Skip to content

Add info about base-uri #213

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 1 commit into from
Jan 14, 2025
Merged

Add info about base-uri #213

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
Binary file added assets/misc/demo_csp_bypass_due_to_no_base_uri_directive.mp4
View file
Open in desktop
Binary file not shown.
14 changes: 11 additions & 3 deletions tab_bestpractices.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -42,7 +42,7 @@ The following section proposes a configuration for the [actively supported and w
| Strict-Transport-Security | `max-age=31536000; includeSubDomains` |
| X-Frame-Options | `deny` |
| X-Content-Type-Options | `nosniff` |
| Content-Security-Policy | `default-src 'self'; form-action 'self'; object-src 'none'; frame-ancestors 'none'; upgrade-insecure-requests; block-all-mixed-content` |
| Content-Security-Policy | `default-src 'self'; form-action 'self'; base-uri 'self'; object-src 'none'; frame-ancestors 'none'; upgrade-insecure-requests; block-all-mixed-content` |
| X-Permitted-Cross-Domain-Policies | `none` |
| Referrer-Policy | `no-referrer` |
| Clear-Site-Data | `"cache","cookies","storage"` |
Expand Down Expand Up @@ -344,22 +344,30 @@ This section describes some points, to keep in mind, during the creation of a [C

🚩 Not every **[directives](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy#directives)** fallback to the **[default-src](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/default-src)** directive when it is not specified in the CSP policy.

## Directive form-action
### Directive form-action

👀 It is the case for the **[form-action](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/form-action)** directive. Therefore, an html form can be used to bypass the CSP in place when the `form-action` is not defined.

📺 This [demonstration video](assets/misc/demo_csp_bypass_due_to_no_form_action_directive.mp4) show an example.

💡 Therefore, ensure to always specify the `form-action` directive in a CSP policy to at least, the `'self'` value, to allow forms only on the current domain.

## Directive frame-ancestors
### Directive frame-ancestors

👀 It is the case for the **[frame-ancestors](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/frame-ancestors)** directive. Therefore, IF it is not defined **AND** IF the header [X-Frame-Options](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Frame-Options) is not/incorrectly specified then the current domain can be embedded into a frame.

📺 This [demonstration video](assets/misc/demo_csp_bypass_due_to_no_frame_ancestors_directive.mp4) show an example.

💡 Therefore, ensure to always specify the `frame-ancestors` directive in a CSP policy to at least, the `'none'` value, to deny the current domain to be "framed".

### Directive base-uri

👀 It is the case for the **[base-uri](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/base-uri)** directive.

📺 This [demonstration video](assets/misc/demo_csp_bypass_due_to_no_base_uri_directive.mp4) show an example.

💡 Therefore, ensure to always specify the `base-uri` directive in a CSP policy to at least, the `'self'` value, to only allow the current domain to be specified as the document's base URI via a `<base href="..." />` html tag.

## Support for a large CSP policy

Tests were performed to identify if any limitation was in place, regarding the definition and usage of a large CSP policy. Tests were performed against the following browsers:
Expand Down
Loading