Ox: Improve stability of decrypting.

Accept all allowed time stamps and remove invalid xml chars from
decrypted messages.

ox.go

@@ -9,6 +9,7 @@ import (
 	"errors"
 	"log"
 	"os"
+	"regexp"
 	"runtime"
 	"strings"
 	"time"
@@ -46,8 +47,12 @@ func oxDecrypt(m xmpp.Chat, client *xmpp.Client, user string,
 	if err != nil {
 		return "error", time.Now(), err
 	}
+	// Remove invalid code points.
+	message := strings.ToValidUTF8(string(decryptMsg.Data), "")
+	reg := regexp.MustCompile(`[\x{0000}-\x{0008}\x{000B}\x{000C}\x{000E}-\x{001F}]`)
+	message = reg.ReplaceAllString(message, "")
 	doc := etree.NewDocument()
-	err = doc.ReadFromBytes(decryptMsg.Data)
+	err = doc.ReadFromString(message)
 	if err != nil {
 		return "error", time.Now(), err
 	}
@@ -76,7 +81,10 @@ func oxDecrypt(m xmpp.Chat, client *xmpp.Client, user string,
 	}
 	msgStamp, err := time.Parse("2006-01-02T15:04:05Z", stamp.Value)
 	if err != nil {
-		return "error", time.Now(), err
+		msgStamp, err = time.Parse("2006-01-02T15:04:05Z0700", stamp.Value)
+		if err != nil {
+			return "error", time.Now(), err
+		}
 	}
 	payload := signcrypt.SelectElement("payload")
 	if payload == nil {