old-keypairs.js/lib/ssh.js

81 lines
2.0 KiB
JavaScript

'use strict';
var SSH = module.exports;
var Enc = require('./encoding.js');
// 7 s s h - r s a
SSH.RSA = '00000007 73 73 68 2d 72 73 61'.replace(/\s+/g, '').toLowerCase();
SSH.parse = function (pem, jwk) {
var parts = pem.split(/\s+/);
var buf = Enc.base64ToBuf(parts[1]);
var els = [];
var index = 0;
var len;
var i = 0;
var offset = (buf.byteOffset || 0);
// using dataview to be browser-compatible (I do want _some_ code reuse)
var dv = new DataView(buf.buffer.slice(offset, offset + buf.byteLength));
var el;
if (SSH.RSA !== Enc.bufToHex(buf.slice(0, SSH.RSA.length/2))) {
throw new Error("does not lead with ssh header");
}
while (index < buf.byteLength) {
i += 1;
if (i > 3) { throw new Error("15+ elements, probably not a public ssh key"); }
len = dv.getUint32(index, false);
index += 4;
el = buf.slice(index, index + len);
// remove BigUInt '00' prefix
if (0x00 === el[0]) {
el = el.slice(1);
}
els.push(el);
index += len;
}
jwk.n = Enc.bufToUrlBase64(els[2]);
jwk.e = Enc.bufToUrlBase64(els[1]);
return jwk;
};
SSH.pack = function (opts) {
var jwk = opts.jwk;
var header = 'ssh-rsa';
var comment = opts.comment || 'rsa@localhost';
var e = SSH._padHexInt(Enc.base64ToHex(jwk.e));
var n = SSH._padHexInt(Enc.base64ToHex(jwk.n));
var hex = [
SSH._numToUint32Hex(header.length)
, Enc.strToHex(header)
, SSH._numToUint32Hex(e.length/2)
, e
, SSH._numToUint32Hex(n.length/2)
, n
].join('');
return [ header, Enc.hexToBase64(hex), comment ].join(' ');
};
SSH._numToUint32Hex = function (num) {
var hex = num.toString(16);
while (hex.length < 8) {
hex = '0' + hex;
}
return hex;
};
SSH._padHexInt = function (hex) {
// BigInt is negative if the high order bit 0x80 is set,
// so ASN1, SSH, and many other formats pad with '0x00'
// to signifiy a positive number.
var i = parseInt(hex.slice(0, 2), 16);
if (0x80 & i) {
return '00' + hex;
}
return hex;
};