istio.io/istio@v0.0.0-20240520182934-d79c90f27776/security/pkg/pki/util/dual_use.go (about)

     1  // Copyright Istio 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 util
    16  
    17  import (
    18  	"fmt"
    19  	"strings"
    20  )
    21  
    22  // DualUseCommonName extracts a valid CommonName from a comma-delimited host string
    23  // for dual-use certificates.
    24  func DualUseCommonName(host string) (string, error) {
    25  	// cn uses one hostname, drop the rest
    26  	first := strings.SplitN(host, ",", 2)[0]
    27  
    28  	// cn max length is 64 (ub-common-name @ https://tools.ietf.org/html/rfc5280)
    29  	if l := len(first); l > 64 {
    30  		return "", fmt.Errorf("certificate CN upper bound exceeded (%v>64): %s", l, first)
    31  	}
    32  
    33  	return first, nil
    34  }