github.com/google/martian/v3@v3.3.3/header/framing_modifier.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 header 16 17 import ( 18 "fmt" 19 "net/http" 20 "strings" 21 22 "github.com/google/martian/v3" 23 ) 24 25 // NewBadFramingModifier makes a best effort to fix inconsistencies in the 26 // request such as multiple Content-Lengths or the lack of Content-Length and 27 // improper Transfer-Encoding. If it is unable to determine a proper resolution 28 // it returns an error. 29 // 30 // http://tools.ietf.org/html/draft-ietf-httpbis-p1-messaging-14#section-3.3 31 func NewBadFramingModifier() martian.RequestModifier { 32 return martian.RequestModifierFunc( 33 func(req *http.Request) error { 34 cls := req.Header["Content-Length"] 35 if len(cls) > 0 { 36 var length string 37 38 // Iterate over all Content-Length headers, splitting any we find with 39 // commas, and check that all Content-Lengths are equal. 40 for _, ls := range cls { 41 for _, l := range strings.Split(ls, ",") { 42 // First length, set it as the canonical Content-Length. 43 if length == "" { 44 length = strings.TrimSpace(l) 45 continue 46 } 47 48 // Mismatched Content-Lengths. 49 if length != strings.TrimSpace(l) { 50 return fmt.Errorf(`bad request framing: multiple mismatched "Content-Length" headers: %v`, cls) 51 } 52 } 53 } 54 55 // All Content-Lengths are equal, remove extras and set it to the 56 // canonical value. 57 req.Header.Set("Content-Length", length) 58 } 59 60 tes := req.Header["Transfer-Encoding"] 61 if len(tes) > 0 { 62 // Extract the last Transfer-Encoding value, and split on commas. 63 last := strings.Split(tes[len(tes)-1], ",") 64 65 // Check that the last, potentially comma-delimited, value is 66 // "chunked", else we have no way to determine when the request is 67 // finished. 68 if strings.TrimSpace(last[len(last)-1]) != "chunked" { 69 return fmt.Errorf(`bad request framing: "Transfer-Encoding" header is present, but does not end in "chunked"`) 70 } 71 72 // Transfer-Encoding "chunked" takes precedence over 73 // Content-Length. 74 req.Header.Del("Content-Length") 75 } 76 77 return nil 78 }) 79 }