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[sha512] Configurable digest support for container image builds #519

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[sha512] Configurable digest support for container image builds #519

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17 changes: 9 additions & 8 deletions image/storage/storage_dest.go
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Original file line number Diff line number Diff line change
Expand Up @@ -37,6 +37,7 @@ import (
"go.podman.io/storage/pkg/chunked"
"go.podman.io/storage/pkg/chunked/toc"
"go.podman.io/storage/pkg/ioutils"
supporteddigests "go.podman.io/storage/pkg/supported-digests"
)

var (
Expand Down Expand Up @@ -288,7 +289,7 @@ func (s *storageImageDestination) putBlobToPendingFile(stream io.Reader, blobinf
}
defer decompressed.Close()

diffID := digest.Canonical.Digester()
diffID := supporteddigests.TmpDigestForNewObjects().Digester()
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@mtrmac mtrmac Dec 2, 2025

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This is more complex — the “Ensure that we always see the same “view” of a layer” code will compare the value to config’s RootFS.DiffIDs, and that might use a different digest.

Potentially, I guess we might need to compute two uncompressed digests: one to match against config, and one to identify the layer in c/storage at the user-wanted level of collision resistance.

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@mtrmac mtrmac Dec 2, 2025

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As a more generic version of this concern, note that all over the place layer.UncompressedDigest and layer.TOCDigest only contains one value per layer; and options.Cache.Cache.UncompressedDigest{,ForTOC} only records one value per blob.

I don’t know what we want to do there… at least for the BlobInfoCache, we might determine that a compressed-sha256=A matches uncompressed-sha512=B (if pulling an old image configured with …ForNewObjects=sha512). Do we want to use that knowledge? Maybe we do, for future pulls (a sha256 collision means a collision at the registry), or at least for pulls from the same registry, but not for future pushes (if we have a sha512 image, we don’t want to regress to sha256 strength on uploads)??

// Copy the data to the file.
// TODO: This can take quite some time, and should ideally be cancellable using context.Context.
_, err = io.Copy(diffID.Hash(), decompressed)
Expand Down Expand Up @@ -856,7 +857,7 @@ func (s *storageImageDestination) computeID(m manifest.Manifest) (string, error)
}
// ordinaryImageID is a digest of a config, which is a JSON value.
// To avoid the risk of collisions, start the input with @ so that the input is not a valid JSON.
tocImageID := digest.FromString("@With TOC:" + tocIDInput).Encoded()
tocImageID := supporteddigests.TmpDigestForNewObjects().FromString("@With TOC:" + tocIDInput).String()
logrus.Debugf("Ordinary storage image ID %s; a layer was looked up by TOC, so using image ID %s", ordinaryImageID, tocImageID)
return tocImageID, nil
}
Expand Down Expand Up @@ -1070,7 +1071,7 @@ func layerID(parentID string, trusted trustedLayerIdentityData) string {
if parentID == "" && !mustHash {
return component
}
return digest.Canonical.FromString(parentID + "+" + component).Encoded()
return supporteddigests.TmpDigestForNewObjects().FromString(parentID + "+" + component).String()
}

// createNewLayer creates a new layer newLayerID for (index, trusted) on top of parentLayer (which may be "").
Expand Down Expand Up @@ -1488,13 +1489,13 @@ func (s *storageImageDestination) CommitWithOptions(ctx context.Context, options
imgOptions.BigData = append(imgOptions.BigData, storage.ImageBigDataOption{
Key: s.lockProtected.configDigest.String(),
Data: v,
Digest: digest.Canonical.FromBytes(v),
Digest: supporteddigests.TmpDigestForNewObjects().FromBytes(v),
})
}
// Set up to save the options.UnparsedToplevel's manifest if it differs from
// the per-platform one, which is saved below.
if !bytes.Equal(toplevelManifest, s.manifest) {
manifestDigest, err := manifest.Digest(toplevelManifest)
manifestDigest, err := manifest.DigestWithAlgorithm(toplevelManifest, supporteddigests.TmpDigestForNewObjects())
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@mtrmac mtrmac Dec 2, 2025

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These values end up in storage.Image.Digests and are used for lookups (see “Look for an image with the specified digest that has the same name,”); so, if the user pulls a repo@digest, we must allow lookup by exactly that digest.

I don’t immediately know what we do when pulling by tag. One option might be to pre-compute and allow lookup only by (probably, Canonical and) the preferred digest. Another might be to add support for lookups by an arbitrary digest algorithm to c/storage, where c/storage would actually digest all recorded manifests using the provided algorithm (and, I guess, cache the values once computed, although that might require RW locks where RO locks used to suffice).

if err != nil {
return fmt.Errorf("digesting top-level manifest: %w", err)
}
Expand Down Expand Up @@ -1530,7 +1531,7 @@ func (s *storageImageDestination) CommitWithOptions(ctx context.Context, options
imgOptions.BigData = append(imgOptions.BigData, storage.ImageBigDataOption{
Key: "signatures",
Data: s.signatures,
Digest: digest.Canonical.FromBytes(s.signatures),
Digest: supporteddigests.TmpDigestForNewObjects().FromBytes(s.signatures),
})
}
for instanceDigest, signatures := range s.signatureses {
Expand All @@ -1541,7 +1542,7 @@ func (s *storageImageDestination) CommitWithOptions(ctx context.Context, options
imgOptions.BigData = append(imgOptions.BigData, storage.ImageBigDataOption{
Key: key,
Data: signatures,
Digest: digest.Canonical.FromBytes(signatures),
Digest: supporteddigests.TmpDigestForNewObjects().FromBytes(signatures),
})
}

Expand Down Expand Up @@ -1643,7 +1644,7 @@ func (s *storageImageDestination) CommitWithOptions(ctx context.Context, options

// PutManifest writes the manifest to the destination.
func (s *storageImageDestination) PutManifest(ctx context.Context, manifestBlob []byte, instanceDigest *digest.Digest) error {
digest, err := manifest.Digest(manifestBlob)
digest, err := manifest.DigestWithAlgorithm(manifestBlob, supporteddigests.TmpDigestForNewObjects())
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@mtrmac mtrmac Dec 2, 2025

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See elsewhere about lookups by manifest digest.

… but, also, see what PutSignaturesWithFormat does with the value. I’m not sure that actually makes a difference, the reader seems to ignore the entry for the top-level manifest digest, but that needs tracking down.

if err != nil {
return err
}
Expand Down
118 changes: 110 additions & 8 deletions image/storage/storage_dest_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -6,76 +6,178 @@ import (
"github.com/opencontainers/go-digest"
"github.com/stretchr/testify/assert"
"github.com/stretchr/testify/require"
supporteddigests "go.podman.io/storage/pkg/supported-digests"
)

func TestLayerID(t *testing.T) {
blobDigest, err := digest.Parse("sha256:0000000000000000000000000000000000000000000000000000000000000000")
blobDigestSHA256, err := digest.Parse("sha256:0000000000000000000000000000000000000000000000000000000000000000")
require.NoError(t, err)
blobDigestSHA512, err := digest.Parse("sha512:00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000")
require.NoError(t, err)

for _, c := range []struct {
algorithm digest.Algorithm
blobDigest digest.Digest
parentID string
identifiedByTOC bool
diffID string
tocDigest string
expected string
}{
{
algorithm: digest.SHA256,
blobDigest: blobDigestSHA256,
parentID: "",
identifiedByTOC: false,
diffID: "sha256:aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
tocDigest: "",
expected: "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
},
{
algorithm: digest.SHA256,
blobDigest: blobDigestSHA256,
parentID: "",
identifiedByTOC: false,
diffID: "sha256:aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
expected: "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
tocDigest: "sha256:bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb",
},
{
algorithm: digest.SHA256,
blobDigest: blobDigestSHA256,
parentID: "",
identifiedByTOC: true,
diffID: "",
tocDigest: "sha256:bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb",
expected: "07f60ddaf18a3d1fa18a71bf40f0b9889b473e26555d6fffdfbd72ba6a59469e",
expected: "sha256:07f60ddaf18a3d1fa18a71bf40f0b9889b473e26555d6fffdfbd72ba6a59469e",
},
{
algorithm: digest.SHA256,
blobDigest: blobDigestSHA256,
parentID: "",
identifiedByTOC: true,
diffID: "sha256:aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
tocDigest: "sha256:bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb",
expected: "07f60ddaf18a3d1fa18a71bf40f0b9889b473e26555d6fffdfbd72ba6a59469e",
expected: "sha256:07f60ddaf18a3d1fa18a71bf40f0b9889b473e26555d6fffdfbd72ba6a59469e",
},
{
algorithm: digest.SHA256,
blobDigest: blobDigestSHA256,
parentID: "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
identifiedByTOC: false,
diffID: "sha256:bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb",
tocDigest: "",
expected: "76f79efda453922cda1cecb6ec9e7cf9d86ea968c6dd199d4030dd00078a1686",
expected: "sha256:76f79efda453922cda1cecb6ec9e7cf9d86ea968c6dd199d4030dd00078a1686",
},
{
algorithm: digest.SHA256,
blobDigest: blobDigestSHA256,
parentID: "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
identifiedByTOC: false,
diffID: "sha256:bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb",
tocDigest: "sha256:cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc",
expected: "76f79efda453922cda1cecb6ec9e7cf9d86ea968c6dd199d4030dd00078a1686",
expected: "sha256:76f79efda453922cda1cecb6ec9e7cf9d86ea968c6dd199d4030dd00078a1686",
},
{
algorithm: digest.SHA256,
blobDigest: blobDigestSHA256,
parentID: "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
identifiedByTOC: true,
diffID: "",
tocDigest: "sha256:cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc",
expected: "468becc3d25ee862f81fd728d229a2b2487cfc9b3e6cf3a4d0af8c3fdde0e7a9",
expected: "sha256:468becc3d25ee862f81fd728d229a2b2487cfc9b3e6cf3a4d0af8c3fdde0e7a9",
},
{
algorithm: digest.SHA256,
blobDigest: blobDigestSHA256,
parentID: "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
identifiedByTOC: true,
diffID: "sha256:bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb",
tocDigest: "sha256:cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc",
expected: "468becc3d25ee862f81fd728d229a2b2487cfc9b3e6cf3a4d0af8c3fdde0e7a9",
expected: "sha256:468becc3d25ee862f81fd728d229a2b2487cfc9b3e6cf3a4d0af8c3fdde0e7a9",
},
{
algorithm: digest.SHA512,
blobDigest: blobDigestSHA512,
parentID: "",
identifiedByTOC: false,
diffID: "sha512:aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
tocDigest: "",
expected: "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
},
{
algorithm: digest.SHA512,
blobDigest: blobDigestSHA512,
parentID: "",
identifiedByTOC: false,
diffID: "sha512:aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
tocDigest: "sha512:bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb",
expected: "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
},
{
algorithm: digest.SHA512,
blobDigest: blobDigestSHA512,
parentID: "",
identifiedByTOC: true,
diffID: "",
tocDigest: "sha512:bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb",
expected: "sha512:129fa63234ab81f43f298346bb7159cc1c8fab6d8ae93f3438f8637f5079ea6dec6ea4740eb6bdbcae3ad1eb00af76011341b2f19fe590daf6f64f06e1302f52",
},
{
algorithm: digest.SHA512,
blobDigest: blobDigestSHA512,
parentID: "",
identifiedByTOC: true,
diffID: "sha512:aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
tocDigest: "sha512:bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb",
expected: "sha512:129fa63234ab81f43f298346bb7159cc1c8fab6d8ae93f3438f8637f5079ea6dec6ea4740eb6bdbcae3ad1eb00af76011341b2f19fe590daf6f64f06e1302f52",
},
{
algorithm: digest.SHA512,
blobDigest: blobDigestSHA512,
parentID: "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
identifiedByTOC: false,
diffID: "sha512:bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb",
tocDigest: "",
expected: "sha512:391623fa853a82d2795e8648f06b7c0eb880e345138dd6b9429132d9aa329ff1e6f7b76a3295b8b34d8682090056a798901b9b700e4059b1011d32b68a7bca21",
},
{
algorithm: digest.SHA512,
blobDigest: blobDigestSHA512,
parentID: "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
identifiedByTOC: false,
diffID: "sha512:bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb",
tocDigest: "sha512:cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc",
expected: "sha512:391623fa853a82d2795e8648f06b7c0eb880e345138dd6b9429132d9aa329ff1e6f7b76a3295b8b34d8682090056a798901b9b700e4059b1011d32b68a7bca21",
},
{
algorithm: digest.SHA512,
blobDigest: blobDigestSHA512,
parentID: "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
identifiedByTOC: true,
diffID: "",
tocDigest: "sha512:cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc",
expected: "sha512:0263be0fd3b851ffe02c877574d1d2b19625e36888e63eec2682de2210b6bbaea262e04085843eda16b7014fd59db6aafa0628c2a02443111ae568ea545b112e",
},
{
algorithm: digest.SHA512,
blobDigest: blobDigestSHA512,
parentID: "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
identifiedByTOC: true,
diffID: "sha512:bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb",
tocDigest: "sha512:cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc",
expected: "sha512:0263be0fd3b851ffe02c877574d1d2b19625e36888e63eec2682de2210b6bbaea262e04085843eda16b7014fd59db6aafa0628c2a02443111ae568ea545b112e",
},
} {
origAlg := supporteddigests.TmpDigestForNewObjects()
defer func() {
err := supporteddigests.TmpSetDigestForNewObjects(origAlg)
require.NoError(t, err)
}()

err := supporteddigests.TmpSetDigestForNewObjects(c.algorithm)
require.NoError(t, err)

var diffID, tocDigest digest.Digest
if c.diffID != "" {
diffID, err = digest.Parse(c.diffID)
Expand All @@ -98,7 +200,7 @@ func TestLayerID(t *testing.T) {
layerIdentifiedByTOC: c.identifiedByTOC,
diffID: diffID,
tocDigest: tocDigest,
blobDigest: blobDigest,
blobDigest: c.blobDigest,
})
assert.Equal(t, c.expected, res)
}
Expand Down
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