go.chromium.org/luci@v0.0.0-20240309015107-7cdc2e660f33/config/validation/net_util.go (about)

     1  // Copyright 2017 The LUCI Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //      http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package validation
    16  
    17  import (
    18  	"fmt"
    19  	"regexp"
    20  	"strings"
    21  )
    22  
    23  const hostnameSegmentPattern = "[a-z0-9]([a-z0-9-]*[a-z0-9])*"
    24  
    25  var hostnameRegexp = regexp.MustCompile(fmt.Sprintf(
    26  	"^%s([.]%s)*$",
    27  	hostnameSegmentPattern,
    28  	hostnameSegmentPattern,
    29  ))
    30  
    31  // ValidateHostname returns an error if the given string is not a valid
    32  // RFC1123 hostname.
    33  func ValidateHostname(hostname string) error {
    34  	if len(hostname) > 255 {
    35  		return fmt.Errorf("length exceeds 255 bytes")
    36  	}
    37  	if !hostnameRegexp.MatchString(hostname) {
    38  		return fmt.Errorf("hostname does not match regex %q", hostnameRegexp)
    39  	}
    40  	for _, s := range strings.Split(hostname, ".") {
    41  		if len(s) > 63 {
    42  			return fmt.Errorf("segment %q exceeds 63 bytes", s)
    43  		}
    44  	}
    45  	return nil
    46  }