Use base32 for 2FA scratch token (go-gitea#18384)

* Use base32 for 2FA scratch token
* rename Secure* to Crypto*, add comments

Author: wxiaoguang

models/auth/twofactor.go

@@ -8,6 +8,7 @@ import (
 	"crypto/md5"
 	"crypto/sha256"
 	"crypto/subtle"
+	"encoding/base32"
 	"encoding/base64"
 	"fmt"
 
@@ -58,11 +59,14 @@ func init() {
 
 // GenerateScratchToken recreates the scratch token the user is using.
 func (t *TwoFactor) GenerateScratchToken() (string, error) {
-	token, err := util.RandomString(8)
+	tokenBytes, err := util.CryptoRandomBytes(6)
 	if err != nil {
 		return "", err
 	}
-	t.ScratchSalt, _ = util.RandomString(10)
+	// these chars are specially chosen, avoid ambiguous chars like `0`, `O`, `1`, `I`.
+	const base32Chars = "ABCDEFGHJKLMNPQRSTUVWXYZ23456789"
+	token := base32.NewEncoding(base32Chars).WithPadding(base32.NoPadding).EncodeToString(tokenBytes)
+	t.ScratchSalt, _ = util.CryptoRandomString(10)
 	t.ScratchHash = HashToken(token, t.ScratchSalt)
 	return token, nil
 }

models/migrations/v71.go

@@ -53,7 +53,7 @@ func addScratchHash(x *xorm.Engine) error {
 
 		for _, tfa := range tfas {
 			// generate salt
-			salt, err := util.RandomString(10)
+			salt, err := util.CryptoRandomString(10)
 			if err != nil {
 				return err
 			}

models/migrations/v85.go

@@ -65,7 +65,7 @@ func hashAppToken(x *xorm.Engine) error {
 
 		for _, token := range tokens {
 			// generate salt
-			salt, err := util.RandomString(10)
+			salt, err := util.CryptoRandomString(10)
 			if err != nil {
 				return err
 			}

models/token.go

@@ -62,7 +62,7 @@ func init() {
 
 // NewAccessToken creates new access token.
 func NewAccessToken(t *AccessToken) error {
-	salt, err := util.RandomString(10)
+	salt, err := util.CryptoRandomString(10)
 	if err != nil {
 		return err
 	}

models/user/user.go

@@ -533,7 +533,7 @@ const SaltByteLength = 16
 
 // GetUserSalt returns a random user salt token.
 func GetUserSalt() (string, error) {
-	rBytes, err := util.RandomBytes(SaltByteLength)
+	rBytes, err := util.CryptoRandomBytes(SaltByteLength)
 	if err != nil {
 		return "", err
 	}

modules/generate/generate.go

@@ -60,7 +60,7 @@ func NewJwtSecretBase64() (string, error) {
 
 // NewSecretKey generate a new value intended to be used by SECRET_KEY.
 func NewSecretKey() (string, error) {
-	secretKey, err := util.RandomString(64)
+	secretKey, err := util.CryptoRandomString(64)
 	if err != nil {
 		return "", err
 	}

modules/secret/secret.go

@@ -24,7 +24,7 @@ func New() (string, error) {
 
 // NewWithLength creates a new secret for a given length
 func NewWithLength(length int64) (string, error) {
-	return util.RandomString(length)
+	return util.CryptoRandomString(length)
 }
 
 // AesEncrypt encrypts text and given key with AES.

modules/util/util.go

@@ -137,36 +137,36 @@ func MergeInto(dict map[string]interface{}, values ...interface{}) (map[string]i
 	return dict, nil
 }
 
-// RandomInt returns a random integer between 0 and limit, inclusive
-func RandomInt(limit int64) (int64, error) {
+// CryptoRandomInt returns a crypto random integer between 0 and limit, inclusive
+func CryptoRandomInt(limit int64) (int64, error) {
 	rInt, err := rand.Int(rand.Reader, big.NewInt(limit))
 	if err != nil {
 		return 0, err
 	}
 	return rInt.Int64(), nil
 }
 
-const letters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
+const alphanumericalChars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
 
-// RandomString generates a random alphanumerical string
-func RandomString(length int64) (string, error) {
-	bytes := make([]byte, length)
-	limit := int64(len(letters))
-	for i := range bytes {
-		num, err := RandomInt(limit)
+// CryptoRandomString generates a crypto random alphanumerical string, each byte is generated by [0,61] range
+func CryptoRandomString(length int64) (string, error) {
+	buf := make([]byte, length)
+	limit := int64(len(alphanumericalChars))
+	for i := range buf {
+		num, err := CryptoRandomInt(limit)
 		if err != nil {
 			return "", err
 		}
-		bytes[i] = letters[num]
+		buf[i] = alphanumericalChars[num]
 	}
-	return string(bytes), nil
+	return string(buf), nil
 }
 
-// RandomBytes generates `length` bytes
-// This differs from RandomString, as RandomString is limits each byte to have
-// a maximum value of 63 instead of 255(max byte size)
-func RandomBytes(length int64) ([]byte, error) {
-	bytes := make([]byte, length)
-	_, err := rand.Read(bytes)
-	return bytes, err
+// CryptoRandomBytes generates `length` crypto bytes
+// This differs from CryptoRandomString, as each byte in CryptoRandomString is generated by [0,61] range
+// This function generates totally random bytes, each byte is generated by [0,255] range
+func CryptoRandomBytes(length int64) ([]byte, error) {
+	buf := make([]byte, length)
+	_, err := rand.Read(buf)
+	return buf, err
 }

modules/util/util_test.go

@@ -120,34 +120,34 @@ func Test_NormalizeEOL(t *testing.T) {
 }
 
 func Test_RandomInt(t *testing.T) {
-	int, err := RandomInt(255)
+	int, err := CryptoRandomInt(255)
 	assert.True(t, int >= 0)
 	assert.True(t, int <= 255)
 	assert.NoError(t, err)
 }
 
 func Test_RandomString(t *testing.T) {
-	str1, err := RandomString(32)
+	str1, err := CryptoRandomString(32)
 	assert.NoError(t, err)
 	matches, err := regexp.MatchString(`^[a-zA-Z0-9]{32}$`, str1)
 	assert.NoError(t, err)
 	assert.True(t, matches)
 
-	str2, err := RandomString(32)
+	str2, err := CryptoRandomString(32)
 	assert.NoError(t, err)
 	matches, err = regexp.MatchString(`^[a-zA-Z0-9]{32}$`, str1)
 	assert.NoError(t, err)
 	assert.True(t, matches)
 
 	assert.NotEqual(t, str1, str2)
 
-	str3, err := RandomString(256)
+	str3, err := CryptoRandomString(256)
 	assert.NoError(t, err)
 	matches, err = regexp.MatchString(`^[a-zA-Z0-9]{256}$`, str3)
 	assert.NoError(t, err)
 	assert.True(t, matches)
 
-	str4, err := RandomString(256)
+	str4, err := CryptoRandomString(256)
 	assert.NoError(t, err)
 	matches, err = regexp.MatchString(`^[a-zA-Z0-9]{256}$`, str4)
 	assert.NoError(t, err)
@@ -157,18 +157,18 @@ func Test_RandomString(t *testing.T) {
 }
 
 func Test_RandomBytes(t *testing.T) {
-	bytes1, err := RandomBytes(32)
+	bytes1, err := CryptoRandomBytes(32)
 	assert.NoError(t, err)
 
-	bytes2, err := RandomBytes(32)
+	bytes2, err := CryptoRandomBytes(32)
 	assert.NoError(t, err)
 
 	assert.NotEqual(t, bytes1, bytes2)
 
-	bytes3, err := RandomBytes(256)
+	bytes3, err := CryptoRandomBytes(256)
 	assert.NoError(t, err)
 
-	bytes4, err := RandomBytes(256)
+	bytes4, err := CryptoRandomBytes(256)
 	assert.NoError(t, err)
 
 	assert.NotEqual(t, bytes3, bytes4)

routers/web/auth/openid.go

@@ -416,7 +416,7 @@ func RegisterOpenIDPost(ctx *context.Context) {
 	if length < 256 {
 		length = 256
 	}
-	password, err := util.RandomString(int64(length))
+	password, err := util.CryptoRandomString(int64(length))
 	if err != nil {
 		ctx.RenderWithErr(err.Error(), tplSignUpOID, form)
 		return