Drop capabilities not needed by Gofer

PiperOrigin-RevId: 199808391
Change-Id: Ib37a4fb6193dc85c1f93bc16769d6aa41854b9d4

1 files changed, 142 insertions, 0 deletions

diff --git a/runsc/cmd/capability.go b/runsc/cmd/capability.go
new file mode 100644
index 000000000..0209feb1b
--- /dev/null
+++ b/runsc/cmd/capability.go
@@ -0,0 +1,142 @@
+// Copyright 2018 Google Inc.
+//
+// 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"
+	"os"
+
+	specs "github.com/opencontainers/runtime-spec/specs-go"
+	"github.com/syndtr/gocapability/capability"
+	"gvisor.googlesource.com/gvisor/pkg/log"
+)
+
+// 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 {
+	setter, err := capability.NewPid2(os.Getpid())
+	if err != nil {
+		return err
+	}
+	if err := setter.Load(); err != nil {
+		return err
+	}
+
+	bounding, err := trimCaps(caps.Bounding, setter)
+	if err != nil {
+		return err
+	}
+	setter.Set(capability.BOUNDS, bounding...)
+
+	effective, err := trimCaps(caps.Effective, setter)
+	if err != nil {
+		return err
+	}
+	setter.Set(capability.EFFECTIVE, effective...)
+
+	permitted, err := trimCaps(caps.Permitted, setter)
+	if err != nil {
+		return err
+	}
+	setter.Set(capability.PERMITTED, permitted...)
+
+	inheritable, err := trimCaps(caps.Inheritable, setter)
+	if err != nil {
+		return err
+	}
+	setter.Set(capability.INHERITABLE, inheritable...)
+
+	ambient, err := trimCaps(caps.Ambient, setter)
+	if err != nil {
+		return err
+	}
+	setter.Set(capability.AMBIENT, ambient...)
+
+	return setter.Apply(capability.CAPS | capability.BOUNDS | capability.AMBS)
+}
+
+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-priviledged 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,
+}