feat(sdk-hmac): add v4 canonical preimage construction

TICKET: CAAS-660

Author: MohammedRyaan786

modules/sdk-hmac/src/hmac.ts

@@ -1,4 +1,4 @@
-import { type BinaryLike, createHmac, type KeyObject } from 'crypto';
+import { type BinaryLike, type KeyObject } from 'crypto';
 import * as urlLib from 'url';
 import * as sjcl from '@bitgo/sjcl';
 import {
@@ -9,6 +9,7 @@ import {
   VerifyResponseInfo,
   VerifyResponseOptions,
 } from './types';
+import { hmacSha256 } from './util';
 
 /**
  * Calculate the HMAC for the given key and message
@@ -17,7 +18,7 @@ import {
  * @returns {*} - the result of the HMAC operation
  */
 export function calculateHMAC(key: string | BinaryLike | KeyObject, message: string | BinaryLike): string {
-  return createHmac('sha256', key).update(message).digest('hex');
+  return hmacSha256(key, message);
 }
 
 /**

modules/sdk-hmac/src/hmacv4.ts

@@ -0,0 +1,315 @@
+/**
+ * @prettier
+ *
+ * V4 HMAC Authentication Module
+ *
+ * This module implements the v4 authentication scheme which uses a canonical
+ * preimage construction with newline-separated fields and body hashing.
+ *
+ * Key differences from v2/v3:
+ * - Separator: newline (\n) instead of pipe (|)
+ * - Body: SHA256 hash of raw bytes instead of actual body content
+ * - Timestamp: seconds instead of milliseconds
+ * - New field: authRequestId for request tracking
+ * - Trailing newline in preimage
+ * - Support for x-original-* headers (proxy scenarios)
+ */
+
+import { timingSafeEqual } from 'crypto';
+import { hmacSha256, sha256Hex, normalizeMethod, getTimestampSec } from './util';
+import {
+  CalculateV4PreimageOptions,
+  CalculateV4RequestHmacOptions,
+  CalculateV4RequestHeadersOptions,
+  V4RequestHeaders,
+  VerifyV4ResponseOptions,
+  VerifyV4ResponseInfo,
+} from './types';
+
+/**
+ * Build canonical preimage for v4 authentication.
+ *
+ * The preimage is constructed as newline-separated values with a trailing newline:
+ * ```
+ * {timestampSec}
+ * {METHOD}
+ * {pathWithQuery}
+ * {bodyHashHex}
+ * {authRequestId}
+ * ```
+ *
+ * This function normalizes the HTTP method to uppercase and handles the
+ * legacy 'del' method conversion to 'DELETE'.
+ *
+ * @param options - The preimage components
+ * @returns Newline-separated canonical preimage string with trailing newline
+ *
+ * @example
+ * ```typescript
+ * const preimage = calculateV4Preimage({
+ *   timestampSec: 1761100000,
+ *   method: 'post',
+ *   pathWithQuery: '/v2/wallets/transfer?foo=bar',
+ *   bodyHashHex: '0d5e3b7a8f9c1d2e3f4a5b6c7d8e9f0a1b2c3d4e5f6a7b8c9d0e1f2a3b4c5d6e',
+ *   authRequestId: '1b7a1d2b-7a2f-4e4b-a1f8-c2a5a0f84e3e',
+ * });
+ *
+ * // Result:
+ * // "1761100000\nPOST\n/v2/wallets/transfer?foo=bar\n0d5e3b...d6e\n1b7a1d2b-7a2f-4e4b-a1f8-c2a5a0f84e3e\n"
+ * ```
+ */
+export function calculateV4Preimage({
+  timestampSec,
+  method,
+  pathWithQuery,
+  bodyHashHex,
+  authRequestId,
+}: CalculateV4PreimageOptions): string {
+  const normalizedMethod = normalizeMethod(method);
+
+  // Build newline-separated preimage with trailing newline
+  const components = [timestampSec.toString(), normalizedMethod, pathWithQuery, bodyHashHex, authRequestId];
+
+  return components.join('\n') + '\n';
+}
+
+/**
+ * Calculate SHA256 hash of body and return as lowercase hex string.
+ *
+ * This is used to compute the bodyHashHex field for v4 authentication.
+ * The hash is computed over the raw bytes of the request body, ensuring
+ * that the exact bytes sent over the wire are used for signature calculation.
+ *
+ * @param body - Raw request body (Buffer or string)
+ * @returns Lowercase hex SHA256 hash (64 characters)
+ *
+ * @example
+ * ```typescript
+ * const hash = calculateBodyHash(Buffer.from('{"address":"tb1q...","amount":100000}'));
+ * // Returns: '0d5e3b7a8f...' (64 character hex string)
+ * ```
+ */
+export function calculateBodyHash(body: Buffer | string): string {
+  return sha256Hex(body);
+}
+
+/**
+ * Calculate the HMAC-SHA256 signature for a v4 HTTP request.
+ *
+ * This function:
+ * 1. Builds the canonical preimage from the provided options
+ * 2. Computes HMAC-SHA256 of the preimage using the raw access token
+ *
+ * @param options - Request parameters and raw access token
+ * @returns Lowercase hex HMAC-SHA256 signature
+ *
+ * @example
+ * ```typescript
+ * const hmac = calculateV4RequestHmac({
+ *   timestampSec: 1761100000,
+ *   method: 'POST',
+ *   pathWithQuery: '/v2/wallets/transfer',
+ *   bodyHashHex: '0d5e3b...',
+ *   authRequestId: '1b7a1d2b-7a2f-4e4b-a1f8-c2a5a0f84e3e',
+ *   rawToken: 'your-raw-token',
+ * });
+ * ```
+ */
+export function calculateV4RequestHmac({
+  timestampSec,
+  method,
+  pathWithQuery,
+  bodyHashHex,
+  authRequestId,
+  rawToken,
+}: CalculateV4RequestHmacOptions): string {
+  const preimage = calculateV4Preimage({
+    timestampSec,
+    method,
+    pathWithQuery,
+    bodyHashHex,
+    authRequestId,
+  });
+
+  return hmacSha256(rawToken, preimage);
+}
+
+/**
+ * Generate all headers required for v4 authenticated requests.
+ *
+ * This is a convenience function that:
+ * 1. Generates the current timestamp (in seconds)
+ * 2. Calculates the body hash from raw bytes
+ * 3. Computes the HMAC signature
+ * 4. Returns all values needed for request headers
+ *
+ * @param options - Request parameters including raw body and signing key
+ * @returns Object containing all v4 authentication header values
+ *
+ * @example
+ * ```typescript
+ * const headers = calculateV4RequestHeaders({
+ *   method: 'POST',
+ *   pathWithQuery: '/v2/wallets/transfer?foo=bar',
+ *   rawBody: Buffer.from('{"address":"tb1q..."}'),
+ *   signingKey: 'your-signing-key',
+ *   authRequestId: '1b7a1d2b-7a2f-4e4b-a1f8-c2a5a0f84e3e',
+ * });
+ *
+ * // Use headers to set:
+ * // - Auth-Timestamp: headers.timestampSec
+ * // - HMAC: headers.hmac
+ * // - X-Body-Hash: headers.bodyHashHex
+ * // - X-Request-Id: headers.authRequestId
+ * ```
+ */
+export function calculateV4RequestHeaders({
+  method,
+  pathWithQuery,
+  rawBody,
+  rawToken,
+  authRequestId,
+}: CalculateV4RequestHeadersOptions): V4RequestHeaders {
+  const timestampSec = getTimestampSec();
+  const bodyHashHex = calculateBodyHash(rawBody);
+
+  const hmac = calculateV4RequestHmac({
+    timestampSec,
+    method,
+    pathWithQuery,
+    bodyHashHex,
+    authRequestId,
+    rawToken,
+  });
+
+  return {
+    hmac,
+    timestampSec,
+    bodyHashHex,
+    authRequestId,
+  };
+}
+
+/**
+ * Build canonical preimage for v4 response verification.
+ *
+ * Response preimage includes the status code and uses the same format:
+ * ```
+ * {timestampSec}
+ * {METHOD}
+ * {pathWithQuery}
+ * {statusCode}
+ * {bodyHashHex}
+ * {authRequestId}
+ * ```
+ *
+ * @param options - Response verification parameters
+ * @returns Newline-separated canonical preimage string with trailing newline
+ */
+export function calculateV4ResponsePreimage({
+  timestampSec,
+  method,
+  pathWithQuery,
+  statusCode,
+  bodyHashHex,
+  authRequestId,
+}: Omit<VerifyV4ResponseOptions, 'hmac' | 'rawToken'>): string {
+  const normalizedMethod = normalizeMethod(method);
+
+  const components = [
+    timestampSec.toString(),
+    normalizedMethod,
+    pathWithQuery,
+    statusCode.toString(),
+    bodyHashHex,
+    authRequestId,
+  ];
+
+  return components.join('\n') + '\n';
+}
+
+/**
+ * Verify the HMAC signature of a v4 HTTP response.
+ *
+ * This function:
+ * 1. Reconstructs the canonical preimage from response data
+ * 2. Calculates the expected HMAC
+ * 3. Compares with the received HMAC
+ * 4. Checks if the timestamp is within the validity window
+ *
+ * The validity window is:
+ * - 5 minutes backwards (to account for clock skew and network latency)
+ * - 1 minute forwards (to account for minor clock differences)
+ *
+ * @param options - Response data and signing key for verification
+ * @returns Verification result including validity and diagnostic info
+ */
+export function verifyV4Response({
+  hmac,
+  timestampSec,
+  method,
+  pathWithQuery,
+  bodyHashHex,
+  authRequestId,
+  statusCode,
+  rawToken,
+}: VerifyV4ResponseOptions): VerifyV4ResponseInfo {
+  // Build the response preimage
+  const preimage = calculateV4ResponsePreimage({
+    timestampSec,
+    method,
+    pathWithQuery,
+    statusCode,
+    bodyHashHex,
+    authRequestId,
+  });
+
+  // Calculate expected HMAC
+  const expectedHmac = hmacSha256(rawToken, preimage);
+
+  // Use constant-time comparison to prevent timing side-channel attacks
+  const hmacBuffer = Buffer.from(hmac, 'hex');
+  const expectedHmacBuffer = Buffer.from(expectedHmac, 'hex');
+  const isHmacValid =
+    hmacBuffer.length === expectedHmacBuffer.length && timingSafeEqual(hmacBuffer, expectedHmacBuffer);
+
+  // Check timestamp validity window
+  const nowSec = getTimestampSec();
+  const backwardValidityWindowSec = 5 * 60; // 5 minutes
+  const forwardValidityWindowSec = 1 * 60; // 1 minute
+  const isInResponseValidityWindow =
+    timestampSec >= nowSec - backwardValidityWindowSec && timestampSec <= nowSec + forwardValidityWindowSec;
+
+  return {
+    isValid: isHmacValid,
+    expectedHmac,
+    preimage,
+    isInResponseValidityWindow,
+    verificationTime: Date.now(),
+  };
+}
+
+/**
+ * Extract path with query from x-original-uri header or request URL.
+ *
+ * @param xOriginalUri - Value of x-original-uri header (if present)
+ * @param requestUrl - The actual request URL
+ * @returns The path with query to use for preimage calculation
+ *
+ */
+export function getPathWithQuery(xOriginalUri: string | undefined, requestUrl: string): string {
+  // Prefer x-original-uri if available (proxy scenario)
+  return xOriginalUri ?? requestUrl;
+}
+
+/**
+ * Get method from x-original-method header or actual request method.
+ *
+ * @param xOriginalMethod - Value of x-original-method header (if present)
+ * @param requestMethod - The actual request method
+ * @returns The method to use for preimage calculation
+ */
+export function getMethod(xOriginalMethod: string | undefined, requestMethod: string): string {
+  // Prefer x-original-method if available (proxy scenario)
+  return xOriginalMethod ?? requestMethod;
+}

modules/sdk-hmac/src/index.ts

@@ -1,2 +1,4 @@
 export * from './hmac';
+export * from './hmacv4';
+export * from './util';
 export * from './types';