runtime: enable sandbox feature on qemu

Enable "-sandbox on" in qemu can introduce another protect layer
on the host, to make the secure container more secure.

The default option is disable because this feature may introduce some
performance cost, even though user can enable
/proc/sys/net/core/bpf_jit_enable to reduce the impact.

Fixes: #2266

Signed-off-by: Feng Wang <feng.wang@databricks.com>

src/runtime/Makefile

@@ -167,6 +167,11 @@ DEFDISABLEGUESTEMPTYDIR := false
 DEFAULTEXPFEATURES := []
 
 DEFDISABLESELINUX := false
+#Default SeccomSandbox param
+#The same default policy is used by libvirt
+#More explanation on https://lists.gnu.org/archive/html/qemu-devel/2017-02/msg03348.html
+# Note: "elevateprivileges=deny" doesn't work with daemonize option, so it's removed from the seccomp sandbox
+DEFSECCOMPSANDBOXPARAM := on,obsolete=deny,spawn=deny,resourcecontrol=deny
 
 #Default entropy source
 DEFENTROPYSOURCE := /dev/urandom
@@ -459,6 +464,7 @@ USER_VARS += DEFVIRTIOFSCACHE
 USER_VARS += DEFVIRTIOFSEXTRAARGS
 USER_VARS += DEFENABLEANNOTATIONS
 USER_VARS += DEFENABLEIOTHREADS
+USER_VARS += DEFSECCOMPSANDBOXPARAM
 USER_VARS += DEFENABLEVHOSTUSERSTORE
 USER_VARS += DEFVHOSTUSERSTOREPATH
 USER_VARS += DEFVALIDVHOSTUSERSTOREPATHS

src/runtime/config/configuration-qemu.toml.in

@@ -76,6 +76,14 @@ firmware_volume = "@FIRMWAREVOLUMEPATH@"
 # For example, `machine_accelerators = "nosmm,nosmbus,nosata,nopit,static-prt,nofw"`
 machine_accelerators="@MACHINEACCELERATORS@"
 
+# Qemu seccomp sandbox feature
+# comma-separated list of seccomp sandbox features to control the syscall access.
+# For example, `seccompsandbox= "on,obsolete=deny,spawn=deny,resourcecontrol=deny"`
+# Note: "elevateprivileges=deny" doesn't work with daemonize option, so it's removed from the seccomp sandbox
+# Another note: enabling this feature may reduce performance, you may enable
+# /proc/sys/net/core/bpf_jit_enable to reduce the impact. see https://man7.org/linux/man-pages/man8/bpfc.8.html
+#seccompsandbox="@DEFSECCOMPSANDBOXPARAM@"
+
 # CPU features
 # comma-separated list of cpu features to pass to the cpu
 # For example, `cpu_features = "pmu=off,vmx=off"

src/runtime/pkg/govmm/qemu/qemu.go

@@ -15,6 +15,7 @@ package qemu
 
 import (
 	"bytes"
+	"context"
 	"fmt"
 	"log"
 	"os"
@@ -23,8 +24,6 @@ import (
 	"strconv"
 	"strings"
 	"syscall"
-
-	"context"
 )
 
 // Machine describes the machine type qemu will emulate.

src/runtime/pkg/katautils/config.go

@@ -95,6 +95,7 @@ type hypervisor struct {
 	FileBackedMemRootDir           string   `toml:"file_mem_backend"`
 	GuestHookPath                  string   `toml:"guest_hook_path"`
 	GuestMemoryDumpPath            string   `toml:"guest_memory_dump_path"`
+	SeccompSandbox                 string   `toml:"seccompsandbox"`
 	HypervisorPathList             []string `toml:"valid_hypervisor_paths"`
 	JailerPathList                 []string `toml:"valid_jailer_paths"`
 	CtlPathList                    []string `toml:"valid_ctlpaths"`
@@ -767,6 +768,7 @@ func newQemuHypervisorConfig(h hypervisor) (vc.HypervisorConfig, error) {
 		EnableVhostUserStore:    h.EnableVhostUserStore,
 		VhostUserStorePath:      h.vhostUserStorePath(),
 		VhostUserStorePathList:  h.VhostUserStorePathList,
+		SeccompSandbox:          h.SeccompSandbox,
 		GuestHookPath:           h.guestHookPath(),
 		RxRateLimiterMaxRate:    rxRateLimiterMaxRate,
 		TxRateLimiterMaxRate:    txRateLimiterMaxRate,

src/runtime/virtcontainers/hypervisor.go

@@ -370,6 +370,9 @@ type HypervisorConfig struct {
 	// VhostUserStorePathList is the list of valid values for vhost-user paths
 	VhostUserStorePathList []string
 
+	// SeccompSandbox is the qemu function which enables the seccomp feature
+	SeccompSandbox string
+
 	// KernelParams are additional guest kernel parameters.
 	KernelParams []Param
 

src/runtime/virtcontainers/persist.go

@@ -247,6 +247,7 @@ func (s *Sandbox) dumpConfig(ss *persistapi.SandboxState) {
 		BootFromTemplate:        sconfig.HypervisorConfig.BootFromTemplate,
 		DisableVhostNet:         sconfig.HypervisorConfig.DisableVhostNet,
 		EnableVhostUserStore:    sconfig.HypervisorConfig.EnableVhostUserStore,
+		SeccompSandbox:          sconfig.HypervisorConfig.SeccompSandbox,
 		VhostUserStorePath:      sconfig.HypervisorConfig.VhostUserStorePath,
 		VhostUserStorePathList:  sconfig.HypervisorConfig.VhostUserStorePathList,
 		GuestHookPath:           sconfig.HypervisorConfig.GuestHookPath,

src/runtime/virtcontainers/persist/api/config.go

@@ -80,6 +80,9 @@ type HypervisorConfig struct {
 	// related folders, sockets and device nodes should be.
 	VhostUserStorePath string
 
+	// SeccompSandbox is the qemu function which enables the seccomp feature
+	SeccompSandbox string
+
 	// GuestHookPath is the path within the VM that will be used for 'drop-in' hooks
 	GuestHookPath string
 

src/runtime/virtcontainers/qemu.go

@@ -629,6 +629,7 @@ func (q *qemu) CreateVM(ctx context.Context, id string, network Network, hypervi
 		// some devices configuration may also change kernel params, make sure this is called afterwards
 		Params: q.kernelParameters(),
 	}
+	q.checkBpfEnabled()
 
 	qemuConfig := govmmQemu.Config{
 		Name:           fmt.Sprintf("sandbox-%s", q.id),
@@ -643,6 +644,7 @@ func (q *qemu) CreateVM(ctx context.Context, id string, network Network, hypervi
 		Memory:         memory,
 		Devices:        devices,
 		CPUModel:       cpuModel,
+		SeccompSandbox: q.config.SeccompSandbox,
 		Kernel:         kernel,
 		RTC:            rtc,
 		QMPSockets:     qmpSockets,
@@ -689,6 +691,25 @@ func (q *qemu) CreateVM(ctx context.Context, id string, network Network, hypervi
 	return err
 }
 
+func (q *qemu) checkBpfEnabled() {
+	if q.config.SeccompSandbox != "" {
+		out, err := os.ReadFile("/proc/sys/net/core/bpf_jit_enable")
+		if err != nil {
+			q.Logger().WithError(err).Warningf("failed to get bpf_jit_enable status")
+			return
+		}
+		enabled, err := strconv.Atoi(string(out))
+		if err != nil {
+			q.Logger().WithError(err).Warningf("failed to convert bpf_jit_enable status to integer")
+			return
+		}
+		if enabled == 0 {
+			q.Logger().Warningf("bpf_jit_enable is disabled. " +
+				"It's recommended to turn on bpf_jit_enable to reduce the performance impact of QEMU seccomp sandbox.")
+		}
+	}
+}
+
 func (q *qemu) vhostFSSocketPath(id string) (string, error) {
 	return utils.BuildSocketPath(q.config.VMStorePath, id, vhostFSSocket)
 }