source: trip-planner-front/node_modules/sshpk/lib/formats/auto.js@ e29cc2e

// Copyright 2018 Joyent, Inc.

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

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

var pem = require('./pem');
var ssh = require('./ssh');
var rfc4253 = require('./rfc4253');
var dnssec = require('./dnssec');
var putty = require('./putty');

var DNSSEC_PRIVKEY_HEADER_PREFIX = 'Private-key-format: v1';

function read(buf, options) {
        if (typeof (buf) === 'string') {
                if (buf.trim().match(/^[-]+[ ]*BEGIN/))
                        return (pem.read(buf, options));
                if (buf.match(/^\s*ssh-[a-z]/))
                        return (ssh.read(buf, options));
                if (buf.match(/^\s*ecdsa-/))
                        return (ssh.read(buf, options));
                if (buf.match(/^putty-user-key-file-2:/i))
                        return (putty.read(buf, options));
                if (findDNSSECHeader(buf))
                        return (dnssec.read(buf, options));
                buf = Buffer.from(buf, 'binary');
        } else {
                assert.buffer(buf);
                if (findPEMHeader(buf))
                        return (pem.read(buf, options));
                if (findSSHHeader(buf))
                        return (ssh.read(buf, options));
                if (findPuTTYHeader(buf))
                        return (putty.read(buf, options));
                if (findDNSSECHeader(buf))
                        return (dnssec.read(buf, options));
        }
        if (buf.readUInt32BE(0) < buf.length)
                return (rfc4253.read(buf, options));
        throw (new Error('Failed to auto-detect format of key'));
}

function findPuTTYHeader(buf) {
        var offset = 0;
        while (offset < buf.length &&
            (buf[offset] === 32 || buf[offset] === 10 || buf[offset] === 9))
                ++offset;
        if (offset + 22 <= buf.length &&
            buf.slice(offset, offset + 22).toString('ascii').toLowerCase() ===
            'putty-user-key-file-2:')
                return (true);
        return (false);
}

function findSSHHeader(buf) {
        var offset = 0;
        while (offset < buf.length &&
            (buf[offset] === 32 || buf[offset] === 10 || buf[offset] === 9))
                ++offset;
        if (offset + 4 <= buf.length &&
            buf.slice(offset, offset + 4).toString('ascii') === 'ssh-')
                return (true);
        if (offset + 6 <= buf.length &&
            buf.slice(offset, offset + 6).toString('ascii') === 'ecdsa-')
                return (true);
        return (false);
}

function findPEMHeader(buf) {
        var offset = 0;
        while (offset < buf.length &&
            (buf[offset] === 32 || buf[offset] === 10))
                ++offset;
        if (buf[offset] !== 45)
                return (false);
        while (offset < buf.length &&
            (buf[offset] === 45))
                ++offset;
        while (offset < buf.length &&
            (buf[offset] === 32))
                ++offset;
        if (offset + 5 > buf.length ||
            buf.slice(offset, offset + 5).toString('ascii') !== 'BEGIN')
                return (false);
        return (true);
}

function findDNSSECHeader(buf) {
        // private case first
        if (buf.length <= DNSSEC_PRIVKEY_HEADER_PREFIX.length)
                return (false);
        var headerCheck = buf.slice(0, DNSSEC_PRIVKEY_HEADER_PREFIX.length);
        if (headerCheck.toString('ascii') === DNSSEC_PRIVKEY_HEADER_PREFIX)
                return (true);

        // public-key RFC3110 ?
        // 'domain.com. IN KEY ...' or 'domain.com. IN DNSKEY ...'
        // skip any comment-lines
        if (typeof (buf) !== 'string') {
                buf = buf.toString('ascii');
        }
        var lines = buf.split('\n');
        var line = 0;
        /* JSSTYLED */
        while (lines[line].match(/^\;/))
                line++;
        if (lines[line].toString('ascii').match(/\. IN KEY /))
                return (true);
        if (lines[line].toString('ascii').match(/\. IN DNSKEY /))
                return (true);
        return (false);
}

function write(key, options) {
        throw (new Error('"auto" format cannot be used for writing'));
}