in GitLab with an OpenAPI Specification:

1. Add the fuzz stage to your .gitlab-ci.yml file.

2. Include the API-Fuzzing.gitlab-ci.yml template in your .gitlab-ci.yml file.

3. Provide the profile by adding the FUZZAPI_PROFILE CI/CD variable to your .gitlab-ci.yml file. The profile specifies how many tests are run. Substitute Quick-10 for the profile you choose. For more details, see API fuzzing profiles.

   variables:
     FUZZAPI_PROFILE: Quick-10

4. Provide the location of the OpenAPI Specification. You can provide the specification as a file or URL. Specify the location by adding the FUZZAPI_OPENAPI variable.

5. Provide the target API instance's base URL. Use either the FUZZAPI_TARGET_URL variable or an environment_url.txt file.

   Adding the URL in an environment_url.txt file at your project's root is great for testing in dynamic environments. To run API fuzzing against an application dynamically created during a GitLab CI/CD pipeline, have the application persist its URL in an environment_url.txt file. API fuzzing automatically parses that file to find its scan target. You can see an example of this in the Auto DevOps CI YAML.

Example .gitlab-ci.yml file using an OpenAPI Specification:

stages:
  - fuzz

include:
  - template: API-Fuzzing.gitlab-ci.yml

variables:
  FUZZAPI_PROFILE: Quick-10
  FUZZAPI_OPENAPI: test-api-specification.json
  FUZZAPI_TARGET_URL: http://test-deployment/

This is a minimal configuration for API Fuzzing. From here you can:

• Run your first scan.
• Add authentication.
• Learn how to handle false positives.

For details of API fuzzing configuration options, see Available CI/CD variables.

HTTP Archive (HAR)

The HTTP Archive format (HAR) is an archive file format for logging HTTP transactions. When used with the GitLab API fuzzer, HAR must contain records of calling the web API to test. The API fuzzer extracts all the requests and uses them to perform testing.

For more details, including how to create a HAR file, see HTTP Archive format.

WARNING: HAR files may contain sensitive information such as authentication tokens, API keys, and session cookies. We recommend that you review the HAR file contents before adding them to a repository.

Configure Web API fuzzing with a HAR file

To configure API fuzzing to use a HAR file:

1. Add the fuzz stage to your .gitlab-ci.yml file.

2. Include the API-Fuzzing.gitlab-ci.yml template in your .gitlab-ci.yml file.

3. Provide the profile by adding the FUZZAPI_PROFILE CI/CD variable to your .gitlab-ci.yml file. The profile specifies how many tests are run. Substitute Quick-10 for the profile you choose. For more details, see API fuzzing profiles.

   variables:
     FUZZAPI_PROFILE: Quick-10

4. Provide the location of the HAR specification. You can provide the specification as a file or URL. URL support was introduced in GitLab 13.10 and later. Specify the location by adding the FUZZAPI_HAR variable.

5. The target API instance's base URL is also required. Provide it by using the FUZZAPI_TARGET_URL variable or an environment_url.txt file.

   Adding the URL in an environment_url.txt file at your project's root is great for testing in dynamic environments. To run API fuzzing against an app dynamically created during a GitLab CI/CD pipeline, have the app persist its domain in an environment_url.txt file. API fuzzing automatically parses that file to find its scan target. You can see an example of this in our Auto DevOps CI YAML.

Example .gitlab-ci.yml file using a HAR file:

stages:
  - fuzz

include:
  - template: API-Fuzzing.gitlab-ci.yml

variables:
  FUZZAPI_PROFILE: Quick-10
  FUZZAPI_HAR: test-api-recording.har
  FUZZAPI_TARGET_URL: http://test-deployment/

This is a minimal configuration for API fuzzing. From here you can:

• Run your first scan.
• Add authentication.
• Learn how to handle false positives.

For details of API fuzzing configuration options, see Available CI/CD variables.

Postman Collection

The Postman API Client is a popular tool that developers and testers use to call various types of APIs. The API definitions can be exported as a Postman Collection file for use with API Fuzzing. When exporting, make sure to select a supported version of Postman Collection: v2.0 or v2.1.

When used with the GitLab API fuzzer, Postman Collections must contain definitions of the web API to test with valid data. The API fuzzer extracts all the API definitions and uses them to perform testing.

WARNING: Postman Collection files may contain sensitive information such as authentication tokens, API keys, and session cookies. We recommend that you review the Postman Collection file contents before adding them to a repository.

Configure Web API fuzzing with a Postman Collection file

To configure API fuzzing to use a Postman Collection file:

1. Add the fuzz stage to your .gitlab-ci.yml file.

2. Include the API-Fuzzing.gitlab-ci.yml template in your .gitlab-ci.yml file.

3. Provide the profile by adding the FUZZAPI_PROFILE CI/CD variable to your .gitlab-ci.yml file. The profile specifies how many tests are run. Substitute Quick-10 for the profile you choose. For more details, see API fuzzing profiles.

   variables:
     FUZZAPI_PROFILE: Quick-10

4. Provide the location of the Postman Collection specification. You can provide the specification as a file or URL. URL support was introduced in GitLab 13.10 and later. Specify the location by adding the FUZZAPI_POSTMAN_COLLECTION variable.

5. Provide the target API instance's base URL. Use either the FUZZAPI_TARGET_URL variable or an environment_url.txt file.

   Adding the URL in an environment_url.txt file at your project's root is great for testing in dynamic environments. To run API fuzzing against an app dynamically created during a GitLab CI/CD pipeline, have the app persist its domain in an environment_url.txt file. API fuzzing automatically parses that file to find its scan target. You can see an example of this in our Auto DevOps CI YAML.

Example .gitlab-ci.yml file using a Postman Collection file:

stages:
  - fuzz

include:
  - template: API-Fuzzing.gitlab-ci.yml

variables:
  FUZZAPI_PROFILE: Quick-10
  FUZZAPI_POSTMAN_COLLECTION: postman-collection_serviceA.json
  FUZZAPI_TARGET_URL: http://test-deployment/

This is a minimal configuration for API Fuzzing. From here you can:

• Run your first scan.
• Add authentication.
• Learn how to handle false positives.

For details of API fuzzing configuration options, see Available CI/CD variables.

Postman variables

Postman allows the developer to define placeholders that can be used in different parts of the requests. These placeholders are called variables, as explained in the Postman documentation, Using variables. You can use variables to store and reuse values in your requests and scripts. For example, you can edit the collection to add variables to the document:

You can then use the variables in sections such as URL, headers, and others:

Variables can be defined at different scopes (for example, Global, Collection, Environment, Local, and Data). In this example, they're defined at the Environment scope:

When you export a Postman collection, only Postman collection variables are exported into the Postman file. For example, Postman does not export environment-scoped variables into the Postman file.

By default, the API fuzzer uses the Postman file to resolve Postman variable values. If a JSON file is set in a GitLab CI/CD variable FUZZAPI_POSTMAN_COLLECTION_VARIABLES, then the JSON file takes precedence to get Postman variable values.

WARNING: Although Postman can export environment variables into a JSON file, the format is not compatible with the JSON expected by FUZZAPI_POSTMAN_COLLECTION_VARIABLES.

Here is an example of using FUZZAPI_POSTMAN_COLLECTION_VARIABLES:

stages:
     - fuzz

include:
  - template: API-Fuzzing.gitlab-ci.yml

variables:
  FUZZAPI_PROFILE: Quick-10
  FUZZAPI_POSTMAN_COLLECTION: postman-collection_serviceA.json
  FUZZAPI_TARGET_URL: http://test-deployment/
  FUZZAPI_POSTMAN_COLLECTION_VARIABLES: variable-collection-dictionary.json

The file variable-collection-dictionary.json is a JSON document. This JSON is an object with key-value pairs for properties. The keys are the variables' names, and the values are the variables' values. For example:

{
   "base_url": "http://127.0.0.1/",
   "token": "Token 84816165151"
}

API fuzzing configuration

The API fuzzing behavior can be changed through CI/CD variables.

From GitLab 13.12 and later, the default API fuzzing configuration file is .gitlab/gitlab-api-fuzzing-config.yml. In GitLab 14.0 and later, API fuzzing configuration files must be in your repository's .gitlab directory instead of your repository's root.

WARNING: All customization of GitLab security scanning tools should be tested in a merge request before merging these changes to the default branch. Failure to do so can give unexpected results, including a large number of false positives.

Authentication

Authentication is handled by providing the authentication token as a header or cookie. You can provide a script that performs an authentication flow or calculates the token.

HTTP Basic Authentication

HTTP basic authentication is an authentication method built in to the HTTP protocol and used in conjunction with transport layer security (TLS). To use HTTP basic authentication, two CI/CD variables are added to your .gitlab-ci.yml file:

• FUZZAPI_HTTP_USERNAME: The username for authentication.
• FUZZAPI_HTTP_PASSWORD: The password for authentication.

For the password, we recommended that you create a CI/CD variable (for example, TEST_API_PASSWORD) set to the password. You can create CI/CD variables from the GitLab projects page at Settings > CI/CD, in the Variables section. Use that variable as the value for FUZZAPI_HTTP_PASSWORD:

stages:
     - fuzz

include:
  - template: API-Fuzzing.gitlab-ci.yml

variables:
  FUZZAPI_PROFILE: Quick-10
  FUZZAPI_HAR: test-api-recording.har
  FUZZAPI_TARGET_URL: http://test-deployment/
  FUZZAPI_HTTP_USERNAME: testuser
  FUZZAPI_HTTP_PASSWORD: $TEST_API_PASSWORD

Bearer Tokens

Bearer tokens are used by several different authentication mechanisms, including OAuth2 and JSON Web Tokens (JWT). Bearer tokens are transmitted using the Authorization HTTP header. To use bearer tokens with API fuzzing, you need one of the following:

• A token that doesn't expire
• A way to generate a token that lasts the length of testing
• A Python script that API fuzzing can call to generate the token

Token doesn't expire

If the bearer token doesn't expire, use the FUZZAPI_OVERRIDES_ENV variable to provide it. This variable's content is a JSON snippet that provides headers and cookies to add to API fuzzing's outgoing HTTP requests.

Follow these steps to provide the bearer token with FUZZAPI_OVERRIDES_ENV:

1. Create a CI/CD variable, for example TEST_API_BEARERAUTH, with the value {"headers":{"Authorization":"Bearer dXNlcm5hbWU6cGFzc3dvcmQ="}} (substitute your token). You can create CI/CD variables from the GitLab projects page at Settings > CI/CD, in the Variables section.

2. In your .gitlab-ci.yml file, set FUZZAPI_OVERRIDES_ENV to the variable you just created:

   stages:
     - fuzz
   
   include:
     - template: API-Fuzzing.gitlab-ci.yml
   
   variables:
     FUZZAPI_PROFILE: Quick-10
     FUZZAPI_OPENAPI: test-api-specification.json
     FUZZAPI_TARGET_URL: http://test-deployment/
     FUZZAPI_OVERRIDES_ENV: $TEST_API_BEARERAUTH

3. To validate that authentication is working, run an API fuzzing test and review the fuzzing logs and the test API's application logs. See the overrides section for more information about override commands.

Token generated at test runtime

If the bearer token must be generated and doesn't expire during testing, you can provide to API fuzzing a file containing the token. A prior stage and job, or part of the API fuzzing job, can generate this file.

API fuzzing expects to receive a JSON file with the following structure:

{
  "headers" : {
    "Authorization" : "Bearer dXNlcm5hbWU6cGFzc3dvcmQ="
  }
}

This file can be generated by a prior stage and provided to API fuzzing through the FUZZAPI_OVERRIDES_FILE CI/CD variable.

Set FUZZAPI_OVERRIDES_FILE in your .gitlab-ci.yml file:

stages:
     - fuzz

include:
  - template: API-Fuzzing.gitlab-ci.yml

variables:
  FUZZAPI_PROFILE: Quick
  FUZZAPI_OPENAPI: test-api-specification.json
  FUZZAPI_TARGET_URL: http://test-deployment/
  FUZZAPI_OVERRIDES_FILE: api-fuzzing-overrides.json

To validate that authentication is working, run an API fuzzing test and review the fuzzing logs and the test API's application logs.

Token has short expiration

If the bearer token must be generated and expires prior to the scan's completion, you can provide a program or script for the API fuzzer to execute on a provided interval. The provided script runs in an Alpine Linux container that has Python 3 and Bash installed. If the Python script requires additional packages, it must detect this and install the packages at runtime.

The script must create a JSON file containing the bearer token in a specific format:

{
  "headers" : {
    "Authorization" : "Bearer dXNlcm5hbWU6cGFzc3dvcmQ="
  }
}

You must provide three CI/CD variables, each set for correct operation:

• FUZZAPI_OVERRIDES_FILE: JSON file the provided command generates.
• FUZZAPI_OVERRIDES_CMD: Command that generates the JSON file.
• FUZZAPI_OVERRIDES_INTERVAL: Interval (in seconds) to run command.

For example:

stages:
     - fuzz

include:
  - template: API-Fuzzing.gitlab-ci.yml

variables:
  FUZZAPI_PROFILE: Quick-10
  FUZZAPI_OPENAPI: test-api-specification.json
  FUZZAPI_TARGET_URL: http://test-deployment/
  FUZZAPI_OVERRIDES_FILE: api-fuzzing-overrides.json
  FUZZAPI_OVERRIDES_CMD: renew_token.py
  FUZZAPI_OVERRIDES_INTERVAL: 300

To validate that authentication is working, run an API fuzzing test and review the fuzzing logs and the test API's application logs.

API fuzzing profiles

GitLab provides the configuration file gitlab-api-fuzzing-config.yml. It contains several testing profiles that perform a specific numbers of tests. The runtime of each profile increases as the number of tests increases.

Available CI/CD variables

Overrides

API Fuzzing provides a method to add or override specific items in your request, for example:

• Headers
• Cookies
• Query string
• Form data
• JSON nodes
• XML nodes

You can use this to inject semantic version headers, authentication, and so on. The authentication section includes examples of using overrides for that purpose.

Overrides use a JSON document, where each type of override is represented by a JSON object:

{
  "headers": {
    "header1": "value",
    "header2": "value"
  },
  "cookies": {
    "cookie1": "value",
    "cookie2": "value"
  },
  "query":      {
    "query-string1": "value",
    "query-string2": "value"
  },
  "body-form":  {
    "form-param1": "value",
    "form-param2": "value"
  },
  "body-json":  {
    "json-path1": "value",
    "json-path2": "value"
  },
  "body-xml" :  {
    "xpath1":    "value",
    "xpath2":    "value"
  }
}

Example of setting a single header:

{
  "headers": {
    "Authorization": "Bearer dXNlcm5hbWU6cGFzc3dvcmQ="
  }
}

Example of setting both a header and cookie:

{
  "headers": {
    "Authorization": "Bearer dXNlcm5hbWU6cGFzc3dvcmQ="
  },
  "cookies": {
    "flags": "677"
  }
}

Example usage for setting a body-form override:

{
  "body-form":  {
    "username": "john.doe"
  }
}

The override engine uses body-form when the request body has only form-data content.

Example usage for setting a body-json override:

{
  "body-json":  {
    "$.credentials.access-token": "iddqd!42.$"
  }
}

Note that each JSON property name in the object body-json is set to a JSON Path expression. The JSON Path expression $.credentials.access-token identifies the node to be overridden with the value iddqd!42.$. The override engine uses body-json when the request body has only JSON content.

For example, if the body is set to the following JSON:

{
    "credentials" : {
        "username" :"john.doe",
        "access-token" : "non-valid-password"
    }
}

It is changed to:

{
    "credentials" : {
        "username" :"john.doe",
        "access-token" : "iddqd!42.$"
    }
}

Here's an example for setting a body-xml override. The first entry overrides an XML attribute and the second entry overrides an XML element:

{
  "body-xml" :  {
    "/credentials/@isEnabled": "true",
    "/credentials/access-token/text()" : "iddqd!42.$"
  }
}

Note that each JSON property name in the object body-xml is set to an XPath v2 expression. The XPath expression /credentials/@isEnabled identifies the attribute node to override with the value true. The XPath expression /credentials/access-token/text() identifies the element node to override with the value iddqd!42.$. The override engine uses body-xml when the request body has only XML content.

For example, if the body is set to the following XML:

<credentials isEnabled="false">
  <username>john.doe</username>
  <access-token>non-valid-password</access-token>
</credentials>

It is changed to:

<credentials isEnabled="true">
  <username>john.doe</username>
  <access-token>iddqd!42.$</access-token>
</credentials>

You can provide this JSON document as a file or environment variable. You may also provide a command to generate the JSON document. The command can run at intervals to support values that expire.

Using a file

To provide the overrides JSON as a file, the FUZZAPI_OVERRIDES_FILE CI/CD variable is set. The path is relative to the job current working directory.

Here's an example .gitlab-ci.yml:

stages:
     - fuzz

include:
  - template: API-Fuzzing.gitlab-ci.yml

variables:
  FUZZAPI_PROFILE: Quick
  FUZZAPI_OPENAPI: test-api-specification.json
  FUZZAPI_TARGET_URL: http://test-deployment/
  FUZZAPI_OVERRIDES_FILE: api-fuzzing-overrides.json

Using a CI/CD variable

To provide the overrides JSON as a CI/CD variable, use the FUZZAPI_OVERRIDES_ENV variable. This allows you to place the JSON as variables that can be masked and protected.

In this example .gitlab-ci.yml, the FUZZAPI_OVERRIDES_ENV variable is set directly to the JSON:

stages:
     - fuzz

include:
  - template: API-Fuzzing.gitlab-ci.yml

variables:
  FUZZAPI_PROFILE: Quick
  FUZZAPI_OPENAPI: test-api-specification.json
  FUZZAPI_TARGET_URL: http://test-deployment/
  FUZZAPI_OVERRIDES_ENV: '{"headers":{"X-API-Version":"2"}}'

In this example .gitlab-ci.yml, the SECRET_OVERRIDES variable provides the JSON. This is a group or instance level CI/CD variable defined in the UI:

stages:
     - fuzz

include:
  - template: API-Fuzzing.gitlab-ci.yml

variables:
  FUZZAPI_PROFILE: Quick
  FUZZAPI_OPENAPI: test-api-specification.json
  FUZZAPI_TARGET_URL: http://test-deployment/
  FUZZAPI_OVERRIDES_ENV: $SECRET_OVERRIDES

Using a command

If the value must be generated or regenerated on expiration, you can provide a program or script for the API fuzzer to execute on a specified interval. The provided script runs in an Alpine Linux container that has Python 3 and Bash installed.

You have to set the environment variable FUZZAPI_OVERRIDES_CMD to the program or script you would like to execute. The provided command creates the overrides JSON file as defined previously.

You might want to install other scripting runtimes like NodeJS or Ruby, or maybe you need to install a dependency for your overrides command. In this case, we recommend setting the FUZZAPI_PRE_SCRIPT to the file path of a script which provides those prerequisites. The script provided by FUZZAPI_PRE_SCRIPT is executed once, before the analyzer starts.

See the Alpine Linux package management page for information about installing Alpine Linux packages.

You must provide three CI/CD variables, each set for correct operation:

• FUZZAPI_OVERRIDES_FILE: File generated by the provided command.
• FUZZAPI_OVERRIDES_CMD: Overrides command in charge of generating the overrides JSON file periodically.
• FUZZAPI_OVERRIDES_INTERVAL: Interval in seconds to run command.

Optionally:

• FUZZAPI_PRE_SCRIPT: Script to install runtimes or dependencies before the analyzer starts.

WARNING: To execute scripts in Alpine Linux you must first use the command chmod to set the execution permission. For example, to set the execution permission of script.py for everyone, use the command: chmod a+x script.py. If needed, you can version your script.py with the execution permission already set.

stages:
     - fuzz

include:
  - template: API-Fuzzing.gitlab-ci.yml

variables:
  FUZZAPI_PROFILE: Quick
  FUZZAPI_OPENAPI: test-api-specification.json
  FUZZAPI_TARGET_URL: http://test-deployment/
  FUZZAPI_OVERRIDES_FILE: api-fuzzing-overrides.json
  FUZZAPI_OVERRIDES_CMD: renew_token.py
  FUZZAPI_OVERRIDES_INTERVAL: 300

Debugging overrides

Introduced in GitLab 14.8.

By default the output of the overrides command is hidden. If the overrides command returns a non zero exit code, the command is displayed as part of your job output. Optionally, you can set the variable FUZZAPI_OVERRIDES_CMD_VERBOSE to any value in order to display overrides command output as it is generated. This is useful when testing your overrides script, but should be disabled afterwards as it slows down testing.

It is also possible to write messages from your script to a log file that is collected when the job completes or fails. The log file must be created in a specific location and follow a naming convention.

Adding some basic logging to your overrides script is useful in case the script fails unexpectedly during normal running of the job. The log file is automatically included as an artifact of the job, allowing you to download it after the job has finished.

Following our example, we provided renew_token.py in the environmental variable FUZZAPI_OVERRIDES_CMD. Please notice two things in the script:

• Log file is saved in the location indicated by the environment variable CI_PROJECT_DIR.
• Log filename should match gl-*.log.

#!/usr/bin/env python

# Example of an overrides command

# Override commands can update the overrides json file
# with new values to be used.  This is a great way to
# update an authentication token that will expire
# during testing.

import logging
import json
import os
import requests
import backoff

# [1] Store log file in directory indicated by env var CI_PROJECT_DIR
working_directory = os.environ.get( 'CI_PROJECT_DIR')
overrides_file_name = os.environ.get('FUZZAPI_OVERRIDES_FILE', 'api-fuzzing-overrides.json')
overrides_file_path = os.path.join(working_directory, overrides_file_name)

# [2] File name should match the pattern: gl-*.log
log_file_path = os.path.join(working_directory, 'gl-user-overrides.log')

# Set up logger
logging.basicConfig(filename=log_file_path, level=logging.DEBUG)

# Use `backoff` decorator to retry in case of transient errors.
@backoff.on_exception(backoff.expo,
                      (requests.exceptions.Timeout,
                       requests.exceptions.ConnectionError),
                       max_time=30)
def get_auth_response():
    authorization_url = 'https://authorization.service/api/get_api_token'
    return requests.get(
        f'{authorization_url}',
        auth=(os.environ.get('AUTH_USER'), os.environ.get('AUTH_PWD'))
    )

# In our example, access token is retrieved from a given endpoint
try:

    # Performs a http request, response sample:
    # { "Token" : "b5638ae7-6e77-4585-b035-7d9de2e3f6b3" }
    response = get_auth_response()

    # Check that the request is successful. may raise `requests.exceptions.HTTPError`
    response.raise_for_status()

    # Gets JSON data
    response_body = response.json()

# If needed specific exceptions can be caught
# requests.ConnectionError                  : A network connection error problem occurred
# requests.HTTPError                        : HTTP request returned an unsuccessful status code. [Response.raise_for_status()]
# requests.ConnectTimeout                   : The request timed out while trying to connect to the remote server
# requests.ReadTimeout                      : The server did not send any data in the allotted amount of time.
# requests.TooManyRedirects                 : The request exceeds the configured number of maximum redirections
# requests.exceptions.RequestException      : All exceptions that related to Requests
except json.JSONDecodeError as json_decode_error:
    # logs errors related decoding JSON response
    logging.error(f'Error, failed while decoding JSON response. Error message: {json_decode_error}')
    raise
except requests.exceptions.RequestException as requests_error:
    # logs  exceptions  related to `Requests`
    logging.error(f'Error, failed while performing HTTP request. Error message: {requests_error}')
    raise
except Exception as e:
    # logs any other error
    logging.error(f'Error, unknown error while retrieving access token. Error message: {e}')
    raise

# computes object that holds overrides file content.
# It uses data fetched from request
overrides_data = {
    "headers": {
        "Authorization": f"Token {response_body['Token']}"
    }
}

# log entry informing about the file override computation
logging.info("Creating overrides file: %s" % overrides_file_path)

# attempts to overwrite the file
try:
    if os.path.exists(overrides_file_path):
        os.unlink(overrides_file_path)

    # overwrites the file with our updated dictionary
    with open(overrides_file_path, "wb+") as fd:
        fd.write(json.dumps(overrides_data).encode('utf-8'))
except Exception as e:
    # logs any other error
    logging.error(f'Error, unknown error when overwriting file {overrides_file_path}. Error message: {e}')
    raise

# logs informing override has finished successfully
logging.info("Override file has been updated")

# end

In the overrides command example, the Python script depends on the backoff library. To make sure the library is installed before executing the Python script, the FUZZAPI_PRE_SCRIPT is set to a script that will install the dependencies of your overrides command. As for example, the following script user-pre-scan-set-up.sh:

#!/bin/bash

# user-pre-scan-set-up.sh
# Ensures python dependencies are installed

echo "**** install python dependencies ****"

python3 -m ensurepip
pip3 install --no-cache --upgrade \
    pip \
    requests \
    backoff

echo "**** python dependencies installed ****"

# end

You have to update your configuration to set the FUZZAPI_PRE_SCRIPT to our new user-pre-scan-set-up.sh script. For example:

stages:
     - fuzz

include:
  - template: API-Fuzzing.gitlab-ci.yml

variables:
  FUZZAPI_PROFILE: Quick
  FUZZAPI_OPENAPI: test-api-specification.json
  FUZZAPI_TARGET_URL: http://test-deployment/
  FUZZAPI_PRE_SCRIPT: user-pre-scan-set-up.sh
  FUZZAPI_OVERRIDES_FILE: api-fuzzing-overrides.json
  FUZZAPI_OVERRIDES_CMD: renew_token.py
  FUZZAPI_OVERRIDES_INTERVAL: 300

In the previous sample, you could use the script user-pre-scan-set-up.sh to also install new runtimes or applications that later on you could use in your overrides command.

Exclude Paths

Introduced in GitLab 14.0.

When testing an API it can be useful to exclude certain paths. For example, you might exclude testing of an authentication service or an older version of the API. To exclude paths, use the FUZZAPI_EXCLUDE_PATHS CI/CD variable . This variable is specified in your .gitlab-ci.yml file. To exclude multiple paths, separate entries using the ; character. In the provided paths you can use a single character wildcard ? and * for a multiple character wildcard.

To verify the paths are excluded, review the Tested Operations and Excluded Operations portion of the job output. You should not see any excluded paths listed under Tested Operations.

2021-05-27 21:51:08 [INF] API Security: --[ Tested Operations ]-------------------------
2021-05-27 21:51:08 [INF] API Security: 201 POST http://target:7777/api/users CREATED
2021-05-27 21:51:08 [INF] API Security: ------------------------------------------------
2021-05-27 21:51:08 [INF] API Security: --[ Excluded Operations ]-----------------------
2021-05-27 21:51:08 [INF] API Security: GET http://target:7777/api/messages
2021-05-27 21:51:08 [INF] API Security: POST http://target:7777/api/messages
2021-05-27 21:51:08 [INF] API Security: ------------------------------------------------

Examples of excluding paths

This example excludes the /auth resource. This does not exclude child resources (/auth/child).

variables:
  FUZZAPI_EXCLUDE_PATHS=/auth

To exclude /auth, and child resources (/auth/child), we use a wildcard.

variables:
  FUZZAPI_EXCLUDE_PATHS=/auth*

To exclude multiple paths we can use the ; character. In this example we exclude /auth* and /v1/*.

variables:
  FUZZAPI_EXCLUDE_PATHS=/auth*;/v1/*

Exclude parameters

Introduced in GitLab 14.10.

While testing an API you may might want to exclude a parameter (query string, header, or body element) from testing. This may be needed because a parameter always causes a failure, slows down testing, or for other reasons. To exclude parameters you can use one of the following variables: FUZZAPI_EXCLUDE_PARAMETER_ENV or FUZZAPI_EXCLUDE_PARAMETER_FILE.

The FUZZAPI_EXCLUDE_PARAMETER_ENV allows providing a JSON string containing excluded parameters. This is a good option if the JSON is short and will not often change. Another option is the variable FUZZAPI_EXCLUDE_PARAMETER_FILE. This variable is set to a file path that can be checked into the repository, created by another job as an artifact, or generated at runtime from a pre script using FUZZAPI_PRE_SCRIPT.

Exclude parameters using a JSON document

The JSON document contains a JSON object which uses specific properties to identify which parameter should be excluded. You can provide the following properties to exclude specific parameters during the scanning process:

• headers: Use this property to exclude specific headers. The property's value is an array of header names to be excluded. Names are case-insensitive.
• cookies: Use this property's value to exclude specific cookies. The property's value is an array of cookie names to be excluded. Names are case-sensitive.
• query: Use this property to exclude specific fields from the query string. The property's value is an array of field names from the query string to be excluded. Names are case-sensitive.
• body-form: Use this property to exclude specific fields from a request that uses the media type application/x-www-form-urlencoded. The property's value is an array of the field names from the body to be excluded. Names are case-sensitive.
• body-json: Use this property to exclude specific JSON nodes from a request that uses the media type application/json. The property's value is an array, each entry of the array is a JSON Path expression.
• body-xml: Use this property to exclude specific XML nodes from a request that uses media type application/xml. The property's value is an array, each entry of the array is a XPath v2 expression.

The following JSON document is an example of the expected structure to exclude parameters.

{
  "headers": [
    "header1",
    "header2"
  ],
  "cookies": [
    "cookie1",
    "cookie2"
  ],
  "query": [
    "query-string1",
    "query-string2"
  ],
  "body-form": [
    "form-param1",
    "form-param2"
  ],
  "body-json": [
    "json-path-expression-1",
    "json-path-expression-2"
  ],
  "body-xml" : [
    "xpath-expression-1",
    "xpath-expression-2"
  ]
}

Examples

Excluding a single header

To exclude the header Upgrade-Insecure-Requests, set the header property's value to an array with the header name: [ "Upgrade-Insecure-Requests" ]. For instance, the JSON document looks like this:

{
  "headers": [ "Upgrade-Insecure-Requests" ]
}

Header names are case-insensitive, thus the header name UPGRADE-INSECURE-REQUESTS is equivalent to Upgrade-Insecure-Requests.

Excluding both a header and two cookies

To exclude the header Authorization and the cookies PHPSESSID and csrftoken, set the headers property's value to an array with header name [ "Authorization" ] and the cookies property's value to an array with the cookies' names [ "PHPSESSID", "csrftoken" ]. For instance, the JSON document looks like this:

{
  "headers": [ "Authorization" ],
  "cookies": [ "PHPSESSID", "csrftoken" ]
}

Excluding a body-form parameter

To exclude the password field in a request that uses application/x-www-form-urlencoded, set the body-form property's value to an array with the field name [ "password" ]. For instance, the JSON document looks like this:

{
  "body-form":  [ "password" ]
}

The exclude parameters uses body-form when the request uses a content type application/x-www-form-urlencoded.

Excluding a specific JSON nodes using JSON Path

To exclude the schema property in the root object, set the body-json property's value to an array with the JSON Path expression [ "$.schema" ].

The JSON Path expression uses special syntax to identify JSON nodes: $ refers to the root of the JSON document, . refers to the current object (in our case the root object), and the text schema refers to a property name. Thus, the JSON path expression $.schema refers to a property schema in the root object. For instance, the JSON document looks like this:

{
  "body-json": [ "$.schema" ]
}

The exclude parameters uses body-json when the request uses a content type application/json. Each entry in body-json is expected to be a JSON Path expression. In JSON Path, characters like $, *, . among others have special meaning.

Excluding multiple JSON nodes using JSON Path

To exclude the property password on each entry of an array of users at the root level, set the body-json property's value to an array with the JSON Path expression [ "$.users[*].paswword" ].

The JSON Path expression starts with $ to refer to the root node and uses . to refer to the current node. Then, it uses users to refer to a property and the characters [ and ] to enclose the index in the array you want to use, instead of providing a number as an index you use * to specify any index. After the index reference, we find . which now refers to any given selected index in the array, preceded by a property name password.

For instance, the JSON document looks like this:

{
  "body-json": [ "$.users[*].paswword" ]
}

The exclude parameters uses body-json when the request uses a content type application/json. Each entry in body-json is expected to be a JSON Path expression. In JSON Path characters like $, *, . among others have special meaning.

Excluding an XML attribute

To exclude an attribute named isEnabled located in the root element credentials, set the body-xml property's value to an array with the XPath expression [ "/credentials/@isEnabled" ].

The XPath expression /credentials/@isEnabled, starts with / to indicate the root of the XML document, then it is followed by the word credentials which indicates the name of the element to match. It uses a / to refer to a node of the previous XML element, and the character @ to indicate that the name isEnable is an attribute.

For instance, the JSON document looks like this:

{
  "body-xml": [
    "/credentials/@isEnabled"
  ]
}

The exclude parameters uses body-xml when the request uses a content type application/xml. Each entry in body-xml is expected to be an XPath v2 expression. In XPath expressions, characters like @, /, :, [, ] among others have special meanings.

Excluding an XML element's text

To exclude the text of the username element contained in root node credentials, set the body-xml property's value to an array with the XPath expression [/credentials/username/text()" ].

In the XPath expression /credentials/username/text(), the first character / refers to the root XML node, and then after it indicates an XML element's name credentials. Similarly, the character / refers to the current element, followed by a new XML element's name username. Last part has a / that refers to the current element, and uses a XPath function called text() which identifies the text of the current element.

For instance, the JSON document looks like this:

{
  "body-xml": [
    "/credentials/username/text()"
  ]
}

The exclude parameters uses body-xml when the request uses a content type application/xml. Each entry in body-xml is expected to be a XPath v2 expression. In XPath expressions characters like @, /, :, [, ] among others have special meanings.

Excluding an XML element

To exclude the element username contained in root node credentials, set the body-xml property's value to an array with the XPath expression [/credentials/username" ].

In the XPath expression /credentials/username, the first character / refers to the root XML node, and then after it indicates an XML element's name credentials. Similarly, the character / refers to the current element, followed by a new XML element's name username.

For instance, the JSON document looks like this:

{
  "body-xml": [
    "/credentials/username"
  ]
}

The exclude parameters uses body-xml when the request uses a content type application/xml. Each entry in body-xml is expected to be a XPath v2 expression. In XPath expressions characters like @, /, :, [, ] among others have special meanings.

Excluding an XML node with namespaces

To exclude a XML element login which is defined in namespace s, and contained in credentials root node, set the body-xml property's value to an array with the XPath expression [ "/credentials/s:login" ].

In the XPath expression /credentials/s:login, the first character / refers to the root XML node, and then after it indicates an XML element's name credentials. Similarly, the character / refers to the current element, followed by a new XML element's name s:login. Notice that name contains the character :, this character separates the namespace from the node name.

The namespace name should have been defined in the XML document which is part of the body request. You may check the namespace in the specification document HAR, OpenAPI, or Postman Collection file.

{
  "body-xml": [
    "/credentials/s:login"
  ]
}

The exclude parameters uses body-xml when the request uses a content type application/xml. Each entry in body-xml is expected to be a XPath v2 expression. In XPath expressions characters like @, /, :, [, ] among others have special meanings.

Using a JSON string

To provide the exclusion JSON document set the variable FUZZAPI_EXCLUDE_PARAMETER_ENV with the JSON string. In the following example, the .gitlab-ci.yml, the FUZZAPI_EXCLUDE_PARAMETER_ENV variable is set to a JSON string:

stages:
     - fuzz

include:
  - template: API-Fuzzing.gitlab-ci.yml

variables:
  FUZZAPI_PROFILE: Quick
  FUZZAPI_OPENAPI: test-api-specification.json
  FUZZAPI_TARGET_URL: http://test-deployment/
  FUZZAPI_EXCLUDE_PARAMETER_ENV: '{ "headers": [ "Upgrade-Insecure-Requests" ] }'

Using a file

To provide the exclusion JSON document, set the variable FUZZAPI_EXCLUDE_PARAMETER_FILE with the JSON file path. The file path is relative to the job current working directory. In the following example .gitlab-ci.yml file, the FUZZAPI_EXCLUDE_PARAMETER_FILE variable is set to a JSON file path:

stages:
     - fuzz

include:
  - template: API-Fuzzing.gitlab-ci.yml

variables:
  FUZZAPI_PROFILE: Quick
  FUZZAPI_OPENAPI: test-api-specification.json
  FUZZAPI_TARGET_URL: http://test-deployment/
  FUZZAPI_EXCLUDE_PARAMETER_FILE: api-fuzzing-exclude-parameters.json

The api-fuzzing-exclude-parameters.json is a JSON document that follows the structure of exclude parameters document.

Exclude URLs

Introduced in GitLab 14.10.

As an alternative to excluding by paths, you can filter by any other component in the URL by using the FUZZAPI_EXCLUDE_URLS CI/CD variable. This variable can be set in your .gitlab-ci.yml file. The variable can store multiple values, separated by commas (,). Each value is a regular expression. Because each entry is a regular expression, an entry such as .* excludes all URLs because it is a regular expression that matches everything.

In your job output you can check if any URLs matched any provided regular expression from FUZZAPI_EXCLUDE_URLS. Matching operations are listed in the Excluded Operations section. Operations listed in the Excluded Operations should not be listed in the Tested Operations section. For example the following portion of a job output:

2021-05-27 21:51:08 [INF] API Security: --[ Tested Operations ]-------------------------
2021-05-27 21:51:08 [INF] API Security: 201 POST http://target:7777/api/users CREATED
2021-05-27 21:51:08 [INF] API Security: ------------------------------------------------
2021-05-27 21:51:08 [INF] API Security: --[ Excluded Operations ]-----------------------
2021-05-27 21:51:08 [INF] API Security: GET http://target:7777/api/messages
2021-05-27 21:51:08 [INF] API Security: POST http://target:7777/api/messages
2021-05-27 21:51:08 [INF] API Security: ------------------------------------------------

NOTE: Each value in FUZZAPI_EXCLUDE_URLS is a regular expression. Characters such as . , * and $ among many others have special meanings in regular expressions.

Examples

Excluding a URL and child resources

The following example excludes the URL http://target/api/auth and its child resources.

variables:
  FUZZAPI_EXCLUDE_URLS: http://target/api/auth

Excluding two URLs and allow their child resources

To exclude the URLs http://target/api/buy and http://target/api/sell but allowing to scan their child resources, for instance: http://target/api/buy/toy or http://target/api/sell/chair. You could use the value http://target/api/buy/$,http://target/api/sell/$. This value is using two regular expressions, each of them separated by a , character. Hence, it contains http://target/api/buy$ and http://target/api/sell$. In each regular expression, the trailing $ character points out where the matching URL should end.

variables:
  FUZZAPI_EXCLUDE_URLS: http://target/api/buy/$,http://target/api/sell/$

Excluding two URLs and their child resources

In order to exclude the URLs: http://target/api/buy and http://target/api/sell, and their child resources. To provide multiple URLs we use the , character as follows:

variables:
  FUZZAPI_EXCLUDE_URLS: http://target/api/buy,http://target/api/sell

Excluding URL using regular expressions

In order to exclude exactly https://target/api/v1/user/create and https://target/api/v2/user/create or any other version (v3,v4, and more). We could use https://target/api/v.*/user/create$, in the previous regular expression . indicates any character and * indicates zero or more times, additionally $ indicates that the URL should end there.

variables:
  FUZZAPI_EXCLUDE_URLS: https://target/api/v.*/user/create$

Header Fuzzing

Header fuzzing is disabled by default due to the high number of false positives that occur with many technology stacks. When header fuzzing is enabled, you must specify a list of headers to include in fuzzing.

Each profile in the default configuration file has an entry for GeneralFuzzingCheck. This check performs header fuzzing. Under the Configuration section, you must change the HeaderFuzzing and Headers settings to enable header fuzzing.

This snippet shows the Quick-10 profile's default configuration with header fuzzing disabled:

- Name: Quick-10
  DefaultProfile: Empty
  Routes:
  - Route: *Route0
    Checks:
    - Name: FormBodyFuzzingCheck
      Configuration:
        FuzzingCount: 10
        UnicodeFuzzing: true
    - Name: GeneralFuzzingCheck
      Configuration:
        FuzzingCount: 10
        UnicodeFuzzing: true
        HeaderFuzzing: false
        Headers:
    - Name: JsonFuzzingCheck
      Configuration:
        FuzzingCount: 10
        UnicodeFuzzing: true
    - Name: XmlFuzzingCheck
      Configuration:
        FuzzingCount: 10
        UnicodeFuzzing: true

HeaderFuzzing is a boolean that turns header fuzzing on and off. The default setting is false for off. To turn header fuzzing on, change this setting to true:

    - Name: GeneralFuzzingCheck
      Configuration:
        FuzzingCount: 10
        UnicodeFuzzing: true
        HeaderFuzzing: true
        Headers:

Headers is a list of headers to fuzz. Only headers listed are fuzzed. To fuzz a header used by your APIs, add an entry for it using the syntax - Name: HeaderName. For example, to fuzz a custom header X-Custom, add - Name: X-Custom:

    - Name: GeneralFuzzingCheck
      Configuration:
        FuzzingCount: 10
        UnicodeFuzzing: true
        HeaderFuzzing: true
        Headers:
          - Name: X-Custom

You now have a configuration to fuzz the header X-Custom. Use the same notation to list additional headers:

    - Name: GeneralFuzzingCheck
      Configuration:
        FuzzingCount: 10
        UnicodeFuzzing: true
        HeaderFuzzing: true
        Headers:
          - Name: X-Custom
          - Name: X-AnotherHeader

Repeat this configuration for each profile as needed.

Running your first scan

When configured correctly, a CI/CD pipeline contains a fuzz stage and an apifuzzer_fuzz or apifuzzer_fuzz_dnd job. The job only fails when an invalid configuration is provided. During normal operation, the job always succeeds even if faults are identified during fuzz testing.

Faults are displayed on the Security pipeline tab with the suite name. When testing against the repositories default branch, the fuzzing faults are also shown on the Security & Compliance's Vulnerability Report page.

To prevent an excessive number of reported faults, the API fuzzing scanner limits the number of faults it reports.

Viewing fuzzing faults

The API Fuzzing analyzer produces a JSON report that is collected and used to populate the faults into GitLab vulnerability screens. Fuzzing faults show up as vulnerabilities with a severity of Unknown.

The faults that API fuzzing finds require manual investigation and aren't associated with a specific vulnerability type. They require investigation to determine if they are a security issue, and if they should be fixed. See handling false positives for information about configuration changes you can make to limit the number of false positives reported.

View details of an API Fuzzing vulnerability

Introduced in GitLab 13.7.

Faults detected by API Fuzzing occur in the live web application, and require manual investigation to determine if they are vulnerabilities. Fuzzing faults are included as vulnerabilities with a severity of Unknown. To facilitate investigation of the fuzzing faults, detailed information is provided about the HTTP messages sent and received along with a description of the modifications made.

Follow these steps to view details of a fuzzing fault:

1. You can view faults in a project, or a merge request:

   • In a project, go to the project's {shield} Security & Compliance > Vulnerability Report page. This page shows all vulnerabilities from the default branch only.
   • In a merge request, go the merge request's Security section and select the Expand button. API Fuzzing faults are available in a section labeled API Fuzzing detected N potential vulnerabilities. Select the title to display the fault details.

2. Select the fault's title to display the fault's details. The table below describes these details.

   Field	Description
   Description	Description of the fault including what was modified.
   Project	Namespace and project in which the vulnerability was detected.
   Method	HTTP method used to detect the vulnerability.
   URL	URL at which the vulnerability was detected.
   Request	The HTTP request that caused the fault.
   Unmodified Response	Response from an unmodified request. This is what a normal working response looks like.
   Actual Response	Response received from fuzzed request.
   Evidence	How we determined a fault occurred.
   Identifiers	The fuzzing check used to find this fault.
   Severity	Severity of the finding is always Unknown.
   Scanner Type	Scanner used to perform testing.

Security Dashboard

Fuzzing faults show up as vulnerabilities with a severity of Unknown. The Security Dashboard is a good place to get an overview of all the security vulnerabilities in your groups, projects and pipelines. For more information, see the Security Dashboard documentation.

Interacting with the vulnerabilities

Fuzzing faults show up as vulnerabilities with a severity of Unknown. Once a fault is found, you can interact with it. Read more on how to address the vulnerabilities.

Handling False Positives

False positives can be handled in two ways:

• Turn off the Check producing the false positive. This prevents the check from generating any faults. Example checks are the JSON Fuzzing Check, and Form Body Fuzzing Check.
• Fuzzing checks have several methods of detecting when a fault is identified, called Asserts. Asserts can also be turned off and configured. For example, the API fuzzer by default uses HTTP status codes to help identify when something is a real issue. If an API returns a 500 error during testing, this creates a fault. This isn't always desired, as some frameworks return 500 errors often.

Turn off a Check

Checks perform testing of a specific type and can be turned on and off for specific configuration profiles. The default configuration file defines several profiles that you can use. The profile definition in the configuration file lists all the checks that are active during a scan. To turn off a specific check, remove it from the profile definition in the configuration file. The profiles are defined in the Profiles section of the configuration file.

Example profile definition:

Profiles:
  - Name: Quick-10
    DefaultProfile: Quick
    Routes:
      - Route: *Route0
        Checks:
          - Name: FormBodyFuzzingCheck
            Configuration:
              FuzzingCount: 10
              UnicodeFuzzing: true
          - Name: GeneralFuzzingCheck
            Configuration:
              FuzzingCount: 10
              UnicodeFuzzing: true
          - Name: JsonFuzzingCheck
            Configuration:
              FuzzingCount: 10
              UnicodeFuzzing: true
          - Name: XmlFuzzingCheck
            Configuration:
              FuzzingCount: 10
              UnicodeFuzzing: true

To turn off the General Fuzzing Check you can remove these lines:

- Name: GeneralFuzzingCheck
  Configuration:
    FuzzingCount: 10
    UnicodeFuzzing: true

This results in the following YAML:

- Name: Quick-10
  DefaultProfile: Quick
  Routes:
    - Route: *Route0
      Checks:
        - Name: FormBodyFuzzingCheck
          Configuration:
            FuzzingCount: 10
            UnicodeFuzzing: true
        - Name: JsonFuzzingCheck
          Configuration:
            FuzzingCount: 10
            UnicodeFuzzing: true
        - Name: XmlFuzzingCheck
          Configuration:
            FuzzingCount: 10
            UnicodeFuzzing: true

Turn off an Assertion for a Check

Assertions detect faults in tests produced by checks. Many checks support multiple Assertions such as Log Analysis, Response Analysis, and Status Code. When a fault is found, the Assertion used is provided. To identify which Assertions are on by default, see the Checks default configuration in the configuration file. The section is called Checks.

This example shows the FormBody Fuzzing Check:

Checks:
  - Name: FormBodyFuzzingCheck
    Configuration:
      FuzzingCount: 30
      UnicodeFuzzing: true
    Assertions:
      - Name: LogAnalysisAssertion
      - Name: ResponseAnalysisAssertion
      - Name: StatusCodeAssertion

Here you can see three Assertions are on by default. A common source of false positives is StatusCodeAssertion. To turn it off, modify its configuration in the Profiles section. This example provides only the other two Assertions (LogAnalysisAssertion, ResponseAnalysisAssertion). This prevents FormBodyFuzzingCheck from using StatusCodeAssertion:

Profiles:
  - Name: Quick-10
    DefaultProfile: Quick
    Routes:
      - Route: *Route0
        Checks:
          - Name: FormBodyFuzzingCheck
            Configuration:
              FuzzingCount: 10
              UnicodeFuzzing: true
            Assertions:
              - Name: LogAnalysisAssertion
              - Name: ResponseAnalysisAssertion
          - Name: GeneralFuzzingCheck
            Configuration:
              FuzzingCount: 10
              UnicodeFuzzing: true
          - Name: JsonFuzzingCheck
            Configuration:
              FuzzingCount: 10
              UnicodeFuzzing: true
          - Name: XmlInjectionCheck
            Configuration:
              FuzzingCount: 10
              UnicodeFuzzing: true

Running API fuzzing in an offline environment

For self-managed GitLab instances in an environment with limited, restricted, or intermittent access to external resources through the internet, some adjustments are required for the Web API Fuzz testing job to successfully run.

Steps:

1. Host the Docker image in a local container registry.
2. Set the SECURE_ANALYZERS_PREFIX to the local container registry.

The Docker image for API Fuzzing must be pulled (downloaded) from the public registry and then pushed (imported) into a local registry. The GitLab container registry can be used to locally host the Docker image. This process can be performed using a special template. See loading Docker images onto your offline host for instructions.

Once the Docker image is hosted locally, the SECURE_ANALYZERS_PREFIX variable is set with the location of the local registry. The variable must be set such that concatenating /api-security:2 results in a valid image location.

For example, the below line sets a registry for the image registry.gitlab.com/security-products/api-security:2:

SECURE_ANALYZERS_PREFIX: "registry.gitlab.com/security-products"

NOTE: Setting SECURE_ANALYZERS_PREFIX changes the Docker image registry location for all GitLab Secure templates.

For more information, see Offline environments.

Troubleshooting

Error waiting for API Security 'http://127.0.0.1:5000' to become available

A bug exists in versions of the API Fuzzing analyzer prior to v1.6.196 that can cause a background process to fail under certain conditions. The solution is to update to a newer version of the DAST API analyzer.

The version information can be found in the job details for the apifuzzer_fuzz job.

If the issue is occurring with versions v1.6.196 or greater, please contact Support and provide the following information:

1. Reference this troubleshooting section and ask for the issue to be escalated to the Dynamic Analysis Team.
2. The full console output of the job.
3. The gl-api-security-scanner.log file available as a job artifact. In the right-hand panel of the job details page, select the Browse button.
4. The apifuzzer_fuzz job definition from your .gitlab-ci.yml file.

Error, the OpenAPI document is not valid. Errors were found during validation of the document using the published OpenAPI schema

At the start of an API Fuzzing job the OpenAPI Specification is validated against the published schema. This error is shown when the provided OpenAPI Specification has validation errors. Errors can be introduced when creating an OpenAPI Specification manually, and also when the schema is generated.

For OpenAPI Specifications that are generated automatically validation errors are often the result of missing code annotations.

Error message

• In GitLab 13.11 and later, Error, the OpenAPI document is not valid. Errors were found during validation of the document using the published OpenAPI schema
  • OpenAPI 2.0 schema validation error ...
  • OpenAPI 3.0.x schema validation error ...

Solution

For generated OpenAPI Specifications

1. Identify the validation errors.
   1. Use the Swagger Editor to identify validation problems in your specification. The visual nature of the Swagger Editor makes it easier to understand what needs to change.
   2. Alternatively, you can check the log output and look for schema validation warnings. They are prefixed with messages such as OpenAPI 2.0 schema validation error or OpenAPI 3.0.x schema validation error. Each failed validation provides extra information about location and description. Note that JSON Schema validation messages might not be easy to understand. This is why we recommend the use of editors to validate schema documents.
2. Review the documentation for the OpenAPI generation your framework/tech stack is using. Identify the changes needed to produce a correct OpenAPI document.
3. Once the validation issues are resolved, re-run your pipeline.

For manually created OpenAPI Specifications

1. Identify the validation errors.
   1. The simplest solution is to use a visual tool to edit and validate the OpenAPI document. For example the Swagger Editor highlights schema errors and possible solutions.
   2. Alternatively, you can check the log output and look for schema validation warnings. They are prefixed with messages such as OpenAPI 2.0 schema validation error or OpenAPI 3.0.x schema validation error. Each failed validation provides extra information about location and description. Correct each of the validation failures and then resubmit the OpenAPI doc. Note that JSON Schema validation message might not be easy to understand. This is why we recommend the use of editors to validate document.
2. Once the validation issues are resolved, re-run your pipeline.

Failed to start scanner session (version header not found)

The API Fuzzing engine outputs an error message when it cannot establish a connection with the scanner application component. The error message is shown in the job output window of the apifuzzer_fuzz job. A common cause of this issue is changing the FUZZAPI_API variable from its default.

Error message

• In GitLab 13.11 and later, Failed to start scanner session (version header not found).
• In GitLab 13.10 and earlier, API Security version header not found. Are you sure that you are connecting to the API Security server?.

Solution

• Remove the FUZZAPI_API variable from the .gitlab-ci.yml file. The value will be inherited from the API Fuzzing CI/CD template. We recommend this method instead of manually setting a value.
• If removing the variable is not possible, check to see if this value has changed in the latest version of the API Fuzzing CI/CD template. If so, update the value in the .gitlab-ci.yml file.

Application cannot determine the base URL for the target API

The API Fuzzing analyzer outputs an error message when it cannot determine the target API after inspecting the OpenAPI document. This error message is shown when the target API has not been set in the .gitlab-ci.ymlfile, it is not available in the environment_url.txt file, and it could not be computed using the OpenAPI document.

There is an order of precedence in which the API Fuzzing analyzer tries to get the target API when checking the different sources. First, it will try to use the FUZZAPI_TARGET_URL. If the environment variable has not been set, then the API Fuzzing analyzer will attempt to use the environment_url.txt file. If there is no file environment_url.txt, the API Fuzzing analyzer will then use the OpenAPI document contents and the URL provided in FUZZAPI_OPENAPI (if a URL is provided) to try to compute the target API.

The best-suited solution will depend on whether or not your target API changes for each deployment. In static environments, the target API is the same for each deployment, in this case please refer to the static environment solution. If the target API changes for each deployment a dynamic environment solution should be applied.

Static environment solution

This solution is for pipelines in which the target API URL doesn't change (is static).

Add environmental variable

For environments where the target API remains the same, we recommend you specify the target URL by using the FUZZAPI_TARGET_URL environment variable. In your .gitlab-ci.yml file, add a variable FUZZAPI_TARGET_URL. The variable must be set to the base URL of API testing target. For example:

include:
    - template: API-Fuzzing.gitlab-ci.yml

  variables:
    FUZZAPI_TARGET_URL: http://test-deployment/
    FUZZAPI_OPENAPI: test-api-specification.json

Dynamic environment solutions

In a dynamic environment your target API changes for each different deployment. In this case, there is more than one possible solution, we recommend to use the environment_url.txt file when dealing with dynamic environments.

Use environment_url.txt

To support dynamic environments in which the target API URL changes during each pipeline, API Fuzzing supports the use of an environment_url.txt file that contains the URL to use. This file is not checked into the repository, instead it's created during the pipeline by the job that deploys the test target and collected as an artifact that can be used by later jobs in the pipeline. The job that creates the environment_url.txt file must run before the API Fuzzing job.

1. Modify the test target deployment job adding the base URL in an environment_url.txt file at the root of your project.
2. Modify the test target deployment job collecting the environment_url.txt as an artifact.

Example:

deploy-test-target:
  script:
    # Perform deployment steps
    # Create environment_url.txt (example)
    - echo http://${CI_PROJECT_ID}-${CI_ENVIRONMENT_SLUG}.example.org > environment_url.txt

  artifacts:
    paths:
      - environment_url.txt

Use OpenAPI with an invalid schema

There are cases where the document is autogenerated with an invalid schema or cannot be edited manually in a timely manner. In those scenarios, the API Security is able to perform a relaxed validation by setting the variable FUZZAPI_OPENAPI_RELAXED_VALIDATION. We recommend providing a fully compliant OpenAPI document to prevent unexpected behaviors.

Edit a non-compliant OpenAPI file

To detect and correct elements that don't comply with the OpenAPI specifications, we recommend using an editor. An editor commonly provides document validation, and suggestions to create a schema-compliant OpenAPI document. Suggested editors include:

If your OpenAPI document is generated manually, load your document in the editor and fix anything that is non-compliant. If your document is generated automatically, load it in your editor to identify the issues in the schema, then go to the application and perform the corrections based on the framework you are using.

Enable OpenAPI relaxed validation

Relaxed validation is meant for cases when the OpenAPI document cannot meet OpenAPI specifications, but it still has enough content to be consumed by different tools. A validation is performed but less strictly in regards to document schema.

API Security can still try to consume an OpenAPI document that does not fully comply with OpenAPI specifications. To instruct API Security to perform a relaxed validation, set the variable FUZZAPI_OPENAPI_RELAXED_VALIDATION to any value, for example:

   stages:
     - fuzz

   include:
     - template: API-Fuzzing.gitlab-ci.yml

   variables:
     FUZZAPI_PROFILE: Quick-10
     FUZZAPI_TARGET_URL: http://test-deployment/
     FUZZAPI_OPENAPI: test-api-specification.json
     FUZZAPI_OPENAPI_RELAXED_VALIDATION: On

No operation in the OpenAPI document is consuming any supported media type

API Security uses the specified media types in the OpenAPI document to generate requests. If no request can be created due to the lack of supported media types, then an error will be thrown.

Error message

• In GitLab 14.10 and later, Error, no operation in the OpenApi document is consuming any supported media type. Check 'OpenAPI Specification' to check the supported media types.

Solution

1. Review the supported media types in the OpenAPI Specification section.
2. Edit your OpenAPI document, allowing at least a given operation to accept any of the supported media types. Alternatively, a supported media type could be set in the OpenAPI document level and get applied to all operations. This step may require changes in your application to ensure the supported media type is accepted by the application.

Get support or request an improvement

To get support for your particular problem please use the getting help channels.

The GitLab issue tracker on GitLab.com is the right place for bugs and feature proposals about API Security and API Fuzzing. Please use ~"Category:API Security" label when opening a new issue regarding API fuzzing to ensure it is quickly reviewed by the right people. Please refer to our review response SLO to understand when you should receive a response.

Search the issue tracker for similar entries before submitting your own, there's a good chance somebody else had the same issue or feature proposal. Show your support with an award emoji and or join the discussion.

When experiencing a behavior not working as expected, consider providing contextual information:

• GitLab version if using a self-managed instance.
• .gitlab-ci.yml job definition.
• Full job console output.
• Scanner log file available as a job artifact named gl-api-security-scanner.log.

WARNING: Sanitize data attached to a support issue. Please remove sensitive information, including: credentials, passwords, tokens, keys, and secrets.

Glossary

• Assert: Assertions are detection modules used by checks to trigger a fault. Many assertions have configurations. A check can use multiple Assertions. For example, Log Analysis, Response Analysis, and Status Code are common Assertions used together by checks. Checks with multiple Assertions allow them to be turned on and off.
• Check: Performs a specific type of test, or performed a check for a type of vulnerability. For example, the JSON Fuzzing Check performs fuzz testing of JSON payloads. The API fuzzer is comprised of several checks. Checks can be turned on and off in a profile.
• Fault: During fuzzing, a failure identified by an Assert is called a fault. Faults are investigated to determine if they are a security vulnerability, a non-security issue, or a false positive. Faults don't have a known vulnerability type until they are investigated. Example vulnerability types are SQL Injection and Denial of Service.
• Profile: A configuration file has one or more testing profiles, or sub-configurations. You may have a profile for feature branches and another with extra testing for a main branch.