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Support thumbnail export & import during backup of visual attachments

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trevor-signal 2024-07-16 16:39:56 -04:00 • committed by GitHub
parent 451ee56c92
commit 61548061b8
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GPG key ID: B5690EEEBB952194
30 changed files with 1326 additions and 327 deletions
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41
ts/Crypto.ts
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@ -221,7 +221,9 @@ const BACKUP_MATERIAL_INFO = '20231003_Signal_Backups_EncryptMessageBackup';
const BACKUP_MEDIA_ID_INFO = '20231003_Signal_Backups_Media_ID';
const BACKUP_MEDIA_ID_LEN = 15;
const BACKUP_MEDIA_ENCRYPT_INFO = '20231003_Signal_Backups_Media_ID';
const BACKUP_MEDIA_ENCRYPT_INFO = '20231003_Signal_Backups_EncryptMedia';
const BACKUP_MEDIA_THUMBNAIL_ENCRYPT_INFO =
'20240513_Signal_Backups_EncryptThumbnail';
const BACKUP_MEDIA_AES_KEY_LEN = 32;
const BACKUP_MEDIA_MAC_KEY_LEN = 32;
const BACKUP_MEDIA_IV_LEN = 16;
@ -278,11 +280,11 @@ export function deriveBackupMediaKeyMaterial(
mediaId: Uint8Array
): BackupMediaKeyMaterialType {
if (backupKey.byteLength !== BACKUP_KEY_LEN) {
throw new Error('deriveMediaIdFromMediaName: invalid backup key length');
throw new Error('deriveBackupMediaKeyMaterial: invalid backup key length');
}
if (!mediaId.length) {
throw new Error('deriveMediaIdFromMediaName: mediaId missing');
throw new Error('deriveBackupMediaKeyMaterial: mediaId missing');
}
const hkdf = HKDF.new(3);
@ -302,6 +304,39 @@ export function deriveBackupMediaKeyMaterial(
iv: material.subarray(BACKUP_MEDIA_MAC_KEY_LEN + BACKUP_MEDIA_AES_KEY_LEN),
};
}
export function deriveBackupMediaThumbnailInnerEncryptionKeyMaterial(
backupKey: Uint8Array,
mediaId: Uint8Array
): BackupMediaKeyMaterialType {
if (backupKey.byteLength !== BACKUP_KEY_LEN) {
throw new Error(
'deriveBackupMediaThumbnailKeyMaterial: invalid backup key length'
);
}
if (!mediaId.length) {
throw new Error('deriveBackupMediaThumbnailKeyMaterial: mediaId missing');
}
const hkdf = HKDF.new(3);
const material = hkdf.deriveSecrets(
BACKUP_MEDIA_MAC_KEY_LEN + BACKUP_MEDIA_AES_KEY_LEN + BACKUP_MEDIA_IV_LEN,
Buffer.from(backupKey),
Buffer.from(BACKUP_MEDIA_THUMBNAIL_ENCRYPT_INFO),
Buffer.from(mediaId)
);
return {
aesKey: material.subarray(0, BACKUP_MEDIA_AES_KEY_LEN),
macKey: material.subarray(
BACKUP_MEDIA_AES_KEY_LEN,
BACKUP_MEDIA_AES_KEY_LEN + BACKUP_MEDIA_MAC_KEY_LEN
),
iv: material.subarray(BACKUP_MEDIA_MAC_KEY_LEN + BACKUP_MEDIA_AES_KEY_LEN),
};
}
export function deriveStorageItemKey(
storageServiceKey: Uint8Array,
itemID: string