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Biometric capability (iOS)

BiometricSecurity.getStatus() · check id biometrics

No biometric data is read, stored, transmitted or exposed by this check, and none is available to it. LAContext reports availability and a biometry type; nothing here can identify a user. A test asserts that signal metadata carries nothing beyond those.

See biometrics.md for the Android signals under the same check id.

1. What it detects

  • whether biometric authentication can be evaluated right now, and if not, why;
  • which biometry type the device supports;
  • whether a device passcode is set.

2. An unenrolled device is not an insecure device

Many people deliberately use a passcode and no biometric, and that is a perfectly good choice. These signals exist so an application can decide whether biometric authentication is a viable gate — not so it can nag someone into enrolling a face they do not want to enrol.

The one unambiguous weakness here is BIOMETRIC-003: without a passcode there is no lock screen, biometric enrolment is impossible, and kSecAttrAccessibleWhenPasscodeSetThisDeviceOnly cannot be used.

3. Signals

ID Indicator Confidence
RNSEC-IOS-BIOMETRIC-001 Biometric authentication not currently usable high
RNSEC-IOS-BIOMETRIC-002 Device reports no biometry type medium
RNSEC-IOS-BIOMETRIC-003 No device passcode set high

The reason matters as much as the verdict

BIOMETRIC-001 reports why biometrics are unusable, because each cause calls for a different response:

Reason What an application should do
not-available No hardware. Permanent — design around it.
not-enrolled The user can fix this in seconds. Offer, do not demand.
lockout Temporary, after failed attempts. Retry later.
passcode-not-set The floor is missing; see BIOMETRIC-003.

biometryType is only populated by LAContext after canEvaluatePolicy has been called, so one evaluated context is reused for every question.

4. Confidence

Result Meaning
secure + high Biometrics usable, a type present, passcode set.
detected + high Biometrics unusable, or no passcode at all.
detected + medium No biometry hardware.
unknown + low The platform did not answer.

5. False positives

  • Nothing enrolled is a user preference far more often than a security problem.
  • lockout is transient; re-checking later may give a different answer.
  • Managed and supervised devices can report differently from a personal one.

6. Known limitations

Capability only. Whether your application actually uses biometric authentication, binds it to a keychain item, or handles evaluatedPolicyDomainState changes when enrolment changes, is invisible here.

7. Recommended application response

const biometrics = await BiometricSecurity.getStatus();

const noPasscode = biometrics.signals.some(
  (signal) => signal.id === 'RNSEC-IOS-BIOMETRIC-003' && signal.detected
);

if (noPasscode) {
  // The only signal here worth acting on firmly.
}

Do not gate access on biometric enrolment. Offer biometrics where available, fall back to a device passcode, and put the real gate on your server.

8. Tests

ios/EngineTests/CapabilityDetectorsTests.swift — 7 cases including one per unavailability reason, and an assertion that no signal's metadata carries anything beyond a reason, a type and a boolean.