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Enable downloading attachments from backup CDN

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trevor-signal 2024-05-02 13:11:34 -04:00 • committed by GitHub
parent 2964006b79
commit 1e8047cf73
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GPG key ID: B5690EEEBB952194
21 changed files with 989 additions and 385 deletions
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63
ts/Crypto.ts
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@ -208,10 +208,23 @@ export type BackupKeyMaterialType = Readonly<{
aesKey: Uint8Array;
}>;
export type BackupMediaKeyMaterialType = Readonly<{
macKey: Uint8Array;
aesKey: Uint8Array;
iv: Uint8Array;
}>;
const BACKUP_AES_KEY_LEN = 32;
const BACKUP_MAC_KEY_LEN = 32;
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_AES_KEY_LEN = 32;
const BACKUP_MEDIA_MAC_KEY_LEN = 32;
const BACKUP_MEDIA_IV_LEN = 16;
export function deriveBackupKeyMaterial(
backupKey: Uint8Array,
backupId: Uint8Array
@ -238,6 +251,56 @@ export function deriveBackupKeyMaterial(
};
}
export function deriveMediaIdFromMediaName(
backupKey: Uint8Array,
mediaName: string
): Uint8Array {
if (backupKey.byteLength !== BACKUP_KEY_LEN) {
throw new Error('deriveMediaIdFromMediaName: invalid backup key length');
}
if (!mediaName) {
throw new Error('deriveMediaIdFromMediaName: mediaName missing');
}
const hkdf = HKDF.new(3);
return hkdf.deriveSecrets(
BACKUP_MEDIA_ID_LEN,
Buffer.from(backupKey),
Buffer.from(BACKUP_MEDIA_ID_INFO),
Buffer.from(Bytes.fromBase64(mediaName))
);
}
export function deriveBackupMediaKeyMaterial(
backupKey: Uint8Array,
mediaId: Uint8Array
): BackupMediaKeyMaterialType {
if (backupKey.byteLength !== BACKUP_KEY_LEN) {
throw new Error('deriveMediaIdFromMediaName: invalid backup key length');
}
if (!mediaId.length) {
throw new Error('deriveMediaIdFromMediaName: 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_ENCRYPT_INFO),
Buffer.from(mediaId)
);
return {
macKey: material.subarray(0, BACKUP_MEDIA_MAC_KEY_LEN),
aesKey: material.subarray(
BACKUP_MEDIA_MAC_KEY_LEN,
BACKUP_MEDIA_MAC_KEY_LEN + BACKUP_MEDIA_AES_KEY_LEN
),
iv: material.subarray(BACKUP_MEDIA_MAC_KEY_LEN + BACKUP_MEDIA_AES_KEY_LEN),
};
}
export function deriveStorageItemKey(
storageServiceKey: Uint8Array,
itemID: string