internal/worker/govulncheck_scan.go - pkgsite-metrics - Git at Google

 // Copyright 2022 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 package worker

 import (
 	"context"
 	"errors"
 	"fmt"
 	"net/http"
 	"os"
 	"os/exec"
 	"path/filepath"
 	"strconv"
 	"strings"
 	"syscall"
 	"time"

 	"cloud.google.com/go/storage"
 	"golang.org/x/exp/event"
 	"golang.org/x/pkgsite-metrics/internal/bigquery"
 	"golang.org/x/pkgsite-metrics/internal/config"
 	"golang.org/x/pkgsite-metrics/internal/derrors"
 	"golang.org/x/pkgsite-metrics/internal/govulncheck"
 	"golang.org/x/pkgsite-metrics/internal/log"
 	"golang.org/x/pkgsite-metrics/internal/proxy"
 	"golang.org/x/pkgsite-metrics/internal/sandbox"
 	"golang.org/x/pkgsite-metrics/internal/version"
 	vulnclient "golang.org/x/vuln/client"
 	govulncheckapi "golang.org/x/vuln/exp/govulncheck"
 )

 const (
 	// modeImports is used to report results of
 	// vulnerability detection at imports level
 	// precision. It cannot be directly triggered
 	// by scan endpoints. Instead, ModeGovulncheck
 	// mode reports its results to show difference
 	// in precision of vulnerability detection.
 	modeImports string = "IMPORTS"

 	// ModeBinary runs the govulncheck binary in
 	// binary mode.
 	ModeBinary string = "BINARY"

 	// ModeGovulncheck runs the govulncheck binary in
 	// default (source) mode.
 	ModeGovulncheck = "GOVULNCHECK"
 )

 // modes is a set of supported vulncheck modes
 var modes = map[string]bool{
 	ModeBinary:      true,
 	ModeGovulncheck: true,
 }

 func IsValidGovulncheckMode(mode string) bool {
 	return modes[mode]
 }

 // TODO(b/241402488): shouldSkip is the list of modules that we are not
 // currently scanning due to previous issues that need investigation.
 var shouldSkip = map[string]bool{}

 var scanCounter = event.NewCounter("scans", &event.MetricOptions{Namespace: metricNamespace})

 // path: /govulncheck/scan/MODULE_VERSION_SUFFIX?params
 // See internal/govulncheck.ParseRequest for allowed path forms and query params.
 func (h *GovulncheckServer) handleScan(w http.ResponseWriter, r *http.Request) (err error) {
 	defer derrors.Wrap(&err, "handleScan")

 	defer func() {
 		scanCounter.Record(r.Context(), 1, event.Bool("success", err == nil))
 	}()

 	ctx := r.Context()
 	sreq, err := govulncheck.ParseRequest(r, "/govulncheck/scan")
 	if err != nil {
 		return fmt.Errorf("%w: %v", derrors.InvalidArgument, err)
 	}
 	if sreq.Mode == "" {
 		sreq.Mode = ModeGovulncheck
 	}
 	if shouldSkip[sreq.Module] {
 		log.Infof(ctx, "skipping (module in shouldSkip list): %s", sreq.Path())
 		return nil
 	}
 	if err := h.readGovulncheckWorkVersions(ctx); err != nil {
 		return err
 	}
 	scanner, err := newScanner(ctx, h)
 	if err != nil {
 		return err
 	}
 	// An explicit "insecure" query param overrides the default.
 	if sreq.Insecure {
 		scanner.insecure = sreq.Insecure
 	}
 	wv := h.storedWorkVersions[[2]string{sreq.Module, sreq.Version}]
 	if scanner.workVersion.Equal(wv) {
 		log.Infof(ctx, "skipping (work version unchanged): %s@%s", sreq.Module, sreq.Version)
 		return nil
 	}

 	return scanner.ScanModule(ctx, w, sreq)
 }

 func (h *GovulncheckServer) readGovulncheckWorkVersions(ctx context.Context) error {
 	h.mu.Lock()
 	defer h.mu.Unlock()
 	if h.storedWorkVersions != nil {
 		return nil
 	}
 	if h.bqClient == nil {
 		return nil
 	}
 	var err error
 	h.storedWorkVersions, err = govulncheck.ReadWorkVersions(ctx, h.bqClient)
 	return err
 }

 // A scanner holds state for scanning modules.
 type scanner struct {
 	proxyClient *proxy.Client
 	dbClient    vulnclient.Client
 	bqClient    *bigquery.Client
 	workVersion *govulncheck.WorkVersion
 	goMemLimit  uint64
 	gcsBucket   *storage.BucketHandle
 	insecure    bool
 	sbox        *sandbox.Sandbox
 }

 func newScanner(ctx context.Context, h *GovulncheckServer) (*scanner, error) {
 	workVersion, err := h.getWorkVersion(ctx)
 	if err != nil {
 		return nil, err
 	}
 	var bucket *storage.BucketHandle
 	if h.cfg.BinaryBucket != "" {
 		c, err := storage.NewClient(ctx)
 		if err != nil {
 			return nil, err
 		}
 		bucket = c.Bucket(h.cfg.BinaryBucket)
 	}
 	sbox := sandbox.New("/bundle")
 	sbox.Runsc = "/usr/local/bin/runsc"
 	return &scanner{
 		proxyClient: h.proxyClient,
 		bqClient:    h.bqClient,
 		dbClient:    h.vulndbClient,
 		workVersion: workVersion,
 		goMemLimit:  parseGoMemLimit(os.Getenv("GOMEMLIMIT")),
 		gcsBucket:   bucket,
 		insecure:    h.cfg.Insecure,
 		sbox:        sbox,
 	}, nil
 }

 type scanError struct {
 	err error
 }

 func (s scanError) Error() string {
 	return s.err.Error()
 }

 func (s scanError) Unwrap() error {
 	return s.err
 }

 func (s *scanner) ScanModule(ctx context.Context, w http.ResponseWriter, sreq *govulncheck.Request) error {
 	if sreq.Module == "std" {
 		return nil // ignore the standard library
 	}
 	row := &govulncheck.Result{
 		ModulePath:  sreq.Module,
 		Suffix:      sreq.Suffix,
 		WorkVersion: *s.workVersion,
 	}
 	// Scan the version.
 	log.Debugf(ctx, "fetching proxy info: %s@%s", sreq.Path(), sreq.Version)
 	info, err := s.proxyClient.Info(ctx, sreq.Module, sreq.Version)
 	if err != nil {
 		log.Errorf(ctx, err, "proxy error")
 		row.AddError(fmt.Errorf("%v: %w", err, derrors.ProxyError))
 		return nil
 	}
 	row.Version = info.Version
 	row.SortVersion = version.ForSorting(row.Version)
 	row.CommitTime = info.Time
 	row.ImportedBy = sreq.ImportedBy
 	row.VulnDBLastModified = s.workVersion.VulnDBLastModified
 	row.ScanMode = sreq.Mode

 	log.Infof(ctx, "running scanner.runScanModule: %s@%s", sreq.Path(), sreq.Version)
 	stats := &scanStats{}
 	vulns, err := s.runScanModule(ctx, sreq.Module, info.Version, sreq.Suffix, sreq.Mode, stats)
 	row.ScanSeconds = stats.scanSeconds
 	row.ScanMemory = int64(stats.scanMemory)
 	row.Workers = config.GetEnvInt("CLOUD_RUN_CONCURRENCY", "0", -1)
 	if err != nil {
 		switch {
 		case errors.Is(err, derrors.LoadPackagesNoGoModError) ||
 			errors.Is(err, derrors.LoadPackagesNoGoSumError):
 			// errors already classified by package loading.
 		case isMissingGoMod(err):
 			// specific for govulncheck
 			err = fmt.Errorf("%v: %w", err, derrors.LoadPackagesNoGoModError)
 		case isNoRequiredModule(err):
 			err = fmt.Errorf("%v: %w", err, derrors.LoadPackagesNoRequiredModuleError)
 		case isMissingGoSumEntry(err):
 			err = fmt.Errorf("%v: %w", err, derrors.LoadPackagesMissingGoSumEntryError)
 		case errors.Is(err, derrors.LoadPackagesError):
 			// general load packages error
 		case isVulnDBConnection(err):
 			err = fmt.Errorf("%v: %w", err, derrors.ScanModuleGovulncheckDBConnectionError)
 		default:
 			err = fmt.Errorf("%v: %w", err, derrors.ScanModuleGovulncheckError)
 		}
 		row.AddError(err)
 	} else {
 		row.Vulns = vulnsForMode(vulns, sreq.Mode)
 	}
 	log.Infof(ctx, "scanner.runScanModule returned %d vulns for %s: row.Vulns=%d err=%v", len(vulns), sreq.Path(), len(row.Vulns), err)

 	if err := writeResult(ctx, sreq.Serve, w, s.bqClient, govulncheck.TableName, row); err != nil {
 		return err
 	}

 	if sreq.Mode != ModeGovulncheck {
 		return nil
 	}
 	// For ModeGovulncheck, add the copy of row and report
 	// each vulnerability as imported. We set the performance
 	// numbers to 0 since we don't actually perform a scan
 	// at the level of import chains. Also makes a copy if
 	// the original row has an error and no vulns.
 	impRow := *row
 	impRow.ScanMode = modeImports
 	impRow.ScanSeconds = 0
 	impRow.ScanMemory = 0
 	impRow.Vulns = vulnsForMode(vulns, modeImports)
 	log.Infof(ctx, "scanner.runScanModule also storing imports vulns for %s: row.Vulns=%d", sreq.Path(), len(impRow.Vulns))
 	return writeResult(ctx, sreq.Serve, w, s.bqClient, govulncheck.TableName, &impRow)
 }

 // vulnsForMode returns vulns that make sense to report for
 // a particular mode.
 //
 // For ModeGovulncheck, these are all vulns that are actually
 // called (CallSink!=0). For modeImports, these are all vulns
 // modified to have CallSink=0. For ModeBinary, these are
 // exactly the input vulns since binary analysis does not
 // distinguish between called and imported vulnerabilities.
 func vulnsForMode(vulns []*govulncheck.Vuln, mode string) []*govulncheck.Vuln {
 	if mode == ModeBinary {
 		return vulns
 	}

 	var vs []*govulncheck.Vuln
 	for _, v := range vulns {
 		if mode == ModeGovulncheck {
 			// Return only the called vulns for ModeGovulncheck.
 			if v.CallSink.Valid && v.CallSink.Int64 != 0 {
 				vs = append(vs, v)
 			}
 		} else if mode == modeImports {
 			// For imports mode, return the vulnerability as it
 			// is imported, but not called.
 			nv := *v
 			nv.CallSink = bigquery.NullInt(0)
 			vs = append(vs, &nv)
 		} else {
 			panic(fmt.Sprintf("vulnsForMode unsupported mode %s", mode))
 		}
 	}
 	return vs
 }

 type scanStats struct {
 	scanSeconds float64
 	scanMemory  uint64
 }

 // Inside the sandbox, the user is root and their $HOME directory is /root.
 const (
 	// The Go cache resides in its default location, $HOME/.cache/go-build.
 	sandboxGoCache = "root/.cache/go-build"
 	// Where the govulncheck binary lives.
 	govulncheckPath = binaryDir + "/govulncheck"
 )

 // runScanModule fetches the module version from the proxy, and analyzes it for
 // vulnerabilities.
 func (s *scanner) runScanModule(ctx context.Context, modulePath, version, binaryDir, mode string, stats *scanStats) (bvulns []*govulncheck.Vuln, err error) {
 	err = doScan(ctx, modulePath, version, s.insecure, func() error {
 		var vulns []*govulncheckapi.Vuln
 		if s.insecure {
 			vulns, err = s.runGovulncheckScanInsecure(ctx, modulePath, version, binaryDir, mode, stats)
 		} else {
 			vulns, err = s.runGovulncheckScanSandbox(ctx, modulePath, version, binaryDir, mode, stats)
 		}
 		if err != nil {
 			return err
 		}
 		for _, v := range vulns {
 			bvulns = append(bvulns, govulncheck.ConvertGovulncheckOutput(v)...)
 		}
 		return nil
 	})
 	return bvulns, err
 }

 func (s *scanner) runGovulncheckScanSandbox(ctx context.Context, modulePath, version, binDir, mode string, stats *scanStats) (_ []*govulncheckapi.Vuln, err error) {
 	if mode == ModeBinary {
 		return s.runBinaryScanSandbox(ctx, modulePath, version, binDir, stats)
 	}

 	mdir := moduleDir(modulePath, version)
 	defer cleanup(&err, func() error { return os.RemoveAll(mdir) })
 	const insecure = false
 	if err := prepareModule(ctx, modulePath, version, mdir, s.proxyClient, insecure); err != nil {
 		return nil, err
 	}

 	log.Infof(ctx, "running govulncheck in sandbox: %s@%s", modulePath, version)
 	smdir := strings.TrimPrefix(mdir, sandboxRoot)
 	err = s.sbox.Validate()
 	log.Debugf(ctx, "sandbox Validate returned %v", err)
 	if err != nil {
 		return nil, err
 	}

 	stdout, err := s.sbox.Command(binaryDir+"/govulncheck_sandbox", govulncheckPath, ModeGovulncheck, smdir).Output()
 	log.Infof(ctx, "done with govulncheck in sandbox: %s@%s err=%v", modulePath, version, err)

 	if err != nil {
 		return nil, errors.New(derrors.IncludeStderr(err))
 	}
 	response, err := govulncheck.UnmarshalSandboxResponse(stdout)
 	if err != nil {
 		return nil, err
 	}
 	stats.scanMemory = response.Stats.ScanMemory
 	stats.scanSeconds = response.Stats.ScanSeconds
 	log.Debugf(ctx, "govulncheck stats: %dkb | Seconds: %vs", stats.scanMemory, stats.scanSeconds)
 	return response.Res.Vulns, nil
 }

 func (s *scanner) runBinaryScanSandbox(ctx context.Context, modulePath, version, binDir string, stats *scanStats) ([]*govulncheckapi.Vuln, error) {
 	if s.gcsBucket == nil {
 		return nil, errors.New("binary bucket not configured; set GO_ECOSYSTEM_BINARY_BUCKET")
 	}
 	// Copy the binary from GCS to the local disk, because vulncheck.Binary
 	// ultimately requires a ReaderAt and GCS doesn't provide that.
 	gcsPathname := fmt.Sprintf("%s/%s@%s/%s", gcsBinaryDir, modulePath, version, binDir)
 	const destDir = binaryDir
 	log.Debug(ctx, "copying",
 		"from", gcsPathname,
 		"to", destDir,
 		"module", modulePath, "version", version,
 		"dir", binDir)
 	destf, err := os.CreateTemp(destDir, "govulncheck-binary-")
 	if err != nil {
 		return nil, err
 	}
 	defer os.Remove(destf.Name())
 	rc, err := s.gcsBucket.Object(gcsPathname).NewReader(ctx)
 	if err != nil {
 		return nil, err
 	}
 	defer rc.Close()
 	if err := copyAndClose(destf, rc); err != nil {
 		return nil, err
 	}

 	log.Infof(ctx, "running govulncheck in sandbox on %s: %s@%s/%s", modulePath, version, binDir, destf.Name())
 	stdout, err := s.sbox.Command(binaryDir+"/govulncheck_sandbox", govulncheckPath, ModeBinary, destf.Name()).Output()
 	log.Infof(ctx, "done with govulncheck in sandbox on %s: %s@%s/%s err=%v", modulePath, version, binDir, destf.Name(), err)

 	if err != nil {
 		return nil, errors.New(derrors.IncludeStderr(err))
 	}
 	response, err := govulncheck.UnmarshalSandboxResponse(stdout)
 	if err != nil {
 		return nil, err
 	}
 	stats.scanMemory = response.Stats.ScanMemory
 	stats.scanSeconds = response.Stats.ScanSeconds
 	log.Debugf(ctx, "govulncheck stats: %dkb | Seconds: %vs", stats.scanMemory, stats.scanSeconds)
 	return response.Res.Vulns, nil
 }

 func (s *scanner) runGovulncheckScanInsecure(ctx context.Context, modulePath, version, binaryDir, mode string, stats *scanStats) (_ []*govulncheckapi.Vuln, err error) {
 	if mode == ModeBinary {
 		return s.runBinaryScanInsecure(ctx, modulePath, version, binaryDir, os.TempDir(), stats)
 	}

 	mdir := moduleDir(modulePath, version)
 	defer cleanup(&err, func() error { return os.RemoveAll(mdir) })
 	if err := prepareModule(ctx, modulePath, version, mdir, s.proxyClient, true); err != nil {
 		return nil, err
 	}
 	vulns, err := runGovulncheckCmd("./...", mdir, stats)
 	if err != nil {
 		return nil, err
 	}
 	return vulns, nil
 }

 func (s *scanner) runBinaryScanInsecure(ctx context.Context, modulePath, version, binDir, tempDir string, stats *scanStats) ([]*govulncheckapi.Vuln, error) {
 	if s.gcsBucket == nil {
 		return nil, errors.New("binary bucket not configured; set GO_ECOSYSTEM_BINARY_BUCKET")
 	}
 	// Copy the binary from GCS to the local disk, because govulncheck
 	// ultimately requires a ReaderAt and GCS doesn't provide that.
 	gcsPathname := fmt.Sprintf("%s/%s@%s/%s", gcsBinaryDir, modulePath, version, binDir)
 	log.Debug(ctx, "copying to temp dir",
 		"from", gcsPathname, "module", modulePath, "version", version, "dir", binDir)
 	localPathname := filepath.Join(tempDir, "binary")
 	if err := copyToLocalFile(localPathname, false, gcsPathname, gcsOpenFileFunc(ctx, s.gcsBucket)); err != nil {
 		return nil, err
 	}

 	vulns, err := runGovulncheckCmd(localPathname, "", stats)
 	if err != nil {
 		return nil, err
 	}
 	return vulns, nil
 }

 func runGovulncheckCmd(pattern, tempDir string, stats *scanStats) ([]*govulncheckapi.Vuln, error) {
 	govulncheckName := govulncheckPath
 	if !fileExists(govulncheckName) {
 		govulncheckName = "govulncheck"
 	}

 	start := time.Now()
 	govulncheckCmd := exec.Command(govulncheckName, "-json", pattern)
 	govulncheckCmd.Dir = tempDir
 	output, err := govulncheckCmd.Output()
 	if e := (&exec.ExitError{}); !errors.As(err, &e) && e.ProcessState.ExitCode() != 3 {
 		return nil, err
 	}
 	stats.scanSeconds = time.Since(start).Seconds()
 	stats.scanMemory = uint64(govulncheckCmd.ProcessState.SysUsage().(*syscall.Rusage).Maxrss)

 	res, err := govulncheck.UnmarshalGovulncheckResult(output)
 	if err != nil {
 		return nil, err
 	}
 	return res.Vulns, nil
 }

 func isNoRequiredModule(err error) bool {
 	return strings.Contains(err.Error(), "no required module")
 }

 func isMissingGoSumEntry(err error) bool {
 	return strings.Contains(err.Error(), "missing go.sum entry")
 }

 func isMissingGoMod(err error) bool {
 	return strings.Contains(err.Error(), "no go.mod file")
 }

 func isVulnDBConnection(err error) bool {
 	s := err.Error()
 	return strings.Contains(s, "https://vuln.go.dev") &&
 		strings.Contains(s, "connection")
 }

 // parseGoMemLimit parses the GOMEMLIMIT environment variable.
 // It returns 0 if the variable isn't set or its value is malformed.
 func parseGoMemLimit(s string) uint64 {
 	if len(s) < 2 {
 		return 0
 	}
 	m := uint64(1)
 	if s[len(s)-1] == 'i' {
 		switch s[len(s)-2] {
 		case 'K':
 			m = 1024
 		case 'M':
 			m = 1024 * 1024
 		case 'G':
 			m = 1024 * 1024 * 1024
 		default:
 			return 0
 		}
 		s = s[:len(s)-2]
 	}
 	v, err := strconv.ParseUint(s, 10, 64)
 	if err != nil {
 		return 0
 	}
 	return v * m
 }

 // fileExists checks if file path exists. Returns true
 // if the file exists or it cannot prove that it does
 // not exist. Otherwise, returns false.
 func fileExists(file string) bool {
 	if _, err := os.Stat(file); err == nil {
 		return true
 	} else if errors.Is(err, os.ErrNotExist) {
 		return false
 	}
 	// Conservatively return true if os.Stat fails
 	// for some other reason.
 	return true
 }
	// Copyright 2022 The Go Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style
	// license that can be found in the LICENSE file.

	package worker

	import (
	"context"
	"errors"
	"fmt"
	"net/http"
	"os"
	"os/exec"
	"path/filepath"
	"strconv"
	"strings"
	"syscall"
	"time"

	"cloud.google.com/go/storage"
	"golang.org/x/exp/event"
	"golang.org/x/pkgsite-metrics/internal/bigquery"
	"golang.org/x/pkgsite-metrics/internal/config"
	"golang.org/x/pkgsite-metrics/internal/derrors"
	"golang.org/x/pkgsite-metrics/internal/govulncheck"
	"golang.org/x/pkgsite-metrics/internal/log"
	"golang.org/x/pkgsite-metrics/internal/proxy"
	"golang.org/x/pkgsite-metrics/internal/sandbox"
	"golang.org/x/pkgsite-metrics/internal/version"
	vulnclient "golang.org/x/vuln/client"
	govulncheckapi "golang.org/x/vuln/exp/govulncheck"
	)

	const (
	// modeImports is used to report results of
	// vulnerability detection at imports level
	// precision. It cannot be directly triggered
	// by scan endpoints. Instead, ModeGovulncheck
	// mode reports its results to show difference
	// in precision of vulnerability detection.
	modeImports string = "IMPORTS"

	// ModeBinary runs the govulncheck binary in
	// binary mode.
	ModeBinary string = "BINARY"

	// ModeGovulncheck runs the govulncheck binary in
	// default (source) mode.
	ModeGovulncheck = "GOVULNCHECK"
	)

	// modes is a set of supported vulncheck modes
	var modes = map[string]bool{
	ModeBinary: true,
	ModeGovulncheck: true,
	}

	func IsValidGovulncheckMode(mode string) bool {
	return modes[mode]
	}

	// TODO(b/241402488): shouldSkip is the list of modules that we are not
	// currently scanning due to previous issues that need investigation.
	var shouldSkip = map[string]bool{}

	var scanCounter = event.NewCounter("scans", &event.MetricOptions{Namespace: metricNamespace})

	// path: /govulncheck/scan/MODULE_VERSION_SUFFIX?params
	// See internal/govulncheck.ParseRequest for allowed path forms and query params.
	func (h GovulncheckServer) handleScan(w http.ResponseWriter, r http.Request) (err error) {
	defer derrors.Wrap(&err, "handleScan")

	defer func() {
	scanCounter.Record(r.Context(), 1, event.Bool("success", err == nil))
	}()

	ctx := r.Context()
	sreq, err := govulncheck.ParseRequest(r, "/govulncheck/scan")
	if err != nil {
	return fmt.Errorf("%w: %v", derrors.InvalidArgument, err)
	}
	if sreq.Mode == "" {
	sreq.Mode = ModeGovulncheck
	}
	if shouldSkip[sreq.Module] {
	log.Infof(ctx, "skipping (module in shouldSkip list): %s", sreq.Path())
	return nil
	}
	if err := h.readGovulncheckWorkVersions(ctx); err != nil {
	return err
	}
	scanner, err := newScanner(ctx, h)
	if err != nil {
	return err
	}
	// An explicit "insecure" query param overrides the default.
	if sreq.Insecure {
	scanner.insecure = sreq.Insecure
	}
	wv := h.storedWorkVersions[[2]string{sreq.Module, sreq.Version}]
	if scanner.workVersion.Equal(wv) {
	log.Infof(ctx, "skipping (work version unchanged): %s@%s", sreq.Module, sreq.Version)
	return nil
	}

	return scanner.ScanModule(ctx, w, sreq)
	}

	func (h *GovulncheckServer) readGovulncheckWorkVersions(ctx context.Context) error {
	h.mu.Lock()
	defer h.mu.Unlock()
	if h.storedWorkVersions != nil {
	return nil
	}
	if h.bqClient == nil {
	return nil
	}
	var err error
	h.storedWorkVersions, err = govulncheck.ReadWorkVersions(ctx, h.bqClient)
	return err
	}

	// A scanner holds state for scanning modules.
	type scanner struct {
	proxyClient *proxy.Client
	dbClient vulnclient.Client
	bqClient *bigquery.Client
	workVersion *govulncheck.WorkVersion
	goMemLimit uint64
	gcsBucket *storage.BucketHandle
	insecure bool
	sbox *sandbox.Sandbox
	}

	func newScanner(ctx context.Context, h GovulncheckServer) (scanner, error) {
	workVersion, err := h.getWorkVersion(ctx)
	if err != nil {
	return nil, err
	}
	var bucket *storage.BucketHandle
	if h.cfg.BinaryBucket != "" {
	c, err := storage.NewClient(ctx)
	if err != nil {
	return nil, err
	}
	bucket = c.Bucket(h.cfg.BinaryBucket)
	}
	sbox := sandbox.New("/bundle")
	sbox.Runsc = "/usr/local/bin/runsc"
	return &scanner{
	proxyClient: h.proxyClient,
	bqClient: h.bqClient,
	dbClient: h.vulndbClient,
	workVersion: workVersion,
	goMemLimit: parseGoMemLimit(os.Getenv("GOMEMLIMIT")),
	gcsBucket: bucket,
	insecure: h.cfg.Insecure,
	sbox: sbox,
	}, nil
	}

	type scanError struct {
	err error
	}

	func (s scanError) Error() string {
	return s.err.Error()
	}

	func (s scanError) Unwrap() error {
	return s.err
	}

	func (s scanner) ScanModule(ctx context.Context, w http.ResponseWriter, sreq govulncheck.Request) error {
	if sreq.Module == "std" {
	return nil // ignore the standard library
	}
	row := &govulncheck.Result{
	ModulePath: sreq.Module,
	Suffix: sreq.Suffix,
	WorkVersion: *s.workVersion,
	}
	// Scan the version.
	log.Debugf(ctx, "fetching proxy info: %s@%s", sreq.Path(), sreq.Version)
	info, err := s.proxyClient.Info(ctx, sreq.Module, sreq.Version)
	if err != nil {
	log.Errorf(ctx, err, "proxy error")
	row.AddError(fmt.Errorf("%v: %w", err, derrors.ProxyError))
	return nil
	}
	row.Version = info.Version
	row.SortVersion = version.ForSorting(row.Version)
	row.CommitTime = info.Time
	row.ImportedBy = sreq.ImportedBy
	row.VulnDBLastModified = s.workVersion.VulnDBLastModified
	row.ScanMode = sreq.Mode

	log.Infof(ctx, "running scanner.runScanModule: %s@%s", sreq.Path(), sreq.Version)
	stats := &scanStats{}
	vulns, err := s.runScanModule(ctx, sreq.Module, info.Version, sreq.Suffix, sreq.Mode, stats)
	row.ScanSeconds = stats.scanSeconds
	row.ScanMemory = int64(stats.scanMemory)
	row.Workers = config.GetEnvInt("CLOUD_RUN_CONCURRENCY", "0", -1)
	if err != nil {
	switch {
	case errors.Is(err, derrors.LoadPackagesNoGoModError) \|\|
	errors.Is(err, derrors.LoadPackagesNoGoSumError):
	// errors already classified by package loading.
	case isMissingGoMod(err):
	// specific for govulncheck
	err = fmt.Errorf("%v: %w", err, derrors.LoadPackagesNoGoModError)
	case isNoRequiredModule(err):
	err = fmt.Errorf("%v: %w", err, derrors.LoadPackagesNoRequiredModuleError)
	case isMissingGoSumEntry(err):
	err = fmt.Errorf("%v: %w", err, derrors.LoadPackagesMissingGoSumEntryError)
	case errors.Is(err, derrors.LoadPackagesError):
	// general load packages error
	case isVulnDBConnection(err):
	err = fmt.Errorf("%v: %w", err, derrors.ScanModuleGovulncheckDBConnectionError)
	default:
	err = fmt.Errorf("%v: %w", err, derrors.ScanModuleGovulncheckError)
	}
	row.AddError(err)
	} else {
	row.Vulns = vulnsForMode(vulns, sreq.Mode)
	}
	log.Infof(ctx, "scanner.runScanModule returned %d vulns for %s: row.Vulns=%d err=%v", len(vulns), sreq.Path(), len(row.Vulns), err)

	if err := writeResult(ctx, sreq.Serve, w, s.bqClient, govulncheck.TableName, row); err != nil {
	return err
	}

	if sreq.Mode != ModeGovulncheck {
	return nil
	}
	// For ModeGovulncheck, add the copy of row and report
	// each vulnerability as imported. We set the performance
	// numbers to 0 since we don't actually perform a scan
	// at the level of import chains. Also makes a copy if
	// the original row has an error and no vulns.
	impRow := *row
	impRow.ScanMode = modeImports
	impRow.ScanSeconds = 0
	impRow.ScanMemory = 0
	impRow.Vulns = vulnsForMode(vulns, modeImports)
	log.Infof(ctx, "scanner.runScanModule also storing imports vulns for %s: row.Vulns=%d", sreq.Path(), len(impRow.Vulns))
	return writeResult(ctx, sreq.Serve, w, s.bqClient, govulncheck.TableName, &impRow)
	}

	// vulnsForMode returns vulns that make sense to report for
	// a particular mode.
	//
	// For ModeGovulncheck, these are all vulns that are actually
	// called (CallSink!=0). For modeImports, these are all vulns
	// modified to have CallSink=0. For ModeBinary, these are
	// exactly the input vulns since binary analysis does not
	// distinguish between called and imported vulnerabilities.
	func vulnsForMode(vulns []govulncheck.Vuln, mode string) []govulncheck.Vuln {
	if mode == ModeBinary {
	return vulns
	}

	var vs []*govulncheck.Vuln
	for _, v := range vulns {
	if mode == ModeGovulncheck {
	// Return only the called vulns for ModeGovulncheck.
	if v.CallSink.Valid && v.CallSink.Int64 != 0 {
	vs = append(vs, v)
	}
	} else if mode == modeImports {
	// For imports mode, return the vulnerability as it
	// is imported, but not called.
	nv := *v
	nv.CallSink = bigquery.NullInt(0)
	vs = append(vs, &nv)
	} else {
	panic(fmt.Sprintf("vulnsForMode unsupported mode %s", mode))
	}
	}
	return vs
	}

	type scanStats struct {
	scanSeconds float64
	scanMemory uint64
	}

	// Inside the sandbox, the user is root and their $HOME directory is /root.
	const (
	// The Go cache resides in its default location, $HOME/.cache/go-build.
	sandboxGoCache = "root/.cache/go-build"
	// Where the govulncheck binary lives.
	govulncheckPath = binaryDir + "/govulncheck"
	)

	// runScanModule fetches the module version from the proxy, and analyzes it for
	// vulnerabilities.
	func (s scanner) runScanModule(ctx context.Context, modulePath, version, binaryDir, mode string, stats scanStats) (bvulns []*govulncheck.Vuln, err error) {
	err = doScan(ctx, modulePath, version, s.insecure, func() error {
	var vulns []*govulncheckapi.Vuln
	if s.insecure {
	vulns, err = s.runGovulncheckScanInsecure(ctx, modulePath, version, binaryDir, mode, stats)
	} else {
	vulns, err = s.runGovulncheckScanSandbox(ctx, modulePath, version, binaryDir, mode, stats)
	}
	if err != nil {
	return err
	}
	for _, v := range vulns {
	bvulns = append(bvulns, govulncheck.ConvertGovulncheckOutput(v)...)
	}
	return nil
	})
	return bvulns, err
	}

	func (s scanner) runGovulncheckScanSandbox(ctx context.Context, modulePath, version, binDir, mode string, stats scanStats) (_ []*govulncheckapi.Vuln, err error) {
	if mode == ModeBinary {
	return s.runBinaryScanSandbox(ctx, modulePath, version, binDir, stats)
	}

	mdir := moduleDir(modulePath, version)
	defer cleanup(&err, func() error { return os.RemoveAll(mdir) })
	const insecure = false
	if err := prepareModule(ctx, modulePath, version, mdir, s.proxyClient, insecure); err != nil {
	return nil, err
	}

	log.Infof(ctx, "running govulncheck in sandbox: %s@%s", modulePath, version)
	smdir := strings.TrimPrefix(mdir, sandboxRoot)
	err = s.sbox.Validate()
	log.Debugf(ctx, "sandbox Validate returned %v", err)
	if err != nil {
	return nil, err
	}

	stdout, err := s.sbox.Command(binaryDir+"/govulncheck_sandbox", govulncheckPath, ModeGovulncheck, smdir).Output()
	log.Infof(ctx, "done with govulncheck in sandbox: %s@%s err=%v", modulePath, version, err)

	if err != nil {
	return nil, errors.New(derrors.IncludeStderr(err))
	}
	response, err := govulncheck.UnmarshalSandboxResponse(stdout)
	if err != nil {
	return nil, err
	}
	stats.scanMemory = response.Stats.ScanMemory
	stats.scanSeconds = response.Stats.ScanSeconds
	log.Debugf(ctx, "govulncheck stats: %dkb \| Seconds: %vs", stats.scanMemory, stats.scanSeconds)
	return response.Res.Vulns, nil
	}

	func (s scanner) runBinaryScanSandbox(ctx context.Context, modulePath, version, binDir string, stats scanStats) ([]*govulncheckapi.Vuln, error) {
	if s.gcsBucket == nil {
	return nil, errors.New("binary bucket not configured; set GO_ECOSYSTEM_BINARY_BUCKET")
	}
	// Copy the binary from GCS to the local disk, because vulncheck.Binary
	// ultimately requires a ReaderAt and GCS doesn't provide that.
	gcsPathname := fmt.Sprintf("%s/%s@%s/%s", gcsBinaryDir, modulePath, version, binDir)
	const destDir = binaryDir
	log.Debug(ctx, "copying",
	"from", gcsPathname,
	"to", destDir,
	"module", modulePath, "version", version,
	"dir", binDir)
	destf, err := os.CreateTemp(destDir, "govulncheck-binary-")
	if err != nil {
	return nil, err
	}
	defer os.Remove(destf.Name())
	rc, err := s.gcsBucket.Object(gcsPathname).NewReader(ctx)
	if err != nil {
	return nil, err
	}
	defer rc.Close()
	if err := copyAndClose(destf, rc); err != nil {
	return nil, err
	}

	log.Infof(ctx, "running govulncheck in sandbox on %s: %s@%s/%s", modulePath, version, binDir, destf.Name())
	stdout, err := s.sbox.Command(binaryDir+"/govulncheck_sandbox", govulncheckPath, ModeBinary, destf.Name()).Output()
	log.Infof(ctx, "done with govulncheck in sandbox on %s: %s@%s/%s err=%v", modulePath, version, binDir, destf.Name(), err)

	if err != nil {
	return nil, errors.New(derrors.IncludeStderr(err))
	}
	response, err := govulncheck.UnmarshalSandboxResponse(stdout)
	if err != nil {
	return nil, err
	}
	stats.scanMemory = response.Stats.ScanMemory
	stats.scanSeconds = response.Stats.ScanSeconds
	log.Debugf(ctx, "govulncheck stats: %dkb \| Seconds: %vs", stats.scanMemory, stats.scanSeconds)
	return response.Res.Vulns, nil
	}

	func (s scanner) runGovulncheckScanInsecure(ctx context.Context, modulePath, version, binaryDir, mode string, stats scanStats) (_ []*govulncheckapi.Vuln, err error) {
	if mode == ModeBinary {
	return s.runBinaryScanInsecure(ctx, modulePath, version, binaryDir, os.TempDir(), stats)
	}

	mdir := moduleDir(modulePath, version)
	defer cleanup(&err, func() error { return os.RemoveAll(mdir) })
	if err := prepareModule(ctx, modulePath, version, mdir, s.proxyClient, true); err != nil {
	return nil, err
	}
	vulns, err := runGovulncheckCmd("./...", mdir, stats)
	if err != nil {
	return nil, err
	}
	return vulns, nil
	}

	func (s scanner) runBinaryScanInsecure(ctx context.Context, modulePath, version, binDir, tempDir string, stats scanStats) ([]*govulncheckapi.Vuln, error) {
	if s.gcsBucket == nil {
	return nil, errors.New("binary bucket not configured; set GO_ECOSYSTEM_BINARY_BUCKET")
	}
	// Copy the binary from GCS to the local disk, because govulncheck
	// ultimately requires a ReaderAt and GCS doesn't provide that.
	gcsPathname := fmt.Sprintf("%s/%s@%s/%s", gcsBinaryDir, modulePath, version, binDir)
	log.Debug(ctx, "copying to temp dir",
	"from", gcsPathname, "module", modulePath, "version", version, "dir", binDir)
	localPathname := filepath.Join(tempDir, "binary")
	if err := copyToLocalFile(localPathname, false, gcsPathname, gcsOpenFileFunc(ctx, s.gcsBucket)); err != nil {
	return nil, err
	}

	vulns, err := runGovulncheckCmd(localPathname, "", stats)
	if err != nil {
	return nil, err
	}
	return vulns, nil
	}

	func runGovulncheckCmd(pattern, tempDir string, stats scanStats) ([]govulncheckapi.Vuln, error) {
	govulncheckName := govulncheckPath
	if !fileExists(govulncheckName) {
	govulncheckName = "govulncheck"
	}

	start := time.Now()
	govulncheckCmd := exec.Command(govulncheckName, "-json", pattern)
	govulncheckCmd.Dir = tempDir
	output, err := govulncheckCmd.Output()
	if e := (&exec.ExitError{}); !errors.As(err, &e) && e.ProcessState.ExitCode() != 3 {
	return nil, err
	}
	stats.scanSeconds = time.Since(start).Seconds()
	stats.scanMemory = uint64(govulncheckCmd.ProcessState.SysUsage().(*syscall.Rusage).Maxrss)

	res, err := govulncheck.UnmarshalGovulncheckResult(output)
	if err != nil {
	return nil, err
	}
	return res.Vulns, nil
	}

	func isNoRequiredModule(err error) bool {
	return strings.Contains(err.Error(), "no required module")
	}

	func isMissingGoSumEntry(err error) bool {
	return strings.Contains(err.Error(), "missing go.sum entry")
	}

	func isMissingGoMod(err error) bool {
	return strings.Contains(err.Error(), "no go.mod file")
	}

	func isVulnDBConnection(err error) bool {
	s := err.Error()
	return strings.Contains(s, "https://vuln.go.dev") &&
	strings.Contains(s, "connection")
	}

	// parseGoMemLimit parses the GOMEMLIMIT environment variable.
	// It returns 0 if the variable isn't set or its value is malformed.
	func parseGoMemLimit(s string) uint64 {
	if len(s) < 2 {
	return 0
	}
	m := uint64(1)
	if s[len(s)-1] == 'i' {
	switch s[len(s)-2] {
	case 'K':
	m = 1024
	case 'M':
	m = 1024 * 1024
	case 'G':
	m = 1024 * 1024 * 1024
	default:
	return 0
	}
	s = s[:len(s)-2]
	}
	v, err := strconv.ParseUint(s, 10, 64)
	if err != nil {
	return 0
	}
	return v * m
	}

	// fileExists checks if file path exists. Returns true
	// if the file exists or it cannot prove that it does
	// not exist. Otherwise, returns false.
	func fileExists(file string) bool {
	if _, err := os.Stat(file); err == nil {
	return true
	} else if errors.Is(err, os.ErrNotExist) {
	return false
	}
	// Conservatively return true if os.Stat fails
	// for some other reason.
	return true
	}