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// Copyright 2020 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 errorstest
import (
"bytes"
"io/ioutil"
"os"
"os/exec"
"path/filepath"
"strings"
"testing"
"unicode"
)
// A manually modified object file could pass unexpected characters
// into the files generated by cgo.
const magicInput = "abcdefghijklmnopqrstuvwxyz0123"
const magicReplace = "\n//go:cgo_ldflag \"-badflag\"\n//"
const cSymbol = "BadSymbol" + magicInput + "Name"
const cDefSource = "int " + cSymbol + " = 1;"
const cRefSource = "extern int " + cSymbol + "; int F() { return " + cSymbol + "; }"
// goSource is the source code for the trivial Go file we use.
// We will replace TMPDIR with the temporary directory name.
const goSource = `
package main
// #cgo LDFLAGS: TMPDIR/cbad.o TMPDIR/cbad.so
// extern int F();
import "C"
func main() {
println(C.F())
}
`
func TestBadSymbol(t *testing.T) {
dir := t.TempDir()
mkdir := func(base string) string {
ret := filepath.Join(dir, base)
if err := os.Mkdir(ret, 0755); err != nil {
t.Fatal(err)
}
return ret
}
cdir := mkdir("c")
godir := mkdir("go")
makeFile := func(mdir, base, source string) string {
ret := filepath.Join(mdir, base)
if err := ioutil.WriteFile(ret, []byte(source), 0644); err != nil {
t.Fatal(err)
}
return ret
}
cDefFile := makeFile(cdir, "cdef.c", cDefSource)
cRefFile := makeFile(cdir, "cref.c", cRefSource)
ccCmd := cCompilerCmd(t)
cCompile := func(arg, base, src string) string {
out := filepath.Join(cdir, base)
run := append(ccCmd, arg, "-o", out, src)
output, err := exec.Command(run[0], run[1:]...).CombinedOutput()
if err != nil {
t.Log(run)
t.Logf("%s", output)
t.Fatal(err)
}
if err := os.Remove(src); err != nil {
t.Fatal(err)
}
return out
}
// Build a shared library that defines a symbol whose name
// contains magicInput.
cShared := cCompile("-shared", "c.so", cDefFile)
// Build an object file that refers to the symbol whose name
// contains magicInput.
cObj := cCompile("-c", "c.o", cRefFile)
// Rewrite the shared library and the object file, replacing
// magicInput with magicReplace. This will have the effect of
// introducing a symbol whose name looks like a cgo command.
// The cgo tool will use that name when it generates the
// _cgo_import.go file, thus smuggling a magic //go:cgo_ldflag
// pragma into a Go file. We used to not check the pragmas in
// _cgo_import.go.
rewrite := func(from, to string) {
obj, err := ioutil.ReadFile(from)
if err != nil {
t.Fatal(err)
}
if bytes.Count(obj, []byte(magicInput)) == 0 {
t.Fatalf("%s: did not find magic string", from)
}
if len(magicInput) != len(magicReplace) {
t.Fatalf("internal test error: different magic lengths: %d != %d", len(magicInput), len(magicReplace))
}
obj = bytes.ReplaceAll(obj, []byte(magicInput), []byte(magicReplace))
if err := ioutil.WriteFile(to, obj, 0644); err != nil {
t.Fatal(err)
}
}
cBadShared := filepath.Join(godir, "cbad.so")
rewrite(cShared, cBadShared)
cBadObj := filepath.Join(godir, "cbad.o")
rewrite(cObj, cBadObj)
goSourceBadObject := strings.ReplaceAll(goSource, "TMPDIR", godir)
makeFile(godir, "go.go", goSourceBadObject)
makeFile(godir, "go.mod", "module badsym")
// Try to build our little package.
cmd := exec.Command("go", "build", "-ldflags=-v")
cmd.Dir = godir
output, err := cmd.CombinedOutput()
// The build should fail, but we want it to fail because we
// detected the error, not because we passed a bad flag to the
// C linker.
if err == nil {
t.Errorf("go build succeeded unexpectedly")
}
t.Logf("%s", output)
for _, line := range bytes.Split(output, []byte("\n")) {
if bytes.Contains(line, []byte("dynamic symbol")) && bytes.Contains(line, []byte("contains unsupported character")) {
// This is the error from cgo.
continue
}
// We passed -ldflags=-v to see the external linker invocation,
// which should not include -badflag.
if bytes.Contains(line, []byte("-badflag")) {
t.Error("output should not mention -badflag")
}
// Also check for compiler errors, just in case.
// GCC says "unrecognized command line option".
// clang says "unknown argument".
if bytes.Contains(line, []byte("unrecognized")) || bytes.Contains(output, []byte("unknown")) {
t.Error("problem should have been caught before invoking C linker")
}
}
}
func cCompilerCmd(t *testing.T) []string {
cc := []string{goEnv(t, "CC")}
out := goEnv(t, "GOGCCFLAGS")
quote := '\000'
start := 0
lastSpace := true
backslash := false
s := string(out)
for i, c := range s {
if quote == '\000' && unicode.IsSpace(c) {
if !lastSpace {
cc = append(cc, s[start:i])
lastSpace = true
}
} else {
if lastSpace {
start = i
lastSpace = false
}
if quote == '\000' && !backslash && (c == '"' || c == '\'') {
quote = c
backslash = false
} else if !backslash && quote == c {
quote = '\000'
} else if (quote == '\000' || quote == '"') && !backslash && c == '\\' {
backslash = true
} else {
backslash = false
}
}
}
if !lastSpace {
cc = append(cc, s[start:])
}
return cc
}
func goEnv(t *testing.T, key string) string {
out, err := exec.Command("go", "env", key).CombinedOutput()
if err != nil {
t.Logf("go env %s\n", key)
t.Logf("%s", out)
t.Fatal(err)
}
return strings.TrimSpace(string(out))
}
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