return full entryID on HTTP 409 responses

Signed-off-by: Bob Callaway <bcallaway@google.com>

pkg/api/entries.go

@@ -206,8 +206,15 @@ func createLogEntry(params entries.CreateLogEntryParams) (models.LogEntry, middl
 		case int32(code.Code_OK):
 		case int32(code.Code_ALREADY_EXISTS), int32(code.Code_FAILED_PRECONDITION):
 			existingUUID := hex.EncodeToString(rfc6962.DefaultHasher.HashLeaf(leaf))
-			err := fmt.Errorf("grpc error: %v", insertionStatus.String())
-			return nil, handleRekorAPIError(params, http.StatusConflict, err, fmt.Sprintf(entryAlreadyExists, existingUUID), "entryURL", getEntryURL(*params.HTTPRequest.URL, existingUUID))
+			activeTree := fmt.Sprintf("%x", api.logID)
+			entryIDstruct, err := sharding.CreateEntryIDFromParts(activeTree, existingUUID)
+			if err != nil {
+				err := fmt.Errorf("error creating EntryID from active treeID %v and uuid %v: %w", activeTree, existingUUID, err)
+				return nil, handleRekorAPIError(params, http.StatusInternalServerError, err, fmt.Sprintf(validationError, err))
+			}
+			existingEntryID := entryIDstruct.ReturnEntryIDString()
+			err = fmt.Errorf("grpc error: %v", insertionStatus.String())
+			return nil, handleRekorAPIError(params, http.StatusConflict, err, fmt.Sprintf(entryAlreadyExists, existingEntryID), "entryURL", getEntryURL(*params.HTTPRequest.URL, existingEntryID))
 		default:
 			err := fmt.Errorf("grpc error: %v", insertionStatus.String())
 			return nil, handleRekorAPIError(params, http.StatusInternalServerError, err, trillianUnexpectedResult)

pkg/types/intoto/e2e_test.go

@@ -42,6 +42,7 @@ import (
 	slsa "github.com/in-toto/in-toto-golang/in_toto/slsa_provenance/v0.2"
 	"github.com/secure-systems-lab/go-securesystemslib/dsse"
 	"github.com/sigstore/rekor/pkg/generated/models"
+	"github.com/sigstore/rekor/pkg/sharding"
 	"github.com/sigstore/rekor/pkg/types"
 	"github.com/sigstore/sigstore/pkg/signature"
 
@@ -161,7 +162,13 @@ func TestIntoto(t *testing.T) {
 
 	out = util.RunCli(t, "upload", "--artifact", attestationPath, "--type", "intoto", "--public-key", pubKeyPath)
 	util.OutputContains(t, out, "Entry already exists")
+	// issue1649 check for full UUID in printed Location value from 409 response header
+	if len(uuid) != sharding.EntryIDHexStringLen {
+		t.Fatal("UUID returned instead of entry ID (includes treeID)")
+	}
+	util.OutputContains(t, out, uuid)
 }
+
 func TestIntotoMultiSig(t *testing.T) {
 	td := t.TempDir()
 	attestationPath := filepath.Join(td, "attestation.json")