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// Copyright (c) 2022 Tulir Asokan
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.
package whatsmeow
import (
"crypto/aes"
"crypto/cipher"
"crypto/rand"
"fmt"
"time"
"google.golang.org/protobuf/proto"
waBinary "go.mau.fi/whatsmeow/binary"
waProto "go.mau.fi/whatsmeow/binary/proto"
"go.mau.fi/whatsmeow/types"
"go.mau.fi/whatsmeow/types/events"
"go.mau.fi/whatsmeow/util/hkdfutil"
)
func getMediaRetryKey(mediaKey []byte) (cipherKey []byte) {
return hkdfutil.SHA256(mediaKey, nil, []byte("WhatsApp Media Retry Notification"), 32)
}
func prepareMediaRetryGCM(mediaKey []byte) (cipher.AEAD, error) {
block, err := aes.NewCipher(getMediaRetryKey(mediaKey))
if err != nil {
return nil, fmt.Errorf("failed to initialize AES cipher: %w", err)
}
gcm, err := cipher.NewGCM(block)
if err != nil {
return nil, fmt.Errorf("failed to initialize GCM: %w", err)
}
return gcm, nil
}
func encryptMediaRetryReceipt(messageID types.MessageID, mediaKey []byte) (ciphertext, iv []byte, err error) {
receipt := &waProto.ServerErrorReceipt{
StanzaId: proto.String(messageID),
}
var plaintext []byte
plaintext, err = proto.Marshal(receipt)
if err != nil {
err = fmt.Errorf("failed to marshal payload: %w", err)
return
}
var gcm cipher.AEAD
gcm, err = prepareMediaRetryGCM(mediaKey)
if err != nil {
return
}
iv = make([]byte, 12)
_, err = rand.Read(iv)
if err != nil {
panic(err)
}
ciphertext = gcm.Seal(plaintext[:0], iv, plaintext, []byte(messageID))
return
}
// SendMediaRetryReceipt sends a request to the phone to re-upload the media in a message.
//
// The response will come as an *events.MediaRetry. The response will then have to be decrypted
// using DecryptMediaRetryNotification and the same media key passed here.
func (cli *Client) SendMediaRetryReceipt(message *types.MessageInfo, mediaKey []byte) error {
ciphertext, iv, err := encryptMediaRetryReceipt(message.ID, mediaKey)
if err != nil {
return fmt.Errorf("failed to prepare encrypted retry receipt: %w", err)
}
rmrAttrs := waBinary.Attrs{
"jid": message.Chat,
"from_me": message.IsFromMe,
}
if message.IsGroup {
rmrAttrs["participant"] = message.Sender
}
encryptedRequest := []waBinary.Node{
{Tag: "enc_p", Content: ciphertext},
{Tag: "enc_iv", Content: iv},
}
err = cli.sendNode(waBinary.Node{
Tag: "receipt",
Attrs: waBinary.Attrs{
"id": message.ID,
"to": cli.Store.ID.ToNonAD(),
"type": "server-error",
},
Content: []waBinary.Node{
{Tag: "encrypt", Content: encryptedRequest},
{Tag: "rmr", Attrs: rmrAttrs},
},
})
if err != nil {
return err
}
return nil
}
// DecryptMediaRetryNotification decrypts a media retry notification using the media key.
func DecryptMediaRetryNotification(evt *events.MediaRetry, mediaKey []byte) (*waProto.MediaRetryNotification, error) {
gcm, err := prepareMediaRetryGCM(mediaKey)
if err != nil {
return nil, err
}
plaintext, err := gcm.Open(nil, evt.IV, evt.Ciphertext, []byte(evt.MessageID))
if err != nil {
return nil, fmt.Errorf("failed to decrypt notification: %w", err)
}
var notif waProto.MediaRetryNotification
err = proto.Unmarshal(plaintext, ¬if)
if err != nil {
return nil, fmt.Errorf("failed to unmarshal notification (invalid encryption key?): %w", err)
}
return ¬if, nil
}
func parseMediaRetryNotification(node *waBinary.Node) (*events.MediaRetry, error) {
ag := node.AttrGetter()
var evt events.MediaRetry
evt.Timestamp = time.Unix(ag.Int64("t"), 0)
evt.MessageID = types.MessageID(ag.String("id"))
if !ag.OK() {
return nil, ag.Error()
}
rmr, ok := node.GetOptionalChildByTag("rmr")
if !ok {
return nil, &ElementMissingError{Tag: "rmr", In: "retry notification"}
}
rmrAG := rmr.AttrGetter()
evt.ChatID = rmrAG.JID("jid")
evt.FromMe = rmrAG.Bool("from_me")
evt.SenderID = rmrAG.OptionalJIDOrEmpty("participant")
if !rmrAG.OK() {
return nil, fmt.Errorf("missing attributes in <rmr> tag: %w", rmrAG.Error())
}
evt.Ciphertext, ok = node.GetChildByTag("encrypt", "enc_p").Content.([]byte)
if !ok {
return nil, &ElementMissingError{Tag: "enc_p", In: fmt.Sprintf("retry notification %s", evt.MessageID)}
}
evt.IV, ok = node.GetChildByTag("encrypt", "enc_iv").Content.([]byte)
if !ok {
return nil, &ElementMissingError{Tag: "enc_iv", In: fmt.Sprintf("retry notification %s", evt.MessageID)}
}
return &evt, nil
}
func (cli *Client) handleMediaRetryNotification(node *waBinary.Node) {
// TODO handle errors (e.g. <error code="2"/>)
evt, err := parseMediaRetryNotification(node)
if err != nil {
cli.Log.Warnf("Failed to parse media retry notification: %v", err)
return
}
cli.dispatchEvent(evt)
}
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