new file mode 100644

@@ -0,0 +1,191 @@

+

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+

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+   END OF TERMS AND CONDITIONS

+

+   Copyright 2014 Docker, Inc.

+

+   Licensed under the Apache License, Version 2.0 (the "License");

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+   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.

new file mode 100644

@@ -0,0 +1,27 @@

+Copyright (c) 2014 The Docker & Go Authors. All rights reserved.

+

+Redistribution and use in source and binary forms, with or without

+modification, are permitted provided that the following conditions are

+met:

+

+   * Redistributions of source code must retain the above copyright

+notice, this list of conditions and the following disclaimer.

+   * Redistributions in binary form must reproduce the above

+copyright notice, this list of conditions and the following disclaimer

+in the documentation and/or other materials provided with the

+distribution.

+   * Neither the name of Google Inc. nor the names of its

+contributors may be used to endorse or promote products derived from

+this software without specific prior written permission.

+

+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT

+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

@@ -1,2 +1,3 @@

-Michael Crosby <michael@crosbymichael.com> (@crosbymichael)

-Victor Vieux <vieux@docker.com> (@vieux)

+Tibor Vass <teabee89@gmail.com> (@tiborvass)

+Cristian Staretu <cristian.staretu@gmail.com> (@unclejack)

+Tianon Gravi <admwiggin@gmail.com> (@tianon)

new file mode 100644

@@ -0,0 +1,5 @@

+Package symlink implements EvalSymlinksInScope which is an extension of filepath.EvalSymlinks

+from the [Go standard library](https://golang.org/pkg/path/filepath).

+

+The code from filepath.EvalSymlinks has been adapted in fs.go.

+Please read the LICENSE.BSD file that governs fs.go and LICENSE.APACHE for fs_test.go.

@@ -1,101 +1,131 @@

+// Copyright 2012 The Go Authors. All rights reserved.

+// Use of this source code is governed by a BSD-style

+// license that can be found in the LICENSE.BSD file.

+

+// This code is a modified version of path/filepath/symlink.go from the Go standard library.

+

 package symlink

 import (

-	"fmt"

+	"bytes"

+	"errors"

 	"os"

-	"path"

 	"path/filepath"

 	"strings"

 )

-const maxLoopCounter = 100

-

-// FollowSymlink will follow an existing link and scope it to the root

-// path provided.

-// The role of this function is to return an absolute path in the root

-// or normalize to the root if the symlink leads to a path which is

-// outside of the root.

-// Errors encountered while attempting to follow the symlink in path

-// will be reported.

-// Normalizations to the root don't constitute errors.

-func FollowSymlinkInScope(link, root string) (string, error) {

-	root, err := filepath.Abs(root)

+// FollowSymlinkInScope is a wrapper around evalSymlinksInScope that returns an absolute path

+func FollowSymlinkInScope(path, root string) (string, error) {

+	path, err := filepath.Abs(path)

 	if err != nil {

 		return "", err

 	}

-

-	link, err = filepath.Abs(link)

+	root, err = filepath.Abs(root)

 	if err != nil {

 		return "", err

 	}

+	return evalSymlinksInScope(path, root)

+}

-	if link == root {

-		return root, nil

+// evalSymlinksInScope will evaluate symlinks in `path` within a scope `root` and return

+// a result guaranteed to be contained within the scope `root`, at the time of the call.

+// Symlinks in `root` are not evaluated and left as-is.

+// Errors encountered while attempting to evaluate symlinks in path will be returned.

+// Non-existing paths are valid and do not constitute an error.

+// `path` has to contain `root` as a prefix, or else an error will be returned.

+// Trying to break out from `root` does not constitute an error.

+//

+// Example:

+//   If /foo/bar -> /outside,

+//   FollowSymlinkInScope("/foo/bar", "/foo") == "/foo/outside" instead of "/oustide"

+//

+// IMPORTANT: it is the caller's responsibility to call evalSymlinksInScope *after* relevant symlinks

+// are created and not to create subsequently, additional symlinks that could potentially make a

+// previously-safe path, unsafe. Example: if /foo/bar does not exist, evalSymlinksInScope("/foo/bar", "/foo")

+// would return "/foo/bar". If one makes /foo/bar a symlink to /baz subsequently, then "/foo/bar" should

+// no longer be considered safely contained in "/foo".

+func evalSymlinksInScope(path, root string) (string, error) {

+	root = filepath.Clean(root)

+	if path == root {

+		return path, nil

 	}

-

-	if !strings.HasPrefix(filepath.Dir(link), root) {

-		return "", fmt.Errorf("%s is not within %s", link, root)

+	if !strings.HasPrefix(path, root) {

+		return "", errors.New("evalSymlinksInScope: " + path + " is not in " + root)

 	}

+	const maxIter = 255

+	originalPath := path

+	// given root of "/a" and path of "/a/b/../../c" we want path to be "/b/../../c"

+	path = path[len(root):]

+	if root == string(filepath.Separator) {

+		path = string(filepath.Separator) + path

+	}

+	if !strings.HasPrefix(path, string(filepath.Separator)) {

+		return "", errors.New("evalSymlinksInScope: " + path + " is not in " + root)

+	}

+	path = filepath.Clean(path)

+	// consume path by taking each frontmost path element,

+	// expanding it if it's a symlink, and appending it to b

+	var b bytes.Buffer

+	// b here will always be considered to be the "current absolute path inside

+	// root" when we append paths to it, we also append a slash and use

+	// filepath.Clean after the loop to trim the trailing slash

+	for n := 0; path != ""; n++ {

+		if n > maxIter {

+			return "", errors.New("evalSymlinksInScope: too many links in " + originalPath)

+		}

-	prev := "/"

-

-	for _, p := range strings.Split(link, "/") {

-		prev = filepath.Join(prev, p)

-

-		loopCounter := 0

-		for {

-			loopCounter++

-

-			if loopCounter >= maxLoopCounter {

-				return "", fmt.Errorf("loopCounter reached MAX: %v", loopCounter)

-			}

-

-			if !strings.HasPrefix(prev, root) {

-				// Don't resolve symlinks outside of root. For example,

-				// we don't have to check /home in the below.

-				//

-				//   /home -> usr/home

-				//   FollowSymlinkInScope("/home/bob/foo/bar", "/home/bob/foo")

-				break

-			}

-

-			stat, err := os.Lstat(prev)

-			if err != nil {

-				if os.IsNotExist(err) {

-					break

-				}

-				return "", err

-			}

-

-			// let's break if we're not dealing with a symlink

-			if stat.Mode()&os.ModeSymlink != os.ModeSymlink {

-				break

-			}

+		// find next path component, p

+		i := strings.IndexRune(path, filepath.Separator)

+		var p string

+		if i == -1 {

+			p, path = path, ""

+		} else {

+			p, path = path[:i], path[i+1:]

+		}

-			// process the symlink

-			dest, err := os.Readlink(prev)

-			if err != nil {

-				return "", err

-			}

+		if p == "" {

+			continue

+		}

-			if path.IsAbs(dest) {

-				prev = filepath.Join(root, dest)

-			} else {

-				prev, _ = filepath.Abs(prev)

+		// this takes a b.String() like "b/../" and a p like "c" and turns it

+		// into "/b/../c" which then gets filepath.Cleaned into "/c" and then

+		// root gets prepended and we Clean again (to remove any trailing slash

+		// if the first Clean gave us just "/")

+		cleanP := filepath.Clean(string(filepath.Separator) + b.String() + p)

+		if cleanP == string(filepath.Separator) {

+			// never Lstat "/" itself

+			b.Reset()

+			continue

+		}

+		fullP := filepath.Clean(root + cleanP)

+

+		fi, err := os.Lstat(fullP)

+		if os.IsNotExist(err) {

+			// if p does not exist, accept it

+			b.WriteString(p)

+			b.WriteRune(filepath.Separator)

+			continue

+		}

+		if err != nil {

+			return "", err

+		}

+		if fi.Mode()&os.ModeSymlink == 0 {

+			b.WriteString(p + string(filepath.Separator))

+			continue

+		}

-				dir := filepath.Dir(prev)

-				prev = filepath.Join(dir, dest)

-				if dir == root && !strings.HasPrefix(prev, root) {

-					prev = root

-				}

-				if len(prev) < len(root) || (len(prev) == len(root) && prev != root) {

-					prev = filepath.Join(root, filepath.Base(dest))

-				}

-			}

+		// it's a symlink, put it at the front of path

+		dest, err := os.Readlink(fullP)

+		if err != nil {

+			return "", err

 		}

+		if filepath.IsAbs(dest) {

+			b.Reset()

+		}

+		path = dest + string(filepath.Separator) + path

 	}

-	if prev == "/" {

-		prev = root

-	}

-	return prev, nil

+

+	// see note above on "fullP := ..." for why this is double-cleaned and

+	// what's happening here

+	return filepath.Clean(root + filepath.Clean(string(filepath.Separator)+b.String())), nil

 }

@@ -1,3 +1,5 @@

+// Licensed under the Apache License, Version 2.0; See LICENSE.APACHE

+

 package symlink

 import (