podman/libpod: add default AppArmor profile

Make users of libpod more secure by adding the libpod/apparmor package
to load a pre-defined AppArmor profile.  Large chunks of libpod/apparmor
come from github.com/moby/moby.

Also check if a specified AppArmor profile is actually loaded and throw
an error if necessary.

The default profile is loaded only on Linux builds with the `apparmor`
buildtag enabled.

Signed-off-by: Valentin Rothberg <vrothberg@suse.com>

Closes: #1063
Approved by: rhatdan

5 files changed, 344 insertions, 0 deletions

diff --git a/pkg/apparmor/aaparser.go b/pkg/apparmor/aaparser.go
new file mode 100644
index 000000000..cec9c4885
--- /dev/null
+++ b/pkg/apparmor/aaparser.go
@@ -0,0 +1,90 @@
+// +build linux,apparmor
+
+package apparmor
+
+import (
+	"fmt"
+	"os/exec"
+	"strconv"
+	"strings"
+)
+
+const (
+	binary = "apparmor_parser"
+)
+
+// getVersion returns the major and minor version of apparmor_parser.
+func getVersion() (int, error) {
+	output, err := cmd("", "--version")
+	if err != nil {
+		return -1, err
+	}
+
+	return parseVersion(output)
+}
+
+// loadProfile runs `apparmor_parser -Kr` on a specified apparmor profile to
+// replace the profile. The `-K` is necessary to make sure that apparmor_parser
+// doesn't try to write to a read-only filesystem.
+func loadProfile(profilePath string) error {
+	_, err := cmd("", "-Kr", profilePath)
+	return err
+}
+
+// cmd runs `apparmor_parser` with the passed arguments.
+func cmd(dir string, arg ...string) (string, error) {
+	c := exec.Command(binary, arg...)
+	c.Dir = dir
+
+	output, err := c.CombinedOutput()
+	if err != nil {
+		return "", fmt.Errorf("running `%s %s` failed with output: %s\nerror: %v", c.Path, strings.Join(c.Args, " "), output, err)
+	}
+
+	return string(output), nil
+}
+
+// parseVersion takes the output from `apparmor_parser --version` and returns
+// a representation of the {major, minor, patch} version as a single number of
+// the form MMmmPPP {major, minor, patch}.
+func parseVersion(output string) (int, error) {
+	// output is in the form of the following:
+	// AppArmor parser version 2.9.1
+	// Copyright (C) 1999-2008 Novell Inc.
+	// Copyright 2009-2012 Canonical Ltd.
+
+	lines := strings.SplitN(output, "\n", 2)
+	words := strings.Split(lines[0], " ")
+	version := words[len(words)-1]
+
+	// split by major minor version
+	v := strings.Split(version, ".")
+	if len(v) == 0 || len(v) > 3 {
+		return -1, fmt.Errorf("parsing version failed for output: `%s`", output)
+	}
+
+	// Default the versions to 0.
+	var majorVersion, minorVersion, patchLevel int
+
+	majorVersion, err := strconv.Atoi(v[0])
+	if err != nil {
+		return -1, err
+	}
+
+	if len(v) > 1 {
+		minorVersion, err = strconv.Atoi(v[1])
+		if err != nil {
+			return -1, err
+		}
+	}
+	if len(v) > 2 {
+		patchLevel, err = strconv.Atoi(v[2])
+		if err != nil {
+			return -1, err
+		}
+	}
+
+	// major*10^5 + minor*10^3 + patch*10^0
+	numericVersion := majorVersion*1e5 + minorVersion*1e3 + patchLevel
+	return numericVersion, nil
+}
diff --git a/pkg/apparmor/aaparser_test.go b/pkg/apparmor/aaparser_test.go
new file mode 100644
index 000000000..9d97969c7
--- /dev/null
+++ b/pkg/apparmor/aaparser_test.go
@@ -0,0 +1,75 @@
+// +build linux,apparmor
+
+package apparmor
+
+import (
+	"testing"
+)
+
+type versionExpected struct {
+	output  string
+	version int
+}
+
+func TestParseVersion(t *testing.T) {
+	versions := []versionExpected{
+		{
+			output: `AppArmor parser version 2.10
+Copyright (C) 1999-2008 Novell Inc.
+Copyright 2009-2012 Canonical Ltd.
+
+`,
+			version: 210000,
+		},
+		{
+			output: `AppArmor parser version 2.8
+Copyright (C) 1999-2008 Novell Inc.
+Copyright 2009-2012 Canonical Ltd.
+
+`,
+			version: 208000,
+		},
+		{
+			output: `AppArmor parser version 2.20
+Copyright (C) 1999-2008 Novell Inc.
+Copyright 2009-2012 Canonical Ltd.
+
+`,
+			version: 220000,
+		},
+		{
+			output: `AppArmor parser version 2.05
+Copyright (C) 1999-2008 Novell Inc.
+Copyright 2009-2012 Canonical Ltd.
+
+`,
+			version: 205000,
+		},
+		{
+			output: `AppArmor parser version 2.9.95
+Copyright (C) 1999-2008 Novell Inc.
+Copyright 2009-2012 Canonical Ltd.
+
+`,
+			version: 209095,
+		},
+		{
+			output: `AppArmor parser version 3.14.159
+Copyright (C) 1999-2008 Novell Inc.
+Copyright 2009-2012 Canonical Ltd.
+
+`,
+			version: 314159,
+		},
+	}
+
+	for _, v := range versions {
+		version, err := parseVersion(v.output)
+		if err != nil {
+			t.Fatalf("expected error to be nil for %#v, got: %v", v, err)
+		}
+		if version != v.version {
+			t.Fatalf("expected version to be %d, was %d, for: %#v\n", v.version, version, v)
+		}
+	}
+}
diff --git a/pkg/apparmor/apparmor.go b/pkg/apparmor/apparmor.go
new file mode 100644
index 000000000..1c205f68a
--- /dev/null
+++ b/pkg/apparmor/apparmor.go
@@ -0,0 +1,54 @@
+package apparmor
+
+import (
+	"errors"
+)
+
+var (
+	// profileDirectory is the file store for apparmor profiles and macros.
+	profileDirectory = "/etc/apparmor.d"
+	// DefaultLibpodProfile is the name of default libpod AppArmor profile.
+	DefaultLibpodProfile = "libpod-default"
+	// ErrApparmorUnsupported indicates that AppArmor support is not supported.
+	ErrApparmorUnsupported = errors.New("AppArmor is not supported")
+)
+
+const libpodProfileTemplate = `
+{{range $value := .Imports}}
+{{$value}}
+{{end}}
+
+profile {{.Name}} flags=(attach_disconnected,mediate_deleted) {
+{{range $value := .InnerImports}}
+  {{$value}}
+{{end}}
+
+  network,
+  capability,
+  file,
+  umount,
+
+  deny @{PROC}/* w,   # deny write for all files directly in /proc (not in a subdir)
+  # deny write to files not in /proc/<number>/** or /proc/sys/**
+  deny @{PROC}/{[^1-9],[^1-9][^0-9],[^1-9s][^0-9y][^0-9s],[^1-9][^0-9][^0-9][^0-9]*}/** w,
+  deny @{PROC}/sys/[^k]** w,  # deny /proc/sys except /proc/sys/k* (effectively /proc/sys/kernel)
+  deny @{PROC}/sys/kernel/{?,??,[^s][^h][^m]**} w,  # deny everything except shm* in /proc/sys/kernel/
+  deny @{PROC}/sysrq-trigger rwklx,
+  deny @{PROC}/kcore rwklx,
+
+  deny mount,
+
+  deny /sys/[^f]*/** wklx,
+  deny /sys/f[^s]*/** wklx,
+  deny /sys/fs/[^c]*/** wklx,
+  deny /sys/fs/c[^g]*/** wklx,
+  deny /sys/fs/cg[^r]*/** wklx,
+  deny /sys/firmware/** rwklx,
+  deny /sys/kernel/security/** rwklx,
+
+{{if ge .Version 208095}}
+  # suppress ptrace denials when using using 'ps' inside a container
+  ptrace (trace,read) peer={{.Name}},
+{{end}}
+}
+`
diff --git a/pkg/apparmor/apparmor_linux.go b/pkg/apparmor/apparmor_linux.go
new file mode 100644
index 000000000..6e8b7f312
--- /dev/null
+++ b/pkg/apparmor/apparmor_linux.go
@@ -0,0 +1,110 @@
+// +build linux,apparmor
+
+package apparmor
+
+import (
+	"bufio"
+	"io"
+	"io/ioutil"
+	"os"
+	"path"
+	"strings"
+	"text/template"
+)
+
+// profileData holds information about the given profile for generation.
+type profileData struct {
+	// Name is profile name.
+	Name string
+	// Imports defines the apparmor functions to import, before defining the profile.
+	Imports []string
+	// InnerImports defines the apparmor functions to import in the profile.
+	InnerImports []string
+	// Version is the {major, minor, patch} version of apparmor_parser as a single number.
+	Version int
+}
+
+// generateDefault creates an apparmor profile from ProfileData.
+func (p *profileData) generateDefault(out io.Writer) error {
+	compiled, err := template.New("apparmor_profile").Parse(libpodProfileTemplate)
+	if err != nil {
+		return err
+	}
+
+	if macroExists("tunables/global") {
+		p.Imports = append(p.Imports, "#include <tunables/global>")
+	} else {
+		p.Imports = append(p.Imports, "@{PROC}=/proc/")
+	}
+
+	if macroExists("abstractions/base") {
+		p.InnerImports = append(p.InnerImports, "#include <abstractions/base>")
+	}
+
+	ver, err := getVersion()
+	if err != nil {
+		return err
+	}
+	p.Version = ver
+
+	return compiled.Execute(out, p)
+}
+
+// macrosExists checks if the passed macro exists.
+func macroExists(m string) bool {
+	_, err := os.Stat(path.Join(profileDirectory, m))
+	return err == nil
+}
+
+// InstallDefault generates a default profile in a temp directory determined by
+// os.TempDir(), then loads the profile into the kernel using 'apparmor_parser'.
+func InstallDefault(name string) error {
+	p := profileData{
+		Name: name,
+	}
+
+	// Install to a temporary directory.
+	f, err := ioutil.TempFile("", name)
+	if err != nil {
+		return err
+	}
+	profilePath := f.Name()
+
+	defer f.Close()
+	defer os.Remove(profilePath)
+
+	if err := p.generateDefault(f); err != nil {
+		return err
+	}
+
+	return loadProfile(profilePath)
+}
+
+// IsLoaded checks if a profile with the given name has been loaded into the
+// kernel.
+func IsLoaded(name string) (bool, error) {
+	file, err := os.Open("/sys/kernel/security/apparmor/profiles")
+	if err != nil {
+		if os.IsNotExist(err) {
+			return false, nil
+		}
+		return false, err
+	}
+	defer file.Close()
+
+	r := bufio.NewReader(file)
+	for {
+		p, err := r.ReadString('\n')
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			return false, err
+		}
+		if strings.HasPrefix(p, name+" ") {
+			return true, nil
+		}
+	}
+
+	return false, nil
+}
diff --git a/pkg/apparmor/apparmor_unsupported.go b/pkg/apparmor/apparmor_unsupported.go
new file mode 100644
index 000000000..0f1ab9464
--- /dev/null
+++ b/pkg/apparmor/apparmor_unsupported.go
@@ -0,0 +1,15 @@
+// +build !linux !apparmor
+
+package apparmor
+
+// InstallDefault generates a default profile in a temp directory determined by
+// os.TempDir(), then loads the profile into the kernel using 'apparmor_parser'.
+func InstallDefault(name string) error {
+	return ErrApparmorUnsupported
+}
+
+// IsLoaded checks if a profile with the given name has been loaded into the
+// kernel.
+func IsLoaded(name string) (bool, error) {
+	return false, ErrApparmorUnsupported
+}