4 files changed, 495 insertions, 0 deletions
diff --git a/runsc/mitigate/cpu.go b/runsc/mitigate/cpu.go
new file mode 100644
index 000000000..ae4ce9579
--- /dev/null
+++ b/runsc/mitigate/cpu.go
@@ -0,0 +1,377 @@
+// Copyright 2021 The gVisor Authors.
+//
+// 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 mitigate
+
+import (
+	"fmt"
+	"io/ioutil"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+const (
+	// constants of coomm
+	meltdown = "cpu_meltdown"
+	l1tf     = "l1tf"
+	mds      = "mds"
+	swapgs   = "swapgs"
+	taa      = "taa"
+)
+
+const (
+	processorKey  = "processor"
+	vendorIDKey   = "vendor_id"
+	cpuFamilyKey  = "cpu family"
+	modelKey      = "model"
+	physicalIDKey = "physical id"
+	coreIDKey     = "core id"
+	bugsKey       = "bugs"
+)
+
+const (
+	cpuOnlineTemplate = "/sys/devices/system/cpu/cpu%d/online"
+)
+
+// cpuSet contains a map of all CPUs on the system, mapped
+// by Physical ID and CoreIDs. threads with the same
+// Core and Physical ID are Hyperthread pairs.
+type cpuSet map[cpuID]*threadGroup
+
+// newCPUSet creates a CPUSet from data read from /proc/cpuinfo.
+func newCPUSet(data []byte, vulnerable func(*thread) bool) (cpuSet, error) {
+	processors, err := getThreads(string(data))
+	if err != nil {
+		return nil, err
+	}
+
+	set := make(cpuSet)
+	for _, p := range processors {
+		// Each ID is of the form physicalID:coreID. Hyperthread pairs
+		// have identical physical and core IDs. We need to match
+		// Hyperthread pairs so that we can shutdown all but one per
+		// pair.
+		core, ok := set[p.id]
+		if !ok {
+			core = &threadGroup{}
+			set[p.id] = core
+		}
+		core.isVulnerable = core.isVulnerable || vulnerable(p)
+		core.threads = append(core.threads, p)
+	}
+	return set, nil
+}
+
+// String implements the String method for CPUSet.
+func (c cpuSet) String() string {
+	ret := ""
+	for _, tg := range c {
+		ret += fmt.Sprintf("%s\n", tg)
+	}
+	return ret
+}
+
+// getRemainingList returns the list of threads that will remain active
+// after mitigation.
+func (c cpuSet) getRemainingList() []*thread {
+	threads := make([]*thread, 0, len(c))
+	for _, core := range c {
+		// If we're vulnerable, take only one thread from the pair.
+		if core.isVulnerable {
+			threads = append(threads, core.threads[0])
+			continue
+		}
+		// Otherwise don't shutdown anything.
+		threads = append(threads, core.threads...)
+	}
+	return threads
+}
+
+// getShutdownList returns the list of threads that will be shutdown on
+// mitigation.
+func (c cpuSet) getShutdownList() []*thread {
+	threads := make([]*thread, 0)
+	for _, core := range c {
+		// Only if we're vulnerable do shutdown anything. In this case,
+		// shutdown all but the first entry.
+		if core.isVulnerable && len(core.threads) > 1 {
+			threads = append(threads, core.threads[1:]...)
+		}
+	}
+	return threads
+}
+
+// threadGroup represents Hyperthread pairs on the same physical/core ID.
+type threadGroup struct {
+	threads      []*thread
+	isVulnerable bool
+}
+
+// String implements the String method for threadGroup.
+func (c *threadGroup) String() string {
+	ret := fmt.Sprintf("ThreadGroup:\nIsVulnerable: %t\n", c.isVulnerable)
+	for _, processor := range c.threads {
+		ret += fmt.Sprintf("%s\n", processor)
+	}
+	return ret
+}
+
+// getThreads returns threads structs from reading /proc/cpuinfo.
+func getThreads(data string) ([]*thread, error) {
+	// Each processor entry should start with the
+	// processor key. Find the beginings of each.
+	r := buildRegex(processorKey, `\d+`)
+	indices := r.FindAllStringIndex(data, -1)
+	if len(indices) < 1 {
+		return nil, fmt.Errorf("no cpus found for: %s", data)
+	}
+
+	// Add the ending index for last entry.
+	indices = append(indices, []int{len(data), -1})
+
+	// Valid cpus are now defined by strings in between
+	// indexes (e.g. data[index[i], index[i+1]]).
+	// There should be len(indicies) - 1 CPUs
+	// since the last index is the end of the string.
+	var cpus = make([]*thread, 0, len(indices)-1)
+	// Find each string that represents a CPU. These begin "processor".
+	for i := 1; i < len(indices); i++ {
+		start := indices[i-1][0]
+		end := indices[i][0]
+		// Parse the CPU entry, which should be between start/end.
+		c, err := newThread(data[start:end])
+		if err != nil {
+			return nil, err
+		}
+		cpus = append(cpus, c)
+	}
+	return cpus, nil
+}
+
+// cpuID for each thread is defined by the physical and
+// core IDs. If equal, two threads are Hyperthread pairs.
+type cpuID struct {
+	physicalID int64
+	coreID     int64
+}
+
+// type cpu represents pertinent info about a cpu.
+type thread struct {
+	processorNumber int64               // the processor number of this CPU.
+	vendorID        string              // the vendorID of CPU (e.g. AuthenticAMD).
+	cpuFamily       int64               // CPU family number (e.g. 6 for CascadeLake/Skylake).
+	model           int64               // CPU model number (e.g. 85 for CascadeLake/Skylake).
+	id              cpuID               // id for this thread
+	bugs            map[string]struct{} // map of vulnerabilities parsed from the 'bugs' field.
+}
+
+// newThread parses a CPU from a single cpu entry from /proc/cpuinfo.
+func newThread(data string) (*thread, error) {
+	processor, err := parseProcessor(data)
+	if err != nil {
+		return nil, err
+	}
+
+	vendorID, err := parseVendorID(data)
+	if err != nil {
+		return nil, err
+	}
+
+	cpuFamily, err := parseCPUFamily(data)
+	if err != nil {
+		return nil, err
+	}
+
+	model, err := parseModel(data)
+	if err != nil {
+		return nil, err
+	}
+
+	physicalID, err := parsePhysicalID(data)
+	if err != nil {
+		return nil, err
+	}
+
+	coreID, err := parseCoreID(data)
+	if err != nil {
+		return nil, err
+	}
+
+	bugs, err := parseBugs(data)
+	if err != nil {
+		return nil, err
+	}
+
+	return &thread{
+		processorNumber: processor,
+		vendorID:        vendorID,
+		cpuFamily:       cpuFamily,
+		model:           model,
+		id: cpuID{
+			physicalID: physicalID,
+			coreID:     coreID,
+		},
+		bugs: bugs,
+	}, nil
+}
+
+// String implements the String method for thread.
+func (t *thread) String() string {
+	template := `CPU: %d
+CPU ID: %+v
+Vendor: %s
+Family/Model: %d/%d
+Bugs: %s
+`
+	bugs := make([]string, 0)
+	for bug := range t.bugs {
+		bugs = append(bugs, bug)
+	}
+
+	return fmt.Sprintf(template, t.processorNumber, t.id, t.vendorID, t.cpuFamily, t.model, strings.Join(bugs, ","))
+}
+
+// shutdown turns off the CPU by writing 0 to /sys/devices/cpu/cpu{N}/online.
+func (t *thread) shutdown() error {
+	cpuPath := fmt.Sprintf(cpuOnlineTemplate, t.processorNumber)
+	return ioutil.WriteFile(cpuPath, []byte{'0'}, 0644)
+}
+
+// List of pertinent side channel vulnerablilites.
+// For mds, see: https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/mds.html.
+var vulnerabilities = []string{
+	meltdown,
+	l1tf,
+	mds,
+	swapgs,
+	taa,
+}
+
+// isVulnerable checks if a CPU is vulnerable to pertinent bugs.
+func (t *thread) isVulnerable() bool {
+	for _, bug := range vulnerabilities {
+		if _, ok := t.bugs[bug]; ok {
+			return true
+		}
+	}
+	return false
+}
+
+// isActive checks if a CPU is active from /sys/devices/system/cpu/cpu{N}/online
+// If the file does not exist (ioutil returns in error), we assume the CPU is on.
+func (t *thread) isActive() bool {
+	cpuPath := fmt.Sprintf(cpuOnlineTemplate, t.processorNumber)
+	data, err := ioutil.ReadFile(cpuPath)
+	if err != nil {
+		return true
+	}
+	return len(data) > 0 && data[0] != '0'
+}
+
+// similarTo checks family/model/bugs fields for equality of two
+// processors.
+func (t *thread) similarTo(other *thread) bool {
+	if t.vendorID != other.vendorID {
+		return false
+	}
+
+	if other.cpuFamily != t.cpuFamily {
+		return false
+	}
+
+	if other.model != t.model {
+		return false
+	}
+
+	if len(other.bugs) != len(t.bugs) {
+		return false
+	}
+
+	for bug := range t.bugs {
+		if _, ok := other.bugs[bug]; !ok {
+			return false
+		}
+	}
+	return true
+}
+
+// parseProcessor grabs the processor field from /proc/cpuinfo output.
+func parseProcessor(data string) (int64, error) {
+	return parseIntegerResult(data, processorKey)
+}
+
+// parseVendorID grabs the vendor_id field from /proc/cpuinfo output.
+func parseVendorID(data string) (string, error) {
+	return parseRegex(data, vendorIDKey, `[\w\d]+`)
+}
+
+// parseCPUFamily grabs the cpu family field from /proc/cpuinfo output.
+func parseCPUFamily(data string) (int64, error) {
+	return parseIntegerResult(data, cpuFamilyKey)
+}
+
+// parseModel grabs the model field from /proc/cpuinfo output.
+func parseModel(data string) (int64, error) {
+	return parseIntegerResult(data, modelKey)
+}
+
+// parsePhysicalID parses the physical id field.
+func parsePhysicalID(data string) (int64, error) {
+	return parseIntegerResult(data, physicalIDKey)
+}
+
+// parseCoreID parses the core id field.
+func parseCoreID(data string) (int64, error) {
+	return parseIntegerResult(data, coreIDKey)
+}
+
+// parseBugs grabs the bugs field from /proc/cpuinfo output.
+func parseBugs(data string) (map[string]struct{}, error) {
+	result, err := parseRegex(data, bugsKey, `[\d\w\s]*`)
+	if err != nil {
+		return nil, err
+	}
+	bugs := strings.Split(result, " ")
+	ret := make(map[string]struct{}, len(bugs))
+	for _, bug := range bugs {
+		ret[bug] = struct{}{}
+	}
+	return ret, nil
+}
+
+// parseIntegerResult parses fields expecting an integer.
+func parseIntegerResult(data, key string) (int64, error) {
+	result, err := parseRegex(data, key, `\d+`)
+	if err != nil {
+		return 0, err
+	}
+	return strconv.ParseInt(result, 0, 64)
+}
+
+// buildRegex builds a regex for parsing each CPU field.
+func buildRegex(key, match string) *regexp.Regexp {
+	reg := fmt.Sprintf(`(?m)^%s\s*:\s*(.*)$`, key)
+	return regexp.MustCompile(reg)
+}
+
+// parseRegex parses data with key inserted into a standard regex template.
+func parseRegex(data, key, match string) (string, error) {
+	r := buildRegex(key, match)
+	matches := r.FindStringSubmatch(data)
+	if len(matches) < 2 {
+		return "", fmt.Errorf("failed to match key %s: %s", key, data)
+	}
+	return matches[1], nil
+}
diff --git a/runsc/mitigate/mitigate.go b/runsc/mitigate/mitigate.go
new file mode 100644
index 000000000..5be66f5f3
--- /dev/null
+++ b/runsc/mitigate/mitigate.go
@@ -0,0 +1,78 @@
+// Copyright 2021 The gVisor Authors.
+//
+// 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 mitigate provides libraries for the mitigate command. The
+// mitigate command mitigates side channel attacks such as MDS. Mitigate
+// shuts down CPUs via /sys/devices/system/cpu/cpu{N}/online. In addition,
+// the mitigate also handles computing available CPU in kubernetes kube_config
+// files.
+package mitigate
+
+import (
+	"fmt"
+
+	"gvisor.dev/gvisor/pkg/log"
+	"gvisor.dev/gvisor/runsc/flag"
+)
+
+// Mitigate handles high level mitigate operations provided to runsc.
+type Mitigate struct {
+	dryRun bool     // Run the command without changing the underlying system.
+	other  mitigate // Struct holds extra mitigate logic.
+}
+
+// Usage implments Usage for cmd.Mitigate.
+func (m Mitigate) Usage() string {
+	usageString := `mitigate [flags]
+
+This command mitigates an underlying system against side channel attacks.
+The command checks /proc/cpuinfo for cpus having key vulnerablilities (meltdown,
+l1tf, mds, swapgs, taa). If cpus are found to have one of the vulnerabilities,
+all but one cpu is shutdown on each core via
+/sys/devices/system/cpu/cpu{N}/online.
+`
+	return usageString + m.other.usage()
+}
+
+// SetFlags sets flags for the command Mitigate.
+func (m Mitigate) SetFlags(f *flag.FlagSet) {
+	f.BoolVar(&m.dryRun, "dryrun", false, "run the command without changing system")
+	m.other.setFlags(f)
+}
+
+// Execute executes the Mitigate command.
+func (m Mitigate) Execute(data []byte) error {
+	set, err := newCPUSet(data, m.other.vulnerable)
+	if err != nil {
+		return err
+	}
+
+	log.Infof("Mitigate found the following CPUs...")
+	log.Infof("%s", set)
+
+	shutdownList := set.getShutdownList()
+	log.Infof("Shutting down threads on thread pairs.")
+	for _, t := range shutdownList {
+		log.Infof("Shutting down thread: %s", t)
+		if m.dryRun {
+			continue
+		}
+		if err := t.shutdown(); err != nil {
+			return fmt.Errorf("error shutting down thread: %s err: %v", t, err)
+		}
+	}
+	log.Infof("Shutdown successful.")
+	m.other.execute(set, m.dryRun)
+	return nil
+}
diff --git a/runsc/mitigate/mitigate_conf.go b/runsc/mitigate/mitigate_conf.go
new file mode 100644
index 000000000..1e74f5891
--- /dev/null
+++ b/runsc/mitigate/mitigate_conf.go
@@ -0,0 +1,37 @@
+// Copyright 2021 The gVisor Authors.
+//
+// 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 mitigate
+
+import (
+	"gvisor.dev/gvisor/runsc/flag"
+)
+
+type mitigate struct {
+}
+
+// usage returns the usage string portion for the mitigate.
+func (m mitigate) usage() string { return "" }
+
+// setFlags sets additional flags for the Mitigate command.
+func (m mitigate) setFlags(f *flag.FlagSet) {}
+
+// execute performs additional parts of Execute for Mitigate.
+func (m mitigate) execute(set cpuSet, dryrun bool) error {
+	return nil
+}
+
+func (m mitigate) vulnerable(other *thread) bool {
+	return other.isVulnerable()
+}
diff --git a/runsc/mitigate/mitigate_state_autogen.go b/runsc/mitigate/mitigate_state_autogen.go
new file mode 100644
index 000000000..14bad0cd6
--- /dev/null
+++ b/runsc/mitigate/mitigate_state_autogen.go
@@ -0,0 +1,3 @@
+// automatically generated by stateify.
+
+package mitigate