otplib API Documentation / @otplib/core / validateCounterTolerance

Function: validateCounterTolerance()

validateCounterTolerance(counterTolerance, guardrails): void

Defined in: packages/core/src/utils.ts:356

Validate counter tolerance for HOTP verification

Prevents DoS attacks by limiting the number of counter values checked.

Parameters

counterTolerance

Counter tolerance specification (number or array of offsets)

number | number[]

guardrails

OTPGuardrails = DEFAULT_GUARDRAILS

Validation guardrails (defaults to RFC recommendations)

Returns

void

Throws

If tolerance size exceeds MAX_WINDOW

Example

validateCounterTolerance(1);        // OK: 3 offsets [-1, 0, 1]
validateCounterTolerance(100);      // OK: 201 offsets [-100, ..., 100]
validateCounterTolerance(101);      // Throws: exceeds MAX_WINDOW
validateCounterTolerance([0, 1]);   // OK: 2 offsets