feat: do not send non-JWTs in Authorization header

src/SupabaseClient.ts

@@ -19,7 +19,12 @@ import {
   DEFAULT_REALTIME_OPTIONS,
 } from './lib/constants'
 import { fetchWithAuth } from './lib/fetch'
-import { stripTrailingSlash, applySettingDefaults } from './lib/helpers'
+import {
+  stripTrailingSlash,
+  applySettingDefaults,
+  isJWT,
+  checkAuthorizationHeader,
+} from './lib/helpers'
 import { SupabaseAuthClient } from './lib/SupabaseAuthClient'
 import { Fetch, GenericSchema, SupabaseClientOptions, SupabaseAuthClientOptions } from './lib/types'
 
@@ -96,6 +101,8 @@ export default class SupabaseClient<
     this.storageKey = settings.auth.storageKey ?? ''
     this.headers = settings.global.headers ?? {}
 
+    checkAuthorizationHeader(this.headers)
+
     if (!settings.accessToken) {
       this.auth = this._initSupabaseAuthClient(
         settings.auth ?? {},
@@ -285,10 +292,14 @@ export default class SupabaseClient<
     headers?: Record<string, string>,
     fetch?: Fetch
   ) {
-    const authHeaders = {
-      Authorization: `Bearer ${this.supabaseKey}`,
+    const authHeaders: { [header: string]: string } = {
       apikey: `${this.supabaseKey}`,
     }
+
+    if (isJWT(this.supabaseKey)) {
+      authHeaders.Authorization = `Bearer ${this.supabaseKey}`
+    }
+
     return new SupabaseAuthClient({
       url: this.authUrl,
       headers: { ...authHeaders, ...headers },

src/lib/fetch.ts

@@ -1,5 +1,6 @@
 // @ts-ignore
 import nodeFetch, { Headers as NodeFetchHeaders } from '@supabase/node-fetch'
+import { isJWT } from './helpers'
 
 type Fetch = typeof fetch
 
@@ -31,15 +32,17 @@ export const fetchWithAuth = (
   const fetch = resolveFetch(customFetch)
   const HeadersConstructor = resolveHeadersConstructor()
 
+  const defaultAccessToken = isJWT(supabaseKey) ? supabaseKey : null
+
   return async (input, init) => {
-    const accessToken = (await getAccessToken()) ?? supabaseKey
+    const accessToken = (await getAccessToken()) ?? defaultAccessToken
     let headers = new HeadersConstructor(init?.headers)
 
     if (!headers.has('apikey')) {
       headers.set('apikey', supabaseKey)
     }
 
-    if (!headers.has('Authorization')) {
+    if (!headers.has('Authorization') && accessToken) {
       headers.set('Authorization', `Bearer ${accessToken}`)
     }
 

src/lib/helpers.ts

@@ -66,3 +66,58 @@ export function applySettingDefaults<
 
   return result
 }
+
+export const BASE64URL_REGEX = /^([a-z0-9_-]{4})*($|[a-z0-9_-]{3}$|[a-z0-9_-]{2}$)$/i
+
+/**
+ * Checks that the value somewhat looks like a JWT, does not do any additional parsing or verification.
+ */
+export function isJWT(value: string): boolean {
+  if (value.startsWith('Bearer ')) {
+    value = value.substring('Bearer '.length)
+  }
+
+  value = value.trim()
+
+  if (!value) {
+    return false
+  }
+
+  const parts = value.split('.')
+
+  if (parts.length !== 3) {
+    return false
+  }
+
+  for (let i = 0; i < parts.length; i += 1) {
+    const part = parts[i]
+
+    if (part.length < 4 || !parts[i].match(BASE64URL_REGEX)) {
+      return false
+    }
+  }
+
+  return true
+}
+
+export function checkAuthorizationHeader(headers: { [header: string]: string }) {
+  if (headers.authorization && headers.Authorization) {
+    console.warn(
+      '@supabase-js: Both `authorization` and `Authorization` headers specified in createClient options. `Authorization` will be used.'
+    )
+  }
+
+  const authorization = headers.Authorization ?? headers.authorization ?? null
+
+  if (!authorization) {
+    return
+  }
+
+  if (authorization.startsWith('Bearer ') && authorization.length > 'Bearer '.length) {
+    if (!isJWT(authorization)) {
+      throw new Error(
+        '@supabase-js: createClient called with global Authorization header that does not contain a JWT'
+      )
+    }
+  }
+}