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Dealing with untrusted content - resolves #456
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,195 @@ | ||
| /* | ||
| Copyright 2023 The Matrix.org Foundation C.I.C. | ||
| Licensed under the Apache License, Version 2.0 (the "License"); | ||
| you may not use this file except in compliance with the License. | ||
| You may obtain a copy of the License at | ||
| http://www.apache.org/licenses/LICENSE-2.0 | ||
| Unless required by applicable law or agreed to in writing, software | ||
| distributed under the License is distributed on an "AS IS" BASIS, | ||
| WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| See the License for the specific language governing permissions and | ||
| limitations under the License. | ||
| */ | ||
|
|
||
| /** | ||
| * Utilities to deal with untrusted values coming from Matrix events. | ||
| * | ||
| * e.g. to confirm that a value `foo` has type `{ bar: string[]}`, | ||
| * run | ||
| * ```ts | ||
| * new SubTypeObjectContent({ | ||
| * bar: STRING_CONTENT.array() | ||
| * }).check_type(value) | ||
| * ``` | ||
| */ | ||
|
|
||
| /** | ||
| * The abstract root class for all content we wish to validate against. | ||
| */ | ||
| abstract class AbstractContent { | ||
| /** | ||
| * Validate the type of a value against `this`. | ||
| * @param value | ||
| */ | ||
| abstract checkType(value: any): boolean; | ||
|
|
||
| /** | ||
| * If `value` has `this` type, return `value`, otherwise | ||
| * return `defaults()`. | ||
| */ | ||
| fallback(value: any, defaults: () => any): any { | ||
| if (this.checkType(value)) { | ||
| return value; | ||
| } | ||
| return defaults(); | ||
| } | ||
|
|
||
| /** | ||
| * Return an `AbstractContent` for values of type `this | null | undefined`. | ||
| */ | ||
| optional(): AbstractContent { | ||
| return new OptionalContent(this); | ||
| } | ||
|
|
||
| /** | ||
| * Return a `AbstractContent` for values of type `this[]`. | ||
| * | ||
| * This is a shortcut for `new OptionalContent(this)` | ||
| */ | ||
| array(): AbstractContent { | ||
| return new ArrayContent(this); | ||
| } | ||
| }; | ||
|
|
||
| /** | ||
| * A content validator for numbers. | ||
| */ | ||
| class StringContent extends AbstractContent { | ||
| /** | ||
| * Check that `value` is a string. | ||
| */ | ||
| checkType(value: any): boolean { | ||
| return typeof value === "string"; | ||
| } | ||
| }; | ||
| /** | ||
| * A content validator for strings (singleton). | ||
| */ | ||
| export const STRING_CONTENT = new StringContent(); | ||
|
|
||
|
|
||
| /** | ||
| * A content validator for numbers. | ||
| */ | ||
| class NumberContent extends AbstractContent { | ||
| checkType(value: any): boolean { | ||
| return typeof value === "number"; | ||
| } | ||
| }; | ||
|
|
||
| /** | ||
| * A content validator for numbers (singleton). | ||
| */ | ||
| export const NUMBER_CONTENT = new NumberContent(); | ||
|
|
||
| /** | ||
| * A content validator for arrays. | ||
| */ | ||
| class ArrayContent extends AbstractContent { | ||
| constructor(public readonly content: AbstractContent) { | ||
| super() | ||
| } | ||
| /** | ||
| * Check that `value` is an array and that each value it contains | ||
| * has type `type.content`. | ||
| */ | ||
| checkType(value: any): boolean { | ||
| if (!Array.isArray(value)) { | ||
| return false; | ||
| } | ||
| for (let item of value) { | ||
| if (!this.content.checkType(item)) { | ||
| return false; | ||
| } | ||
| } | ||
| return true; | ||
| } | ||
| } | ||
| class OptionalContent extends AbstractContent { | ||
| constructor(public readonly content: AbstractContent) { | ||
| super() | ||
| } | ||
| optional(): AbstractContent { | ||
| return this; | ||
| } | ||
| /** | ||
| * Check that value either has type `this.content` or is `null` or `undefined`. | ||
| */ | ||
| checkType(value: any): boolean { | ||
| if (typeof value === "undefined") { | ||
| return true; | ||
| } | ||
| if (value === null) { | ||
| return true; | ||
| } | ||
| if (this.content.checkType(value)) { | ||
| return true; | ||
| } | ||
| return false; | ||
| } | ||
| } | ||
| export class SubTypeObjectContent extends AbstractContent { | ||
| constructor(public readonly fields: Record<string, AbstractContent>) { | ||
| super() | ||
| } | ||
| /** | ||
| * Check that `value` contains **at least** the fields of `this.fields` | ||
| * and that each field specified in `this.fields` holds a value that | ||
| * matches the type specified in `this.fields`. | ||
| */ | ||
| checkType(value: any): boolean { | ||
| if (typeof value !== "object") { | ||
| return false; | ||
| } | ||
| if (value === null) { | ||
| // Let's not forget that `typeof null === "object"` | ||
| return false; | ||
| } | ||
| if (Array.isArray(value)) { | ||
| // Let's not forget that `typeof [...] === "object"` | ||
| return false; | ||
| } | ||
| for (let [k, expected] of Object.entries(this.fields)) { | ||
| if (!expected.checkType(value[k])) { | ||
| return false; | ||
| } | ||
| } | ||
| return true; | ||
| } | ||
| } | ||
|
|
||
| export class ExactTypeObjectContent extends SubTypeObjectContent { | ||
| constructor(public readonly fields: Record<string, AbstractContent>) { | ||
| super(fields) | ||
| } | ||
| /** | ||
| * Check that `value` contains **exactly** the fields of `this.fields` | ||
| * and that each field specified in `this.fields` holds a value that | ||
| * matches the type specified in `this.fields`. | ||
| */ | ||
| checkType(value: any): boolean { | ||
| if (!super.checkType(value)) { | ||
| return false; | ||
| } | ||
| // Check that we don't have any field we're not expecting. | ||
| for (let k of Object.keys(value)) { | ||
| if (!(k in this.fields)) { | ||
| return false; | ||
| } | ||
| } | ||
| return true; | ||
| } | ||
| } |
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