cmd/go/internal/work: allow @ character in some -Wl, linker flags on darwin

The GNU linker interprets @file as "read command-line options from file".
Thus, we forbid values starting with @ on linker flags. However, this
causes a problem when targeting Darwin. @executable_path, @loader_path, and
@rpath are special values used in Mach-O to change the library search path
and can be used in conjunction with the -install_name and -rpath linker
flags. Since the GNU linker does not support Mach-O, targeting Darwin
implies not using the GNU linker. Therefore, we allow @ in the linker flags
if and only if cfg.Goos == "darwin".

Fixes #40559

Change-Id: I0896758f0835e444ea0d501ea3fd8423cff97a27
GitHub-Last-Rev: 2b81dcd12e
GitHub-Pull-Request: golang/go#70939
Reviewed-on: https://go-review.googlesource.com/c/go/+/638075
Auto-Submit: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

src/cmd/go/internal/work/security.go

@@ -227,6 +227,21 @@ var validLinkerFlags = []*lazyregexp.Regexp{
 	re(`\./.*\.(a|o|obj|dll|dylib|so|tbd)`),
 }
 
+var validLinkerFlagsOnDarwin = []*lazyregexp.Regexp{
+	// The GNU linker interprets `@file` as "read command-line options from
+	// file". Thus, we forbid values starting with `@` on linker flags.
+	// However, this causes a problem when targeting Darwin.
+	// `@executable_path`, `@loader_path`, and `@rpath` are special values
+	// used in Mach-O to change the library search path and can be used in
+	// conjunction with the `-install_name` and `-rpath` linker flags.
+	// Since the GNU linker does not support Mach-O, targeting Darwin
+	// implies not using the GNU linker. Therefore, we allow @ in the linker
+	// flags if and only if cfg.Goos == "darwin" || cfg.Goos == "ios".
+	re(`-Wl,-dylib_install_name,@rpath(/[^,]*)?`),
+	re(`-Wl,-install_name,@rpath(/[^,]*)?`),
+	re(`-Wl,-rpath,@(executable_path|loader_path)(/[^,]*)?`),
+}
+
 var validLinkerFlagsWithNextArg = []string{
 	"-arch",
 	"-F",
@@ -249,8 +264,13 @@ func checkCompilerFlags(name, source string, list []string) error {
 }
 
 func checkLinkerFlags(name, source string, list []string) error {
+	validLinkerFlagsForPlatform := validLinkerFlags
+	if cfg.Goos == "darwin" || cfg.Goos == "ios" {
+		validLinkerFlagsForPlatform = append(validLinkerFlags, validLinkerFlagsOnDarwin...)
+	}
+
 	checkOverrides := true
-	return checkFlags(name, source, list, invalidLinkerFlags, validLinkerFlags, validLinkerFlagsWithNextArg, checkOverrides)
+	return checkFlags(name, source, list, invalidLinkerFlags, validLinkerFlagsForPlatform, validLinkerFlagsWithNextArg, checkOverrides)
 }
 
 // checkCompilerFlagsForInternalLink returns an error if 'list'

src/cmd/go/internal/work/security_test.go

@@ -8,6 +8,8 @@ import (
 	"os"
 	"strings"
 	"testing"
+
+	"cmd/go/internal/cfg"
 )
 
 var goodCompilerFlags = [][]string{
@@ -245,6 +247,8 @@ var badLinkerFlags = [][]string{
 	{"-Wl,--hash-style=foo"},
 	{"-x", "--c"},
 	{"-x", "@obj"},
+	{"-Wl,-dylib_install_name,@foo"},
+	{"-Wl,-install_name,@foo"},
 	{"-Wl,-rpath,@foo"},
 	{"-Wl,-R,foo,bar"},
 	{"-Wl,-R,@foo"},
@@ -261,6 +265,21 @@ var badLinkerFlags = [][]string{
 	{"./-Wl,--push-state,-R.c"},
 }
 
+var goodLinkerFlagsOnDarwin = [][]string{
+	{"-Wl,-dylib_install_name,@rpath"},
+	{"-Wl,-dylib_install_name,@rpath/"},
+	{"-Wl,-dylib_install_name,@rpath/foo"},
+	{"-Wl,-install_name,@rpath"},
+	{"-Wl,-install_name,@rpath/"},
+	{"-Wl,-install_name,@rpath/foo"},
+	{"-Wl,-rpath,@executable_path"},
+	{"-Wl,-rpath,@executable_path/"},
+	{"-Wl,-rpath,@executable_path/foo"},
+	{"-Wl,-rpath,@loader_path"},
+	{"-Wl,-rpath,@loader_path/"},
+	{"-Wl,-rpath,@loader_path/foo"},
+}
+
 func TestCheckLinkerFlags(t *testing.T) {
 	for _, f := range goodLinkerFlags {
 		if err := checkLinkerFlags("test", "test", f); err != nil {
@@ -272,6 +291,31 @@ func TestCheckLinkerFlags(t *testing.T) {
 			t.Errorf("missing error for %q", f)
 		}
 	}
+
+	goos := cfg.Goos
+
+	cfg.Goos = "darwin"
+	for _, f := range goodLinkerFlagsOnDarwin {
+		if err := checkLinkerFlags("test", "test", f); err != nil {
+			t.Errorf("unexpected error for %q: %v", f, err)
+		}
+	}
+
+	cfg.Goos = "ios"
+	for _, f := range goodLinkerFlagsOnDarwin {
+		if err := checkLinkerFlags("test", "test", f); err != nil {
+			t.Errorf("unexpected error for %q: %v", f, err)
+		}
+	}
+
+	cfg.Goos = "linux"
+	for _, f := range goodLinkerFlagsOnDarwin {
+		if err := checkLinkerFlags("test", "test", f); err == nil {
+			t.Errorf("missing error for %q", f)
+		}
+	}
+
+	cfg.Goos = goos
 }
 
 func TestCheckFlagAllowDisallow(t *testing.T) {