go.chromium.org/luci@v0.0.0-20240309015107-7cdc2e660f33/server/auth/addr.go (about)

     1  // Copyright 2015 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 auth
    16  
    17  import (
    18  	"errors"
    19  	"fmt"
    20  	"net"
    21  	"strings"
    22  )
    23  
    24  // parseRemoteIP parses the IP address from the supplied HTTP request RemoteAddr
    25  // string.
    26  //
    27  // The HTTP library's representation of remote address says that it is a
    28  // "host:port" pair. They lie. The following permutations have been observed:
    29  // - ipv4:port (Standard)
    30  // - ipv4 (GAE)
    31  // - ipv6 (GAE)
    32  // - [ipv6]:port (GAE Managed VM)
    33  //
    34  // Note that IPv6 addresses have colons in them.
    35  //
    36  // If the remote address is blank, "0.0.0.0" will be returned.
    37  func parseRemoteIP(a string) (net.IP, error) {
    38  	if a == "" {
    39  		return net.IPv4(0, 0, 0, 0), nil
    40  	}
    41  
    42  	// IPv6 in braces with or without port.
    43  	if strings.HasPrefix(a, "[") {
    44  		idx := strings.LastIndex(a, "]")
    45  		if idx < 0 {
    46  			return nil, errors.New("missing closing brace on IPv6 address")
    47  		}
    48  		a = a[1:idx]
    49  	}
    50  
    51  	// Parse as a standalone IPv4/IPv6 address (no port).
    52  	if ip := net.ParseIP(a); ip != nil {
    53  		return ip, nil
    54  	}
    55  
    56  	// Is there a port? Strip and try again.
    57  	if idx := strings.LastIndex(a, ":"); idx >= 0 {
    58  		if ip := net.ParseIP(a[:idx]); ip != nil {
    59  			return ip, nil
    60  		}
    61  	}
    62  
    63  	return nil, fmt.Errorf("don't know how to parse: %q", a)
    64  }