Return location of existing entry if upload tried

cmd/cli/app/upload.go

@@ -30,15 +30,16 @@ import (
 )
 
 type uploadCmdOutput struct {
-	Location string
-	Index    int64
+	AlreadyExists bool
+	Location      string
+	Index         int64
 }
 
 func (u *uploadCmdOutput) String() string {
-	if u.Location != "" {
-		return fmt.Sprintf("Created entry at index %d, available at: %v%v\n", u.Index, viper.GetString("rekor_server"), u.Location)
+	if u.AlreadyExists {
+		return fmt.Sprintf("Entry already exists; available at: %v%v\n", viper.GetString("rekor_server"), u.Location)
 	}
-	return "Entry already exists.\n"
+	return fmt.Sprintf("Created entry at index %d, available at: %v%v\n", u.Index, viper.GetString("rekor_server"), u.Location)
 }
 
 // uploadCmd represents the upload command
@@ -84,9 +85,12 @@ var uploadCmd = &cobra.Command{
 
 		resp, err := rekorClient.Entries.CreateLogEntry(params)
 		if err != nil {
-			switch err.(type) {
+			switch e := err.(type) {
 			case *entries.CreateLogEntryConflict:
-				return &uploadCmdOutput{Location: ""}, nil
+				return &uploadCmdOutput{
+					Location:      e.Location.String(),
+					AlreadyExists: true,
+				}, nil
 			default:
 				return nil, err
 			}

openapi.yaml

@@ -432,6 +432,10 @@ responses:
     description: The request conflicts with the current state of the transparency log
     schema:
       $ref: "#/definitions/Error"
+    headers:
+      Location:
+        type: string
+        format: uri
   NotFound:
     description: The content requested could not be found
   InternalServerError:

pkg/api/entries.go

@@ -23,6 +23,7 @@ import (
 	"errors"
 	"fmt"
 	"net/http"
+	"net/url"
 
 	"github.com/google/trillian"
 	"github.com/spf13/viper"
@@ -102,7 +103,8 @@ func CreateLogEntryHandler(params entries.CreateLogEntryParams) middleware.Respo
 		switch insertionStatus.Code {
 		case int32(code.Code_OK):
 		case int32(code.Code_ALREADY_EXISTS), int32(code.Code_FAILED_PRECONDITION):
-			return handleRekorAPIError(params, http.StatusConflict, fmt.Errorf("grpc error: %v", insertionStatus.String()), entryAlreadyExists)
+			existingUUID := hex.EncodeToString(rfc6962.DefaultHasher.HashLeaf(leaf))
+			return handleRekorAPIError(params, http.StatusConflict, fmt.Errorf("grpc error: %v", insertionStatus.String()), fmt.Sprintf(entryAlreadyExists, existingUUID), "entryURL", getEntryURL(*httpReq.URL, existingUUID))
 		default:
 			return handleRekorAPIError(params, http.StatusInternalServerError, fmt.Errorf("grpc error: %v", insertionStatus.String()), trillianUnexpectedResult)
 		}
@@ -131,13 +133,17 @@ func CreateLogEntryHandler(params entries.CreateLogEntryParams) middleware.Respo
 		}()
 	}
 
-	locationURL := httpReq.URL
+	return entries.NewCreateLogEntryCreated().WithPayload(logEntry).WithLocation(getEntryURL(*httpReq.URL, uuid)).WithETag(uuid)
+}
+
+func getEntryURL(locationURL url.URL, uuid string) strfmt.URI {
 	// remove API key from output
 	query := locationURL.Query()
 	query.Del("apiKey")
 	locationURL.RawQuery = query.Encode()
 	locationURL.Path = fmt.Sprintf("%v/%v", locationURL.Path, uuid)
-	return entries.NewCreateLogEntryCreated().WithPayload(logEntry).WithLocation(strfmt.URI(locationURL.String())).WithETag(uuid)
+	return strfmt.URI(locationURL.String())
+
 }
 
 func GetLogEntryByUUIDHandler(params entries.GetLogEntryByUUIDParams) middleware.Responder {

pkg/api/error.go

@@ -21,6 +21,7 @@ import (
 	"regexp"
 
 	"github.com/go-openapi/runtime/middleware"
+	"github.com/go-openapi/strfmt"
 	"github.com/mitchellh/mapstructure"
 	"github.com/sigstore/rekor/pkg/generated/models"
 	"github.com/sigstore/rekor/pkg/generated/restapi/operations/entries"
@@ -33,7 +34,7 @@ const (
 	trillianCommunicationError     = "Unexpected error communicating with transparency log"
 	trillianUnexpectedResult       = "Unexpected result from transparency log"
 	failedToGenerateCanonicalEntry = "Error generating canonicalized entry"
-	entryAlreadyExists             = "An equivalent entry already exists in the transparency log"
+	entryAlreadyExists             = "An equivalent entry already exists in the transparency log with UUID %v"
 	firstSizeLessThanLastSize      = "firstSize(%d) must be less than lastSize(%d)"
 	malformedUUID                  = "UUID must be a 64-character hexadecimal string"
 	malformedHash                  = "Hash must be a 64-character hexadecimal string created from SHA256 algorithm"
@@ -98,7 +99,19 @@ func handleRekorAPIError(params interface{}, code int, err error, message string
 		case http.StatusBadRequest:
 			return entries.NewCreateLogEntryBadRequest().WithPayload(errorMsg(message, code))
 		case http.StatusConflict:
-			return entries.NewCreateLogEntryConflict().WithPayload(errorMsg(message, code))
+			resp := entries.NewCreateLogEntryConflict().WithPayload(errorMsg(message, code))
+			locationFound := false
+			for _, field := range fields {
+				if locationFound {
+					existingURL := field.(strfmt.URI)
+					resp.SetLocation(existingURL)
+					break
+				} else if field.(string) == "entryURL" {
+					locationFound = true
+					continue
+				}
+			}
+			return resp
 		default:
 			return entries.NewCreateLogEntryDefault(code).WithPayload(errorMsg(message, code))
 		}