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Filename : ssh-private.js
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// Copyright 2015 Joyent, Inc.

module.exports = {
	read: read,
	readSSHPrivate: readSSHPrivate,
	write: write
};

var assert = require('assert-plus');
var asn1 = require('asn1');
var Buffer = require('safer-buffer').Buffer;
var algs = require('../algs');
var utils = require('../utils');
var crypto = require('crypto');

var Key = require('../key');
var PrivateKey = require('../private-key');
var pem = require('./pem');
var rfc4253 = require('./rfc4253');
var SSHBuffer = require('../ssh-buffer');
var errors = require('../errors');

var bcrypt;

function read(buf, options) {
	return (pem.read(buf, options));
}

var MAGIC = 'openssh-key-v1';

function readSSHPrivate(type, buf, options) {
	buf = new SSHBuffer({buffer: buf});

	var magic = buf.readCString();
	assert.strictEqual(magic, MAGIC, 'bad magic string');

	var cipher = buf.readString();
	var kdf = buf.readString();
	var kdfOpts = buf.readBuffer();

	var nkeys = buf.readInt();
	if (nkeys !== 1) {
		throw (new Error('OpenSSH-format key file contains ' +
		    'multiple keys: this is unsupported.'));
	}

	var pubKey = buf.readBuffer();

	if (type === 'public') {
		assert.ok(buf.atEnd(), 'excess bytes left after key');
		return (rfc4253.read(pubKey));
	}

	var privKeyBlob = buf.readBuffer();
	assert.ok(buf.atEnd(), 'excess bytes left after key');

	var kdfOptsBuf = new SSHBuffer({ buffer: kdfOpts });
	switch (kdf) {
	case 'none':
		if (cipher !== 'none') {
			throw (new Error('OpenSSH-format key uses KDF "none" ' +
			     'but specifies a cipher other than "none"'));
		}
		break;
	case 'bcrypt':
		var salt = kdfOptsBuf.readBuffer();
		var rounds = kdfOptsBuf.readInt();
		var cinf = utils.opensshCipherInfo(cipher);
		if (bcrypt === undefined) {
			bcrypt = require('bcrypt-pbkdf');
		}

		if (typeof (options.passphrase) === 'string') {
			options.passphrase = Buffer.from(options.passphrase,
			    'utf-8');
		}
		if (!Buffer.isBuffer(options.passphrase)) {
			throw (new errors.KeyEncryptedError(
			    options.filename, 'OpenSSH'));
		}

		var pass = new Uint8Array(options.passphrase);
		var salti = new Uint8Array(salt);
		/* Use the pbkdf to derive both the key and the IV. */
		var out = new Uint8Array(cinf.keySize + cinf.blockSize);
		var res = bcrypt.pbkdf(pass, pass.length, salti, salti.length,
		    out, out.length, rounds);
		if (res !== 0) {
			throw (new Error('bcrypt_pbkdf function returned ' +
			    'failure, parameters invalid'));
		}
		out = Buffer.from(out);
		var ckey = out.slice(0, cinf.keySize);
		var iv = out.slice(cinf.keySize, cinf.keySize + cinf.blockSize);
		var cipherStream = crypto.createDecipheriv(cinf.opensslName,
		    ckey, iv);
		cipherStream.setAutoPadding(false);
		var chunk, chunks = [];
		cipherStream.once('error', function (e) {
			if (e.toString().indexOf('bad decrypt') !== -1) {
				throw (new Error('Incorrect passphrase ' +
				    'supplied, could not decrypt key'));
			}
			throw (e);
		});
		cipherStream.write(privKeyBlob);
		cipherStream.end();
		while ((chunk = cipherStream.read()) !== null)
			chunks.push(chunk);
		privKeyBlob = Buffer.concat(chunks);
		break;
	default:
		throw (new Error(
		    'OpenSSH-format key uses unknown KDF "' + kdf + '"'));
	}

	buf = new SSHBuffer({buffer: privKeyBlob});

	var checkInt1 = buf.readInt();
	var checkInt2 = buf.readInt();
	if (checkInt1 !== checkInt2) {
		throw (new Error('Incorrect passphrase supplied, could not ' +
		    'decrypt key'));
	}

	var ret = {};
	var key = rfc4253.readInternal(ret, 'private', buf.remainder());

	buf.skip(ret.consumed);

	var comment = buf.readString();
	key.comment = comment;

	return (key);
}

function write(key, options) {
	var pubKey;
	if (PrivateKey.isPrivateKey(key))
		pubKey = key.toPublic();
	else
		pubKey = key;

	var cipher = 'none';
	var kdf = 'none';
	var kdfopts = Buffer.alloc(0);
	var cinf = { blockSize: 8 };
	var passphrase;
	if (options !== undefined) {
		passphrase = options.passphrase;
		if (typeof (passphrase) === 'string')
			passphrase = Buffer.from(passphrase, 'utf-8');
		if (passphrase !== undefined) {
			assert.buffer(passphrase, 'options.passphrase');
			assert.optionalString(options.cipher, 'options.cipher');
			cipher = options.cipher;
			if (cipher === undefined)
				cipher = 'aes128-ctr';
			cinf = utils.opensshCipherInfo(cipher);
			kdf = 'bcrypt';
		}
	}

	var privBuf;
	if (PrivateKey.isPrivateKey(key)) {
		privBuf = new SSHBuffer({});
		var checkInt = crypto.randomBytes(4).readUInt32BE(0);
		privBuf.writeInt(checkInt);
		privBuf.writeInt(checkInt);
		privBuf.write(key.toBuffer('rfc4253'));
		privBuf.writeString(key.comment || '');

		var n = 1;
		while (privBuf._offset % cinf.blockSize !== 0)
			privBuf.writeChar(n++);
		privBuf = privBuf.toBuffer();
	}

	switch (kdf) {
	case 'none':
		break;
	case 'bcrypt':
		var salt = crypto.randomBytes(16);
		var rounds = 16;
		var kdfssh = new SSHBuffer({});
		kdfssh.writeBuffer(salt);
		kdfssh.writeInt(rounds);
		kdfopts = kdfssh.toBuffer();

		if (bcrypt === undefined) {
			bcrypt = require('bcrypt-pbkdf');
		}
		var pass = new Uint8Array(passphrase);
		var salti = new Uint8Array(salt);
		/* Use the pbkdf to derive both the key and the IV. */
		var out = new Uint8Array(cinf.keySize + cinf.blockSize);
		var res = bcrypt.pbkdf(pass, pass.length, salti, salti.length,
		    out, out.length, rounds);
		if (res !== 0) {
			throw (new Error('bcrypt_pbkdf function returned ' +
			    'failure, parameters invalid'));
		}
		out = Buffer.from(out);
		var ckey = out.slice(0, cinf.keySize);
		var iv = out.slice(cinf.keySize, cinf.keySize + cinf.blockSize);

		var cipherStream = crypto.createCipheriv(cinf.opensslName,
		    ckey, iv);
		cipherStream.setAutoPadding(false);
		var chunk, chunks = [];
		cipherStream.once('error', function (e) {
			throw (e);
		});
		cipherStream.write(privBuf);
		cipherStream.end();
		while ((chunk = cipherStream.read()) !== null)
			chunks.push(chunk);
		privBuf = Buffer.concat(chunks);
		break;
	default:
		throw (new Error('Unsupported kdf ' + kdf));
	}

	var buf = new SSHBuffer({});

	buf.writeCString(MAGIC);
	buf.writeString(cipher);	/* cipher */
	buf.writeString(kdf);		/* kdf */
	buf.writeBuffer(kdfopts);	/* kdfoptions */

	buf.writeInt(1);		/* nkeys */
	buf.writeBuffer(pubKey.toBuffer('rfc4253'));

	if (privBuf)
		buf.writeBuffer(privBuf);

	buf = buf.toBuffer();

	var header;
	if (PrivateKey.isPrivateKey(key))
		header = 'OPENSSH PRIVATE KEY';
	else
		header = 'OPENSSH PUBLIC KEY';

	var tmp = buf.toString('base64');
	var len = tmp.length + (tmp.length / 70) +
	    18 + 16 + header.length*2 + 10;
	buf = Buffer.alloc(len);
	var o = 0;
	o += buf.write('-----BEGIN ' + header + '-----\n', o);
	for (var i = 0; i < tmp.length; ) {
		var limit = i + 70;
		if (limit > tmp.length)
			limit = tmp.length;
		o += buf.write(tmp.slice(i, limit), o);
		buf[o++] = 10;
		i = limit;
	}
	o += buf.write('-----END ' + header + '-----\n', o);

	return (buf.slice(0, o));
}