From e18a8a7d9c98d04fb6294255e18250cb15172e79 Mon Sep 17 00:00:00 2001 From: "renovate[bot]" <29139614+renovate[bot]@users.noreply.github.com> Date: Thu, 11 Jul 2024 17:07:31 +0000 Subject: [PATCH] fix(deps): update module github.com/cyphar/filepath-securejoin to v0.3.0 Signed-off-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com> --- go.mod | 2 +- go.sum | 4 +- .../cyphar/filepath-securejoin/LICENSE | 2 +- .../cyphar/filepath-securejoin/README.md | 139 ++++- .../cyphar/filepath-securejoin/VERSION | 2 +- .../cyphar/filepath-securejoin/join.go | 8 +- .../filepath-securejoin/lookup_linux.go | 380 ++++++++++++++ .../cyphar/filepath-securejoin/mkdir_linux.go | 228 +++++++++ .../cyphar/filepath-securejoin/open_linux.go | 83 +++ .../filepath-securejoin/openat2_linux.go | 128 +++++ .../filepath-securejoin/openat_linux.go | 59 +++ .../filepath-securejoin/procfs_linux.go | 481 ++++++++++++++++++ .../testing_mocks_linux.go | 68 +++ .../cyphar/filepath-securejoin/vfs.go | 2 +- vendor/modules.txt | 4 +- 15 files changed, 1556 insertions(+), 34 deletions(-) create mode 100644 vendor/github.com/cyphar/filepath-securejoin/lookup_linux.go create mode 100644 vendor/github.com/cyphar/filepath-securejoin/mkdir_linux.go create mode 100644 vendor/github.com/cyphar/filepath-securejoin/open_linux.go create mode 100644 vendor/github.com/cyphar/filepath-securejoin/openat2_linux.go create mode 100644 vendor/github.com/cyphar/filepath-securejoin/openat_linux.go create mode 100644 vendor/github.com/cyphar/filepath-securejoin/procfs_linux.go create mode 100644 vendor/github.com/cyphar/filepath-securejoin/testing_mocks_linux.go diff --git a/go.mod b/go.mod index 43edc24b6..a82e314ec 100644 --- a/go.mod +++ b/go.mod @@ -16,7 +16,7 @@ require ( github.com/containers/ocicrypt v1.2.0 github.com/containers/storage v1.54.1-0.20240627145511-52b643e1ff51 github.com/coreos/go-systemd/v22 v22.5.0 - github.com/cyphar/filepath-securejoin v0.2.5 + github.com/cyphar/filepath-securejoin v0.3.0 github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc github.com/disiqueira/gotree/v3 v3.0.2 github.com/docker/distribution v2.8.3+incompatible diff --git a/go.sum b/go.sum index c7ee84215..999da739e 100644 --- a/go.sum +++ b/go.sum @@ -72,8 +72,8 @@ github.com/coreos/go-systemd/v22 v22.5.0/go.mod h1:Y58oyj3AT4RCenI/lSvhwexgC+NSV github.com/cpuguy83/go-md2man/v2 v2.0.4/go.mod h1:tgQtvFlXSQOSOSIRvRPT7W67SCa46tRHOmNcaadrF8o= github.com/cyberphone/json-canonicalization v0.0.0-20231217050601-ba74d44ecf5f h1:eHnXnuK47UlSTOQexbzxAZfekVz6i+LKRdj1CU5DPaM= github.com/cyberphone/json-canonicalization v0.0.0-20231217050601-ba74d44ecf5f/go.mod h1:uzvlm1mxhHkdfqitSA92i7Se+S9ksOn3a3qmv/kyOCw= -github.com/cyphar/filepath-securejoin v0.2.5 h1:6iR5tXJ/e6tJZzzdMc1km3Sa7RRIVBKAK32O2s7AYfo= -github.com/cyphar/filepath-securejoin v0.2.5/go.mod h1:aPGpWjXOXUn2NCNjFvBE6aRxGGx79pTxQpKOJNYHHl4= +github.com/cyphar/filepath-securejoin v0.3.0 h1:tXpmbiaeBrS/K2US8nhgwdKYnfAOnVfkcLPKFgFHeA0= +github.com/cyphar/filepath-securejoin v0.3.0/go.mod h1:F7i41x/9cBF7lzCrVsYs9fuzwRZm4NQsGTBdpp6mETc= github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38= github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38= github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc h1:U9qPSI2PIWSS1VwoXQT9A3Wy9MM3WgvqSxFWenqJduM= diff --git a/vendor/github.com/cyphar/filepath-securejoin/LICENSE b/vendor/github.com/cyphar/filepath-securejoin/LICENSE index bec842f29..cb1ab88da 100644 --- a/vendor/github.com/cyphar/filepath-securejoin/LICENSE +++ b/vendor/github.com/cyphar/filepath-securejoin/LICENSE @@ -1,5 +1,5 @@ Copyright (C) 2014-2015 Docker Inc & Go Authors. All rights reserved. -Copyright (C) 2017 SUSE LLC. All rights reserved. +Copyright (C) 2017-2024 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 diff --git a/vendor/github.com/cyphar/filepath-securejoin/README.md b/vendor/github.com/cyphar/filepath-securejoin/README.md index 4eca0f235..253956f86 100644 --- a/vendor/github.com/cyphar/filepath-securejoin/README.md +++ b/vendor/github.com/cyphar/filepath-securejoin/README.md @@ -2,31 +2,24 @@ [![Build Status](https://github.com/cyphar/filepath-securejoin/actions/workflows/ci.yml/badge.svg)](https://github.com/cyphar/filepath-securejoin/actions/workflows/ci.yml) -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`. - -> **NOTE**: This code is *only* safe if you are not at risk of other processes -> modifying path components after you've used `SecureJoin`. If it is possible -> for a malicious process to modify path components of the resolved path, then -> you will be vulnerable to some fairly trivial TOCTOU race conditions. [There -> are some Linux kernel patches I'm working on which might allow for a better -> solution.][lwn-obeneath] -> -> In addition, with a slightly modified API it might be possible to use -> `O_PATH` and verify that the opened path is actually the resolved one -- but -> I have not done that yet. I might add it in the future as a helper function -> to help users verify the path (we can't just return `/proc/self/fd/` -> because that doesn't always work transparently for all users). - -This is the function prototype: +### Old API ### -```go -func SecureJoin(root, unsafePath string) (string, error) -``` +This library was originally just an implementation of `SecureJoin` which was +[intended to be included in the Go standard library][go#20126] as a safer +`filepath.Join` that would restrict the path lookup to be inside a root +directory. + +The implementation was based on code that existed in several container +runtimes. Unfortunately, this API is **fundamentally unsafe** against attackers +that can modify path components after `SecureJoin` returns and before the +caller uses the path, allowing for some fairly trivial TOCTOU attacks. + +`SecureJoin` (and `SecureJoinVFS`) are still provided by this library to +support legacy users, but new users are strongly suggested to avoid using +`SecureJoin` and instead use the [new api](#new-api) or switch to +[libpathrs][libpathrs]. -This library **guarantees** the following: +With the above limitations in mind, this library guarantees the following: * If no error is set, the resulting string **must** be a child path of `root` and will not contain any symlink path components (they will all be @@ -47,7 +40,7 @@ This library **guarantees** the following: 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): +`readlink` is inside the `root` path and is trustworthy): ```go package securejoin @@ -70,9 +63,105 @@ func SecureJoin(root, unsafePath string) (string, error) { } ``` -[lwn-obeneath]: https://lwn.net/Articles/767547/ +[libpathrs]: https://github.com/openSUSE/libpathrs [go#20126]: https://github.com/golang/go/issues/20126 +### New API ### + +While we recommend users switch to [libpathrs][libpathrs] as soon as it has a +stable release, some methods implemented by libpathrs have been ported to this +library to ease the transition. These APIs are only supported on Linux. + +These APIs are implemented such that `filepath-securejoin` will +opportunistically use certain newer kernel APIs that make these operations far +more secure. In particular: + +* All of the lookup operations will use [`openat2`][openat2.2] on new enough + kernels (Linux 5.6 or later) to restrict lookups through magic-links and + bind-mounts (for certain operations) and to make use of `RESOLVE_IN_ROOT` to + efficiently resolve symlinks within a rootfs. + +* The APIs provide hardening against a malicious `/proc` mount to either detect + or avoid being tricked by a `/proc` that is not legitimate. This is done + using [`openat2`][openat2.2] for all users, and privileged users will also be + further protected by using [`fsopen`][fsopen.2] and [`open_tree`][open_tree.2] + (Linux 4.18 or later). + +[openat2.2]: https://www.man7.org/linux/man-pages/man2/openat2.2.html +[fsopen.2]: https://github.com/brauner/man-pages-md/blob/main/fsopen.md +[open_tree.2]: https://github.com/brauner/man-pages-md/blob/main/open_tree.md + +#### `OpenInRoot` #### + +```go +func OpenInRoot(root, unsafePath string) (*os.File, error) +func OpenatInRoot(root *os.File, unsafePath string) (*os.File, error) +func Reopen(handle *os.File, flags int) (*os.File, error) +``` + +`OpenInRoot` is a much safer version of + +```go +path, err := securejoin.SecureJoin(root, unsafePath) +file, err := os.OpenFile(path, unix.O_PATH|unix.O_CLOEXEC) +``` + +that protects against various race attacks that could lead to serious security +issues, depending on the application. Note that the returned `*os.File` is an +`O_PATH` file descriptor, which is quite restricted. Callers will probably need +to use `Reopen` to get a more usable handle (this split is done to provide +useful features like PTY spawning and to avoid users accidentally opening bad +inodes that could cause a DoS). + +Callers need to be careful in how they use the returned `*os.File`. Usually it +is only safe to operate on the handle directly, and it is very easy to create a +security issue. [libpathrs][libpathrs] provides far more helpers to make using +these handles safer -- there is currently no plan to port them to +`filepath-securejoin`. + +`OpenatInRoot` is like `OpenInRoot` except that the root is provided using an +`*os.File`. This allows you to ensure that multiple `OpenatInRoot` (or +`MkdirAllHandle`) calls are operating on the same rootfs. + +> **NOTE**: Unlike `SecureJoin`, `OpenInRoot` will error out as soon as it hits +> a dangling symlink or non-existent path. This is in contrast to `SecureJoin` +> which treated non-existent components as though they were real directories, +> and would allow for partial resolution of dangling symlinks. These behaviours +> are at odds with how Linux treats non-existent paths and dangling symlinks, +> and so these are no longer allowed. + +#### `MkdirAll` #### + +```go +func MkdirAll(root, unsafePath string, mode int) error +func MkdirAllHandle(root *os.File, unsafePath string, mode int) (*os.File, error) +``` + +`MkdirAll` is a much safer version of + +```go +path, err := securejoin.SecureJoin(root, unsafePath) +err = os.MkdirAll(path, mode) +``` + +that protects against the same kinds of races that `OpenInRoot` protects +against. + +`MkdirAllHandle` is like `MkdirAll` except that the root is provided using an +`*os.File` (the reason for this is the same as with `OpenatInRoot`) and an +`*os.File` of the final created directory is returned (this directory is +guaranteed to be effectively identical to the directory created by +`MkdirAllHandle`, which is not possible to ensure by just using `OpenatInRoot` +after `MkdirAll`). + +> **NOTE**: Unlike `SecureJoin`, `MkdirAll` will error out as soon as it hits +> a dangling symlink or non-existent path. This is in contrast to `SecureJoin` +> which treated non-existent components as though they were real directories, +> and would allow for partial resolution of dangling symlinks. These behaviours +> are at odds with how Linux treats non-existent paths and dangling symlinks, +> and so these are no longer allowed. This means that `MkdirAll` will not +> create non-existent directories referenced by a dangling symlink. + ### License ### The license of this project is the same as Go, which is a BSD 3-clause license diff --git a/vendor/github.com/cyphar/filepath-securejoin/VERSION b/vendor/github.com/cyphar/filepath-securejoin/VERSION index 3a4036fb4..0d91a54c7 100644 --- a/vendor/github.com/cyphar/filepath-securejoin/VERSION +++ b/vendor/github.com/cyphar/filepath-securejoin/VERSION @@ -1 +1 @@ -0.2.5 +0.3.0 diff --git a/vendor/github.com/cyphar/filepath-securejoin/join.go b/vendor/github.com/cyphar/filepath-securejoin/join.go index 5ac23b998..bd86a48b0 100644 --- a/vendor/github.com/cyphar/filepath-securejoin/join.go +++ b/vendor/github.com/cyphar/filepath-securejoin/join.go @@ -1,5 +1,5 @@ // Copyright (C) 2014-2015 Docker Inc & Go Authors. All rights reserved. -// Copyright (C) 2017 SUSE LLC. All rights reserved. +// Copyright (C) 2017-2024 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. @@ -41,6 +41,12 @@ func IsNotExist(err error) bool { // replaced with symlinks on the filesystem) after this function has returned. // Such a symlink race is necessarily out-of-scope of SecureJoin. // +// NOTE: Due to the above limitation, Linux users are strongly encouraged to +// use OpenInRoot instead, which does safely protect against these kinds of +// attacks. There is no way to solve this problem with SecureJoinVFS because +// the API is fundamentally wrong (you cannot return a "safe" path string and +// guarantee it won't be modified afterwards). +// // Volume names in unsafePath are always discarded, regardless if they are // provided via direct input or when evaluating symlinks. Therefore: // diff --git a/vendor/github.com/cyphar/filepath-securejoin/lookup_linux.go b/vendor/github.com/cyphar/filepath-securejoin/lookup_linux.go new file mode 100644 index 000000000..140ac18ff --- /dev/null +++ b/vendor/github.com/cyphar/filepath-securejoin/lookup_linux.go @@ -0,0 +1,380 @@ +//go:build linux + +// Copyright (C) 2024 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 ( + "errors" + "fmt" + "os" + "path" + "path/filepath" + "slices" + "strings" + + "golang.org/x/sys/unix" +) + +type symlinkStackEntry struct { + // (dir, remainingPath) is what we would've returned if the link didn't + // exist. This matches what openat2(RESOLVE_IN_ROOT) would return in + // this case. + dir *os.File + remainingPath string + // linkUnwalked is the remaining path components from the original + // Readlink which we have yet to walk. When this slice is empty, we + // drop the link from the stack. + linkUnwalked []string +} + +func (se symlinkStackEntry) String() string { + return fmt.Sprintf("<%s>/%s [->%s]", se.dir.Name(), se.remainingPath, strings.Join(se.linkUnwalked, "/")) +} + +func (se symlinkStackEntry) Close() { + _ = se.dir.Close() +} + +type symlinkStack []*symlinkStackEntry + +func (s symlinkStack) IsEmpty() bool { + return len(s) == 0 +} + +func (s *symlinkStack) Close() { + for _, link := range *s { + link.Close() + } + // TODO: Switch to clear once we switch to Go 1.21. + *s = nil +} + +var ( + errEmptyStack = errors.New("[internal] stack is empty") + errBrokenSymlinkStack = errors.New("[internal error] broken symlink stack") +) + +func (s *symlinkStack) popPart(part string) error { + if s.IsEmpty() { + // If there is nothing in the symlink stack, then the part was from the + // real path provided by the user, and this is a no-op. + return errEmptyStack + } + tailEntry := (*s)[len(*s)-1] + + // Double-check that we are popping the component we expect. + if len(tailEntry.linkUnwalked) == 0 { + return fmt.Errorf("%w: trying to pop component %q of empty stack entry %s", errBrokenSymlinkStack, part, tailEntry) + } + headPart := tailEntry.linkUnwalked[0] + if headPart != part { + return fmt.Errorf("%w: trying to pop component %q but the last stack entry is %s (%q)", errBrokenSymlinkStack, part, tailEntry, headPart) + } + + // Drop the component, but keep the entry around in case we are dealing + // with a "tail-chained" symlink. + tailEntry.linkUnwalked = tailEntry.linkUnwalked[1:] + return nil +} + +func (s *symlinkStack) PopPart(part string) error { + if err := s.popPart(part); err != nil { + if errors.Is(err, errEmptyStack) { + // Skip empty stacks. + err = nil + } + return err + } + + // Clean up any of the trailing stack entries that are empty. + for lastGood := len(*s) - 1; lastGood >= 0; lastGood-- { + entry := (*s)[lastGood] + if len(entry.linkUnwalked) > 0 { + break + } + entry.Close() + (*s) = (*s)[:lastGood] + } + return nil +} + +func (s *symlinkStack) push(dir *os.File, remainingPath, linkTarget string) error { + // Split the link target and clean up any "" parts. + linkTargetParts := slices.DeleteFunc( + strings.Split(linkTarget, "/"), + func(part string) bool { return part == "" }) + + // Don't add a no-op link to the stack. You can't create a no-op link + // symlink, but if the symlink is /, partialLookupInRoot has already jumped to the + // root and so there's nothing more to do. + if len(linkTargetParts) == 0 { + return nil + } + + // Copy the directory so the caller doesn't close our copy. + dirCopy, err := dupFile(dir) + if err != nil { + return err + } + + // Add to the stack. + *s = append(*s, &symlinkStackEntry{ + dir: dirCopy, + remainingPath: remainingPath, + linkUnwalked: linkTargetParts, + }) + return nil +} + +func (s *symlinkStack) SwapLink(linkPart string, dir *os.File, remainingPath, linkTarget string) error { + // If we are currently inside a symlink resolution, remove the symlink + // component from the last symlink entry, but don't remove the entry even + // if it's empty. If we are a "tail-chained" symlink (a trailing symlink we + // hit during a symlink resolution) we need to keep the old symlink until + // we finish the resolution. + if err := s.popPart(linkPart); err != nil { + if !errors.Is(err, errEmptyStack) { + return err + } + // Push the component regardless of whether the stack was empty. + } + return s.push(dir, remainingPath, linkTarget) +} + +func (s *symlinkStack) PopTopSymlink() (*os.File, string, bool) { + if s.IsEmpty() { + return nil, "", false + } + tailEntry := (*s)[0] + *s = (*s)[1:] + return tailEntry.dir, tailEntry.remainingPath, true +} + +// partialLookupInRoot tries to lookup as much of the request path as possible +// within the provided root (a-la RESOLVE_IN_ROOT) and opens the final existing +// component of the requested path, returning a file handle to the final +// existing component and a string containing the remaining path components. +func partialLookupInRoot(root *os.File, unsafePath string) (_ *os.File, _ string, Err error) { + unsafePath = filepath.ToSlash(unsafePath) // noop + + // This is very similar to SecureJoin, except that we operate on the + // components using file descriptors. We then return the last component we + // managed open, along with the remaining path components not opened. + + // Try to use openat2 if possible. + if hasOpenat2() { + return partialLookupOpenat2(root, unsafePath) + } + + // Get the "actual" root path from /proc/self/fd. This is necessary if the + // root is some magic-link like /proc/$pid/root, in which case we want to + // make sure when we do checkProcSelfFdPath that we are using the correct + // root path. + logicalRootPath, err := procSelfFdReadlink(root) + if err != nil { + return nil, "", fmt.Errorf("get real root path: %w", err) + } + + currentDir, err := dupFile(root) + if err != nil { + return nil, "", fmt.Errorf("clone root fd: %w", err) + } + defer func() { + if Err != nil { + _ = currentDir.Close() + } + }() + + // symlinkStack is used to emulate how openat2(RESOLVE_IN_ROOT) treats + // dangling symlinks. If we hit a non-existent path while resolving a + // symlink, we need to return the (dir, remainingPath) that we had when we + // hit the symlink (treating the symlink as though it were a regular file). + // The set of (dir, remainingPath) sets is stored within the symlinkStack + // and we add and remove parts when we hit symlink and non-symlink + // components respectively. We need a stack because of recursive symlinks + // (symlinks that contain symlink components in their target). + // + // Note that the stack is ONLY used for book-keeping. All of the actual + // path walking logic is still based on currentPath/remainingPath and + // currentDir (as in SecureJoin). + var symlinkStack symlinkStack + defer symlinkStack.Close() + + var ( + linksWalked int + currentPath string + remainingPath = unsafePath + ) + for remainingPath != "" { + // Save the current remaining path so if the part is not real we can + // return the path including the component. + oldRemainingPath := remainingPath + + // Get the next path component. + var part string + if i := strings.IndexByte(remainingPath, '/'); i == -1 { + part, remainingPath = remainingPath, "" + } else { + part, remainingPath = remainingPath[:i], remainingPath[i+1:] + } + // Skip any "//" components. + if part == "" { + continue + } + + // Apply the component lexically to the path we are building. + // currentPath does not contain any symlinks, and we are lexically + // dealing with a single component, so it's okay to do a filepath.Clean + // here. + nextPath := path.Join("/", currentPath, part) + // If we logically hit the root, just clone the root rather than + // opening the part and doing all of the other checks. + if nextPath == "/" { + if err := symlinkStack.PopPart(part); err != nil { + return nil, "", fmt.Errorf("walking into root with part %q failed: %w", part, err) + } + // Jump to root. + rootClone, err := dupFile(root) + if err != nil { + return nil, "", fmt.Errorf("clone root fd: %w", err) + } + _ = currentDir.Close() + currentDir = rootClone + currentPath = nextPath + continue + } + + // Try to open the next component. + nextDir, err := openatFile(currentDir, part, unix.O_PATH|unix.O_NOFOLLOW|unix.O_CLOEXEC, 0) + switch { + case err == nil: + st, err := nextDir.Stat() + if err != nil { + _ = nextDir.Close() + return nil, "", fmt.Errorf("stat component %q: %w", part, err) + } + + switch st.Mode() & os.ModeType { + case os.ModeDir: + // If we are dealing with a directory, simply walk into it. + _ = currentDir.Close() + currentDir = nextDir + currentPath = nextPath + + // The part was real, so drop it from the symlink stack. + if err := symlinkStack.PopPart(part); err != nil { + return nil, "", fmt.Errorf("walking into directory %q failed: %w", part, err) + } + + // If we are operating on a .., make sure we haven't escaped. + // We only have to check for ".." here because walking down + // into a regular component component cannot cause you to + // escape. This mirrors the logic in RESOLVE_IN_ROOT, except we + // have to check every ".." rather than only checking after a + // rename or mount on the system. + if part == ".." { + // Make sure the root hasn't moved. + if err := checkProcSelfFdPath(logicalRootPath, root); err != nil { + return nil, "", fmt.Errorf("root path moved during lookup: %w", err) + } + // Make sure the path is what we expect. + fullPath := logicalRootPath + nextPath + if err := checkProcSelfFdPath(fullPath, currentDir); err != nil { + return nil, "", fmt.Errorf("walking into %q had unexpected result: %w", part, err) + } + } + + case os.ModeSymlink: + // We don't need the handle anymore. + _ = nextDir.Close() + + // Unfortunately, we cannot readlink through our handle and so + // we need to do a separate readlinkat (which could race to + // give us an error if the attacker swapped the symlink with a + // non-symlink). + linkDest, err := readlinkatFile(currentDir, part) + if err != nil { + if errors.Is(err, unix.EINVAL) { + // The part was not a symlink, so assume that it's a + // regular file. It is possible for it to be a + // directory (if an attacker is swapping a directory + // and non-directory at this subpath) but erroring out + // here is better anyway. + err = fmt.Errorf("%w: path component %q is invalid: %w", errPossibleAttack, part, unix.ENOTDIR) + } + return nil, "", err + } + + linksWalked++ + if linksWalked > maxSymlinkLimit { + return nil, "", &os.PathError{Op: "partialLookupInRoot", Path: logicalRootPath + "/" + unsafePath, Err: unix.ELOOP} + } + + // Swap out the symlink's component for the link entry itself. + if err := symlinkStack.SwapLink(part, currentDir, oldRemainingPath, linkDest); err != nil { + return nil, "", fmt.Errorf("walking into symlink %q failed: push symlink: %w", part, err) + } + + // Update our logical remaining path. + remainingPath = linkDest + "/" + remainingPath + // Absolute symlinks reset any work we've already done. + if path.IsAbs(linkDest) { + // Jump to root. + rootClone, err := dupFile(root) + if err != nil { + return nil, "", fmt.Errorf("clone root fd: %w", err) + } + _ = currentDir.Close() + currentDir = rootClone + currentPath = "/" + } + default: + // For any other file type, we can't walk further and so we've + // hit the end of the lookup. The handling is very similar to + // ENOENT from openat(2), except that we return a handle to the + // component we just walked into (and we drop the component + // from the symlink stack). + _ = currentDir.Close() + + // The part existed, so drop it from the symlink stack. + if err := symlinkStack.PopPart(part); err != nil { + return nil, "", fmt.Errorf("walking into non-directory %q failed: %w", part, err) + } + + // If there are any remaining components in the symlink stack, + // we are still within a symlink resolution and thus we hit a + // dangling symlink. So pretend that the first symlink in the + // stack we hit was an ENOENT (to match openat2). + if oldDir, remainingPath, ok := symlinkStack.PopTopSymlink(); ok { + _ = nextDir.Close() + return oldDir, remainingPath, nil + } + + // The current component exists, so return it. + return nextDir, remainingPath, nil + } + + case errors.Is(err, os.ErrNotExist): + // If there are any remaining components in the symlink stack, we + // are still within a symlink resolution and thus we hit a dangling + // symlink. So pretend that the first symlink in the stack we hit + // was an ENOENT (to match openat2). + if oldDir, remainingPath, ok := symlinkStack.PopTopSymlink(); ok { + _ = currentDir.Close() + return oldDir, remainingPath, nil + } + // We have hit a final component that doesn't exist, so we have our + // partial open result. Note that we have to use the OLD remaining + // path, since the lookup failed. + return currentDir, oldRemainingPath, nil + + default: + return nil, "", err + } + } + // All of the components existed! + return currentDir, "", nil +} diff --git a/vendor/github.com/cyphar/filepath-securejoin/mkdir_linux.go b/vendor/github.com/cyphar/filepath-securejoin/mkdir_linux.go new file mode 100644 index 000000000..05e0bde9a --- /dev/null +++ b/vendor/github.com/cyphar/filepath-securejoin/mkdir_linux.go @@ -0,0 +1,228 @@ +//go:build linux + +// Copyright (C) 2024 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 ( + "errors" + "fmt" + "io" + "os" + "path/filepath" + "slices" + "strings" + + "golang.org/x/sys/unix" +) + +var ( + errInvalidMode = errors.New("invalid permission mode") + errPossibleAttack = errors.New("possible attack detected") +) + +// MkdirAllHandle is equivalent to MkdirAll, except that it is safer to use in +// two respects: +// +// - The caller provides the root directory as an *os.File (preferably O_PATH) +// handle. This means that the caller can be sure which root directory is +// being used. Note that this can be emulated by using /proc/self/fd/... as +// the root path with MkdirAll. +// +// - Once all of the directories have been created, an *os.File (O_PATH) handle +// to the directory at unsafePath is returned to the caller. This is done in +// an effectively-race-free way (an attacker would only be able to swap the +// final directory component), which is not possible to emulate with +// MkdirAll. +// +// In addition, the returned handle is obtained far more efficiently than doing +// a brand new lookup of unsafePath (such as with SecureJoin or openat2) after +// doing MkdirAll. If you intend to open the directory after creating it, you +// should use MkdirAllHandle. +func MkdirAllHandle(root *os.File, unsafePath string, mode int) (_ *os.File, Err error) { + // Make sure there are no os.FileMode bits set. + if mode&^0o7777 != 0 { + return nil, fmt.Errorf("%w for mkdir 0o%.3o", errInvalidMode, mode) + } + + // Try to open as much of the path as possible. + currentDir, remainingPath, err := partialLookupInRoot(root, unsafePath) + if err != nil { + return nil, fmt.Errorf("find existing subpath of %q: %w", unsafePath, err) + } + defer func() { + if Err != nil { + _ = currentDir.Close() + } + }() + + // If there is an attacker deleting directories as we walk into them, + // detect this proactively. Note this is guaranteed to detect if the + // attacker deleted any part of the tree up to currentDir. + // + // Once we walk into a dead directory, partialLookupInRoot would not be + // able to walk further down the tree (directories must be empty before + // they are deleted), and if the attacker has removed the entire tree we + // can be sure that anything that was originally inside a dead directory + // must also be deleted and thus is a dead directory in its own right. + // + // This is mostly a quality-of-life check, because mkdir will simply fail + // later if the attacker deletes the tree after this check. + if err := isDeadInode(currentDir); err != nil { + return nil, fmt.Errorf("finding existing subpath of %q: %w", unsafePath, err) + } + + // Re-open the path to match the O_DIRECTORY reopen loop later (so that we + // always return a non-O_PATH handle). We also check that we actually got a + // directory. + if reopenDir, err := Reopen(currentDir, unix.O_DIRECTORY|unix.O_CLOEXEC); errors.Is(err, unix.ENOTDIR) { + return nil, fmt.Errorf("cannot create subdirectories in %q: %w", currentDir.Name(), unix.ENOTDIR) + } else if err != nil { + return nil, fmt.Errorf("re-opening handle to %q: %w", currentDir.Name(), err) + } else { + currentDir = reopenDir + } + + remainingParts := strings.Split(remainingPath, string(filepath.Separator)) + if slices.Contains(remainingParts, "..") { + // The path contained ".." components after the end of the "real" + // components. We could try to safely resolve ".." here but that would + // add a bunch of extra logic for something that it's not clear even + // needs to be supported. So just return an error. + // + // If we do filepath.Clean(remainingPath) then we end up with the + // problem that ".." can erase a trailing dangling symlink and produce + // a path that doesn't quite match what the user asked for. + return nil, fmt.Errorf("%w: yet-to-be-created path %q contains '..' components", unix.ENOENT, remainingPath) + } + + // Make sure the mode doesn't have any type bits. + mode &^= unix.S_IFMT + // What properties do we expect any newly created directories to have? + var ( + // While umask(2) is a per-thread property, and thus this value could + // vary between threads, a functioning Go program would LockOSThread + // threads with different umasks and so we don't need to LockOSThread + // for this entire mkdirat loop (if we are in the locked thread with a + // different umask, we are already locked and there's nothing for us to + // do -- and if not then it doesn't matter which thread we run on and + // there's nothing for us to do). + expectedMode = uint32(unix.S_IFDIR | (mode &^ getUmask())) + + // We would want to get the fs[ug]id here, but we can't access those + // from userspace. In practice, nobody uses setfs[ug]id() anymore, so + // just use the effective [ug]id (which is equivalent to the fs[ug]id + // for programs that don't use setfs[ug]id). + expectedUid = uint32(unix.Geteuid()) + expectedGid = uint32(unix.Getegid()) + ) + + // Create the remaining components. + for _, part := range remainingParts { + switch part { + case "", ".": + // Skip over no-op paths. + continue + } + + // NOTE: mkdir(2) will not follow trailing symlinks, so we can safely + // create the finaly component without worrying about symlink-exchange + // attacks. + if err := unix.Mkdirat(int(currentDir.Fd()), part, uint32(mode)); err != nil { + err = &os.PathError{Op: "mkdirat", Path: currentDir.Name() + "/" + part, Err: err} + // Make the error a bit nicer if the directory is dead. + if err2 := isDeadInode(currentDir); err2 != nil { + err = fmt.Errorf("%w (%w)", err, err2) + } + return nil, err + } + + // Get a handle to the next component. O_DIRECTORY means we don't need + // to use O_PATH. + var nextDir *os.File + if hasOpenat2() { + nextDir, err = openat2File(currentDir, part, &unix.OpenHow{ + Flags: unix.O_NOFOLLOW | unix.O_DIRECTORY | unix.O_CLOEXEC, + Resolve: unix.RESOLVE_BENEATH | unix.RESOLVE_NO_SYMLINKS | unix.RESOLVE_NO_XDEV, + }) + } else { + nextDir, err = openatFile(currentDir, part, unix.O_NOFOLLOW|unix.O_DIRECTORY|unix.O_CLOEXEC, 0) + } + if err != nil { + return nil, err + } + _ = currentDir.Close() + currentDir = nextDir + + // Make sure that the directory matches what we expect. An attacker + // could have swapped the directory between us making it and opening + // it. There's no way for us to be sure that the directory is + // _precisely_ the same as the directory we created, but if we are in + // an empty directory with the same owner and mode as the one we + // created then there is nothing the attacker could do with this new + // directory that they couldn't do with the old one. + if stat, err := fstat(currentDir); err != nil { + return nil, fmt.Errorf("check newly created directory: %w", err) + } else { + if stat.Mode != expectedMode { + return nil, fmt.Errorf("%w: newly created directory %q has incorrect mode 0o%.3o (expected 0o%.3o)", errPossibleAttack, currentDir.Name(), stat.Mode, expectedMode) + } + if stat.Uid != expectedUid || stat.Gid != expectedGid { + return nil, fmt.Errorf("%w: newly created directory %q has incorrect owner %d:%d (expected %d:%d)", errPossibleAttack, currentDir.Name(), stat.Uid, stat.Gid, expectedUid, expectedGid) + } + // Check that the directory is empty. We only need to check for + // a single entry, and we should get EOF if the directory is + // empty. + _, err := currentDir.Readdirnames(1) + if !errors.Is(err, io.EOF) { + if err == nil { + err = fmt.Errorf("%w: newly created directory %q is non-empty", errPossibleAttack, currentDir.Name()) + } + return nil, fmt.Errorf("check if newly created directory %q is empty: %w", currentDir.Name(), err) + } + // Reset the offset. + _, _ = currentDir.Seek(0, unix.SEEK_SET) + } + } + return currentDir, nil +} + +// MkdirAll is a race-safe alternative to the Go stdlib's os.MkdirAll function, +// where the new directory is guaranteed to be within the root directory (if an +// attacker can move directories from inside the root to outside the root, the +// created directory tree might be outside of the root but the key constraint +// is that at no point will we walk outside of the directory tree we are +// creating). +// +// Effectively, MkdirAll(root, unsafePath, mode) is equivalent to +// +// path, _ := securejoin.SecureJoin(root, unsafePath) +// err := os.MkdirAll(path, mode) +// +// But is much safer. The above implementation is unsafe because if an attacker +// can modify the filesystem tree between SecureJoin and MkdirAll, it is +// possible for MkdirAll to resolve unsafe symlink components and create +// directories outside of the root. +// +// If you plan to open the directory after you have created it or want to use +// an open directory handle as the root, you should use MkdirAllHandle instead. +// This function is a wrapper around MkdirAllHandle. +// +// NOTE: The mode argument must be set the unix mode bits (unix.S_I...), not +// the Go generic mode bits (os.Mode...). +func MkdirAll(root, unsafePath string, mode int) error { + rootDir, err := os.OpenFile(root, unix.O_PATH|unix.O_DIRECTORY|unix.O_CLOEXEC, 0) + if err != nil { + return err + } + defer rootDir.Close() + + f, err := MkdirAllHandle(rootDir, unsafePath, mode) + if err != nil { + return err + } + _ = f.Close() + return nil +} diff --git a/vendor/github.com/cyphar/filepath-securejoin/open_linux.go b/vendor/github.com/cyphar/filepath-securejoin/open_linux.go new file mode 100644 index 000000000..21700612c --- /dev/null +++ b/vendor/github.com/cyphar/filepath-securejoin/open_linux.go @@ -0,0 +1,83 @@ +//go:build linux + +// Copyright (C) 2024 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 ( + "fmt" + "os" + + "golang.org/x/sys/unix" +) + +// OpenatInRoot is equivalent to OpenInRoot, except that the root is provided +// using an *os.File handle, to ensure that the correct root directory is used. +func OpenatInRoot(root *os.File, unsafePath string) (*os.File, error) { + handle, remainingPath, err := partialLookupInRoot(root, unsafePath) + if err != nil { + return nil, err + } + if remainingPath != "" { + _ = handle.Close() + return nil, &os.PathError{Op: "securejoin.OpenInRoot", Path: unsafePath, Err: unix.ENOENT} + } + return handle, nil +} + +// OpenInRoot safely opens the provided unsafePath within the root. +// Effectively, OpenInRoot(root, unsafePath) is equivalent to +// +// path, _ := securejoin.SecureJoin(root, unsafePath) +// handle, err := os.OpenFile(path, unix.O_PATH|unix.O_CLOEXEC) +// +// But is much safer. The above implementation is unsafe because if an attacker +// can modify the filesystem tree between SecureJoin and OpenFile, it is +// possible for the returned file to be outside of the root. +// +// Note that the returned handle is an O_PATH handle, meaning that only a very +// limited set of operations will work on the handle. This is done to avoid +// accidentally opening an untrusted file that could cause issues (such as a +// disconnected TTY that could cause a DoS, or some other issue). In order to +// use the returned handle, you can "upgrade" it to a proper handle using +// Reopen. +func OpenInRoot(root, unsafePath string) (*os.File, error) { + rootDir, err := os.OpenFile(root, unix.O_PATH|unix.O_DIRECTORY|unix.O_CLOEXEC, 0) + if err != nil { + return nil, err + } + defer rootDir.Close() + return OpenatInRoot(rootDir, unsafePath) +} + +// Reopen takes an *os.File handle and re-opens it through /proc/self/fd. +// Reopen(file, flags) is effectively equivalent to +// +// fdPath := fmt.Sprintf("/proc/self/fd/%d", file.Fd()) +// os.OpenFile(fdPath, flags|unix.O_CLOEXEC) +// +// But with some extra hardenings to ensure that we are not tricked by a +// maliciously-configured /proc mount. While this attack scenario is not +// common, in container runtimes it is possible for higher-level runtimes to be +// tricked into configuring an unsafe /proc that can be used to attack file +// operations. See CVE-2019-19921 for more details. +func Reopen(handle *os.File, flags int) (*os.File, error) { + procRoot, err := getProcRoot() + if err != nil { + return nil, err + } + + flags |= unix.O_CLOEXEC + fdPath := fmt.Sprintf("fd/%d", handle.Fd()) + return doProcSelfMagiclink(procRoot, fdPath, func(procDirHandle *os.File, base string) (*os.File, error) { + // Rather than just wrapping openatFile, open-code it so we can copy + // handle.Name(). + reopenFd, err := unix.Openat(int(procDirHandle.Fd()), base, flags, 0) + if err != nil { + return nil, fmt.Errorf("reopen fd %d: %w", handle.Fd(), err) + } + return os.NewFile(uintptr(reopenFd), handle.Name()), nil + }) +} diff --git a/vendor/github.com/cyphar/filepath-securejoin/openat2_linux.go b/vendor/github.com/cyphar/filepath-securejoin/openat2_linux.go new file mode 100644 index 000000000..fc93db864 --- /dev/null +++ b/vendor/github.com/cyphar/filepath-securejoin/openat2_linux.go @@ -0,0 +1,128 @@ +//go:build linux + +// Copyright (C) 2024 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 ( + "errors" + "fmt" + "os" + "path/filepath" + "strings" + "sync" + "testing" + + "golang.org/x/sys/unix" +) + +var ( + hasOpenat2Bool bool + hasOpenat2Once sync.Once + + testingForceHasOpenat2 *bool +) + +func hasOpenat2() bool { + if testing.Testing() && testingForceHasOpenat2 != nil { + return *testingForceHasOpenat2 + } + hasOpenat2Once.Do(func() { + fd, err := unix.Openat2(unix.AT_FDCWD, ".", &unix.OpenHow{ + Flags: unix.O_PATH | unix.O_CLOEXEC, + Resolve: unix.RESOLVE_NO_SYMLINKS | unix.RESOLVE_IN_ROOT, + }) + if err == nil { + hasOpenat2Bool = true + _ = unix.Close(fd) + } + }) + return hasOpenat2Bool +} + +func scopedLookupShouldRetry(how *unix.OpenHow, err error) bool { + // RESOLVE_IN_ROOT (and RESOLVE_BENEATH) can return -EAGAIN if we resolve + // ".." while a mount or rename occurs anywhere on the system. This could + // happen spuriously, or as the result of an attacker trying to mess with + // us during lookup. + // + // In addition, scoped lookups have a "safety check" at the end of + // complete_walk which will return -EXDEV if the final path is not in the + // root. + return how.Resolve&(unix.RESOLVE_IN_ROOT|unix.RESOLVE_BENEATH) != 0 && + (errors.Is(err, unix.EAGAIN) || errors.Is(err, unix.EXDEV)) +} + +const scopedLookupMaxRetries = 10 + +func openat2File(dir *os.File, path string, how *unix.OpenHow) (*os.File, error) { + fullPath := dir.Name() + "/" + path + // Make sure we always set O_CLOEXEC. + how.Flags |= unix.O_CLOEXEC + var tries int + for tries < scopedLookupMaxRetries { + fd, err := unix.Openat2(int(dir.Fd()), path, how) + if err != nil { + if scopedLookupShouldRetry(how, err) { + // We retry a couple of times to avoid the spurious errors, and + // if we are being attacked then returning -EAGAIN is the best + // we can do. + tries++ + continue + } + return nil, &os.PathError{Op: "openat2", Path: fullPath, Err: err} + } + // If we are using RESOLVE_IN_ROOT, the name we generated may be wrong. + // NOTE: The procRoot code MUST NOT use RESOLVE_IN_ROOT, otherwise + // you'll get infinite recursion here. + if how.Resolve&unix.RESOLVE_IN_ROOT == unix.RESOLVE_IN_ROOT { + if actualPath, err := rawProcSelfFdReadlink(fd); err == nil { + fullPath = actualPath + } + } + return os.NewFile(uintptr(fd), fullPath), nil + } + return nil, &os.PathError{Op: "openat2", Path: fullPath, Err: errPossibleAttack} +} + +// partialLookupOpenat2 is an alternative implementation of +// partialLookupInRoot, using openat2(RESOLVE_IN_ROOT) to more safely get a +// handle to the deepest existing child of the requested path within the root. +func partialLookupOpenat2(root *os.File, unsafePath string) (*os.File, string, error) { + // TODO: Implement this as a git-bisect-like binary search. + + unsafePath = filepath.ToSlash(unsafePath) // noop + endIdx := len(unsafePath) + for endIdx > 0 { + subpath := unsafePath[:endIdx] + + handle, err := openat2File(root, subpath, &unix.OpenHow{ + Flags: unix.O_PATH | unix.O_CLOEXEC, + Resolve: unix.RESOLVE_IN_ROOT | unix.RESOLVE_NO_MAGICLINKS, + }) + if err == nil { + // Jump over the slash if we have a non-"" remainingPath. + if endIdx < len(unsafePath) { + endIdx += 1 + } + // We found a subpath! + return handle, unsafePath[endIdx:], nil + } + if errors.Is(err, unix.ENOENT) || errors.Is(err, unix.ENOTDIR) { + // That path doesn't exist, let's try the next directory up. + endIdx = strings.LastIndexByte(subpath, '/') + continue + } + return nil, "", fmt.Errorf("open subpath: %w", err) + } + // If we couldn't open anything, the whole subpath is missing. Return a + // copy of the root fd so that the caller doesn't close this one by + // accident. + rootClone, err := dupFile(root) + if err != nil { + return nil, "", err + } + return rootClone, unsafePath, nil +} diff --git a/vendor/github.com/cyphar/filepath-securejoin/openat_linux.go b/vendor/github.com/cyphar/filepath-securejoin/openat_linux.go new file mode 100644 index 000000000..949fb5f2d --- /dev/null +++ b/vendor/github.com/cyphar/filepath-securejoin/openat_linux.go @@ -0,0 +1,59 @@ +//go:build linux + +// Copyright (C) 2024 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" + "path/filepath" + + "golang.org/x/sys/unix" +) + +func dupFile(f *os.File) (*os.File, error) { + fd, err := unix.FcntlInt(f.Fd(), unix.F_DUPFD_CLOEXEC, 0) + if err != nil { + return nil, os.NewSyscallError("fcntl(F_DUPFD_CLOEXEC)", err) + } + return os.NewFile(uintptr(fd), f.Name()), nil +} + +func openatFile(dir *os.File, path string, flags int, mode int) (*os.File, error) { + // Make sure we always set O_CLOEXEC. + flags |= unix.O_CLOEXEC + fd, err := unix.Openat(int(dir.Fd()), path, flags, uint32(mode)) + if err != nil { + return nil, &os.PathError{Op: "openat", Path: dir.Name() + "/" + path, Err: err} + } + // All of the paths we use with openatFile(2) are guaranteed to be + // lexically safe, so we can use path.Join here. + fullPath := filepath.Join(dir.Name(), path) + return os.NewFile(uintptr(fd), fullPath), nil +} + +func fstatatFile(dir *os.File, path string, flags int) (unix.Stat_t, error) { + var stat unix.Stat_t + if err := unix.Fstatat(int(dir.Fd()), path, &stat, flags); err != nil { + return stat, &os.PathError{Op: "fstatat", Path: dir.Name() + "/" + path, Err: err} + } + return stat, nil +} + +func readlinkatFile(dir *os.File, path string) (string, error) { + size := 4096 + for { + linkBuf := make([]byte, size) + n, err := unix.Readlinkat(int(dir.Fd()), path, linkBuf) + if err != nil { + return "", &os.PathError{Op: "readlinkat", Path: dir.Name() + "/" + path, Err: err} + } + if n != size { + return string(linkBuf[:n]), nil + } + // Possible truncation, resize the buffer. + size *= 2 + } +} diff --git a/vendor/github.com/cyphar/filepath-securejoin/procfs_linux.go b/vendor/github.com/cyphar/filepath-securejoin/procfs_linux.go new file mode 100644 index 000000000..daac3f061 --- /dev/null +++ b/vendor/github.com/cyphar/filepath-securejoin/procfs_linux.go @@ -0,0 +1,481 @@ +//go:build linux + +// Copyright (C) 2024 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 ( + "errors" + "fmt" + "os" + "path/filepath" + "runtime" + "strconv" + "sync" + + "golang.org/x/sys/unix" +) + +func fstat(f *os.File) (unix.Stat_t, error) { + var stat unix.Stat_t + if err := unix.Fstat(int(f.Fd()), &stat); err != nil { + return stat, &os.PathError{Op: "fstat", Path: f.Name(), Err: err} + } + return stat, nil +} + +func fstatfs(f *os.File) (unix.Statfs_t, error) { + var statfs unix.Statfs_t + if err := unix.Fstatfs(int(f.Fd()), &statfs); err != nil { + return statfs, &os.PathError{Op: "fstatfs", Path: f.Name(), Err: err} + } + return statfs, nil +} + +// The kernel guarantees that the root inode of a procfs mount has an +// f_type of PROC_SUPER_MAGIC and st_ino of PROC_ROOT_INO. +const ( + procSuperMagic = 0x9fa0 // PROC_SUPER_MAGIC + procRootIno = 1 // PROC_ROOT_INO +) + +func verifyProcRoot(procRoot *os.File) error { + if statfs, err := fstatfs(procRoot); err != nil { + return err + } else if statfs.Type != procSuperMagic { + return fmt.Errorf("%w: incorrect procfs root filesystem type 0x%x", errUnsafeProcfs, statfs.Type) + } + if stat, err := fstat(procRoot); err != nil { + return err + } else if stat.Ino != procRootIno { + return fmt.Errorf("%w: incorrect procfs root inode number %d", errUnsafeProcfs, stat.Ino) + } + return nil +} + +var ( + hasNewMountApiBool bool + hasNewMountApiOnce sync.Once +) + +func hasNewMountApi() bool { + hasNewMountApiOnce.Do(func() { + // All of the pieces of the new mount API we use (fsopen, fsconfig, + // fsmount, open_tree) were added together in Linux 5.1[1,2], so we can + // just check for one of the syscalls and the others should also be + // available. + // + // Just try to use open_tree(2) to open a file without OPEN_TREE_CLONE. + // This is equivalent to openat(2), but tells us if open_tree is + // available (and thus all of the other basic new mount API syscalls). + // open_tree(2) is most light-weight syscall to test here. + // + // [1]: merge commit 400913252d09 + // [2]: + fd, err := unix.OpenTree(-int(unix.EBADF), "/", unix.OPEN_TREE_CLOEXEC) + if err == nil { + hasNewMountApiBool = true + _ = unix.Close(fd) + } + }) + return hasNewMountApiBool +} + +func fsopen(fsName string, flags int) (*os.File, error) { + // Make sure we always set O_CLOEXEC. + flags |= unix.FSOPEN_CLOEXEC + fd, err := unix.Fsopen(fsName, flags) + if err != nil { + return nil, os.NewSyscallError("fsopen "+fsName, err) + } + return os.NewFile(uintptr(fd), "fscontext:"+fsName), nil +} + +func fsmount(ctx *os.File, flags, mountAttrs int) (*os.File, error) { + // Make sure we always set O_CLOEXEC. + flags |= unix.FSMOUNT_CLOEXEC + fd, err := unix.Fsmount(int(ctx.Fd()), flags, mountAttrs) + if err != nil { + return nil, os.NewSyscallError("fsmount "+ctx.Name(), err) + } + return os.NewFile(uintptr(fd), "fsmount:"+ctx.Name()), nil +} + +func newPrivateProcMount() (*os.File, error) { + procfsCtx, err := fsopen("proc", unix.FSOPEN_CLOEXEC) + if err != nil { + return nil, err + } + defer procfsCtx.Close() + + // Try to configure hidepid=ptraceable,subset=pid if possible, but ignore errors. + _ = unix.FsconfigSetString(int(procfsCtx.Fd()), "hidepid", "ptraceable") + _ = unix.FsconfigSetString(int(procfsCtx.Fd()), "subset", "pid") + + // Get an actual handle. + if err := unix.FsconfigCreate(int(procfsCtx.Fd())); err != nil { + return nil, os.NewSyscallError("fsconfig create procfs", err) + } + return fsmount(procfsCtx, unix.FSMOUNT_CLOEXEC, unix.MS_RDONLY|unix.MS_NODEV|unix.MS_NOEXEC|unix.MS_NOSUID) +} + +func openTree(dir *os.File, path string, flags uint) (*os.File, error) { + dirFd := -int(unix.EBADF) + dirName := "." + if dir != nil { + dirFd = int(dir.Fd()) + dirName = dir.Name() + } + // Make sure we always set O_CLOEXEC. + flags |= unix.OPEN_TREE_CLOEXEC + fd, err := unix.OpenTree(dirFd, path, flags) + if err != nil { + return nil, &os.PathError{Op: "open_tree", Path: path, Err: err} + } + return os.NewFile(uintptr(fd), dirName+"/"+path), nil +} + +func clonePrivateProcMount() (_ *os.File, Err error) { + // Try to make a clone without using AT_RECURSIVE if we can. If this works, + // we can be sure there are no over-mounts and so if the root is valid then + // we're golden. Otherwise, we have to deal with over-mounts. + procfsHandle, err := openTree(nil, "/proc", unix.OPEN_TREE_CLONE) + if err != nil || testingForcePrivateProcRootOpenTreeAtRecursive(procfsHandle) { + procfsHandle, err = openTree(nil, "/proc", unix.OPEN_TREE_CLONE|unix.AT_RECURSIVE) + } + if err != nil { + return nil, fmt.Errorf("creating a detached procfs clone: %w", err) + } + defer func() { + if Err != nil { + _ = procfsHandle.Close() + } + }() + if err := verifyProcRoot(procfsHandle); err != nil { + return nil, err + } + return procfsHandle, nil +} + +func privateProcRoot() (*os.File, error) { + if !hasNewMountApi() { + return nil, fmt.Errorf("new mount api: %w", unix.ENOTSUP) + } + // Try to create a new procfs mount from scratch if we can. This ensures we + // can get a procfs mount even if /proc is fake (for whatever reason). + procRoot, err := newPrivateProcMount() + if err != nil || testingForcePrivateProcRootOpenTree(procRoot) { + // Try to clone /proc then... + procRoot, err = clonePrivateProcMount() + } + return procRoot, err +} + +var ( + procRootHandle *os.File + procRootError error + procRootOnce sync.Once + + errUnsafeProcfs = errors.New("unsafe procfs detected") +) + +func unsafeHostProcRoot() (_ *os.File, Err error) { + procRoot, err := os.OpenFile("/proc", unix.O_PATH|unix.O_NOFOLLOW|unix.O_DIRECTORY|unix.O_CLOEXEC, 0) + if err != nil { + return nil, err + } + defer func() { + if Err != nil { + _ = procRoot.Close() + } + }() + if err := verifyProcRoot(procRoot); err != nil { + return nil, err + } + return procRoot, nil +} + +func doGetProcRoot() (*os.File, error) { + procRoot, err := privateProcRoot() + if err != nil || testingForceGetProcRootUnsafe(procRoot) { + // Fall back to using a /proc handle if making a private mount failed. + // If we have openat2, at least we can avoid some kinds of over-mount + // attacks, but without openat2 there's not much we can do. + procRoot, err = unsafeHostProcRoot() + } + return procRoot, err +} + +func getProcRoot() (*os.File, error) { + procRootOnce.Do(func() { + procRootHandle, procRootError = doGetProcRoot() + }) + return procRootHandle, procRootError +} + +var ( + haveProcThreadSelf bool + haveProcThreadSelfOnce sync.Once +) + +type procThreadSelfCloser func() + +// procThreadSelf returns a handle to /proc/thread-self/ (or an +// equivalent handle on older kernels where /proc/thread-self doesn't exist). +// Once finished with the handle, you must call the returned closer function +// (runtime.UnlockOSThread). You must not pass the returned *os.File to other +// Go threads or use the handle after calling the closer. +// +// This is similar to ProcThreadSelf from runc, but with extra hardening +// applied and using *os.File. +func procThreadSelf(procRoot *os.File, subpath string) (_ *os.File, _ procThreadSelfCloser, Err error) { + haveProcThreadSelfOnce.Do(func() { + // If the kernel doesn't support thread-self, it doesn't matter which + // /proc handle we use. + _, err := fstatatFile(procRoot, "thread-self", unix.AT_SYMLINK_NOFOLLOW) + haveProcThreadSelf = (err == nil) + }) + + // We need to lock our thread until the caller is done with the handle + // because between getting the handle and using it we could get interrupted + // by the Go runtime and hit the case where the underlying thread is + // swapped out and the original thread is killed, resulting in + // pull-your-hair-out-hard-to-debug issues in the caller. + runtime.LockOSThread() + defer func() { + if Err != nil { + runtime.UnlockOSThread() + } + }() + + // Figure out what prefix we want to use. + threadSelf := "thread-self/" + if !haveProcThreadSelf || testingForceProcSelfTask() { + /// Pre-3.17 kernels don't have /proc/thread-self, so do it manually. + threadSelf = "self/task/" + strconv.Itoa(unix.Gettid()) + "/" + if _, err := fstatatFile(procRoot, threadSelf, unix.AT_SYMLINK_NOFOLLOW); err != nil || testingForceProcSelf() { + // In this case, we running in a pid namespace that doesn't match + // the /proc mount we have. This can happen inside runc. + // + // Unfortunately, there is no nice way to get the correct TID to + // use here because of the age of the kernel, so we have to just + // use /proc/self and hope that it works. + threadSelf = "self/" + } + } + + // Grab the handle. + var ( + handle *os.File + err error + ) + if hasOpenat2() { + // We prefer being able to use RESOLVE_NO_XDEV if we can, to be + // absolutely sure we are operating on a clean /proc handle that + // doesn't have any cheeky overmounts that could trick us (including + // symlink mounts on top of /proc/thread-self). RESOLVE_BENEATH isn't + // stricly needed, but just use it since we have it. + // + // NOTE: /proc/self is technically a magic-link (the contents of the + // symlink are generated dynamically), but it doesn't use + // nd_jump_link() so RESOLVE_NO_MAGICLINKS allows it. + // + // NOTE: We MUST NOT use RESOLVE_IN_ROOT here, as openat2File uses + // procSelfFdReadlink to clean up the returned f.Name() if we use + // RESOLVE_IN_ROOT (which would lead to an infinite recursion). + handle, err = openat2File(procRoot, threadSelf+subpath, &unix.OpenHow{ + Flags: unix.O_PATH | unix.O_CLOEXEC, + Resolve: unix.RESOLVE_BENEATH | unix.RESOLVE_NO_XDEV | unix.RESOLVE_NO_MAGICLINKS, + }) + if err != nil { + return nil, nil, fmt.Errorf("%w: %w", errUnsafeProcfs, err) + } + } else { + handle, err = openatFile(procRoot, threadSelf+subpath, unix.O_PATH|unix.O_CLOEXEC, 0) + if err != nil { + return nil, nil, fmt.Errorf("%w: %w", errUnsafeProcfs, err) + } + defer func() { + if Err != nil { + _ = handle.Close() + } + }() + // We can't detect bind-mounts of different parts of procfs on top of + // /proc (a-la RESOLVE_NO_XDEV), but we can at least be sure that we + // aren't on the wrong filesystem here. + if statfs, err := fstatfs(handle); err != nil { + return nil, nil, err + } else if statfs.Type != procSuperMagic { + return nil, nil, fmt.Errorf("%w: incorrect /proc/self/fd filesystem type 0x%x", errUnsafeProcfs, statfs.Type) + } + } + return handle, runtime.UnlockOSThread, nil +} + +var ( + hasStatxMountIdBool bool + hasStatxMountIdOnce sync.Once +) + +func hasStatxMountId() bool { + hasStatxMountIdOnce.Do(func() { + var ( + stx unix.Statx_t + // We don't care which mount ID we get. The kernel will give us the + // unique one if it is supported. + wantStxMask uint32 = unix.STATX_MNT_ID_UNIQUE | unix.STATX_MNT_ID + ) + err := unix.Statx(-int(unix.EBADF), "/", 0, int(wantStxMask), &stx) + hasStatxMountIdBool = (err == nil && (stx.Mask&wantStxMask != 0)) + }) + return hasStatxMountIdBool +} + +func checkSymlinkOvermount(dir *os.File, path string) error { + // If we don't have statx(STATX_MNT_ID*) support, we can't do anything. + if !hasStatxMountId() { + return nil + } + + var ( + stx unix.Statx_t + // We don't care which mount ID we get. The kernel will give us the + // unique one if it is supported. + wantStxMask uint32 = unix.STATX_MNT_ID_UNIQUE | unix.STATX_MNT_ID + ) + + // Get the mntId of our procfs handle. + err := unix.Statx(int(dir.Fd()), "", unix.AT_EMPTY_PATH, int(wantStxMask), &stx) + if err != nil { + return &os.PathError{Op: "statx", Path: dir.Name(), Err: err} + } + if stx.Mask&wantStxMask == 0 { + // It's not a kernel limitation, for some reason we couldn't get a + // mount ID. Assume it's some kind of attack. + return fmt.Errorf("%w: could not get mnt id of dir %s", errUnsafeProcfs, dir.Name()) + } + expectedMountId := stx.Mnt_id + + // Get the mntId of the target symlink. + stx = unix.Statx_t{} + err = unix.Statx(int(dir.Fd()), path, unix.AT_SYMLINK_NOFOLLOW, int(wantStxMask), &stx) + if err != nil { + return &os.PathError{Op: "statx", Path: dir.Name() + "/" + path, Err: err} + } + if stx.Mask&wantStxMask == 0 { + // It's not a kernel limitation, for some reason we couldn't get a + // mount ID. Assume it's some kind of attack. + return fmt.Errorf("%w: could not get mnt id of symlink %s", errUnsafeProcfs, path) + } + gotMountId := stx.Mnt_id + + // As long as the directory mount is alive, even with wrapping mount IDs, + // we would expect to see a different mount ID here. (Of course, if we're + // using unsafeHostProcRoot() then an attaker could change this after we + // did this check.) + if expectedMountId != gotMountId { + return fmt.Errorf("%w: symlink %s/%s has an overmount obscuring the real link (mount ids do not match %d != %d)", errUnsafeProcfs, dir.Name(), path, expectedMountId, gotMountId) + } + return nil +} + +func doProcSelfMagiclink[T any](procRoot *os.File, subPath string, fn func(procDirHandle *os.File, base string) (T, error)) (T, error) { + // We cannot operate on the magic-link directly with a handle, we need to + // create a handle to the parent of the magic-link and then do + // single-component operations on it. + dir, base := filepath.Dir(subPath), filepath.Base(subPath) + + procDirHandle, closer, err := procThreadSelf(procRoot, dir) + if err != nil { + return *new(T), fmt.Errorf("get safe /proc/thread-self/%s handle: %w", dir, err) + } + defer procDirHandle.Close() + defer closer() + + // Try to detect if there is a mount on top of the symlink we are about to + // read. If we are using unsafeHostProcRoot(), this could change after we + // check it (and there's nothing we can do about that) but for + // privateProcRoot() this should be guaranteed to be safe (at least since + // Linux 5.12[1], when anonymous mount namespaces were completely isolated + // from external mounts including mount propagation events). + // + // [1]: Linux commit ee2e3f50629f ("mount: fix mounting of detached mounts + // onto targets that reside on shared mounts"). + if err := checkSymlinkOvermount(procDirHandle, base); err != nil { + return *new(T), fmt.Errorf("check safety of %s proc magiclink: %w", subPath, err) + } + return fn(procDirHandle, base) +} + +func doRawProcSelfFdReadlink(procRoot *os.File, fd int) (string, error) { + fdPath := fmt.Sprintf("fd/%d", fd) + return doProcSelfMagiclink(procRoot, fdPath, readlinkatFile) +} + +func rawProcSelfFdReadlink(fd int) (string, error) { + procRoot, err := getProcRoot() + if err != nil { + return "", err + } + return doRawProcSelfFdReadlink(procRoot, fd) +} + +func procSelfFdReadlink(f *os.File) (string, error) { + return rawProcSelfFdReadlink(int(f.Fd())) +} + +var ( + errPossibleBreakout = errors.New("possible breakout detected") + errInvalidDirectory = errors.New("wandered into deleted directory") + errDeletedInode = errors.New("cannot verify path of deleted inode") +) + +func isDeadInode(file *os.File) error { + // If the nlink of a file drops to 0, there is an attacker deleting + // directories during our walk, which could result in weird /proc values. + // It's better to error out in this case. + stat, err := fstat(file) + if err != nil { + return fmt.Errorf("check for dead inode: %w", err) + } + if stat.Nlink == 0 { + err := errDeletedInode + if stat.Mode&unix.S_IFMT == unix.S_IFDIR { + err = errInvalidDirectory + } + return fmt.Errorf("%w %q", err, file.Name()) + } + return nil +} + +func getUmask() int { + // umask is a per-thread property, but it is inherited by children, so we + // need to lock our OS thread to make sure that no other goroutine runs in + // this thread and no goroutines are spawned from this thread until we + // revert to the old umask. + // + // We could parse /proc/self/status to avoid this get-set problem, but + // /proc/thread-self requires LockOSThread anyway, so there's no real + // benefit over just using umask(2). + runtime.LockOSThread() + umask := unix.Umask(0) + unix.Umask(umask) + runtime.UnlockOSThread() + return umask +} + +func checkProcSelfFdPath(path string, file *os.File) error { + if err := isDeadInode(file); err != nil { + return err + } + actualPath, err := procSelfFdReadlink(file) + if err != nil { + return fmt.Errorf("get path of handle: %w", err) + } + if actualPath != path { + return fmt.Errorf("%w: handle path %q doesn't match expected path %q", errPossibleBreakout, actualPath, path) + } + return nil +} diff --git a/vendor/github.com/cyphar/filepath-securejoin/testing_mocks_linux.go b/vendor/github.com/cyphar/filepath-securejoin/testing_mocks_linux.go new file mode 100644 index 000000000..2a25d08e3 --- /dev/null +++ b/vendor/github.com/cyphar/filepath-securejoin/testing_mocks_linux.go @@ -0,0 +1,68 @@ +//go:build linux + +// Copyright (C) 2024 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" + "testing" +) + +type forceGetProcRootLevel int + +const ( + forceGetProcRootDefault forceGetProcRootLevel = iota + forceGetProcRootOpenTree // force open_tree() + forceGetProcRootOpenTreeAtRecursive // force open_tree(AT_RECURSIVE) + forceGetProcRootUnsafe // force open() +) + +var testingForceGetProcRoot *forceGetProcRootLevel + +func testingCheckClose(check bool, f *os.File) bool { + if check { + if f != nil { + _ = f.Close() + } + return true + } + return false +} + +func testingForcePrivateProcRootOpenTree(f *os.File) bool { + return testing.Testing() && testingForceGetProcRoot != nil && + testingCheckClose(*testingForceGetProcRoot >= forceGetProcRootOpenTree, f) +} + +func testingForcePrivateProcRootOpenTreeAtRecursive(f *os.File) bool { + return testing.Testing() && testingForceGetProcRoot != nil && + testingCheckClose(*testingForceGetProcRoot >= forceGetProcRootOpenTreeAtRecursive, f) +} + +func testingForceGetProcRootUnsafe(f *os.File) bool { + return testing.Testing() && testingForceGetProcRoot != nil && + testingCheckClose(*testingForceGetProcRoot >= forceGetProcRootUnsafe, f) +} + +type forceProcThreadSelfLevel int + +const ( + forceProcThreadSelfDefault forceProcThreadSelfLevel = iota + forceProcSelfTask + forceProcSelf +) + +var testingForceProcThreadSelf *forceProcThreadSelfLevel + +func testingForceProcSelfTask() bool { + return testing.Testing() && testingForceProcThreadSelf != nil && + *testingForceProcThreadSelf >= forceProcSelfTask +} + +func testingForceProcSelf() bool { + return testing.Testing() && testingForceProcThreadSelf != nil && + *testingForceProcThreadSelf >= forceProcSelf +} diff --git a/vendor/github.com/cyphar/filepath-securejoin/vfs.go b/vendor/github.com/cyphar/filepath-securejoin/vfs.go index a82a5eae1..6e27c7dd8 100644 --- a/vendor/github.com/cyphar/filepath-securejoin/vfs.go +++ b/vendor/github.com/cyphar/filepath-securejoin/vfs.go @@ -1,4 +1,4 @@ -// Copyright (C) 2017 SUSE LLC. All rights reserved. +// Copyright (C) 2017-2024 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. diff --git a/vendor/modules.txt b/vendor/modules.txt index f46ccb275..9972afb31 100644 --- a/vendor/modules.txt +++ b/vendor/modules.txt @@ -242,8 +242,8 @@ github.com/coreos/go-systemd/v22/dbus # github.com/cyberphone/json-canonicalization v0.0.0-20231217050601-ba74d44ecf5f ## explicit github.com/cyberphone/json-canonicalization/go/src/webpki.org/jsoncanonicalizer -# github.com/cyphar/filepath-securejoin v0.2.5 -## explicit; go 1.13 +# github.com/cyphar/filepath-securejoin v0.3.0 +## explicit; go 1.20 github.com/cyphar/filepath-securejoin # github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc ## explicit