在JS逆向系列课的第15课《真假猴王 Base64 竟有如此威力》中，我们了解到了Base64原来还能通过修改码表的方式，使其变成“加密”的效果， 也学习了如何通过同样的方式，在Python中将其轻松干掉。

那么现在，请运用你在第15课中学到的知识，尝试做一下这道题吧~

请问：

第7个帖子（以1为起始）的HTML中id为content的部分中一共有多少个img标签？

找到数据返回地址

![debugger](../img/125.png)

打断点测试

![debugger](../img/126.png)

发现 Base64 是魔改过的

    data = JSON.parse(Base64.run(data))
    
提取js代码，测试解密

    var _O0O0oooa = ['\x51\x4d\x66\x7a\x69', '\x49\x71\x4c\x45\x46', '\x6c\x65\x6e\x67\x74\x68', '\x31\x30\x32\x34', '\x52\x4a\x63\x4b\x52'];
    (function (a, b) {
        var c = function (f) {
            while (--f) {
                a['push'](a['shift']());
            }
        };
        c(++b);
    }(_O0O0oooa, 0xae));
    var _O0O0ooob = function (a, b) {
        a = a - 0x0;
        var c = _O0O0oooa[a];
        return c;
    };
    
    function _O0O0oooc() {
        var b = {};
        b[_O0O0ooob('\x30\x78\x31')] = function (d, e) {
            return d + e;
        };
        b[_O0O0ooob('\x30\x78\x30')] = _O0O0ooob('\x30\x78\x34');
        b['\x49\x71\x4c\x45\x46'] = function (d, e) {
            return d + e;
        };
        var c = b;
        b = ![] | !![] & ![];
        b = c[_O0O0ooob('\x30\x78\x31')](c[_O0O0ooob('\x30\x78\x30')], b);
        return c[_O0O0ooob('\x30\x78\x32')](b, b[_O0O0ooob('\x30\x78\x33')]);
    }
    
    var Base64 = {
    
        // private property
        _keyStr: "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="
    
        // public method for encoding
        , encode: function (input) {
            var output = "";
            var chr1, chr2, chr3, enc1, enc2, enc3, enc4;
            var i = 0;
    
            input = Base64._utf8_encode(input);
    
            while (i < input.length) {
                chr1 = input.charCodeAt(i++);
                chr2 = input.charCodeAt(i++);
                chr3 = input.charCodeAt(i++);
    
                enc1 = chr1 >> 2;
                enc2 = ((chr1 & 3) << 4) | (chr2 >> 4);
                enc3 = ((chr2 & 15) << 2) | (chr3 >> 6);
                enc4 = chr3 & 63;
    
                if (isNaN(chr2)) {
                    enc3 = enc4 = 64;
                } else if (isNaN(chr3)) {
                    enc4 = 64;
                }
    
                output = output +
                    this._keyStr.charAt(enc1) + this._keyStr.charAt(enc2) +
                    this._keyStr.charAt(enc3) + this._keyStr.charAt(enc4);
            } // Whend
    
            return output;
        } // End Function encode
    
    
        // public method for decoding
        , decode: function (input) {
            var output = "";
            var chr1, chr2, chr3;
            var enc1, enc2, enc3, enc4;
            var i = 0;
    
            input = input.replace(/[^A-Za-z0-9\+\/\=]/g, "");
            while (i < input.length) {
                enc1 = this._keyStr.indexOf(input.charAt(i++));
                enc2 = this._keyStr.indexOf(input.charAt(i++));
                enc3 = this._keyStr.indexOf(input.charAt(i++));
                enc4 = this._keyStr.indexOf(input.charAt(i++));
    
                chr1 = (enc1 << 2) | (enc2 >> 4);
                chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);
                chr3 = ((enc3 & 3) << 6) | enc4;
    
                output = output + String.fromCharCode(chr1);
    
                if (enc3 != 64) {
                    output = output + String.fromCharCode(chr2);
                }
    
                if (enc4 != 64) {
                    output = output + String.fromCharCode(chr3);
                }
    
            } // Whend
    
            output = Base64._utf8_decode(output);
    
            return output;
        } // End Function decode
    
    
        // private method for UTF-8 encoding
        , _utf8_encode: function (string) {
            var utftext = "";
            string = string.replace(/\r\n/g, "\n");
    
            for (var n = 0; n < string.length; n++) {
                var c = string.charCodeAt(n);
    
                if (c < 128) {
                    utftext += String.fromCharCode(c);
                } else if ((c > 127) && (c < 2048)) {
                    utftext += String.fromCharCode((c >> 6) | 192);
                    utftext += String.fromCharCode((c & 63) | 128);
                } else {
                    utftext += String.fromCharCode((c >> 12) | 224);
                    utftext += String.fromCharCode(((c >> 6) & 63) | 128);
                    utftext += String.fromCharCode((c & 63) | 128);
                }
    
            } // Next n
    
            return utftext;
        } // End Function _utf8_encode
    
        // private method for UTF-8 decoding
        , _utf8_decode: function (utftext) {
            var string = "";
            var i = 0;
            var c, c1, c2, c3;
            c = c1 = c2 = 0;
    
            while (i < utftext.length) {
                c = utftext.charCodeAt(i);
    
                if (c < 128) {
                    string += String.fromCharCode(c);
                    i++;
                } else if ((c > 191) && (c < 224)) {
                    c2 = utftext.charCodeAt(i + 1);
                    string += String.fromCharCode(((c & 31) << 6) | (c2 & 63));
                    i += 2;
                } else {
                    c2 = utftext.charCodeAt(i + 1);
                    c3 = utftext.charCodeAt(i + 2);
                    string += String.fromCharCode(((c & 15) << 12) | ((c2 & 63) << 6) | (c3 & 63));
                    i += 3;
                }
    
            } // Whend
    
            return string;
        }, // End Function _utf8_decode
        run: function (all_str) {
            Base64._keyStr = all_str.substring(0, 64);
            let charset = all_str.substring(64, all_str.length);
            return Base64.decode(charset).replace("", "").replace("￀", "")
        }
    
    };
    
    a = Base64.run('[encoded data, 14900 characters]');
    console.log(JSON.parse(a));
