Unable to add arguments to extensions

[plackyhacker]

Describe the bug
When I add arguments to an extension the client crashes and displays the following error:

panic: missing arg value: arg 'arguments' not registered

To Reproduce
Steps to reproduce the behavior:

Using the following .json file:

{
    "name": "SliverGetSystem",
    "command_name": "get-system",
    "version": "0.0.1",
    "extension_author": "plackyhacker",
    "original_author": "plackyhacker",
    "repo_url": "",
    "help": "Uses the SCM to get system on a local or remote host. Needs admin privileges.",
    "entrypoint": "Execute",
    "files": [
        {
            "os": "windows",
            "arch": "386",
            "path": "SliverGetSystem.x86.dll"
        },
        {
            "os": "windows",
            "arch": "amd64",
            "path": "SliverGetSystem.x64.dll"
        }
    ],
    "arguments": [
        {"name": "target", "type": "string", "desc": "The target.", "optional": false},
        {"name": "service", "type": "string", "desc": "The target service.", "optional": false},
        {"name": "payload", "type": "string", "desc": "The payload to execute.", "optional": false}
    ]
}

1. extensions install ./Payloads/SliverGetSystem
2. reload the client
3. use {guid}
4. get-system localhost service name "my payload"

Expected behavior
I would expect the extension to be loaded and executed on the target beacon.

Desktop (please complete the following information):

• OS: Linux parrot
• Version 6.1.0-1

[rkervella]

This is poorly documented at the moment, but extensions other than BOFs don't support typed arguments. Arguments are passed as a single string to the extension, and it's up to the extension code to parse it. You can check this example for reference.
This is planned for v1.6.

[plackyhacker]

Thanks for the quick response. The example given only uses numbers as args.

In my extension I am parsing the arg string myself but I noticed that ' and " characters seem to be taken out. If I pass:

get-system arg1 arg2 "arg3 with some spaces in it"

What I get on the input argsBuffer is:

arg1 arg2 arg3 with some spaces in it

This breaks the arguments down from the intended 3 to 8. Is there something I should be aware of when passing a string as arguments? I am using C to code the extension.

Thanks in advance.

[plackyhacker]

I should clarify, I have now removed the arguments from the json file.

[rkervella]

That's because the arguments are first interpreted as a string slice and then merged into a single string with strings.Join() with space as a delimiter:

sliver/client/command/extensions/load.go

Line 364 in f2a3915

extArgs := strings.Join(ctx.Args.StringList("arguments"), " ")

This is one of the shortcomings we have with extensions right now that will be solved in 1.6 once we merge #1424.
You could try something like this:

get-system arg1 arg2 '"arg3 with some spaces in it"'

[plackyhacker]

Brilliant, thanks for the information. I can work around this now I know.