refactor: move multipler derivation to the SRP parameters

zolbooo · Jun 2, 2024 · 6436c36 · 6436c36
1 parent b8d35d9
commit 6436c36
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Showing 6 changed files with 10 additions and 28 deletions.
diff --git a/src/client.ts b/src/client.ts
@@ -1,13 +1,8 @@
 import * as constants from "./constants";
 
 import { SRPParameterSet } from "./constants";
-import {
-  byteArrayToHexString,
-  concatByteArrays,
-  safeByteArrayEquals,
-} from "./utils";
+import { concatByteArrays, safeByteArrayEquals } from "./utils";
 
-import { DeriveMultiplierFn } from "./srp/multiplier";
 import { DigestFn, deriveVerifier } from "./srp/verifier";
 import {
   deriveSessionKey,
@@ -21,25 +16,19 @@ export class ClientSession {
   private parameters: SRPParameterSet = constants.SRP_PARAMETERS_RFC5054_2048;
 
   private digest?: DigestFn;
-  private deriveMultiplier?: DeriveMultiplierFn;
   constructor({
     parameters,
     digest,
-    deriveMultiplier,
   }: {
     parameters?: SRPParameterSet;
     digest?: DigestFn;
-    deriveMultiplier?: DeriveMultiplierFn;
   } = {}) {
     if (parameters) {
       this.parameters = parameters;
     }
     if (digest) {
       this.digest = digest;
     }
-    if (deriveMultiplier) {
-      this.deriveMultiplier = deriveMultiplier;
-    }
   }
 
   private clientPrivateEphemeral?: Uint8Array;
@@ -82,7 +71,6 @@ export class ClientSession {
       serverPublicEphemeral: serverPublicEphemeral,
       parameters: this.parameters,
       digest: this.digest,
-      deriveMultiplier: this.deriveMultiplier,
     });
     this.sessionKey = sessionKey;
     const clientProof = await deriveClientProof({

diff --git a/src/constants.ts b/src/constants.ts
@@ -1,10 +1,13 @@
+import { DeriveMultiplierFn } from "./srp/multiplier";
+
 import { hexStringToByteArray } from "./utils";
 
 export type SRPHashAlgorithm = "SHA-1" | "SHA-256" | "SHA-384" | "SHA-512";
 export interface SRPParameterSet {
   N: Uint8Array;
   G: Uint8Array;
   algorithm: SRPHashAlgorithm;
+  deriveMultiplier?: DeriveMultiplierFn;
 }
 
 export const SRP_PARAMETERS_RFC5054_2048: SRPParameterSet = {

diff --git a/src/server.ts b/src/server.ts
@@ -8,25 +8,18 @@ import {
   generateServerEphemeral,
 } from "./srp/server";
 import { deriveClientProof } from "./srp/client";
-import { DeriveMultiplierFn } from "./srp/multiplier";
 
 export class ServerSession {
   private parameters: SRPParameterSet = constants.SRP_PARAMETERS_RFC5054_2048;
 
-  private deriveMultiplier?: DeriveMultiplierFn;
   constructor({
     parameters,
-    deriveMultiplier,
   }: {
     parameters?: SRPParameterSet;
-    deriveMultiplier?: DeriveMultiplierFn;
   } = {}) {
     if (parameters) {
       this.parameters = parameters;
     }
-    if (deriveMultiplier) {
-      this.deriveMultiplier = deriveMultiplier;
-    }
   }
 
   private clientVerifier?: Uint8Array;
@@ -45,7 +38,6 @@ export class ServerSession {
       await generateServerEphemeral({
         verifier,
         parameters: this.parameters,
-        deriveMultiplier: this.deriveMultiplier,
       });
     this.clientVerifier = verifier;
     this.clientPublicEphemeral = clientPublicEphemeral;

diff --git a/src/srp/client.ts b/src/srp/client.ts
@@ -9,8 +9,8 @@ import {
 } from "../utils";
 
 import { deriveSharedHash } from "./common";
+import { deriveMultiplierSRP6a } from "./multiplier";
 import { DigestFn, deriveVerifier, digestPBKDF2 } from "./verifier";
-import { DeriveMultiplierFn, deriveMultiplierSRP6a } from "./multiplier";
 
 export function generateClientEphemeral(
   parameters: SRPParameterSet = defaultParameters
@@ -57,7 +57,6 @@ export async function deriveSessionKey({
   salt,
   clientPrivateEphemeral,
   serverPublicEphemeral,
-  deriveMultiplier = deriveMultiplierSRP6a,
   digest = digestPBKDF2,
   parameters = defaultParameters,
   unsafe_skipOutputHashing = false,
@@ -68,7 +67,6 @@ export async function deriveSessionKey({
   salt: Uint8Array;
   clientPrivateEphemeral: Uint8Array;
   serverPublicEphemeral: Uint8Array;
-  deriveMultiplier?: DeriveMultiplierFn;
   digest?: DigestFn;
   parameters?: SRPParameterSet;
   unsafe_skipOutputHashing?: boolean;
@@ -82,7 +80,9 @@ export async function deriveSessionKey({
           parameters,
         })
   );
+  const { deriveMultiplier = deriveMultiplierSRP6a } = parameters;
   const k = byteArrayToBigInt(await deriveMultiplier(parameters));
+
   const N = byteArrayToBigInt(parameters.N);
   const { x: xBytes, verifier } = await deriveVerifier(
     { username, password },

diff --git a/src/srp/multiplier.ts b/src/srp/multiplier.ts
@@ -2,7 +2,7 @@ import { SRPParameterSet } from "../constants";
 import { concatByteArrays, padData } from "../utils";
 
 export type DeriveMultiplierFn = (
-  parameters: SRPParameterSet
+  parameters: Pick<SRPParameterSet, "N" | "G" | "algorithm">
 ) => Uint8Array | Promise<Uint8Array>;
 
 export const deriveMultiplierSRP6a: DeriveMultiplierFn = async (parameters) =>

diff --git a/src/srp/server.ts b/src/srp/server.ts
@@ -9,22 +9,21 @@ import {
 } from "../utils";
 
 import { deriveSharedHash } from "./common";
-import { DeriveMultiplierFn, deriveMultiplierSRP6a } from "./multiplier";
+import { deriveMultiplierSRP6a } from "./multiplier";
 
 export async function generateServerEphemeral({
   verifier,
-  deriveMultiplier = deriveMultiplierSRP6a,
   parameters = defaultParameters,
   unsafe_staticPrivateEphemeral,
 }: {
   verifier: Uint8Array;
-  deriveMultiplier?: DeriveMultiplierFn;
   parameters?: SRPParameterSet;
   unsafe_staticPrivateEphemeral?: Uint8Array;
 }): Promise<{
   serverPrivateEphemeral: Uint8Array;
   serverPublicEphemeral: Uint8Array;
 }> {
+  const { deriveMultiplier = deriveMultiplierSRP6a } = parameters;
   const multiplier = BigInt(
     "0x" + byteArrayToHexString(await deriveMultiplier(parameters))
   );