api接口安全策略：签名和加密原理-后端验证签名原理

1. 安全概述

一般的接口是裸露的、不安全的！使用post、get模拟可以轻松对api进行请求，最简单的攻击就可以瞬间完成近万会员的注册！所以在进行api接口通讯的同时我们应该进行数据的验证工作！

2. 加密原理及流程(自定义)

2.1 从服务器端获取一个唯一性的token，我们称之为 accessToken;
2.2 前端对accessToken进行随机性拆分及md5加密,产生签名（保存在本地存储中）;
2.3 前端在与后端进行交互时传递签名;
2.4 后端接收数据是验证签名;

3. 签名准备

3.1 前端(uni-app)-主要理解签名函数

(1)md5.js (对字符串进行md5 加密)

var hexcase = 0;   /* hex output format. 0 - lowercase; 1 - uppercase        */
var b64pad  = "";  /* base-64 pad character. "=" for strict RFC compliance   */

/*
 * These are the functions you'll usually want to call
 * They take string arguments and return either hex or base-64 encoded strings
 * md5 加密 ：该文件用于对字符串进行md5加密
 */
function hex_md5(s)    { return rstr2hex(rstr_md5(str2rstr_utf8(s))); }
function b64_md5(s)    { return rstr2b64(rstr_md5(str2rstr_utf8(s))); }
function any_md5(s, e) { return rstr2any(rstr_md5(str2rstr_utf8(s)), e); }
function hex_hmac_md5(k, d)
  { return rstr2hex(rstr_hmac_md5(str2rstr_utf8(k), str2rstr_utf8(d))); }
function b64_hmac_md5(k, d)
  { return rstr2b64(rstr_hmac_md5(str2rstr_utf8(k), str2rstr_utf8(d))); }
function any_hmac_md5(k, d, e)
  { return rstr2any(rstr_hmac_md5(str2rstr_utf8(k), str2rstr_utf8(d)), e); }

/*
 * Perform a simple self-test to see if the VM is working
 */
function md5_vm_test()
{
  return hex_md5("abc").toLowerCase() == "900150983cd24fb0d6963f7d28e17f72";
}

/*
 * Calculate the MD5 of a raw string
 */
function rstr_md5(s)
{
  return binl2rstr(binl_md5(rstr2binl(s), s.length * 8));
}

/*
 * Calculate the HMAC-MD5, of a key and some data (raw strings)
 */
function rstr_hmac_md5(key, data)
{
  var bkey = rstr2binl(key);
  if(bkey.length > 16) bkey = binl_md5(bkey, key.length * 8);

  var ipad = Array(16), opad = Array(16);
  for(var i = 0; i < 16; i++)
  {
    ipad[i] = bkey[i] ^ 0x36363636;
    opad[i] = bkey[i] ^ 0x5C5C5C5C;
  }

  var hash = binl_md5(ipad.concat(rstr2binl(data)), 512 + data.length * 8);
  return binl2rstr(binl_md5(opad.concat(hash), 512 + 128));
}

/*
 * Convert a raw string to a hex string
 */
function rstr2hex(input)
{
  try { hexcase } catch(e) { hexcase=0; }
  var hex_tab = hexcase ? "0123456789ABCDEF" : "0123456789abcdef";
  var output = "";
  var x;
  for(var i = 0; i < input.length; i++)
  {
    x = input.charCodeAt(i);
    output += hex_tab.charAt((x >>> 4) & 0x0F)
           +  hex_tab.charAt( x        & 0x0F);
  }
  return output;
}

/*
 * Convert a raw string to a base-64 string
 */
function rstr2b64(input)
{
  try { b64pad } catch(e) { b64pad=''; }
  var tab = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  var output = "";
  var len = input.length;
  for(var i = 0; i < len; i += 3)
  {
    var triplet = (input.charCodeAt(i) << 16)
                | (i + 1 < len ? input.charCodeAt(i+1) << 8 : 0)
                | (i + 2 < len ? input.charCodeAt(i+2)      : 0);
    for(var j = 0; j < 4; j++)
    {
      if(i * 8 + j * 6 > input.length * 8) output += b64pad;
      else output += tab.charAt((triplet >>> 6*(3-j)) & 0x3F);
    }
  }
  return output;
}

/*
 * Convert a raw string to an arbitrary string encoding
 */
function rstr2any(input, encoding)
{
  var divisor = encoding.length;
  var i, j, q, x, quotient;

  /* Convert to an array of 16-bit big-endian values, forming the dividend */
  var dividend = Array(Math.ceil(input.length / 2));
  for(i = 0; i < dividend.length; i++)
  {
    dividend[i] = (input.charCodeAt(i * 2) << 8) | input.charCodeAt(i * 2 + 1);
  }

  /*
   * Repeatedly perform a long division. The binary array forms the dividend,
   * the length of the encoding is the divisor. Once computed, the quotient
   * forms the dividend for the next step. All remainders are stored for later
   * use.
   */
  var full_length = Math.ceil(input.length * 8 /
                                    (Math.log(encoding.length) / Math.log(2)));
  var remainders = Array(full_length);
  for(j = 0; j < full_length; j++)
  {
    quotient = Array();
    x = 0;
    for(i = 0; i < dividend.length; i++)
    {
      x = (x << 16) + dividend[i];
      q = Math.floor(x / divisor);
      x -= q * divisor;
      if(quotient.length > 0 || q > 0)
        quotient[quotient.length] = q;
    }
    remainders[j] = x;
    dividend = quotient;
  }

  /* Convert the remainders to the output string */
  var output = "";
  for(i = remainders.length - 1; i >= 0; i--)
    output += encoding.charAt(remainders[i]);

  return output;
}

/*
 * Encode a string as utf-8.
 * For efficiency, this assumes the input is valid utf-16.
 */
function str2rstr_utf8(input)
{
  var output = "";
  var i = -1;
  var x, y;

  while(++i < input.length)
  {
    /* Decode utf-16 surrogate pairs */
    x = input.charCodeAt(i);
    y = i + 1 < input.length ? input.charCodeAt(i + 1) : 0;
    if(0xD800 <= x && x <= 0xDBFF && 0xDC00 <= y && y <= 0xDFFF)
    {
      x = 0x10000 + ((x & 0x03FF) << 10) + (y & 0x03FF);
      i++;
    }

    /* Encode output as utf-8 */
    if(x <= 0x7F)
      output += String.fromCharCode(x);
    else if(x <= 0x7FF)
      output += String.fromCharCode(0xC0 | ((x >>> 6 ) & 0x1F),
                                    0x80 | ( x         & 0x3F));
    else if(x <= 0xFFFF)
      output += String.fromCharCode(0xE0 | ((x >>> 12) & 0x0F),
                                    0x80 | ((x >>> 6 ) & 0x3F),
                                    0x80 | ( x         & 0x3F));
    else if(x <= 0x1FFFFF)
      output += String.fromCharCode(0xF0 | ((x >>> 18) & 0x07),
                                    0x80 | ((x >>> 12) & 0x3F),
                                    0x80 | ((x >>> 6 ) & 0x3F),
                                    0x80 | ( x         & 0x3F));
  }
  return output;
}

/*
 * Encode a string as utf-16
 */
function str2rstr_utf16le(input)
{
  var output = "";
  for(var i = 0; i < input.length; i++)
    output += String.fromCharCode( input.charCodeAt(i)        & 0xFF,
                                  (input.charCodeAt(i) >>> 8) & 0xFF);
  return output;
}

function str2rstr_utf16be(input)
{
  var output = "";
  for(var i = 0; i < input.length; i++)
    output += String.fromCharCode((input.charCodeAt(i) >>> 8) & 0xFF,
                                   input.charCodeAt(i)        & 0xFF);
  return output;
}

/*
 * Convert a raw string to an array of little-endian words
 * Characters >255 have their high-byte silently ignored.
 */
function rstr2binl(input)
{
  var output = Array(input.length >> 2);
  for(var i = 0; i < output.length; i++)
    output[i] = 0;
  for(var i = 0; i < input.length * 8; i += 8)
    output[i>>5] |= (input.charCodeAt(i / 8) & 0xFF) << (i%32);
  return output;
}

/*
 * Convert an array of little-endian words to a string
 */
function binl2rstr(input)
{
  var output = "";
  for(var i = 0; i < input.length * 32; i += 8)
    output += String.fromCharCode((input[i>>5] >>> (i % 32)) & 0xFF);
  return output;
}

/*
 * Calculate the MD5 of an array of little-endian words, and a bit length.
 */
function binl_md5(x, len)
{
  /* append padding */
  x[len >> 5] |= 0x80 << ((len) % 32);
  x[(((len + 64) >>> 9) << 4) + 14] = len;

  var a =  1732584193;
  var b = -271733879;
  var c = -1732584194;
  var d =  271733878;

  for(var i = 0; i < x.length; i += 16)
  {
    var olda = a;
    var oldb = b;
    var oldc = c;
    var oldd = d;

    a = md5_ff(a, b, c, d, x[i+ 0], 7 , -680876936);
    d = md5_ff(d, a, b, c, x[i+ 1], 12, -389564586);
    c = md5_ff(c, d, a, b, x[i+ 2], 17,  606105819);
    b = md5_ff(b, c, d, a, x[i+ 3], 22, -1044525330);
    a = md5_ff(a, b, c, d, x[i+ 4], 7 , -176418897);
    d = md5_ff(d, a, b, c, x[i+ 5], 12,  1200080426);
    c = md5_ff(c, d, a, b, x[i+ 6], 17, -1473231341);
    b = md5_ff(b, c, d, a, x[i+ 7], 22, -45705983);
    a = md5_ff(a, b, c, d, x[i+ 8], 7 ,  1770035416);
    d = md5_ff(d, a, b, c, x[i+ 9], 12, -1958414417);
    c = md5_ff(c, d, a, b, x[i+10], 17, -42063);
    b = md5_ff(b, c, d, a, x[i+11], 22, -1990404162);
    a = md5_ff(a, b, c, d, x[i+12], 7 ,  1804603682);
    d = md5_ff(d, a, b, c, x[i+13], 12, -40341101);
    c = md5_ff(c, d, a, b, x[i+14], 17, -1502002290);
    b = md5_ff(b, c, d, a, x[i+15], 22,  1236535329);

    a = md5_gg(a, b, c, d, x[i+ 1], 5 , -165796510);
    d = md5_gg(d, a, b, c, x[i+ 6], 9 , -1069501632);
    c = md5_gg(c, d, a, b, x[i+11], 14,  643717713);
    b = md5_gg(b, c, d, a, x[i+ 0], 20, -373897302);
    a = md5_gg(a, b, c, d, x[i+ 5], 5 , -701558691);
    d = md5_gg(d, a, b, c, x[i+10], 9 ,  38016083);
    c = md5_gg(c, d, a, b, x[i+15], 14, -660478335);
    b = md5_gg(b, c, d, a, x[i+ 4], 20, -405537848);
    a = md5_gg(a, b, c, d, x[i+ 9], 5 ,  568446438);
    d = md5_gg(d, a, b, c, x[i+14], 9 , -1019803690);
    c = md5_gg(c, d, a, b, x[i+ 3], 14, -187363961);
    b = md5_gg(b, c, d, a, x[i+ 8], 20,  1163531501);
    a = md5_gg(a, b, c, d, x[i+13], 5 , -1444681467);
    d = md5_gg(d, a, b, c, x[i+ 2], 9 , -51403784);
    c = md5_gg(c, d, a, b, x[i+ 7], 14,  1735328473);
    b = md5_gg(b, c, d, a, x[i+12], 20, -1926607734);

    a = md5_hh(a, b, c, d, x[i+ 5], 4 , -378558);
    d = md5_hh(d, a, b, c, x[i+ 8], 11, -2022574463);
    c = md5_hh(c, d, a, b, x[i+11], 16,  1839030562);
    b = md5_hh(b, c, d, a, x[i+14], 23, -35309556);
    a = md5_hh(a, b, c, d, x[i+ 1], 4 , -1530992060);
    d = md5_hh(d, a, b, c, x[i+ 4], 11,  1272893353);
    c = md5_hh(c, d, a, b, x[i+ 7], 16, -155497632);
    b = md5_hh(b, c, d, a, x[i+10], 23, -1094730640);
    a = md5_hh(a, b, c, d, x[i+13], 4 ,  681279174);
    d = md5_hh(d, a, b, c, x[i+ 0], 11, -358537222);
    c = md5_hh(c, d, a, b, x[i+ 3], 16, -722521979);
    b = md5_hh(b, c, d, a, x[i+ 6], 23,  76029189);
    a = md5_hh(a, b, c, d, x[i+ 9], 4 , -640364487);
    d = md5_hh(d, a, b, c, x[i+12], 11, -421815835);
    c = md5_hh(c, d, a, b, x[i+15], 16,  530742520);
    b = md5_hh(b, c, d, a, x[i+ 2], 23, -995338651);

    a = md5_ii(a, b, c, d, x[i+ 0], 6 , -198630844);
    d = md5_ii(d, a, b, c, x[i+ 7], 10,  1126891415);
    c = md5_ii(c, d, a, b, x[i+14], 15, -1416354905);
    b = md5_ii(b, c, d, a, x[i+ 5], 21, -57434055);
    a = md5_ii(a, b, c, d, x[i+12], 6 ,  1700485571);
    d = md5_ii(d, a, b, c, x[i+ 3], 10, -1894986606);
    c = md5_ii(c, d, a, b, x[i+10], 15, -1051523);
    b = md5_ii(b, c, d, a, x[i+ 1], 21, -2054922799);
    a = md5_ii(a, b, c, d, x[i+ 8], 6 ,  1873313359);
    d = md5_ii(d, a, b, c, x[i+15], 10, -30611744);
    c = md5_ii(c, d, a, b, x[i+ 6], 15, -1560198380);
    b = md5_ii(b, c, d, a, x[i+13], 21,  1309151649);
    a = md5_ii(a, b, c, d, x[i+ 4], 6 , -145523070);
    d = md5_ii(d, a, b, c, x[i+11], 10, -1120210379);
    c = md5_ii(c, d, a, b, x[i+ 2], 15,  718787259);
    b = md5_ii(b, c, d, a, x[i+ 9], 21, -343485551);

    a = safe_add(a, olda);
    b = safe_add(b, oldb);
    c = safe_add(c, oldc);
    d = safe_add(d, oldd);
  }
  return Array(a, b, c, d);
}

/*
 * These functions implement the four basic operations the algorithm uses.
 */
function md5_cmn(q, a, b, x, s, t)
{
  return safe_add(bit_rol(safe_add(safe_add(a, q), safe_add(x, t)), s),b);
}
function md5_ff(a, b, c, d, x, s, t)
{
  return md5_cmn((b & c) | ((~b) & d), a, b, x, s, t);
}
function md5_gg(a, b, c, d, x, s, t)
{
  return md5_cmn((b & d) | (c & (~d)), a, b, x, s, t);
}
function md5_hh(a, b, c, d, x, s, t)
{
  return md5_cmn(b ^ c ^ d, a, b, x, s, t);
}
function md5_ii(a, b, c, d, x, s, t)
{
  return md5_cmn(c ^ (b | (~d)), a, b, x, s, t);
}

/*
 * Add integers, wrapping at 2^32. This uses 16-bit operations internally
 * to work around bugs in some JS interpreters.
 */
function safe_add(x, y)
{
  var lsw = (x & 0xFFFF) + (y & 0xFFFF);
  var msw = (x >> 16) + (y >> 16) + (lsw >> 16);
  return (msw << 16) | (lsw & 0xFFFF);
}

/*
 * Bitwise rotate a 32-bit number to the left.
 */
function bit_rol(num, cnt)
{
  return (num << cnt) | (num >>> (32 - cnt));
}

module.exports  = {
    hex_md5 : hex_md5
}

(2)sign.js (签名函数)

var md5 = require('./md5.js');
/**
 * 签名函数：与服务器进行交互与md5加密
 */
module.exports = {
    sign : function(apiServer){
        // 环境判断非uni环境不支持（get、post模拟工具模拟不出来uni变量，实现了接口安全）
        if(!uni){return '...';}
        console.log('开始签名');
        // 连接服务器获取一个临时的accessToken
        uni.request({
            url: apiServer+'getAccessToken',
            method: 'GET',
            success: res => {
                console.log(res);
                if(res.data.status != 'ok'){return ;}
                var data = res.data.data;
                // 对 accessToken 进行md5加密（token和当前时间戳组合后加密）
                var accessToken = md5.hex_md5(data.token + data.time);
                // 签名 = md5(accessToekn + time) + '-' + 'accessToekn';
                var sign = accessToken + '-' + data.token;
                //console.log(sign);
                // 记录在本地
                uni.setStorage({
                    key:"sign",
                    data:sign
                });
                console.log('签名完成');
            },
            fail:function(e){
                console.log(JSON.stringify(e));
            }
        });
    }
}

3.2 数据库-创建数据表存放临时token

DROP TABLE IF EXISTS `yuedu_access_tokens`;
CREATE TABLE `yuedu_access_tokens` (
  `token` varchar(30) NOT NULL,
  `time` int(11) DEFAULT NULL,
  PRIMARY KEY (`token`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8mb4;

3.3 后端(php)

(1)表中插入生成的token

 uniqid(),
                'time' => time()
        );
        $db->add($token);//记录写入到数据库
        exit(jsonCode('ok'),$token);//返回token
        
    }
        
}
?>

(2)签名验证-后端验证签名原理

//签名验证
function checkSign(){
    if(empty($_POST['sign'])){exit(jsonCode('error', 'sign error'));}
    $sign = explode('-', $_POST['sign']);
    if(count($sign) != 2){exit(jsonCode('error', 'sign error'));}
    $db = \hsTool\db::getInstance('access_tokens');
    $token = $db->where('token = ?', array($sign[1]))->fetch();
    if(empty($token)){exit(jsonCode('error', 'sign error'));}
    $signMd5 = md5($token['token'].$token['time']);
    if($signMd5 != $sign[0]){exit(jsonCode('error', 'sign error'));}
    // 验证成功则删除
    $db->where('token = ?', array($sign[1]))->delete();
}

4. 使用说明

在数据提交页面提交之前进行预签名，提交数据时携带此签名！

//options为登录验证时若需进行登录时传的参数
    onLoad:function(options){
        sign.sign(this.apiServer);//预签名：获取签名并保存在本地
        
        //console.log(options)
        _self = this;
        pageOptions = options
        
        //条件编译：判断对应平台
        // #ifdef MP-WEIXIN
        //微信端登录
        uni.login({
            success:function(res){
                console.log(res)
                uni.request({
                    url: _self.apiServer + 'member&m=codeToSession&code=' + res.code,
                    method: 'GET',
                    //data: {},
                    success: res => {
                        console.log(res)
                        session_key = res.data.session_key;
                        openid = res.data.openid;
                    }
                });
            }
        })
        // #endif
        
        // #ifdef APP-PLUS
        //app端(微信第三方)登录:手册位置 https://uniapp.dcloud.io/api/plugins/login?id=getuserinfo
        uni.login({
            provider: 'weixin',//默认登录提供商是微信，可省略（也可以开发微博、qq等的同步登录）
            success:function(loginRes){
                //console.log(JSON.stringify(loginRes))//对象转json
                //console.log(JSON.stringify(loginRes.authResult));//authResult对象存放的是和对应平台相关的敏感信息
                
                uni.getUserInfo({
                    success:function(infoRes){//userInfo存放基本的用户信息,
                        //console.log(JSON.stringify(infoRes));
                        //console.log('用户昵称为:' + infoRes.userInfo.nickName);
                        var sign = uni.getStorageSync('sign');
                        
                        // 与服务器交互将数据提交到服务端数据库
                        uni.request({
                            url: _self.apiServer+'member&m=login',
                            method: 'POST',
                            header: {'content-type' : "application/x-www-form-urlencoded"},
                            data: {
                                openid : infoRes.userInfo.openId,
                                name   : infoRes.userInfo.nickName,
                                face   : infoRes.userInfo.avatarUrl,
                                sign   : sign
                            },
                            success: res => {
                                console.log(JSON.stringify(res));
                                res = res.data;
                                if(res.status == "ok"){
                                    uni.showToast({title:"登录成功后存储用户信息并跳转"});
                                    uni.setStorageSync('SUID',res.data.u_id + '');
                                    uni.setStorageSync('SRAND',res.data.u_random + '');
                                    uni.setStorageSync('SNAME',res.data.u_name + '');
                                    uni.setStorageSync('SFACE',res.data.u_face + '');
                                    if(options.backtype == 1){
                                        uni.redirectTo({url:options.backpage});
                                    }else{
                                        uni.switchTab({url:options.backpage});
                                    }
                                
                                }else{
                                    uni.showToast({title:'登录失败:' + res.data});
                                }
                            },
                            fail: () => {},
                            complete: () => {}
                        });

                    },
                    fail:function(){
                        uni.showToast({title:"微信登录授权失败",icon:"none"});
                    }
                })
            },
            fail:function(){
                uni.showToast({title:"微信登录授权失败",icon:"none"});
            }
        })
        // #endif
        
    }

5. 更合理的签名保存

(1)此处使用数据库保存了accessToken，会降低数据库的性能：每一个token都会连接数据库去读取和生成；如果只是预签名没有提交，但也会放在数据表中产生垃圾数据。
(2)更好的方式是使用redis 或 memcache来保存token和time，优点是不仅变量会自动失效而且查询效率高：redis 或 memcache的所有变量都有有效期，可以设置变量有效期并能隔段时间自动失效，符合accessToken的生命周期；redis 或 memcache的保存是基于内存的，不需要连接数据库，查询效率高。