fix: enable parsing of UUID-only rekor entry ID

pkg/fanal/artifact/image/remote_sbom.go

@@ -1,6 +1,7 @@
 package image
 
 import (
+	"bytes"
 	"context"
 	"encoding/json"
 	"errors"
@@ -61,10 +62,10 @@ func (a Artifact) inspectSBOMAttestation(ctx context.Context) (ftypes.ArtifactRe
 	for _, id := range entryIDs {
 		log.Logger.Debugf("Inspecting Rekor entry: %s", id)
 		ref, err := a.inspectRekorRecord(ctx, client, id)
-		if errors.Is(err, rekor.ErrNoAttestation) {
+		if errors.Is(err, rekor.ErrNoAttestation) || errors.Is(err, errNoSBOMFound) {
 			continue
 		} else if err != nil {
-			return ftypes.ArtifactReference{}, xerrors.Errorf("rekor rekord inspection error: %w", err)
+			return ftypes.ArtifactReference{}, xerrors.Errorf("rekor record inspection error: %w", err)
 		}
 		return ref, nil
 	}
@@ -111,6 +112,11 @@ func (a Artifact) inspectRekorRecord(ctx context.Context, client *rekor.Client,
 }
 
 func (a Artifact) parseStatement(entry rekor.Entry) (json.RawMessage, error) {
+	// Skip base64-encoded attestation
+	if bytes.HasPrefix(entry.Statement, []byte(`eyJ`)) {
+		return nil, errNoSBOMFound
+	}
+
 	// Parse statement of in-toto attestation
 	var raw json.RawMessage
 	statement := &in_toto.Statement{

pkg/rekor/client.go

@@ -22,20 +22,28 @@ const (
 
 var ErrNoAttestation = xerrors.Errorf("Rekor attestations not found")
 
-// EntryID is a hex-format string. The length of the string is 80.
-// It consists of two elements, the TreeID and the UUID.
+// EntryID is a hex-format string. The length of the string is 80 or 64.
+// If the length is 80, it consists of two elements, the TreeID and the UUID. If the length is 64,
+// it consists only of the UUID.
 // cf. https://github.com/sigstore/rekor/blob/4923f60f4ae55ccd4baf28d182e8f55c2d8097d3/pkg/sharding/sharding.go#L25-L36
-type EntryID string
+type EntryID struct {
+	TreeID string
+	UUID   string
+}
 
 func NewEntryID(entryID string) (EntryID, error) {
-	if len(entryID) == treeIDLen+uuidLen {
-		return EntryID(entryID), nil
+	switch len(entryID) {
+	case treeIDLen + uuidLen:
+		return EntryID{TreeID: entryID[:treeIDLen], UUID: entryID[treeIDLen:]}, nil
+	case uuidLen:
+		return EntryID{TreeID: "", UUID: entryID}, nil
+	default:
+		return EntryID{}, xerrors.New("invalid Entry ID length")
 	}
-	return "", xerrors.Errorf("invalid Entry ID length")
 }
 
-func (e EntryID) UUID() string {
-	return string(e)[treeIDLen:]
+func (e EntryID) String() string {
+	return e.TreeID + e.UUID
 }
 
 type Entry struct {
@@ -79,15 +87,15 @@ func (c *Client) Search(ctx context.Context, hash string) ([]EntryID, error) {
 }
 
 func (c *Client) GetEntry(ctx context.Context, entryID EntryID) (Entry, error) {
-	params := entries.NewGetLogEntryByUUIDParamsWithContext(ctx).WithEntryUUID(string(entryID))
+	params := entries.NewGetLogEntryByUUIDParamsWithContext(ctx).WithEntryUUID(entryID.String())
 
 	// TODO: bulk search
 	resp, err := c.Entries.GetLogEntryByUUID(params)
 	if err != nil {
 		return Entry{}, xerrors.Errorf("failed to get log entry by UUID: %w", err)
 	}
 
-	entry, found := resp.Payload[entryID.UUID()]
+	entry, found := resp.Payload[entryID.UUID]
 	if !found {
 		return Entry{}, ErrNoAttestation
 	}

pkg/rekor/client_test.go

@@ -30,8 +30,18 @@ func TestClient_Search(t *testing.T) {
 				hash: "92251458088c638061cda8fd8b403b76d661a4dc6b7ee71b6affcf1872557b2b",
 			},
 			want: []rekor.EntryID{
-				"392f8ecba72f4326eb624a7403756250b5f2ad58842a99d1653cd6f147f4ce9eda2da350bd908a55",
-				"392f8ecba72f4326414eaca77bd19bf5f378725d7fd79309605a81b69cc0101f5cd3119d0a216523",
+				{
+					TreeID: "392f8ecba72f4326",
+					UUID:   "eb624a7403756250b5f2ad58842a99d1653cd6f147f4ce9eda2da350bd908a55",
+				},
+				{
+					TreeID: "392f8ecba72f4326",
+					UUID:   "414eaca77bd19bf5f378725d7fd79309605a81b69cc0101f5cd3119d0a216523",
+				},
+				{
+					TreeID: "",
+					UUID:   "414eaca77bd19bf5f378725d7fd79309605a81b69cc0101f5cd3119d0a012345",
+				},
 			},
 		},
 		{
@@ -80,7 +90,10 @@ func TestClient_GetEntry(t *testing.T) {
 			name:             "happy path",
 			mockResponseFile: "testdata/log-entry.json",
 			args: args{
-				uuid: "392f8ecba72f43268b5b2debb565fd5cb05ae0d3935351fa3faabce558bede72e197b5722a742b1e",
+				uuid: rekor.EntryID{
+					TreeID: "392f8ecba72f4326",
+					UUID:   "8b5b2debb565fd5cb05ae0d3935351fa3faabce558bede72e197b5722a742b1e",
+				},
 			},
 			want: rekor.Entry{
 				Statement: []byte(`{"_type":"https://in-toto.io/Statement/v0.1","predicateType":"cosign.sigstore.dev/attestation/v1","subject":[{"name":"ghcr.io/aquasecurity/trivy-test-images","digest":{"sha256":"20d3f693dcffa44d6b24eae88783324d25cc132c22089f70e4fbfb858625b062"}}],"predicate":{"Data":"\"foo\\n\"\n","Timestamp":"2022-08-26T01:17:17Z"}}`),
@@ -90,7 +103,10 @@ func TestClient_GetEntry(t *testing.T) {
 			name:             "no attestation",
 			mockResponseFile: "testdata/log-entry-no-attestation.json",
 			args: args{
-				uuid: "392f8ecba72f43268b5b2debb565fd5cb05ae0d3935351fa3faabce558bede72e197b5722a742b1e",
+				uuid: rekor.EntryID{
+					TreeID: "392f8ecba72f4326",
+					UUID:   "8b5b2debb565fd5cb05ae0d3935351fa3faabce558bede72e197b5722a742b1e",
+				},
 			},
 			wantErr: rekor.ErrNoAttestation,
 		},

pkg/rekor/testdata/search-response.json

@@ -1,4 +1,5 @@
 [
   "392f8ecba72f4326eb624a7403756250b5f2ad58842a99d1653cd6f147f4ce9eda2da350bd908a55",
-  "392f8ecba72f4326414eaca77bd19bf5f378725d7fd79309605a81b69cc0101f5cd3119d0a216523"
+  "392f8ecba72f4326414eaca77bd19bf5f378725d7fd79309605a81b69cc0101f5cd3119d0a216523",
+  "414eaca77bd19bf5f378725d7fd79309605a81b69cc0101f5cd3119d0a012345"
 ]