Entry Info

• Date: 2025-10-21
• BGGP Challenge: 6
• Name: bah
• Contact Info: bahorn in the BGGP discord
• Online Presence: https://b.horn.uk/
• Writeup Link: https://gist.github.com/bahorn/4a0d8505d84e7acab21358c39fdab4a7

File Info

• Target File Type: .curlrc
• Target File Size: 62
• SHA256 Hash: e664df8af2ac8d6bcef04ad9d7654012ab8e2d97

File Contents

Please encode the file as Base64

LUxvNgp1cmw9ZmlsZTovcHJvYy9zZWxmL2N3ZC8uY3VybHJjCnVybD1iaW5hcnkuZ29sZi81LzUKdXJsPWE=

Environment Info

Target Software and Version

Any modern curl version should work, I tested on curl 8.5.0, on a default Ubuntu 24.04 install.

Environment Setup

Description of Target Software's Environment (Platform/OS, Setup Instructions, etc.)

On any recent Ubuntu install:

$ apt-get install curl

Then run the entry by writing it $HOME/.curlrc and just invoking curl from the same directory.

Run curl like HOME=$PWD curl if you don't want to overwrite your users .curlrc.

Additional Info

Here attach any additional information about the file, including supporting notes, screenshots, videos, console output, etc.

NOTE: If this is an update to an existing entry, please include a link to your entry below this text. Reminder that authors can only update an entry once during BGGP.

This implements both BGGP 4 and 5. Copying the file by going to /proc/self/cwd/.curlrc and writing it to 6 with the -o option.
Returns 6 by passing curl a domain that doesn't resolve.
Downloading the BGGP5 file is as expected.

Expect the following output:

$ HOME=`pwd` curl
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100    62  100    62    0     0   672k      0 --:--:-- --:--:-- --:--:--  672k
Another #BGGP5 download!! @binarygolf https://binary.golf
curl: (6) Could not resolve host: a
$ echo $?
6
$ shasum .curlrc 6
e664df8af2ac8d6bcef04ad9d7654012ab8e2d97  .curlrc
e664df8af2ac8d6bcef04ad9d7654012ab8e2d97  6