From ecd61a3d6483d032aea259c2b2ba7e8f34f10c8f Mon Sep 17 00:00:00 2001 From: Damien Neil Date: Thu, 10 Nov 2022 12:16:27 -0800 Subject: [PATCH] [go-1.15.15-eks] os, net/http: avoid escapes from os.DirFS and http.Dir on Windows # AWS EKS Backported To: go-1.15.15-eks Backported On: Fri, 16 Dec 2022 Backported By: ksschumy@amazon.com Backported From: release-branch.go1.18 Upstream Source Commit: https://github.com/golang/go/commit/7013a4f5f816af62033ad63dd06b77c30d7a62a7 # Original Information Do not permit access to Windows reserved device names (NUL, COM1, etc.) via os.DirFS and http.Dir filesystems. Avoid escapes from os.DirFS(`\`) on Windows. DirFS would join the the root to the relative path with a path separator, making os.DirFS(`\`).Open(`/foo/bar`) open the path `\\foo\bar`, which is a UNC name. Not only does this not open the intended file, but permits reference to any file on the system rather than only files on the current drive. Make os.DirFS("") invalid, with all file access failing. Previously, a root of "" was interpreted as "/", which is surprising and probably unintentional. Fixes CVE-2022-41720. Fixes #56694. Change-Id: I275b5fa391e6ad7404309ea98ccc97405942e0f0 Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/1663832 Reviewed-by: Julie Qiu Reviewed-by: Tatiana Bradley Reviewed-on: https://go-review.googlesource.com/c/go/+/455360 Reviewed-by: Michael Pratt TryBot-Result: Gopher Robot Run-TryBot: Jenny Rakoczy --- src/go/build/deps_test.go | 1 + src/internal/safefilepath/path.go | 21 +++++ src/internal/safefilepath/path_other.go | 23 ++++++ src/internal/safefilepath/path_test.go | 88 +++++++++++++++++++++ src/internal/safefilepath/path_windows.go | 95 +++++++++++++++++++++++ src/net/http/fs.go | 8 +- src/net/http/fs_test.go | 28 +++++++ src/os/file.go | 1 - 8 files changed, 261 insertions(+), 4 deletions(-) create mode 100644 src/internal/safefilepath/path.go create mode 100644 src/internal/safefilepath/path_other.go create mode 100644 src/internal/safefilepath/path_test.go create mode 100644 src/internal/safefilepath/path_windows.go diff --git a/src/go/build/deps_test.go b/src/go/build/deps_test.go index 875acebf9c..0c76bd18c4 100644 --- a/src/go/build/deps_test.go +++ b/src/go/build/deps_test.go @@ -148,6 +148,7 @@ var depsRules = ` TIME, io, sort < internal/testlog < internal/poll + < internal/safefilepath < os < os/signal; diff --git a/src/internal/safefilepath/path.go b/src/internal/safefilepath/path.go new file mode 100644 index 0000000000..0f0a270c30 --- /dev/null +++ b/src/internal/safefilepath/path.go @@ -0,0 +1,21 @@ +// Copyright 2022 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 file. + +// Package safefilepath manipulates operating-system file paths. +package safefilepath + +import ( + "errors" +) + +var errInvalidPath = errors.New("invalid path") + +// FromFS converts a slash-separated path into an operating-system path. +// +// FromFS returns an error if the path cannot be represented by the operating +// system. For example, paths containing '\' and ':' characters are rejected +// on Windows. +func FromFS(path string) (string, error) { + return fromFS(path) +} diff --git a/src/internal/safefilepath/path_other.go b/src/internal/safefilepath/path_other.go new file mode 100644 index 0000000000..f93da18680 --- /dev/null +++ b/src/internal/safefilepath/path_other.go @@ -0,0 +1,23 @@ +// Copyright 2022 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 file. + +// +build !windows + +package safefilepath + +import "runtime" + +func fromFS(path string) (string, error) { + if runtime.GOOS == "plan9" { + if len(path) > 0 && path[0] == '#' { + return path, errInvalidPath + } + } + for i := range path { + if path[i] == 0 { + return "", errInvalidPath + } + } + return path, nil +} diff --git a/src/internal/safefilepath/path_test.go b/src/internal/safefilepath/path_test.go new file mode 100644 index 0000000000..dc662c18b3 --- /dev/null +++ b/src/internal/safefilepath/path_test.go @@ -0,0 +1,88 @@ +// Copyright 2022 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 file. + +package safefilepath_test + +import ( + "internal/safefilepath" + "io/ioutil" + "path/filepath" + "runtime" + "testing" +) + +type PathTest struct { + path, result string +} + +const invalid = "" + +var fspathtests = []PathTest{ + {".", "."}, + {"/a/b/c", "/a/b/c"}, + {"a\x00b", invalid}, +} + +var winreservedpathtests = []PathTest{ + {`a\b`, `a\b`}, + {`a:b`, `a:b`}, + {`a/b:c`, `a/b:c`}, + {`NUL`, `NUL`}, + {`./com1`, `./com1`}, + {`a/nul/b`, `a/nul/b`}, +} + +// Whether a reserved name with an extension is reserved or not varies by +// Windows version. +var winreservedextpathtests = []PathTest{ + {"nul.txt", "nul.txt"}, + {"a/nul.txt/b", "a/nul.txt/b"}, +} + +var plan9reservedpathtests = []PathTest{ + {`#c`, `#c`}, +} + +func TestFromFS(t *testing.T) { + switch runtime.GOOS { + case "windows": + if canWriteFile(t, "NUL") { + t.Errorf("can unexpectedly write a file named NUL on Windows") + } + if canWriteFile(t, "nul.txt") { + fspathtests = append(fspathtests, winreservedextpathtests...) + } else { + winreservedpathtests = append(winreservedpathtests, winreservedextpathtests...) + } + for i := range winreservedpathtests { + winreservedpathtests[i].result = invalid + } + for i := range fspathtests { + fspathtests[i].result = filepath.FromSlash(fspathtests[i].result) + } + case "plan9": + for i := range plan9reservedpathtests { + plan9reservedpathtests[i].result = invalid + } + } + tests := fspathtests + tests = append(tests, winreservedpathtests...) + tests = append(tests, plan9reservedpathtests...) + for _, test := range tests { + got, err := safefilepath.FromFS(test.path) + if (got == "") != (err != nil) { + t.Errorf(`FromFS(%q) = %q, %v; want "" only if err != nil`, test.path, got, err) + } + if got != test.result { + t.Errorf("FromFS(%q) = %q, %v; want %q", test.path, got, err, test.result) + } + } +} + +func canWriteFile(t *testing.T, name string) bool { + path := filepath.Join(t.TempDir(), name) + ioutil.WriteFile(path, []byte("ok"), 0666) + b, _ := ioutil.ReadFile(path) + return string(b) == "ok" +} diff --git a/src/internal/safefilepath/path_windows.go b/src/internal/safefilepath/path_windows.go new file mode 100644 index 0000000000..909c150edc --- /dev/null +++ b/src/internal/safefilepath/path_windows.go @@ -0,0 +1,95 @@ +// Copyright 2022 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 file. + +package safefilepath + +import ( + "syscall" + "unicode/utf8" +) + +func fromFS(path string) (string, error) { + if !utf8.ValidString(path) { + return "", errInvalidPath + } + for len(path) > 1 && path[0] == '/' && path[1] == '/' { + path = path[1:] + } + containsSlash := false + for p := path; p != ""; { + // Find the next path element. + i := 0 + dot := -1 + for i < len(p) && p[i] != '/' { + switch p[i] { + case 0, '\\', ':': + return "", errInvalidPath + case '.': + if dot < 0 { + dot = i + } + } + i++ + } + part := p[:i] + if i < len(p) { + containsSlash = true + p = p[i+1:] + } else { + p = "" + } + // Trim the extension and look for a reserved name. + base := part + if dot >= 0 { + base = part[:dot] + } + if isReservedName(base) { + if dot < 0 { + return "", errInvalidPath + } + // The path element is a reserved name with an extension. + // Some Windows versions consider this a reserved name, + // while others do not. Use FullPath to see if the name is + // reserved. + if p, _ := syscall.FullPath(part); len(p) >= 4 && p[:4] == `\\.\` { + return "", errInvalidPath + } + } + } + if containsSlash { + // We can't depend on strings, so substitute \ for / manually. + buf := []byte(path) + for i, b := range buf { + if b == '/' { + buf[i] = '\\' + } + } + path = string(buf) + } + return path, nil +} + +// isReservedName reports if name is a Windows reserved device name. +// It does not detect names with an extension, which are also reserved on some Windows versions. +// +// For details, search for PRN in +// https://docs.microsoft.com/en-us/windows/desktop/fileio/naming-a-file. +func isReservedName(name string) bool { + if 3 <= len(name) && len(name) <= 4 { + switch string([]byte{toUpper(name[0]), toUpper(name[1]), toUpper(name[2])}) { + case "CON", "PRN", "AUX", "NUL": + return len(name) == 3 + case "COM", "LPT": + return len(name) == 4 && '1' <= name[3] && name[3] <= '9' + } + } + return false +} + +func toUpper(c byte) byte { + if 'a' <= c && c <= 'z' { + return c - ('a' - 'A') + } + return c +} diff --git a/src/net/http/fs.go b/src/net/http/fs.go index 922706ada1..068cd0a0cf 100644 --- a/src/net/http/fs.go +++ b/src/net/http/fs.go @@ -9,6 +9,7 @@ package http import ( "errors" "fmt" + "internal/safefilepath" "io" "mime" "mime/multipart" @@ -68,14 +69,15 @@ func mapDirOpenError(originalErr error, name string) error { // Open implements FileSystem using os.Open, opening files for reading rooted // and relative to the directory d. func (d Dir) Open(name string) (File, error) { - if filepath.Separator != '/' && strings.ContainsRune(name, filepath.Separator) { - return nil, errors.New("http: invalid character in file path") + path, err := safefilepath.FromFS(path.Clean("/" + name)) + if err != nil { + return nil, errors.New("http: invalid or unsafe file path") } dir := string(d) if dir == "" { dir = "." } - fullName := filepath.Join(dir, filepath.FromSlash(path.Clean("/"+name))) + fullName := filepath.Join(dir, path) f, err := os.Open(fullName) if err != nil { return nil, mapDirOpenError(err, fullName) diff --git a/src/net/http/fs_test.go b/src/net/http/fs_test.go index c082ceee71..f2fd9f21fa 100644 --- a/src/net/http/fs_test.go +++ b/src/net/http/fs_test.go @@ -615,6 +615,34 @@ func TestFileServerZeroByte(t *testing.T) { } } +func TestFileServerNamesEscape(t *testing.T) { + t.Run("h1", func(t *testing.T) { + testFileServerNamesEscape(t, h1Mode) + }) + t.Run("h2", func(t *testing.T) { + testFileServerNamesEscape(t, h2Mode) + }) +} +func testFileServerNamesEscape(t *testing.T, h2 bool) { + defer afterTest(t) + ts := newClientServerTest(t, h2, FileServer(Dir("testdata"))).ts + defer ts.Close() + for _, path := range []string{ + "/../testdata/file", + "/NUL", // don't read from device files on Windows + } { + res, err := ts.Client().Get(ts.URL + path) + if err != nil { + t.Fatal(err) + } + res.Body.Close() + if res.StatusCode < 400 || res.StatusCode > 599 { + t.Errorf("Get(%q): got status %v, want 4xx or 5xx", path, res.StatusCode) + } + + } +} + type fakeFileInfo struct { dir bool basename string diff --git a/src/os/file.go b/src/os/file.go index a2b71cb61a..0413a8ee6a 100644 --- a/src/os/file.go +++ b/src/os/file.go @@ -37,7 +37,6 @@ // Note: The maximum number of concurrent operations on a File may be limited by // the OS or the system. The number should be high, but exceeding it may degrade // performance or cause other issues. -// package os import ( -- 2.38.1