is using the popular open source tool [OWASP ZAProxy](https://github.com/zaproxy/zaproxy)
to perform an analysis on your running web application.
By default, DAST executes [ZAP Baseline Scan](https://github.com/zaproxy/zaproxy/wiki/ZAP-Baseline-Scan) and will perform passive scanning only. It will not actively attack your application.
However, DAST can be [configured](#full-scan)
to also perform a so-called "active scan". That is, attack your application and produce a more extensive security report.
It can be very useful combined with [Review Apps](../../../ci/review_apps/index.md).
The [`dast`](https://gitlab.com/gitlab-org/security-products/dast/container_registry) Docker image in GitLab container registry is updated on a weekly basis to have all [`owasp2docker-weekly`](https://hub.docker.com/r/owasp/zap2docker-weekly/) updates in it.
It's also possible to authenticate the user before performing the DAST checks:
```yaml
include:
template: DAST.gitlab-ci.yml
variables:
DAST_WEBSITE: https://example.com
DAST_AUTH_URL: https://example.com/sign-in
DAST_USERNAME: john.doe@example.com
DAST_PASSWORD: john-doe-password
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 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](#available-variables) `DAST_FULL_SCAN_DOMAIN_VALIDATION_REQUIRED` to true.
```yaml
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](https://guides.rubyonrails.org/action_controller_overview.html#setting-custom-headers):
```ruby
class DastWebsiteTargetController <ActionController::Base
It's also possible to add the `Gitlab-DAST-Permission` header via a proxy.
###### NGINX
The following config allows NGINX to act as a reverse proxy and add the `Gitlab-DAST-Permission` [header](http://nginx.org/en/docs/http/ngx_http_headers_module.html#add_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](https://httpd.apache.org/docs/2.4/mod/mod_proxy.html)
| `DAST_WEBSITE` | yes | The URL of the website to scan. |
| `DAST_AUTH_URL` | no | The authentication URL of the website to scan. |
| `DAST_USERNAME` | no | The username to authenticate to in the website. |
| `DAST_PASSWORD` | no | The password to authenticate to in the website. |
| `DAST_USERNAME_FIELD` | no | The name of username field at the sign-in HTML form. |
| `DAST_PASSWORD_FIELD` | no | The name of password field at the sign-in HTML form. |
| `DAST_AUTH_EXCLUDE_URLS` | no | The URLs to skip during the authenticated scan; comma-separated, no spaces in between. |
| `DAST_TARGET_AVAILABILITY_TIMEOUT` | no | Time limit in seconds to wait for target availability. Scan is attempted nevertheless if it runs out. Integer. Defaults to `60`. |
| `DAST_FULL_SCAN_ENABLED` | no | Switches the tool to execute [ZAP Full Scan](https://github.com/zaproxy/zaproxy/wiki/ZAP-Full-Scan) instead of [ZAP Baseline Scan](https://github.com/zaproxy/zaproxy/wiki/ZAP-Baseline-Scan). Boolean. `true`, `True`, or `1` are considered as true value, otherwise false. Defaults to `false`. |
| `DAST_FULL_SCAN_DOMAIN_VALIDATION_REQUIRED` | no | Requires [domain validation](#domain-validation) when running DAST full scans. Boolean. `true`, `True`, or `1` are considered as true value, otherwise false. Defaults to `false`. |
