discrepancy with AWS S3 for non-utf8 key names

[kahing]

S3Proxy returns 404 when I try to HEAD a key that's not valid utf8, whereas aws returns 400. For ListObject, both return 403.

AWS S3:

2017/03/14 00:06:58 DEBUG: Request s3/HeadObject Details:
---[ REQUEST POST-SIGN ]-----------------------------
HEAD http://s3-us-west-2.amazonaws.com/zwryrjs2vjnu5su7/%AE%8A- HTTP/1.1
Host: s3-us-west-2.amazonaws.com
User-Agent: aws-sdk-go/1.0.0 (go1.7.5; linux; amd64)
Authorization: AWS4-HMAC-SHA256 Credential=AKIAJZP3GQRDDHSDPVOA/20170314/us-west-2/s3/aws4_request, SignedHeaders=host;x-amz-date, Signature=c2e525178f22ff31477cd2f39aa56b00e6ccbbd6e6c77512232db8ef2eb32884
X-Amz-Content-Sha256: e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855
X-Amz-Date: 20170314T070658Z
-----------------------------------------------------
2017/03/14 00:06:58 DEBUG: Response s3/HeadObject Details:
---[ RESPONSE ]--------------------------------------
HTTP/1.1 400 Bad Request
Connection: close
Transfer-Encoding: chunked
Content-Type: application/xml
Date: Tue, 14 Mar 2017 07:06:58 GMT
Server: AmazonS3
X-Amz-Id-2: uTuLEkOBaQu+7qlioztYjl1AimGyhrK3E0g0LZCp0S9LgRLvy2CTOmVF3Dmv4BJ/YtvQWPr2q18=
X-Amz-Request-Id: CE60C5D3261F9937

[gaul]

Upstream issues: CODEC-228 and ceph/s3-tests#156.