fix(security): fallback to crypto.getRandomValues for idempotency keys on insecure origins

src/lib/utils.test.ts

@@ -401,6 +401,63 @@ describe("generateIdempotencyKey", () => {
     const keys = new Set(Array.from({ length: 50 }, () => generateIdempotencyKey()));
     expect(keys.size).toBe(50);
   });
+
+  it("falls back to crypto.getRandomValues when crypto.randomUUID is undefined (#706)", () => {
+    const originalCrypto = globalThis.crypto;
+    const getRandomValuesSpy = jest.fn((bytes: Uint8Array) => {
+      // fill with dummy non-zero bytes to verify version & variant formatting
+      for (let i = 0; i < bytes.length; i++) {
+        bytes[i] = (i * 17 + 5) & 0xff;
+      }
+      return bytes;
+    });
+
+    try {
+      Object.defineProperty(globalThis, "crypto", {
+        value: {
+          getRandomValues: getRandomValuesSpy,
+          randomUUID: undefined,
+        },
+        configurable: true,
+        writable: true,
+      });
+
+      const key = generateIdempotencyKey();
+      expect(getRandomValuesSpy).toHaveBeenCalled();
+      expect(key).toMatch(
+        /^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i,
+      );
+      // Verify version 4 character at position 14
+      expect(key.charAt(14)).toBe("4");
+      // Verify variant [89ab] character at position 19
+      expect(["8", "9", "a", "b"]).toContain(key.charAt(19).toLowerCase());
+    } finally {
+      Object.defineProperty(globalThis, "crypto", {
+        value: originalCrypto,
+        configurable: true,
+        writable: true,
+      });
+    }
+  });
+
+  it("falls back to pseudo-random string when crypto is undefined", () => {
+    const originalCrypto = globalThis.crypto;
+    try {
+      // @ts-expect-error simulating legacy/unsupported environment
+      delete globalThis.crypto;
+
+      const key = generateIdempotencyKey();
+      expect(key).toMatch(
+        /^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i,
+      );
+    } finally {
+      Object.defineProperty(globalThis, "crypto", {
+        value: originalCrypto,
+        configurable: true,
+        writable: true,
+      });
+    }
+  });
 });
 
 // ─── toCents / toMajorUnits ────────────────────────────────────────────────

src/lib/utils.ts

@@ -316,11 +316,21 @@ export function validateTeamSplits(
  * popup timeout.
  */
 export function generateIdempotencyKey(): string {
-  if (typeof crypto !== "undefined" && crypto.randomUUID) {
+  if (typeof crypto !== "undefined" && typeof crypto.randomUUID === "function") {
     return crypto.randomUUID();
   }
-  // Fallback for environments without crypto.randomUUID (very unlikely in
-  // modern browsers, but defensive).
+  // crypto.randomUUID is only exposed in secure contexts (HTTPS/localhost).
+  // In non-secure contexts (e.g. plain-HTTP staging), fall back to
+  // crypto.getRandomValues to construct an RFC 4122 v4 UUID securely (#706).
+  if (typeof crypto !== "undefined" && typeof crypto.getRandomValues === "function") {
+    const bytes = new Uint8Array(16);
+    crypto.getRandomValues(bytes);
+    bytes[6] = (bytes[6] & 0x0f) | 0x40; // RFC 4122 version 4
+    bytes[8] = (bytes[8] & 0x3f) | 0x80; // RFC 4122 variant 1
+    const hex = Array.from(bytes, (b) => b.toString(16).padStart(2, "0")).join("");
+    return `${hex.slice(0, 8)}-${hex.slice(8, 12)}-${hex.slice(12, 16)}-${hex.slice(16, 20)}-${hex.slice(20, 32)}`;
+  }
+  // Fallback for environments without Web Crypto API (defensive).
   return "xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx".replace(/[xy]/g, (c) => {
     const r = (Math.random() * 16) | 0;
     return (c === "x" ? r : (r & 0x3) | 0x8).toString(16);