add build constraints to limit syscalls to linux

Author: 3ventic

internal/login/login.go

@@ -14,8 +14,6 @@ import (
 	"net/url"
 	"os/exec"
 	"runtime"
-	"strings"
-	"syscall"
 	"time"
 
 	"github.com/spf13/viper"
@@ -231,32 +229,12 @@ func generateState() (string, error) {
 	return base64.URLEncoding.EncodeToString(b), nil
 }
 
-// check for Windows Subsystem for Linux
-func isWsl(sc util.Syscall) bool {
-	// the common factor between WSL distros is the Microsoft-specific kernel version, so we check for that
-	// SUSE, WSLv1: 4.4.0-19041-Microsoft
-	// Ubuntu, WSLv2: 4.19.128-microsoft-standard
-	const wslIdentifier = "microsoft"
-	var uname syscall.Utsname
-	if err := sc.Uname(&uname); err == nil {
-		var kernel []byte
-		for _, b := range uname.Release {
-			if b == 0 {
-				break
-			}
-			kernel = append(kernel, byte(b))
-		}
-		return strings.Contains(strings.ToLower(string(kernel)), wslIdentifier)
-	}
-	return false
-}
-
 func openBrowser(url string) error {
 	const rundllParameters = "url.dll,FileProtocolHandler"
 	var err error
 	switch runtime.GOOS {
 	case "linux":
-		if isWsl(util.DefaultSyscall) {
+		if util.IsWsl() {
 			err = exec.Command("rundll32.exe", rundllParameters, url).Start()
 		} else {
 			err = exec.Command("xdg-open", url).Start()

internal/login/login_test.go

@@ -4,16 +4,13 @@ package login
 
 import (
 	"encoding/json"
-	"errors"
 	"fmt"
 	"net/http"
 	"net/http/httptest"
-	"syscall"
 	"testing"
 	"time"
 
 	"github.com/spf13/viper"
-	"github.com/stretchr/testify/assert"
 	"github.com/twitchdev/twitch-cli/internal/util"
 )
 
@@ -160,40 +157,3 @@ func TestUserAuthServer(t *testing.T) {
 	a.Equal(state, ur.State, "State mismatch")
 	a.Equal(code, ur.Code, "Code mismatch")
 }
-
-func TestIsWsl(t *testing.T) {
-	a := assert.New(t)
-
-	var (
-		// syscall.Utsname.Release value on various systems
-
-		// Ubuntu 20.04 on WSL2 on Windows 10 x64 20H2
-		ubuntu20Wsl2 = [65]int8{52, 46, 49, 57, 46, 49, 50, 56, 45, 109, 105, 99, 114, 111, 115, 111, 102, 116, 45, 115, 116, 97, 110, 100, 97, 114, 100, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
-
-		// Arch Linux on baremetal on 2021-04-02
-		archReal = [65]int8{53, 46, 49, 49, 46, 49, 49, 45, 97, 114, 99, 104, 49, 45, 49, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
-	)
-
-	result := isWsl(util.Syscall{
-		Uname: func(buf *syscall.Utsname) (err error) {
-			buf.Release = ubuntu20Wsl2
-			return nil
-		},
-	})
-	a.True(result)
-
-	result = isWsl(util.Syscall{
-		Uname: func(buf *syscall.Utsname) (err error) {
-			buf.Release = archReal
-			return nil
-		},
-	})
-	a.False(result)
-
-	result = isWsl(util.Syscall{
-		Uname: func(buf *syscall.Utsname) (err error) {
-			return errors.New("mocked error")
-		},
-	})
-	a.False(result)
-}

internal/util/syscall.go

@@ -1,3 +1,7 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+// +build linux
+
 package util
 
 import "syscall"

internal/util/wsl.go

@@ -0,0 +1,34 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+// +build linux
+
+package util
+
+import (
+	"strings"
+	"syscall"
+)
+
+func IsWsl() bool {
+	return isWsl(DefaultSyscall)
+}
+
+// check for Windows Subsystem for Linux
+func isWsl(sc Syscall) bool {
+	// the common factor between WSL distros is the Microsoft-specific kernel version, so we check for that
+	// SUSE, WSLv1: 4.4.0-19041-Microsoft
+	// Ubuntu, WSLv2: 4.19.128-microsoft-standard
+	const wslIdentifier = "microsoft"
+	var uname syscall.Utsname
+	if err := sc.Uname(&uname); err == nil {
+		var kernel []byte
+		for _, b := range uname.Release {
+			if b == 0 {
+				break
+			}
+			kernel = append(kernel, byte(b))
+		}
+		return strings.Contains(strings.ToLower(string(kernel)), wslIdentifier)
+	}
+	return false
+}

internal/util/wsl_default.go

@@ -0,0 +1,10 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+// +build !linux
+
+package util
+
+// non-linux platforms cannot be WSL
+func IsWsl() bool {
+	return false
+}

internal/util/wsl_test.go

@@ -0,0 +1,50 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+// +build linux
+
+package util
+
+import (
+	"errors"
+	"syscall"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestIsWsl(t *testing.T) {
+	a := assert.New(t)
+
+	var (
+		// syscall.Utsname.Release value on various systems
+
+		// Ubuntu 20.04 on WSL2 on Windows 10 x64 20H2
+		ubuntu20Wsl2 = [65]int8{52, 46, 49, 57, 46, 49, 50, 56, 45, 109, 105, 99, 114, 111, 115, 111, 102, 116, 45, 115, 116, 97, 110, 100, 97, 114, 100, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
+
+		// Arch Linux on baremetal on 2021-04-02
+		archReal = [65]int8{53, 46, 49, 49, 46, 49, 49, 45, 97, 114, 99, 104, 49, 45, 49, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
+	)
+
+	result := isWsl(Syscall{
+		Uname: func(buf *syscall.Utsname) (err error) {
+			buf.Release = ubuntu20Wsl2
+			return nil
+		},
+	})
+	a.True(result)
+
+	result = isWsl(Syscall{
+		Uname: func(buf *syscall.Utsname) (err error) {
+			buf.Release = archReal
+			return nil
+		},
+	})
+	a.False(result)
+
+	result = isWsl(Syscall{
+		Uname: func(buf *syscall.Utsname) (err error) {
+			return errors.New("mocked error")
+		},
+	})
+	a.False(result)
+}