🚀 Feature Request — crypto.subtle.importKey should support large RSA public exponent

[thibmeu]

It would be great if crypto.subtle.importKey would support large RSA public key exponent.

The following worker (playground) highlights the curent error path

addEventListener('fetch', event => {
  event.respondWith(handleRequest(event.request))
})

async function handleRequest(request) {
  try {
    await crypto.subtle.importKey('jwk', {
      "alg": "PS384",
      "e": "K932_NQuz0qCWG0SZbKm97-6NG1Oy2VFbwAb9Mh1OcHS0jXlZCCa-jJWd9li6aYd_bLkcR26K70eFxIIxSY8bZElSeidBcpBewjHUd5wNmubxI9MInQPgsPUT9gEHXYeRC1o0vBUOUPH7hDNfCEC9ijSOiTFDT01oZakoc_XoTc",
      "ext": true,
      "key_ops": [
          "verify"
      ],
      "kty": "RSA",
      "n": "1pMIIPcf5Re_MlnRTUAgmwKlwNPWGZHHMd19o5-NaYIVUuIxjWya2JfmA4h6R26jFiwSBdqayW8C7fMd8Em9VfFCE0wX1DgqDnjidTRfFl--jknNymz1xybFmd054J514PMwozEh5zl25PrLqc-gAcKLfJb4E0-ZgdtnULQ6QXEPUdpCQP4DEGwSrLHnu1PXXsclbaP93QcYuJw2VBD85hvHyZsRX7TDwxgIH6fhtlo3d06OUMlujOKyzGs7NnmCNmor-ZJMS6_bP_XnIiWKtwXHbUPl8fEhuYSBTpjqKyuHJc2byQXAvD11wqjbcKcVMhPDmuNxsrXcHa_LGdb66Q"
    }, {name: 'RSA-PSS', hash: 'SHA-384'}, true, ['verify'])
    return new Response('crypto.subtle.importKey succeded')
  } catch (e) {
    return new Response(`crypto.subtle.importKey failed: ${e.message}`, { status: 500 })
  }
}

This key import works in Node.js v20 and Firefox.

While there might be a performance penalty, the extra CPU usage would be reflected on the worker bill.

The relevant code is

workerd/src/workerd/api/crypto-impl-asymmetric.c++

Lines 973 to 992 in 62481a4

	// Now check the public exponent for allow-listed values.
	// First see if we can convert the public exponent to an unsigned number. Unfortunately OpenSSL
	// doesn't have convenient APIs to do this (since these are bignums) so we have to do it by hand.
	// Since the problematic BIGNUMs are within the range of an unsigned int (& technicall an
	// unsigned short) we can treat an out-of-range issue as valid input.
	KJ_IF_SOME(v, fromBignum<unsigned>(publicExponent)) {
	if (!isImport) {
	JSG_REQUIRE(v == 3 || v == 65537, DOMOperationError,
	"The \"publicExponent\" must be either 3 or 65537, but got ", v, ".");
	} else if (strictCrypto) {
	// While we have long required the exponent to be 3 or 65537 when generating keys, handle
	// imported keys more permissively and allow additional exponents that are considered safe
	// and commonly used.
	JSG_REQUIRE(v == 3 || v == 17 || v == 37 || v == 65537, DOMOperationError,
	"Imported RSA key has invalid publicExponent ", v, ".");
	}
	} else {
	JSG_FAIL_REQUIRE(DOMOperationError, "The \"publicExponent\" must be either 3 or 65537, but "
	"got a number larger than 2^32.");
	}

[jasnell]

@irvinebroque @mikenomitch ... this is related to recent discussions around compute limits and crypto operations. We should discuss and figure out how to prioritize.