All we know is the file with the flag is named
down-at-the-bottom.txt … Disk image: dds2-alpine.flag.img.gz
First, let’s examine the file presented to us by the challenge using the
Decompressing the archive with the command
gzip -d results in the disk image file
Next, I used the
binwalk tool to extract data from the disk image. (
binwalk -e dds2-alpine.flag.img). This step produced the following.
file on 100000.ext suggests that it is an MBR boot sector image, and ext-root is the extracted root filesystem.
The description of the challenge mentioned a file called
down-at-the-bottom.txt. Let’s see if it’s somewhere in ext-root.
From here we simply have to read the text file with
cat to get our flag.