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fix(crypto): reject invalid hex operands in timingSafeEqualHex #1760

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Merged
JSONbored merged 2 commits into from
Jun 29, 2026
Merged

fix(crypto): reject invalid hex operands in timingSafeEqualHex #1760

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53d3860
fix(crypto): reject invalid hex operands in timingSafeEqualHex
Jun 29, 2026
c28da6c
Merge branch 'main' into fix/crypto-timing-safe-equal-hex
andriypolanski Jun 29, 2026
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5 changes: 3 additions & 2 deletions src/utils/crypto.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,7 @@ export async function verifyGitHubSignature(rawBody: string, signatureHeader: st
export function timingSafeEqualHex(left: string, right: string): boolean {
const leftBytes = hexToBytes(left);
const rightBytes = hexToBytes(right);
if (!leftBytes || !rightBytes) return false;
if (leftBytes.length !== rightBytes.length) return false;
let result = 0;
for (let index = 0; index < leftBytes.length; index += 1) {
Expand All @@ -32,8 +33,8 @@ export function timingSafeEqualHex(left: string, right: string): boolean {
return result === 0;
}

function hexToBytes(hex: string): Uint8Array {
if (!/^[0-9a-f]+$/i.test(hex) || hex.length % 2 !== 0) return new Uint8Array();
function hexToBytes(hex: string): Uint8Array | null {
if (hex.length === 0 || hex.length % 2 !== 0 || !/^[0-9a-f]+$/i.test(hex)) return null;
const bytes = new Uint8Array(hex.length / 2);
for (let index = 0; index < bytes.length; index += 1) {
bytes[index] = Number.parseInt(hex.slice(index * 2, index * 2 + 2), 16);
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12 changes: 11 additions & 1 deletion test/unit/crypto.test.ts
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
import { describe, expect, it } from "vitest";
import { createOpaqueToken, hashToken, timingSafeEqual } from "../../src/auth/security";
import { verifyGitHubSignature } from "../../src/utils/crypto";
import { verifyGitHubSignature, timingSafeEqualHex } from "../../src/utils/crypto";

describe("webhook signature verification", () => {
it("accepts valid GitHub HMAC signatures and rejects tampering", async () => {
Expand All @@ -17,6 +17,16 @@ describe("webhook signature verification", () => {
await expect(verifyGitHubSignature(body, null, secret)).resolves.toBe(false);
await expect(verifyGitHubSignature(body, "bad-prefix", secret)).resolves.toBe(false);
await expect(verifyGitHubSignature(body, `sha256=${signature}`, "")).resolves.toBe(false);
await expect(verifyGitHubSignature(body, "sha256=not-valid-hex", secret)).resolves.toBe(false);
});

it("rejects invalid hex operands in timingSafeEqualHex", () => {
expect(timingSafeEqualHex("zz", "yy")).toBe(false);
expect(timingSafeEqualHex("not-hex-a", "not-hex-b")).toBe(false);
expect(timingSafeEqualHex("abc", "abcd")).toBe(false);
expect(timingSafeEqualHex("", "00")).toBe(false);
expect(timingSafeEqualHex("00", "01")).toBe(false);
expect(timingSafeEqualHex("00", "00")).toBe(true);
});

it("uses timing-safe token comparisons and one-way token hashes", async () => {
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