diff options
Diffstat (limited to 'runsc')
| -rw-r--r-- | runsc/boot/BUILD | 5 | ||||
| -rw-r--r-- | runsc/boot/loader.go | 7 | ||||
| -rw-r--r-- | runsc/boot/user.go | 234 | ||||
| -rw-r--r-- | runsc/boot/user_test.go | 254 |
4 files changed, 5 insertions, 495 deletions
diff --git a/runsc/boot/BUILD b/runsc/boot/BUILD index 5451f1eba..72c2fe381 100644 --- a/runsc/boot/BUILD +++ b/runsc/boot/BUILD @@ -20,7 +20,6 @@ go_library( "loader_arm64.go", "network.go", "strace.go", - "user.go", "vfs.go", ], visibility = [ @@ -52,6 +51,7 @@ go_library( "//pkg/sentry/fs/sys", "//pkg/sentry/fs/tmpfs", "//pkg/sentry/fs/tty", + "//pkg/sentry/fs/user", "//pkg/sentry/fsimpl/devtmpfs", "//pkg/sentry/fsimpl/gofer", "//pkg/sentry/fsimpl/host", @@ -97,7 +97,6 @@ go_library( "//pkg/tcpip/transport/tcp", "//pkg/tcpip/transport/udp", "//pkg/urpc", - "//pkg/usermem", "//runsc/boot/filter", "//runsc/boot/platforms", "//runsc/boot/pprof", @@ -115,7 +114,6 @@ go_test( "compat_test.go", "fs_test.go", "loader_test.go", - "user_test.go", ], library = ":boot", deps = [ @@ -125,7 +123,6 @@ go_test( "//pkg/sentry/contexttest", "//pkg/sentry/fs", "//pkg/sentry/kernel", - "//pkg/sentry/kernel/auth", "//pkg/sync", "//pkg/unet", "//runsc/fsgofer", diff --git a/runsc/boot/loader.go b/runsc/boot/loader.go index cf1f47bc7..096b0e9f0 100644 --- a/runsc/boot/loader.go +++ b/runsc/boot/loader.go @@ -35,6 +35,7 @@ import ( "gvisor.dev/gvisor/pkg/sentry/control" "gvisor.dev/gvisor/pkg/sentry/fs" "gvisor.dev/gvisor/pkg/sentry/fs/host" + "gvisor.dev/gvisor/pkg/sentry/fs/user" "gvisor.dev/gvisor/pkg/sentry/inet" "gvisor.dev/gvisor/pkg/sentry/kernel" "gvisor.dev/gvisor/pkg/sentry/kernel/auth" @@ -550,11 +551,11 @@ func (l *Loader) run() error { // Add the HOME enviroment variable if it is not already set. var envv []string if kernel.VFS2Enabled { - envv, err = maybeAddExecUserHomeVFS2(ctx, l.rootProcArgs.MountNamespaceVFS2, + envv, err = user.MaybeAddExecUserHomeVFS2(ctx, l.rootProcArgs.MountNamespaceVFS2, l.rootProcArgs.Credentials.RealKUID, l.rootProcArgs.Envv) } else { - envv, err = maybeAddExecUserHome(ctx, l.rootProcArgs.MountNamespace, + envv, err = user.MaybeAddExecUserHome(ctx, l.rootProcArgs.MountNamespace, l.rootProcArgs.Credentials.RealKUID, l.rootProcArgs.Envv) } if err != nil { @@ -860,7 +861,7 @@ func (l *Loader) executeAsync(args *control.ExecArgs) (kernel.ThreadID, error) { root := args.MountNamespace.Root() defer root.DecRef() ctx := fs.WithRoot(l.k.SupervisorContext(), root) - envv, err := maybeAddExecUserHome(ctx, args.MountNamespace, args.KUID, args.Envv) + envv, err := user.MaybeAddExecUserHome(ctx, args.MountNamespace, args.KUID, args.Envv) if err != nil { return 0, err } diff --git a/runsc/boot/user.go b/runsc/boot/user.go deleted file mode 100644 index 332e4fce5..000000000 --- a/runsc/boot/user.go +++ /dev/null @@ -1,234 +0,0 @@ -// Copyright 2019 The gVisor Authors. -// -// 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 -// -// http://www.apache.org/licenses/LICENSE-2.0 -// -// Unless required by applicable law or agreed to in writing, software -// distributed under the License is distributed on an "AS IS" BASIS, -// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -// See the License for the specific language governing permissions and -// limitations under the License. - -package boot - -import ( - "bufio" - "fmt" - "io" - "strconv" - "strings" - - "gvisor.dev/gvisor/pkg/abi/linux" - "gvisor.dev/gvisor/pkg/context" - "gvisor.dev/gvisor/pkg/fspath" - "gvisor.dev/gvisor/pkg/sentry/fs" - "gvisor.dev/gvisor/pkg/sentry/kernel/auth" - "gvisor.dev/gvisor/pkg/sentry/vfs" - "gvisor.dev/gvisor/pkg/usermem" -) - -type fileReader struct { - // Ctx is the context for the file reader. - Ctx context.Context - - // File is the file to read from. - File *fs.File -} - -// Read implements io.Reader.Read. -func (r *fileReader) Read(buf []byte) (int, error) { - n, err := r.File.Readv(r.Ctx, usermem.BytesIOSequence(buf)) - return int(n), err -} - -// getExecUserHome returns the home directory of the executing user read from -// /etc/passwd as read from the container filesystem. -func getExecUserHome(ctx context.Context, rootMns *fs.MountNamespace, uid auth.KUID) (string, error) { - // The default user home directory to return if no user matching the user - // if found in the /etc/passwd found in the image. - const defaultHome = "/" - - // Open the /etc/passwd file from the dirent via the root mount namespace. - mnsRoot := rootMns.Root() - maxTraversals := uint(linux.MaxSymlinkTraversals) - dirent, err := rootMns.FindInode(ctx, mnsRoot, nil, "/etc/passwd", &maxTraversals) - if err != nil { - // NOTE: Ignore errors opening the passwd file. If the passwd file - // doesn't exist we will return the default home directory. - return defaultHome, nil - } - defer dirent.DecRef() - - // Check read permissions on the file. - if err := dirent.Inode.CheckPermission(ctx, fs.PermMask{Read: true}); err != nil { - // NOTE: Ignore permissions errors here and return default root dir. - return defaultHome, nil - } - - // Only open regular files. We don't open other files like named pipes as - // they may block and might present some attack surface to the container. - // Note that runc does not seem to do this kind of checking. - if !fs.IsRegular(dirent.Inode.StableAttr) { - return defaultHome, nil - } - - f, err := dirent.Inode.GetFile(ctx, dirent, fs.FileFlags{Read: true, Directory: false}) - if err != nil { - return "", err - } - defer f.DecRef() - - r := &fileReader{ - Ctx: ctx, - File: f, - } - - return findHomeInPasswd(uint32(uid), r, defaultHome) -} - -type fileReaderVFS2 struct { - ctx context.Context - fd *vfs.FileDescription -} - -func (r *fileReaderVFS2) Read(buf []byte) (int, error) { - n, err := r.fd.Read(r.ctx, usermem.BytesIOSequence(buf), vfs.ReadOptions{}) - return int(n), err -} - -func getExecUserHomeVFS2(ctx context.Context, mns *vfs.MountNamespace, uid auth.KUID) (string, error) { - const defaultHome = "/" - - root := mns.Root() - defer root.DecRef() - - creds := auth.CredentialsFromContext(ctx) - - target := &vfs.PathOperation{ - Root: root, - Start: root, - Path: fspath.Parse("/etc/passwd"), - } - - opts := &vfs.OpenOptions{ - Flags: linux.O_RDONLY, - } - - fd, err := root.Mount().Filesystem().VirtualFilesystem().OpenAt(ctx, creds, target, opts) - if err != nil { - return defaultHome, nil - } - defer fd.DecRef() - - r := &fileReaderVFS2{ - ctx: ctx, - fd: fd, - } - - homeDir, err := findHomeInPasswd(uint32(uid), r, defaultHome) - if err != nil { - return "", err - } - - return homeDir, nil -} - -// maybeAddExecUserHome returns a new slice with the HOME enviroment variable -// set if the slice does not already contain it, otherwise it returns the -// original slice unmodified. -func maybeAddExecUserHome(ctx context.Context, mns *fs.MountNamespace, uid auth.KUID, envv []string) ([]string, error) { - // Check if the envv already contains HOME. - for _, env := range envv { - if strings.HasPrefix(env, "HOME=") { - // We have it. Return the original slice unmodified. - return envv, nil - } - } - - // Read /etc/passwd for the user's HOME directory and set the HOME - // environment variable as required by POSIX if it is not overridden by - // the user. - homeDir, err := getExecUserHome(ctx, mns, uid) - if err != nil { - return nil, fmt.Errorf("error reading exec user: %v", err) - } - - return append(envv, "HOME="+homeDir), nil -} - -func maybeAddExecUserHomeVFS2(ctx context.Context, vmns *vfs.MountNamespace, uid auth.KUID, envv []string) ([]string, error) { - // Check if the envv already contains HOME. - for _, env := range envv { - if strings.HasPrefix(env, "HOME=") { - // We have it. Return the original slice unmodified. - return envv, nil - } - } - - // Read /etc/passwd for the user's HOME directory and set the HOME - // environment variable as required by POSIX if it is not overridden by - // the user. - homeDir, err := getExecUserHomeVFS2(ctx, vmns, uid) - if err != nil { - return nil, fmt.Errorf("error reading exec user: %v", err) - } - return append(envv, "HOME="+homeDir), nil -} - -// findHomeInPasswd parses a passwd file and returns the given user's home -// directory. This function does it's best to replicate the runc's behavior. -func findHomeInPasswd(uid uint32, passwd io.Reader, defaultHome string) (string, error) { - s := bufio.NewScanner(passwd) - - for s.Scan() { - if err := s.Err(); err != nil { - return "", err - } - - line := strings.TrimSpace(s.Text()) - if line == "" { - continue - } - - // Pull out part of passwd entry. Loosely parse the passwd entry as some - // passwd files could be poorly written and for compatibility with runc. - // - // Per 'man 5 passwd' - // /etc/passwd contains one line for each user account, with seven - // fields delimited by colons (“:”). These fields are: - // - // - login name - // - optional encrypted password - // - numerical user ID - // - numerical group ID - // - user name or comment field - // - user home directory - // - optional user command interpreter - parts := strings.Split(line, ":") - - found := false - homeDir := "" - for i, p := range parts { - switch i { - case 2: - parsedUID, err := strconv.ParseUint(p, 10, 32) - if err == nil && parsedUID == uint64(uid) { - found = true - } - case 5: - homeDir = p - } - } - if found { - // NOTE: If the uid is present but the home directory is not - // present in the /etc/passwd entry we return an empty string. This - // is, for better or worse, what runc does. - return homeDir, nil - } - } - - return defaultHome, nil -} diff --git a/runsc/boot/user_test.go b/runsc/boot/user_test.go deleted file mode 100644 index fb4e13dfb..000000000 --- a/runsc/boot/user_test.go +++ /dev/null @@ -1,254 +0,0 @@ -// Copyright 2019 The gVisor Authors. -// -// 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 -// -// http://www.apache.org/licenses/LICENSE-2.0 -// -// Unless required by applicable law or agreed to in writing, software -// distributed under the License is distributed on an "AS IS" BASIS, -// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -// See the License for the specific language governing permissions and -// limitations under the License. - -package boot - -import ( - "io/ioutil" - "os" - "path/filepath" - "strings" - "syscall" - "testing" - - specs "github.com/opencontainers/runtime-spec/specs-go" - "gvisor.dev/gvisor/pkg/sentry/contexttest" - "gvisor.dev/gvisor/pkg/sentry/fs" - "gvisor.dev/gvisor/pkg/sentry/kernel/auth" -) - -func setupTempDir() (string, error) { - tmpDir, err := ioutil.TempDir(os.TempDir(), "exec-user-test") - if err != nil { - return "", err - } - return tmpDir, nil -} - -func setupPasswd(contents string, perms os.FileMode) func() (string, error) { - return func() (string, error) { - tmpDir, err := setupTempDir() - if err != nil { - return "", err - } - - if err := os.Mkdir(filepath.Join(tmpDir, "etc"), 0777); err != nil { - return "", err - } - - f, err := os.Create(filepath.Join(tmpDir, "etc", "passwd")) - if err != nil { - return "", err - } - defer f.Close() - - _, err = f.WriteString(contents) - if err != nil { - return "", err - } - - err = f.Chmod(perms) - if err != nil { - return "", err - } - return tmpDir, nil - } -} - -// TestGetExecUserHome tests the getExecUserHome function. -func TestGetExecUserHome(t *testing.T) { - tests := map[string]struct { - uid auth.KUID - createRoot func() (string, error) - expected string - }{ - "success": { - uid: 1000, - createRoot: setupPasswd("adin::1000:1111::/home/adin:/bin/sh", 0666), - expected: "/home/adin", - }, - "no_passwd": { - uid: 1000, - createRoot: setupTempDir, - expected: "/", - }, - "no_perms": { - uid: 1000, - createRoot: setupPasswd("adin::1000:1111::/home/adin:/bin/sh", 0000), - expected: "/", - }, - "directory": { - uid: 1000, - createRoot: func() (string, error) { - tmpDir, err := setupTempDir() - if err != nil { - return "", err - } - - if err := os.Mkdir(filepath.Join(tmpDir, "etc"), 0777); err != nil { - return "", err - } - - if err := syscall.Mkdir(filepath.Join(tmpDir, "etc", "passwd"), 0666); err != nil { - return "", err - } - - return tmpDir, nil - }, - expected: "/", - }, - // Currently we don't allow named pipes. - "named_pipe": { - uid: 1000, - createRoot: func() (string, error) { - tmpDir, err := setupTempDir() - if err != nil { - return "", err - } - - if err := os.Mkdir(filepath.Join(tmpDir, "etc"), 0777); err != nil { - return "", err - } - - if err := syscall.Mkfifo(filepath.Join(tmpDir, "etc", "passwd"), 0666); err != nil { - return "", err - } - - return tmpDir, nil - }, - expected: "/", - }, - } - - for name, tc := range tests { - t.Run(name, func(t *testing.T) { - tmpDir, err := tc.createRoot() - if err != nil { - t.Fatalf("failed to create root dir: %v", err) - } - - sandEnd, cleanup, err := startGofer(tmpDir) - if err != nil { - t.Fatalf("failed to create gofer: %v", err) - } - defer cleanup() - - ctx := contexttest.Context(t) - conf := &Config{ - RootDir: "unused_root_dir", - Network: NetworkNone, - DisableSeccomp: true, - } - - spec := &specs.Spec{ - Root: &specs.Root{ - Path: tmpDir, - Readonly: true, - }, - // Add /proc mount as tmpfs to avoid needing a kernel. - Mounts: []specs.Mount{ - { - Destination: "/proc", - Type: "tmpfs", - }, - }, - } - - mntr := newContainerMounter(spec, []int{sandEnd}, nil, &podMountHints{}) - mns, err := mntr.createMountNamespace(ctx, conf) - if err != nil { - t.Fatalf("failed to create mount namespace: %v", err) - } - ctx = fs.WithRoot(ctx, mns.Root()) - if err := mntr.mountSubmounts(ctx, conf, mns); err != nil { - t.Fatalf("failed to create mount namespace: %v", err) - } - - got, err := getExecUserHome(ctx, mns, tc.uid) - if err != nil { - t.Fatalf("failed to get user home: %v", err) - } - - if got != tc.expected { - t.Fatalf("expected %v, got: %v", tc.expected, got) - } - }) - } -} - -// TestFindHomeInPasswd tests the findHomeInPasswd function's passwd file parsing. -func TestFindHomeInPasswd(t *testing.T) { - tests := map[string]struct { - uid uint32 - passwd string - expected string - def string - }{ - "empty": { - uid: 1000, - passwd: "", - expected: "/", - def: "/", - }, - "whitespace": { - uid: 1000, - passwd: " ", - expected: "/", - def: "/", - }, - "full": { - uid: 1000, - passwd: "adin::1000:1111::/home/adin:/bin/sh", - expected: "/home/adin", - def: "/", - }, - // For better or worse, this is how runc works. - "partial": { - uid: 1000, - passwd: "adin::1000:1111:", - expected: "", - def: "/", - }, - "multiple": { - uid: 1001, - passwd: "adin::1000:1111::/home/adin:/bin/sh\nian::1001:1111::/home/ian:/bin/sh", - expected: "/home/ian", - def: "/", - }, - "duplicate": { - uid: 1000, - passwd: "adin::1000:1111::/home/adin:/bin/sh\nian::1000:1111::/home/ian:/bin/sh", - expected: "/home/adin", - def: "/", - }, - "empty_lines": { - uid: 1001, - passwd: "adin::1000:1111::/home/adin:/bin/sh\n\n\nian::1001:1111::/home/ian:/bin/sh", - expected: "/home/ian", - def: "/", - }, - } - - for name, tc := range tests { - t.Run(name, func(t *testing.T) { - got, err := findHomeInPasswd(tc.uid, strings.NewReader(tc.passwd), tc.def) - if err != nil { - t.Fatalf("error parsing passwd: %v", err) - } - if tc.expected != got { - t.Fatalf("expected %v, got: %v", tc.expected, got) - } - }) - } -} |