Image package to append layers and push final image

pkg/constants/constants.go

@@ -24,4 +24,7 @@ const (
 	RootDir = "/"
 
 	WhitelistPath = "/proc/self/mountinfo"
+
+	// PolicyJSONPath is the path to the policy JSON
+	PolicyJSONPath = "/workspace/policy.json"
 )

pkg/image/image.go

@@ -0,0 +1,79 @@
+/*
+Copyright 2018 Google LLC
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+    http://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package image
+
+import (
+	img "github.com/GoogleCloudPlatform/container-diff/pkg/image"
+	"github.com/GoogleCloudPlatform/k8s-container-builder/pkg/constants"
+	"github.com/containers/image/copy"
+	"github.com/containers/image/docker"
+	"github.com/containers/image/signature"
+	"github.com/containers/image/transports/alltransports"
+	"github.com/sirupsen/logrus"
+)
+
+// sourceImage is the image that will be modified by the executor
+var sourceImage img.MutableSource
+
+// InitializeSourceImage initializes the source image with the base image
+func InitializeSourceImage(srcImg string) error {
+	ref, err := docker.ParseReference("//" + srcImg)
+	if err != nil {
+		return err
+	}
+	ms, err := img.NewMutableSource(ref)
+	if err != nil {
+		return err
+	}
+	sourceImage = *ms
+	return nil
+}
+
+// AppendLayer appends a layer onto the base image
+func AppendLayer(contents []byte) error {
+	return sourceImage.AppendLayer(contents)
+}
+
+// PushImage pushes the final image
+func PushImage(destImg string) error {
+	srcRef := &img.ProxyReference{
+		ImageReference: nil,
+		Src:            &sourceImage,
+	}
+	destRef, err := alltransports.ParseImageName("docker://" + destImg)
+	if err != nil {
+		return err
+	}
+	policyContext, err := getPolicyContext()
+	if err != nil {
+		return err
+	}
+	logrus.Infof("Pushing image to %s", destImg)
+	err = copy.Image(policyContext, destRef, srcRef, nil)
+	return err
+}
+
+func getPolicyContext() (*signature.PolicyContext, error) {
+	policy, err := signature.NewPolicyFromFile(constants.PolicyJsonPath)
+	if err != nil {
+		logrus.Debugf("Error retrieving policy: %s", err)
+		return nil, err
+	}
+	policyContext, err := signature.NewPolicyContext(policy)
+	if err != nil {
+		logrus.Debugf("Error retrieving policy context: %s", err)
+		return nil, err
+	}
+	return policyContext, nil
+}