fix: verify presigned S3 URLs against public host
This commit is contained in:
asepharyana
+14
-11
@@ -160,7 +160,8 @@ export const handleS3Request = async (req: Request): Promise<Response> => {
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}
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// Standard object operations
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if (method === 'GET') return handleGetObject(bucket, key, searchParams, reqId);
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if (method === 'GET')
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return handleGetObject(bucket, key, searchParams, headers, req.url, reqId);
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if (method === 'HEAD') return handleHeadObject(bucket, key, reqId);
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if (method === 'PUT') return handlePutObject(bucket, key, searchParams, headers, req, reqId);
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if (method === 'DELETE') return handleDeleteObject(bucket, key, reqId);
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@@ -264,21 +265,23 @@ const handleGetObject = async (
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bucket: string,
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key: string,
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searchParams: URLSearchParams,
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headers: Record<string, string>,
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requestUrl: string,
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reqId: string,
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): Promise<Response> => {
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if (searchParams.has('X-Amz-Signature')) {
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const fullUrl = `http://localhost/${bucket}/${key}?${searchParams.toString()}`;
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const presignedResult = await verifyPresignedUrl(
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fullUrl,
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'GET',
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config.s3AccessKey,
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config.s3SecretKey,
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REGION,
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);
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const presignedResult = await verifyPresignedUrl({
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url: requestUrl,
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method: 'GET',
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headers,
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s3AccessKey: config.s3AccessKey,
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s3SecretKey: config.s3SecretKey,
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region: REGION,
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});
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if (!presignedResult.isValid) {
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return s3ErrorResponse(
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'AccessDenied',
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'Request has expired',
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presignedResult.errorCode || 'AccessDenied',
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'Presigned URL verification failed',
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`/${bucket}/${key}`,
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403,
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reqId,
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+92
-63
@@ -9,6 +9,16 @@ export interface SigV4Result {
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errorCode?: string;
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}
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export interface VerifyPresignedUrlInput {
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url: string;
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method: string;
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headers: Record<string, string>;
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s3AccessKey: string;
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s3SecretKey: string;
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region: string;
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now?: Date;
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}
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const SERVICE = 's3';
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const TERMINATION = 'aws4_request';
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@@ -101,16 +111,26 @@ const normalizeUri = (uri: string): string => {
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return decodeURIComponent(uri);
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};
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const buildCanonicalQueryString = (searchParams: URLSearchParams): string => {
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const params: string[] = [];
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const keys = Array.from(searchParams.keys()).sort();
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for (const key of keys) {
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const values = searchParams.getAll(key).sort();
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for (const value of values) {
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params.push(`${encodeURIComponent(key)}=${encodeURIComponent(value)}`);
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}
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const awsEncode = (value: string): string =>
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encodeURIComponent(value).replace(
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/[!'()*]/g,
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(ch) => `%${ch.charCodeAt(0).toString(16).toUpperCase()}`,
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);
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export const buildCanonicalQueryString = (
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searchParams: URLSearchParams,
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excludeKeys: Set<string> = new Set(),
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): string => {
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const pairs: Array<[string, string]> = [];
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for (const [key, value] of searchParams.entries()) {
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if (!excludeKeys.has(key)) pairs.push([key, value]);
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}
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return params.join('&');
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pairs.sort(([ak, av], [bk, bv]) => {
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const a = `${awsEncode(ak)}=${awsEncode(av)}`;
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const b = `${awsEncode(bk)}=${awsEncode(bv)}`;
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return a.localeCompare(b);
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});
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return pairs.map(([key, value]) => `${awsEncode(key)}=${awsEncode(value)}`).join('&');
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};
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const getHashedPayload = async (
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@@ -191,88 +211,97 @@ export const verifySignature = async (
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};
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};
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export const verifyPresignedUrl = async (
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url: string,
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method: string,
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s3AccessKey: string,
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s3SecretKey: string,
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region: string,
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): Promise<SigV4Result> => {
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const parsedUrl = new URL(url);
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const queryParams = Object.fromEntries(parsedUrl.searchParams.entries());
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const parseAmzDateUtc = (amzDate: string): Date | null => {
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const match = amzDate.match(/^(\d{4})(\d{2})(\d{2})T(\d{2})(\d{2})(\d{2})Z$/);
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if (!match) return null;
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const [, year, month, day, hour, minute, second] = match;
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return new Date(
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Date.UTC(
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Number.parseInt(year, 10),
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Number.parseInt(month, 10) - 1,
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Number.parseInt(day, 10),
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Number.parseInt(hour, 10),
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Number.parseInt(minute, 10),
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Number.parseInt(second, 10),
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),
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);
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};
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const algorithm = queryParams['X-Amz-Algorithm'];
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const credential = queryParams['X-Amz-Credential'];
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const signedHeaders = queryParams['X-Amz-SignedHeaders'];
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const signature = queryParams['X-Amz-Signature'];
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const expires = parseInt(queryParams['X-Amz-Expires'] || '0', 10);
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const amzDate = queryParams['X-Amz-Date'];
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export const verifyPresignedUrl = async ({
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url,
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method,
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headers,
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s3AccessKey,
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s3SecretKey,
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region,
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now = new Date(),
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}: VerifyPresignedUrlInput): Promise<SigV4Result> => {
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const parsedUrl = new URL(url);
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const searchParams = parsedUrl.searchParams;
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const algorithm = searchParams.get('X-Amz-Algorithm');
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const credential = searchParams.get('X-Amz-Credential');
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const signedHeaders = searchParams.get('X-Amz-SignedHeaders');
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const signature = searchParams.get('X-Amz-Signature');
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const expiresText = searchParams.get('X-Amz-Expires');
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const amzDate = searchParams.get('X-Amz-Date');
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if (
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!algorithm ||
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algorithm !== 'AWS4-HMAC-SHA256' ||
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!credential ||
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!signedHeaders ||
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!signature ||
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!expires ||
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!expiresText ||
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!amzDate
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) {
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return { isValid: false, credential: null, errorCode: 'AccessDenied' };
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}
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// Check expiration
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const dateObj = new Date(
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parseInt(amzDate.substring(0, 4), 10),
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parseInt(amzDate.substring(4, 6), 10) - 1,
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parseInt(amzDate.substring(6, 8), 10),
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parseInt(amzDate.substring(9, 11), 10),
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parseInt(amzDate.substring(11, 13), 10),
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parseInt(amzDate.substring(13, 15), 10),
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);
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const expiresMs = expires * 1000;
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if (Date.now() > dateObj.getTime() + expiresMs) {
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const expires = Number.parseInt(expiresText, 10);
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const signedAt = parseAmzDateUtc(amzDate);
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if (!Number.isFinite(expires) || expires <= 0 || !signedAt) {
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return { isValid: false, credential: null, errorCode: 'AccessDenied' };
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}
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if (now.getTime() > signedAt.getTime() + expires * 1000) {
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return { isValid: false, credential: null, errorCode: 'AccessDenied' };
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}
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const credParts = credential.split('/');
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const presignedAccessKey = credParts[0];
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if (presignedAccessKey !== s3AccessKey) {
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if (credParts.length !== 5) {
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return { isValid: false, credential: null, errorCode: 'AccessDenied' };
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}
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const [accessKey, dateStamp, credentialRegion, service, termination] = credParts;
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if (
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accessKey !== s3AccessKey ||
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credentialRegion !== region ||
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service !== SERVICE ||
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termination !== TERMINATION
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) {
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return { isValid: false, credential: null, errorCode: 'SignatureDoesNotMatch' };
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}
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const dateStamp = credParts[1] || amzDate.substring(0, 8);
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const canonicalUri = normalizeUri(parsedUrl.pathname);
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const sortedParams = new URLSearchParams();
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const paramKeys = Object.keys(queryParams).sort();
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for (const key of paramKeys) {
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if (key !== 'X-Amz-Signature') {
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sortedParams.append(key, queryParams[key]);
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}
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}
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const canonicalQueryString = buildCanonicalQueryString(sortedParams);
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// Build canonical headers for presigned URL — only 'host' is typically signed
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const signedHeaderList = signedHeaders.split(';').filter(Boolean);
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const canonicalHeaders = signedHeaderList
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.map((h) => `${h.toLowerCase()}:${h === 'host' ? parsedUrl.host : ''}\n`)
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.map((headerName) => {
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const lower = headerName.toLowerCase();
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const value = lower === 'host' ? headers.host || parsedUrl.host : headers[lower] || '';
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return `${lower}:${value.trim()}\n`;
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})
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.join('');
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const hashedPayload = 'UNSIGNED-PAYLOAD';
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const canonicalRequest = `${method}\n${canonicalUri}\n${canonicalQueryString}\n${canonicalHeaders}\n${signedHeaders}\n${hashedPayload}`;
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const canonicalRequest = `${method}\n${normalizeUri(parsedUrl.pathname)}\n${buildCanonicalQueryString(searchParams, new Set(['X-Amz-Signature']))}\n${canonicalHeaders}\n${signedHeaders}\nUNSIGNED-PAYLOAD`;
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const hashedCanonicalRequest = await sha256Hex(canonicalRequest);
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const credentialScope = `${dateStamp}/${region}/s3/aws4_request`;
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const credentialScope = `${dateStamp}/${region}/${SERVICE}/${TERMINATION}`;
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const stringToSign = `AWS4-HMAC-SHA256\n${amzDate}\n${credentialScope}\n${hashedCanonicalRequest}`;
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const signingKey = await getSigningKey(s3SecretKey, dateStamp, region);
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const expectedSignature = await hmacHex(signingKey, stringToSign);
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const expectedSignature = await hmacHex(
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await getSigningKey(s3SecretKey, dateStamp, region),
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stringToSign,
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);
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if (expectedSignature !== signature) {
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return { isValid: false, credential: null, errorCode: 'SignatureDoesNotMatch' };
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}
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return { isValid: true, credential: null };
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return { isValid: true, credential: { accessKey, date: dateStamp, region, service } };
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};
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export const isS3Request = (headers: Record<string, string>): boolean => {
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