The handler is a special container that enables challenge instance hosting/handling. Developers can create jail configurations that allow challenge creators to manage their challenge's jail allowing for more variety of challenges to be hosted compared to being stuck running a single binary.
These configurations are linked to challenge entries following the rule that one challenge gets at most one configuration reference. These configurations allow easy handling of controlling what files are read-only mounted in the jail along with configuring the entrypoint executable that is initially propogated via nsjail.
These files are written in JSON
| Attribute | Description |
|---|---|
name |
Name of the configuration. |
author |
Creator meta-data. |
files |
List of files contained in the generated jail. |
entrypoint |
Executable initially executed by nsjail. |
The files attribute when parsed will automatically append entrypoint within the list if it is not present. For challenge files (excludes natural system files) within the jail, they will always exist at the root of the jail.
{
"name":"n0Auth",
"author":"g3ne1c",
"files":[
"/vuln_comp",
"/lib/x86_64-linux-gnu/libc.so.6"
],
"entrypoint":"/vuln"
}As you can see the files vuln and vuln_comp are ctf challenge files, thus exist within the root directory, while natural files like libc.so.6 use the absolute system path because these files are aquired from the jail host file-system.