/**
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* Alipay.com Inc. Copyright (c) 2004-2019 All Rights Reserved.
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*/
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package com.alipay.easysdk.kernel.util;
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import com.alipay.easysdk.kernel.AlipayConstants;
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import java.util.LinkedList;
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/**
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* 待验签原文提取器
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* <p>
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* 注：此处不可使用JSON反序列化工具进行提取，会破坏原有格式，对于签名而言差个空格都会验签不通过
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*
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* @author zhongyu
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* @version $Id: SignContentExtractor.java, v 0.1 2019年12月19日 9:07 PM zhongyu Exp $
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*/
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public class SignContentExtractor {
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/**
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* 左大括号
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*/
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public static final char LEFT_BRACE = '{';
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/**
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* 右大括号
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*/
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public static final char RIGHT_BRACE = '}';
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/**
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* 双引号
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*/
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public static final char DOUBLE_QUOTES = '"';
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/**
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* 获取待验签的原文
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*
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* @param body 网关的整体响应字符串
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* @param method 本次调用的OpenAPI接口名称
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* @return 待验签的原文
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*/
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public static String getSignSourceData(String body, String method) {
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// 加签源串起点
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String rootNode = method.replace('.', '_') + AlipayConstants.RESPONSE_SUFFIX;
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String errorRootNode = AlipayConstants.ERROR_RESPONSE;
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int indexOfRootNode = body.indexOf(rootNode);
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int indexOfErrorRoot = body.indexOf(errorRootNode);
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if (indexOfRootNode > 0) {
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return parseSignSourceData(body, rootNode, indexOfRootNode);
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} else if (indexOfErrorRoot > 0) {
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return parseSignSourceData(body, errorRootNode, indexOfErrorRoot);
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} else {
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return null;
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}
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}
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private static String parseSignSourceData(String body, String rootNode, int indexOfRootNode) {
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//第一个字母 + 长度 + 冒号 + 引号
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int signDataStartIndex = indexOfRootNode + rootNode.length() + 2;
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int indexOfSign = body.indexOf("\"" + AlipayConstants.SIGN_FIELD + "\"");
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if (indexOfSign < 0) {
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return null;
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}
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SignSourceData signSourceData = extractSignContent(body, signDataStartIndex);
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//如果提取的待验签原始内容后还有rootNode
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if (body.lastIndexOf(rootNode) > signSourceData.getEndIndex()) {
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throw new RuntimeException("检测到响应报文中有重复的" + rootNode + "，验签失败。");
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}
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return signSourceData.getSourceData();
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}
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private static SignSourceData extractSignContent(String str, int begin) {
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if (str == null) {
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return null;
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}
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int beginIndex = extractBeginPosition(str, begin);
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if (beginIndex >= str.length()) {
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return null;
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}
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int endIndex = extractEndPosition(str, beginIndex);
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return new SignSourceData(str.substring(beginIndex, endIndex), beginIndex, endIndex);
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}
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private static int extractBeginPosition(String responseString, int begin) {
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int beginPosition = begin;
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//找到第一个左大括号（对应响应的是JSON对象的情况：普通调用OpenAPI响应明文）
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//或者双引号（对应响应的是JSON字符串的情况：加密调用OpenAPI响应Base64串），作为待验签内容的起点
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while (beginPosition < responseString.length()
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&& responseString.charAt(beginPosition) != LEFT_BRACE
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&& responseString.charAt(beginPosition) != DOUBLE_QUOTES) {
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++beginPosition;
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}
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return beginPosition;
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}
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private static int extractEndPosition(String responseString, int beginPosition) {
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//提取明文验签内容终点
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if (responseString.charAt(beginPosition) == LEFT_BRACE) {
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return extractJsonObjectEndPosition(responseString, beginPosition);
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}
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//提取密文验签内容终点
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else {
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return extractJsonBase64ValueEndPosition(responseString, beginPosition);
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}
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}
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private static int extractJsonBase64ValueEndPosition(String responseString, int beginPosition) {
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for (int index = beginPosition; index < responseString.length(); ++index) {
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//找到第2个双引号作为终点，由于中间全部是Base64编码的密文，所以不会有干扰的特殊字符
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if (responseString.charAt(index) == DOUBLE_QUOTES && index != beginPosition) {
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return index + 1;
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}
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}
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//如果没有找到第2个双引号，说明验签内容片段提取失败，直接尝试选取剩余整个响应字符串进行验签
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return responseString.length();
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}
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private static int extractJsonObjectEndPosition(String responseString, int beginPosition) {
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//记录当前尚未发现配对闭合的大括号
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LinkedList<Character> braces = new LinkedList<Character>();
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//记录当前字符是否在双引号中
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boolean inQuotes = false;
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//记录当前字符前面连续的转义字符个数
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int consecutiveEscapeCount = 0;
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//从待验签字符的起点开始遍历后续字符串，找出待验签字符串的终止点，终点即是与起点{配对的}
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for (int index = beginPosition; index < responseString.length(); ++index) {
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//提取当前字符
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char currentChar = responseString.charAt(index);
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//如果当前字符是"且前面有偶数个转义标记（0也是偶数）
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if (currentChar == DOUBLE_QUOTES && consecutiveEscapeCount % 2 == 0) {
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//是否在引号中的状态取反
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inQuotes = !inQuotes;
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}
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//如果当前字符是{且不在引号中
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else if (currentChar == LEFT_BRACE && !inQuotes) {
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//将该{加入未闭合括号中
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braces.push(LEFT_BRACE);
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}
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//如果当前字符是}且不在引号中
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else if (currentChar == RIGHT_BRACE && !inQuotes) {
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//弹出一个未闭合括号
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braces.pop();
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//如果弹出后，未闭合括号为空，说明已经找到终点
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if (braces.isEmpty()) {
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return index + 1;
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}
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}
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//如果当前字符是转义字符
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if (currentChar == '\\') {
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//连续转义字符个数+1
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++consecutiveEscapeCount;
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} else {
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//连续转义字符个数置0
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consecutiveEscapeCount = 0;
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}
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}
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//如果没有找到配对的闭合括号，说明验签内容片段提取失败，直接尝试选取剩余整个响应字符串进行验签
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return responseString.length();
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}
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private static class SignSourceData {
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/**
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* 待验签原始内容
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*/
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private final String sourceData;
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/**
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* 待验签原始内容在响应字符串中的起始位置
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*/
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private final int beginIndex;
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/**
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* 待验签原始内容在响应字符串中的结束位置
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*/
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private final int endIndex;
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SignSourceData(String sourceData, int beginIndex, int endIndex) {
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this.sourceData = sourceData;
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this.beginIndex = beginIndex;
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this.endIndex = endIndex;
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}
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String getSourceData() {
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return sourceData;
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}
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public int getBeginIndex() {
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return beginIndex;
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}
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int getEndIndex() {
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return endIndex;
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}
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}
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}
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