github.com/google/martian/v3@v3.3.3/proxyauth/proxyauth.go (about)

     1  // Copyright 2015 Google Inc. All rights reserved.
     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 proxyauth provides authentication support via the
    16  // Proxy-Authorization header.
    17  package proxyauth
    18  
    19  import (
    20  	"encoding/base64"
    21  	"net/http"
    22  	"strings"
    23  
    24  	"github.com/google/martian/v3"
    25  	"github.com/google/martian/v3/auth"
    26  )
    27  
    28  var noop = martian.Noop("proxyauth.Modifier")
    29  
    30  // Modifier is the proxy authentication modifier.
    31  type Modifier struct {
    32  	reqmod martian.RequestModifier
    33  	resmod martian.ResponseModifier
    34  }
    35  
    36  // NewModifier returns a new proxy authentication modifier.
    37  func NewModifier() *Modifier {
    38  	return &Modifier{
    39  		reqmod: noop,
    40  		resmod: noop,
    41  	}
    42  }
    43  
    44  // SetRequestModifier sets the request modifier.
    45  func (m *Modifier) SetRequestModifier(reqmod martian.RequestModifier) {
    46  	if reqmod == nil {
    47  		reqmod = noop
    48  	}
    49  
    50  	m.reqmod = reqmod
    51  }
    52  
    53  // SetResponseModifier sets the response modifier.
    54  func (m *Modifier) SetResponseModifier(resmod martian.ResponseModifier) {
    55  	if resmod == nil {
    56  		resmod = noop
    57  	}
    58  
    59  	m.resmod = resmod
    60  }
    61  
    62  // ModifyRequest sets the auth ID in the context from the request iff it has
    63  // not already been set and runs reqmod.ModifyRequest. If the underlying
    64  // modifier has indicated via auth error that no valid auth credentials
    65  // have been found we set ctx.SkipRoundTrip.
    66  func (m *Modifier) ModifyRequest(req *http.Request) error {
    67  	ctx := martian.NewContext(req)
    68  	actx := auth.FromContext(ctx)
    69  
    70  	actx.SetID(id(req.Header))
    71  
    72  	err := m.reqmod.ModifyRequest(req)
    73  
    74  	if actx.Error() != nil {
    75  		ctx.SkipRoundTrip()
    76  	}
    77  
    78  	return err
    79  }
    80  
    81  // ModifyResponse runs resmod.ModifyResponse and modifies the response to
    82  // include the correct status code and headers if auth error is present.
    83  //
    84  // If an error is returned from resmod.ModifyResponse it is returned.
    85  func (m *Modifier) ModifyResponse(res *http.Response) error {
    86  	ctx := martian.NewContext(res.Request)
    87  	actx := auth.FromContext(ctx)
    88  
    89  	err := m.resmod.ModifyResponse(res)
    90  
    91  	if actx.Error() != nil {
    92  		res.StatusCode = http.StatusProxyAuthRequired
    93  		res.Header.Set("Proxy-Authenticate", "Basic")
    94  	}
    95  
    96  	return err
    97  }
    98  
    99  // id returns an ID derived from the Proxy-Authorization header username and password.
   100  func id(header http.Header) string {
   101  	id := strings.TrimPrefix(header.Get("Proxy-Authorization"), "Basic ")
   102  
   103  	data, err := base64.StdEncoding.DecodeString(id)
   104  	if err != nil {
   105  		return ""
   106  	}
   107  
   108  	return string(data)
   109  }