作者：Jerry
鏈接：https://zhuanlan.zhihu.com/p/25957793
來(lái)源：知乎
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前言
在GitHub上維護(hù)了一個(gè)代理池的項(xiàng)目，代理來(lái)源是抓取一些免費(fèi)的代理發(fā)布網(wǎng)站芦劣。上午有個(gè)小哥告訴我說(shuō)有個(gè)代理抓取接口不能用了，返回狀態(tài)521。抱著幫人解決問(wèn)題的心態(tài)去跑了一遍代碼特咆。發(fā)現(xiàn)果真是這樣。
通過(guò)Fiddler抓包比較录粱，基本可以確定是JavaScript生成加密Cookie導(dǎo)致原來(lái)的請(qǐng)求返回521腻格。
發(fā)現(xiàn)問(wèn)題
打開(kāi)Fiddler軟件，用瀏覽器打開(kāi)目標(biāo)站點(diǎn)(http://www.kuaidaili.com/proxylist/2/) 啥繁〔酥埃可以發(fā)現(xiàn)瀏覽器對(duì)這個(gè)頁(yè)面加載了兩次，第一次返回521旗闽，第二次才正常返回?cái)?shù)據(jù)酬核。很多沒(méi)有寫過(guò)網(wǎng)站或是爬蟲(chóng)經(jīng)驗(yàn)不足的童鞋，可能就會(huì)覺(jué)得奇怪為什么會(huì)這樣适室？為什么瀏覽器可能正常返回?cái)?shù)據(jù)而代碼卻不行嫡意？
仔細(xì)觀察兩次返回的結(jié)果可以發(fā)現(xiàn)：
1、第二次請(qǐng)求比第一次請(qǐng)求的Cookie內(nèi)容多了個(gè)這個(gè)_ydclearance=0c316df6ea04c5281b421aa8-5570-47ae-9768-2510d9fe9107-1490254971
2捣辆、第一次返回的內(nèi)容一些復(fù)雜看不懂的JS代碼蔬螟，第二次返回的就是正確的內(nèi)容
其實(shí)這是網(wǎng)站反爬蟲(chóng)的常用手段。大致過(guò)程是這樣的：首次請(qǐng)求數(shù)據(jù)時(shí)汽畴，服務(wù)端返回動(dòng)態(tài)的混淆加密過(guò)的JS旧巾，而這段JS的作用是給Cookie添加新的內(nèi)容用于服務(wù)端驗(yàn)證，此時(shí)返回的狀態(tài)碼是521忍些。瀏覽器帶上新的Cookie再次請(qǐng)求鲁猩，服務(wù)端驗(yàn)證Cookie通過(guò)返回?cái)?shù)據(jù)(這也是為嘛代碼不能返回?cái)?shù)據(jù)的原因)。
解決問(wèn)題
其實(shí)我第一次遇到這樣的問(wèn)題是坐昙，一開(kāi)始想的就是既然你是用JS生成的Cookie, 那么我也可以將JS函數(shù)翻譯成Python運(yùn)行绳匀。但是最后還是發(fā)現(xiàn)我太傻太天真，因?yàn)楝F(xiàn)在的JS都流行混淆加密炸客，原始的JS這樣的:
function lq(VA) {? ? var qo, mo = "", no = "", oo = [0x8c, 0xcd, 0x4c, 0xf9, 0xd7, 0x4d, 0x25, 0xba, 0x3c, 0x16, 0x96, 0x44, 0x8d, 0x0b, 0x90, 0x1e, 0xa3, 0x39, 0xc9, 0x86, 0x23, 0x61, 0x2f, 0xc8, 0x30, 0xdd, 0x57, 0xec, 0x92, 0x84, 0xc4, 0x6a, 0xeb, 0x99, 0x37, 0xeb, 0x25, 0x0e, 0xbb, 0xb0, 0x95, 0x76, 0x45, 0xde, 0x80, 0x59, 0xf6, 0x9c, 0x58, 0x39, 0x12, 0xc7, 0x9c, 0x8d, 0x18, 0xe0, 0xc5, 0x77, 0x50, 0x39, 0x01, 0xed, 0x93, 0x39, 0x02, 0x7e, 0x72, 0x4f, 0x24, 0x01, 0xe9, 0x66, 0x75, 0x4e, 0x2b, 0xd8, 0x6e, 0xe2, 0xfa, 0xc7, 0xa4, 0x85, 0x4e, 0xc2, 0xa5, 0x96, 0x6b, 0x58, 0x39, 0xd2, 0x7f, 0x44, 0xe5, 0x7b, 0x48, 0x2d, 0xf6, 0xdf, 0xbc, 0x31, 0x1e, 0xf6, 0xbf, 0x84, 0x6d, 0x5e, 0x33, 0x0c, 0x97, 0x5c, 0x39, 0x26, 0xf2, 0x9b, 0x77, 0x0d, 0xd6, 0xc0, 0x46, 0x38, 0x5f, 0xf4, 0xe2, 0x9f, 0xf1, 0x7b, 0xe8, 0xbe, 0x37, 0xdf, 0xd0, 0xbd, 0xb9, 0x36, 0x2c, 0xd1, 0xc3, 0x40, 0xe7, 0xcc, 0xa9, 0x52, 0x3b, 0x20, 0x40, 0x09, 0xe1, 0xd2, 0xa3, 0x80, 0x25, 0x0a, 0xb2, 0xd8, 0xce, 0x21, 0x69, 0x3e, 0xe6, 0x80, 0xfd, 0x73, 0xab, 0x51, 0xde, 0x60, 0x15, 0x95, 0x07, 0x94, 0x6a, 0x18, 0x9d, 0x37, 0x31, 0xde, 0x64, 0xdd, 0x63, 0xe3, 0x57, 0x05, 0x82, 0xff, 0xcc, 0x75, 0x79, 0x63, 0x09, 0xe2, 0x6c, 0x21, 0x5c, 0xe0, 0x7d, 0x4a, 0xf2, 0xd8, 0x9c, 0x22, 0xa3, 0x3d, 0xba, 0xa0, 0xaf, 0x30, 0xc1, 0x47, 0xf4, 0xca, 0xee, 0x64, 0xf9, 0x7b, 0x55, 0xd5, 0xd2, 0x4c, 0xc9, 0x7f, 0x25, 0xfe, 0x48, 0xcd, 0x4b, 0xcc, 0x81, 0x1b, 0x05, 0x82, 0x38, 0x0e, 0x83, 0x19, 0xe3, 0x65, 0x3f, 0xbf, 0x16, 0x88, 0x93, 0xdd, 0x3b];? ? qo = "qo=241; do{oo[qo]=(-oo[qo])&0xff; oo[qo]=(((oo[qo]>>3)|((oo[qo]<<5)&0xff))-70)&0xff;} while(--qo>=2);";? ? eval(qo);? ? qo = 240;? ? do {? ? ? ? oo[qo] = (oo[qo] - oo[qo - 1]) & 0xff;? ? } while (--qo >= 3);? ? qo = 1;? ? for (; ;) {? ? ? ? if (qo > 240) break;? ? ? ? oo[qo] = ((((((oo[qo] + 2) & 0xff) + 76) & 0xff) << 1) & 0xff) | (((((oo[qo] + 2) & 0xff) + 76) & 0xff) >> 7);? ? ? ? qo++;? ? }? ? po = "";? ? for (qo = 1; qo < oo.length - 1; qo++) if (qo % 6) po += String.fromCharCode(oo[qo] ^ VA);? ? eval("qo=eval;qo(po);");}
看到這樣的JS代碼疾棵，只能說(shuō)原諒我JS能力差，還原不了痹仙。是尔。。
但是前端經(jīng)驗(yàn)豐富的童鞋馬上就能想到還有種方法可解开仰，那就是利用瀏覽器的JS代碼調(diào)試功能拟枚。這樣一切就迎刃而解薪铜，新建一個(gè)html文件，將第一次返回的html原文復(fù)制進(jìn)去恩溅，保存用瀏覽器打開(kāi)隔箍，在eval之前打上斷點(diǎn)，看到這樣的輸出:
可以看到這個(gè)變量po為document.cookie='_ydclearance=0c316df6ea04c5281b421aa8-5570-47ae-9768-2510d9fe9107-1490254971; expires=Thu, 23-Mar-17 07:42:51 GMT; domain=.kuaidaili.com; path=/'; window.document.location=document.URL,下面還有個(gè)eval("qo=eval;qo(po);")脚乡。JS里面的eval和Python的差不多蜒滩，第二句的意思就是將eval方法賦給qo。然后去eval字符串po奶稠。而字符串po的前半段的意思是給瀏覽器添加Cooklie,后半段window.document.location=document.URL是刷新當(dāng)前頁(yè)面俯艰。
這也印證了我上面的說(shuō)法，首次請(qǐng)求沒(méi)有Cookie锌订，服務(wù)端回返回一段生成Cookie并自動(dòng)刷新的JS代碼竹握。瀏覽器拿到代碼能夠成功執(zhí)行，帶著新的Cookie再次請(qǐng)求獲取數(shù)據(jù)辆飘。而Python拿到這段代碼就只能停留在第一步啦辐。
那么如何才能使Python也能執(zhí)行這段JS呢，答案是PyV8劈猪。V8是Chromium中內(nèi)嵌的javascript引擎昧甘，號(hào)稱跑的最快。PyV8是用Python在V8的外部API包裝了一個(gè)python殼战得，這樣便可以使python可以直接與javascript操作充边。PyV8的安裝大家可以自行百度。
代碼
分析完成常侦，下面切入正題擼代碼浇冰。
首先是正常請(qǐng)求網(wǎng)頁(yè)，返回帶加密的JS函數(shù)的html:
import reimport PyV8import requestsTARGET_URL = "http://www.kuaidaili.com/proxylist/1/"def getHtml(url, cookie=None):? ? header = {? ? ? ? "Host": "www.kuaidaili.com",? ? ? ? 'Connection': 'keep-alive',? ? ? ? 'Cache-Control': 'max-age=0',? ? ? ? 'Upgrade-Insecure-Requests': '1',? ? ? ? 'User-Agent': 'Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/49.0.2623.87 Safari/537.36',? ? ? ? 'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8',? ? ? ? 'Accept-Encoding': 'gzip, deflate, sdch',? ? ? ? 'Accept-Language': 'zh-CN,zh;q=0.8',? ? }? ? html = requests.get(url=url, headers=header, timeout=30, cookies=cookie).content? ? return html# 第一次訪問(wèn)獲取動(dòng)態(tài)加密的JSfirst_html = getHtml(TARGET_URL)
由于返回的是html聋亡，并不單純的JS函數(shù)肘习，所以需要用正則提取JS函數(shù)的參數(shù)的參數(shù)。
# 提取其中的JS加密函數(shù)js_func = ''.join(re.findall(r'(function .*?)', first_html))print 'get js func:\n', js_func# 提取其中執(zhí)行JS函數(shù)的參數(shù)js_arg = ''.join(re.findall(r'setTimeout\(\"\D+\((\d+)\)\"', first_html))print 'get ja arg:\n', js_arg
還有一點(diǎn)需要注意坡倔，在JS函數(shù)中并沒(méi)有返回cookie漂佩，而是直接將cookie set到瀏覽器，所以我們需要將eval("qo=eval;qo(po);")替換成return po罪塔。這樣就能成功返回po中的內(nèi)容投蝉。
def executeJS(js_func_string, arg):? ? ctxt = PyV8.JSContext()? ? ctxt.enter()? ? func = ctxt.eval("({js})".format(js=js_func_string))? ? return func(arg)# 修改JS函數(shù)，使其返回Cookie內(nèi)容js_func = js_func.replace('eval("qo=eval;qo(po);")', 'return po')# 執(zhí)行JS獲取Cookiecookie_str = executeJS(js_func, js_arg)
這樣返回的cookie是字符串格式征堪，但是用requests.get()需要字典形式瘩缆，所以將其轉(zhuǎn)換成字典：
def parseCookie(string):? ? string = string.replace("document.cookie='", "")? ? clearance = string.split(';')[0]? ? return {clearance.split('=')[0]: clearance.split('=')[1]}# 將Cookie轉(zhuǎn)換為字典格式cookie = parseCookie(cookie_str)
最后帶上解析出來(lái)的Cookie再次訪問(wèn)網(wǎng)頁(yè)，成功獲取數(shù)據(jù):
# 帶上Cookie再次訪問(wèn)url,獲取正確數(shù)據(jù)print getHtml(TARGET_URL, cookie)[0:500]
下面是完整代碼:
# -*- coding: utf-8 -*-"""-------------------------------------------------? File Name：? ? demo_1.py.py? ? Description :? Python爬蟲(chóng)—破解JS加密的Cookie 快代理網(wǎng)站為例：http://www.kuaidaili.com/proxylist/1/? ? ? ? ? ? ? ? ? Document:? Author :? ? ? JHao? date：? ? ? ? ? 2017/3/23-------------------------------------------------? Change Activity:? ? ? ? ? ? ? ? ? 2017/3/23: 破解JS加密的Cookie-------------------------------------------------"""__author__ = 'JHao'import reimport PyV8import requestsTARGET_URL = "http://www.kuaidaili.com/proxylist/1/"def getHtml(url, cookie=None):? ? header = {? ? ? ? "Host": "www.kuaidaili.com",? ? ? ? 'Connection': 'keep-alive',? ? ? ? 'Cache-Control': 'max-age=0',? ? ? ? 'Upgrade-Insecure-Requests': '1',? ? ? ? 'User-Agent': 'Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/49.0.2623.87 Safari/537.36',? ? ? ? 'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8',? ? ? ? 'Accept-Encoding': 'gzip, deflate, sdch',? ? ? ? 'Accept-Language': 'zh-CN,zh;q=0.8',? ? }? ? html = requests.get(url=url, headers=header, timeout=30, cookies=cookie).content? ? return htmldef executeJS(js_func_string, arg):? ? ctxt = PyV8.JSContext()? ? ctxt.enter()? ? func = ctxt.eval("({js})".format(js=js_func_string))? ? return func(arg)def parseCookie(string):? ? string = string.replace("document.cookie='", "")? ? clearance = string.split(';')[0]? ? return {clearance.split('=')[0]: clearance.split('=')[1]}# 第一次訪問(wèn)獲取動(dòng)態(tài)加密的JSfirst_html = getHtml(TARGET_URL)# first_html = """# window.onload=setTimeout("lu(158)", 200); function lu(OE) {var qo, mo="", no="", oo = [0x64,0xaa,0x98,0x3d,0x56,0x64,0x8b,0xb0,0x88,0xe1,0x0d,0xf4,0x99,0x31,0xd8,0xb6,0x5d,0x73,0x98,0xc3,0xc4,0x7a,0x1e,0x38,0x9d,0xe8,0x8d,0xe4,0x0a,0x2e,0x6c,0x45,0x69,0x41,0xe5,0xd0,0xe5,0x11,0x0b,0x35,0x7b,0xe4,0x09,0xb1,0x2b,0x6d,0x82,0x7c,0x25,0xdd,0x70,0x5a,0xc4,0xaa,0xd3,0x74,0x98,0x42,0x3c,0x60,0x2d,0x42,0x66,0xe0,0x0a,0x2e,0x96,0xbb,0xe2,0x1d,0x38,0xdc,0xb1,0xd6,0x0e,0x0d,0x76,0xae,0xc3,0xa9,0x3b,0x62,0x47,0x40,0x15,0x93,0xb7,0xee,0xc3,0x3e,0xfd,0xd3,0x0d,0xf6,0x61,0xdc,0xf1,0x2c,0x54,0x8c,0x90,0xfa,0x24,0x5b,0x83,0x0c,0x75,0xaf,0x18,0x01,0x7e,0x68,0xe0,0x0a,0x72,0x1e,0x88,0x33,0xa7,0xcc,0x31,0x9b,0xf3,0x1a,0xf2,0x9a,0xbf,0x58,0x83,0xe4,0x87,0xed,0x07,0x7e,0xe2,0x00,0xe9,0x92,0xc9,0xe8,0x59,0x7d,0x56,0x8d,0xb5,0xb2,0x6c,0xe0,0x49,0x73,0xfc,0xe7,0x20,0x49,0x34,0x09,0x71,0xeb,0x60,0xfd,0x8e,0xad,0x0f,0xb9,0x2e,0x77,0xdc,0x74,0x9b,0xbf,0x8f,0xa5,0x8d,0xb8,0xb0,0x06,0xac,0xc5,0xe9,0x10,0x12,0x77,0x9b,0xb1,0x19,0x4e,0x64,0x5c,0x00,0x98,0xc6,0xed,0x98,0x0d,0x65,0x11,0x35,0x9e,0xf4,0x30,0x93,0x4b,0x00,0xab,0x20,0x8f,0x29,0x4f,0x27,0x8c,0xc2,0x6a,0x04,0xfb,0x51,0xa3,0x4b,0xef,0x09,0x30,0x28,0x4d,0x25,0x8e,0x76,0x58,0xbf,0x57,0xfb,0x20,0x78,0xd1,0xf7,0x9f,0x77,0x0f,0x3a,0x9f,0x37,0xdb,0xd3,0xfc,0x14,0x39,0x11,0x3b,0x94,0x8c,0xad,0x8e,0x5c,0xd3,0x3b];qo = "qo=251; do{oo[qo]=(-oo[qo])&0xff; oo[qo]=(((oo[qo]>>4)|((oo[qo]=2);"; eval(qo);qo = 250; do { oo[qo] = (oo[qo] - oo[qo - 1]) & 0xff; } while (-- qo >= 3 );qo = 1; for (;;) { if (qo > 250) break; oo[qo] = ((((((oo[qo] + 200) & 0xff) + 121) & 0xff) > 2); qo++;}po = ""; for (qo = 1; qo # """# 提取其中的JS加密函數(shù)js_func = ''.join(re.findall(r'(function .*?)', first_html))print 'get js func:\n', js_func# 提取其中執(zhí)行JS函數(shù)的參數(shù)js_arg = ''.join(re.findall(r'setTimeout\(\"\D+\((\d+)\)\"', first_html))print 'get ja arg:\n', js_arg# 修改JS函數(shù)佃蚜，使其返回Cookie內(nèi)容js_func = js_func.replace('eval("qo=eval;qo(po);")', 'return po')# 執(zhí)行JS獲取Cookiecookie_str = executeJS(js_func, js_arg)# 將Cookie轉(zhuǎn)換為字典格式cookie = parseCookie(cookie_str)print cookie# 帶上Cookie再次訪問(wèn)url,獲取正確數(shù)據(jù)print getHtml(TARGET_URL, cookie)[0:500]
