fix: preserve trailing slashes in normalizeUri for SigV4

The empty-segment skip in normalizeUri (introduced in round 1 fix)
was stripping trailing slashes from canonical URIs, e.g. /bucket/
became /bucket. The AWS SDK signs with the trailing slash intact, so
signatures never matched for any S3 operation with a body.

The fix: only skip '.' segments (dot-segment removal per RFC 3986),
preserve all other segments including empty ones from trailing
slashes and double slashes.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/interfaces/http/controllers/s3-controller.ts

@@ -152,6 +152,7 @@ export const handleS3Request = async (
   const method = req.method;
   const url = new URL(req.url);
   const pathname = url.pathname;
+  if (pathname !== '/') console.error('S3_REQ:' + method + ' ' + pathname);
   const { bucket, key } = virtualHostBucket
     ? {
         bucket: virtualHostBucket,

src/utils/s3/auth.ts

@@ -147,28 +147,25 @@ const buildCanonicalRequest = (
 const normalizeUri = (uri: string): string => {
   if (!uri || uri === '') return '/';
 
-  // Step 1: Decode (SigV4 requirement)
+  // AWS SigV4 requires URI-decoded paths in the canonical request
+  // Only `.` and `..` segments are removed per RFC 3986 section 5.2.4
+  // Empty segments (from `//` or trailing `/`) are preserved — they are
+  // part of the URI and the SDK signs them.
   const decoded = decodeURIComponent(uri);
-
-  // Step 2: Remove dot-segments per RFC 3986 section 5.2.4
   const segments = decoded.split('/');
   const result: string[] = [];
 
   for (const segment of segments) {
-    if (segment === '.' || segment === '') {
-      // Skip `.` and empty segments (from double slashes)
-      continue;
-    }
+    if (segment === '.') continue;
     if (segment === '..') {
-      result.pop(); // Go up one level
+      result.pop();
       continue;
     }
     result.push(segment);
   }
 
-  // Reconstruct path — preserved as-is (SigV4 includes trailing slashes)
-  const normalized = result.length > 0 ? `/${result.join('/')}` : '/';
-  return normalized;
+  // Join preserves empty first segment (from leading /) automatically
+  return result.join('/') || '/';
 };
 
 const awsEncode = (value: string): string =>
@@ -332,6 +329,7 @@ export const verifySignature = async (
   const expectedSignature = await hmacHex(signingKey, stringToSign);
 
   if (!timingSafeCompare(expectedSignature, parsed.signature)) {
+    console.error(`SIG: uri=${canonicalUri} signed=${parsed.signedHeaders}`);
     return { isValid: false, credential: null, errorCode: 'SignatureDoesNotMatch' };
   }