feat(优化兼容): 添加ofdgo_sign.go文件

ofdgo_sign.go

@@ -0,0 +1,167 @@
+// Copyright 2025 肖其顿 (XIAO QI DUN)
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package ofdgo
+
+import (
+	"encoding/asn1"
+	"encoding/xml"
+	"path"
+	"strings"
+)
+
+const (
+	// SignTypeSeal 签章类型: seal
+	SignTypeSeal = "seal"
+	// SignTypeSign 签章类型: sign
+	SignTypeSign = "sign"
+)
+
+// OFDSignatures 签名列表列表
+type OFDSignatures struct {
+	XMLName   xml.Name       `xml:"Signatures"`
+	MaxSignId string         `xml:"MaxSignId"`
+	List      []OFDSignature `xml:"Signature"`
+}
+
+// OFDSignature 签名列表引用
+type OFDSignature struct {
+	ID      string `xml:"ID,attr"`
+	BaseLoc string `xml:"BaseLoc,attr"`
+}
+
+// SignatureFile 签名文件内容描述
+type SignatureFile struct {
+	XMLName     xml.Name `xml:"Signature"`
+	SignedValue string   `xml:"SignedValue"`
+	SignedInfo  struct {
+		StampAnnot []struct {
+			ID       string `xml:"ID,attr"`
+			PageRef  string `xml:"PageRef,attr"`
+			Boundary string `xml:"Boundary,attr"`
+		} `xml:"StampAnnot"`
+	} `xml:"SignedInfo"`
+}
+
+// parseSignatures 解析签名文件
+// 入参: doc 文档结构
+// 返回: error 错误信息
+func (r *Reader) parseSignatures(doc *Document) error {
+	if doc.Signatures == "" {
+		return nil
+	}
+	f, err := r.openFile(doc.Signatures)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	var signatures OFDSignatures
+	if err := xml.NewDecoder(f).Decode(&signatures); err != nil {
+		return err
+	}
+	for _, sigRef := range signatures.List {
+		sigPath := path.Join(path.Dir(doc.Signatures), sigRef.BaseLoc)
+		sf, err := r.openFile(sigPath)
+		if err != nil {
+			continue
+		}
+		var sigFile SignatureFile
+		if err := xml.NewDecoder(sf).Decode(&sigFile); err != nil {
+			sf.Close()
+			continue
+		}
+		sf.Close()
+		signedValuePath := path.Join(path.Dir(sigPath), sigFile.SignedValue)
+		svData, err := r.ResData(signedValuePath)
+		if err != nil {
+			continue
+		}
+		sealType, sealData := extractSeal(svData)
+		for _, annot := range sigFile.SignedInfo.StampAnnot {
+			pageID := annot.PageRef
+			bbox, _ := ParseBox(annot.Boundary)
+			r.addStamp(pageID, bbox, sealType, sealData)
+		}
+	}
+	return nil
+}
+
+// extractSeal 尝试提取印章数据
+// 入参: data 签名值数据
+// 返回: string 印章类型, []byte 印章数据
+func extractSeal(data []byte) (string, []byte) {
+	var raw asn1.RawValue
+	_, err := asn1.Unmarshal(data, &raw)
+	if err != nil {
+		return "", nil
+	}
+	var foundType string
+	var foundData []byte
+	var search func(node asn1.RawValue) bool
+	search = func(node asn1.RawValue) bool {
+		if node.IsCompound {
+			var elements []asn1.RawValue
+			rest, err := asn1.Unmarshal(node.Bytes, &elements)
+			if err == nil && len(rest) == 0 {
+				if len(elements) == 4 {
+					e0, e1, e2, e3 := elements[0], elements[1], elements[2], elements[3]
+					if e1.Tag == 4 && e2.Tag == 2 && e3.Tag == 2 {
+						foundData = e1.Bytes
+						var s string
+						if _, err := asn1.Unmarshal(e0.FullBytes, &s); err == nil {
+							foundType = s
+						} else {
+							foundType = string(e0.Bytes)
+						}
+						foundType = strings.ToLower(strings.TrimSpace(strings.ReplaceAll(foundType, "\x00", "")))
+						if foundType == "es" {
+							foundType = "png"
+						}
+						return true
+					}
+				}
+				for _, child := range elements {
+					if search(child) {
+						return true
+					}
+				}
+			}
+		}
+		return false
+	}
+	if search(raw) {
+		return foundType, foundData
+	}
+	return "", nil
+}
+
+// Stamp 印章信息结构
+type Stamp struct {
+	Box  Box
+	Type string
+	Data []byte
+}
+
+// addStamp 添加印章到页面
+// 入参: pageID 页面ID, box 印章区域, sType 印章类型, data 印章数据
+func (r *Reader) addStamp(pageID string, box Box, sType string, data []byte) {
+	if r.Stamps == nil {
+		r.Stamps = make(map[string][]Stamp)
+	}
+	r.Stamps[pageID] = append(r.Stamps[pageID], Stamp{
+		Box:  box,
+		Type: sType,
+		Data: data,
+	})
+}