From 852136a03c60c5ccb02890dfa95daf1262b0c405 Mon Sep 17 00:00:00 2001 From: Dmytro Shynkevych Date: Wed, 15 Jul 2020 18:05:08 -0400 Subject: [PATCH] cmd/tailscale: simplify hostname validation Signed-off-by: Dmytro Shynkevych --- cmd/tailscale/cli/up.go | 35 ++--------------------------------- 1 file changed, 2 insertions(+), 33 deletions(-) diff --git a/cmd/tailscale/cli/up.go b/cmd/tailscale/cli/up.go index 244d724b2..01161425c 100644 --- a/cmd/tailscale/cli/up.go +++ b/cmd/tailscale/cli/up.go @@ -80,37 +80,6 @@ var upArgs struct { hostname string } -// validateHostname checks that name is a valid domain name label -// pursuant to https://tools.ietf.org/html/rfc1034#section-3.1. -func validateHostname(name string) error { - switch { - // Empty string is treated as missing hostname and replaced downstream. - case len(name) == 0: - return nil - case len(name) > 63: - return fmt.Errorf("longer than 63 characters") - } - - name = strings.ToLower(name) - first, last := name[0], name[len(name)-1] - - // This is more obviously correct than using package unicode, - // though that can work too if we ensure that characters are below MaxASCII. - if !('a' <= first && first <= 'z') { - return fmt.Errorf("does not start with a letter") - } - if !(('a' <= last && last <= 'z') || ('0' <= last && last <= '9')) { - return fmt.Errorf("does not end with a letter or digit") - } - for i, c := range name { - if !(('a' <= c && c <= 'z') || ('0' <= c && c <= '9') || (c == '-')) { - return fmt.Errorf("[%d] = %c is not a letter, digit or hyphen", i, c) - } - } - - return nil -} - // parseIPOrCIDR parses an IP address or a CIDR prefix. If the input // is an IP address, it is returned in CIDR form with a /32 mask for // IPv4 or a /128 mask for IPv6. @@ -199,8 +168,8 @@ func runUp(ctx context.Context, args []string) error { } } - if err := validateHostname(upArgs.hostname); err != nil { - log.Fatalf("illegal hostname: %v", err) + if len(upArgs.hostname) > 256 { + log.Fatalf("hostname too long: %d bytes (max 256)", len(upArgs.hostname)) } // TODO(apenwarr): fix different semantics between prefs and uflags