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

1 files changed, 90 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
+}