ARA CTF 6.0

Writeup for GeoGuessr Challenge.

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Problem Setter

Solve: 1 / 128

Challenge	Category	Points
GeoGuessr-Pro	Misc	500

Misc

GeoGuessr-Pro

Description

How pro are you at the GeoGuessr? I challenge you to figure out the name of the area. But, this is a different GeoGuessr.

flag format: ARA6{area_name}

replace spaces with underscores and use lowercase.

Author: nblirwn

TL;DR

Reverse output gdal2tiles via tilemapresource.xml

Solve

Several files are provided:

• original-modified.pgw: A file containing spatial information for the raster image.

• original-modified.png.aux.xml: A metadata file from ArcGIS used to store additional information about the raster image.

• original-modified.png: The raster image file.

• original-modified.png.ovr: A file containing pyramid data for the raster image.

• original-modified.png.xml: An XML file containing metadata for the raster image.

Notice the tile-output folder. It contains file tilemapresource.xml and several directories. Therefore, tile-output folder is the output of the command gdal2tiles -z 0-5 original.tif tile-output.

gdal2tiles is a tool for converting a raster file into a tile layer map (tile-output folder).

Look at <title>original.tif</title>

By default, gdal2tiles places the original file name, which has been converted into a tile map, in the title of tilemapresource.xml.

How can player know this? You can search for what tilemapresource.xml is. You could even ask an AI.

I love ChatGPT

Or, watch this video: https://www.youtube.com/watch?v=31J3pPCStKw

Resources:

Programs — GDAL documentation

So what do you need to do? first, check the raster file using gdalinfo.

gdalinfo original-modified.png

There is an invalid angle, so the raster file does not appear in the correct location when opened using ArcGIS, Tile Map, or other tools.

There are many ways to fix it. I fixed it by converting the .png extension to .tif, then using the corner coordinates data from original.tif, which can be obtained through tilemapresource.xml:

<BoundingBox minx="8.49940967600014" miny="44.68120028221342" maxx="11.42827153744795" maxy="46.63789675900006"/>

1. Convert to .tif using gdal_translate:

gdal_translate -of GTiff original-modified.png original-modified.tif

1. Repair coordinates using gdal_edit:

gdal_edit -a_ullr 8.49940967600014 46.63789675900006 11.42827153744795 44.68120028221342 original-modified.tif

Check using gdalinfo, and the invalid angle will disappear, file was fixed. Last, open the .tif using ArcGIS or convert the .tif to a tile map with 10-12 zoom level (to be able to see that area, because it is very small.).

gdal2tiles -z 10-12 original-modified.tif solve

Output gdal2tiles

Then, you will see that the raster points to Lentate sul Seveso.

Flag: ARA6{lentate_sul_seveso}