Bump google.golang.org/api

vendor/github.com/google/martian/header/via_modifier.go

@@ -0,0 +1,125 @@
+// Copyright 2015 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package header
+
+import (
+	"crypto/rand"
+	"fmt"
+	"io"
+	"net/http"
+	"regexp"
+	"strings"
+
+	"github.com/google/martian"
+)
+
+const viaLoopKey = "via.LoopDetection"
+
+var whitespace = regexp.MustCompile("[\t ]+")
+
+// ViaModifier is a header modifier that checks for proxy redirect loops.
+type ViaModifier struct {
+	requestedBy string
+	boundary    string
+}
+
+// NewViaModifier returns a new Via modifier.
+func NewViaModifier(requestedBy string) *ViaModifier {
+	return &ViaModifier{
+		requestedBy: requestedBy,
+		boundary:    randomBoundary(),
+	}
+}
+
+// ModifyRequest sets the Via header and provides loop-detection. If Via is
+// already present, it will be appended to the existing value. If a loop is
+// detected an error is added to the context and the request round trip is
+// skipped.
+//
+// http://tools.ietf.org/html/draft-ietf-httpbis-p1-messaging-14#section-9.9
+func (m *ViaModifier) ModifyRequest(req *http.Request) error {
+	via := fmt.Sprintf("%d.%d %s-%s", req.ProtoMajor, req.ProtoMinor, m.requestedBy, m.boundary)
+
+	if v := req.Header.Get("Via"); v != "" {
+		if m.hasLoop(v) {
+			err := fmt.Errorf("via: detected request loop, header contains %s", via)
+
+			ctx := martian.NewContext(req)
+			ctx.Set(viaLoopKey, err)
+			ctx.SkipRoundTrip()
+
+			return err
+		}
+
+		via = fmt.Sprintf("%s, %s", v, via)
+	}
+
+	req.Header.Set("Via", via)
+
+	return nil
+}
+
+// ModifyResponse sets the status code to 400 Bad Request if a loop was
+// detected in the request.
+func (m *ViaModifier) ModifyResponse(res *http.Response) error {
+	ctx := martian.NewContext(res.Request)
+
+	if err, _ := ctx.Get(viaLoopKey); err != nil {
+		res.StatusCode = 400
+		res.Status = http.StatusText(400)
+
+		return err.(error)
+	}
+
+	return nil
+}
+
+// hasLoop parses via and attempts to match requestedBy against the contained
+// pseudonyms/host:port pairs.
+func (m *ViaModifier) hasLoop(via string) bool {
+	for _, v := range strings.Split(via, ",") {
+		parts := whitespace.Split(strings.TrimSpace(v), 3)
+
+		// No pseudonym or host:port, assume there is no loop.
+		if len(parts) < 2 {
+			continue
+		}
+
+		if fmt.Sprintf("%s-%s", m.requestedBy, m.boundary) == parts[1] {
+			return true
+		}
+	}
+
+	return false
+}
+
+// SetBoundary sets the boundary string (random 10 character by default) used to
+// disabiguate Martians that are chained together with identical requestedBy values.
+// This should only be used for testing.
+func (m *ViaModifier) SetBoundary(boundary string) {
+	m.boundary = boundary
+}
+
+// randomBoundary generates a 10 character string to ensure that Martians that
+// are chained together with the same requestedBy value do not collide.  This func
+// panics if io.Readfull fails.
+func randomBoundary() string {
+	var buf [10]byte
+	_, err := io.ReadFull(rand.Reader, buf[:])
+	if err != nil {
+		panic(err)
+	}
+	return fmt.Sprintf("%x", buf[:])
+}