From 43a123c1ae6613b3efeed291fa552ecd909d3acf Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Tue, 16 Apr 2024 21:23:18 +0200 Subject: Adding upstream version 1.20.14. Signed-off-by: Daniel Baumann --- src/syscall/exec_linux_test.go | 733 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 733 insertions(+) create mode 100644 src/syscall/exec_linux_test.go (limited to 'src/syscall/exec_linux_test.go') diff --git a/src/syscall/exec_linux_test.go b/src/syscall/exec_linux_test.go new file mode 100644 index 0000000..a6900f9 --- /dev/null +++ b/src/syscall/exec_linux_test.go @@ -0,0 +1,733 @@ +// Copyright 2015 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. + +//go:build linux + +package syscall_test + +import ( + "bytes" + "errors" + "flag" + "fmt" + "internal/testenv" + "io" + "os" + "os/exec" + "os/user" + "path" + "path/filepath" + "runtime" + "strconv" + "strings" + "syscall" + "testing" + "unsafe" +) + +func isDocker() bool { + _, err := os.Stat("/.dockerenv") + return err == nil +} + +func isLXC() bool { + return os.Getenv("container") == "lxc" +} + +func skipInContainer(t *testing.T) { + // TODO: the callers of this func are using this func to skip + // tests when running as some sort of "fake root" that's uid 0 + // but lacks certain Linux capabilities. Most of the Go builds + // run in privileged containers, though, where root is much + // closer (if not identical) to the real root. We should test + // for what we need exactly (which capabilities are active?), + // instead of just assuming "docker == bad". Then we'd get more test + // coverage on a bunch of builders too. + if isDocker() { + t.Skip("skip this test in Docker container") + } + if isLXC() { + t.Skip("skip this test in LXC container") + } +} + +func skipNoUserNamespaces(t *testing.T) { + if _, err := os.Stat("/proc/self/ns/user"); err != nil { + if os.IsNotExist(err) { + t.Skip("kernel doesn't support user namespaces") + } + if os.IsPermission(err) { + t.Skip("unable to test user namespaces due to permissions") + } + t.Fatalf("Failed to stat /proc/self/ns/user: %v", err) + } +} + +func skipUnprivilegedUserClone(t *testing.T) { + // Skip the test if the sysctl that prevents unprivileged user + // from creating user namespaces is enabled. + data, errRead := os.ReadFile("/proc/sys/kernel/unprivileged_userns_clone") + if os.IsNotExist(errRead) { + // This file is only available in some Debian/Ubuntu kernels. + return + } + if errRead != nil || len(data) < 1 || data[0] == '0' { + t.Skip("kernel prohibits user namespace in unprivileged process") + } +} + +// Check if we are in a chroot by checking if the inode of / is +// different from 2 (there is no better test available to non-root on +// linux). +func isChrooted(t *testing.T) bool { + root, err := os.Stat("/") + if err != nil { + t.Fatalf("cannot stat /: %v", err) + } + return root.Sys().(*syscall.Stat_t).Ino != 2 +} + +func checkUserNS(t *testing.T) { + skipInContainer(t) + skipNoUserNamespaces(t) + if isChrooted(t) { + // create_user_ns in the kernel (see + // https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/kernel/user_namespace.c) + // forbids the creation of user namespaces when chrooted. + t.Skip("cannot create user namespaces when chrooted") + } + // On some systems, there is a sysctl setting. + if os.Getuid() != 0 { + skipUnprivilegedUserClone(t) + } + // On Centos 7 make sure they set the kernel parameter user_namespace=1 + // See issue 16283 and 20796. + if _, err := os.Stat("/sys/module/user_namespace/parameters/enable"); err == nil { + buf, _ := os.ReadFile("/sys/module/user_namespace/parameters/enabled") + if !strings.HasPrefix(string(buf), "Y") { + t.Skip("kernel doesn't support user namespaces") + } + } + + // On Centos 7.5+, user namespaces are disabled if user.max_user_namespaces = 0 + if _, err := os.Stat("/proc/sys/user/max_user_namespaces"); err == nil { + buf, errRead := os.ReadFile("/proc/sys/user/max_user_namespaces") + if errRead == nil && buf[0] == '0' { + t.Skip("kernel doesn't support user namespaces") + } + } +} + +func whoamiCmd(t *testing.T, uid, gid int, setgroups bool) *exec.Cmd { + checkUserNS(t) + cmd := exec.Command("whoami") + cmd.SysProcAttr = &syscall.SysProcAttr{ + Cloneflags: syscall.CLONE_NEWUSER, + UidMappings: []syscall.SysProcIDMap{ + {ContainerID: 0, HostID: uid, Size: 1}, + }, + GidMappings: []syscall.SysProcIDMap{ + {ContainerID: 0, HostID: gid, Size: 1}, + }, + GidMappingsEnableSetgroups: setgroups, + } + return cmd +} + +func testNEWUSERRemap(t *testing.T, uid, gid int, setgroups bool) { + cmd := whoamiCmd(t, uid, gid, setgroups) + out, err := cmd.CombinedOutput() + if err != nil { + t.Fatalf("Cmd failed with err %v, output: %s", err, out) + } + sout := strings.TrimSpace(string(out)) + want := "root" + if sout != want { + t.Fatalf("whoami = %q; want %q", out, want) + } +} + +func TestCloneNEWUSERAndRemapRootDisableSetgroups(t *testing.T) { + if os.Getuid() != 0 { + t.Skip("skipping root only test") + } + testNEWUSERRemap(t, 0, 0, false) +} + +func TestCloneNEWUSERAndRemapRootEnableSetgroups(t *testing.T) { + if os.Getuid() != 0 { + t.Skip("skipping root only test") + } + testNEWUSERRemap(t, 0, 0, true) +} + +func TestCloneNEWUSERAndRemapNoRootDisableSetgroups(t *testing.T) { + if os.Getuid() == 0 { + t.Skip("skipping unprivileged user only test") + } + testNEWUSERRemap(t, os.Getuid(), os.Getgid(), false) +} + +func TestCloneNEWUSERAndRemapNoRootSetgroupsEnableSetgroups(t *testing.T) { + if os.Getuid() == 0 { + t.Skip("skipping unprivileged user only test") + } + cmd := whoamiCmd(t, os.Getuid(), os.Getgid(), true) + err := cmd.Run() + if err == nil { + t.Skip("probably old kernel without security fix") + } + if !os.IsPermission(err) { + t.Fatalf("Unprivileged gid_map rewriting with GidMappingsEnableSetgroups must fail") + } +} + +func TestEmptyCredGroupsDisableSetgroups(t *testing.T) { + cmd := whoamiCmd(t, os.Getuid(), os.Getgid(), false) + cmd.SysProcAttr.Credential = &syscall.Credential{} + if err := cmd.Run(); err != nil { + t.Fatal(err) + } +} + +func TestUnshare(t *testing.T) { + skipInContainer(t) + // Make sure we are running as root so we have permissions to use unshare + // and create a network namespace. + if os.Getuid() != 0 { + t.Skip("kernel prohibits unshare in unprivileged process, unless using user namespace") + } + + path := "/proc/net/dev" + if _, err := os.Stat(path); err != nil { + if os.IsNotExist(err) { + t.Skip("kernel doesn't support proc filesystem") + } + if os.IsPermission(err) { + t.Skip("unable to test proc filesystem due to permissions") + } + t.Fatal(err) + } + if _, err := os.Stat("/proc/self/ns/net"); err != nil { + if os.IsNotExist(err) { + t.Skip("kernel doesn't support net namespace") + } + t.Fatal(err) + } + + orig, err := os.ReadFile(path) + if err != nil { + t.Fatal(err) + } + origLines := strings.Split(strings.TrimSpace(string(orig)), "\n") + + cmd := exec.Command("cat", path) + cmd.SysProcAttr = &syscall.SysProcAttr{ + Unshareflags: syscall.CLONE_NEWNET, + } + out, err := cmd.CombinedOutput() + if err != nil { + if strings.Contains(err.Error(), "operation not permitted") { + // Issue 17206: despite all the checks above, + // this still reportedly fails for some users. + // (older kernels?). Just skip. + t.Skip("skipping due to permission error") + } + t.Fatalf("Cmd failed with err %v, output: %s", err, out) + } + + // Check there is only the local network interface + sout := strings.TrimSpace(string(out)) + if !strings.Contains(sout, "lo:") { + t.Fatalf("Expected lo network interface to exist, got %s", sout) + } + + lines := strings.Split(sout, "\n") + if len(lines) >= len(origLines) { + t.Fatalf("Got %d lines of output, want <%d", len(lines), len(origLines)) + } +} + +func TestGroupCleanup(t *testing.T) { + if os.Getuid() != 0 { + t.Skip("we need root for credential") + } + cmd := exec.Command("id") + cmd.SysProcAttr = &syscall.SysProcAttr{ + Credential: &syscall.Credential{ + Uid: 0, + Gid: 0, + }, + } + out, err := cmd.CombinedOutput() + if err != nil { + t.Fatalf("Cmd failed with err %v, output: %s", err, out) + } + strOut := strings.TrimSpace(string(out)) + t.Logf("id: %s", strOut) + + expected := "uid=0(root) gid=0(root)" + // Just check prefix because some distros reportedly output a + // context parameter; see https://golang.org/issue/16224. + // Alpine does not output groups; see https://golang.org/issue/19938. + if !strings.HasPrefix(strOut, expected) { + t.Errorf("expected prefix: %q", expected) + } +} + +func TestGroupCleanupUserNamespace(t *testing.T) { + if os.Getuid() != 0 { + t.Skip("we need root for credential") + } + checkUserNS(t) + cmd := exec.Command("id") + uid, gid := os.Getuid(), os.Getgid() + cmd.SysProcAttr = &syscall.SysProcAttr{ + Cloneflags: syscall.CLONE_NEWUSER, + Credential: &syscall.Credential{ + Uid: uint32(uid), + Gid: uint32(gid), + }, + UidMappings: []syscall.SysProcIDMap{ + {ContainerID: 0, HostID: uid, Size: 1}, + }, + GidMappings: []syscall.SysProcIDMap{ + {ContainerID: 0, HostID: gid, Size: 1}, + }, + } + out, err := cmd.CombinedOutput() + if err != nil { + t.Fatalf("Cmd failed with err %v, output: %s", err, out) + } + strOut := strings.TrimSpace(string(out)) + t.Logf("id: %s", strOut) + + // As in TestGroupCleanup, just check prefix. + // The actual groups and contexts seem to vary from one distro to the next. + expected := "uid=0(root) gid=0(root) groups=0(root)" + if !strings.HasPrefix(strOut, expected) { + t.Errorf("expected prefix: %q", expected) + } +} + +// TestUnshareHelperProcess isn't a real test. It's used as a helper process +// for TestUnshareMountNameSpace. +func TestUnshareMountNameSpaceHelper(*testing.T) { + if os.Getenv("GO_WANT_HELPER_PROCESS") != "1" { + return + } + defer os.Exit(0) + if err := syscall.Mount("none", flag.Args()[0], "proc", 0, ""); err != nil { + fmt.Fprintf(os.Stderr, "unshare: mount %v failed: %v", os.Args, err) + os.Exit(2) + } +} + +// Test for Issue 38471: unshare fails because systemd has forced / to be shared +func TestUnshareMountNameSpace(t *testing.T) { + skipInContainer(t) + // Make sure we are running as root so we have permissions to use unshare + // and create a network namespace. + if os.Getuid() != 0 { + t.Skip("kernel prohibits unshare in unprivileged process, unless using user namespace") + } + + d, err := os.MkdirTemp("", "unshare") + if err != nil { + t.Fatalf("tempdir: %v", err) + } + + cmd := exec.Command(os.Args[0], "-test.run=TestUnshareMountNameSpaceHelper", d) + cmd.Env = append(os.Environ(), "GO_WANT_HELPER_PROCESS=1") + cmd.SysProcAttr = &syscall.SysProcAttr{Unshareflags: syscall.CLONE_NEWNS} + + o, err := cmd.CombinedOutput() + if err != nil { + if strings.Contains(err.Error(), ": permission denied") { + t.Skipf("Skipping test (golang.org/issue/19698); unshare failed due to permissions: %s, %v", o, err) + } + t.Fatalf("unshare failed: %s, %v", o, err) + } + + // How do we tell if the namespace was really unshared? It turns out + // to be simple: just try to remove the directory. If it's still mounted + // on the rm will fail with EBUSY. Then we have some cleanup to do: + // we must unmount it, then try to remove it again. + + if err := os.Remove(d); err != nil { + t.Errorf("rmdir failed on %v: %v", d, err) + if err := syscall.Unmount(d, syscall.MNT_FORCE); err != nil { + t.Errorf("Can't unmount %v: %v", d, err) + } + if err := os.Remove(d); err != nil { + t.Errorf("rmdir after unmount failed on %v: %v", d, err) + } + } +} + +// Test for Issue 20103: unshare fails when chroot is used +func TestUnshareMountNameSpaceChroot(t *testing.T) { + skipInContainer(t) + // Make sure we are running as root so we have permissions to use unshare + // and create a network namespace. + if os.Getuid() != 0 { + t.Skip("kernel prohibits unshare in unprivileged process, unless using user namespace") + } + + d, err := os.MkdirTemp("", "unshare") + if err != nil { + t.Fatalf("tempdir: %v", err) + } + + // Since we are doing a chroot, we need the binary there, + // and it must be statically linked. + x := filepath.Join(d, "syscall.test") + cmd := exec.Command(testenv.GoToolPath(t), "test", "-c", "-o", x, "syscall") + cmd.Env = append(os.Environ(), "CGO_ENABLED=0") + if o, err := cmd.CombinedOutput(); err != nil { + t.Fatalf("Build of syscall in chroot failed, output %v, err %v", o, err) + } + + cmd = exec.Command("/syscall.test", "-test.run=TestUnshareMountNameSpaceHelper", "/") + cmd.Env = append(os.Environ(), "GO_WANT_HELPER_PROCESS=1") + cmd.SysProcAttr = &syscall.SysProcAttr{Chroot: d, Unshareflags: syscall.CLONE_NEWNS} + + o, err := cmd.CombinedOutput() + if err != nil { + if strings.Contains(err.Error(), ": permission denied") { + t.Skipf("Skipping test (golang.org/issue/19698); unshare failed due to permissions: %s, %v", o, err) + } + t.Fatalf("unshare failed: %s, %v", o, err) + } + + // How do we tell if the namespace was really unshared? It turns out + // to be simple: just try to remove the executable. If it's still mounted + // on, the rm will fail. Then we have some cleanup to do: + // we must force unmount it, then try to remove it again. + + if err := os.Remove(x); err != nil { + t.Errorf("rm failed on %v: %v", x, err) + if err := syscall.Unmount(d, syscall.MNT_FORCE); err != nil { + t.Fatalf("Can't unmount %v: %v", d, err) + } + if err := os.Remove(x); err != nil { + t.Fatalf("rm failed on %v: %v", x, err) + } + } + + if err := os.Remove(d); err != nil { + t.Errorf("rmdir failed on %v: %v", d, err) + } +} + +func TestUnshareUidGidMappingHelper(*testing.T) { + if os.Getenv("GO_WANT_HELPER_PROCESS") != "1" { + return + } + defer os.Exit(0) + if err := syscall.Chroot(os.TempDir()); err != nil { + fmt.Fprintln(os.Stderr, err) + os.Exit(2) + } +} + +// Test for Issue 29789: unshare fails when uid/gid mapping is specified +func TestUnshareUidGidMapping(t *testing.T) { + if os.Getuid() == 0 { + t.Skip("test exercises unprivileged user namespace, fails with privileges") + } + checkUserNS(t) + cmd := exec.Command(os.Args[0], "-test.run=TestUnshareUidGidMappingHelper") + cmd.Env = append(os.Environ(), "GO_WANT_HELPER_PROCESS=1") + cmd.SysProcAttr = &syscall.SysProcAttr{ + Unshareflags: syscall.CLONE_NEWNS | syscall.CLONE_NEWUSER, + GidMappingsEnableSetgroups: false, + UidMappings: []syscall.SysProcIDMap{ + { + ContainerID: 0, + HostID: syscall.Getuid(), + Size: 1, + }, + }, + GidMappings: []syscall.SysProcIDMap{ + { + ContainerID: 0, + HostID: syscall.Getgid(), + Size: 1, + }, + }, + } + out, err := cmd.CombinedOutput() + if err != nil { + t.Fatalf("Cmd failed with err %v, output: %s", err, out) + } +} + +func prepareCgroupFD(t *testing.T) (int, string) { + t.Helper() + + const O_PATH = 0x200000 // Same for all architectures, but for some reason not defined in syscall for 386||amd64. + + // Requires cgroup v2. + const prefix = "/sys/fs/cgroup" + selfCg, err := os.ReadFile("/proc/self/cgroup") + if err != nil { + if os.IsNotExist(err) || os.IsPermission(err) { + t.Skip(err) + } + t.Fatal(err) + } + + // Expect a single line like this: + // 0::/user.slice/user-1000.slice/user@1000.service/app.slice/vte-spawn-891992a2-efbb-4f28-aedb-b24f9e706770.scope + // Otherwise it's either cgroup v1 or a hybrid hierarchy. + if bytes.Count(selfCg, []byte("\n")) > 1 { + t.Skip("cgroup v2 not available") + } + cg := bytes.TrimPrefix(selfCg, []byte("0::")) + if len(cg) == len(selfCg) { // No prefix found. + t.Skipf("cgroup v2 not available (/proc/self/cgroup contents: %q)", selfCg) + } + + // Need clone3 with CLONE_INTO_CGROUP support. + _, err = syscall.ForkExec("non-existent binary", nil, &syscall.ProcAttr{ + Sys: &syscall.SysProcAttr{ + UseCgroupFD: true, + CgroupFD: -1, + }, + }) + // // EPERM can be returned if clone3 is not enabled by seccomp. + if err == syscall.ENOSYS || err == syscall.EPERM { + t.Skipf("clone3 with CLONE_INTO_CGROUP not available: %v", err) + } + + // Need an ability to create a sub-cgroup. + subCgroup, err := os.MkdirTemp(prefix+string(bytes.TrimSpace(cg)), "subcg-") + if err != nil { + // ErrPermission or EROFS (#57262) when running in an unprivileged container. + // ErrNotExist when cgroupfs is not mounted in chroot/schroot. + if os.IsNotExist(err) || os.IsPermission(err) || errors.Is(err, syscall.EROFS) { + t.Skip(err) + } + t.Fatal(err) + } + t.Cleanup(func() { syscall.Rmdir(subCgroup) }) + + cgroupFD, err := syscall.Open(subCgroup, O_PATH, 0) + if err != nil { + t.Fatal(&os.PathError{Op: "open", Path: subCgroup, Err: err}) + } + t.Cleanup(func() { syscall.Close(cgroupFD) }) + + return cgroupFD, "/" + path.Base(subCgroup) +} + +func TestUseCgroupFD(t *testing.T) { + fd, suffix := prepareCgroupFD(t) + + cmd := exec.Command(os.Args[0], "-test.run=TestUseCgroupFDHelper") + cmd.Env = append(os.Environ(), "GO_WANT_HELPER_PROCESS=1") + cmd.SysProcAttr = &syscall.SysProcAttr{ + UseCgroupFD: true, + CgroupFD: fd, + } + out, err := cmd.CombinedOutput() + if err != nil { + t.Fatalf("Cmd failed with err %v, output: %s", err, out) + } + // NB: this wouldn't work with cgroupns. + if !bytes.HasSuffix(bytes.TrimSpace(out), []byte(suffix)) { + t.Fatalf("got: %q, want: a line that ends with %q", out, suffix) + } +} + +func TestUseCgroupFDHelper(*testing.T) { + if os.Getenv("GO_WANT_HELPER_PROCESS") != "1" { + return + } + defer os.Exit(0) + // Read and print own cgroup path. + selfCg, err := os.ReadFile("/proc/self/cgroup") + if err != nil { + fmt.Fprintln(os.Stderr, err) + os.Exit(2) + } + fmt.Print(string(selfCg)) +} + +type capHeader struct { + version uint32 + pid int32 +} + +type capData struct { + effective uint32 + permitted uint32 + inheritable uint32 +} + +const CAP_SYS_TIME = 25 +const CAP_SYSLOG = 34 + +type caps struct { + hdr capHeader + data [2]capData +} + +func getCaps() (caps, error) { + var c caps + + // Get capability version + if _, _, errno := syscall.Syscall(syscall.SYS_CAPGET, uintptr(unsafe.Pointer(&c.hdr)), uintptr(unsafe.Pointer(nil)), 0); errno != 0 { + return c, fmt.Errorf("SYS_CAPGET: %v", errno) + } + + // Get current capabilities + if _, _, errno := syscall.Syscall(syscall.SYS_CAPGET, uintptr(unsafe.Pointer(&c.hdr)), uintptr(unsafe.Pointer(&c.data[0])), 0); errno != 0 { + return c, fmt.Errorf("SYS_CAPGET: %v", errno) + } + + return c, nil +} + +func mustSupportAmbientCaps(t *testing.T) { + var uname syscall.Utsname + if err := syscall.Uname(&uname); err != nil { + t.Fatalf("Uname: %v", err) + } + var buf [65]byte + for i, b := range uname.Release { + buf[i] = byte(b) + } + ver := string(buf[:]) + ver, _, _ = strings.Cut(ver, "\x00") + if strings.HasPrefix(ver, "2.") || + strings.HasPrefix(ver, "3.") || + strings.HasPrefix(ver, "4.1.") || + strings.HasPrefix(ver, "4.2.") { + t.Skipf("kernel version %q predates required 4.3; skipping test", ver) + } +} + +// TestAmbientCapsHelper isn't a real test. It's used as a helper process for +// TestAmbientCaps. +func TestAmbientCapsHelper(*testing.T) { + if os.Getenv("GO_WANT_HELPER_PROCESS") != "1" { + return + } + defer os.Exit(0) + + caps, err := getCaps() + if err != nil { + fmt.Fprintln(os.Stderr, err) + os.Exit(2) + } + if caps.data[0].effective&(1<