protocol: add ParseRequest and ParseResponse functions

For parsing and verification of of HTTP request and response bodies,
including optional checking the Content-Type field which the handler
previously didn't do.

omaha/handler.go

@@ -33,25 +33,18 @@ func (o *OmahaHandler) ServeHTTP(w http.ResponseWriter, httpReq *http.Request) {
 
 	// A request over 1M in size is certainly bogus.
 	reader := http.MaxBytesReader(w, httpReq.Body, 1024*1024)
-
-	decoder := xml.NewDecoder(reader)
-	var omahaReq Request
-	if err := decoder.Decode(&omahaReq); err != nil {
-		log.Printf("omaha: Failed decoding XML: %v", err)
-		http.Error(w, "Invalid XML", http.StatusBadRequest)
-		return
-	}
-
-	if omahaReq.Protocol != "3.0" {
-		log.Printf("omaha: Unexpected protocol: %q", omahaReq.Protocol)
-		http.Error(w, "Omaha 3.0 Required", http.StatusBadRequest)
+	contentType := httpReq.Header.Get("Content-Type")
+	omahaReq, err := ParseRequest(contentType, reader)
+	if err != nil {
+		log.Printf("omaha: Failed parsing request: %v", err)
+		http.Error(w, "Bad Omaha Request", http.StatusBadRequest)
 		return
 	}
 
 	httpStatus := 0
 	omahaResp := NewResponse()
 	for _, appReq := range omahaReq.Apps {
-		appResp := o.serveApp(omahaResp, httpReq, &omahaReq, appReq)
+		appResp := o.serveApp(omahaResp, httpReq, omahaReq, appReq)
 		if appResp.Status == AppOK {
 			// HTTP is ok if any app is ok.
 			httpStatus = http.StatusOK

omaha/parse.go

@@ -0,0 +1,71 @@
+// Copyright 2017 CoreOS, Inc.
+//
+// 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 omaha
+
+import (
+	"encoding/xml"
+	"fmt"
+	"io"
+	"mime"
+	"strings"
+)
+
+// checkContentType verifies the HTTP Content-Type header properly
+// declares the document is XML and UTF-8. Blank is assumed OK.
+func checkContentType(contentType string) error {
+	if contentType == "" {
+		return nil
+	}
+
+	mType, mParams, err := mime.ParseMediaType(contentType)
+	if err != nil {
+		return err
+	}
+
+	if mType != "text/xml" && mType != "application/xml" {
+		return fmt.Errorf("unsupported content type %q", mType)
+	}
+
+	charset, _ := mParams["charset"]
+	if charset != "" && strings.ToLower(charset) != "utf-8" {
+		return fmt.Errorf("unsupported content charset %q", charset)
+	}
+
+	return nil
+}
+
+// parseReqOrResp parses Request and Response objects.
+func parseReqOrResp(r io.Reader, v interface{}) error {
+	decoder := xml.NewDecoder(r)
+	if err := decoder.Decode(v); err != nil {
+		return err
+	}
+
+	var protocol string
+	switch v := v.(type) {
+	case *Request:
+		protocol = v.Protocol
+	case *Response:
+		protocol = v.Protocol
+	default:
+		panic(fmt.Errorf("unexpected type %T", v))
+	}
+
+	if protocol != "3.0" {
+		return fmt.Errorf("unsupported omaha protocol: %q", protocol)
+	}
+
+	return nil
+}

omaha/parse_test.go

@@ -0,0 +1,55 @@
+// Copyright 2017 CoreOS, Inc.
+//
+// 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 omaha
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestCheckContentType(t *testing.T) {
+	for _, tt := range []struct {
+		ct string
+		ok bool
+	}{
+		{"", true},
+		{"text/xml", true},
+		{"text/XML", true},
+		{"application/xml", true},
+		{"text/plain", false},
+		{"xml", false},
+		{"text/xml; charset=utf-8", true},
+		{"text/xml; charset=UTF-8", true},
+		{"text/xml; charset=ascii", false},
+	} {
+		err := checkContentType(tt.ct)
+		if tt.ok && err != nil {
+			t.Errorf("%q failed: %v", tt.ct, err)
+		}
+		if !tt.ok && err == nil {
+			t.Errorf("%q was not rejected", tt.ct)
+		}
+	}
+}
+
+func TestParseBadVersion(t *testing.T) {
+	r := strings.NewReader(`<request protocol="2.0"></request>`)
+	err := parseReqOrResp(r, &Request{})
+	if err == nil {
+		t.Error("Bad protocol version was accepted")
+	} else if err.Error() != `unsupported omaha protocol: "2.0"` {
+		t.Errorf("Wrong error: %v", err)
+	}
+}

omaha/protocol.go

@@ -24,6 +24,7 @@ package omaha
 
 import (
 	"encoding/xml"
+	"io"
 )
 
 // Request sent by the Omaha client
@@ -56,6 +57,22 @@ func NewRequest() *Request {
 	}
 }
 
+// ParseRequest verifies and returns the parsed Request document.
+// The MIME Content-Type header may be provided to sanity check its
+// value; if blank it is assumed to be XML in UTF-8.
+func ParseRequest(contentType string, body io.Reader) (*Request, error) {
+	if err := checkContentType(contentType); err != nil {
+		return nil, err
+	}
+
+	r := &Request{}
+	if err := parseReqOrResp(body, r); err != nil {
+		return nil, err
+	}
+
+	return r, nil
+}
+
 func (r *Request) AddApp(id, version string) *AppRequest {
 	a := &AppRequest{ID: id, Version: version}
 	r.Apps = append(r.Apps, a)
@@ -138,6 +155,22 @@ func NewResponse() *Response {
 	}
 }
 
+// ParseResponse verifies and returns the parsed Response document.
+// The MIME Content-Type header may be provided to sanity check its
+// value; if blank it is assumed to be XML in UTF-8.
+func ParseResponse(contentType string, body io.Reader) (*Response, error) {
+	if err := checkContentType(contentType); err != nil {
+		return nil, err
+	}
+
+	r := &Response{}
+	if err := parseReqOrResp(body, r); err != nil {
+		return nil, err
+	}
+
+	return r, nil
+}
+
 type DayStart struct {
 	ElapsedSeconds string `xml:"elapsed_seconds,attr"`
 }

omaha/protocol_test.go

@@ -17,10 +17,13 @@ package omaha
 import (
 	"encoding/xml"
 	"fmt"
+	"reflect"
+	"strings"
 	"testing"
 )
 
-const SampleRequest = `<?xml version="1.0" encoding="UTF-8"?>
+const (
+	sampleRequest = `<?xml version="1.0" encoding="UTF-8"?>
 <request protocol="3.0" version="ChromeOSUpdateEngine-0.1.0.0" updaterversion="ChromeOSUpdateEngine-0.1.0.0" installsource="ondemandupdate" ismachine="1">
 <os version="Indy" platform="Chrome OS" sp="ForcedUpdate_x86_64"></os>
 <app appid="{87efface-864d-49a5-9bb3-4b050a7c227a}" bootid="{7D52A1CC-7066-40F0-91C7-7CB6A871BFDE}" machineid="{8BDE4C4D-9083-4D61-B41C-3253212C0C37}" oem="ec3000" version="ForcedUpdate" track="dev-channel" from_track="developer-build" lang="en-US" board="amd64-generic" hardware_class="" delta_okay="false" >
@@ -30,10 +33,34 @@ const SampleRequest = `<?xml version="1.0" encoding="UTF-8"?>
 </app>
 </request>
 `
+	sampleResponse = `<?xml version="1.0" encoding="UTF-8"?>
+<response protocol="3.0">
+<daystart elapsed_seconds="49008"/>
+<app appid="{87efface-864d-49a5-9bb3-4b050a7c227a}" status="ok">
+<ping status="ok"/>
+<updatecheck status="ok">
+<urls>
+<url codebase="http://kam:8080/static/"/>
+</urls>
+<manifest version="9999.0.0">
+<packages>
+<package hash="+LXvjiaPkeYDLHoNKlf9qbJwvnk=" name="update.gz" size="67546213" required="true"/>
+</packages>
+<actions>
+<action event="postinstall" DisplayVersion="9999.0.0" sha256="0VAlQW3RE99SGtSB5R4m08antAHO8XDoBMKDyxQT/Mg=" needsadmin="false" IsDeltaPayload="true" />
+</actions>
+</manifest>
+</updatecheck>
+</app>
+</response>
+`
+)
 
 func TestOmahaRequestUpdateCheck(t *testing.T) {
-	v := Request{}
-	xml.Unmarshal([]byte(SampleRequest), &v)
+	v, err := ParseRequest("", strings.NewReader(sampleRequest))
+	if err != nil {
+		t.Fatalf("ParseRequest failed: %v", err)
+	}
 
 	if v.OS.Version != "Indy" {
 		t.Error("Unexpected version", v.OS.Version)
@@ -80,6 +107,63 @@ func TestOmahaRequestUpdateCheck(t *testing.T) {
 	}
 }
 
+func TestOmahaResponseWithUpdate(t *testing.T) {
+	parsed, err := ParseResponse("", strings.NewReader(sampleResponse))
+	if err != nil {
+		t.Fatalf("ParseResponse failed: %v", err)
+	}
+
+	expected := &Response{
+		XMLName:  xml.Name{Local: "response"},
+		Protocol: "3.0",
+		DayStart: DayStart{ElapsedSeconds: "49008"},
+		Apps: []*AppResponse{&AppResponse{
+			ID:     "{87efface-864d-49a5-9bb3-4b050a7c227a}",
+			Status: AppOK,
+			Ping:   &PingResponse{"ok"},
+			UpdateCheck: &UpdateResponse{
+				Status: UpdateOK,
+				URLs: []*URL{&URL{
+					CodeBase: "http://kam:8080/static/",
+				}},
+				Manifest: &Manifest{
+					Version: "9999.0.0",
+					Packages: []*Package{&Package{
+						SHA1:     "+LXvjiaPkeYDLHoNKlf9qbJwvnk=",
+						Name:     "update.gz",
+						Size:     67546213,
+						Required: true,
+					}},
+					Actions: []*Action{&Action{
+						Event:          "postinstall",
+						DisplayVersion: "9999.0.0",
+						SHA256:         "0VAlQW3RE99SGtSB5R4m08antAHO8XDoBMKDyxQT/Mg=",
+						IsDeltaPayload: true,
+					}},
+				},
+			},
+		}},
+	}
+
+	if !reflect.DeepEqual(parsed, expected) {
+		t.Errorf("parsed != expected\n%s\n%s", parsed, expected)
+	}
+}
+
+func TestOmahaResponsAsRequest(t *testing.T) {
+	_, err := ParseRequest("", strings.NewReader(sampleResponse))
+	if err == nil {
+		t.Fatal("ParseRequest successfully parsed a response")
+	}
+}
+
+func TestOmahaRequestAsResponse(t *testing.T) {
+	_, err := ParseResponse("", strings.NewReader(sampleRequest))
+	if err == nil {
+		t.Fatal("ParseResponse successfully parsed a request")
+	}
+}
+
 func ExampleNewResponse() {
 	response := NewResponse()
 	app := response.AddApp("{52F1B9BC-D31A-4D86-9276-CBC256AADF9A}", "ok")