next-auth vulnerable to possible user mocking that bypasses basic authentication

@@ -21,11 +21,17 @@ export async function signCookie(
 
   logger.debug(`CREATE_${type.toUpperCase()}`, { value, maxAge })
 
+  const { name } = cookies[type]
   const expires = new Date()
   expires.setTime(expires.getTime() + maxAge * 1000)
   return {
-    name: cookies[type].name,
-    value: await jwt.encode({ ...options.jwt, maxAge, token: { value } }),
+    name,
+    value: await jwt.encode({
+      ...options.jwt,
+      maxAge,
+      token: { value },
+      salt: name,
+    }),
     options: { ...cookies[type].options, expires },
   }
 }
@@ -71,16 +77,18 @@ export const pkce = {
     if (!codeVerifier)
       throw new TypeError("PKCE code_verifier cookie was missing.")
 
+    const { name } = options.cookies.pkceCodeVerifier
     const value = (await jwt.decode({
       ...options.jwt,
       token: codeVerifier,
+      salt: name,
     })) as any
 
     if (!value?.value)
       throw new TypeError("PKCE code_verifier value could not be parsed.")
 
     resCookies.push({
-      name: options.cookies.pkceCodeVerifier.name,
+      name,
       value: "",
       options: { ...options.cookies.pkceCodeVerifier.options, maxAge: 0 },
     })
@@ -121,12 +129,17 @@ export const state = {
 
     if (!state) throw new TypeError("State cookie was missing.")
 
-    const value = (await jwt.decode({ ...options.jwt, token: state })) as any
+    const { name } = options.cookies.state
+    const value = (await jwt.decode({
+      ...options.jwt,
+      token: state,
+      salt: name,
+    })) as any
 
     if (!value?.value) throw new TypeError("State value could not be parsed.")
 
     resCookies.push({
-      name: options.cookies.state.name,
+      name,
       value: "",
       options: { ...options.cookies.state.options, maxAge: 0 },
     })
@@ -166,12 +179,17 @@ export const nonce = {
     const nonce = cookies?.[options.cookies.nonce.name]
     if (!nonce) throw new TypeError("Nonce cookie was missing.")
 
-    const value = (await jwt.decode({ ...options.jwt, token: nonce })) as any
+    const { name } = options.cookies.nonce
+    const value = (await jwt.decode({
+      ...options.jwt,
+      token: nonce,
+      salt: name,
+    })) as any
 
     if (!value?.value) throw new TypeError("Nonce value could not be parsed.")
 
     resCookies.push({
-      name: options.cookies.nonce.name,
+      name,
       value: "",
       options: { ...options.cookies.nonce.options, maxAge: 0 },
     })

@@ -15,8 +15,9 @@ const now = () => (Date.now() / 1000) | 0
 
 /** Issues a JWT. By default, the JWT is encrypted using "A256GCM". */
 export async function encode(params: JWTEncodeParams) {
-  const { token = {}, secret, maxAge = DEFAULT_MAX_AGE } = params
-  const encryptionSecret = await getDerivedEncryptionKey(secret)
+  /** @note empty `salt` means a session token. See {@link JWTEncodeParams.salt}. */
+  const { token = {}, secret, maxAge = DEFAULT_MAX_AGE, salt = "" } = params
+  const encryptionSecret = await getDerivedEncryptionKey(secret, salt)
   return await new EncryptJWT(token)
     .setProtectedHeader({ alg: "dir", enc: "A256GCM" })
     .setIssuedAt()
@@ -27,9 +28,10 @@ export async function encode(params: JWTEncodeParams) {
 
 /** Decodes a NextAuth.js issued JWT. */
 export async function decode(params: JWTDecodeParams): Promise<JWT | null> {
-  const { token, secret } = params
+  /** @note empty `salt` means a session token. See {@link JWTDecodeParams.salt}. */
+  const { token, secret, salt = "" } = params
   if (!token) return null
-  const encryptionSecret = await getDerivedEncryptionKey(secret)
+  const encryptionSecret = await getDerivedEncryptionKey(secret, salt)
   const { payload } = await jwtDecrypt(token, encryptionSecret, {
     clockTolerance: 15,
   })
@@ -116,12 +118,15 @@ export async function getToken<R extends boolean = false>(
   }
 }
 
-async function getDerivedEncryptionKey(secret: string | Buffer) {
+async function getDerivedEncryptionKey(
+  keyMaterial: string | Buffer,
+  salt: string
+) {
   return await hkdf(
     "sha256",
-    secret,
-    "",
-    "NextAuth.js Generated Encryption Key",
+    keyMaterial,
+    salt,
+    `NextAuth.js Generated Encryption Key${salt ? ` (${salt})` : ""}`,
     32
   )
 }

@@ -17,7 +17,13 @@ export interface JWT extends Record<string, unknown>, DefaultJWT {}
 export interface JWTEncodeParams {
   /** The JWT payload. */
   token?: JWT
-  /** The secret used to encode the NextAuth.js issued JWT. */
+  /**
+   * Used in combination with `secret` when deriving the encryption secret for the various NextAuth.js-issued JWTs.
+   * @note When no `salt` is passed, we assume this is a session token.
+   * This is for backwards-compatibility with currently active sessions, so they won't be invalidated when upgrading the package.
+   */
+  salt?: string
+  /** The key material used to encode the NextAuth.js issued JWTs. Defaults to `NEXTAUTH_SECRET`. */
   secret: string | Buffer
   /**
    * The maximum age of the NextAuth.js issued JWT in seconds.
@@ -29,7 +35,13 @@ export interface JWTEncodeParams {
 export interface JWTDecodeParams {
   /** The NextAuth.js issued JWT to be decoded */
   token?: string
-  /** The secret used to decode the NextAuth.js issued JWT. */
+  /**
+   * Used in combination with `secret` when deriving the encryption secret for the various NextAuth.js-issued JWTs.
+   * @note When no `salt` is passed, we assume this is a session token.
+   * This is for backwards-compatibility with currently active sessions, so they won't be invalidated when upgrading the package.
+   */
+  salt?: string
+  /** The key material used to decode the NextAuth.js issued JWTs. Defaults to `NEXTAUTH_SECRET`. */
   secret: string | Buffer
 }