old-keypairs.js/lib/x509-ec-parser.js

'use strict';

var Enc = require('./encoding.js');
var x509 = module.exports;

// 1.2.840.10045.3.1.7
// prime256v1 (ANSI X9.62 named elliptic curve)
var OBJ_ID_EC_256  = '06 08 2A8648CE3D030107'.replace(/\s+/g, '').toLowerCase();
// 1.3.132.0.34
// secp384r1 (SECG (Certicom) named elliptic curve)
var OBJ_ID_EC_384 = '06 05 2B81040022'.replace(/\s+/g, '').toLowerCase();

x509.parseSec1 = function parseEcOnlyPrivkey(u8, jwk) {
  var index = 7;
  var len = 32;
  var olen = OBJ_ID_EC_256.length/2;

  if ("P-384" === jwk.crv) {
    olen = OBJ_ID_EC_384.length/2;
    index = 8;
    len = 48;
  }
  if (len !== u8[index - 1]) {
    throw new Error("Unexpected bitlength " + len);
  }

  // private part is d
  var d = u8.slice(index, index + len);
  // compression bit index
  var ci = index + len + 2 + olen + 2 + 3;
  var c = u8[ci];
  var x, y;

  if (0x04 === c) {
    y = u8.slice(ci + 1 + len, ci + 1 + len + len);
  } else if (0x02 !== c) {
    throw new Error("not a supported EC private key");
  }
  x = u8.slice(ci + 1, ci + 1 + len);

  return {
    kty: jwk.kty
  , crv: jwk.crv
  , d: Enc.bufToUrlBase64(d)
  //, dh: Enc.bufToHex(d)
  , x: Enc.bufToUrlBase64(x)
  //, xh: Enc.bufToHex(x)
  , y: Enc.bufToUrlBase64(y)
  //, yh: Enc.bufToHex(y)
  };
};

x509.parsePkcs8 = function parseEcPkcs8(u8, jwk) {
  var index = 24 + (OBJ_ID_EC_256.length/2);
  var len = 32;
  if ("P-384" === jwk.crv) {
    index = 24 + (OBJ_ID_EC_384.length/2) + 2;
    len = 48;
  }

  //console.log(index, u8.slice(index));
  if (0x04 !== u8[index]) {
    //console.log(jwk);
    throw new Error("privkey not found");
  }
  var d = u8.slice(index+2, index+2+len);
  var ci = index+2+len+5;
  var xi = ci+1;
  var x = u8.slice(xi, xi + len);
  var yi = xi+len;
  var y;
  if (0x04 === u8[ci]) {
    y = u8.slice(yi, yi + len);
  } else if (0x02 !== u8[ci]) {
    throw new Error("invalid compression bit (expected 0x04 or 0x02)");
  }

  return {
    kty: jwk.kty
  , crv: jwk.crv
  , d: Enc.bufToUrlBase64(d)
  //, dh: Enc.bufToHex(d)
  , x: Enc.bufToUrlBase64(x)
  //, xh: Enc.bufToHex(x)
  , y: Enc.bufToUrlBase64(y)
  //, yh: Enc.bufToHex(y)
  };
};

x509.parseSpki = function parsePem(u8, jwk) {
  var ci = 16 + OBJ_ID_EC_256.length/2;
  var len = 32;

  if ("P-384" === jwk.crv) {
    ci = 16 + OBJ_ID_EC_384.length/2;
    len = 48;
  }

  var c = u8[ci];
  var xi = ci + 1;
  var x = u8.slice(xi, xi + len);
  var yi = xi + len;
  var y;
  if (0x04 === c) {
    y = u8.slice(yi, yi + len);
  } else if (0x02 !== c) {
    throw new Error("not a supported EC private key");
  }

  return {
    kty: jwk.kty
  , crv: jwk.crv
  , x: Enc.bufToUrlBase64(x)
  //, xh: Enc.bufToHex(x)
  , y: Enc.bufToUrlBase64(y)
  //, yh: Enc.bufToHex(y)
  };
};
x509.parsePkix = x509.parseSpki;