Initial commit

2021-02-04 12:02:42 +01:00
commit 6a17fb6be2
3 changed files with 195 additions and 0 deletions
--- a/index.js
+++ b/index.js
@@ -0,0 +1,102 @@
+class Base64URL {
+    static parse(s) {
+        return new Uint8Array(Array.prototype.map.call(atob(s.replace(/-/g, '+').replace(/_/g, '/').replace(/\s/g, '')), c => c.charCodeAt(0)))
+    }
+    static stringify(a) {
+        return btoa(String.fromCharCode.apply(0, a)).replace(/=/g, '').replace(/\+/g, '-').replace(/\//g, '_')
+    }
+}
+
+class JWT {
+    constructor() {
+        if (!crypto || !crypto.subtle)
+            throw new Error('Crypto not supported!')
+        this.algorithms = {
+            HS256: {
+                name: 'HMAC',
+                hash: {
+                    name: 'SHA-256'
+                }
+            },
+            HS512: {
+                name: 'HMAC',
+                hash: {
+                    name: 'SHA-512'
+                }
+            }
+        }
+    }
+    utf8ToUint8Array(str) {
+        const chars = []
+        str = btoa(unescape(encodeURIComponent(str)))
+        return Base64URL.parse(str)
+    }
+    async sign(payload, secret, alg = 'HS256') {
+        if (payload === null || typeof payload !== 'object')
+            throw new Error('payload must be an object')
+        if (typeof secret !== 'string')
+            throw new Error('secret must be a string')
+        if (typeof alg !== 'string')
+            throw new Error('alg must be a string')
+        const importAlgorithm = this.algorithms[alg]
+        if (!importAlgorithm)
+            throw new Error('algorithm not found')
+        const payloadAsJSON = JSON.stringify(payload)
+        const partialToken = `${Base64URL.stringify(this.utf8ToUint8Array(JSON.stringify({ alg, typ: 'JWT' })))}.${Base64URL.stringify(this.utf8ToUint8Array(payloadAsJSON))}`
+        const key = await crypto.subtle.importKey('raw', this.utf8ToUint8Array(secret), importAlgorithm, false, ['sign'])
+        const characters = payloadAsJSON.split('')
+        const it = this.utf8ToUint8Array(payloadAsJSON).entries()
+        let i = 0
+        const result = []
+        let current
+        while (!(current = it.next()).done) {
+            result.push([current.value[1], characters[i]])
+            i++
+        }
+        const signature = await crypto.subtle.sign(importAlgorithm.name, key, this.utf8ToUint8Array(partialToken))
+        return `${partialToken}.${Base64URL.stringify(new Uint8Array(signature))}`
+    }
+    async verify(token, secret, alg = 'HS256') {
+        if (typeof token !== 'string')
+            throw new Error('token must be a string')
+        if (typeof secret !== 'string')
+            throw new Error('secret must be a string')
+        if (typeof alg !== 'string')
+            throw new Error('alg must be a string')
+        const tokenParts = token.split('.')
+        if (tokenParts.length !== 3)
+            throw new Error('token must have 3 parts')
+        const importAlgorithm = this.algorithms[alg]
+        if (!importAlgorithm)
+            throw new Error('algorithm not found')
+        const keyData = this.utf8ToUint8Array(secret)
+        const key = await crypto.subtle.importKey('raw', keyData, importAlgorithm, false, ['sign'])
+        const partialToken = tokenParts.slice(0, 2).join('.')
+        const signaturePart = tokenParts[2]
+        const messageAsUint8Array = this.utf8ToUint8Array(partialToken)
+        const res = await crypto.subtle.sign(importAlgorithm.name, key, messageAsUint8Array)
+        return Base64URL.stringify(new Uint8Array(res)) === signaturePart
+    }
+    decode(token) {
+        let output = token.split('.')[1].replace(/-/g, '+').replace(/_/g, '/')
+        switch (output.length % 4) {
+            case 0:
+                break
+            case 2:
+                output += '=='
+                break
+            case 3:
+                output += '='
+                break
+            default:
+                throw new Error('Illegal base64url string!')
+        }
+        try {
+            return JSON.parse(decodeURIComponent(escape(atob(output))))
+        } catch {
+            return null
+        }
+    }
+}
+
+module.exports = new JWT