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ergo/vendor/github.com/ergochat/irc-go/ircutils/hostnames.go
2021-06-18 02:43:25 -04:00

42 lines
1.3 KiB
Go

// written by Daniel Oaks <daniel@danieloaks.net>
// released under the ISC license
package ircutils
import "strings"
var allowedHostnameChars = "abcdefghijklmnopqrstuvwxyz1234567890-."
// HostnameIsValid provides a way for servers to check whether a looked-up client
// hostname is valid (see InspIRCd #1033 for why this is required).
//
// This function shouldn't be called by clients since they don't need to validate
// hostnames for IRC use, just by servers that need to confirm hostnames of incoming
// clients.
//
// In addition to this function, servers should impose their own limits on max
// hostname length -- this function limits it to 200 but most servers will probably
// want to make it smaller than that.
func HostnameIsValid(hostname string) bool {
// IRC hostnames specifically require a period, rough limit of 200 chars
if !strings.Contains(hostname, ".") || len(hostname) < 1 || len(hostname) > 200 {
return false
}
// ensure each part of hostname is valid
for _, part := range strings.Split(hostname, ".") {
if len(part) < 1 || len(part) > 63 || strings.HasPrefix(part, "-") || strings.HasSuffix(part, "-") {
return false
}
}
// ensure all chars of hostname are valid
for _, char := range strings.Split(strings.ToLower(hostname), "") {
if !strings.Contains(allowedHostnameChars, char) {
return false
}
}
return true
}