mirror of
https://github.com/opencontainers/runc.git
synced 2026-07-11 22:37:14 +08:00
Aleksa Sarai
8e1cd2f56d
If a file descriptor of a directory in the host's mount namespace is leaked to runc init, a malicious config.json could use /proc/self/fd/... as a working directory to allow for host filesystem access after the container runs. This can also be exploited by a container process if it knows that an administrator will use "runc exec --cwd" and the target --cwd (the attacker can change that cwd to be a symlink pointing to /proc/self/fd/... and wait for the process to exec and then snoop on /proc/$pid/cwd to get access to the host). The former issue can lead to a critical vulnerability in Docker and Kubernetes, while the latter is a container breakout. We can (ab)use the fact that getcwd(2) on Linux detects this exact case, and getcwd(3) and Go's Getwd() return an error as a result. Thus, if we just do os.Getwd() after chdir we can easily detect this case and error out. In runc 1.1, a /sys/fs/cgroup handle happens to be leaked to "runc init", making this exploitable. On runc main it just so happens that the leaked /sys/fs/cgroup gets clobbered and thus this is only consistently exploitable for runc 1.1. Fixes: GHSA-xr7r-f8xq-vfvv CVE-2024-21626 Co-developed-by: lifubang <lifubang@acmcoder.com> Signed-off-by: lifubang <lifubang@acmcoder.com> [refactored the implementation and added more comments] Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
420 lines
9.0 KiB
Go
420 lines
9.0 KiB
Go
//go:build linux && cgo && seccomp
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// +build linux,cgo,seccomp
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package integration
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import (
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"strings"
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"syscall"
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"testing"
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"github.com/opencontainers/runc/libcontainer"
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"github.com/opencontainers/runc/libcontainer/configs"
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libseccomp "github.com/seccomp/libseccomp-golang"
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)
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func TestSeccompDenySyslogWithErrno(t *testing.T) {
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if testing.Short() {
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return
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}
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errnoRet := uint(syscall.ESRCH)
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config := newTemplateConfig(t, nil)
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config.Seccomp = &configs.Seccomp{
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DefaultAction: configs.Allow,
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Syscalls: []*configs.Syscall{
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{
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Name: "syslog",
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Action: configs.Errno,
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ErrnoRet: &errnoRet,
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},
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},
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}
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container, err := newContainer(t, config)
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ok(t, err)
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defer container.Destroy() //nolint:errcheck
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buffers := newStdBuffers()
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pwd := &libcontainer.Process{
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Cwd: "/",
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Args: []string{"dmesg"},
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Env: standardEnvironment,
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Stdin: buffers.Stdin,
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Stdout: buffers.Stdout,
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Stderr: buffers.Stderr,
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Init: true,
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}
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err = container.Run(pwd)
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ok(t, err)
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ps, err := pwd.Wait()
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if err == nil {
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t.Fatal("Expecting error (negative return code); instead exited cleanly!")
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}
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var exitCode int
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status := ps.Sys().(syscall.WaitStatus)
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if status.Exited() {
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exitCode = status.ExitStatus()
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} else if status.Signaled() {
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exitCode = -int(status.Signal())
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} else {
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t.Fatalf("Unrecognized exit reason!")
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}
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if exitCode == 0 {
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t.Fatalf("dmesg should fail with negative exit code, instead got %d!", exitCode)
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}
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expected := "dmesg: klogctl: No such process"
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actual := strings.Trim(buffers.Stderr.String(), "\n")
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if actual != expected {
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t.Fatalf("Expected output %s but got %s\n", expected, actual)
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}
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}
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func TestSeccompDenySyslog(t *testing.T) {
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if testing.Short() {
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return
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}
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config := newTemplateConfig(t, nil)
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config.Seccomp = &configs.Seccomp{
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DefaultAction: configs.Allow,
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Syscalls: []*configs.Syscall{
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{
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Name: "syslog",
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Action: configs.Errno,
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},
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},
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}
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container, err := newContainer(t, config)
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ok(t, err)
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defer container.Destroy() //nolint:errcheck
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buffers := newStdBuffers()
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pwd := &libcontainer.Process{
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Cwd: "/",
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Args: []string{"dmesg"},
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Env: standardEnvironment,
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Stdin: buffers.Stdin,
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Stdout: buffers.Stdout,
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Stderr: buffers.Stderr,
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Init: true,
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}
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err = container.Run(pwd)
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ok(t, err)
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ps, err := pwd.Wait()
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if err == nil {
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t.Fatal("Expecting error (negative return code); instead exited cleanly!")
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}
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var exitCode int
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status := ps.Sys().(syscall.WaitStatus)
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if status.Exited() {
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exitCode = status.ExitStatus()
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} else if status.Signaled() {
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exitCode = -int(status.Signal())
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} else {
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t.Fatalf("Unrecognized exit reason!")
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}
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if exitCode == 0 {
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t.Fatalf("dmesg should fail with negative exit code, instead got %d!", exitCode)
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}
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expected := "dmesg: klogctl: Operation not permitted"
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actual := strings.Trim(buffers.Stderr.String(), "\n")
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if actual != expected {
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t.Fatalf("Expected output %s but got %s\n", expected, actual)
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}
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}
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func TestSeccompPermitWriteConditional(t *testing.T) {
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if testing.Short() {
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return
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}
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config := newTemplateConfig(t, nil)
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config.Seccomp = &configs.Seccomp{
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DefaultAction: configs.Allow,
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Syscalls: []*configs.Syscall{
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{
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Name: "write",
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Action: configs.Errno,
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Args: []*configs.Arg{
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{
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Index: 0,
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Value: 2,
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Op: configs.EqualTo,
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},
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},
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},
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},
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}
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container, err := newContainer(t, config)
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ok(t, err)
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defer container.Destroy() //nolint:errcheck
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buffers := newStdBuffers()
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dmesg := &libcontainer.Process{
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Cwd: "/",
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Args: []string{"busybox", "ls", "/"},
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Env: standardEnvironment,
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Stdin: buffers.Stdin,
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Stdout: buffers.Stdout,
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Stderr: buffers.Stderr,
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Init: true,
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}
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err = container.Run(dmesg)
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ok(t, err)
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if _, err := dmesg.Wait(); err != nil {
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t.Fatalf("%s: %s", err, buffers.Stderr)
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}
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}
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func TestSeccompDenyWriteConditional(t *testing.T) {
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if testing.Short() {
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return
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}
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// Only test if library version is v2.2.1 or higher
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// Conditional filtering will always error in v2.2.0 and lower
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major, minor, micro := libseccomp.GetLibraryVersion()
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if (major == 2 && minor < 2) || (major == 2 && minor == 2 && micro < 1) {
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return
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}
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config := newTemplateConfig(t, nil)
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config.Seccomp = &configs.Seccomp{
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DefaultAction: configs.Allow,
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Syscalls: []*configs.Syscall{
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{
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Name: "write",
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Action: configs.Errno,
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Args: []*configs.Arg{
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{
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Index: 0,
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Value: 2,
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Op: configs.EqualTo,
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},
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},
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},
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},
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}
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container, err := newContainer(t, config)
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ok(t, err)
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defer container.Destroy() //nolint:errcheck
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buffers := newStdBuffers()
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dmesg := &libcontainer.Process{
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Cwd: "/",
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Args: []string{"busybox", "ls", "does_not_exist"},
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Env: standardEnvironment,
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Stdin: buffers.Stdin,
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Stdout: buffers.Stdout,
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Stderr: buffers.Stderr,
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Init: true,
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}
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err = container.Run(dmesg)
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ok(t, err)
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ps, err := dmesg.Wait()
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if err == nil {
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t.Fatal("Expecting negative return, instead got 0!")
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}
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var exitCode int
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status := ps.Sys().(syscall.WaitStatus)
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if status.Exited() {
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exitCode = status.ExitStatus()
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} else if status.Signaled() {
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exitCode = -int(status.Signal())
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} else {
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t.Fatalf("Unrecognized exit reason!")
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}
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if exitCode == 0 {
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t.Fatalf("Busybox should fail with negative exit code, instead got %d!", exitCode)
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}
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// We're denying write to stderr, so we expect an empty buffer
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expected := ""
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actual := strings.Trim(buffers.Stderr.String(), "\n")
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if actual != expected {
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t.Fatalf("Expected output %s but got %s\n", expected, actual)
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}
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}
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func TestSeccompPermitWriteMultipleConditions(t *testing.T) {
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if testing.Short() {
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return
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}
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config := newTemplateConfig(t, nil)
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config.Seccomp = &configs.Seccomp{
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DefaultAction: configs.Allow,
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Syscalls: []*configs.Syscall{
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{
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Name: "write",
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Action: configs.Errno,
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Args: []*configs.Arg{
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{
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Index: 0,
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Value: 2,
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Op: configs.EqualTo,
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},
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{
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Index: 2,
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Value: 0,
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Op: configs.NotEqualTo,
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},
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},
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},
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},
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}
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buffers := runContainerOk(t, config, "ls", "/")
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// We don't need to verify the actual thing printed
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// Just that something was written to stdout
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if len(buffers.Stdout.String()) == 0 {
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t.Fatalf("Nothing was written to stdout, write call failed!\n")
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}
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}
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func TestSeccompDenyWriteMultipleConditions(t *testing.T) {
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if testing.Short() {
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return
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}
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// Only test if library version is v2.2.1 or higher
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// Conditional filtering will always error in v2.2.0 and lower
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major, minor, micro := libseccomp.GetLibraryVersion()
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if (major == 2 && minor < 2) || (major == 2 && minor == 2 && micro < 1) {
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return
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}
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config := newTemplateConfig(t, nil)
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config.Seccomp = &configs.Seccomp{
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DefaultAction: configs.Allow,
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Syscalls: []*configs.Syscall{
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{
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Name: "write",
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Action: configs.Errno,
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Args: []*configs.Arg{
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{
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Index: 0,
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Value: 2,
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Op: configs.EqualTo,
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},
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{
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Index: 2,
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Value: 0,
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Op: configs.NotEqualTo,
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},
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},
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},
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},
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}
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buffers, exitCode, err := runContainer(t, config, "ls", "/does_not_exist")
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if err == nil {
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t.Fatalf("Expecting error return, instead got 0")
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}
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if exitCode == 0 {
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t.Fatalf("Busybox should fail with negative exit code, instead got %d!", exitCode)
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}
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expected := ""
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actual := strings.Trim(buffers.Stderr.String(), "\n")
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if actual != expected {
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t.Fatalf("Expected output %s but got %s\n", expected, actual)
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}
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}
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func TestSeccompMultipleConditionSameArgDeniesStdout(t *testing.T) {
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if testing.Short() {
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return
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}
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// Prevent writing to both stdout and stderr.
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config := newTemplateConfig(t, nil)
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config.Seccomp = &configs.Seccomp{
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DefaultAction: configs.Allow,
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Syscalls: []*configs.Syscall{
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{
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Name: "write",
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Action: configs.Errno,
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Args: []*configs.Arg{
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{
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Index: 0,
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Value: 1,
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Op: configs.EqualTo,
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},
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{
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Index: 0,
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Value: 2,
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Op: configs.EqualTo,
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},
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},
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},
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},
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}
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buffers := runContainerOk(t, config, "ls", "/")
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// Verify that nothing was printed
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if len(buffers.Stdout.String()) != 0 {
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t.Fatalf("Something was written to stdout, write call succeeded!\n")
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}
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}
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func TestSeccompMultipleConditionSameArgDeniesStderr(t *testing.T) {
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if testing.Short() {
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return
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}
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// Prevent writing to both stdout and stderr.
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config := newTemplateConfig(t, nil)
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config.Seccomp = &configs.Seccomp{
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DefaultAction: configs.Allow,
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Syscalls: []*configs.Syscall{
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{
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Name: "write",
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Action: configs.Errno,
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Args: []*configs.Arg{
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{
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Index: 0,
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Value: 1,
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Op: configs.EqualTo,
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},
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{
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Index: 0,
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Value: 2,
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Op: configs.EqualTo,
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},
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},
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},
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},
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}
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buffers, exitCode, err := runContainer(t, config, "ls", "/does_not_exist")
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if err == nil {
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t.Fatalf("Expecting error return, instead got 0")
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}
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if exitCode == 0 {
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t.Fatalf("Busybox should fail with negative exit code, instead got %d!", exitCode)
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}
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// Verify nothing was printed
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if len(buffers.Stderr.String()) != 0 {
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t.Fatalf("Something was written to stderr, write call succeeded!\n")
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}
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}
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