[release-branch.go1.20] cmd/cover: error out if a requested source file contains a newline

cmd/cover uses '//line' directives to map instrumented source files
back to the original source file and line numbers.
Line directives have no way to escape newline characters, so cmd/cover
must not be used with source file paths that contain such characters.

Updates #60516.
Updates #60167.

Change-Id: I6dc039392d59fc3a5a6121ef6ca97b0ab0da5288
Reviewed-on: https://go-review.googlesource.com/c/go/+/501577
Auto-Submit: Bryan Mills <bcmills@google.com>
Run-TryBot: Bryan Mills <bcmills@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
(cherry picked from commit 3d78c735fc7d213e23383b9744297bd5251dc0e3)
Reviewed-on: https://go-review.googlesource.com/c/go/+/501818
Auto-Submit: Dmitri Shuralyov <dmitshur@google.com>

2 files changed, 41 insertions, 0 deletions

diff --git a/src/cmd/cover/cover.go b/src/cmd/cover/cover.go
index 74bb500cb9..5fd8b95272 100644
--- a/src/cmd/cover/cover.go
+++ b/src/cmd/cover/cover.go
@@ -568,6 +568,11 @@ func annotate(names []string) {
 	}
 	// TODO: process files in parallel here if it matters.
 	for k, name := range names {
+		if strings.ContainsAny(name, "\r\n") {
+			// annotateFile uses '//line' directives, which don't permit newlines.
+			log.Fatalf("cover: input path contains newline character: %q", name)
+		}
+
 		last := false
 		if k == len(names)-1 {
 			last = true
@@ -645,6 +650,11 @@ func (p *Package) annotateFile(name string, fd io.Writer, last bool) {
 	}
 	newContent := file.edit.Bytes()
 
+	if strings.ContainsAny(name, "\r\n") {
+		// This should have been checked by the caller already, but we double check
+		// here just to be sure we haven't missed a caller somewhere.
+		panic(fmt.Sprintf("annotateFile: name contains unexpected newline character: %q", name))
+	}
 	fmt.Fprintf(fd, "//line %s:1:1\n", name)
 	fd.Write(newContent)
 
diff --git a/src/cmd/cover/cover_test.go b/src/cmd/cover/cover_test.go
index af266b5e83..6ed4ae4675 100644
--- a/src/cmd/cover/cover_test.go
+++ b/src/cmd/cover/cover_test.go
@@ -574,3 +574,34 @@ func runExpectingError(c *exec.Cmd, t *testing.T) string {
 	}
 	return string(out)
 }
+
+func TestSrcPathWithNewline(t *testing.T) {
+	testenv.MustHaveExec(t)
+	t.Parallel()
+
+	// srcPath is intentionally not clean so that the path passed to testcover
+	// will not normalize the trailing / to a \ on Windows.
+	srcPath := t.TempDir() + string(filepath.Separator) + "\npackage main\nfunc main() { panic(string([]rune{'u', 'h', '-', 'o', 'h'}))\n/*/main.go"
+	mainSrc := ` package main
+
+func main() {
+	/* nothing here */
+	println("ok")
+}
+`
+	if err := os.MkdirAll(filepath.Dir(srcPath), 0777); err != nil {
+		t.Skipf("creating directory with bogus path: %v", err)
+	}
+	if err := os.WriteFile(srcPath, []byte(mainSrc), 0666); err != nil {
+		t.Skipf("writing file with bogus directory: %v", err)
+	}
+
+	cmd := testenv.Command(t, testcover(t), "-mode=atomic", srcPath)
+	cmd.Stderr = new(bytes.Buffer)
+	out, err := cmd.Output()
+	t.Logf("%v:\n%s", cmd, out)
+	t.Logf("stderr:\n%s", cmd.Stderr)
+	if err == nil {
+		t.Errorf("unexpected success; want failure due to newline in file path")
+	}
+}