mc mirror without --disable-multipart generate some invalid requests

[the-glu]

Expected behavior

If I do a

/opt/minio/mc mirror --remove --overwrite --retry old/deeps-data new/deeps-data

without the --disable-multipart option, minio fail with the following error:

mc: <DEBUG> POST /deeps-data/data/00/a4/1c/19-0f62-453b-9975-925b3344bd52?uploads= HTTP/1.1
Host: **REDACTED**
User-Agent: MinIO (linux; amd64) minio-go/v7.0.70 mc/RELEASE.2024-06-12T14-34-03Z
Content-Length: 0
Accept-Encoding: zstd,gzip
Authorization: AWS4-HMAC-SHA256 Credential=**REDACTED**/20240722/us-east-1/s3/aws4_request, SignedHeaders=content-type;host;x-amz-checksum-algorithm;x-amz-content-sha256;x-amz-date, Signature=**REDACTED**
Content-Type: multipart/form-data
X-Amz-Checksum-Algorithm: CRC32C
X-Amz-Content-Sha256: UNSIGNED-PAYLOAD
X-Amz-Date: 20240722T122202Z

mc: <DEBUG> HTTP/1.1 400 Bad Request
Content-Length: 372
Accept-Ranges: bytes
Content-Type: application/xml
Date: Mon, 22 Jul 2024 12:22:02 GMT
Server: MinIO
Strict-Transport-Security: max-age=31536000
Vary: Origin
X-Amz-Id-2: 8703973134a8a51d367677607c2ed52e3cd578ceff22cc497def47c3d201d2a1
X-Amz-Request-Id: 17E48864783FA6C6
X-Content-Type-Options: nosniff
X-Xss-Protection: 1; mode=block

<?xml version="1.0" encoding="UTF-8"?>
<Error><Code>InvalidRequest</Code><Message>Invalid Request (request has multiple authentication types, please use one)</Message><Resource>/deeps-data/data/00/a4/1c/19-0f62-453b-9975-925b3344bd52</Resource><RequestId>17E48864783FA6C6</RequestId><HostId>8703973134a8a51d367677607c2ed52e3cd578ceff22cc497def47c3d201d2a1</HostId></Error>mc: <DEBUG> TLS Certificate found: 
mc: <DEBUG>  >> Country: US
mc: <DEBUG>  >> Organization: Let's Encrypt
mc: <DEBUG>  >> Expires: 2024-09-29 02:13:48 +0000 UTC
mc: <DEBUG> TLS Certificate found: 
mc: <DEBUG>  >> Country: US
mc: <DEBUG>  >> Organization: Internet Security Research Group
mc: <DEBUG>  >> Expires: 2027-03-12 23:59:59 +0000 UTC
mc: <DEBUG> Response Time: 1.282901ms

Steps to reproduce the behavior

Do a mc mirror with a big file that make mc use multipart uploads ?

mc --version

mc version RELEASE.2024-06-12T14-34-03Z (commit-id=e7c9a733c680fe62066d24e8718f81938b4f6606

(minio servers, both source and target: minio version RELEASE.2024-06-13T22-53-53Z)

[klauspost]

It seems the Content-Type: multipart/form-data is triggering isRequestPostPolicySignatureV4.

Presumably this is transferred from the source. Maybe correctly, maybe incorrectly.