62 lines
1.7 KiB
TypeScript
62 lines
1.7 KiB
TypeScript
// Copyright 2020-2021 Signal Messenger, LLC
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// SPDX-License-Identifier: AGPL-3.0-only
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import { isNumber, omit } from 'lodash';
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import { strictAssert } from '../util/assert';
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import { dropNull } from '../util/dropNull';
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import type { DownloadedAttachmentType } from '../types/Attachment';
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import * as MIME from '../types/MIME';
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import * as Bytes from '../Bytes';
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import { getFirstBytes, decryptAttachment } from '../Crypto';
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import type { ProcessedAttachment } from './Types.d';
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import type { WebAPIType } from './WebAPI';
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export async function downloadAttachment(
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server: WebAPIType,
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attachment: ProcessedAttachment
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): Promise<DownloadedAttachmentType> {
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const cdnId = attachment.cdnId || attachment.cdnKey;
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const { cdnNumber } = attachment;
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if (!cdnId) {
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throw new Error('downloadAttachment: Attachment was missing cdnId!');
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}
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strictAssert(cdnId, 'attachment without cdnId');
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const encrypted = await server.getAttachment(cdnId, dropNull(cdnNumber));
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const { key, digest, size, contentType } = attachment;
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if (!digest) {
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throw new Error('Failure: Ask sender to update Signal and resend.');
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}
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strictAssert(key, 'attachment has no key');
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strictAssert(digest, 'attachment has no digest');
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const paddedData = decryptAttachment(
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encrypted,
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Bytes.fromBase64(key),
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Bytes.fromBase64(digest)
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);
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if (!isNumber(size)) {
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throw new Error(
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`downloadAttachment: Size was not provided, actual size was ${paddedData.byteLength}`
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);
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}
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const data = getFirstBytes(paddedData, size);
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return {
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...omit(attachment, 'digest', 'key'),
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size,
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contentType: contentType
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? MIME.stringToMIMEType(contentType)
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: MIME.APPLICATION_OCTET_STREAM,
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data,
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};
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}
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