fix: allow shorter HMAC secrets

With workarounds available its enforcement is just adding extra code that annoys developers.
panva · Nov 1, 2021 · 57126f1 · 57126f1
1 parent 4f99309
commit 57126f1
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Showing 3 changed files with 0 additions and 34 deletions.
diff --git a/src/runtime/browser/check_key_length.ts b/src/runtime/browser/check_key_length.ts
@@ -1,12 +1,4 @@
 export default (alg: string, key: CryptoKey) => {
-  if (alg.startsWith('HS')) {
-    const bitlen = parseInt(alg.substr(-3), 10)
-    const { length } = <HmacKeyAlgorithm>key.algorithm
-    if (typeof length !== 'number' || length < bitlen) {
-      throw new TypeError(`${alg} requires symmetric keys to be ${bitlen} bits or larger`)
-    }
-  }
-
   if (alg.startsWith('RS') || alg.startsWith('PS')) {
     const { modulusLength } = <RsaKeyAlgorithm>key.algorithm
     if (typeof modulusLength !== 'number' || modulusLength < 2048) {

diff --git a/src/runtime/node/sign.ts b/src/runtime/node/sign.ts
@@ -22,10 +22,6 @@ const sign: SignFunction = async (alg, key: unknown, data) => {
   const keyObject = getSignKey(alg, key, 'sign')
 
   if (alg.startsWith('HS')) {
-    const bitlen = parseInt(alg.substr(-3), 10)
-    if (!keyObject.symmetricKeySize || keyObject.symmetricKeySize << 3 < bitlen) {
-      throw new TypeError(`${alg} requires symmetric keys to be ${bitlen} bits or larger`)
-    }
     const hmac = crypto.createHmac(hmacDigest(alg), keyObject)
     hmac.update(data)
     return hmac.digest()

diff --git a/test/jws/restrictions.test.mjs b/test/jws/restrictions.test.mjs
@@ -63,28 +63,6 @@ Promise.all([
       }
     })
 
-    async function testHMAC(t, alg) {
-      const size = parseInt(alg.substr(-3), 10)
-      const message = `${alg} requires symmetric keys to be ${size} bits or larger`
-      const secret = crypto.randomFillSync(new Uint8Array((size >> 3) - 1))
-      await t.throwsAsync(
-        new FlattenedSign(t.context.payload).setProtectedHeader({ alg }).sign(secret),
-        { instanceOf: TypeError, message },
-      )
-
-      const jws = await new FlattenedSign(t.context.payload)
-        .setProtectedHeader({ alg })
-        .sign(crypto.randomFillSync(new Uint8Array(size >> 3)))
-
-      await t.throwsAsync(flattenedVerify(jws, secret), { instanceOf: TypeError, message })
-    }
-    testHMAC.title = (title, alg) =>
-      `${alg} requires symmetric keys to be ${alg.substr(-3)} bits or larger`
-
-    test(testHMAC, 'HS256')
-    test(testHMAC, 'HS384')
-    test(testHMAC, 'HS512')
-
     async function testRSAsig(t, alg) {
       const message = `${alg} requires key modulusLength to be 2048 bits or larger`
       const keyBad = t.context.rsa2040