fix: incorrect unsafe usage in upstream lib

Updates #1070

coolq/cqcode.go

@@ -21,7 +21,6 @@ import (
 	"github.com/Mrs4s/MiraiGo/message"
 	"github.com/Mrs4s/MiraiGo/utils"
 	"github.com/gabriel-vasile/mimetype"
-	"github.com/segmentio/asm/base64"
 	log "github.com/sirupsen/logrus"
 	"github.com/tidwall/gjson"
 
@@ -1118,7 +1117,7 @@ func (bot *CQBot) makeImageOrVideoElem(d map[string]string, video, group bool) (
 		return &LocalImageElement{File: fu.Path}, nil
 	}
 	if strings.HasPrefix(f, "base64") && !video {
-		b, err := base64.StdEncoding.DecodeString(strings.TrimPrefix(f, "base64://"))
+		b, err := global.Base64DecodeString(strings.TrimPrefix(f, "base64://"))
 		if err != nil {
 			return nil, err
 		}

global/fs.go

@@ -14,7 +14,6 @@ import (
 	"strings"
 
 	"github.com/Mrs4s/MiraiGo/utils"
-	"github.com/segmentio/asm/base64"
 	log "github.com/sirupsen/logrus"
 )
 
@@ -98,7 +97,7 @@ func FindFile(file, cache, p string) (data []byte, err error) {
 			return nil, err
 		}
 	case strings.HasPrefix(file, "base64"):
-		data, err = base64.StdEncoding.DecodeString(strings.TrimPrefix(file, "base64://"))
+		data, err = Base64DecodeString(strings.TrimPrefix(file, "base64://"))
 		if err != nil {
 			return nil, err
 		}

global/param.go

@@ -8,6 +8,8 @@ import (
 	"strings"
 	"sync"
 
+	"github.com/Mrs4s/MiraiGo/utils"
+	"github.com/segmentio/asm/base64"
 	log "github.com/sirupsen/logrus"
 	"github.com/tidwall/gjson"
 )
@@ -152,3 +154,13 @@ func SplitURL(s string) []string {
 	result = append(result, s[last:])
 	return result
 }
+
+// Base64DecodeString decode base64 with avx2
+// see https://github.com/segmentio/asm/issues/50
+// avoid incorrect unsafe usage in origin library
+func Base64DecodeString(s string) ([]byte, error) {
+	e := base64.StdEncoding
+	dst := make([]byte, e.DecodedLen(len(s)))
+	n, err := e.Decode(dst, utils.S2B(s))
+	return dst[:n], err
+}