otplib API Documentation / @otplib/core / utils / validateCounterTolerance

Function: validateCounterTolerance()

validateCounterTolerance(counterTolerance, guardrails?): void

Defined in: packages/core/src/utils.ts:435

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, number]

guardrails?

OTPGuardrails = DEFAULT_GUARDRAILS

Validation guardrails (defaults to RFC recommendations)

Returns

void

Throws

If tolerance size exceeds MAX_WINDOW

Example

validateCounterTolerance(1);        // OK: [0, 1] = 2 checks
validateCounterTolerance(98);       // OK: [0, 98] = 99 checks
validateCounterTolerance(99);       // Throws: exceeds MAX_WINDOW
validateCounterTolerance([0, 1]);   // OK: 2 offsets