hash.Checksum.AddPart returned before seeding the accumulator when the
part was empty, so a multipart object with no content at all ended up
with no checksum instead of the checksum of zero bytes. Completing such
an upload failed with XAmzContentChecksumMismatch when the client
supplied the correct object checksum, and stored an empty checksum when
it did not.
Run the type check and the first checksum seeding before the zero size
early return. Appending zero bytes still leaves an existing accumulator
unchanged, so only the all empty case changes: a zero length part
followed by content already merged correctly, because prepending no bytes
does not alter a CRC.
AddPart has a single production caller, the multipart completion path, and
its part checksum type is derived from the upload's own checksum type, so
the type check now reached for zero sized parts cannot fire there.
Add a table test over CRC32, CRC32C and CRC64NVME covering every position
an empty part can take, and an API level zero length full object upload
that exercises the persisted AppendTo/ReadCheckSums round trip.
Co-authored-by: ChatGPT <noreply@openai.com>
Co-authored-by: Claude <noreply@anthropic.com>
CompleteMultipartUpload compared the per-part checksum taken from the
request body against the stored part checksum unconditionally, so a
client that sent only PartNumber and ETag for each part failed with
InvalidPart.
AWS S3 requires part level checksums in the completion body only for
composite checksum types. For full object types the client sends the
object level checksum in the request headers instead and does not retain
per-part values - that is the point of FULL_OBJECT. Reproduced with
boto3 1.43.58: it puts x-amz-checksum-crc32 on each UploadPart and the
full object checksum on the completion headers, but emits only ETag and
PartNumber in the completion body. A caller could only get such an upload
through by collecting the per-part checksums from the UploadPart
responses and echoing them back, which is exactly the bookkeeping
FULL_OBJECT exists to avoid and which no off-the-shelf SDK call does.
minio-go does echo them, which is why mc never hit this.
Treat the part checksum as optional when the upload declared a full
object checksum type and the client sent no part checksum at all. A part
carrying any checksum is still validated against the stored one -
including one sent under the wrong algorithm, which cannot match and is
rejected - composite uploads keep requiring a checksum for every part,
and the merged object checksum is still computed from the server stored,
upload time validated part checksums, never from client supplied values,
so integrity is unchanged.
Covered by API level tests over CRC32, CRC32C and CRC64NVME on both the
single drive and erasure backends, with guards for a wrong object
checksum, a wrong part checksum, a part checksum under another algorithm,
a mix of present and omitted part checksums, an absent object checksum,
and composite uploads still requiring every part checksum.
Fixes#31
Reported-by: Christophe Bornet <cbornet@users.noreply.github.com>
Co-authored-by: ChatGPT <noreply@openai.com>
Co-authored-by: Claude <noreply@anthropic.com>
Feng Ruohang