If user formats rawURL to contain '#' before channel name - execution ends up in segfault

[atighineanu]

When I tried shoutrrr code for a rocket chat automated notification, and formatted the channel name with a '#' prefix - that is what I got:

go run cli/main.go send --url "rocketchat://shoutrrr@<myhost>/<tokenA>/<tokenB>/#general" --message "hello hello"
panic: runtime error: slice bounds out of range [:1] with length 0
goroutine 1 [running]:
github.com/containrrr/shoutrrr/pkg/services/rocketchat.(*Config).SetURL(0xc0000c27e0, 0xc0000d8120, 0x1548080, 0xc0000b8980)
        /Users/alexeitighineanu/go/src/github.com/shoutrrr/pkg/services/rocketchat/rocketchat_config.go:69 +0x77d
github.com/containrrr/shoutrrr/pkg/services/rocketchat.(*Service).Initialize(0xc0000b8980, 0xc0000d8120, 0xc0000c8280, 0xa, 0xc0000b1938)
        /Users/alexeitighineanu/go/src/github.com/shoutrrr/pkg/services/rocketchat/rocketchat.go:24 +0x85
github.com/containrrr/shoutrrr/pkg/router.(*ServiceRouter).initService(0x191ce20, 0x7ffeefbff694, 0x73, 0x15aa11a, 0x6, 0x15d0868, 0x1501b60)
        /Users/alexeitighineanu/go/src/github.com/shoutrrr/pkg/router/router.go:171 +0xe6
github.com/containrrr/shoutrrr/pkg/router.(*ServiceRouter).Locate(...)
        /Users/alexeitighineanu/go/src/github.com/shoutrrr/pkg/router/router.go:203
github.com/containrrr/shoutrrr.Send(0x7ffeefbff694, 0x73, 0x7ffeefbff712, 0x15, 0x15, 0x0)
        /Users/alexeitighineanu/go/src/github.com/shoutrrr/shoutrrr.go:19 +0x45
github.com/containrrr/shoutrrr/cli/cmd/send.Run(0x1914580, 0xc0000dce00, 0x0, 0x4)
        /Users/alexeitighineanu/go/src/github.com/shoutrrr/cli/cmd/send/send.go:49 +0x146
github.com/spf13/cobra.(*Command).execute(0x1914580, 0xc0000dcdc0, 0x4, 0x4, 0x1914580, 0xc0000dcdc0)
        /Users/alexeitighineanu/go/pkg/mod/github.com/spf13/[email protected]/command.go:842 +0x2c2
github.com/spf13/cobra.(*Command).ExecuteC(0x19142e0, 0x0, 0x0, 0x0)
        /Users/alexeitighineanu/go/pkg/mod/github.com/spf13/[email protected]/command.go:943 +0x336
github.com/spf13/cobra.(*Command).Execute(...)
        /Users/alexeitighineanu/go/pkg/mod/github.com/spf13/[email protected]/command.go:883
main.main()
        /Users/alexeitighineanu/go/src/github.com/shoutrrr/cli/main.go:9 +0x31
exit status 2

It is pretty confusing given that it is caused by a '#' symbol. I've discovered it is caused by this statement in
pkg/services/rocketchat_configure.go:

if len(path) > 3 {
		if path[3][0:1] != "@" {                          <--------HERE
			config.Channel = "#" + path[3]

Because path[3] in my case was empty. url.Parse red the path just until the '#' symbol.

Therefore, here are two possible remedies for this:
a) whether check at url.Parse() stage for escaped fragments (in pkg/router/router.go):

func (router *ServiceRouter) ExtractServiceName(rawURL string) (string, *url.URL, error) {
	serviceURL, err := url.Parse(rawURL)
	if serviceURL.EscapedFragment() != "" && strings.Contains(rawURL, "/#") {
		fmt.Println("Please, do not use \"#\" before channel name")
		serviceURL.Path += serviceURL.EscapedFragment()
	}
	if err != nil {
		return "", &url.URL{}, err
	}
	return serviceURL.Scheme, serviceURL, nil
}

b) or check for escaped fragments just in rocket chat's case (if somebody is worrying about introducing bugs affecting other services):
(in pkg/services/rocketchat_configure.go:)

if path[3] == "" && serviceURL.EscapedFragment() != "" {
  fmt.Println("Please, do not use \"#\" before channel name")
  path[3] = serviceURL.EscapedFragment()
}

Let me know what you think, thanks.

[piksel]

Yeah, since that is rocketchat specific, it should probably be handled inside the service (or rather, it's config parser), especially as this would prevent all other services from ever using the fragment part of the URLs.

I guess we should either explicitly allow the fragment to be used as the channel name, or throw an error when we detect it, not do both. But otherwise I totally agree, getting a segfault for using the wrong syntax is terrible feedback for the consumer!

[atighineanu]

solved by #74