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

     1  // Copyright 2016 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  	"context"
    19  	"net/http"
    20  )
    21  
    22  // NewModifyingTransport returns a transport that can modify headers of
    23  // http.Request's that pass through it (e.g. by appending authentication
    24  // information).
    25  //
    26  // Go docs explicitly prohibit this kind of behavior, but everyone cheat and
    27  // implement it anyway. E.g. https://github.com/golang/oauth2.
    28  //
    29  // Works only with Go >=1.5 transports (that use Request.Cancel instead of
    30  // deprecated Transport.CancelRequest). For same reason doesn't implement
    31  // CancelRequest itself.
    32  //
    33  // TODO(vadimsh): Move it elsewhere. It has no direct relation to auth.
    34  func NewModifyingTransport(base http.RoundTripper, modifier func(*http.Request) error) http.RoundTripper {
    35  	return &modifyingTransport{
    36  		base:     base,
    37  		modifier: modifier,
    38  	}
    39  }
    40  
    41  type modifyingTransport struct {
    42  	base     http.RoundTripper
    43  	modifier func(*http.Request) error
    44  }
    45  
    46  func (t *modifyingTransport) RoundTrip(req *http.Request) (*http.Response, error) {
    47  	clone := *req
    48  	clone.Header = make(http.Header, len(req.Header))
    49  	for k, v := range req.Header {
    50  		clone.Header[k] = v
    51  	}
    52  	if err := t.modifier(&clone); err != nil {
    53  		return nil, err
    54  	}
    55  	return t.base.RoundTrip(&clone)
    56  }
    57  
    58  var globalInstrumentTransport func(context.Context, http.RoundTripper, string) http.RoundTripper
    59  
    60  // SetMonitoringInstrumentation sets a global callback used by Authenticator to
    61  // add monitoring instrumentation to a transport.
    62  //
    63  // This is used by tsmon library in init(). We have to resort to callbacks to
    64  // break module dependency cycle (tsmon is using auth lib already).
    65  func SetMonitoringInstrumentation(cb func(context.Context, http.RoundTripper, string) http.RoundTripper) {
    66  	globalInstrumentTransport = cb
    67  }