Merge branch 'master' into fix-toc-in-readme

.golangci.yaml

@@ -0,0 +1,191 @@
+# This file contains all available configuration options
+# with their default values.
+
+# options for analysis running
+run:
+  # default concurrency is a available CPU number
+  concurrency: 4
+
+  # timeout for analysis, e.g. 30s, 5m, default is 1m
+  deadline: 1m
+
+  # exit code when at least one issue was found, default is 1
+  issues-exit-code: 1
+
+  # include test files or not, default is true
+  tests: true
+
+  # list of build tags, all linters use it. Default is empty list.
+  build-tags:
+
+  # which dirs to skip: they won't be analyzed;
+  # can use regexp here: generated.*, regexp is applied on full path;
+  # default value is empty list, but next dirs are always skipped independently
+  # from this option's value:
+  #   	vendor$, third_party$, testdata$, examples$, Godeps$, builtin$
+  skip-dirs:
+
+  # which files to skip: they will be analyzed, but issues from them
+  # won't be reported. Default value is empty list, but there is
+  # no need to include all autogenerated files, we confidently recognize
+  # autogenerated files. If it's not please let us know.
+  skip-files:
+
+# output configuration options
+output:
+  # colored-line-number|line-number|json|tab|checkstyle, default is "colored-line-number"
+  format: colored-line-number
+
+  # print lines of code with issue, default is true
+  print-issued-lines: true
+
+  # print linter name in the end of issue text, default is true
+  print-linter-name: true
+
+
+# all available settings of specific linters
+linters-settings:
+  errcheck:
+    # report about not checking of errors in type assetions: `a := b.(MyStruct)`;
+    # default is false: such cases aren't reported by default.
+    check-type-assertions: false
+
+    # report about assignment of errors to blank identifier: `num, _ := strconv.Atoi(numStr)`;
+    # default is false: such cases aren't reported by default.
+    check-blank: false
+  govet:
+    # report about shadowed variables
+    #check-shadowing: true
+
+    # Obtain type information from installed (to $GOPATH/pkg) package files:
+    # golangci-lint will execute `go install -i` and `go test -i` for analyzed packages
+    # before analyzing them.
+    # By default this option is disabled and govet gets type information by loader from source code.
+    # Loading from source code is slow, but it's done only once for all linters.
+    # Go-installing of packages first time is much slower than loading them from source code,
+    # therefore this option is disabled by default.
+    # But repeated installation is fast in go >= 1.10 because of build caching.
+    # Enable this option only if all conditions are met:
+    #  1. you use only "fast" linters (--fast e.g.): no program loading occurs
+    #  2. you use go >= 1.10
+    #  3. you do repeated runs (false for CI) or cache $GOPATH/pkg or `go env GOCACHE` dir in CI.
+    #use-installed-packages: false
+  golint:
+    # minimal confidence for issues, default is 0.8
+    min-confidence: 0.8
+  gofmt:
+    # simplify code: gofmt with `-s` option, true by default
+    simplify: true
+  #gocyclo:
+  #  # minimal code complexity to report, 30 by default (but we recommend 10-20)
+  #  min-complexity: 10
+  maligned:
+    # print struct with more effective memory layout or not, false by default
+    suggest-new: true
+  #dupl:
+  #  # tokens count to trigger issue, 150 by default
+  #  threshold: 100
+  goconst:
+    # minimal length of string constant, 3 by default
+    min-len: 3
+    # minimal occurrences count to trigger, 3 by default
+    min-occurrences: 3
+  #depguard:
+  #  list-type: blacklist
+  #  include-go-root: false
+  #  packages:
+  #    - github.com/davecgh/go-spew/spew
+  misspell:
+    # Correct spellings using locale preferences for US or UK.
+    # Default is to use a neutral variety of English.
+    # Setting locale to US will correct the British spelling of 'colour' to 'color'.
+    locale: US
+  #lll:
+  #  # max line length, lines longer will be reported. Default is 120.
+  #  # '\t' is counted as 1 character by default, and can be changed with the tab-width option
+  #  line-length: 120
+  #  # tab width in spaces. Default to 1.
+  #  tab-width: 1
+  unused:
+    # treat code as a program (not a library) and report unused exported identifiers; default is false.
+    # XXX: if you enable this setting, unused will report a lot of false-positives in text editors:
+    # if it's called for subdir of a project it can't find funcs usages. All text editor integrations
+    # with golangci-lint call it on a directory with the changed file.
+    check-exported: false
+  unparam:
+    # call graph construction algorithm (cha, rta). In general, use cha for libraries,
+    # and rta for programs with main packages. Default is cha.
+    algo: cha
+
+    # Inspect exported functions, default is false. Set to true if no external program/library imports your code.
+    # XXX: if you enable this setting, unparam will report a lot of false-positives in text editors:
+    # if it's called for subdir of a project it can't find external interfaces. All text editor integrations
+    # with golangci-lint call it on a directory with the changed file.
+    check-exported: false
+  #nakedret:
+  #  # make an issue if func has more lines of code than this setting and it has naked returns; default is 30
+  #  max-func-lines: 30
+  #prealloc:
+  #  # XXX: we don't recommend using this linter before doing performance profiling.
+  #  # For most programs usage of prealloc will be a premature optimization.
+
+  #  # Report preallocation suggestions only on simple loops that have no returns/breaks/continues/gotos in them.
+  #  # True by default.
+  #  simple: true
+  #  range-loops: true # Report preallocation suggestions on range loops, true by default
+  #  for-loops: false # Report preallocation suggestions on for loops, false by default
+
+
+linters:
+  enable:
+    - goconst
+    - goimports
+    - golint
+    - interfacer
+    - maligned
+    - misspell
+    - unconvert
+    - unparam
+  enable-all: false
+  disable:
+    - errcheck
+    - gas
+  disable-all: false
+  presets:
+    - bugs
+    - unused
+  fast: false
+
+
+issues:
+  # List of regexps of issue texts to exclude, empty list by default.
+  # But independently from this option we use default exclude patterns,
+  # it can be disabled by `exclude-use-default: false`. To list all
+  # excluded by default patterns execute `golangci-lint run --help`
+  exclude:
+
+  # Independently from option `exclude` we use default exclude patterns,
+  # it can be disabled by this option. To list all
+  # excluded by default patterns execute `golangci-lint run --help`.
+  # Default value for this option is true.
+  exclude-use-default: true
+
+  # Maximum issues count per one linter. Set to 0 to disable. Default is 50.
+  max-per-linter: 50
+
+  # Maximum count of issues with the same text. Set to 0 to disable. Default is 3.
+  max-same: 3
+
+  # Show only new issues: if there are unstaged changes or untracked files,
+  # only those changes are analyzed, else only changes in HEAD~ are analyzed.
+  # It's a super-useful option for integration of golangci-lint into existing
+  # large codebase. It's not practical to fix all existing issues at the moment
+  # of integration: much better don't allow issues in new code.
+  # Default is false.
+  new: false
+
+  ## Show only new issues created after git revision `REV`
+  #new-from-rev: REV
+
+  ## Show only new issues created in git patch with set file path.
+  #new-from-patch: path/to/patch/file

README.md

@@ -88,7 +88,10 @@ After each command, we append a layer of changed files to the base image (if the
 
 ## Known Issues
 
-kaniko does not support building Windows containers.
+* kaniko does not support building Windows containers.
+* Running kaniko in any Docker image other than the official kaniko image is not supported (ie YMMV).
+  * This includes copying the kaniko executables from the official image into another image.
+* kaniko does not support the v1 Registry API ([Registry v1 API Deprecation](https://engineering.docker.com/2019/03/registry-v1-api-deprecation/))
 
 ## Demo
 
@@ -285,7 +288,7 @@ as a remote image destination:
 ### Caching
 
 #### Caching Layers
-kaniko currently can cache layers created by `RUN` commands in a remote repository.
+kaniko can cache layers created by `RUN` commands in a remote repository.
 Before executing a command, kaniko checks the cache for the layer.
 If it exists, kaniko will pull and extract the cached layer instead of executing the command.
 If not, kaniko will execute the command and then push the newly created layer to the cache.
@@ -296,7 +299,7 @@ If this flag isn't provided, a cached repo will be inferred from the `--destinat
 
 #### Caching Base Images
 
-kaniko can cache images in a local directory that can be volume mounted into the kaniko image.
+kaniko can cache images in a local directory that can be volume mounted into the kaniko pod.
 To do so, the cache must first be populated, as it is read-only. We provide a kaniko cache warming
 image at `gcr.io/kaniko-project/warmer`:
 
@@ -307,7 +310,7 @@ docker run -v $(pwd):/workspace gcr.io/kaniko-project/warmer:latest --cache-dir=
 `--image` can be specified for any number of desired images.
 This command will cache those images by digest in a local directory named `cache`.
 Once the cache is populated, caching is opted into with the same `--cache=true` flag as above.
-The location of the local cache is provided via the `--cache-dir` flag, defaulting at `/cache` as with the cache warmer.
+The location of the local cache is provided via the `--cache-dir` flag, defaulting to `/cache` as with the cache warmer.
 See the `examples` directory for how to use with kubernetes clusters and persistent cache volumes.
 
 ### Pushing to Different Registries
@@ -343,7 +346,7 @@ Run kaniko with the `config.json` inside `/kaniko/.docker/config.json`
 The Amazon ECR [credential helper](https://github.com/awslabs/amazon-ecr-credential-helper) is built in to the kaniko executor image.
 To configure credentials, you will need to do the following:
 
-1. Update the `credHelpers` section of [config.json](https://github.com/GoogleContainerTools/kaniko/blob/master/files/config.json) with the specific URI of your ECR registry:
+1. Update the `credHelpers` section of [config.json](https://github.com/awslabs/amazon-ecr-credential-helper#configuration) with the specific URI of your ECR registry:
 
   ```json
   {

hack/linter.sh

@@ -23,15 +23,4 @@ if ! [ -x "$(command -v golangci-lint)" ]; then
 	${DIR}/install_golint.sh -b $GOPATH/bin v1.9.3
 fi
 
-golangci-lint run \
+golangci-lint run
-	--no-config \
-	-E goconst \
-	-E goimports \
-	-E golint \
-	-E interfacer \
-	-E maligned \
-	-E misspell \
-	-E unconvert \
-	-E unparam \
-	-D errcheck \
-	-D gas

integration/dockerfiles/Dockerfile_test_add_dest_symlink_dir

@@ -0,0 +1,2 @@
+FROM phusion/baseimage:0.11
+ADD context/foo /etc/service/foo

integration/dockerfiles/Dockerfile_test_add_url_with_arg

@@ -0,0 +1,6 @@
+FROM busybox:1.31
+
+ARG REPO=kaniko
+ARG VERSION=v0.14.0
+
+ADD https://github.com/GoogleContainerTools/$REPO/archive/$VERSION.tar.gz /tmp/release.tar.gz

pkg/cache/cache.go

@@ -28,7 +28,7 @@ import (
 	"github.com/GoogleContainerTools/kaniko/pkg/config"
 	"github.com/GoogleContainerTools/kaniko/pkg/creds"
 	"github.com/google/go-containerregistry/pkg/name"
-	"github.com/google/go-containerregistry/pkg/v1"
+	v1 "github.com/google/go-containerregistry/pkg/v1"
 	"github.com/google/go-containerregistry/pkg/v1/remote"
 	"github.com/google/go-containerregistry/pkg/v1/tarball"
 	"github.com/pkg/errors"
@@ -124,7 +124,8 @@ func LocalSource(opts *config.CacheOptions, cacheKey string) (v1.Image, error) {
 
 	fi, err := os.Stat(path)
 	if err != nil {
-		return nil, errors.Wrap(err, "getting file info")
+		logrus.Debugf("No file found for cache key %v %v", cacheKey, err)
+		return nil, nil
 	}
 
 	// A stale cache is a bad cache

pkg/commands/add.go

@@ -141,3 +141,7 @@ func (a *AddCommand) FilesUsedFromContext(config *v1.Config, buildArgs *dockerfi
 func (a *AddCommand) MetadataOnly() bool {
 	return false
 }
+
+func (a *AddCommand) RequiresUnpackedFS() bool {
+	return true
+}

pkg/commands/commands.go

@@ -17,6 +17,7 @@ limitations under the License.
 package commands
 
 import (
+	"github.com/GoogleContainerTools/kaniko/pkg/constants"
 	"github.com/GoogleContainerTools/kaniko/pkg/dockerfile"
 	v1 "github.com/google/go-containerregistry/pkg/v1"
 	"github.com/moby/buildkit/frontend/dockerfile/instructions"
@@ -24,6 +25,12 @@ import (
 	"github.com/sirupsen/logrus"
 )
 
+var RootDir string
+
+func init() {
+	RootDir = constants.RootDir
+}
+
 type CurrentCacheKey func() (string, error)
 
 type DockerCommand interface {

pkg/commands/copy.go

@@ -66,6 +66,14 @@ func (c *CopyCommand) ExecuteCommand(config *v1.Config, buildArgs *dockerfile.Bu
 		if err != nil {
 			return err
 		}
+
+		// If the destination dir is a symlink we need to resolve the path and use
+		// that instead of the symlink path
+		destPath, err = resolveIfSymlink(destPath)
+		if err != nil {
+			return err
+		}
+
 		if fi.IsDir() {
 			if !filepath.IsAbs(dest) {
 				// we need to add '/' to the end to indicate the destination is a directory
@@ -163,7 +171,7 @@ type CachingCopyCommand struct {
 func (cr *CachingCopyCommand) ExecuteCommand(config *v1.Config, buildArgs *dockerfile.BuildArgs) error {
 	logrus.Infof("Found cached layer, extracting to filesystem")
 	var err error
-	cr.extractedFiles, err = util.GetFSFromImage(constants.RootDir, cr.img)
+	cr.extractedFiles, err = util.GetFSFromImage(RootDir, cr.img)
 	logrus.Infof("extractedFiles: %s", cr.extractedFiles)
 	if err != nil {
 		return errors.Wrap(err, "extracting fs from image")
@@ -178,3 +186,21 @@ func (cr *CachingCopyCommand) FilesToSnapshot() []string {
 func (cr *CachingCopyCommand) String() string {
 	return cr.cmd.String()
 }
+
+func resolveIfSymlink(destPath string) (string, error) {
+	baseDir := filepath.Dir(destPath)
+	if info, err := os.Lstat(baseDir); err == nil {
+		switch mode := info.Mode(); {
+		case mode&os.ModeSymlink != 0:
+			linkPath, err := os.Readlink(baseDir)
+			if err != nil {
+				return "", errors.Wrap(err, "error reading symlink")
+			}
+			absLinkPath := filepath.Join(filepath.Dir(baseDir), linkPath)
+			newPath := filepath.Join(absLinkPath, filepath.Base(destPath))
+			logrus.Tracef("Updating destination path from %v to %v due to symlink", destPath, newPath)
+			return newPath, nil
+		}
+	}
+	return destPath, nil
+}

pkg/commands/copy_test.go

@@ -16,6 +16,7 @@ limitations under the License.
 package commands
 
 import (
+	"fmt"
 	"io"
 	"io/ioutil"
 	"os"
@@ -165,3 +166,52 @@ func copySetUpBuildArgs() *dockerfile.BuildArgs {
 	buildArgs.AddArg("buildArg2", &d)
 	return buildArgs
 }
+
+func Test_resolveIfSymlink(t *testing.T) {
+	type testCase struct {
+		destPath     string
+		expectedPath string
+		err          error
+	}
+
+	tmpDir, err := ioutil.TempDir("", "copy-test")
+	if err != nil {
+		t.Error(err)
+	}
+
+	baseDir, err := ioutil.TempDir(tmpDir, "not-linked")
+	if err != nil {
+		t.Error(err)
+	}
+
+	path, err := ioutil.TempFile(baseDir, "foo.txt")
+	if err != nil {
+		t.Error(err)
+	}
+
+	thepath, err := filepath.Abs(filepath.Dir(path.Name()))
+	if err != nil {
+		t.Error(err)
+	}
+	cases := []testCase{{destPath: thepath, expectedPath: thepath, err: nil}}
+
+	baseDir = tmpDir
+	symLink := filepath.Join(baseDir, "symlink")
+	if err := os.Symlink(filepath.Base(thepath), symLink); err != nil {
+		t.Error(err)
+	}
+	cases = append(cases, testCase{filepath.Join(symLink, "foo.txt"), filepath.Join(thepath, "foo.txt"), nil})
+
+	for i, c := range cases {
+		t.Run(fmt.Sprintf("%d", i), func(t *testing.T) {
+			res, e := resolveIfSymlink(c.destPath)
+			if e != c.err {
+				t.Errorf("%s: expected %v but got %v", c.destPath, c.err, e)
+			}
+
+			if res != c.expectedPath {
+				t.Errorf("%s: expected %v but got %v", c.destPath, c.expectedPath, res)
+			}
+		})
+	}
+}

pkg/executor/build.go

@@ -23,7 +23,7 @@ import (
 	"strconv"
 	"time"
 
-	"github.com/otiai10/copy"
+	otiai10Cpy "github.com/otiai10/copy"
 
 	"github.com/google/go-containerregistry/pkg/v1/partial"
 
@@ -52,21 +52,32 @@ import (
 // This is the size of an empty tar in Go
 const emptyTarSize = 1024
 
+type cachePusher func(*config.KanikoOptions, string, string, string) error
+type snapShotter interface {
+	Init() error
+	TakeSnapshotFS() (string, error)
+	TakeSnapshot([]string) (string, error)
+}
+
 // stageBuilder contains all fields necessary to build one stage of a Dockerfile
 type stageBuilder struct {
-	stage           config.KanikoStage
+	stage               config.KanikoStage
-	image           v1.Image
+	image               v1.Image
-	cf              *v1.ConfigFile
+	cf                  *v1.ConfigFile
-	snapshotter     *snapshot.Snapshotter
+	snapshotter         snapShotter
-	baseImageDigest string
+	layerCache          cache.LayerCache
-	opts            *config.KanikoOptions
+	pushCache           cachePusher
-	cmds            []commands.DockerCommand
+	baseImageDigest     string
-	args            *dockerfile.BuildArgs
+	finalCacheKey       string
-	crossStageDeps  map[int][]string
+	opts                *config.KanikoOptions
+	cmds                []commands.DockerCommand
+	args                *dockerfile.BuildArgs
+	crossStageDeps      map[int][]string
+	digestToCacheKeyMap map[string]string
 }
 
 // newStageBuilder returns a new type stageBuilder which contains all the information required to build the stage
-func newStageBuilder(opts *config.KanikoOptions, stage config.KanikoStage, crossStageDeps map[int][]string) (*stageBuilder, error) {
+func newStageBuilder(opts *config.KanikoOptions, stage config.KanikoStage, crossStageDeps map[int][]string, dcm map[string]string) (*stageBuilder, error) {
 	sourceImage, err := util.RetrieveSourceImage(stage, opts)
 	if err != nil {
 		return nil, err
@@ -93,13 +104,18 @@ func newStageBuilder(opts *config.KanikoOptions, stage config.KanikoStage, cross
 		return nil, err
 	}
 	s := &stageBuilder{
-		stage:           stage,
+		stage:               stage,
-		image:           sourceImage,
+		image:               sourceImage,
-		cf:              imageConfig,
+		cf:                  imageConfig,
-		snapshotter:     snapshotter,
+		snapshotter:         snapshotter,
-		baseImageDigest: digest.String(),
+		baseImageDigest:     digest.String(),
-		opts:            opts,
+		opts:                opts,
-		crossStageDeps:  crossStageDeps,
+		crossStageDeps:      crossStageDeps,
+		digestToCacheKeyMap: dcm,
+		layerCache: &cache.RegistryCache{
+			Opts: opts,
+		},
+		pushCache: pushLayerToCache,
 	}
 
 	for _, cmd := range s.stage.Commands {
@@ -135,10 +151,7 @@ func (s *stageBuilder) optimize(compositeKey CompositeCache, cfg v1.Config) erro
 		return nil
 	}
 
-	layerCache := &cache.RegistryCache{
+	stopCache := false
-		Opts: s.opts,
-	}
-
 	// Possibly replace commands with their cached implementations.
 	// We walk through all the commands, running any commands that only operate on metadata.
 	// We throw the metadata away after, but we need it to properly track command dependencies
@@ -151,25 +164,27 @@ func (s *stageBuilder) optimize(compositeKey CompositeCache, cfg v1.Config) erro
 		// If the command uses files from the context, add them.
 		files, err := command.FilesUsedFromContext(&cfg, s.args)
 		if err != nil {
-			return err
+			return errors.Wrap(err, "failed to get files used from context")
 		}
 		for _, f := range files {
 			if err := compositeKey.AddPath(f); err != nil {
-				return err
+				return errors.Wrap(err, "failed to add path to composite key")
 			}
 		}
 
 		ck, err := compositeKey.Hash()
 		if err != nil {
-			return err
+			return errors.Wrap(err, "failed to hash composite key")
 		}
-		if command.ShouldCacheOutput() {
+		s.finalCacheKey = ck
-			img, err := layerCache.RetrieveLayer(ck)
+		if command.ShouldCacheOutput() && !stopCache {
+			img, err := s.layerCache.RetrieveLayer(ck)
 			if err != nil {
 				logrus.Debugf("Failed to retrieve layer: %s", err)
 				logrus.Infof("No cached layer found for cmd %s", command.String())
 				logrus.Debugf("Key missing was: %s", compositeKey.Key())
-				break
+				stopCache = true
+				continue
 			}
 
 			if cacheCmd := command.CacheCommand(img); cacheCmd != nil {
@@ -190,12 +205,17 @@ func (s *stageBuilder) optimize(compositeKey CompositeCache, cfg v1.Config) erro
 
 func (s *stageBuilder) build() error {
 	// Set the initial cache key to be the base image digest, the build args and the SrcContext.
-	compositeKey := NewCompositeCache(s.baseImageDigest)
+	var compositeKey *CompositeCache
+	if cacheKey, ok := s.digestToCacheKeyMap[s.baseImageDigest]; ok {
+		compositeKey = NewCompositeCache(cacheKey)
+	} else {
+		compositeKey = NewCompositeCache(s.baseImageDigest)
+	}
 	compositeKey.AddKey(s.opts.BuildArgs...)
 
 	// Apply optimizations to the instructions.
 	if err := s.optimize(*compositeKey, s.cf.Config); err != nil {
-		return err
+		return errors.Wrap(err, "failed to optimize instructions")
 	}
 
 	// Unpack file system to root if we need to.
@@ -214,14 +234,14 @@ func (s *stageBuilder) build() error {
 	if shouldUnpack {
 		t := timing.Start("FS Unpacking")
 		if _, err := util.GetFSFromImage(constants.RootDir, s.image); err != nil {
-			return err
+			return errors.Wrap(err, "failed to get filesystem from image")
 		}
 		timing.DefaultRun.Stop(t)
 	} else {
 		logrus.Info("Skipping unpacking as no commands require it.")
 	}
 	if err := util.DetectFilesystemWhitelist(constants.WhitelistPath); err != nil {
-		return err
+		return errors.Wrap(err, "failed to check filesystem whitelist")
 	}
 	// Take initial snapshot
 	t := timing.Start("Initial FS snapshot")
@@ -242,17 +262,17 @@ func (s *stageBuilder) build() error {
 		// If the command uses files from the context, add them.
 		files, err := command.FilesUsedFromContext(&s.cf.Config, s.args)
 		if err != nil {
-			return err
+			return errors.Wrap(err, "failed to get files used from context")
 		}
 		for _, f := range files {
 			if err := compositeKey.AddPath(f); err != nil {
-				return err
+				return errors.Wrap(err, fmt.Sprintf("failed to add path to composite key %v", f))
 			}
 		}
 		logrus.Info(command.String())
 
 		if err := command.ExecuteCommand(&s.cf.Config, s.args); err != nil {
-			return err
+			return errors.Wrap(err, "failed to execute command")
 		}
 		files = command.FilesToSnapshot()
 		timing.DefaultRun.Stop(t)
@@ -263,21 +283,21 @@ func (s *stageBuilder) build() error {
 
 		tarPath, err := s.takeSnapshot(files)
 		if err != nil {
-			return err
+			return errors.Wrap(err, "failed to take snapshot")
 		}
 
 		ck, err := compositeKey.Hash()
 		if err != nil {
-			return err
+			return errors.Wrap(err, "failed to hash composite key")
 		}
 		// Push layer to cache (in parallel) now along with new config file
 		if s.opts.Cache && command.ShouldCacheOutput() {
 			cacheGroup.Go(func() error {
-				return pushLayerToCache(s.opts, ck, tarPath, command.String())
+				return s.pushCache(s.opts, ck, tarPath, command.String())
 			})
 		}
 		if err := s.saveSnapshotToImage(command.String(), tarPath); err != nil {
-			return err
+			return errors.Wrap(err, "failed to save snapshot to image")
 		}
 	}
 	if err := cacheGroup.Wait(); err != nil {
@@ -333,7 +353,7 @@ func (s *stageBuilder) saveSnapshotToImage(createdBy string, tarPath string) err
 	}
 	fi, err := os.Stat(tarPath)
 	if err != nil {
-		return err
+		return errors.Wrap(err, "tar file path does not exist")
 	}
 	if fi.Size() <= emptyTarSize {
 		logrus.Info("No files were changed, appending empty layer to config. No layer added to image.")
@@ -422,6 +442,7 @@ func CalculateDependencies(opts *config.KanikoOptions) (map[int][]string, error)
 // DoBuild executes building the Dockerfile
 func DoBuild(opts *config.KanikoOptions) (v1.Image, error) {
 	t := timing.Start("Total Build Time")
+	digestToCacheKeyMap := make(map[string]string)
 	// Parse dockerfile and unpack base image to root
 	stages, err := dockerfile.Stages(opts)
 	if err != nil {
@@ -442,7 +463,7 @@ func DoBuild(opts *config.KanikoOptions) (v1.Image, error) {
 	logrus.Infof("Built cross stage deps: %v", crossStageDependencies)
 
 	for index, stage := range stages {
-		sb, err := newStageBuilder(opts, stage, crossStageDependencies)
+		sb, err := newStageBuilder(opts, stage, crossStageDependencies, digestToCacheKeyMap)
 		if err != nil {
 			return nil, err
 		}
@@ -454,6 +475,11 @@ func DoBuild(opts *config.KanikoOptions) (v1.Image, error) {
 		if err != nil {
 			return nil, err
 		}
+		d, err := sourceImage.Digest()
+		if err != nil {
+			return nil, err
+		}
+		digestToCacheKeyMap[d.String()] = sb.finalCacheKey
 		if stage.Final {
 			sourceImage, err = mutate.CreatedAt(sourceImage, v1.Time{Time: time.Now()})
 			if err != nil {
@@ -489,7 +515,7 @@ func DoBuild(opts *config.KanikoOptions) (v1.Image, error) {
 		}
 		for _, p := range filesToSave {
 			logrus.Infof("Saving file %s for later use.", p)
-			copy.Copy(p, filepath.Join(dstDir, p))
+			otiai10Cpy.Copy(p, filepath.Join(dstDir, p))
 		}
 
 		// Delete the filesystem

pkg/executor/build_test.go

@@ -17,6 +17,9 @@ limitations under the License.
 package executor
 
 import (
+	"archive/tar"
+	"bytes"
+	"fmt"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -24,6 +27,7 @@ import (
 	"sort"
 	"testing"
 
+	"github.com/GoogleContainerTools/kaniko/pkg/commands"
 	"github.com/GoogleContainerTools/kaniko/pkg/config"
 	"github.com/GoogleContainerTools/kaniko/pkg/dockerfile"
 	"github.com/GoogleContainerTools/kaniko/testutil"
@@ -32,6 +36,7 @@ import (
 	"github.com/google/go-containerregistry/pkg/v1/empty"
 	"github.com/google/go-containerregistry/pkg/v1/mutate"
 	"github.com/moby/buildkit/frontend/dockerfile/instructions"
+	"github.com/sirupsen/logrus"
 )
 
 func Test_reviewConfig(t *testing.T) {
@@ -462,3 +467,455 @@ func TestInitializeConfig(t *testing.T) {
 		testutil.CheckDeepEqual(t, tt.expected, actual.Config)
 	}
 }
+
+func Test_stageBuilder_optimize(t *testing.T) {
+	testCases := []struct {
+		opts     *config.KanikoOptions
+		retrieve bool
+		name     string
+	}{
+		{
+			name: "cache enabled and layer not present in cache",
+			opts: &config.KanikoOptions{Cache: true},
+		},
+		{
+			name:     "cache enabled and layer present in cache",
+			opts:     &config.KanikoOptions{Cache: true},
+			retrieve: true,
+		},
+		{
+			name: "cache disabled and layer not present in cache",
+			opts: &config.KanikoOptions{Cache: false},
+		},
+		{
+			name:     "cache disabled and layer present in cache",
+			opts:     &config.KanikoOptions{Cache: false},
+			retrieve: true,
+		},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			cf := &v1.ConfigFile{}
+			snap := fakeSnapShotter{}
+			lc := &fakeLayerCache{retrieve: tc.retrieve}
+			sb := &stageBuilder{opts: tc.opts, cf: cf, snapshotter: snap, layerCache: lc}
+			ck := CompositeCache{}
+			file, err := ioutil.TempFile("", "foo")
+			if err != nil {
+				t.Error(err)
+			}
+			command := MockDockerCommand{
+				contextFiles: []string{file.Name()},
+				cacheCommand: MockCachedDockerCommand{},
+			}
+			sb.cmds = []commands.DockerCommand{command}
+			err = sb.optimize(ck, cf.Config)
+			if err != nil {
+				t.Errorf("Expected error to be nil but was %v", err)
+			}
+
+		})
+	}
+}
+
+func Test_stageBuilder_build(t *testing.T) {
+	type testcase struct {
+		description       string
+		opts              *config.KanikoOptions
+		layerCache        *fakeLayerCache
+		expectedCacheKeys []string
+		pushedCacheKeys   []string
+		commands          []commands.DockerCommand
+		fileName          string
+		rootDir           string
+		image             v1.Image
+		config            *v1.ConfigFile
+	}
+
+	testCases := []testcase{
+		func() testcase {
+			dir, files := tempDirAndFile(t)
+			file := files[0]
+			filePath := filepath.Join(dir, file)
+			ch := NewCompositeCache("", "meow")
+
+			ch.AddPath(filePath)
+			hash, err := ch.Hash()
+			if err != nil {
+				t.Errorf("couldn't create hash %v", err)
+			}
+			command := MockDockerCommand{
+				contextFiles: []string{filePath},
+				cacheCommand: MockCachedDockerCommand{
+					contextFiles: []string{filePath},
+				},
+			}
+
+			destDir, err := ioutil.TempDir("", "baz")
+			if err != nil {
+				t.Errorf("could not create temp dir %v", err)
+			}
+			return testcase{
+				description:       "fake command cache enabled but key not in cache",
+				config:            &v1.ConfigFile{Config: v1.Config{WorkingDir: destDir}},
+				opts:              &config.KanikoOptions{Cache: true},
+				expectedCacheKeys: []string{hash},
+				pushedCacheKeys:   []string{hash},
+				commands:          []commands.DockerCommand{command},
+				rootDir:           dir,
+			}
+		}(),
+		func() testcase {
+			dir, files := tempDirAndFile(t)
+			file := files[0]
+			filePath := filepath.Join(dir, file)
+			ch := NewCompositeCache("", "meow")
+
+			ch.AddPath(filePath)
+			hash, err := ch.Hash()
+			if err != nil {
+				t.Errorf("couldn't create hash %v", err)
+			}
+			command := MockDockerCommand{
+				contextFiles: []string{filePath},
+				cacheCommand: MockCachedDockerCommand{
+					contextFiles: []string{filePath},
+				},
+			}
+
+			destDir, err := ioutil.TempDir("", "baz")
+			if err != nil {
+				t.Errorf("could not create temp dir %v", err)
+			}
+			return testcase{
+				description: "fake command cache enabled and key in cache",
+				opts:        &config.KanikoOptions{Cache: true},
+				config:      &v1.ConfigFile{Config: v1.Config{WorkingDir: destDir}},
+				layerCache: &fakeLayerCache{
+					retrieve: true,
+				},
+				expectedCacheKeys: []string{hash},
+				pushedCacheKeys:   []string{},
+				commands:          []commands.DockerCommand{command},
+				rootDir:           dir,
+			}
+		}(),
+		{
+			description: "fake command cache disabled and key not in cache",
+			opts:        &config.KanikoOptions{Cache: false},
+		},
+		{
+			description: "fake command cache disabled and key in cache",
+			opts:        &config.KanikoOptions{Cache: false},
+			layerCache: &fakeLayerCache{
+				retrieve: true,
+			},
+		},
+		func() testcase {
+			dir, filenames := tempDirAndFile(t)
+			filename := filenames[0]
+			filepath := filepath.Join(dir, filename)
+
+			tarContent := generateTar(t, dir, filename)
+
+			ch := NewCompositeCache("", "")
+			ch.AddPath(filepath)
+			logrus.SetLevel(logrus.DebugLevel)
+			hash, err := ch.Hash()
+			if err != nil {
+				t.Errorf("couldn't create hash %v", err)
+			}
+			copyCommandCacheKey := hash
+			return testcase{
+				description: "copy command cache enabled and key in cache",
+				opts:        &config.KanikoOptions{Cache: true},
+				layerCache: &fakeLayerCache{
+					retrieve: true,
+					img: fakeImage{
+						ImageLayers: []v1.Layer{
+							fakeLayer{
+								TarContent: tarContent,
+							},
+						},
+					},
+				},
+				rootDir:           dir,
+				expectedCacheKeys: []string{copyCommandCacheKey},
+				// CachingCopyCommand is not pushed to the cache
+				pushedCacheKeys: []string{},
+				commands: getCommands(dir, []instructions.Command{
+					&instructions.CopyCommand{
+						SourcesAndDest: []string{
+							filename, "foo.txt",
+						},
+					},
+				}),
+				fileName: filename,
+			}
+		}(),
+		func() testcase {
+			dir, filenames := tempDirAndFile(t)
+			filename := filenames[0]
+			tarContent := []byte{}
+			destDir, err := ioutil.TempDir("", "baz")
+			if err != nil {
+				t.Errorf("could not create temp dir %v", err)
+			}
+			filePath := filepath.Join(dir, filename)
+			ch := NewCompositeCache("", "")
+			ch.AddPath(filePath)
+			logrus.SetLevel(logrus.DebugLevel)
+			hash, err := ch.Hash()
+			if err != nil {
+				t.Errorf("couldn't create hash %v", err)
+			}
+			return testcase{
+				description: "copy command cache enabled and key is not in cache",
+				opts:        &config.KanikoOptions{Cache: true},
+				config:      &v1.ConfigFile{Config: v1.Config{WorkingDir: destDir}},
+				layerCache:  &fakeLayerCache{},
+				image: fakeImage{
+					ImageLayers: []v1.Layer{
+						fakeLayer{
+							TarContent: tarContent,
+						},
+					},
+				},
+				rootDir:           dir,
+				expectedCacheKeys: []string{hash},
+				pushedCacheKeys:   []string{hash},
+				commands: getCommands(dir, []instructions.Command{
+					&instructions.CopyCommand{
+						SourcesAndDest: []string{
+							filename, "foo.txt",
+						},
+					},
+				}),
+				fileName: filename,
+			}
+		}(),
+		func() testcase {
+			dir, filenames := tempDirAndFile(t)
+			filename := filenames[0]
+			tarContent := generateTar(t, filename)
+			destDir, err := ioutil.TempDir("", "baz")
+			if err != nil {
+				t.Errorf("could not create temp dir %v", err)
+			}
+			filePath := filepath.Join(dir, filename)
+			ch := NewCompositeCache("", fmt.Sprintf("COPY %s foo.txt", filename))
+			ch.AddPath(filePath)
+			logrus.SetLevel(logrus.DebugLevel)
+			logrus.Infof("test composite key %v", ch)
+			hash1, err := ch.Hash()
+			if err != nil {
+				t.Errorf("couldn't create hash %v", err)
+			}
+			ch.AddKey(fmt.Sprintf("COPY %s bar.txt", filename))
+			ch.AddPath(filePath)
+			logrus.Infof("test composite key %v", ch)
+			hash2, err := ch.Hash()
+			if err != nil {
+				t.Errorf("couldn't create hash %v", err)
+			}
+			ch = NewCompositeCache("", fmt.Sprintf("COPY %s foo.txt", filename))
+			ch.AddKey(fmt.Sprintf("COPY %s bar.txt", filename))
+			ch.AddPath(filePath)
+			logrus.Infof("test composite key %v", ch)
+			hash3, err := ch.Hash()
+			if err != nil {
+				t.Errorf("couldn't create hash %v", err)
+			}
+			image := fakeImage{
+				ImageLayers: []v1.Layer{
+					fakeLayer{
+						TarContent: tarContent,
+					},
+				},
+			}
+
+			dockerFile := fmt.Sprintf(`
+FROM ubuntu:16.04
+COPY %s foo.txt
+COPY %s bar.txt
+`, filename, filename)
+			f, _ := ioutil.TempFile("", "")
+			ioutil.WriteFile(f.Name(), []byte(dockerFile), 0755)
+			opts := &config.KanikoOptions{
+				DockerfilePath: f.Name(),
+			}
+
+			stages, err := dockerfile.Stages(opts)
+			if err != nil {
+				t.Errorf("could not parse test dockerfile")
+			}
+			stage := stages[0]
+			cmds := stage.Commands
+			return testcase{
+				description: "cached copy command followed by uncached copy command result in different read and write hashes",
+				opts:        &config.KanikoOptions{Cache: true},
+				rootDir:     dir,
+				config:      &v1.ConfigFile{Config: v1.Config{WorkingDir: destDir}},
+				layerCache: &fakeLayerCache{
+					keySequence: []string{hash1},
+					img:         image,
+				},
+				image: image,
+				// hash1 is the read cachekey for the first layer
+				// hash2 is the read cachekey for the second layer
+				expectedCacheKeys: []string{hash1, hash2},
+				// Due to CachingCopyCommand and CopyCommand returning different values the write cache key for the second copy command will never match the read cache key
+				// hash3 is the cachekey used to write to the cache for layer 2
+				pushedCacheKeys: []string{hash3},
+				commands:        getCommands(dir, cmds),
+			}
+		}(),
+	}
+	for _, tc := range testCases {
+		t.Run(tc.description, func(t *testing.T) {
+			var fileName string
+			if tc.commands == nil {
+				file, err := ioutil.TempFile("", "foo")
+				if err != nil {
+					t.Error(err)
+				}
+				command := MockDockerCommand{
+					contextFiles: []string{file.Name()},
+					cacheCommand: MockCachedDockerCommand{
+						contextFiles: []string{file.Name()},
+					},
+				}
+				tc.commands = []commands.DockerCommand{command}
+				fileName = file.Name()
+			} else {
+				fileName = tc.fileName
+			}
+
+			cf := tc.config
+			if cf == nil {
+				cf = &v1.ConfigFile{
+					Config: v1.Config{
+						Env: make([]string, 0),
+					},
+				}
+			}
+
+			snap := fakeSnapShotter{file: fileName}
+			lc := tc.layerCache
+			if lc == nil {
+				lc = &fakeLayerCache{}
+			}
+			keys := []string{}
+			sb := &stageBuilder{
+				args:        &dockerfile.BuildArgs{}, //required or code will panic
+				image:       tc.image,
+				opts:        tc.opts,
+				cf:          cf,
+				snapshotter: snap,
+				layerCache:  lc,
+				pushCache: func(_ *config.KanikoOptions, cacheKey, _, _ string) error {
+					keys = append(keys, cacheKey)
+					return nil
+				},
+			}
+			sb.cmds = tc.commands
+			tmp := commands.RootDir
+			if tc.rootDir != "" {
+				commands.RootDir = tc.rootDir
+			}
+			err := sb.build()
+			if err != nil {
+				t.Errorf("Expected error to be nil but was %v", err)
+			}
+
+			assertCacheKeys(t, tc.expectedCacheKeys, lc.receivedKeys, "receive")
+			assertCacheKeys(t, tc.pushedCacheKeys, keys, "push")
+
+			commands.RootDir = tmp
+
+		})
+	}
+}
+
+func assertCacheKeys(t *testing.T, expectedCacheKeys, actualCacheKeys []string, description string) {
+	if len(expectedCacheKeys) != len(actualCacheKeys) {
+		t.Errorf("expected to %v %v keys but was %v", description, len(expectedCacheKeys), len(actualCacheKeys))
+	}
+
+	sort.Slice(expectedCacheKeys, func(x, y int) bool {
+		return expectedCacheKeys[x] > expectedCacheKeys[y]
+	})
+	sort.Slice(actualCacheKeys, func(x, y int) bool {
+		return actualCacheKeys[x] > actualCacheKeys[y]
+	})
+	for i, key := range expectedCacheKeys {
+		if key != actualCacheKeys[i] {
+			t.Errorf("expected to %v keys %d to be %v but was %v %v", description, i, key, actualCacheKeys[i], actualCacheKeys)
+		}
+	}
+}
+
+func getCommands(dir string, cmds []instructions.Command) []commands.DockerCommand {
+	outCommands := make([]commands.DockerCommand, 0)
+	for _, c := range cmds {
+		cmd, err := commands.GetCommand(
+			c,
+			dir,
+		)
+		if err != nil {
+			panic(err)
+		}
+		outCommands = append(outCommands, cmd)
+	}
+	return outCommands
+
+}
+
+func tempDirAndFile(t *testing.T) (string, []string) {
+	filenames := []string{"bar.txt"}
+
+	dir, err := ioutil.TempDir("", "foo")
+	if err != nil {
+		t.Errorf("could not create temp dir %v", err)
+	}
+	for _, filename := range filenames {
+		filepath := filepath.Join(dir, filename)
+		err = ioutil.WriteFile(filepath, []byte(`meow`), 0777)
+		if err != nil {
+			t.Errorf("could not create temp file %v", err)
+		}
+	}
+
+	return dir, filenames
+}
+func generateTar(t *testing.T, dir string, fileNames ...string) []byte {
+	buf := bytes.NewBuffer([]byte{})
+	writer := tar.NewWriter(buf)
+	defer writer.Close()
+
+	for _, filename := range fileNames {
+		filePath := filepath.Join(dir, filename)
+		info, err := os.Stat(filePath)
+		if err != nil {
+			t.Errorf("could not get file info for temp file %v", err)
+		}
+		hdr, err := tar.FileInfoHeader(info, filename)
+		if err != nil {
+			t.Errorf("could not get tar header for temp file %v", err)
+		}
+
+		if err := writer.WriteHeader(hdr); err != nil {
+			t.Errorf("could not write tar header %v", err)
+		}
+
+		content, err := ioutil.ReadFile(filePath)
+		if err != nil {
+			t.Errorf("could not read tempfile %v", err)
+		}
+
+		if _, err := writer.Write(content); err != nil {
+			t.Errorf("could not write file contents to tar")
+		}
+	}
+	return buf.Bytes()
+}

pkg/executor/composite_cache_test.go

@@ -0,0 +1,137 @@
+/*
+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 executor
+
+import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"reflect"
+	"testing"
+)
+
+func Test_NewCompositeCache(t *testing.T) {
+	r := NewCompositeCache()
+	if reflect.TypeOf(r).String() != "*executor.CompositeCache" {
+		t.Errorf("expected return to be *executor.CompositeCache but was %v", reflect.TypeOf(r).String())
+	}
+}
+
+func Test_CompositeCache_AddKey(t *testing.T) {
+	keys := []string{
+		"meow",
+		"purr",
+	}
+	r := NewCompositeCache()
+	r.AddKey(keys...)
+	if len(r.keys) != 2 {
+		t.Errorf("expected keys to have length 2 but was %v", len(r.keys))
+	}
+}
+
+func Test_CompositeCache_Key(t *testing.T) {
+	r := NewCompositeCache("meow", "purr")
+	k := r.Key()
+	if k != "meow-purr" {
+		t.Errorf("expected result to equal meow-purr but was %v", k)
+	}
+}
+
+func Test_CompositeCache_Hash(t *testing.T) {
+	r := NewCompositeCache("meow", "purr")
+	h, err := r.Hash()
+	if err != nil {
+		t.Errorf("expected error to be nil but was %v", err)
+	}
+
+	expectedHash := "b4fd5a11af812a11a79d794007c842794cc668c8e7ebaba6d1e6d021b8e06c71"
+	if h != expectedHash {
+		t.Errorf("expected result to equal %v but was %v", expectedHash, h)
+	}
+}
+
+func Test_CompositeCache_AddPath_dir(t *testing.T) {
+	tmpDir, err := ioutil.TempDir("/tmp", "foo")
+	if err != nil {
+		t.Errorf("got error setting up test %v", err)
+	}
+
+	content := `meow meow meow`
+	if err := ioutil.WriteFile(filepath.Join(tmpDir, "foo.txt"), []byte(content), 0777); err != nil {
+		t.Errorf("got error writing temp file %v", err)
+	}
+
+	fn := func() string {
+		r := NewCompositeCache()
+		if err := r.AddPath(tmpDir); err != nil {
+			t.Errorf("expected error to be nil but was %v", err)
+		}
+
+		if len(r.keys) != 1 {
+			t.Errorf("expected len of keys to be 1 but was %v", len(r.keys))
+		}
+		hash, err := r.Hash()
+		if err != nil {
+			t.Errorf("couldnt generate hash from test cache")
+		}
+		return hash
+	}
+
+	hash1 := fn()
+	hash2 := fn()
+	if hash1 != hash2 {
+		t.Errorf("expected hash %v to equal hash %v", hash1, hash2)
+	}
+}
+func Test_CompositeCache_AddPath_file(t *testing.T) {
+	tmpfile, err := ioutil.TempFile("/tmp", "foo.txt")
+	if err != nil {
+		t.Errorf("got error setting up test %v", err)
+	}
+	defer os.Remove(tmpfile.Name()) // clean up
+
+	content := `meow meow meow`
+	if _, err := tmpfile.Write([]byte(content)); err != nil {
+		t.Errorf("got error writing temp file %v", err)
+	}
+	if err := tmpfile.Close(); err != nil {
+		t.Errorf("got error closing temp file %v", err)
+	}
+
+	p := tmpfile.Name()
+	fn := func() string {
+		r := NewCompositeCache()
+		if err := r.AddPath(p); err != nil {
+			t.Errorf("expected error to be nil but was %v", err)
+		}
+
+		if len(r.keys) != 1 {
+			t.Errorf("expected len of keys to be 1 but was %v", len(r.keys))
+		}
+		hash, err := r.Hash()
+		if err != nil {
+			t.Errorf("couldnt generate hash from test cache")
+		}
+		return hash
+	}
+
+	hash1 := fn()
+	hash2 := fn()
+	if hash1 != hash2 {
+		t.Errorf("expected hash %v to equal hash %v", hash1, hash2)
+	}
+}

pkg/executor/fakes.go

@@ -0,0 +1,184 @@
+/*
+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.
+*/
+
+// for use in tests
+package executor
+
+import (
+	"bytes"
+	"errors"
+	"io"
+	"io/ioutil"
+
+	"github.com/GoogleContainerTools/kaniko/pkg/commands"
+	"github.com/GoogleContainerTools/kaniko/pkg/dockerfile"
+	v1 "github.com/google/go-containerregistry/pkg/v1"
+	"github.com/google/go-containerregistry/pkg/v1/types"
+)
+
+type fakeSnapShotter struct {
+	file    string
+	tarPath string
+}
+
+func (f fakeSnapShotter) Init() error { return nil }
+func (f fakeSnapShotter) TakeSnapshotFS() (string, error) {
+	return f.tarPath, nil
+}
+func (f fakeSnapShotter) TakeSnapshot(_ []string) (string, error) {
+	return f.tarPath, nil
+}
+
+type MockDockerCommand struct {
+	contextFiles []string
+	cacheCommand commands.DockerCommand
+}
+
+func (m MockDockerCommand) ExecuteCommand(c *v1.Config, args *dockerfile.BuildArgs) error { return nil }
+func (m MockDockerCommand) String() string {
+	return "meow"
+}
+func (m MockDockerCommand) FilesToSnapshot() []string {
+	return []string{"meow-snapshot-no-cache"}
+}
+func (m MockDockerCommand) CacheCommand(image v1.Image) commands.DockerCommand {
+	return m.cacheCommand
+}
+func (m MockDockerCommand) FilesUsedFromContext(c *v1.Config, args *dockerfile.BuildArgs) ([]string, error) {
+	return m.contextFiles, nil
+}
+func (m MockDockerCommand) MetadataOnly() bool {
+	return false
+}
+func (m MockDockerCommand) RequiresUnpackedFS() bool {
+	return false
+}
+func (m MockDockerCommand) ShouldCacheOutput() bool {
+	return true
+}
+
+type MockCachedDockerCommand struct {
+	contextFiles []string
+}
+
+func (m MockCachedDockerCommand) ExecuteCommand(c *v1.Config, args *dockerfile.BuildArgs) error {
+	return nil
+}
+func (m MockCachedDockerCommand) String() string {
+	return "meow"
+}
+func (m MockCachedDockerCommand) FilesToSnapshot() []string {
+	return []string{"meow-snapshot"}
+}
+func (m MockCachedDockerCommand) CacheCommand(image v1.Image) commands.DockerCommand {
+	return nil
+}
+func (m MockCachedDockerCommand) FilesUsedFromContext(c *v1.Config, args *dockerfile.BuildArgs) ([]string, error) {
+	return m.contextFiles, nil
+}
+func (m MockCachedDockerCommand) MetadataOnly() bool {
+	return false
+}
+func (m MockCachedDockerCommand) RequiresUnpackedFS() bool {
+	return false
+}
+func (m MockCachedDockerCommand) ShouldCacheOutput() bool {
+	return false
+}
+
+type fakeLayerCache struct {
+	retrieve     bool
+	receivedKeys []string
+	img          v1.Image
+	keySequence  []string
+}
+
+func (f *fakeLayerCache) RetrieveLayer(key string) (v1.Image, error) {
+	f.receivedKeys = append(f.receivedKeys, key)
+	if len(f.keySequence) > 0 {
+		if f.keySequence[0] == key {
+			f.keySequence = f.keySequence[1:]
+			return f.img, nil
+		}
+		return f.img, errors.New("could not find layer")
+	}
+
+	if !f.retrieve {
+		return nil, errors.New("could not find layer")
+	}
+	return f.img, nil
+}
+
+type fakeLayer struct {
+	TarContent []byte
+}
+
+func (f fakeLayer) Digest() (v1.Hash, error) {
+	return v1.Hash{}, nil
+}
+func (f fakeLayer) DiffID() (v1.Hash, error) {
+	return v1.Hash{}, nil
+}
+func (f fakeLayer) Compressed() (io.ReadCloser, error) {
+	return nil, nil
+}
+func (f fakeLayer) Uncompressed() (io.ReadCloser, error) {
+	return ioutil.NopCloser(bytes.NewReader(f.TarContent)), nil
+}
+func (f fakeLayer) Size() (int64, error) {
+	return 0, nil
+}
+func (f fakeLayer) MediaType() (types.MediaType, error) {
+	return "", nil
+}
+
+type fakeImage struct {
+	ImageLayers []v1.Layer
+}
+
+func (f fakeImage) Layers() ([]v1.Layer, error) {
+	return f.ImageLayers, nil
+}
+func (f fakeImage) MediaType() (types.MediaType, error) {
+	return "", nil
+}
+func (f fakeImage) Size() (int64, error) {
+	return 0, nil
+}
+func (f fakeImage) ConfigName() (v1.Hash, error) {
+	return v1.Hash{}, nil
+}
+func (f fakeImage) ConfigFile() (*v1.ConfigFile, error) {
+	return &v1.ConfigFile{}, nil
+}
+func (f fakeImage) RawConfigFile() ([]byte, error) {
+	return []byte{}, nil
+}
+func (f fakeImage) Digest() (v1.Hash, error) {
+	return v1.Hash{}, nil
+}
+func (f fakeImage) Manifest() (*v1.Manifest, error) {
+	return &v1.Manifest{}, nil
+}
+func (f fakeImage) RawManifest() ([]byte, error) {
+	return []byte{}, nil
+}
+func (f fakeImage) LayerByDigest(v1.Hash) (v1.Layer, error) {
+	return fakeLayer{}, nil
+}
+func (f fakeImage) LayerByDiffID(v1.Hash) (v1.Layer, error) {
+	return fakeLayer{}, nil
+}

pkg/snapshot/snapshot.go

@@ -176,7 +176,7 @@ func (s *Snapshotter) scanFullFilesystem() ([]string, []string, error) {
 		// Only add changed files.
 		fileChanged, err := s.l.CheckFileChange(path)
 		if err != nil {
-			return nil, nil, err
+			return nil, nil, fmt.Errorf("could not check if file has changed %s %s", path, err)
 		}
 		if fileChanged {
 			logrus.Debugf("Adding %s to layer, because it was changed.", path)

pkg/util/command_util.go

@@ -17,6 +17,7 @@ limitations under the License.
 package util
 
 import (
+	"fmt"
 	"net/http"
 	"net/url"
 	"os"
@@ -25,7 +26,7 @@ import (
 	"strings"
 
 	"github.com/GoogleContainerTools/kaniko/pkg/constants"
-	"github.com/google/go-containerregistry/pkg/v1"
+	v1 "github.com/google/go-containerregistry/pkg/v1"
 	"github.com/moby/buildkit/frontend/dockerfile/instructions"
 	"github.com/moby/buildkit/frontend/dockerfile/parser"
 	"github.com/moby/buildkit/frontend/dockerfile/shell"
@@ -77,13 +78,16 @@ func ResolveEnvAndWildcards(sd instructions.SourcesAndDest, buildcontext string,
 	// First, resolve any environment replacement
 	resolvedEnvs, err := ResolveEnvironmentReplacementList(sd, envs, true)
 	if err != nil {
-		return nil, "", err
+		return nil, "", errors.Wrap(err, "failed to resolve environment")
+	}
+	if len(resolvedEnvs) == 0 {
+		return nil, "", errors.New("resolved envs is empty")
 	}
 	dest := resolvedEnvs[len(resolvedEnvs)-1]
 	// Resolve wildcards and get a list of resolved sources
 	srcs, err := ResolveSources(resolvedEnvs[0:len(resolvedEnvs)-1], buildcontext)
 	if err != nil {
-		return nil, "", err
+		return nil, "", errors.Wrap(err, "failed to resolve sources")
 	}
 	err = IsSrcsValid(sd, srcs, buildcontext)
 	return srcs, dest, err
@@ -219,9 +223,10 @@ func IsSrcsValid(srcsAndDest instructions.SourcesAndDest, resolvedSources []stri
 		if IsSrcRemoteFileURL(resolvedSources[0]) {
 			return nil
 		}
-		fi, err := os.Lstat(filepath.Join(root, resolvedSources[0]))
+		path := filepath.Join(root, resolvedSources[0])
+		fi, err := os.Lstat(path)
 		if err != nil {
-			return err
+			return errors.Wrap(err, fmt.Sprintf("failed to get fileinfo for %v", path))
 		}
 		if fi.IsDir() {
 			return nil
@@ -237,7 +242,7 @@ func IsSrcsValid(srcsAndDest instructions.SourcesAndDest, resolvedSources []stri
 		src = filepath.Clean(src)
 		files, err := RelativeFiles(src, root)
 		if err != nil {
-			return err
+			return errors.Wrap(err, "failed to get relative files")
 		}
 		for _, file := range files {
 			if excludeFile(file, root) {

pkg/util/fs_util.go

@@ -424,11 +424,17 @@ func FilepathExists(path string) bool {
 func CreateFile(path string, reader io.Reader, perm os.FileMode, uid uint32, gid uint32) error {
 	// Create directory path if it doesn't exist
 	baseDir := filepath.Dir(path)
-	if _, err := os.Lstat(baseDir); os.IsNotExist(err) {
+	if info, err := os.Lstat(baseDir); os.IsNotExist(err) {
 		logrus.Tracef("baseDir %s for file %s does not exist. Creating.", baseDir, path)
 		if err := os.MkdirAll(baseDir, 0755); err != nil {
 			return err
 		}
+	} else {
+		switch mode := info.Mode(); {
+		case mode&os.ModeSymlink != 0:
+			logrus.Infof("destination cannot be a symlink %v", baseDir)
+			return errors.New("destination cannot be a symlink")
+		}
 	}
 	dest, err := os.Create(path)
 	if err != nil {

pkg/util/image_util.go

@@ -74,15 +74,13 @@ func RetrieveSourceImage(stage config.KanikoStage, opts *config.KanikoOptions) (
 	// If so, look in the local cache before trying the remote registry
 	if opts.CacheDir != "" {
 		cachedImage, err := cachedImage(opts, currentBaseName)
-		if cachedImage != nil {
+		if err != nil {
+			logrus.Errorf("Error while retrieving image from cache: %v %v", currentBaseName, err)
+		} else if cachedImage != nil {
 			return cachedImage, nil
 		}
-
-		if err != nil {
-			logrus.Infof("Error while retrieving image from cache: %v", err)
-		}
 	}
-
+	logrus.Infof("Image %v not found in cache", currentBaseName)
 	// Otherwise, initialize image as usual
 	return RetrieveRemoteImage(currentBaseName, opts)
 }
@@ -93,13 +91,23 @@ func tarballImage(index int) (v1.Image, error) {
 	return tarball.ImageFromPath(tarPath, nil)
 }
 
+// Retrieves the manifest for the specified image from the specified registry
 func remoteImage(image string, opts *config.KanikoOptions) (v1.Image, error) {
-	logrus.Infof("Downloading base image %s", image)
+	logrus.Infof("Retrieving image manifest %s", image)
 	ref, err := name.ParseReference(image, name.WeakValidation)
 	if err != nil {
 		return nil, err
 	}
 
+	rOpts, err := prepareRemoteRequest(ref, opts)
+	if err != nil {
+		return nil, err
+	}
+
+	return remote.Image(ref, rOpts...)
+}
+
+func prepareRemoteRequest(ref name.Reference, opts *config.KanikoOptions) ([]remote.Option, error) {
 	registryName := ref.Context().RegistryStr()
 	if opts.InsecurePull || opts.InsecureRegistries.Contains(registryName) {
 		newReg, err := name.NewRegistry(registryName, name.WeakValidation, name.Insecure)
@@ -122,8 +130,7 @@ func remoteImage(image string, opts *config.KanikoOptions) (v1.Image, error) {
 			InsecureSkipVerify: true,
 		}
 	}
-
+	return []remote.Option{remote.WithTransport(tr), remote.WithAuthFromKeychain(creds.GetKeychain())}, nil
-	return remote.Image(ref, remote.WithTransport(tr), remote.WithAuthFromKeychain(creds.GetKeychain()))
 }
 
 func cachedImage(opts *config.KanikoOptions, image string) (v1.Image, error) {
@@ -136,18 +143,16 @@ func cachedImage(opts *config.KanikoOptions, image string) (v1.Image, error) {
 	if d, ok := ref.(name.Digest); ok {
 		cacheKey = d.DigestStr()
 	} else {
-		img, err := remoteImage(image, opts)
+		image, err := remoteImage(image, opts)
 		if err != nil {
 			return nil, err
 		}
 
-		d, err := img.Digest()
+		d, err := image.Digest()
 		if err != nil {
 			return nil, err
 		}
-
 		cacheKey = d.String()
 	}
-
 	return cache.LocalSource(&opts.CacheOptions, cacheKey)
 }