> irrgarten
> Be ready for some long running in the irrgarten.
> Connection:
> dig -t txt -p53535 @ 950ae439-d534-4b0c-8722-9ddcb97a50f6.maze.ctf.link
> 100 Basepoints + 100 Bonuspoints * min(1, 3/35 Solves) = 108 Points

When we run the command it returns a TXT record suggesting the we try ```down.<domain>```. When we run the following command we get a record of another subdomain:

dig -t txt -p53535 @ down.950ae439-d534-4b0c-8722-9ddcb97a50f6.maze.ctf.link

It seems that the nameserver is set up as a maze that we can traverse by specifying directions. If the direction exists for that particular node a name of the new subdomain node is returned. I was not sure what the valid directions were, but ```up```, ```down```, ```right```, and ```left``` seemed to work.

By specifying all directions on all nodes that we see we should eventually stumble upon a flag. When we see a new node we will add it to the "fresh" list, so that we could explore it. As we check all direction on a node we will add it to the "seen" list so that we won't have to check it again. Let's put this logic in a script:

import subprocess
import re

# new nodes
fresh = {}

# nodes that were already seen
seen = {}

def run_command(command):
p = subprocess.Popen(command.split(),stdout=subprocess.PIPE,stderr=subprocess.STDOUT)
return iter(p.stdout.readline, b'')

def run(node,dir=None):
global fresh, seen

# mark the node as seen
seen[node] = True

dir_str = ""
if dir != None:
dir_str = dir + "."

out = run_command("dig -t txt -p53535 @ {}{}.maze.ctf.link".format(dir_str, node))
in_answer = False
for x in out:
if ";; ANSWER SECTION" in x:
in_answer = True
if ";; AUTHORITY SECTION:" in x:

# if we are in the answer section and the line is not empty...
if in_answer and x.strip() != "":
val = x.strip()

# extract the new node name
m = re.search(r'IN CNAME\s+([0-9a-f-]{36}).maze.ctf.link.', val)
if m:
new_node = m.group(1)
# if we have not seen this node - add it to the "fresh" list
if new_node not in seen:
print "Adding node " + new_node
fresh[new_node] = True
# this is not a line containing new node - let's print it just in case it has the flag
print val

def explore(node):
print "Exploring " + node

fresh['950ae439-d534-4b0c-8722-9ddcb97a50f6'] = True
while True:

next_key = next(iter(fresh))

if len(fresh) == 0:

The script runs for a long while but eventually the flag is returned:

Adding node 20b3aaad-20c0-4da5-9ff1-f5c98fe23efc
Exploring 91e3cc82-ced7-4150-8eeb-0374c85fcb68
Adding node 4206714c-494f-4da4-aab7-cb0e523fd4ce
Exploring 4206714c-494f-4da4-aab7-cb0e523fd4ce
Adding node 20b3aaad-20c0-4da5-9ff1-f5c98fe23efc
Exploring 20b3aaad-20c0-4da5-9ff1-f5c98fe23efc
Adding node 8f3bb677-b8f8-4c48-a4c4-d8451f361d03
8f3bb677-b8f8-4c48-a4c4-d8451f361d03.maze.ctf.link. 3600 IN TXT "Flag:" "hxp{w3-h0p3-y0u-3nj0y3d-dd051n6-y0ur-dn5-1rr364r73n}"
Exploring 8f3bb677-b8f8-4c48-a4c4-d8451f361d03

The flag is ```hxp{w3-h0p3-y0u-3nj0y3d-dd051n6-y0ur-dn5-1rr364r73n}```.

Original writeup (https://0xd13a.github.io/ctfs/hxp2017/irrgarten/).