rsa-compat.js/lib/rasha

Rasha.js ·

Sponsored by Root. Built for ACME.js and Greenlock.js

| ~550 lines of code | 3kb gzipped | 10kb minified | 18kb with comments |

RSA tools. Lightweight. Zero Dependencies. Universal compatibility.

• Fast and Easy RSA Key Generation
• PEM-to-JWK
• JWK-to-PEM
• SSH "pub" format
• ECDSA
  • Need EC or ECDSA tools? Check out Eckles.js

Generate RSA Key

Achieves the fastest possible key generation using node's native RSA bindings to OpenSSL, then converts to JWK for ease-of-use.

Rasha.generate({ format: 'jwk' }).then(function (keypair) {
  console.log(keypair.private);
  console.log(keypair.public);
});

options

• format defaults to 'jwk'
  • 'pkcs1' (traditional)
  • 'pkcs8'
• modulusLength defaults to 2048 (must not be lower)
  • generally you shouldn't pick a larger key size - they're slow
  • 2048 is more than sufficient
  • 3072 is way, way overkill and takes a few seconds to generate
  • 4096 can take about a minute to generate and is just plain wasteful

advanced options

These options are provided for debugging and should not be used.

• publicExponent defaults to 65537 (0x10001)

PEM-to-JWK

• PKCS#1 (traditional)
• PKCS#8, SPKI/PKIX
• 2048-bit, 3072-bit, 4096-bit (and ostensibily all others)
• SSH (RFC4716), (RFC 4716/SSH2)

var Rasha = require('rasha');
var pem = require('fs')
  .readFileSync('./node_modles/rasha/fixtures/privkey-rsa-2048.pkcs1.pem', 'ascii');

Rasha.import({ pem: pem }).then(function (jwk) {
  console.log(jwk);
});

{
  "kty": "RSA",
  "n": "m2ttVBxPlWw06ZmGBWVDl...QlEz7UNNj9RGps_50-CNw",
  "e": "AQAB",
  "d": "Cpfo7Mm9Nu8YMC_xrZ54W...Our1IdDzJ_YfHPt9sHMQQ",
  "p": "ynG-t9HwKCN3MWRYFdnFz...E9S4DsGcAarIuOT2TsTCE",
  "q": "xIkAjgUzB1zaUzJtW2Zgv...38ahSrBFEVnxjpnPh1Q1c",
  "dp": "tzDGjECFOU0ehqtuqhcu...dVGAXJoGOdv5VpaZ7B1QE",
  "dq": "kh5dyDk7YCz7sUFbpsmu...aX9PKa12HFlny6K1daL48",
  "qi": "AlHWbx1gp6Z9pbw_1hlS...lhmIOgRApS0t9VoXtHhFU"
}

JWK-to-PEM

• PKCS#1 (traditional)
• PKCS#8, SPKI/PKIX
• 2048-bit, 4096-bit (and ostensibily all others)
• SSH (RFC4716), (RFC 4716/SSH2)

var Rasha = require('rasha');
var jwk = require('rasha/fixtures/privkey-rsa-2048.jwk.json');

Rasha.export({ jwk: jwk }).then(function (pem) {
  // PEM in PKCS1 (traditional) format
  console.log(pem);
});

-----BEGIN RSA PRIVATE KEY-----
MIIEpAIBAAKCAQEAm2ttVBxPlWw06ZmGBWVDlfjkPAJ4DgnY0TrDwtCohHzLxGhD
NzUJefLukC+xu0LBKylYojT5vTkxaOhxeSYo31syu4WhxbkTBLICOFcCGMob6pSQ
38P8LdAIlb0pqDHxEJ9adWomjuFf.....5cCBahfsiNtNR6WV1/iCSuINYs6uPdA
Jlw7hm9m8TAmFWWyfL0s7wiRvAYkQvpxetorTwHJVLabBDJ+WBOAY2enOLHIRQv+
atAvHrLXjkUdzF96o0icyF6n7QzGfUPmeWGYg6BEClLS31Whe0eEVQ==
-----END RSA PRIVATE KEY-----

Advanced Options

format: 'pkcs8':

The default output format pkcs1 (RSA-specific format) is used for private keys. Use format: 'pkcs8' to output in PKCS#8 format instead.

Rasha.export({ jwk: jwk, format: 'pkcs8' }).then(function (pem) {
  // PEM in PKCS#8 format
  console.log(pem);
});

-----BEGIN PRIVATE KEY-----
MIIEvgIBADANBgkqhkiG9w0BAQEFAASCBKgwggSkAgEAAoIBAQCba21UHE+VbDTp
mYYFZUOV+OQ8AngOCdjROsPC0KiEfMvEaEM3NQl58u6QL7G7QsErKViiNPm9OTFo
6HF5JijfWzK7haHFuRMEsgI4VwIY.....LorV1ovjwKBgAJR1m8dYKemfaW8P9YZ
Uux7lwIFqF+yI201HpZXX+IJK4g1izq490AmXDuGb2bxMCYVZbJ8vSzvCJG8BiRC
+nF62itPAclUtpsEMn5YE4BjZ6c4schFC/5q0C8esteORR3MX3qjSJzIXqftDMZ9
Q+Z5YZiDoEQKUtLfVaF7R4RV
-----END PRIVATE KEY-----

format: 'ssh':

Although SSH uses PKCS#1 for private keys, it uses ts own special non-ASN1 format (affectionately known as rfc4716) for public keys. I got curious and then decided to add this format as well.

To get the same format as you would get with ssh-keygen, pass ssh as the format option:

Rasha.export({ jwk: jwk, format: 'ssh' }).then(function (pub) {
  // Special SSH2 Public Key format (RFC 4716)
  console.log(pub);
});

ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQCba21UHE.....Q02P1Eamz/nT4I3 rsa@localhost

public: 'true':

If a private key is used as input, a private key will be output.

If you'd like to output a public key instead you can pass public: true.

or format: 'spki'.

Rasha.export({ jwk: jwk, public: true }).then(function (pem) {
  // PEM in SPKI/PKIX format
  console.log(pem);
});

-----BEGIN PUBLIC KEY-----
MIIBCgKCAQEAm2ttVBxPlWw06ZmGBWVDlfjkPAJ4DgnY0TrDwtCohHzLxGhDNzUJ
efLukC+xu0LBKylYojT5vTkxaOhx.....TmzCh2ikrwTMja7mUdBJf2bK3By5AB0
Qi49OykUCfNZeQlEz7UNNj9RGps/50+CNwIDAQAB
-----END PUBLIC KEY-----

Testing

All cases are tested in test.sh.

You can compare these keys to the ones that you get from OpenSSL, OpenSSH/ssh-keygen, and WebCrypto:

# Generate 2048-bit RSA Keypair
openssl genrsa -out privkey-rsa-2048.pkcs1.pem 2048

# Convert PKCS1 (traditional) RSA Keypair to PKCS8 format
openssl rsa -in privkey-rsa-2048.pkcs1.pem -pubout -out pub-rsa-2048.spki.pem

# Export Public-only RSA Key in PKCS1 (traditional) format
openssl pkcs8 -topk8 -nocrypt -in privkey-rsa-2048.pkcs1.pem -out privkey-rsa-2048.pkcs8.pem

# Convert PKCS1 (traditional) RSA Public Key to SPKI/PKIX format
openssl rsa -in pub-rsa-2048.spki.pem -pubin -RSAPublicKey_out -out pub-rsa-2048.pkcs1.pem

# Convert RSA public key to SSH format
ssh-keygen -f ./pub-rsa-2048.spki.pem -i -mPKCS8 > ./pub-rsa-2048.ssh.pub

Goals of this project

• Focused support for 2048-bit and 4096-bit RSA keypairs (although any size is technically supported)
• Zero Dependencies
• VanillaJS
• Quality Code: Good comments and tests
• Convert both ways: PEM-to-JWK and JWK-to-PEM (also supports SSH pub files)
• Browser support as well (TODO)
• OpenSSL, ssh-keygen, and WebCrypto compatibility

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