feat(storage): enhance AWS S3 client configuration for presigned URLs

- Updated the AWS S3 client initialization to enforce SigV4 for presigned URLs, ensuring consistent header signing behavior across S3-compatible providers.
- Introduced a dedicated configuration for the S3 client to manage addressing styles and signature versions more effectively.

api/extensions/storage/aws_s3_storage.py

@@ -2,7 +2,7 @@ import logging
 from collections.abc import Generator
 
 import boto3
-from botocore.client import Config
+from botocore.client import BaseClient, Config
 from botocore.exceptions import ClientError
 
 from configs import dify_config
@@ -14,15 +14,34 @@ logger = logging.getLogger(__name__)
 class AwsS3Storage(BaseStorage):
     """Implementation for Amazon Web Services S3 storage."""
 
+    client: BaseClient
+
     def __init__(self):
         super().__init__()
         self.bucket_name = dify_config.S3_BUCKET_NAME
+
+        # NOTE:
+        # Some S3-compatible providers (e.g. MinIO) are strict about presigned request
+        # signature calculation. If the client sends a `Content-Type` header while the
+        # server generates a SigV2 presigned URL (or otherwise signs an empty Content-Type),
+        # the request may be rejected with 403 (signature mismatch).
+        #
+        # Enforce SigV4 for presigned URLs to avoid accidental SigV2 fallback and to keep
+        # header signing behavior consistent across providers.
+        s3_client_config = Config(
+            signature_version="s3v4",
+            s3={"addressing_style": dify_config.S3_ADDRESS_STYLE},
+        )
         if dify_config.S3_USE_AWS_MANAGED_IAM:
             logger.info("Using AWS managed IAM role for S3")
 
             session = boto3.Session()
             region_name = dify_config.S3_REGION
-            self.client = session.client(service_name="s3", region_name=region_name)
+            self.client = session.client(
+                service_name="s3",
+                region_name=region_name,
+                config=s3_client_config,
+            )
         else:
             logger.info("Using ak and sk for S3")
 
@@ -32,7 +51,7 @@ class AwsS3Storage(BaseStorage):
                 aws_access_key_id=dify_config.S3_ACCESS_KEY,
                 endpoint_url=dify_config.S3_ENDPOINT,
                 region_name=dify_config.S3_REGION,
-                config=Config(s3={"addressing_style": dify_config.S3_ADDRESS_STYLE}),
+                config=s3_client_config,
             )
         # create bucket
         try: