rework code to enable/disable remote support

we had a generic ssh key management api. this was causing issues because
the ssh format is more complicated than what we had implemented. currently,
the only use case we have is to add our ssh key.

Fixes #600

src/support.js

@@ -0,0 +1,66 @@
+'use strict';
+
+exports = module.exports = {
+    getRemoteSupport: getRemoteSupport,
+    enableRemoteSupport: enableRemoteSupport,
+
+    SupportError: SupportError
+};
+
+let assert = require('assert'),
+    config = require('./config.js'),
+    shell = require('./shell.js'),
+    once = require('once'),
+    path = require('path'),
+    util = require('util');
+
+var AUTHORIZED_KEYS_FILEPATH = config.TEST ? path.join(config.baseDir(), 'authorized_keys') : ((config.provider() === 'ec2' || config.provider() === 'lightsail' || config.provider() === 'ami') ? '/home/ubuntu/.ssh/authorized_keys' : '/root/.ssh/authorized_keys'),
+    AUTHORIZED_KEYS_USER = config.TEST ? process.getuid() : ((config.provider() === 'ec2' || config.provider() === 'lightsail' || config.provider() === 'ami') ? 'ubuntu' : 'root'),
+    AUTHORIZED_KEYS_CMD = path.join(__dirname, 'scripts/remotesupport.sh');
+
+function SupportError(reason, errorOrMessage) {
+    assert.strictEqual(typeof reason, 'string');
+    assert(errorOrMessage instanceof Error || typeof errorOrMessage === 'string' || typeof errorOrMessage === 'undefined');
+
+    Error.call(this);
+    Error.captureStackTrace(this, this.constructor);
+
+    this.name = this.constructor.name;
+    this.reason = reason;
+    if (typeof errorOrMessage === 'undefined') {
+        this.message = reason;
+    } else if (typeof errorOrMessage === 'string') {
+        this.message = errorOrMessage;
+    } else {
+        this.message = 'Internal error';
+        this.nestedError = errorOrMessage;
+    }
+}
+util.inherits(SupportError, Error);
+SupportError.NOT_FOUND = 'Not found';
+SupportError.INVALID_KEY = 'Invalid key';
+SupportError.INTERNAL_ERROR = 'Internal Error';
+
+function getRemoteSupport(callback) {
+    assert.strictEqual(typeof callback, 'function');
+
+    callback = once(callback); // exit may or may not be called after an 'error'
+
+    let result = '';
+    let cp = shell.sudo('support', [ AUTHORIZED_KEYS_CMD, 'is-enabled', AUTHORIZED_KEYS_FILEPATH ], {}, function (error) {
+        if (error) callback(new SupportError(SupportError.INTERNAL_ERROR, error));
+
+        callback(null, { enabled: result.trim() === 'true' });
+    });
+    cp.stdout.on('data', (data) => result = result + data.toString('utf8'));
+}
+
+function enableRemoteSupport(enable, callback) {
+    assert.strictEqual(typeof callback, 'function');
+
+    shell.sudo('support', [ AUTHORIZED_KEYS_CMD, enable ? 'enable' : 'disable', AUTHORIZED_KEYS_FILEPATH, AUTHORIZED_KEYS_USER ], {}, function (error) {
+        if (error) callback(new SupportError(SupportError.INTERNAL_ERROR, error));
+
+        callback();
+    });
+}