Fix symlink handling in builder ADD/COPY commands

Fixes #17290

Fixes following issues:

- Cache checksums turning off while walking a broken symlink.

- Cache checksums were taken from symlinks while targets were actually copied.

- Copying a symlink pointing to a file to a directory used the basename of the target as a destination basename, instead of basename of the symlink.

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>
(cherry picked from commit 47da59f7ec4ee0f49d47a9b32abb137bb30b2c48)

integration-cli/docker_cli_build_test.go

@@ -20,6 +20,7 @@ import (
 
 	"github.com/docker/docker/builder/dockerfile/command"
 	"github.com/docker/docker/pkg/archive"
+	"github.com/docker/docker/pkg/integration/checker"
 	"github.com/docker/docker/pkg/stringutils"
 	"github.com/go-check/check"
 )
@@ -6223,3 +6224,127 @@ func (s *DockerSuite) TestBuildNoNamedVolume(c *check.C) {
 	_, err := buildImage("test", dockerFile, false)
 	c.Assert(err, check.NotNil, check.Commentf("image build should have failed"))
 }
+
+// #17290
+func (s *DockerSuite) TestBuildCacheBrokenSymlink(c *check.C) {
+	testRequires(c, DaemonIsLinux)
+	name := "testbuildbrokensymlink"
+	ctx, err := fakeContext(`
+	FROM busybox
+	COPY . ./`,
+		map[string]string{
+			"foo": "bar",
+		})
+	c.Assert(err, checker.IsNil)
+	defer ctx.Close()
+
+	err = os.Symlink(filepath.Join(ctx.Dir, "nosuchfile"), filepath.Join(ctx.Dir, "asymlink"))
+	c.Assert(err, checker.IsNil)
+
+	// warm up cache
+	_, err = buildImageFromContext(name, ctx, true)
+	c.Assert(err, checker.IsNil)
+
+	// add new file to context, should invalidate cache
+	err = ioutil.WriteFile(filepath.Join(ctx.Dir, "newfile"), []byte("foo"), 0644)
+	c.Assert(err, checker.IsNil)
+
+	_, out, err := buildImageFromContextWithOut(name, ctx, true)
+	c.Assert(err, checker.IsNil)
+
+	c.Assert(out, checker.Not(checker.Contains), "Using cache")
+
+}
+
+func (s *DockerSuite) TestBuildFollowSymlinkToFile(c *check.C) {
+	testRequires(c, DaemonIsLinux)
+	name := "testbuildbrokensymlink"
+	ctx, err := fakeContext(`
+	FROM busybox
+	COPY asymlink target`,
+		map[string]string{
+			"foo": "bar",
+		})
+	c.Assert(err, checker.IsNil)
+	defer ctx.Close()
+
+	err = os.Symlink("foo", filepath.Join(ctx.Dir, "asymlink"))
+	c.Assert(err, checker.IsNil)
+
+	id, err := buildImageFromContext(name, ctx, true)
+	c.Assert(err, checker.IsNil)
+
+	out, _ := dockerCmd(c, "run", "--rm", id, "cat", "target")
+	c.Assert(out, checker.Matches, "bar")
+
+	// change target file should invalidate cache
+	err = ioutil.WriteFile(filepath.Join(ctx.Dir, "foo"), []byte("baz"), 0644)
+	c.Assert(err, checker.IsNil)
+
+	id, out, err = buildImageFromContextWithOut(name, ctx, true)
+	c.Assert(err, checker.IsNil)
+	c.Assert(out, checker.Not(checker.Contains), "Using cache")
+
+	out, _ = dockerCmd(c, "run", "--rm", id, "cat", "target")
+	c.Assert(out, checker.Matches, "baz")
+}
+
+func (s *DockerSuite) TestBuildFollowSymlinkToDir(c *check.C) {
+	testRequires(c, DaemonIsLinux)
+	name := "testbuildbrokensymlink"
+	ctx, err := fakeContext(`
+	FROM busybox
+	COPY asymlink /`,
+		map[string]string{
+			"foo/abc": "bar",
+			"foo/def": "baz",
+		})
+	c.Assert(err, checker.IsNil)
+	defer ctx.Close()
+
+	err = os.Symlink("foo", filepath.Join(ctx.Dir, "asymlink"))
+	c.Assert(err, checker.IsNil)
+
+	id, err := buildImageFromContext(name, ctx, true)
+	c.Assert(err, checker.IsNil)
+
+	out, _ := dockerCmd(c, "run", "--rm", id, "cat", "abc", "def")
+	c.Assert(out, checker.Matches, "barbaz")
+
+	// change target file should invalidate cache
+	err = ioutil.WriteFile(filepath.Join(ctx.Dir, "foo/def"), []byte("bax"), 0644)
+	c.Assert(err, checker.IsNil)
+
+	id, out, err = buildImageFromContextWithOut(name, ctx, true)
+	c.Assert(err, checker.IsNil)
+	c.Assert(out, checker.Not(checker.Contains), "Using cache")
+
+	out, _ = dockerCmd(c, "run", "--rm", id, "cat", "abc", "def")
+	c.Assert(out, checker.Matches, "barbax")
+
+}
+
+// TestBuildSymlinkBasename tests that target file gets basename from symlink,
+// not from the target file.
+func (s *DockerSuite) TestBuildSymlinkBasename(c *check.C) {
+	testRequires(c, DaemonIsLinux)
+	name := "testbuildbrokensymlink"
+	ctx, err := fakeContext(`
+	FROM busybox
+	COPY asymlink /`,
+		map[string]string{
+			"foo": "bar",
+		})
+	c.Assert(err, checker.IsNil)
+	defer ctx.Close()
+
+	err = os.Symlink("foo", filepath.Join(ctx.Dir, "asymlink"))
+	c.Assert(err, checker.IsNil)
+
+	id, err := buildImageFromContext(name, ctx, true)
+	c.Assert(err, checker.IsNil)
+
+	out, _ := dockerCmd(c, "run", "--rm", id, "cat", "asymlink")
+	c.Assert(out, checker.Matches, "bar")
+
+}

integration-cli/docker_utils.go

@@ -1214,6 +1214,14 @@ func buildImage(name, dockerfile string, useCache bool, buildFlags ...string) (s
 }
 
 func buildImageFromContext(name string, ctx *FakeContext, useCache bool, buildFlags ...string) (string, error) {
+	id, _, err := buildImageFromContextWithOut(name, ctx, useCache, buildFlags...)
+	if err != nil {
+		return "", err
+	}
+	return id, nil
+}
+
+func buildImageFromContextWithOut(name string, ctx *FakeContext, useCache bool, buildFlags ...string) (string, string, error) {
 	args := []string{"build", "-t", name}
 	if !useCache {
 		args = append(args, "--no-cache")
@@ -1224,9 +1232,13 @@ func buildImageFromContext(name string, ctx *FakeContext, useCache bool, buildFl
 	buildCmd.Dir = ctx.Dir
 	out, exitCode, err := runCommandWithOutput(buildCmd)
 	if err != nil || exitCode != 0 {
-		return "", fmt.Errorf("failed to build the image: %s", out)
+		return "", "", fmt.Errorf("failed to build the image: %s", out)
 	}
-	return getIDByName(name)
+	id, err := getIDByName(name)
+	if err != nil {
+		return "", "", err
+	}
+	return id, out, nil
 }
 
 func buildImageFromPath(name, path string, useCache bool, buildFlags ...string) (string, error) {