Generating zone files from Route53

Recently I found myself wanting to do some analysis on all of our DNS entires stored in AWS’s Route53 for security reasons (specifically to prevent subdomain takeover attacks, I’ll probably write that up soon). In doing so, I realized that while Route53 has the ability to import a zone file, it’s not possible to export one.

To some extent, this makes sense. Since Route53 supports ALIAS records (which can automatically determine their values based on other AWS products, such as an ELB changing its public IP) and those aren’t actually ‘real’ DNS entries, things will get confused. But I don’t currently intend to re-import these zone files, just use them. So let’s see what we can do.

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Advent of Code 2017

As I did with last year / yesterday, I’ve written up a series of posts for the Advent of Code 2017 problems. Again, I didn’t manage to write them up as I did them, but this time around I least I finished mostly on time.

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Advent of Code 2016

As I did last year, I’m going to solve the Advent of Code problems again this year.

Or that was the plan. It turns out that instead I put down my blog for almost a year and a half and never quite got around to doing these problems. So I’m actually backdating these posts from the early days of 2018 to where they would have been had I solved them on time. They’re still interesting problems, so give them a read.

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AoC 2017 Day 25: Turing

Source: The Halting Problem

Part 1: Implement a Turing machine defined as such:

Begin in state A.
Perform a diagnostic checksum after 6 steps.

In state A:
  If the current value is 0:
    - Write the value 1.
    - Move one slot to the right.
    - Continue with state B.
  If the current value is 1:
    - Write the value 0.
    - Move one slot to the left.
    - Continue with state B.

...

What is the final number of 1s on the tape?

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AoC 2017 Day 24: Maker Of Bridges

Source: Electromagnetic Moat

Part 1: Given a series of reversible components of the form 3/4 (can connect a 3 on one end to a 4 on the other), form a bridge of components. The bridge’s strength is equal to the sum of component values. So 0/3, 3/7, and 7/4 has a strength of 0+3 + 3+7 + 7+4 = 24.

What is the strongest possible bridge?

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AoC 2017 Day 23: Duetvmc

Source: Coprocessor Conflagration

Part 1: Create a variation of the previous DuetVM with only the following four instructions:

  • set X Y sets register X to Y
  • sub X Y set register X to X - Y
  • mul X Y sets register X to X * Y
  • jnz X Y jumps with an offset of the value of Y, iff X is not equal to zero

If you run the given program, how many times is mul invoked?

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AoC 2017 Day 22: Langton's Ant

Source: Sporifica Virus

Part 1: Implement a cellular automaton on an infinite grid of . and # pixels such that:

  1. Start at (0, 0), facing Up
  2. Repeat:
    • If the cursor is on . swap it to # and turn Left
    • If the cursor is on # swap it to . and turn Right
    • Either way, after turning, move forward once

After 10,000 iterations, how many pixels were turned from . to #?

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AoC 2017 Day 21: Fractal Expander

Source: Fractal Art

Part 1: Start with an input image made of . and # pixels. For n iterations, break the image into blocks:

  • If the current size is even, break the image into 2x2 chunks and replace each with a 3x3 chunk
  • If the current size is odd, break the image into 3x3 chunks and replace each with a 4x4 chunk

The replacement rules will be specified in the following format (example is a 3x3 -> 4x4 rule):

.#./..#/### => #..#/..../..../#..#

In that example, replace this:

.#.
..#
###

With this:

#..#
....
....
#..#

Any rotation or reflection of a chunk can be used to match the input of a replacement rule.

After n = 18 iterations, how many # pixels are there?

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AoC 2017 Day 19: Networkout

Source: A Series of Tubes

Part 1: Take a network diagram of the following form:

    |          
    |  +--+    
    A  |  C    
F---|--|-E---+
    |  |  |  D
    +B-+  +--+

Starting at the single node at the top and following the lines, what order would the nodes be visited in?

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