Dynamic Application Security Testing (DAST)

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Running static checks on your code is the first step to detect vulnerabilities that can put the security of your code at risk. Yet, once deployed, your application is exposed to a new category of possible attacks, such as cross-site scripting or broken authentication flaws. This is where Dynamic Application Security Testing (DAST) comes into place.

Overview

If you’re using GitLab CI/CD, you can analyze your running web applications for known vulnerabilities using Dynamic Application Security Testing (DAST). You can take advantage of DAST by either including the CI job in your existing .gitlab-ci.yml file or by implicitly using Auto DAST, provided by Auto DevOps.

GitLab checks the DAST report, compares the found vulnerabilities between the source and target branches, and shows the information on the merge request.

Note: This comparison logic uses only the latest pipeline executed for the target branch’s base commit. Running the pipeline on any other commit has no effect on the merge request.

DAST Widget

By clicking on one of the detected linked vulnerabilities, you can see the details and the URL(s) affected.

DAST Widget Clicked

Dynamic Application Security Testing (DAST) uses the popular open source tool OWASP Zed Attack Proxy to perform an analysis on your running web application.

By default, DAST executes ZAP Baseline Scan and performs passive scanning only. It won’t actively attack your application. However, DAST can be configured to also perform an active scan: attack your application and produce a more extensive security report. It can be very useful combined with Review Apps.

Note: A pipeline may consist of multiple jobs, including SAST and DAST scanning. If any job fails to finish for any reason, the security dashboard won’t show DAST scanner output. For example, if the DAST job finishes but the SAST job fails, the security dashboard won’t show DAST results. The analyzer will output an exit code on failure.

Use cases

It helps you automatically find security vulnerabilities in your running web applications while you’re developing and testing your applications.

Requirements

To run a DAST job, you need GitLab Runner with the docker executor.

Configuration

For GitLab 11.9 and later, to enable DAST, you must include the DAST.gitlab-ci.yml template that’s provided as a part of your GitLab installation. For GitLab versions earlier than 11.9, you can copy and use the job as defined in that template.

Add the following to your .gitlab-ci.yml file:

include:
  - template: DAST.gitlab-ci.yml

variables:
  DAST_WEBSITE: https://example.com

There are two ways to define the URL to be scanned by DAST:

  1. Set the DAST_WEBSITE variable.

  2. Add it in an environment_url.txt file at the root of your project. This is great for testing in dynamic environments. In order to run DAST against an app dynamically created during a GitLab CI/CD pipeline, have the app persist its domain in an environment_url.txt file, and DAST automatically parses that file to find its scan target. You can see an example of this in our Auto DevOps CI YAML.

If both values are set, the DAST_WEBSITE value takes precedence.

The included template creates a dast job in your CI/CD pipeline and scans your project’s source code for possible vulnerabilities.

The results are saved as a DAST report artifact that you can later download and analyze. Due to implementation limitations we always take the latest DAST artifact available. Behind the scenes, the GitLab DAST Docker image is used to run the tests on the specified URL and scan it for possible vulnerabilities.

By default, the DAST template will use the latest major version of the DAST Docker image. Using the DAST_VERSION variable, you can choose how DAST updates:

  • Automatically update DAST with new features and fixes by pinning to a major version (such as 1).
  • Only update fixes by pinning to a minor version (such as 1.6).
  • Prevent all updates by pinning to a specific version (such as 1.6.4).

Find the latest DAST versions on the Releases page.

When DAST scans run

When using DAST.gitlab-ci.yml template, the dast job is run last as shown in the example below. To ensure DAST is scanning the latest code, your CI pipeline should deploy changes to the web server in one of the jobs preceding the dast job.

stages:
  - build
  - test
  - deploy
  - dast

Be aware that if your pipeline is configured to deploy to the same webserver in each run, running a pipeline while another is still running could cause a race condition where one pipeline overwrites the code from another pipeline. The site to be scanned should be excluded from changes for the duration of a DAST scan. The only changes to the site should be from the DAST scanner. Be aware that any changes that users, scheduled tasks, database changes, code changes, other pipelines, or other scanners make to the site during a scan could lead to inaccurate results.

Hide sensitive information

Introduced in GitLab 13.1.

HTTP request and response headers may contain sensitive information, including cookies and authorization credentials. By default, the following headers are masked:

  • Authorization.
  • Proxy-Authorization.
  • Set-Cookie (values only).
  • Cookie (values only).

Using the DAST_MASK_HTTP_HEADERS variable, you can list the headers whose values you want masked. For details on how to mask headers, see Customizing the DAST settings.

Authentication

It’s also possible to authenticate the user before performing the DAST checks.

Create masked variables to pass the credentials that DAST will use. To create masked variables for the username and password, see Create a custom variable in the UI. Note that the key of the username variable must be DAST_USERNAME and the key of the password variable must be DAST_PASSWORD.

Other variables that are related to authenticated scans are:

include:
  - template: DAST.gitlab-ci.yml

variables:
  DAST_WEBSITE: https://example.com
  DAST_AUTH_URL: https://example.com/sign-in
  DAST_USERNAME_FIELD: session[user] # the name of username field at the sign-in HTML form
  DAST_PASSWORD_FIELD: session[password] # the name of password field at the sign-in HTML form
  DAST_AUTH_EXCLUDE_URLS: http://example.com/sign-out,http://example.com/sign-out-2 # optional, URLs to skip during the authenticated scan; comma-separated, no spaces in between

The results will be saved as a DAST report artifact that you can later download and analyze. Due to implementation limitations, we always take the latest DAST artifact available.

Danger: NEVER run an authenticated scan against a production server. When an authenticated scan is run, it may perform any function that the authenticated user can. This includes actions like modifying and deleting data, submitting forms, and following links. Only run an authenticated scan against a test server.

Full scan

DAST can be configured to perform ZAP Full Scan, which includes both passive and active scanning against the same target website:

include:
  - template: DAST.gitlab-ci.yml

variables:
  DAST_FULL_SCAN_ENABLED: "true"

Domain validation

The DAST job can be run anywhere, which means you can accidentally hit live web servers and potentially damage them. You could even take down your production environment. For that reason, you should use domain validation.

Domain validation is not required by default. It can be required by setting the environment variable DAST_FULL_SCAN_DOMAIN_VALIDATION_REQUIRED to "true".

include:
  - template: DAST.gitlab-ci.yml

variables:
  DAST_FULL_SCAN_ENABLED: "true"
  DAST_FULL_SCAN_DOMAIN_VALIDATION_REQUIRED: "true"

Since ZAP full scan actively attacks the target application, DAST sends a ping to the target (normally defined in DAST_WEBSITE or environment_url.txt) beforehand.

  • If DAST_FULL_SCAN_DOMAIN_VALIDATION_REQUIRED is false or unset, the scan will proceed unless the response to the ping includes a Gitlab-DAST-Permission header with a value of deny.
  • If DAST_FULL_SCAN_DOMAIN_VALIDATION_REQUIRED is true, the scan will exit unless the response to the ping includes a Gitlab-DAST-Permission header with a value of allow.

Here are some examples of adding the Gitlab-DAST-Permission header to a response in Rails, Django, and Node (with Express).

Ruby on Rails

Here’s how you would add a custom header in Ruby on Rails:

class DastWebsiteTargetController < ActionController::Base
  def dast_website_target
    response.headers['Gitlab-DAST-Permission'] = 'allow'

    head :ok
  end
end
Django

Here’s how you would add a custom header in Django:

class DastWebsiteTargetView(View):
    def head(self, *args, **kwargs):
      response = HttpResponse()
      response['Gitlab-Dast-Permission'] = 'allow'

      return response
Node (with Express)

Here’s how you would add a custom header in Node (with Express):

app.get('/dast-website-target', function(req, res) {
  res.append('Gitlab-DAST-Permission', 'allow')
  res.send('Respond to DAST ping')
})
Domain validation header via a proxy

It’s also possible to add the Gitlab-DAST-Permission header via a proxy.

NGINX

The following configuration allows NGINX to act as a reverse proxy and add the Gitlab-DAST-Permission header:

# default.conf
server {
    listen 80;
    server_name localhost;

    location / {
        proxy_pass http://test-application;
        add_header Gitlab-DAST-Permission allow;
    }
}
Apache

Apache can also be used as a reverse proxy to add the Gitlab-DAST-Permission header.

To do so, add the following lines to httpd.conf:

# httpd.conf
LoadModule proxy_module modules/mod_proxy.so
LoadModule proxy_connect_module modules/mod_proxy_connect.so
LoadModule proxy_http_module modules/mod_proxy_http.so

<VirtualHost *:80>
  ProxyPass "/" "http://test-application.com/"
  ProxyPassReverse "/" "http://test-application.com/"
  Header set Gitlab-DAST-Permission "allow"
</VirtualHost>

This snippet contains a complete httpd.conf file configured to act as a remote proxy and add the Gitlab-DAST-Permission header.

API scan

Using an API specification as a scan’s target is a useful way to seed URLs for scanning an API. Vulnerability rules in an API scan are different than those in a normal website scan.

Specification format

API scans support OpenAPI V2 and OpenAPI V3 specifications. You can define these specifications using JSON or YAML.

Import API specification from a URL

If your API specification is accessible at a URL, you can pass that URL in directly as the target. The specification does not have to be hosted on the same host as the API being tested.

include:
  - template: DAST.gitlab-ci.yml

variables:
  DAST_API_SPECIFICATION: http://my.api/api-specification.yml

Import API specification from a file

If your API specification is in your repository, you can provide the specification’s filename directly as the target. The specification file is expected to be in the /zap/wrk directory.

dast:
  script:
    - mkdir -p /zap/wrk
    - cp api-specification.yml /zap/wrk/api-specification.yml
    - /analyze -t $DAST_WEBSITE
  variables:
    GIT_STRATEGY: fetch
    DAST_API_SPECIFICATION: api-specification.yml

Full scan

API scans support full scanning, which can be enabled by using the DAST_FULL_SCAN_ENABLED environment variable. Domain validation is not supported for full API scans.

Host override

Specifications often define a host, which contains a domain name and a port. The host referenced may be different than the host of the API’s review instance. This can cause incorrect URLs to be imported, or a scan on an incorrect host. Use the DAST_API_HOST_OVERRIDE environment variable to override these values.

For example, with a OpenAPI V3 specification containing:

servers:
  - url: https://api.host.com

If the test version of the API is running at https://api-test.host.com, then the following DAST configuration can be used:

include:
  - template: DAST.gitlab-ci.yml

variables:
  DAST_API_SPECIFICATION: http://api-test.host.com/api-specification.yml
  DAST_API_HOST_OVERRIDE: api-test.host.com

Note that DAST_API_HOST_OVERRIDE is only applied to specifications imported by URL.

Authentication using headers

Tokens in request headers are often used as a way to authenticate API requests. You can achieve this by using the DAST_REQUEST_HEADERS environment variable. Headers are applied to every request DAST makes.

include:
  - template: DAST.gitlab-ci.yml

variables:
  DAST_API_SPECIFICATION: http://api-test.api.com/api-specification.yml
  DAST_REQUEST_HEADERS: "Authorization: Bearer my.token"

Customizing the DAST settings

Deprecation: Beginning in GitLab 13.0, the use of only and except is no longer supported. When overriding the template, you must use rules instead.

The DAST settings can be changed through environment variables by using the variables parameter in .gitlab-ci.yml. These variables are documented in available variables.

For example:

include:
  - template: DAST.gitlab-ci.yml

variables:
  DAST_WEBSITE: https://example.com
  DAST_SPIDER_MINS: 120

Because the template is evaluated before the pipeline configuration, the last mention of the variable will take precedence.

Available variables

DAST can be configured using environment variables.

Environment variable Type Description
SECURE_ANALYZERS_PREFIX URL Set the Docker registry base address from which to download the analyzer.
DAST_WEBSITE URL The URL of the website to scan. DAST_API_SPECIFICATION must be specified if this is omitted.
DAST_API_SPECIFICATION URL or string The API specification to import. The specification can be hosted at a URL, or the name of a file present in the /zap/wrk directory. DAST_WEBSITE must be specified if this is omitted.
DAST_AUTH_URL URL The URL of the page containing the sign-in HTML form on the target website. DAST_USERNAME and DAST_PASSWORD will be submitted with the login form to create an authenticated scan. Not supported for API scans.
DAST_USERNAME string The username to authenticate to in the website.
DAST_PASSWORD string The password to authenticate to in the website.
DAST_USERNAME_FIELD string The name of username field at the sign-in HTML form.
DAST_PASSWORD_FIELD string The name of password field at the sign-in HTML form.
DAST_MASK_HTTP_HEADERS string Comma-separated list of request and response headers to be masked (introduced in GitLab 13.1). Must contain all headers to be masked. Refer to list of headers that are masked by default.
DAST_AUTH_EXCLUDE_URLS URLs The URLs to skip during the authenticated scan; comma-separated, no spaces in between. Not supported for API scans.
DAST_FULL_SCAN_ENABLED boolean Set to true to run a ZAP Full Scan instead of a ZAP Baseline Scan. Default: false
DAST_FULL_SCAN_DOMAIN_VALIDATION_REQUIRED boolean Set to true to require domain validation when running DAST full scans. Not supported for API scans. Default: false
DAST_AUTO_UPDATE_ADDONS boolean ZAP add-ons are pinned to specific versions in the DAST Docker image. Set to true to download the latest versions when the scan starts. Default: false
DAST_API_HOST_OVERRIDE string Used to override domains defined in API specification files. Example: example.com:8080
DAST_EXCLUDE_RULES string Set to a comma-separated list of Vulnerability Rule IDs to exclude them from running during the scan. Rule IDs are numbers and can be found from the DAST log or on the ZAP project. For example, HTTP Parameter Override has a rule ID of 10026. Note: In earlier versions of GitLab the excluded rules were executed but alerts they generated were supressed. Introduced in GitLab 12.10.
DAST_REQUEST_HEADERS string Set to a comma-separated list of request header names and values. Headers will be added to every request made by DAST. For example, Cache-control: no-cache,User-Agent: DAST/1.0
DAST_DEBUG boolean Enable debug message output. Default: false
DAST_SPIDER_MINS number The maximum duration of the spider scan in minutes. Set to 0 for unlimited. Default: One minute, or unlimited when the scan is a full scan.
DAST_HTML_REPORT string The file name of the HTML report written at the end of a scan.
DAST_MARKDOWN_REPORT string The file name of the Markdown report written at the end of a scan.
DAST_XML_REPORT string The file name of the XML report written at the end of a scan.
DAST_INCLUDE_ALPHA_VULNERABILITIES boolean Set to true to include alpha passive and active scan rules. Default: false
DAST_USE_AJAX_SPIDER boolean Set to true to use the AJAX spider in addition to the traditional spider, useful for crawling sites that require JavaScript. Default: false
DAST_ZAP_CLI_OPTIONS string ZAP server command-line options. For example, -Xmx3072m would set the Java maximum memory allocation pool size.
DAST_ZAP_LOG_CONFIGURATION string Set to a semicolon-separated list of additional log4j properties for the ZAP Server. For example, log4j.logger.org.parosproxy.paros.network.HttpSender=DEBUG;log4j.logger.com.crawljax=DEBUG

DAST command-line options

Not all DAST configuration is available via environment variables. To find out all possible options, run the following configuration. Available command-line options will be printed to the job log:

include:
  template: DAST.gitlab-ci.yml

dast:
  script:
    - /analyze --help

You must then overwrite the script command to pass in the appropriate argument. For example, passive scanning can be delayed using option -D. The following configuration delays passive scanning by five minutes:

include:
  template: DAST.gitlab-ci.yml

dast:
  script:
    - export DAST_WEBSITE=${DAST_WEBSITE:-$(cat environment_url.txt)}
    - /analyze -D 300 -t $DAST_WEBSITE

Custom ZAProxy configuration

The ZAProxy server contains many useful configurable values. Many key/values for -config remain undocumented, but there is an untested list of possible keys. Note that these options are not supported by DAST, and may break the DAST scan when used. An example of how to rewrite the Authorization header value with TOKEN follows:

include:
  template: DAST.gitlab-ci.yml

variables:
  DAST_ZAP_CLI_OPTIONS: "-config replacer.full_list(0).description=auth -config replacer.full_list(0).enabled=true -config replacer.full_list(0).matchtype=REQ_HEADER -config replacer.full_list(0).matchstr=Authorization -config replacer.full_list(0).regex=false -config replacer.full_list(0).replacement=TOKEN"

Cloning the project’s repository

The DAST job does not require the project’s repository to be present when running, so by default GIT_STRATEGY is set to none.

Debugging DAST jobs

A DAST job has two executing processes:

  • The ZAP server.
  • A series of scripts that start, control and stop the ZAP server.

Debug mode of the scripts can be enabled by using the DAST_DEBUG environment variable. This can help when troubleshooting the job, and will output statements indicating what percentage of the scan is complete. For details on using variables, see Overriding the DAST template.

Debug mode of the ZAP server can be enabled using the DAST_ZAP_LOG_CONFIGURATION environment variable. The following table outlines examples of values that can be set and the effect that they have on the output that is logged. Multiple values can be specified, separated by semicolons.

Log configuration value Effect
log4j.rootLogger=DEBUG Enable all debug logging statements.
log4j.logger.org.apache.commons.httpclient=DEBUG Log every HTTP request and response made by the ZAP server.
log4j.logger.org.zaproxy.zap.spider.SpiderController=DEBUG Log URLs found during the spider scan of the target.
log4j.logger.com.crawljax=DEBUG Enable Ajax Crawler debug logging statements.
log4j.logger.org.parosproxy.paros=DEBUG Enable ZAP server proxy debug logging statements.
log4j.logger.org.zaproxy.zap=DEBUG Enable debug logging statements of the general ZAP server code.

Running DAST 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 DAST job to successfully run. For more information, see Offline environments.

Requirements for offline DAST support

To use DAST in an offline environment, you need:

Note: GitLab Runner has a default pull policy of always, meaning the Runner tries to pull Docker images from the GitLab container registry even if a local copy is available. GitLab Runner’s pull_policy can be set to if-not-present in an offline environment if you prefer using only locally available Docker images. However, we recommend keeping the pull policy setting to always if not in an offline environment, as this enables the use of updated scanners in your CI/CD pipelines.

Make GitLab DAST analyzer images available inside your Docker registry

For DAST, import the following default DAST analyzer image from registry.gitlab.com to your local Docker container registry:

  • registry.gitlab.com/gitlab-org/security-products/dast:latest

The process for importing Docker images into a local offline Docker registry depends on your network security policy. Please consult your IT staff to find an accepted and approved process by which external resources can be imported or temporarily accessed. Note that these scanners are updated periodically with new definitions, so consider if you’re able to make periodic updates yourself.

For details on saving and transporting Docker images as a file, see Docker’s documentation on docker save, docker load, docker export, and docker import.

Set DAST CI job variables to use local DAST analyzers

Add the following configuration to your .gitlab-ci.yml file. You must replace image to refer to the DAST Docker image hosted on your local Docker container registry:

include:
  - template: DAST.gitlab-ci.yml
dast:
  image: registry.example.com/namespace/dast:latest

The DAST job should now use local copies of the DAST analyzers to scan your code and generate security reports without requiring internet access.

Alternatively, you can use the variable SECURE_ANALYZERS_PREFIX to override the base registry address of the dast image.

On-Demand Scans

Version history
  • Introduced in GitLab 13.2.
  • It’s deployed behind a feature flag, disabled by default.
  • It’s disabled on GitLab.com.
  • It’s able to be enabled or disabled per-project.
  • To use it in GitLab self-managed instances, ask a GitLab administrator to enable it.

Passive DAST scans may be run on demand against a target website, outside the DevOps lifecycle. These scans are always associated with the default or master branch of your project and the results can be seen in the project dashboard.

Note: You cannot run an on-demand DAST scan against a protected branch unless you have permission to do so. The master branch is protected by default. For more details, see Pipeline security on protected branches.

DAST On-Demand Scan

Enable or disable On-Demand Scans

On-Demand Scans is under development and not ready for production use. It is deployed behind a feature flag that is disabled by default. GitLab administrators with access to the GitLab Rails console can enable it for your instance. On-Demand Scans can be enabled or disabled per-project

To enable it:

# Instance-wide
Feature.enable(:security_on_demand_scans_feature_flag)
# or by project
Feature.enable(:security_on_demand_scans_feature_flag, Project.find(<project id>))

To disable it:

# Instance-wide
Feature.disable(:security_on_demand_scans_feature_flag)
# or by project
Feature.disable(:security_on_demand_scans_feature_flag, Project.find(<project id>))

Reports

The DAST tool outputs a report file in JSON format by default. However, this tool can also generate reports in Markdown, HTML, and XML. For more information, see the schema for DAST reports.

List of URLs scanned

When DAST completes scanning, the merge request page states the number of URLs scanned. Click View details to view the web console output which includes the list of scanned URLs.

DAST Widget

JSON

Caution: The JSON report artifacts are not a public API of DAST and their format is expected to change in the future.

The DAST tool always emits a JSON report file called gl-dast-report.json and sample reports can be found in the DAST repository.

There are two formats of data in the JSON report that are used side by side:

  • The proprietary ZAP format that will be eventually deprecated.
  • A common format that will be the default in the future.

Other formats

Reports can also be generated in Markdown, HTML, and XML. These can be published as artifacts using the following configuration:

include:
  template: DAST.gitlab-ci.yml

dast:
  variables:
    DAST_HTML_REPORT: report.html
    DAST_MARKDOWN_REPORT: report.md
    DAST_XML_REPORT: report.xml
  artifacts:
    paths:
      - $DAST_HTML_REPORT
      - $DAST_MARKDOWN_REPORT
      - $DAST_XML_REPORT
      - gl-dast-report.json

Security Dashboard

The Security Dashboard is a good place to get an overview of all the security vulnerabilities in your groups, projects and pipelines. Read more about the Security Dashboard.

Bleeding-edge vulnerability definitions

ZAP first creates rules in the alpha class. After a testing period with the community, they are promoted to beta. DAST uses beta definitions by default. To request alpha definitions, use the DAST_INCLUDE_ALPHA_VULNERABILITIES environment variable as shown in the following configuration:

include:
  template: DAST.gitlab-ci.yml

variables:
  DAST_INCLUDE_ALPHA_VULNERABILITIES: true

Interacting with the vulnerabilities

Once a vulnerability is found, you can interact with it. Read more on how to interact with the vulnerabilities.

Vulnerabilities database update

For more information about the vulnerabilities database update, check the maintenance table.

Optimizing DAST

By default, DAST will download all artifacts defined by previous jobs in the pipeline. If your DAST job does not rely on environment_url.txt to define the URL under test or any other files created in previous jobs, we recommend you don’t download artifacts. To avoid downloading artifacts, add the following to your gitlab-ci.yml file:

dast:
   dependencies: []

Troubleshooting

Running out of memory

By default, ZAProxy, which DAST relies on, is allocated memory that sums to 25% of the total memory on the host. Since it keeps most of its information in memory during a scan, it’s possible for DAST to run out of memory while scanning large applications. This results in the following error:

[zap.out] java.lang.OutOfMemoryError: Java heap space

Fortunately, it’s straightforward to increase the amount of memory available for DAST by using the DAST_ZAP_CLI_OPTIONS environment variable:

include:
  - template: DAST.gitlab-ci.yml

variables:
  DAST_ZAP_CLI_OPTIONS: "-Xmx3072m"

Here, DAST is being allocated 3072 MB. Change the number after -Xmx to the required memory amount.