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import type { Algorithm, AlgorithmInput } from "./_algorithm.ts";
import * as base64url from "../encoding/base64url.ts";
import { encodeToString as convertUint8ArrayToHex } from "../encoding/hex.ts";
import {
create as createSignature,
verify as verifySignature,
} from "./_signature.ts";
import { verify as verifyAlgorithm } from "./_algorithm.ts";
/*
* JWT §4.1: The following Claim Names are registered in the IANA
* "JSON Web Token Claims" registry established by Section 10.1. None of the
* claims defined below are intended to be mandatory to use or implement in all
* cases, but rather they provide a starting point for a set of useful,
* interoperable claims.
* Applications using JWTs should define which specific claims they use and when
* they are required or optional.
*/
export interface PayloadObject {
iss?: string;
sub?: string;
aud?: string[] | string;
exp?: number;
nbf?: number;
iat?: number;
jti?: string;
[key: string]: unknown;
}
export type Payload = PayloadObject | string;
/*
* JWS §4.1.1: The "alg" value is a case-sensitive ASCII string containing a
* StringOrURI value. This Header Parameter MUST be present and MUST be
* understood and processed by implementations.
*/
export interface Header {
alg: Algorithm;
[key: string]: unknown;
}
const encoder = new TextEncoder();
const decoder = new TextDecoder();
/*
* JWT §4.1.4: Implementers MAY provide for some small leeway to account for
* clock skew.
*/
function isExpired(exp: number, leeway = 0): boolean {
return exp + leeway < Date.now() / 1000;
}
function tryToParsePayload(input: string): unknown {
try {
return JSON.parse(input);
} catch {
return input;
}
}
/**
* Decodes a token into an { header, payload, signature } object.
* @param token
*/
export function decode(
token: string,
): {
header: Header;
payload: unknown;
signature: string;
} {
const parsedArray = token
.split(".")
.map(base64url.decode)
.map((uint8Array, index) => {
switch (index) {
case 0:
try {
return JSON.parse(decoder.decode(uint8Array));
} catch {
break;
}
case 1:
return tryToParsePayload(decoder.decode(uint8Array));
case 2:
return convertUint8ArrayToHex(uint8Array);
}
throw TypeError("The serialization is invalid.");
});
const [header, payload, signature] = parsedArray;
if (
!(
(typeof signature === "string" &&
typeof header?.alg === "string") && payload?.exp !== undefined
? typeof payload.exp === "number"
: true
)
) {
throw new Error(`The token is invalid.`);
}
if (
typeof payload?.exp === "number" &&
isExpired(payload.exp)
) {
throw RangeError("The token is expired.");
}
return {
header,
payload,
signature,
};
}
export type VerifyOptions = {
algorithm?: AlgorithmInput;
};
/**
* Verifies a token.
* @param token
* @param key
* @param object with property 'algorithm'
*/
export async function verify(
token: string,
key: string,
{ algorithm = "HS512" }: VerifyOptions = {},
): Promise<unknown> {
const { header, payload, signature } = decode(token);
if (!verifyAlgorithm(algorithm, header.alg)) {
throw new Error(
`The token's algorithm does not match the specified algorithm '${algorithm}'.`,
);
}
/*
* JWS §4.1.11: The "crit" (critical) Header Parameter indicates that
* extensions to this specification and/or [JWA] are being used that MUST be
* understood and processed.
*/
if ("crit" in header) {
throw new Error(
"The 'crit' header parameter is currently not supported by this module.",
);
}
if (
!(await verifySignature({
signature,
key,
algorithm: header.alg,
signingInput: token.slice(0, token.lastIndexOf(".")),
}))
) {
throw new Error(
"The token's signature does not match the verification signature.",
);
}
return payload;
}
/*
* JSW §7.1: The JWS Compact Serialization represents digitally signed or MACed
* content as a compact, URL-safe string. This string is:
* BASE64URL(UTF8(JWS Protected Header)) || '.' ||
* BASE64URL(JWS Payload) || '.' ||
* BASE64URL(JWS Signature)
*/
function createSigningInput(header: Header, payload: Payload): string {
return `${
base64url.encode(
encoder.encode(JSON.stringify(header)),
)
}.${
base64url.encode(
encoder.encode(
typeof payload === "string" ? payload : JSON.stringify(payload),
),
)
}`;
}
/**
* Creates a token.
* @param payload
* @param key
* @param object with property 'header'
*/
export async function create(
payload: Payload,
key: string,
{
header = { alg: "HS512", typ: "JWT" },
}: {
header?: Header;
} = {},
): Promise<string> {
const signingInput = createSigningInput(header, payload);
const signature = await createSignature(header.alg, key, signingInput);
return `${signingInput}.${signature}`;
}
|
