function to test ssh safety

lib/ssh.js

@@ -0,0 +1,72 @@
+'use strict';
+
+/*global Promise*/
+var PromiseA = Promise;
+var crypto = require('crypto');
+var util = require('util');
+var readFile = util.promisify(require('fs').readFile);
+var exec = require('child_process').exec;
+
+function sshAllowsPassword(user) {
+  // SSH on Windows is a thing now (beta 2015, standard 2018)
+  // https://stackoverflow.com/questions/313111/is-there-a-dev-null-on-windows
+  var nullfile = '/dev/null';
+  if (/^win/i.test(process.platform)) {
+    nullfile = 'NUL';
+  }
+  var args = [
+    'ssh', '-v', '-n'
+  , '-o', 'Batchmode=yes'
+  , '-o', 'StrictHostKeyChecking=no'
+  , '-o', 'UserKnownHostsFile=' + nullfile
+  , user + '@localhost'
+  , '| true'
+  ];
+  return new PromiseA(function (resolve) {
+    // not using promisify because all 3 arguments convey information
+    exec(args.join(' '), function (err, stdout, stderr) {
+      stdout = (stdout||'').toString('utf8');
+      stderr = (stderr||'').toString('utf8');
+      if (/\bpassword\b/.test(stdout) || /\bpassword\b/.test(stderr)) {
+        resolve(true);
+        return;
+      }
+      if (/\bAuthentications\b/.test(stdout) || /\bAuthentications\b/.test(stderr)) {
+        resolve(false);
+        return;
+      }
+      resolve();
+    });
+  });
+}
+
+module.exports.checkSecurity = function () {
+  var conf = {};
+  var sshdConf = '/etc/ssh/sshd_config';
+  var noRootPasswordRe = /(^|[\r\n]+)\s*PermitRootLogin\s+(prohibit-password|without-password|no)\s*/i;
+  var noPasswordRe = /(^|[\r\n]+)\s*PasswordAuthentication\s+no\s*/i;
+  return readFile(sshdConf, null).then(function (sshd) {
+    sshd = sshd.toString('utf8');
+    conf.disallowPasswordRoot = noRootPasswordRe.test(sshd);
+    conf.disallowPassword = noPasswordRe.test(sshd);
+  }).catch(function () {
+    // ignore error as that might not be the correct sshd_config location
+  }).then(function () {
+    var doesntExist = crypto.randomBytes(16).toString('hex');
+    return sshAllowsPassword(doesntExist).then(function (maybe) {
+      conf.allowsPassword = maybe;
+      return sshAllowsPassword('root').then(function (maybe) {
+        conf.allowsRootPassword = maybe;
+      });
+    });
+  }).then(function () {
+    return conf;
+  });
+};
+
+if (require.main === module) {
+  module.exports.checkSecurity().then(function (conf) {
+    console.log(conf);
+    return conf;
+  });
+}