[release-branch.go1.15-security] cmd/go: pass resolved CC, GCCGO to cgo

This makes sure the go command and cgo agree about
exactly which compiler is being used.

This issue was reported by RyotaK.

Fixes CVE-2021-3115.

Change-Id: If171c5c8b2523efb5ea2d957e5ad1380a038149c
Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/949416
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Jay Conrod <jayconrod@google.com>
(cherry picked from commit 4cf399ca38587a6e4a3e85b494cd9a9b4cc53378)
Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/955293
Reviewed-by: Katie Hockman <katiehockman@google.com>

diff --git a/src/cmd/go/internal/work/action.go b/src/cmd/go/internal/work/action.go
index 6b5f9e48079e1f1987db1f3e66fb0855fe705218..03ca301bdd8bd655fa0cf52b78cc09f310316f4a 100644 (file)
--- a/src/cmd/go/internal/work/action.go
+++ b/src/cmd/go/internal/work/action.go
@@ -56,6 +56,9 @@ type Builder struct {
        id           sync.Mutex
        toolIDCache  map[string]string // tool name -> tool ID
        buildIDCache map[string]string // file name -> build ID
+
+       cgoEnvOnce  sync.Once
+       cgoEnvCache []string
 }
 
 // NOTE: Much of Action would not need to be exported if not for test.

diff --git a/src/cmd/go/internal/work/exec.go b/src/cmd/go/internal/work/exec.go
index dc0c4fc3444a3abbba82d62860b149e09e873a57..3c39734590191ae45ab1c8627b035cd81373b9bb 100644 (file)
--- a/src/cmd/go/internal/work/exec.go
+++ b/src/cmd/go/internal/work/exec.go
@@ -1080,10 +1080,8 @@ func (b *Builder) vet(a *Action) error {
                return err
        }
 
-       env := b.cCompilerEnv()
-       if cfg.BuildToolchainName == "gccgo" {
-               env = append(env, "GCCGO="+BuildToolchain.compiler())
-       }
+       // TODO(rsc): Why do we pass $GCCGO to go vet?
+       env := b.cgoEnv()
 
        p := a.Package
        tool := VetTool
@@ -2014,6 +2012,24 @@ func (b *Builder) cCompilerEnv() []string {
        return []string{"TERM=dumb"}
 }
 
+// cgoEnv returns environment variables to set when running cgo.
+// Some of these pass through to cgo running the C compiler,
+// so it includes cCompilerEnv.
+func (b *Builder) cgoEnv() []string {
+       b.cgoEnvOnce.Do(func() {
+               cc, err := exec.LookPath(b.ccExe()[0])
+               if err != nil || filepath.Base(cc) == cc { // reject relative path
+                       cc = "/missing-cc"
+               }
+               gccgo := GccgoBin
+               if filepath.Base(gccgo) == gccgo { // reject relative path
+                       gccgo = "/missing-gccgo"
+               }
+               b.cgoEnvCache = append(b.cCompilerEnv(), "CC="+cc, "GCCGO="+gccgo)
+       })
+       return b.cgoEnvCache
+}
+
 // mkdir makes the named directory.
 func (b *Builder) Mkdir(dir string) error {
        // Make Mkdir(a.Objdir) a no-op instead of an error when a.Objdir == "".
@@ -2603,13 +2619,13 @@ func (b *Builder) cgo(a *Action, cgoExe, objdir string, pcCFLAGS, pcLDFLAGS, cgo
        // along to the host linker. At this point in the code, cgoLDFLAGS
        // consists of the original $CGO_LDFLAGS (unchecked) and all the
        // flags put together from source code (checked).
-       cgoenv := b.cCompilerEnv()
+       cgoenv := b.cgoEnv()
        if len(cgoLDFLAGS) > 0 {
                flags := make([]string, len(cgoLDFLAGS))
                for i, f := range cgoLDFLAGS {
                        flags[i] = strconv.Quote(f)
                }
-               cgoenv = []string{"CGO_LDFLAGS=" + strings.Join(flags, " ")}
+               cgoenv = append(cgoenv, "CGO_LDFLAGS="+strings.Join(flags, " "))
        }
 
        if cfg.BuildToolchainName == "gccgo" {
@@ -2824,7 +2840,7 @@ func (b *Builder) dynimport(a *Action, p *load.Package, objdir, importGo, cgoExe
        if p.Standard && p.ImportPath == "runtime/cgo" {
                cgoflags = []string{"-dynlinker"} // record path to dynamic linker
        }
-       return b.run(a, p.Dir, p.ImportPath, b.cCompilerEnv(), cfg.BuildToolexec, cgoExe, "-dynpackage", p.Name, "-dynimport", dynobj, "-dynout", importGo, cgoflags)
+       return b.run(a, p.Dir, p.ImportPath, b.cgoEnv(), cfg.BuildToolexec, cgoExe, "-dynpackage", p.Name, "-dynimport", dynobj, "-dynout", importGo, cgoflags)
 }
 
 // Run SWIG on all SWIG input files.