gvisor/runsc/cmd/capability.go

// Copyright 2018 Google LLC
//
// 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 cmd

import (
	"fmt"

	specs "github.com/opencontainers/runtime-spec/specs-go"
	"github.com/syndtr/gocapability/capability"
	"gvisor.googlesource.com/gvisor/pkg/log"
)

var allCapTypes = []capability.CapType{
	capability.BOUNDS,
	capability.EFFECTIVE,
	capability.PERMITTED,
	capability.INHERITABLE,
	capability.AMBIENT,
}

// applyCaps applies the capabilities in the spec to the current thread.
//
// Note that it must be called with current thread locked.
func applyCaps(caps *specs.LinuxCapabilities) error {
	// Load current capabilities to trim the ones not permitted.
	curCaps, err := capability.NewPid2(0)
	if err != nil {
		return err
	}
	if err := curCaps.Load(); err != nil {
		return err
	}

	// Create an empty capability set to populate.
	newCaps, err := capability.NewPid2(0)
	if err != nil {
		return err
	}

	for _, c := range allCapTypes {
		if !newCaps.Empty(c) {
			panic("unloaded capabilities must be empty")
		}
		set, err := trimCaps(getCaps(c, caps), curCaps)
		if err != nil {
			return err
		}
		newCaps.Set(c, set...)
	}

	if err := newCaps.Apply(capability.CAPS | capability.BOUNDS | capability.AMBS); err != nil {
		return err
	}
	log.Infof("Capabilities applied: %+v", newCaps)
	return nil
}

func getCaps(which capability.CapType, caps *specs.LinuxCapabilities) []string {
	switch which {
	case capability.BOUNDS:
		return caps.Bounding
	case capability.EFFECTIVE:
		return caps.Effective
	case capability.PERMITTED:
		return caps.Permitted
	case capability.INHERITABLE:
		return caps.Inheritable
	case capability.AMBIENT:
		return caps.Ambient
	}
	panic(fmt.Sprint("invalid capability type:", which))
}

func trimCaps(names []string, setter capability.Capabilities) ([]capability.Cap, error) {
	wantedCaps, err := capsFromNames(names)
	if err != nil {
		return nil, err
	}

	// Trim down capabilities that aren't possible to acquire.
	var caps []capability.Cap
	for _, c := range wantedCaps {
		// Capability rules are more complicated than this, but this catches most
		// problems with tests running with non-privileged user.
		if setter.Get(capability.PERMITTED, c) {
			caps = append(caps, c)
		} else {
			log.Warningf("Capability %q is not permitted, dropping it.", c)
		}
	}
	return caps, nil
}

func capsFromNames(names []string) ([]capability.Cap, error) {
	var caps []capability.Cap
	for _, name := range names {
		cap, ok := capFromName[name]
		if !ok {
			return nil, fmt.Errorf("invalid capability %q", name)
		}
		caps = append(caps, cap)
	}
	return caps, nil
}

var capFromName = map[string]capability.Cap{
	"CAP_CHOWN":            capability.CAP_CHOWN,
	"CAP_DAC_OVERRIDE":     capability.CAP_DAC_OVERRIDE,
	"CAP_DAC_READ_SEARCH":  capability.CAP_DAC_READ_SEARCH,
	"CAP_FOWNER":           capability.CAP_FOWNER,
	"CAP_FSETID":           capability.CAP_FSETID,
	"CAP_KILL":             capability.CAP_KILL,
	"CAP_SETGID":           capability.CAP_SETGID,
	"CAP_SETUID":           capability.CAP_SETUID,
	"CAP_SETPCAP":          capability.CAP_SETPCAP,
	"CAP_LINUX_IMMUTABLE":  capability.CAP_LINUX_IMMUTABLE,
	"CAP_NET_BIND_SERVICE": capability.CAP_NET_BIND_SERVICE,
	"CAP_NET_BROADCAST":    capability.CAP_NET_BROADCAST,
	"CAP_NET_ADMIN":        capability.CAP_NET_ADMIN,
	"CAP_NET_RAW":          capability.CAP_NET_RAW,
	"CAP_IPC_LOCK":         capability.CAP_IPC_LOCK,
	"CAP_IPC_OWNER":        capability.CAP_IPC_OWNER,
	"CAP_SYS_MODULE":       capability.CAP_SYS_MODULE,
	"CAP_SYS_RAWIO":        capability.CAP_SYS_RAWIO,
	"CAP_SYS_CHROOT":       capability.CAP_SYS_CHROOT,
	"CAP_SYS_PTRACE":       capability.CAP_SYS_PTRACE,
	"CAP_SYS_PACCT":        capability.CAP_SYS_PACCT,
	"CAP_SYS_ADMIN":        capability.CAP_SYS_ADMIN,
	"CAP_SYS_BOOT":         capability.CAP_SYS_BOOT,
	"CAP_SYS_NICE":         capability.CAP_SYS_NICE,
	"CAP_SYS_RESOURCE":     capability.CAP_SYS_RESOURCE,
	"CAP_SYS_TIME":         capability.CAP_SYS_TIME,
	"CAP_SYS_TTY_CONFIG":   capability.CAP_SYS_TTY_CONFIG,
	"CAP_MKNOD":            capability.CAP_MKNOD,
	"CAP_LEASE":            capability.CAP_LEASE,
	"CAP_AUDIT_WRITE":      capability.CAP_AUDIT_WRITE,
	"CAP_AUDIT_CONTROL":    capability.CAP_AUDIT_CONTROL,
	"CAP_SETFCAP":          capability.CAP_SETFCAP,
	"CAP_MAC_OVERRIDE":     capability.CAP_MAC_OVERRIDE,
	"CAP_MAC_ADMIN":        capability.CAP_MAC_ADMIN,
	"CAP_SYSLOG":           capability.CAP_SYSLOG,
	"CAP_WAKE_ALARM":       capability.CAP_WAKE_ALARM,
	"CAP_BLOCK_SUSPEND":    capability.CAP_BLOCK_SUSPEND,
	"CAP_AUDIT_READ":       capability.CAP_AUDIT_READ,
}