// Copyright 2018 Joyent, Inc.

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

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

var pkcs1 = require('./pkcs1');
var pkcs8 = require('./pkcs8');
var sshpriv = require('./ssh-private');
var rfc4253 = require('./rfc4253');

var errors = require('../errors');

var OID_PBES2 = '1.2.840.113549.1.5.13';
var OID_PBKDF2 = '1.2.840.113549.1.5.12';

var OID_TO_CIPHER = {
	'1.2.840.113549.3.7': '3des-cbc',
	'2.16.840.1.101.3.4.1.2': 'aes128-cbc',
	'2.16.840.1.101.3.4.1.42': 'aes256-cbc'
};
var CIPHER_TO_OID = {};
Object.keys(OID_TO_CIPHER).forEach(function (k) {
	CIPHER_TO_OID[OID_TO_CIPHER[k]] = k;
});

var OID_TO_HASH = {
	'1.2.840.113549.2.7': 'sha1',
	'1.2.840.113549.2.9': 'sha256',
	'1.2.840.113549.2.11': 'sha512'
};
var HASH_TO_OID = {};
Object.keys(OID_TO_HASH).forEach(function (k) {
	HASH_TO_OID[OID_TO_HASH[k]] = k;
});

/*
 * For reading we support both PKCS#1 and PKCS#8. If we find a private key,
 * we just take the public component of it and use that.
 */
function read(buf, options, forceType) {
	var input = buf;
	if (typeof (buf) !== 'string') {
		assert.buffer(buf, 'buf');
		buf = buf.toString('ascii');
	}

	var lines = buf.trim().split(/[\r\n]+/g);

	var m;
	var si = -1;
	while (!m && si < lines.length) {
		m = lines[++si].match(/*JSSTYLED*/
		    /[-]+[ ]*BEGIN ([A-Z0-9][A-Za-z0-9]+ )?(PUBLIC|PRIVATE) KEY[ ]*[-]+/);
	}
	assert.ok(m, 'invalid PEM header');

	var m2;
	var ei = lines.length;
	while (!m2 && ei > 0) {
		m2 = lines[--ei].match(/*JSSTYLED*/
		    /[-]+[ ]*END ([A-Z0-9][A-Za-z0-9]+ )?(PUBLIC|PRIVATE) KEY[ ]*[-]+/);
	}
	assert.ok(m2, 'invalid PEM footer');

	/* Begin and end banners must match key type */
	assert.equal(m[2], m2[2]);
	var type = m[2].toLowerCase();

	var alg;
	if (m[1]) {
		/* They also must match algorithms, if given */
		assert.equal(m[1], m2[1], 'PEM header and footer mismatch');
		alg = m[1].trim();
	}

	lines = lines.slice(si, ei + 1);

	var headers = {};
	while (true) {
		lines = lines.slice(1);
		m = lines[0].match(/*JSSTYLED*/
		    /^([A-Za-z0-9-]+): (.+)$/);
		if (!m)
			break;
		headers[m[1].toLowerCase()] = m[2];
	}

	/* Chop off the first and last lines */
	lines = lines.slice(0, -1).join('');
	buf = Buffer.from(lines, 'base64');

	var cipher, key, iv;
	if (headers['proc-type']) {
		var parts = headers['proc-type'].split(',');
		if (parts[0] === '4' && parts[1] === 'ENCRYPTED') {
			if (typeof (options.passphrase) === 'string') {
				options.passphrase = Buffer.from(
				    options.passphrase, 'utf-8');
			}
			if (!Buffer.isBuffer(options.passphrase)) {
				throw (new errors.KeyEncryptedError(
				    options.filename, 'PEM'));
			} else {
				parts = headers['dek-info'].split(',');
				assert.ok(parts.length === 2);
				cipher = parts[0].toLowerCase();
				iv = Buffer.from(parts[1], 'hex');
				key = utils.opensslKeyDeriv(cipher, iv,
				    options.passphrase, 1).key;
			}
		}
	}

	if (alg && alg.toLowerCase() === 'encrypted') {
		var eder = new asn1.BerReader(buf);
		var pbesEnd;
		eder.readSequence();

		eder.readSequence();
		pbesEnd = eder.offset + eder.length;

		var method = eder.readOID();
		if (method !== OID_PBES2) {
			throw (new Error('Unsupported PEM/PKCS8 encryption ' +
			    'scheme: ' + method));
		}

		eder.readSequence();	/* PBES2-params */

		eder.readSequence();	/* keyDerivationFunc */
		var kdfEnd = eder.offset + eder.length;
		var kdfOid = eder.readOID();
		if (kdfOid !== OID_PBKDF2)
			throw (new Error('Unsupported PBES2 KDF: ' + kdfOid));
		eder.readSequence();
		var salt = eder.readString(asn1.Ber.OctetString, true);
		var iterations = eder.readInt();
		var hashAlg = 'sha1';
		if (eder.offset < kdfEnd) {
			eder.readSequence();
			var hashAlgOid = eder.readOID();
			hashAlg = OID_TO_HASH[hashAlgOid];
			if (hashAlg === undefined) {
				throw (new Error('Unsupported PBKDF2 hash: ' +
				    hashAlgOid));
			}
		}
		eder._offset = kdfEnd;

		eder.readSequence();	/* encryptionScheme */
		var cipherOid = eder.readOID();
		cipher = OID_TO_CIPHER[cipherOid];
		if (cipher === undefined) {
			throw (new Error('Unsupported PBES2 cipher: ' +
			    cipherOid));
		}
		iv = eder.readString(asn1.Ber.OctetString, true);

		eder._offset = pbesEnd;
		buf = eder.readString(asn1.Ber.OctetString, true);

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

		var cinfo = utils.opensshCipherInfo(cipher);

		cipher = cinfo.opensslName;
		key = utils.pbkdf2(hashAlg, salt, iterations, cinfo.keySize,
		    options.passphrase);
		alg = undefined;
	}

	if (cipher && key && iv) {
		var cipherStream = crypto.createDecipheriv(cipher, key, iv);
		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(buf);
		cipherStream.end();
		while ((chunk = cipherStream.read()) !== null)
			chunks.push(chunk);
		buf = Buffer.concat(chunks);
	}

	/* The new OpenSSH internal format abuses PEM headers */
	if (alg && alg.toLowerCase() === 'openssh')
		return (sshpriv.readSSHPrivate(type, buf, options));
	if (alg && alg.toLowerCase() === 'ssh2')
		return (rfc4253.readType(type, buf, options));

	var der = new asn1.BerReader(buf);
	der.originalInput = input;

	/*
	 * All of the PEM file types start with a sequence tag, so chop it
	 * off here
	 */
	der.readSequence();

	/* PKCS#1 type keys name an algorithm in the banner explicitly */
	if (alg) {
		if (forceType)
			assert.strictEqual(forceType, 'pkcs1');
		return (pkcs1.readPkcs1(alg, type, der));
	} else {
		if (forceType)
			assert.strictEqual(forceType, 'pkcs8');
		return (pkcs8.readPkcs8(alg, type, der));
	}
}

function write(key, options, type) {
	assert.object(key);

	var alg = {
	    'ecdsa': 'EC',
	    'rsa': 'RSA',
	    'dsa': 'DSA',
	    'ed25519': 'EdDSA'
	}[key.type];
	var header;

	var der = new asn1.BerWriter();

	if (PrivateKey.isPrivateKey(key)) {
		if (type && type === 'pkcs8') {
			header = 'PRIVATE KEY';
			pkcs8.writePkcs8(der, key);
		} else {
			if (type)
				assert.strictEqual(type, 'pkcs1');
			header = alg + ' PRIVATE KEY';
			pkcs1.writePkcs1(der, key);
		}

	} else if (Key.isKey(key)) {
		if (type && type === 'pkcs1') {
			header = alg + ' PUBLIC KEY';
			pkcs1.writePkcs1(der, key);
		} else {
			if (type)
				assert.strictEqual(type, 'pkcs8');
			header = 'PUBLIC KEY';
			pkcs8.writePkcs8(der, key);
		}

	} else {
		throw (new Error('key is not a Key or PrivateKey'));
	}

	var tmp = der.buffer.toString('base64');
	var len = tmp.length + (tmp.length / 64) +
	    18 + 16 + header.length*2 + 10;
	var buf = Buffer.alloc(len);
	var o = 0;
	o += buf.write('-----BEGIN ' + header + '-----\n', o);
	for (var i = 0; i < tmp.length; ) {
		var limit = i + 64;
		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));
}