feat: pin_derived_eph_pub+priv (#128)

Signed-off-by: Berend Sliedrecht <[email protected]>

.gitignore

@@ -100,6 +100,6 @@ android
 
 # build output
 dist/
-types/
+packages/ui/types
 
-storybook-static
+storybook-static

apps/funke/constants.ts

@@ -0,0 +1 @@
+export const FUNKE_WALLET_INSTANCE_LONG_TERM_AES_KEY_ID = 'FUNKE_WALLET_INSTANCE_LONG_TERM_AES_KEY_ID'

apps/funke/crypto/aes.ts

@@ -0,0 +1,4 @@
+import { aes128Gcm } from '@package/agent'
+import { FUNKE_WALLET_INSTANCE_LONG_TERM_AES_KEY_ID } from '../constants'
+
+export const funkeAes128Gcm = aes128Gcm(FUNKE_WALLET_INSTANCE_LONG_TERM_AES_KEY_ID)

apps/funke/crypto/bPrime.ts

@@ -0,0 +1,35 @@
+import { type AgentContext, TypedArrayEncoder } from '@credo-ts/core'
+import { Key, KeyAlgs, KeyMethod } from '@hyperledger/aries-askar-react-native'
+import { kdf } from '@package/secure-store/kdf'
+import { funkeAes128Gcm } from './aes'
+
+/**
+ *
+ * Derive a key pair based on a numeric pin according to the steps in B'
+ *
+ * returns pin_derived_eph_pub + pin_derived_eph_priv
+ *
+ * @todo Might be good later to add methods like `signWithPidPin`
+ *
+ */
+export const deriveKeypairFromPin = async (agentContext: AgentContext, pin: Array<number>) => {
+  if (!(await funkeAes128Gcm.aes128GcmHasKey({ agentContext }))) {
+    throw new Error('No AES key found in storage. Flow is called in an incorrect way!')
+  }
+
+  const pinSecret = await funkeAes128Gcm.aes128GcmEncrypt({
+    agentContext,
+    data: new Uint8Array(pin),
+  })
+
+  const pinSeed = await kdf.derive(
+    TypedArrayEncoder.toUtf8String(new Uint8Array(pin)),
+    TypedArrayEncoder.toUtf8String(pinSecret)
+  )
+
+  return Key.fromSeed({
+    seed: new Uint8Array(TypedArrayEncoder.fromHex(pinSeed)),
+    method: KeyMethod.None,
+    algorithm: KeyAlgs.EcSecp256r1,
+  })
+}

apps/funke/package.json

@@ -19,6 +19,7 @@
 		"@package/agent": "workspace:*",
 		"@package/app": "workspace:*",
 		"@package/ui": "workspace:*",
+		"@package/secure-store": "workspace:*",
 		"@react-native-community/blur": "^4.3.2",
 		"@react-native-community/netinfo": "11.3.1",
 		"@react-native-masked-view/masked-view": "0.3.1",
@@ -54,6 +55,7 @@
 	},
 	"devDependencies": {
 		"@babel/core": "^7.24.4",
+		"@credo-ts/core": "0.5.1-alpha.51",
 		"@tamagui/babel-plugin": "^1.104.2",
 		"typescript": "*"
 	}

packages/agent/src/crypto/aes.ts

@@ -0,0 +1,63 @@
+import { assertAskarWallet } from '@credo-ts/askar/build/utils/assertAskarWallet'
+import type { AgentContext } from '@credo-ts/core'
+import { Key, KeyAlgs } from '@hyperledger/aries-askar-react-native'
+
+const aes128GcmGenerateAndStoreKey =
+  (id: string) =>
+  async ({ agentContext }: { agentContext: AgentContext }) => {
+    const wallet = agentContext.wallet
+    const key = Key.generate(KeyAlgs.AesA128Gcm)
+    assertAskarWallet(wallet)
+    await wallet.withSession((session) => session.insertKey({ name: id, key }))
+  }
+
+const aes128GcmHasKey =
+  (id: string) =>
+  async ({ agentContext }: { agentContext: AgentContext }) => {
+    const wallet = agentContext.wallet
+    assertAskarWallet(wallet)
+    const aesKey = await wallet.withSession((session) => session.fetchKey({ name: id }))
+
+    return Boolean(aesKey)
+  }
+
+const aes128GcmGetKey =
+  (id: string) =>
+  async ({ agentContext }: { agentContext: AgentContext }) => {
+    const wallet = agentContext.wallet
+    assertAskarWallet(wallet)
+    const aesKey = await wallet.withSession((session) => session.fetchKey({ name: id }))
+
+    if (!aesKey) {
+      throw new Error(`AES-128-GCM key not found with id: ${id}`)
+    }
+
+    return aesKey.key
+  }
+
+const aes128GcmEncrypt =
+  (id: string) =>
+  async ({
+    data,
+    agentContext,
+    nonce = new Uint8Array(12).fill(1),
+  }: {
+    data: Uint8Array
+    agentContext: AgentContext
+    nonce?: Uint8Array
+  }) => {
+    const wallet = agentContext.wallet
+    assertAskarWallet(wallet)
+
+    const key = await aes128GcmGetKey(id)({ agentContext })
+
+    const { ciphertextWithTag } = key.aeadEncrypt({ nonce, message: data })
+
+    return ciphertextWithTag
+  }
+
+export const aes128Gcm = (id: string) => ({
+  aes128GcmGenerateAndStoreKey: aes128GcmGenerateAndStoreKey(id),
+  aes128GcmHasKey: aes128GcmHasKey(id),
+  aes128GcmEncrypt: aes128GcmEncrypt(id),
+})

packages/agent/src/crypto/index.ts

@@ -0,0 +1 @@
+export * from './aes'

packages/agent/src/index.ts

@@ -22,3 +22,4 @@ export {
   formatDifPexCredentialsForRequest,
 } from './format/formatPresentation'
 export * from './mediation'
+export * from './crypto'

packages/secure-store/secure-unlock/walletKeyDerivation.ts → packages/secure-store/kdf.ts

@@ -1,12 +1,15 @@
 import argon2 from 'react-native-argon2'
 
 /**
- * Derive key from pin and salt.
+ * Derive a hash from pin and salt. (which can be used to seed a key)
  *
  * Configuration based on recommended parameters defined in RFC 9106
  * @see https://www.rfc-editor.org/rfc/rfc9106.html#name-parameter-choice
+ *
+ * returns a hex-encoded derived hash
+ *
  */
-export const deriveWalletKey = async (pin: string, salt: string) => {
+const derive = async (pin: string, salt: string): Promise<string> => {
   const { rawHash } = await argon2(pin, salt, {
     hashLength: 32,
     mode: 'argon2id',
@@ -24,6 +27,12 @@ export const deriveWalletKey = async (pin: string, salt: string) => {
  * @see https://github.com/LinusU/react-native-get-random-values
  * @see https://developer.mozilla.org/en-US/docs/Web/API/Crypto/getRandomValues
  */
-export function generateSalt(): string {
-  return crypto.getRandomValues(new Uint8Array(32)).join('')
-}
+const generateSalt = () => crypto.getRandomValues(new Uint8Array(32)).join('')
+
+/**
+ * Derive key from pin and salt.
+ *
+ * Configuration based on recommended parameters defined in RFC 9106
+ * @see https://www.rfc-editor.org/rfc/rfc9106.html#name-parameter-choice
+ */
+export const kdf = { derive, generateSalt }

packages/secure-store/secureUnlock.ts

@@ -1,6 +1,6 @@
 import { WalletUnlockError } from './error/WalletUnlockError'
+import { kdf } from './kdf'
 import { getSalt, storeSalt } from './secure-unlock/saltStore'
-import { deriveWalletKey, generateSalt } from './secure-unlock/walletKeyDerivation'
 import {
   canUseBiometryBackedWalletKey,
   getWalletKeyUsingBiometrics,
@@ -25,7 +25,7 @@ export async function createSaltForPin(returnExisting = false) {
     if (existingSalt) return existingSalt
   }
 
-  const salt = generateSalt()
+  const salt = kdf.generateSalt()
   await storeSalt(salt, version)
 
   return salt
@@ -37,7 +37,7 @@ export async function getWalletKeyUsingPin(pin: string) {
     throw new WalletUnlockError('Error unlocking wallet. No salt configured')
   }
 
-  const walletKey = await deriveWalletKey(pin, salt)
+  const walletKey = await kdf.derive(pin, salt)
   return walletKey
 }
 

packages/ui/tsconfig.json

@@ -3,7 +3,8 @@
 	"include": ["src"],
 	"compilerOptions": {
 		"composite": true,
-		"jsx": "react-jsx"
+		"jsx": "react-jsx",
+		"typeRoots": ["types"]
 	},
 	"references": []
 }