@@ -3,6 +3,7 @@ package dockerfile

 import (

 	"fmt"

 	"io"

+	"mime"

 	"net/http"

 	"net/url"

 	"os"

@@ -24,6 +25,8 @@ import (

 	"github.com/pkg/errors"

 )

+const unnamedFilename = "__unnamed__"

+

 type pathCache interface {

 	Load(key interface{}) (value interface{}, ok bool)

 	Store(key, value interface{})

@@ -85,8 +88,7 @@ func (o *copier) createCopyInstruction(args []string, cmdName string) (copyInstr

 	// Work in daemon-specific filepath semantics

 	inst.dest = filepath.FromSlash(args[last])

-

-	infos, err := o.getCopyInfosForSourcePaths(args[0:last])

+	infos, err := o.getCopyInfosForSourcePaths(args[0:last], inst.dest)

 	if err != nil {

 		return inst, errors.Wrapf(err, "%s failed", cmdName)

 	}

@@ -99,10 +101,11 @@ func (o *copier) createCopyInstruction(args []string, cmdName string) (copyInstr

 // getCopyInfosForSourcePaths iterates over the source files and calculate the info

 // needed to copy (e.g. hash value if cached)

-func (o *copier) getCopyInfosForSourcePaths(sources []string) ([]copyInfo, error) {

+// The dest is used in case source is URL (and ends with "/")

+func (o *copier) getCopyInfosForSourcePaths(sources []string, dest string) ([]copyInfo, error) {

 	var infos []copyInfo

 	for _, orig := range sources {

-		subinfos, err := o.getCopyInfoForSourcePath(orig)

+		subinfos, err := o.getCopyInfoForSourcePath(orig, dest)

 		if err != nil {

 			return nil, err

 		}

@@ -115,7 +118,7 @@ func (o *copier) getCopyInfosForSourcePaths(sources []string) ([]copyInfo, error

 	return infos, nil

 }

-func (o *copier) getCopyInfoForSourcePath(orig string) ([]copyInfo, error) {

+func (o *copier) getCopyInfoForSourcePath(orig, dest string) ([]copyInfo, error) {

 	if !urlutil.IsURL(orig) {

 		return o.calcCopyInfo(orig, true)

 	}

@@ -123,6 +126,14 @@ func (o *copier) getCopyInfoForSourcePath(orig string) ([]copyInfo, error) {

 	if err != nil {

 		return nil, err

 	}

+	// If path == "" then we are unable to determine filename from src

+	// We have to make sure dest is available

+	if path == "" {

+		if strings.HasSuffix(dest, "/") {

+			return nil, errors.Errorf("cannot determine filename for source %s", orig)

+		}

+		path = unnamedFilename

+	}

 	o.tmpPaths = append(o.tmpPaths, remote.Root())

 	hash, err := remote.Hash(path)

@@ -301,22 +312,40 @@ func errOnSourceDownload(_ string) (builder.Source, string, error) {

 	return nil, "", errors.New("source can't be a URL for COPY")

 }

+func getFilenameForDownload(path string, resp *http.Response) string {

+	// Guess filename based on source

+	if path != "" && !strings.HasSuffix(path, "/") {

+		if filename := filepath.Base(filepath.FromSlash(path)); filename != "" {

+			return filename

+		}

+	}

+

+	// Guess filename based on Content-Disposition

+	if contentDisposition := resp.Header.Get("Content-Disposition"); contentDisposition != "" {

+		if _, params, err := mime.ParseMediaType(contentDisposition); err == nil {

+			if params["filename"] != "" && !strings.HasSuffix(params["filename"], "/") {

+				if filename := filepath.Base(filepath.FromSlash(params["filename"])); filename != "" {

+					return filename

+				}

+			}

+		}

+	}

+	return ""

+}

+

 func downloadSource(output io.Writer, stdout io.Writer, srcURL string) (remote builder.Source, p string, err error) {

 	u, err := url.Parse(srcURL)

 	if err != nil {

 		return

 	}

-	filename := filepath.Base(filepath.FromSlash(u.Path)) // Ensure in platform semantics

-	if filename == "" {

-		err = errors.Errorf("cannot determine filename from url: %s", u)

-		return

-	}

 	resp, err := remotecontext.GetWithStatusError(srcURL)

 	if err != nil {

 		return

 	}

+	filename := getFilenameForDownload(u.Path, resp)

+

 	// Prepare file in a tmp dir

 	tmpDir, err := ioutils.TempDir("", "docker-remote")

 	if err != nil {

@@ -327,7 +356,13 @@ func downloadSource(output io.Writer, stdout io.Writer, srcURL string) (remote b

 			os.RemoveAll(tmpDir)

 		}

 	}()

-	tmpFileName := filepath.Join(tmpDir, filename)

+	// If filename is empty, the returned filename will be "" but

+	// the tmp filename will be created as "__unnamed__"

+	tmpFileName := filename

+	if filename == "" {

+		tmpFileName = unnamedFilename

+	}

+	tmpFileName = filepath.Join(tmpDir, tmpFileName)

 	tmpFile, err := os.OpenFile(tmpFileName, os.O_RDWR|os.O_CREATE|os.O_EXCL, 0600)

 	if err != nil {

 		return

@@ -6506,3 +6506,19 @@ RUN touch /foop

 	c.Assert(err, check.IsNil)

 	c.Assert(d.String(), checker.Equals, getIDByName(c, name))

 }

+

+// Test case for #34208

+func (s *DockerSuite) TestBuildAddHTTPRoot(c *check.C) {

+	testRequires(c, Network, DaemonIsLinux)

+	buildImageSuccessfully(c, "buildaddhttproot", build.WithDockerfile(`

+                FROM scratch

+                ADD http://example.com/index.html /example1

+                ADD http://example.com /example2

+                ADD http://example.com /example3`))

+	buildImage("buildaddhttprootfailure", build.WithDockerfile(`

+                FROM scratch

+                ADD http://example.com/ /`)).Assert(c, icmd.Expected{

+		ExitCode: 1,

+		Err:      "cannot determine filename for source http://example.com/",

+	})

+}