Add hash checking and fix hexadecimal chardata

cmd/fdroidcl/install.go

@@ -32,7 +32,7 @@ func runInstall(args []string) {
 		apk := app.CurApk
 		url := fmt.Sprintf("%s/%s", repoURL, apk.ApkName)
 		path := filepath.Join(apksDir, apk.ApkName)
-		if err := downloadEtag(url, path); err != nil {
+		if err := downloadEtag(url, path, apk.Hash.Data); err != nil {
 			log.Fatalf("Could not download '%s': %v", app.ID, err)
 		}
 		paths[i] = path

cmd/fdroidcl/update.go

@@ -4,6 +4,9 @@
 package main
 
 import (
+	"bytes"
+	"crypto/sha256"
+	"errors"
 	"fmt"
 	"io"
 	"io/ioutil"
@@ -33,7 +36,7 @@ func runUpdate(args []string) {
 
 func updateIndex() error {
 	url := fmt.Sprintf("%s/%s", repoURL, "index.jar")
-	if err := downloadEtag(url, indexPath(repoName)); err != nil {
+	if err := downloadEtag(url, indexPath(repoName), nil); err != nil {
 		return err
 	}
 	return nil
@@ -47,8 +50,9 @@ func respEtag(resp *http.Response) string {
 	return etags[0]
 }
 
-func downloadEtag(url, path string) error {
+func downloadEtag(url, path string, sum []byte) error {
 	fmt.Printf("Downloading %s...", url)
+	defer fmt.Println()
 	client := &http.Client{}
 	req, err := http.NewRequest("GET", url, nil)
 
@@ -64,22 +68,35 @@ func downloadEtag(url, path string) error {
 	}
 	defer resp.Body.Close()
 	if resp.StatusCode == http.StatusNotModified {
-		fmt.Println(" not modified")
+		fmt.Printf(" not modified")
 		return nil
 	}
 	f, err := os.OpenFile(path, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0644)
 	if err != nil {
 		return err
 	}
-	_, err = io.Copy(f, resp.Body)
-	err2 := ioutil.WriteFile(etagPath, []byte(respEtag(resp)), 0644)
-	if err != nil {
-		return err
+	if sum == nil {
+		_, err := io.Copy(f, resp.Body)
+		if err != nil {
+			return err
+		}
+	} else {
+		data, err := ioutil.ReadAll(resp.Body)
+		if err != nil {
+			return err
+		}
+		got := sha256.Sum256(data)
+		if !bytes.Equal(sum, got[:]) {
+			return errors.New("sha256 mismatch")
+		}
+		if _, err := f.Write(data); err != nil {
+			return err
+		}
 	}
-	if err2 != nil {
-		return err2
+	if err := ioutil.WriteFile(etagPath, []byte(respEtag(resp)), 0644); err != nil {
+		return err
 	}
-	fmt.Println(" done")
+	fmt.Printf(" done")
 	return nil
 }
 

index.go

@@ -39,14 +39,29 @@ func (cl *commaList) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error
 
 type hexVal []byte
 
-func (hv *hexVal) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {
+func (hv *hexVal) UnmarshalXML(d *xml.Decoder, start xml.StartElement) (err error) {
 	var content string
-	var err error
 	if err = d.DecodeElement(&content, &start); err != nil {
-		return err
+		return
 	}
 	*hv, err = hex.DecodeString(content)
-	return err
+	return
+}
+
+func (hv *hexVal) UnmarshalText(text []byte) (err error) {
+	*hv, err = hex.DecodeString(string(text))
+	return
+}
+
+func (hv *hexVal) MarshalXML(e *xml.Encoder, start xml.StartElement) error {
+	s := hex.EncodeToString(*hv)
+	e.EncodeElement(s, start)
+	return nil
+}
+
+func (hv *hexVal) MarshalText() (result []byte, err error) {
+	s := hex.EncodeToString(*hv)
+	return []byte(s), nil
 }
 
 // App is an Android application
@@ -72,7 +87,7 @@ type App struct {
 	CurApk    *Apk
 }
 
-type Hash struct {
+type HexHash struct {
 	Type string `xml:"type,attr"`
 	Data hexVal `xml:",chardata"`
 }
@@ -105,7 +120,7 @@ type Apk struct {
 	Added   dateVal   `xml:"added"`
 	Perms   commaList `xml:"permissions"`
 	Feats   commaList `xml:"features"`
-	Hashes  []Hash    `xml:"hash"`
+	Hash    HexHash   `xml:"hash"`
 }
 
 func (app *App) calcCurApk() {