Refactor legacy `unknwon/com` package, improve golangci lint (#19284)

The main purpose is to refactor the legacy `unknwon/com` package.
1. Remove most imports of `unknwon/com`, only `util/legacy.go` imports the legacy `unknwon/com`
2. Use golangci's depguard to process denied packages
3. Fix some incorrect values in golangci.yml, eg, the version should be quoted string `"1.18"`
4. Use correctly escaped content for `go-import` and `go-source` meta tags
5. Refactor `com.Expand` to our stable (and the same fast) `vars.Expand`, our `vars.Expand` can still return partially rendered content even if the template is not good (eg: key mistach).

5 files changed, 148 insertions, 22 deletions

diff --git a/modules/util/copy.go b/modules/util/copy.go
deleted file mode 100644
index 46765849dc..0000000000
--- a/modules/util/copy.go
+++ /dev/null
@@ -1,20 +0,0 @@
-// Copyright 2020 The Gitea Authors. All rights reserved.
-// Use of this source code is governed by a MIT-style
-// license that can be found in the LICENSE file.
-
-package util
-
-import (
-	"github.com/unknwon/com"
-)
-
-// CopyFile copies file from source to target path.
-func CopyFile(src, dest string) error {
-	return com.Copy(src, dest)
-}
-
-// CopyDir copy files recursively from source to target directory.
-// It returns error when error occurs in underlying functions.
-func CopyDir(srcPath, destPath string) error {
-	return com.CopyDir(srcPath, destPath)
-}
diff --git a/modules/util/io.go b/modules/util/io.go
index b467c0ac8a..0c677c359f 100644
--- a/modules/util/io.go
+++ b/modules/util/io.go
@@ -9,7 +9,7 @@ import (
 )
 
 // ReadAtMost reads at most len(buf) bytes from r into buf.
-// It returns the number of bytes copied. n is only less then len(buf) if r provides fewer bytes.
+// It returns the number of bytes copied. n is only less than len(buf) if r provides fewer bytes.
 // If EOF occurs while reading, err will be nil.
 func ReadAtMost(r io.Reader, buf []byte) (n int, err error) {
 	n, err = io.ReadFull(r, buf)
diff --git a/modules/util/legacy.go b/modules/util/legacy.go
new file mode 100644
index 0000000000..c7da541534
--- /dev/null
+++ b/modules/util/legacy.go
@@ -0,0 +1,84 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package util
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/rand"
+	"errors"
+
+	"github.com/unknwon/com" //nolint:depguard
+)
+
+// CopyFile copies file from source to target path.
+func CopyFile(src, dest string) error {
+	return com.Copy(src, dest)
+}
+
+// CopyDir copy files recursively from source to target directory.
+// It returns error when error occurs in underlying functions.
+func CopyDir(srcPath, destPath string) error {
+	return com.CopyDir(srcPath, destPath)
+}
+
+// ToStr converts any interface to string. should be replaced.
+func ToStr(value interface{}, args ...int) string {
+	return com.ToStr(value, args...)
+}
+
+// ToSnakeCase converts a string to snake_case. should be replaced.
+func ToSnakeCase(str string) string {
+	return com.ToSnakeCase(str)
+}
+
+// AESGCMEncrypt (from legacy package): encrypts plaintext with the given key using AES in GCM mode. should be replaced.
+func AESGCMEncrypt(key, plaintext []byte) ([]byte, error) {
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return nil, err
+	}
+
+	nonce := make([]byte, gcm.NonceSize())
+	if _, err := rand.Read(nonce); err != nil {
+		return nil, err
+	}
+
+	ciphertext := gcm.Seal(nil, nonce, plaintext, nil)
+	return append(nonce, ciphertext...), nil
+}
+
+// AESGCMDecrypt (from legacy package): decrypts ciphertext with the given key using AES in GCM mode. should be replaced.
+func AESGCMDecrypt(key, ciphertext []byte) ([]byte, error) {
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return nil, err
+	}
+
+	size := gcm.NonceSize()
+	if len(ciphertext)-size <= 0 {
+		return nil, errors.New("ciphertext is empty")
+	}
+
+	nonce := ciphertext[:size]
+	ciphertext = ciphertext[size:]
+
+	plainText, err := gcm.Open(nil, nonce, ciphertext, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	return plainText, nil
+}
diff --git a/modules/util/legacy_test.go b/modules/util/legacy_test.go
new file mode 100644
index 0000000000..cfda93d3ad
--- /dev/null
+++ b/modules/util/legacy_test.go
@@ -0,0 +1,37 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package util
+
+import (
+	"crypto/aes"
+	"crypto/rand"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/unknwon/com" //nolint:depguard
+)
+
+func TestAESGCM(t *testing.T) {
+	t.Parallel()
+
+	key := make([]byte, aes.BlockSize)
+	_, err := rand.Read(key)
+	assert.NoError(t, err)
+
+	plaintext := []byte("this will be encrypted")
+
+	ciphertext, err := AESGCMEncrypt(key, plaintext)
+	assert.NoError(t, err)
+
+	decrypted, err := AESGCMDecrypt(key, ciphertext)
+	assert.NoError(t, err)
+
+	assert.Equal(t, plaintext, decrypted)
+
+	// at the moment, we make sure the result is the same as the legacy package, this assertion can be removed in next round refactoring
+	legacy, err := com.AESGCMDecrypt(key, ciphertext)
+	assert.NoError(t, err)
+	assert.Equal(t, legacy, plaintext)
+}
diff --git a/modules/util/path.go b/modules/util/path.go
index f4acf92ba9..ed7cc62699 100644
--- a/modules/util/path.go
+++ b/modules/util/path.go
@@ -154,6 +154,10 @@ func StatDir(rootPath string, includeDir ...bool) ([]string, error) {
 	return statDir(rootPath, "", isIncludeDir, false, false)
 }
 
+func isOSWindows() bool {
+	return runtime.GOOS == "windows"
+}
+
 // FileURLToPath extracts the path information from a file://... url.
 func FileURLToPath(u *url.URL) (string, error) {
 	if u.Scheme != "file" {
@@ -162,7 +166,7 @@ func FileURLToPath(u *url.URL) (string, error) {
 
 	path := u.Path
 
-	if runtime.GOOS != "windows" {
+	if !isOSWindows() {
 		return path, nil
 	}
 
@@ -173,3 +177,24 @@ func FileURLToPath(u *url.URL) (string, error) {
 	}
 	return path, nil
 }
+
+// HomeDir returns path of '~'(in Linux) on Windows,
+// it returns error when the variable does not exist.
+func HomeDir() (home string, err error) {
+	// TODO: some users run Gitea with mismatched uid  and "HOME=xxx" (they set HOME=xxx by environment manually)
+	// so at the moment we can not use `user.Current().HomeDir`
+	if isOSWindows() {
+		home = os.Getenv("USERPROFILE")
+		if home == "" {
+			home = os.Getenv("HOMEDRIVE") + os.Getenv("HOMEPATH")
+		}
+	} else {
+		home = os.Getenv("HOME")
+	}
+
+	if home == "" {
+		return "", errors.New("cannot get home directory")
+	}
+
+	return home, nil
+}