Ancient Fossil Writeup | Huntress CTF 2024

All things are lost to time…

Ancient Fossil was a Forensics challenge released on Day #24 of the Huntress Capture the Flag (CTF) competition. We were provided a Fossil repository file, ancient.fossil, and tasked with finding the flag within the repository.

Using the fossil command-line tool, we see that there are 403 commits within the timeline:

$ fossil timeline -n 0 --type ci -R ancient.fossil | grep '^20' | wc -l
403

We then used the deconstruct option to extract all of the file artifacts from the repository:

$ fossil deconstruct -R ancient.fossil .

With all of these artifacts now extracted, we then searched recursively for the flag via grep:

$ grep -R "flag" .

Extracting artifacts via fossil and searching for the flag

flag{2ed33f365669ea9f10b1a4ea4566fe8c}

References

[1] Fossil. Fossil File Formats. https://fossil-scm.org/home/doc/hierarchical-manifests/www/fileformat.wiki