adds seccomp helpers

Signed-off-by: Mike Brown <brownwm@us.ibm.com>

contrib/seccomp/seccomp.go

@@ -0,0 +1,40 @@
+// +build linux
+
+package seccomp
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+
+	"github.com/containerd/containerd"
+	"github.com/containerd/containerd/containers"
+	"github.com/opencontainers/runtime-spec/specs-go"
+)
+
+// WithProfile receives the name of a file stored on disk comprising a json
+// formated seccomp profile, as specified by the opencontainers/runtime-spec.
+// The profile is read from the file, unmarshaled, and set to the spec.
+func WithProfile(profile string) containerd.SpecOpts {
+	return func(_ context.Context, _ *containerd.Client, _ *containers.Container, s *specs.Spec) error {
+		s.Linux.Seccomp = &specs.LinuxSeccomp{}
+		f, err := ioutil.ReadFile(profile)
+		if err != nil {
+			return fmt.Errorf("Cannot load seccomp profile %q: %v", profile, err)
+		}
+		if err := json.Unmarshal(f, s.Linux.Seccomp); err != nil {
+			return fmt.Errorf("Decoding seccomp profile failed %q: %v", profile, err)
+		}
+		return nil
+	}
+}
+
+// WithDefaultProfile sets the default seccomp profile to the spec.
+// Note: must follow the setting of process capabilities
+func WithDefaultProfile() containerd.SpecOpts {
+	return func(_ context.Context, _ *containerd.Client, _ *containers.Container, s *specs.Spec) error {
+		s.Linux.Seccomp = DefaultProfile(s)
+		return nil
+	}
+}