Added post about Synology password.

know-how/hacking/_posts/2016-01-26-synology-telnet-password.md

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+---
+title: Synology Telnet password
+language: en
+layout: default
+created: 2016-01-26 19:54:55 +0100
+updated: 2016-01-26 19:54:55 +0100
+toc: true
+tags:
+  - know-how
+  - hacking
+  - hardware
+  - synology
+  - xpenology
+  - telnet
+  - password
+---
+If you ever had a problem with your Synology DiskStation, you might have
+stumbled upon the emergency telnet access or even the serial port on the PCB.
+
+Or maybe you just wanted to set it (or XPEnology) up and needed the `root`
+password to configure a static IP in order to access the web based setup.
+
+But what is the password?
+
+Luckily, Gui Ambros took a look at the GPL'ed source code and
+[made a small C snippet](https://wrgms.com/synologys-secret-telnet-password/)
+to generate that password.
+
+It is based on the current day and month.
+
+<script>
+var today = new Date();
+var d = today.getDate();
+var m = today.getMonth() + 1;
+
+var mh = m.toString(16);
+var pm = ('0' + m).substr(-2);
+var pdh = ('0' + d.toString(16)).substr(-2);
+
+var months = ['January', 'February', 'March', 'April', 'May', 'June', 'July',
+              'August', 'September', 'October', 'November', 'December'];
+
+function gcd(x, y) {
+  return y?gcd(y, x%y):Math.abs(x);
+}
+
+var x = gcd(d, m);
+var px = ('0' + x).substr(-2);
+
+document.write('Today\'s (' + d + ' ' + months[m-1] + ') password is: <code>' + mh + pm + '-' + pdh + px + '</code>');
+</script>
+
+The structure is like this:
+
+1. Current month in hexadecimal, lower case (Jan:`1`, Feb:`2`, … , Oct:`a`, Nov:`b`, Dec:`c`)
+1. Current month in decimal, 2 characters, zero padded (`01`, `02`, …, `11`, `12`)
+1. Minus (`-`)
+1. Current day of the month in hex, 2 characters, zero padded, lower case (`01`, `02`, …, 10:`0a`, …, 30:`1e`, 31:`1f`)
+1. [Greatest common divisor](https://en.wikipedia.org/wiki/Greatest_common_divisor) between month and day, 2 characters, zero padded (`01`, …, `12`)
+
+Here is a small Python snippet to calculate today's password:
+
+{% highlight python %}
+from datetime import date
+import fractions
+
+today = date.today()
+m = today.month
+d = today.day
+
+print("%x%02d-%02x%02d" % (m, m, d, fractions.gcd(d, m)))
+{% endhighlight %}
+
+And if you look at the source code of this page, you'll find the JavaScript
+which calculates the code displayed above.
+
+<p><div class="notetip" markdown="1">
+If the generated password doesn't work, also try `101-0101`. After a bootup, the
+time might be reset to 1 January 1970.
+</div></p>
+
+By the way: This password doesn't work for SSH after you've setup your Synology.
+After the setup, the `root` password is that of your `admin` user.