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Use cyphar/filepath-securejoin instead of docker pkg/symlink

Browse Source 
runc shouldn't depend on docker and be more self-contained.
Removing github.com/pkg/symlink dep is the first step to not depend on docker anymore

Signed-off-by: Vincent Demeester <vincent@sbr.pm>
This commit is contained in:
Vincent Demeester
2017-10-27 15:30:30 +02:00
parent 9a1186d128
commit 594501475e
17 changed files with 1970 additions and 331 deletions
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vendor/github.com/docker/docker/pkg/symlink/LICENSE.BSD → vendor/github.com/cyphar/filepath-securejoin/LICENSE
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Copyright (c) 2014-2015 The Docker & Go Authors. All rights reserved.
Copyright (C) 2014-2015 Docker Inc & Go Authors. All rights reserved.
Copyright (C) 2017 SUSE LLC. All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
vendor/github.com/cyphar/filepath-securejoin/README.md
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## `filepath-securejoin` ##
[![Build Status](https://travis-ci.org/cyphar/filepath-securejoin.svg?branch=master)](https://travis-ci.org/cyphar/filepath-securejoin)
An implementation of `SecureJoin`, a [candidate for inclusion in the Go
standard library][go#20126]. The purpose of this function is to be a "secure"
alternative to `filepath.Join`, and in particular it provides certain
guarantees that are not provided by `filepath.Join`.
This is the function prototype:
```go
func SecureJoin(root, unsafePath string) (string, error)
```
This library **guarantees** the following:
* If no error is set, the resulting string **must** be a child path of
`SecureJoin` and will not contain any symlink path components (they will all
be expanded).
* When expanding symlinks, all symlink path components **must** be resolved
relative to the provided root. In particular, this can be considered a
userspace implementation of how `chroot(2)` operates on file paths. Note that
these symlinks will **not** be expanded lexically (`filepath.Clean` is not
called on the input before processing).
* Non-existant path components are unaffected by `SecureJoin` (similar to
`filepath.EvalSymlinks`'s semantics).
* The returned path will always be `filepath.Clean`ed and thus not contain any
`..` components.
A (trivial) implementation of this function on GNU/Linux systems could be done
with the following (note that this requires root privileges and is far more
opaque than the implementation in this library, and also requires that
`readlink` is inside the `root` path):
```go
package securejoin
import (
"os/exec"
"path/filepath"
)
func SecureJoin(root, unsafePath string) (string, error) {
unsafePath = string(filepath.Separator) + unsafePath
cmd := exec.Command("chroot", root,
"readlink", "--canonicalize-missing", "--no-newline", unsafePath)
output, err := cmd.CombinedOutput()
if err != nil {
return "", err
}
expanded := string(output)
return filepath.Join(root, expanded), nil
}
```
[go#20126]: https://github.com/golang/go/issues/20126
### License ###
The license of this project is the same as Go, which is a BSD 3-clause license
available in the `LICENSE` file.
vendor/github.com/cyphar/filepath-securejoin/join.go
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// Copyright (C) 2014-2015 Docker Inc & Go Authors. All rights reserved.
// Copyright (C) 2017 SUSE LLC. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package securejoin is an implementation of the hopefully-soon-to-be-included
// SecureJoin helper that is meant to be part of the "path/filepath" package.
// The purpose of this project is to provide a PoC implementation to make the
// SecureJoin proposal (https://github.com/golang/go/issues/20126) more
// tangible.
package securejoin
import (
"bytes"
"fmt"
"os"
"path/filepath"
"strings"
"syscall"
"github.com/pkg/errors"
)
// ErrSymlinkLoop is returned by SecureJoinVFS when too many symlinks have been
// evaluated in attempting to securely join the two given paths.
var ErrSymlinkLoop = fmt.Errorf("SecureJoin: too many links")
// IsNotExist tells you if err is an error that implies that either the path
// accessed does not exist (or path components don't exist). This is
// effectively a more broad version of os.IsNotExist.
func IsNotExist(err error) bool {
// If it's a bone-fide ENOENT just bail.
if os.IsNotExist(errors.Cause(err)) {
return true
}
// Check that it's not actually an ENOTDIR, which in some cases is a more
// convoluted case of ENOENT (usually involving weird paths).
var errno error
switch err := errors.Cause(err).(type) {
case *os.PathError:
errno = err.Err
case *os.LinkError:
errno = err.Err
case *os.SyscallError:
errno = err.Err
}
return errno == syscall.ENOTDIR || errno == syscall.ENOENT
}
// SecureJoinVFS joins the two given path components (similar to Join) except
// that the returned path is guaranteed to be scoped inside the provided root
// path (when evaluated). Any symbolic links in the path are evaluated with the
// given root treated as the root of the filesystem, similar to a chroot. The
// filesystem state is evaluated through the given VFS interface (if nil, the
// standard os.* family of functions are used).
//
// Note that the guarantees provided by this function only apply if the path
// components in the returned string are not modified (in other words are not
// replaced with symlinks on the filesystem) after this function has returned.
// Such a symlink race is necessarily out-of-scope of SecureJoin.
func SecureJoinVFS(root, unsafePath string, vfs VFS) (string, error) {
// Use the os.* VFS implementation if none was specified.
if vfs == nil {
vfs = osVFS{}
}
var path bytes.Buffer
n := 0
for unsafePath != "" {
if n > 255 {
return "", ErrSymlinkLoop
}
// Next path component, p.
i := strings.IndexRune(unsafePath, filepath.Separator)
var p string
if i == -1 {
p, unsafePath = unsafePath, ""
} else {
p, unsafePath = unsafePath[:i], unsafePath[i+1:]
}
// Create a cleaned path, using the lexical semantics of /../a, to
// create a "scoped" path component which can safely be joined to fullP
// for evaluation. At this point, path.String() doesn't contain any
// symlink components.
cleanP := filepath.Clean(string(filepath.Separator) + path.String() + p)
if cleanP == string(filepath.Separator) {
path.Reset()
continue
}
fullP := filepath.Clean(root + cleanP)
// Figure out whether the path is a symlink.
fi, err := vfs.Lstat(fullP)
if err != nil && !IsNotExist(err) {
return "", err
}
// Treat non-existent path components the same as non-symlinks (we
// can't do any better here).
if IsNotExist(err) || fi.Mode()&os.ModeSymlink == 0 {
path.WriteString(p)
path.WriteRune(filepath.Separator)
continue
}
// Only increment when we actually dereference a link.
n++
// It's a symlink, expand it by prepending it to the yet-unparsed path.
dest, err := vfs.Readlink(fullP)
if err != nil {
return "", err
}
// Absolute symlinks reset any work we've already done.
if filepath.IsAbs(dest) {
path.Reset()
}
unsafePath = dest + string(filepath.Separator) + unsafePath
}
// We have to clean path.String() here because it may contain '..'
// components that are entirely lexical, but would be misleading otherwise.
// And finally do a final clean to ensure that root is also lexically
// clean.
fullP := filepath.Clean(string(filepath.Separator) + path.String())
return filepath.Clean(root + fullP), nil
}
// SecureJoin is a wrapper around SecureJoinVFS that just uses the os.* library
// of functions as the VFS. If in doubt, use this function over SecureJoinVFS.
func SecureJoin(root, unsafePath string) (string, error) {
return SecureJoinVFS(root, unsafePath, nil)
}
vendor/github.com/cyphar/filepath-securejoin/vendor.conf
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github.com/pkg/errors v0.8.0
vendor/github.com/cyphar/filepath-securejoin/vfs.go
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// Copyright (C) 2017 SUSE LLC. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package securejoin
import "os"
// In future this should be moved into a separate package, because now there
// are several projects (umoci and go-mtree) that are using this sort of
// interface.
// VFS is the minimal interface necessary to use SecureJoinVFS. A nil VFS is
// equivalent to using the standard os.* family of functions. This is mainly
// used for the purposes of mock testing, but also can be used to otherwise use
// SecureJoin with VFS-like system.
type VFS interface {
// Lstat returns a FileInfo describing the named file. If the file is a
// symbolic link, the returned FileInfo describes the symbolic link. Lstat
// makes no attempt to follow the link. These semantics are identical to
// os.Lstat.
Lstat(name string) (os.FileInfo, error)
// Readlink returns the destination of the named symbolic link. These
// semantics are identical to os.Readlink.
Readlink(name string) (string, error)
}
// osVFS is the "nil" VFS, in that it just passes everything through to the os
// module.
type osVFS struct{}
// Lstat returns a FileInfo describing the named file. If the file is a
// symbolic link, the returned FileInfo describes the symbolic link. Lstat
// makes no attempt to follow the link. These semantics are identical to
// os.Lstat.
func (o osVFS) Lstat(name string) (os.FileInfo, error) { return os.Lstat(name) }
// Readlink returns the destination of the named symbolic link. These
// semantics are identical to os.Readlink.
func (o osVFS) Readlink(name string) (string, error) { return os.Readlink(name) }
vendor/github.com/docker/docker/pkg/symlink/LICENSE.APACHE
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Apache License
Version 2.0, January 2004
http://www.apache.org/licenses/
TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
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"License" shall mean the terms and conditions for use, reproduction,
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outstanding shares, or (iii) beneficial ownership of such entity.
"You" (or "Your") shall mean an individual or Legal Entity
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"Work" shall mean the work of authorship, whether in Source or
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5. Submission of Contributions. Unless You explicitly state otherwise,
any Contribution intentionally submitted for inclusion in the Work
by You to the Licensor shall be under the terms and conditions of
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Notwithstanding the above, nothing herein shall supersede or modify
the terms of any separate license agreement you may have executed
with Licensor regarding such Contributions.
6. Trademarks. This License does not grant permission to use the trade
names, trademarks, service marks, or product names of the Licensor,
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7. Disclaimer of Warranty. Unless required by applicable law or
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risks associated with Your exercise of permissions under this License.
8. Limitation of Liability. In no event and under no legal theory,
whether in tort (including negligence), contract, or otherwise,
unless required by applicable law (such as deliberate and grossly
negligent acts) or agreed to in writing, shall any Contributor be
liable to You for damages, including any direct, indirect, special,
incidental, or consequential damages of any character arising as a
result of this License or out of the use or inability to use the
Work (including but not limited to damages for loss of goodwill,
work stoppage, computer failure or malfunction, or any and all
other commercial damages or losses), even if such Contributor
has been advised of the possibility of such damages.
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the Work or Derivative Works thereof, You may choose to offer,
and charge a fee for, acceptance of support, warranty, indemnity,
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on Your own behalf and on Your sole responsibility, not on behalf
of any other Contributor, and only if You agree to indemnify,
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incurred by, or claims asserted against, such Contributor by reason
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END OF TERMS AND CONDITIONS
Copyright 2014-2015 Docker, Inc.
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
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Unless required by applicable law or agreed to in writing, software
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
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vendor/github.com/docker/docker/pkg/symlink/README.md
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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.
vendor/github.com/docker/docker/pkg/symlink/fs.go
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// 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 (
"bytes"
"errors"
"os"
"path/filepath"
"strings"
)
// 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
}
root, err = filepath.Abs(root)
if err != nil {
return "", err
}
return evalSymlinksInScope(path, root)
}
// 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(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)
}
// 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:]
}
if p == "" {
continue
}
// 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
}
// 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
}
// 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
}