使用query詞抓取百度圖片數據的時候，為了簡化抓取，使用firebug跟蹤到百度圖片請求返回了一個json格式數據，例如http://image.baidu.com/i?tn=resultjson_com&ie=gbk&word=%B7%B6%B1%F9%B1%F9&cg=girl&pn=0&rn=60（該url已簡化）。我們只需抓取這個json數據即可，但是這個json格式中的objectUrl和fromUrl卻是加密了的數據，如ippr_z2C$qAzdH3FAzdH3Fjgp_z&e3Bvg6_z&e3BvgAzdH3FstfpAzdH3Fda8candnAzdH3FWada8candnn98c9lndadl9_z&e3B3r2。后又使用firebug發現，鼠標在點擊連接時并沒有向百度解密的請求，故判斷解密程序在javascript中。

本來打算使用SpiderMonkey執行js來解密，但今天在網上偶然看到一段js解密url的代碼，來自百度知道http://zhidao.baidu.com/link?url=APKpO_ktmLa4QE0ZYlOqKyNdLul4rkDbV-LXBeDv40sHe0yDXS-LGc4A3ArNL2RoSY4xD2Z8M_5vdmjm2nAOILhYWXE1ErtGMiPbi-paK4e，測試了下是對的，到這里這個問題總算搞定了。

解密方法很簡單，秘鑰是一個字符的對應關系，有2種映射：（1）多個字符映射為一個字符，'_z2C$q'=>':','_z&e3B'=>'.','AzdH3F'=>'/'，（2）單個字符映射為單字符。根據這個關系可將密文解密為明文，實現并不困難。

C語言的實現：

#include <stdio.h> #include <string.h>// return length; int Decode(const char *src, const char *table, char *dest) {char *d = dest;const char *p = src;while (*p != 0) {if (*p == '_') {if (strncmp(p, "_z2C$q", 6) == 0) {*dest++ = ':';p += 6;} else if (strncmp(p, "_z&e3B", 6) == 0) {*dest++ = '.';p += 6;} else {*dest++ = *p++;}} else if (*p == 'A') {if (strncmp(p, "AzdH3F", 6) == 0) {*dest++ = '/';p += 6;} else {*dest++ = *p++;}} else if (table[*p] == 0) {*dest++ = *p++;} else {*dest++ = table[*p++];}}*dest = 0;return dest - d; }int main(int argc, char **argv) {static char table[128] = {0};table['w'] = 'a';table['k'] = 'b';table['v'] = 'c';table['1'] = 'd';table['j'] = 'e';table['u'] = 'f';table['2'] = 'g';table['i'] = 'h';table['t'] = 'i';table['3'] = 'j';table['h'] = 'k';table['s'] = 'l';table['4'] = 'm';table['g'] = 'n';table['5'] = 'o';table['r'] = 'p';table['q'] = 'q';table['6'] = 'r';table['f'] = 's';table['p'] = 't';table['7'] = 'u';table['e'] = 'v';table['o'] = 'w';table['8'] = '1';table['d'] = '2';table['n'] = '3';table['9'] = '4';table['c'] = '5';table['m'] = '6';table['0'] = '7';table['b'] = '8';table['l'] = '9';table['a'] = '0';char *url = "ippr_z2C$qAzdH3FAzdH3Ft428_z&e3Bd0_z&e3BvgAzdH3Ft4w2jfAzdH3Fda8a8aAzdH3FddAzdH3F8db00d0dnd_9amln8aa_z&e3B3r2";char dest[1024];Decode(url, table, dest);printf("%s\n", dest);return 0; } 自己寫的，不能保證效率。

輸出：http://img1.27.cn/images/201010/22/1287727232_40693100.jpg

JavaScript的實現：

<script type="text/javascript">var f = { w: "a", k: "b", v: "c", 1: "d", j: "e", u: "f", 2: "g", i: "h", t: "i", 3: "j", h: "k", s: "l", 4: "m", g: "n", 5: "o", r: "p", q: "q", 6: "r", f: "s", p: "t", 7: "u", e: "v", o: "w", 8: "1", d: "2", n: "3", 9: "4", c: "5", m: "6", 0: "7", b: "8", l: "9", a: "0", _z2C$q: ":", "_z&e3B": ".", AzdH3F: "/" };var url = "ippr_z2C$qAzdH3FAzdH3Fjgp_z&e3Bvg6_z&e3BvgAzdH3FstfpAzdH3Fda8candnAzdH3FWada8candnn98c9lndadl9_z&e3B3r2";var h = /(_z2C\$q|_z&e3B|AzdH3F)/g;var e = url.replace(h, function(t, e) { return f[e] });var s = /([a-w\d])/g;e = e.replace(s, function(t, e) { return f[e] });document.write(e); </script>
輸出：http://ent.cnr.cn/list/20150323/W020150323341549320294.jpg

PHP的實現：

<?PHP $f = array('w'=>'a','k'=>'b','v'=>'c','1'=>'d','j'=>'e','u'=>'f','2'=>'g','i'=>'h','t'=>'i','3'=>'j','h'=>'k','s'=>'l','4'=>'m','g'=>'n','5'=>'o','r'=>'p','q'=>'q','6'=>'r','f'=>'s','p'=>'t','7'=>'u','e'=>'v','o'=>'w','8'=>'1','d'=>'2','n'=>'3','9'=>'4','c'=>'5','m'=>'6','0'=>'7','b'=>'8','l'=>'9','a'=>'0','_z2C$q'=>':','_z&e3B'=>'.','AzdH3F'=>'/');$url = 'ippr_z2C$qAzdH3FAzdH3Ft4f_z&e3Bw6ptg2nmc_z&e3Bv54AzdH3Fg51jAzdH3F8da90bAzdH3F'; // 這里需要用單引號$url = preg_replace_callback('/_z2C\$q|_z&e3B|AzdH3F/', function($matches){ global $f; return $f[$matches[0]]; }, $url); $url = preg_replace_callback('/[a-w\d]/', function($matches){ global $f; return $f[$matches[0]]; }, $url); echo $url; ?>

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