Refactor registry to keep a state

.gitignore

@@ -1,2 +1,3 @@
 /seccompagent
+/seccompshell
 *.swp

Makefile

@@ -5,10 +5,17 @@ IMAGE_TAG=$(shell ./tools/image-tag)
 IMAGE_BRANCH_TAG=$(shell ./tools/image-tag branch)
 CONTAINER_REPO ?= quay.io/kinvolk/seccompagent
 
+.PHONY: all
+all: seccompagent seccompshell
+
 .PHONY: seccompagent
 seccompagent:
 	$(GO_BUILD) -o seccompagent ./cmd/seccompagent
 
+.PHONY: seccompshell
+seccompshell:
+	$(GO_BUILD) -tags seccomp -o seccompshell ./cmd/seccompshell
+
 .PHONY: container-build
 container-build:
 	docker build -t $(CONTAINER_REPO):$(IMAGE_TAG) -f Dockerfile .

cmd/seccompagent/seccompagent.go

@@ -69,47 +69,49 @@ func main() {
 		// Kubernetes API, find the pod, and allow or deny a syscall depending
 		// on the pod specifications (e.g. namespace, annotations,
 		// serviceAccount).
-		resolver = func(state *specs.ContainerProcessState) *registry.Registry {
-			r := registry.New()
+		resolver = func(state *specs.ContainerProcessState) registry.Filter {
+			f := registry.NewSimpleFilter()
 
 			// Example:
 			// 	/ # mount -t proc proc root
 			// 	/ # ls /root/self/cmdline
 			// 	/root/self/cmdline
 			allowedFilesystems := map[string]struct{}{"proc": struct{}{}}
-			r.Add("mount", handlers.Mount(allowedFilesystems))
+			f.AddHandler("mount", handlers.Mount(allowedFilesystems))
 
 			// Example:
 			// 	# chmod 777 /
 			// 	chmod: /: Bad message
-			r.Add("chmod", handlers.Error(unix.EBADMSG))
+			f.AddHandler("chmod", handlers.Error(unix.EBADMSG))
 
 			// Example:
 			// 	# mkdir /abc
 			// 	# ls -d /abc*
 			// 	/abc-pid-3528098
 			if state != nil {
-				r.Add("mkdir", handlers.MkdirWithSuffix(fmt.Sprintf("-pid-%d", state.State.Pid)))
+				f.AddHandler("mkdir", handlers.MkdirWithSuffix(fmt.Sprintf("-pid-%d", state.State.Pid)))
 			}
 
-			return r
+			return f
 		}
 	case "kubernetes":
-		kubeResolverFunc := func(podCtx *kuberesolver.PodContext, metadata map[string]string) *registry.Registry {
+		kubeResolverFunc := func(podCtx *kuberesolver.PodContext, metadata map[string]string) registry.Filter {
 			log.WithFields(log.Fields{
 				"pod":      podCtx,
 				"metadata": metadata,
 			}).Debug("New container")
 
-			r := registry.New()
+			f := registry.NewSimpleFilter()
+
+			f.AddHandler("chmod", handlers.ErrorSeq())
 
 			if v, ok := metadata["MKDIR_TMPL"]; ok {
 				tmpl, err := template.New("mkdirTmpl").Parse(v)
 				if err == nil {
 					var suffix strings.Builder
 					err = tmpl.Execute(&suffix, podCtx)
 					if err == nil {
-						r.Add("mkdir", handlers.MkdirWithSuffix(suffix.String()))
+						f.AddHandler("mkdir", handlers.MkdirWithSuffix(suffix.String()))
 					}
 				}
 			}
@@ -118,15 +120,15 @@ func main() {
 				d, ok := metadata["EXEC_DURATION"]
 				if ok {
 					duration, _ := time.ParseDuration(d)
-					r.Add("execve", handlers.ExecCondition(fileName, duration))
+					f.AddHandler("execve", handlers.ExecCondition(fileName, duration))
 				}
 			}
 
 			if sidecars, ok := metadata["SIDECARS"]; ok {
 				d, ok := metadata["SIDECARS_DELAY"]
 				if ok {
 					duration, _ := time.ParseDuration(d)
-					r.Add("execve", handlers.ExecSidecars(podCtx, sidecars, duration))
+					f.AddHandler("execve", handlers.ExecSidecars(podCtx, sidecars, duration))
 				}
 			}
 
@@ -138,9 +140,9 @@ func main() {
 				allowedFilesystems["sysfs"] = struct{}{}
 			}
 			if len(allowedFilesystems) > 0 {
-				r.Add("mount", handlers.Mount(allowedFilesystems))
+				f.AddHandler("mount", handlers.Mount(allowedFilesystems))
 			}
-			return r
+			return f
 		}
 		var err error
 		resolver, err = kuberesolver.KubeResolver(kubeResolverFunc)

cmd/seccompshell/seccompshell.go

@@ -0,0 +1,129 @@
+// +build linux,cgo
+
+package main
+
+import (
+	"encoding/json"
+	"errors"
+	"flag"
+	"fmt"
+	"io/ioutil"
+	"net"
+	"os"
+	"strings"
+
+	"github.com/opencontainers/runc/libcontainer/seccomp"
+	"github.com/opencontainers/runc/libcontainer/specconv"
+	"github.com/opencontainers/runc/libcontainer/utils"
+	"github.com/opencontainers/runtime-spec/specs-go"
+	log "github.com/sirupsen/logrus"
+	"golang.org/x/sys/unix"
+)
+
+var (
+	paramSeccompFile string
+	socketFile       string
+	paramMetadata    string
+	paramID          string
+	logflags         string
+)
+
+func init() {
+	flag.StringVar(&paramSeccompFile, "seccomp-policy", "/var/lib/kubelet/seccomp/default.json", "Seccomp Policy file")
+	flag.StringVar(&socketFile, "socketfile", "/run/seccomp-agent.socket", "Socket file")
+	flag.StringVar(&paramMetadata, "metadata", "", "Metadata to send to the seccomp agent")
+	flag.StringVar(&paramID, "id", "", "Container ID to send to the seccomp agent")
+	flag.StringVar(&logflags, "log", "info", "log level [trace,debug,info,warn,error,fatal,color,nocolor,json]")
+}
+
+func sendContainerProcessState(listenerPath string, state *specs.ContainerProcessState, fds ...int) error {
+	conn, err := net.Dial("unix", listenerPath)
+	if err != nil {
+		return fmt.Errorf("cannot connect to %q: %v\n", listenerPath, err)
+	}
+
+	socket, err := conn.(*net.UnixConn).File()
+	if err != nil {
+		return fmt.Errorf("cannot get socket: %v\n", err)
+	}
+	defer socket.Close()
+
+	b, err := json.Marshal(state)
+	if err != nil {
+		return fmt.Errorf("cannot marshall seccomp state: %v\n", err)
+	}
+
+	err = utils.SendFds(socket, b, fds...)
+	if err != nil {
+		return fmt.Errorf("cannot send seccomp fd to %s: %v\n", listenerPath, err)
+	}
+
+	return nil
+}
+
+func main() {
+	flag.Parse()
+	for _, v := range strings.Split(logflags, ",") {
+		if v == "json" {
+			log.SetFormatter(&log.JSONFormatter{})
+		} else if v == "color" {
+			log.SetFormatter(&log.TextFormatter{ForceColors: true})
+		} else if v == "nocolor" {
+			log.SetFormatter(&log.TextFormatter{DisableColors: true})
+		} else if lvl, err := log.ParseLevel(v); err == nil {
+			log.SetLevel(lvl)
+		} else {
+			fmt.Fprintf(os.Stderr, "Invalid log level: %s\n", err.Error())
+			flag.Usage()
+			os.Exit(1)
+		}
+	}
+	if flag.NArg() == 0 {
+		panic(errors.New("invalid command"))
+	}
+
+	buf, err := ioutil.ReadFile(paramSeccompFile)
+	if err != nil {
+		panic(fmt.Errorf("cannot read file %q: %s", paramSeccompFile, err))
+	}
+
+	seccompConfigOCI := &specs.LinuxSeccomp{}
+	json.Unmarshal(buf, seccompConfigOCI)
+
+	seccompConfig, err := specconv.SetupSeccomp(seccompConfigOCI)
+	if err != nil {
+		panic(fmt.Errorf("cannot convert seccomp policy from OCI format to libcontainer format: %s", err))
+	}
+
+	if err := unix.Prctl(unix.PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0); err != nil {
+		panic(fmt.Errorf("cannot set nonewprivileges", err))
+	}
+
+	containerProcessState := &specs.ContainerProcessState{
+		Version:   specs.Version,
+		FdIndexes: map[specs.FdIndexKey]int{specs.SeccompFdIndexKey: 0},
+		Pid:       os.Getpid(),
+		Metadata:  paramMetadata,
+		State: specs.State{
+			Version:     specs.Version,
+			ID:          paramID,
+			Status:      specs.StateRunning,
+			Pid:         os.Getpid(),
+			Bundle:      "",
+			Annotations: map[string]string{},
+		},
+	}
+	seccompFd, err := seccomp.InitSeccomp(seccompConfig)
+	if err != nil || seccompFd == -1 {
+		panic(fmt.Errorf("cannot init seccomp: %s", err))
+	}
+
+	if err := sendContainerProcessState(socketFile,
+		containerProcessState, int(seccompFd)); err != nil {
+		panic(fmt.Errorf("cannot send message to seccomp agent: %s", err))
+	}
+
+	if err := unix.Exec(flag.Arg(0), flag.Args()[1:], os.Environ()); err != nil {
+		panic(fmt.Errorf("cannot exec command", err))
+	}
+}

go.mod

@@ -3,12 +3,13 @@ module github.com/kinvolk/seccompagent
 go 1.15
 
 require (
-	github.com/opencontainers/runtime-spec v1.0.2
+	github.com/opencontainers/runc v0.0.0-00010101000000-000000000000
+	github.com/opencontainers/runtime-spec v1.0.3-0.20200929063507-e6143ca7d51d
 	github.com/seccomp/libseccomp-golang v0.9.1
 	github.com/sirupsen/logrus v1.7.0
 	golang.org/x/crypto v0.0.0-20200220183623-bac4c82f6975 // indirect
 	golang.org/x/oauth2 v0.0.0-20190604053449-0f29369cfe45 // indirect
-	golang.org/x/sys v0.0.0-20201101102859-da207088b7d1
+	golang.org/x/sys v0.0.0-20201107080550-4d91cf3a1aaf
 	golang.org/x/time v0.0.0-20200630173020-3af7569d3a1e // indirect
 	k8s.io/api v0.17.4
 	k8s.io/apimachinery v0.17.4
@@ -19,3 +20,5 @@ require (
 replace github.com/opencontainers/runtime-spec => github.com/kinvolk/runtime-spec v1.0.2-0.20201110202115-2755fc508653
 
 replace github.com/seccomp/libseccomp-golang => github.com/kinvolk/libseccomp-golang v0.9.2-0.20201113182948-883917843313
+
+replace github.com/opencontainers/runc => github.com/kinvolk/runc v0.1.1-0.20201126131201-5a620a897292