@httpland/csp-middleware
v1.0.0
Published
HTTP content security policy(CSP) middleware
Downloads
3
Maintainers
Readme
csp-middleware
HTTP content security policy(CSP) middleware.
Compliant with Content Security Policy Level 3.
Middleware
For a definition of Universal HTTP middleware, see the http-middleware project.
Usage
Middleware adds the Content-Security-Policy
header to the response.
import {
csp,
type Handler,
} from "https://deno.land/x/csp_middleware@$VERSION/mod.ts";
import { assert } from "https://deno.land/std/testing/asserts.ts";
declare const request: Request;
declare const handler: Handler;
const middleware = csp();
const response = await middleware(request, handler);
assert(response.headers.has("content-security-policy"));
yield:
Content-Security-Policy: default-src 'none'; script-src 'self'; connect-src 'self'; img-src 'self'; style-src 'self'; base-uri 'self'; form-action 'self'
The default header field value is compliant with Content Security Policy (CSP) Quick Reference Guide, Stater policy.
Options
Middleware factory takes following fields.
| Name | Type | Description |
| ---------- | --------------- | -------------------------------------- |
| directives | CSPDirectives
| CSP directives. |
| reportOnly | boolean
| Whether the policy report only or not. |
Directives
directives
can be one of the following.
CSPDirective
- Camel casing
CSPDirective
CSP directives
CSPDirectives
are structured Content-Security-Policy
header field objects.
Base types are as follows:
interface Directives {
[k: string]: string | string[];
}
Each key represents a directive name and each value represents a directive value.
The Directive supports all directives in Content Security Policy Level 3.
Each directive may be restricted to a more strict type.
For example, a webrtc
directive is restricted to 'allow'
or 'block'
.
import { csp } from "https://deno.land/x/csp_middleware@$VERSION/middleware.ts";
const middleware = csp({
directives: {
"default-src": "'none'",
webrtc: "'allow'",
},
});
Check deno doc
for about CSPDirectives
.
Camel casing
The directive name can also be defined in camel case. Overloading makes it exclusive.
import { csp } from "https://deno.land/x/csp_middleware@$VERSION/middleware.ts";
const middleware = csp({
directives: {
defaultSrc: "'none'",
scriptSrc: ["'self'", "*.example.test"],
},
});
Report Only
The header field changes depending on the value of reportOnly
.
| Value | Header field |
| ------- | ----------------------------------- |
| true
| Content-Security-Policy-Report-Only |
| false
| Content-Security-Policy |
The default reportOnly
is false
.
import {
csp,
type Handler,
} from "https://deno.land/x/csp_middleware@$VERSION/mod.ts";
import { assert } from "https://deno.land/std/testing/asserts.ts";
declare const request: Request;
declare const handler: Handler;
const middleware = csp({ reportOnly: true });
const response = await middleware(request, handler);
assert(response.headers.has("content-security-policy-report-only"));
Serialization error
CSP directives will serialize into string.
In Serialization, the directive name and directive value are validated based on ABNF. If they are invalid, an error may be thrown.
Errors are thrown in the following cases:
- None of the
directive
is present - Directive key does not compliant with
<directive-name>
- Directive value does not compliant with
<VCHAR>
without ";" and "," - Directive values has a duplicate value
import { csp } from "https://deno.land/x/csp_middleware@$VERSION/middleware.ts";
import { assertThrows } from "https://deno.land/std/testing/asserts.ts";
assertThrows(() => csp({ directives: {} }));
assertThrows(() => csp({ directives: { defaultSrc: "<invalid>" } }));
assertThrows(() =>
csp({ directives: { defaultSrc: ["<duplicate>", "<duplicate>"] } })
);
Effects
Middleware may make changes to the following elements of the HTTP message.
- HTTP Headers
- Content-Security-Policy
- Content-Security-Policy-Report-Only
Conditions
Middleware will execute if all of the following conditions are met:
Depends on reportOnly:
Content-Security-Policy
header does not exists in responseContent-Security-Policy-Report-Only
header does not exists in response
API
All APIs can be found in the deno doc.
License
Copyright © 2023-present httpland.
Released under the MIT license