fix(server): Use uncompressed tarball hashes in image config

Docker expects hashes of compressed tarballs in the manifest (as these
are used to fetch from the content-addressable layer store), but for
some reason it expects hashes in the configuration layer to be of
uncompressed tarballs.

To achieve this an additional SHA256 hash is calculcated while
creating the layer tarballs, but before passing them to the gzip
writer.

In the current constellation the symlink layer is first compressed and
then decompressed again to calculate its hash. This can be refactored
in a future change.

1 files changed, 4 insertions, 2 deletions

diff --git a/tools/nixery/server/manifest/manifest.go b/tools/nixery/server/manifest/manifest.go
index 8e65fa223b18..8ad828239591 100644
--- a/tools/nixery/server/manifest/manifest.go
+++ b/tools/nixery/server/manifest/manifest.go
@@ -29,9 +29,10 @@ type Entry struct {
 	Size      int64  `json:"size"`
 	Digest    string `json:"digest"`
 
-	// This field is internal to Nixery and not part of the
+	// These fields are internal to Nixery and not part of the
 	// serialised entry.
 	MergeRating uint64 `json:"-"`
+	TarHash     string `json:",omitempty"`
 }
 
 type manifest struct {
@@ -102,9 +103,10 @@ func Manifest(layers []Entry) (json.RawMessage, ConfigLayer) {
 
 	hashes := make([]string, len(layers))
 	for i, l := range layers {
+		hashes[i] = l.TarHash
 		l.MediaType = layerType
+		l.TarHash = ""
 		layers[i] = l
-		hashes[i] = l.Digest
 	}
 
 	c := configLayer(hashes)