高級(jí)PHP應(yīng)用程序漏洞審核技術(shù)

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• 高級(jí)PHP應(yīng)用程序漏洞審核技術(shù)
• 前言
• 傳統(tǒng)的代碼審計(jì)技術(shù)
• PHP版本與應(yīng)用代碼審計(jì)
• 其他的因素與應(yīng)用代碼審計(jì)
• 擴(kuò)展我們的字典
• 變量本身的key
• 變量覆蓋
• 遍歷初始化變量
• parse_str()變量覆蓋漏洞
• import_request_variables()變量覆蓋漏洞
• PHP5 Globals
• magic_quotes_gpc與代碼安全
• 什么是magic_quotes_gpc
• 哪些地方?jīng)]有魔術(shù)引號(hào)的保護(hù)
• 變量的編碼與解碼
• 二次攻擊
• 魔術(shù)引號(hào)帶來(lái)的新的安全問(wèn)題
• 變量key與魔術(shù)引號(hào)
• 代碼注射
• PHP中可能導(dǎo)致代碼注射的函數(shù)
• 變量函數(shù)與雙引號(hào)
• PHP自身函數(shù)漏洞及缺陷
• PHP函數(shù)的溢出漏洞
• PHP函數(shù)的其他漏洞
• session_destroy()刪除文件漏洞
• 隨機(jī)函數(shù)
• 特殊字符
• 截?cái)?/li>
  • include截?cái)?/li>
  • 數(shù)據(jù)截?cái)?/li>
  • 文件操作里的特殊字符
• 怎么進(jìn)一步尋找新的字典
• DEMO
• 后話
• 附錄

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前言

PHP是一種被廣泛使用的腳本語(yǔ)言，尤其適合于web開發(fā)。具有跨平臺(tái)，容易學(xué)習(xí)，功能強(qiáng)大等特點(diǎn)，據(jù)統(tǒng)計(jì)全世界有超過(guò)34%的網(wǎng)站有php的應(yīng)用，包括Yahoo、sina、163、sohu等大型門戶網(wǎng)站。而且很多具名的web應(yīng)用系統(tǒng)（包括bbs,blog,wiki,cms等等）都是使用php開發(fā)的，Discuz、phpwind、phpbb、vbb、wordpress、boblog等等。隨著web安全的熱點(diǎn)升級(jí)，php應(yīng)用程序的代碼安全問(wèn)題也逐步興盛起來(lái)，越來(lái)越多的安全人員投入到這個(gè)領(lǐng)域，越來(lái)越多的應(yīng)用程序代碼漏洞被披露。針對(duì)這樣一個(gè)狀況，很多應(yīng)用程序的官方都成立了安全部門，或者雇傭安全人員進(jìn)行代碼審計(jì)，因此出現(xiàn)了很多自動(dòng)化商業(yè)化的代碼審計(jì)工具。也就是這樣的形勢(shì)導(dǎo)致了一個(gè)局面：大公司的產(chǎn)品安全系數(shù)大大的提高，那些很明顯的漏洞基本滅絕了，那些大家都知道的審計(jì)技術(shù)都無(wú)用武之地了。我們面對(duì)很多工具以及大牛掃描過(guò)n遍的代碼，有很多的安全人員有點(diǎn)悲觀，而有的官方安全人員也非常的放心自己的代碼，但是不要忘記了“沒有絕對(duì)的安全”，我們應(yīng)該去尋找新的途徑挖掘新的漏洞。本文就給介紹了一些非傳統(tǒng)的技術(shù)經(jīng)驗(yàn)和大家分享。

另外在這里特別說(shuō)明一下本文里面很多漏洞都是來(lái)源于網(wǎng)絡(luò)上牛人和朋友們的分享，在這里需要感謝他們 ：）

傳統(tǒng)的代碼審計(jì)技術(shù)

WEB應(yīng)用程序漏洞查找基本上是圍繞兩個(gè)元素展開：變量與函數(shù)。也就是說(shuō)一漏洞的利用必須把你提交的惡意代碼通過(guò)變量經(jīng)過(guò)n次變量轉(zhuǎn)換傳遞，最終傳遞給目標(biāo)函數(shù)執(zhí)行，還記得MS那句經(jīng)典的名言嗎？“一切輸入都是有害的”。這句話只強(qiáng)調(diào)了變量輸入，很多程序員把“輸入”理解為只是gpc[$_GET,$_POST,$_COOKIE]，但是變量在傳遞過(guò)程產(chǎn)生了n多的變化。導(dǎo)致很多過(guò)濾只是個(gè)“紙老虎”！我們換句話來(lái)描敘下代碼安全：“一切進(jìn)入函數(shù)的變量是有害的”。

PHP代碼審計(jì)技術(shù)用的最多也是目前的主力方法：靜態(tài)分析，主要也是通過(guò)查找容易導(dǎo)致安全漏洞的危險(xiǎn)函數(shù)，常用的如grep，findstr等搜索工具，很多自動(dòng)化工具也是使用正則來(lái)搜索這些函數(shù)。下面列舉一些常用的函數(shù)，也就是下文說(shuō)的字典（暫略）。但是目前基本已有的字典很難找到漏洞，所以我們需要擴(kuò)展我們的字典，這些字典也是本文主要探討的。

其他的方法有：通過(guò)修改PHP源代碼來(lái)分析變量流程，或者h(yuǎn)ook危險(xiǎn)的函數(shù)來(lái)實(shí)現(xiàn)對(duì)應(yīng)用程序代碼的審核，但是這些也依靠了我們上面提到的字典。

PHP版本與應(yīng)用代碼審計(jì)

到目前為止，PHP主要有3個(gè)版本：php4、php5、php6，使用比例大致如下：

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由于php缺少自動(dòng)升級(jí)的機(jī)制，導(dǎo)致目前PHP版本并存，也導(dǎo)致很多存在漏洞沒有被修補(bǔ)。這些有漏洞的函數(shù)也是我們進(jìn)行WEB應(yīng)用程序代碼審計(jì)的重點(diǎn)對(duì)象，也是我們字典重要來(lái)源。

其他的因素與應(yīng)用代碼審計(jì)

很多代碼審計(jì)者拿到代碼就看，他們忽視了“安全是一個(gè)整體”，代碼安全很多的其他因素有關(guān)系，比如上面我們談到的PHP版本的問(wèn)題，比較重要的還有操作系統(tǒng)類型（主要是兩大陣營(yíng)win/*nix），WEB服務(wù)端軟件（主要是iis/apache兩大類型）等因素。這是由于不同的系統(tǒng)不同的WEB SERVER有著不同的安全特點(diǎn)或特性，下文有些部分會(huì)涉及。

所以我們?cè)谧瞿硞€(gè)公司W(wǎng)EB應(yīng)用代碼審計(jì)時(shí)，應(yīng)該了解他們使用的系統(tǒng)，WEB服務(wù)端軟件，PHP版本等信息。

擴(kuò)展我們的字典

下面將詳細(xì)介紹一些非傳統(tǒng)PHP應(yīng)用代碼審計(jì)一些漏洞類型和利用技巧。

變量本身的key

說(shuō)到變量的提交很多人只是看到了GET/POST/COOKIE等提交的變量的值，但是忘記了有的程序把變量本身的key也當(dāng)變量提取給函數(shù)處理。

<span style="color: #666600;" class="pun"><?</span><span class="pln">php</span><span style="color: #880000;" class="com">//key.php?aaaa'aaa=1&bb'b=2 </span><span class="pln"></span><span style="color: #880000;" class="com">//print_R($_GET); </span><span class="pln">?</span><span style="color: #000088;" class="kwd">foreach</span><span style="color: #666600;" class="pun">(</span><span class="pln">$_GET AS $key </span><span style="color: #666600;" class="pun">=></span><span class="pln"> $value</span><span style="color: #666600;" class="pun">)</span><span class="pln"></span><span style="color: #666600;" class="pun">{</span><span class="pln">? ? ? ? </span><span style="color: #000088;" class="kwd">print</span><span class="pln"> $key</span><span style="color: #666600;" class="pun">.</span><span style="color: #008800;" class="str">"\n"</span><span style="color: #666600;" class="pun">;</span><span class="pln"></span><span style="color: #666600;" class="pun">}</span><span class="pln"></span><span style="color: #666600;" class="pun">?></span>

上面的代碼就提取了變量本身的key顯示出來(lái)，單純對(duì)于上面的代碼，如果我們提交URL：

<span class="pln">key</span><span style="color: #666600;" class="pun">.</span><span class="pln">php</span><span style="color: #666600;" class="pun">?<</span><span class="pln">script</span><span style="color: #666600;" class="pun">></span><span class="pln">alert</span><span style="color: #666600;" class="pun">(</span><span style="color: #006666;" class="lit">1</span><span style="color: #666600;" class="pun">);</</span><span class="pln">script</span><span style="color: #666600;" class="pun">>=</span><span style="color: #006666;" class="lit">1</span><span style="color: #666600;" class="pun">&</span><span class="pln">bbb</span><span style="color: #666600;" class="pun">=</span><span style="color: #006666;" class="lit">2</span>

那么就導(dǎo)致一個(gè)xss的漏洞，擴(kuò)展一下如果這個(gè)key提交給include()等函數(shù)或者sql查詢呢？：）

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變量覆蓋

很多的漏洞查找者都知道extract()這個(gè)函數(shù)在指定參數(shù)為EXTR_OVERWRITE或者沒有指定函數(shù)可以導(dǎo)致變量覆蓋，但是還有很多其他情況導(dǎo)致變量覆蓋的如：

遍歷初始化變量

請(qǐng)看如下代碼：

<span style="color: #666600;" class="pun"><?</span><span class="pln">php</span><span style="color: #880000;" class="com">//var.php?a=fuck</span><span class="pln">$a</span><span style="color: #666600;" class="pun">=</span><span style="color: #008800;" class="str">'hi'</span><span style="color: #666600;" class="pun">;</span><span class="pln"></span><span style="color: #000088;" class="kwd">foreach</span><span style="color: #666600;" class="pun">(</span><span class="pln">$_GET </span><span style="color: #000088;" class="kwd">as</span><span class="pln"> $key </span><span style="color: #666600;" class="pun">=></span><span class="pln"> $value</span><span style="color: #666600;" class="pun">)</span><span style="color: #666600;" class="pun">{</span><span class="pln">? ? ? ? $$key </span><span style="color: #666600;" class="pun">=</span><span class="pln"> $value</span><span style="color: #666600;" class="pun">;</span><span class="pln"></span><span style="color: #666600;" class="pun">}</span><span class="pln"></span><span style="color: #000088;" class="kwd">print</span><span class="pln"> $a</span><span style="color: #666600;" class="pun">;</span><span class="pln"></span><span style="color: #666600;" class="pun">?></span>

很多的WEB應(yīng)用都使用上面的方式（注意循環(huán)不一定是foreach），如Discuz!4.1的WAP部分的代碼：

<span class="pln">$chs </span><span style="color: #666600;" class="pun">=</span><span style="color: #008800;" class="str">''</span><span style="color: #666600;" class="pun">;</span><span class="pln"></span><span style="color: #000088;" class="kwd">if</span><span style="color: #666600;" class="pun">(</span><span class="pln">$_POST </span><span style="color: #666600;" class="pun">&&</span><span class="pln"> $charset </span><span style="color: #666600;" class="pun">!=</span><span style="color: #008800;" class="str">'utf-8'</span><span style="color: #666600;" class="pun">)</span><span style="color: #666600;" class="pun">{</span><span class="pln">? ? ? ? $chs </span><span style="color: #666600;" class="pun">=</span><span style="color: #000088;" class="kwd">new</span><span style="color: #660066;" class="typ">Chinese</span><span style="color: #666600;" class="pun">(</span><span style="color: #008800;" class="str">'UTF-8'</span><span style="color: #666600;" class="pun">,</span><span class="pln"> $charset</span><span style="color: #666600;" class="pun">);</span><span class="pln">? ? ? ? </span><span style="color: #000088;" class="kwd">foreach</span><span style="color: #666600;" class="pun">(</span><span class="pln">$_POST </span><span style="color: #000088;" class="kwd">as</span><span class="pln"> $key </span><span style="color: #666600;" class="pun">=></span><span class="pln"> $value</span><span style="color: #666600;" class="pun">)</span><span style="color: #666600;" class="pun">{</span><span class="pln">? ? ? ? ? ? ? ? $$key </span><span style="color: #666600;" class="pun">=</span><span class="pln"> $chs</span><span style="color: #666600;" class="pun">-></span><span style="color: #660066;" class="typ">Convert</span><span style="color: #666600;" class="pun">(</span><span class="pln">$value</span><span style="color: #666600;" class="pun">);</span><span class="pln">? ? ? ? </span><span style="color: #666600;" class="pun">}</span><span class="pln">? ? ? ? unset</span><span style="color: #666600;" class="pun">(</span><span class="pln">$chs</span><span style="color: #666600;" class="pun">);</span>

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parse_str()變量覆蓋漏洞

<span style="color: #880000;" class="com">//var.php?var=new</span><span class="pln">$var </span><span style="color: #666600;" class="pun">=</span><span style="color: #008800;" class="str">'init'</span><span style="color: #666600;" class="pun">;</span><span class="pln"> ? ? ? ? ? ? ? ? ? ? parse_str</span><span style="color: #666600;" class="pun">(</span><span class="pln">$_SERVER</span><span style="color: #666600;" class="pun">[</span><span style="color: #008800;" class="str">'QUERY_STRING'</span><span style="color: #666600;" class="pun">]);</span><span class="pln"> </span><span style="color: #000088;" class="kwd">print</span><span class="pln"> $var</span><span style="color: #666600;" class="pun">;</span>

該函數(shù)一樣可以覆蓋數(shù)組變量，上面的代碼是通過(guò)$_SERVER['QUERY_STRING']來(lái)提取變量的，對(duì)于指定了變量名的我們可以通過(guò)注射“=”來(lái)實(shí)現(xiàn)覆蓋其他的變量：

<span style="color: #880000;" class="com">//var.php?var=1&a[1]=var1%3d222</span><span class="pln">$var1 </span><span style="color: #666600;" class="pun">=</span><span style="color: #008800;" class="str">'init'</span><span style="color: #666600;" class="pun">;</span><span class="pln">parse_str</span><span style="color: #666600;" class="pun">(</span><span class="pln">$a</span><span style="color: #666600;" class="pun">[</span><span class="pln">$_GET</span><span style="color: #666600;" class="pun">[</span><span style="color: #008800;" class="str">'var'</span><span style="color: #666600;" class="pun">]]);</span><span class="pln"></span><span style="color: #000088;" class="kwd">print</span><span class="pln"> $var1</span><span style="color: #666600;" class="pun">;</span>

上面的代碼通過(guò)提交$var來(lái)實(shí)現(xiàn)對(duì)$var1的覆蓋。

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import_request_variables()變量覆蓋漏洞

<span style="color: #880000;" class="com">//var.php?_SERVER[REMOTE_ADDR]=10.1.1.1</span><span class="pln">echo </span><span style="color: #008800;" class="str">'GLOBALS '</span><span style="color: #666600;" class="pun">.(</span><span style="color: #000088;" class="kwd">int</span><span style="color: #666600;" class="pun">)</span><span class="pln">ini_get</span><span style="color: #666600;" class="pun">(</span><span style="color: #008800;" class="str">"register_globals"</span><span style="color: #666600;" class="pun">).</span><span style="color: #008800;" class="str">"n"</span><span style="color: #666600;" class="pun">;</span><span class="pln">import_request_variables</span><span style="color: #666600;" class="pun">(</span><span style="color: #008800;" class="str">'GPC'</span><span style="color: #666600;" class="pun">);</span><span class="pln"></span><span style="color: #000088;" class="kwd">if</span><span style="color: #666600;" class="pun">(</span><span class="pln">$_SERVER</span><span style="color: #666600;" class="pun">[</span><span style="color: #008800;" class="str">'REMOTE_ADDR'</span><span style="color: #666600;" class="pun">]</span><span style="color: #666600;" class="pun">!=</span><span style="color: #008800;" class="str">'10.1.1.1'</span><span style="color: #666600;" class="pun">)</span><span style="color: #000088;" class="kwd">die</span><span style="color: #666600;" class="pun">(</span><span style="color: #008800;" class="str">'Go away!'</span><span style="color: #666600;" class="pun">);</span><span class="pln">echo </span><span style="color: #008800;" class="str">'Hello admin!'</span><span style="color: #666600;" class="pun">;</span>

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PHP5 Globals

從嚴(yán)格意義上來(lái)說(shuō)這個(gè)不可以算是PHP的漏洞，只能算是一個(gè)特性，測(cè)試代碼：

<span style="color: #666600;" class="pun"><?</span><span class="pln"></span><span style="color: #880000;" class="com">// register_globals =ON</span><span class="pln"></span><span style="color: #880000;" class="com">//foo.php?GLOBALS[foobar]=HELLO</span><span class="pln">php echo $foobar</span><span style="color: #666600;" class="pun">;</span><span class="pln"> </span><span style="color: #666600;" class="pun">?></span>

但是很多的程序沒有考慮到這點(diǎn)，請(qǐng)看如下代碼：

<span style="color: #880000;" class="com">//為了安全取消全局變量</span><span class="pln"></span><span style="color: #880000;" class="com">//var.php?GLOBALS[a]=aaaa&b=111</span><span class="pln"></span><span style="color: #000088;" class="kwd">if</span><span style="color: #666600;" class="pun">(</span><span class="pln">ini_get</span><span style="color: #666600;" class="pun">(</span><span style="color: #008800;" class="str">'register_globals'</span><span style="color: #666600;" class="pun">))</span><span style="color: #000088;" class="kwd">foreach</span><span style="color: #666600;" class="pun">(</span><span class="pln">$_REQUEST </span><span style="color: #000088;" class="kwd">as</span><span class="pln"> $k</span><span style="color: #666600;" class="pun">=></span><span class="pln">$v</span><span style="color: #666600;" class="pun">)</span><span class="pln"> unset</span><span style="color: #666600;" class="pun">(</span><span class="pln">$</span><span style="color: #666600;" class="pun">{</span><span class="pln">$k</span><span style="color: #666600;" class="pun">});</span><span class="pln"></span><span style="color: #000088;" class="kwd">print</span><span class="pln"> $a</span><span style="color: #666600;" class="pun">;</span><span class="pln"></span><span style="color: #000088;" class="kwd">print</span><span class="pln"> $_GET</span><span style="color: #666600;" class="pun">[</span><span class="pln">b</span><span style="color: #666600;" class="pun">];</span>

如果熟悉WEB2.0的攻擊的同學(xué)，很容易想到上面的代碼我們可以利用這個(gè)特性進(jìn)行crsf攻擊。

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magic_quotes_gpc與代碼安全

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什么是magic_quotes_gpc

當(dāng)打開時(shí)，所有的 '（單引號(hào)），"（雙引號(hào)），\（反斜線）和 NULL 字符都會(huì)被自動(dòng)加上一個(gè)反斜線進(jìn)行轉(zhuǎn)義。還有很多函數(shù)有類似的作用 如：addslashes()、mysql_escape_string()、mysql_real_escape_string()等，另外還有parse_str()后的變量也受magic_quotes_gpc的影響。目前大多數(shù)的主機(jī)都打開了這個(gè)選項(xiàng)，并且很多程序員也注意使用上面那些函數(shù)去過(guò)濾變量，這看上去很安全。很多漏洞查找者或者工具遇到些函數(shù)過(guò)濾后的變量直接就放棄，但是就在他們放棄的同時(shí)也放過(guò)很多致命的安全漏洞。 ：）

哪些地方?jīng)]有魔術(shù)引號(hào)的保護(hù)

1) $_SERVER變量

PHP5的$_SERVER變量缺少magic_quotes_gpc的保護(hù)，導(dǎo)致近年來(lái)X-Forwarded-For的漏洞猛暴，所以很多程序員考慮過(guò)濾X-Forwarded-For，但是其他的變量呢？

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2) getenv()得到的變量（使用類似$_SERVER變量）

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3) $HTTP_RAW_POST_DATA與PHP輸入、輸出流

主要應(yīng)用與soap/xmlrpc/webpublish功能里，請(qǐng)看如下代碼：

<span style="color: #000088;" class="kwd">if</span><span style="color: #666600;" class="pun">(</span><span style="color: #666600;" class="pun">!</span><span class="pln">isset</span><span style="color: #666600;" class="pun">(</span><span class="pln"> $HTTP_RAW_POST_DATA </span><span style="color: #666600;" class="pun">)</span><span style="color: #666600;" class="pun">)</span><span style="color: #666600;" class="pun">{</span><span class="pln">? ? ? ? $HTTP_RAW_POST_DATA </span><span style="color: #666600;" class="pun">=</span><span class="pln"> file_get_contents</span><span style="color: #666600;" class="pun">(</span><span style="color: #008800;" class="str">'php://input'</span><span style="color: #666600;" class="pun">);</span><span class="pln"></span><span style="color: #666600;" class="pun">}</span><span class="pln"></span><span style="color: #000088;" class="kwd">if</span><span style="color: #666600;" class="pun">(</span><span class="pln"> isset</span><span style="color: #666600;" class="pun">(</span><span class="pln">$HTTP_RAW_POST_DATA</span><span style="color: #666600;" class="pun">)</span><span style="color: #666600;" class="pun">)</span><span class="pln">? ? ? ? $HTTP_RAW_POST_DATA </span><span style="color: #666600;" class="pun">=</span><span class="pln"> trim</span><span style="color: #666600;" class="pun">(</span><span class="pln">$HTTP_RAW_POST_DATA</span><span style="color: #666600;" class="pun">);</span>

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4) 數(shù)據(jù)庫(kù)操作容易忘記'的地方如：in()/limit/order by/group by

如Discuz!<5.0的pm.php：

<span style="color: #000088;" class="kwd">if</span><span style="color: #666600;" class="pun">(</span><span class="pln">is_array</span><span style="color: #666600;" class="pun">(</span><span class="pln">$msgtobuddys</span><span style="color: #666600;" class="pun">))</span><span style="color: #666600;" class="pun">{</span><span class="pln">? ? ? ? $msgto </span><span style="color: #666600;" class="pun">=</span><span class="pln"> array_merge</span><span style="color: #666600;" class="pun">(</span><span class="pln">$msgtobuddys</span><span style="color: #666600;" class="pun">,</span><span class="pln"> array</span><span style="color: #666600;" class="pun">(</span><span class="pln">$msgtoid</span><span style="color: #666600;" class="pun">));</span><span class="pln">? ? ? ? ? ? ? ? </span><span style="color: #666600;" class="pun">......</span><span class="pln"></span><span style="color: #000088;" class="kwd">foreach</span><span style="color: #666600;" class="pun">(</span><span class="pln">$msgto </span><span style="color: #000088;" class="kwd">as</span><span class="pln"> $uid</span><span style="color: #666600;" class="pun">)</span><span style="color: #666600;" class="pun">{</span><span class="pln">? ? ? ? $uids </span><span style="color: #666600;" class="pun">.=</span><span class="pln"> $comma</span><span style="color: #666600;" class="pun">.</span><span class="pln">$uid</span><span style="color: #666600;" class="pun">;</span><span class="pln">? ? ? ? $comma </span><span style="color: #666600;" class="pun">=</span><span style="color: #008800;" class="str">','</span><span style="color: #666600;" class="pun">;</span><span class="pln"></span><span style="color: #666600;" class="pun">}</span><span class="pln"></span><span style="color: #666600;" class="pun">......</span><span class="pln">$query </span><span style="color: #666600;" class="pun">=</span><span class="pln"> $db</span><span style="color: #666600;" class="pun">-></span><span class="pln">query</span><span style="color: #666600;" class="pun">(</span><span style="color: #008800;" class="str">"SELECT m.username, mf.ignorepm FROM {$tablepre}members m? ? ? ? LEFT JOIN {$tablepre}memberfields mf USING(uid)? ? ? ? WHERE m.uid IN ($uids)"</span><span style="color: #666600;" class="pun">);</span>

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變量的編碼與解碼

一個(gè)WEB程序很多功能的實(shí)現(xiàn)都需要變量的編碼解碼，而且就在這一轉(zhuǎn)一解的傳遞過(guò)程中就悄悄的繞過(guò)你的過(guò)濾的安全防線。

這個(gè)類型的主要函數(shù)有：

1) stripslashes() 這個(gè)其實(shí)就是一個(gè)decode-addslashes()

2) 其他字符串轉(zhuǎn)換函數(shù)：

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另外一個(gè) unserialize/serialize

3) 字符集函數(shù)（GKB,UTF7/8...）如iconv()/mb_convert_encoding()等

目前很多漏洞挖掘者開始注意這一類型的漏洞了，如典型的urldecode：

<span class="pln">$sql </span><span style="color: #666600;" class="pun">=</span><span style="color: #008800;" class="str">"SELECT * FROM article WHERE articleid='"</span><span style="color: #666600;" class="pun">.</span><span class="pln">urldecode</span><span style="color: #666600;" class="pun">(</span><span class="pln">$_GET</span><span style="color: #666600;" class="pun">[</span><span class="pln">id</span><span style="color: #666600;" class="pun">]).</span><span style="color: #008800;" class="str">"'"</span><span style="color: #666600;" class="pun">;</span>

當(dāng)magic_quotes_gpc=on時(shí)，我們提交?id=%2527，得到sql語(yǔ)句為：

<span class="pln">SELECT </span><span style="color: #666600;" class="pun">*</span><span class="pln"> FROM article WHERE articleid</span><span style="color: #666600;" class="pun">=</span><span style="color: #008800;" class="str">'''</span>

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二次攻擊

詳細(xì)見附錄[1]

1)數(shù)據(jù)庫(kù)出來(lái)的變量沒有進(jìn)行過(guò)濾

2)數(shù)據(jù)庫(kù)的轉(zhuǎn)義符號(hào)：

• mysql/oracle轉(zhuǎn)義符號(hào)同樣是\（我們提交'通過(guò)魔術(shù)引號(hào)變化為\'，當(dāng)我們update進(jìn)入數(shù)據(jù)庫(kù)時(shí)，通過(guò)轉(zhuǎn)義變?yōu)?）
• mssql的轉(zhuǎn)義字符為'（所以我們提交'通過(guò)魔術(shù)引號(hào)變化為\'，mssql會(huì)把它當(dāng)為一個(gè)字符串直接處理，所以魔術(shù)引號(hào)對(duì)于mssql的注射沒有任何意義）

從這里我們可以思考得到一個(gè)結(jié)論：一切進(jìn)入函數(shù)的變量都是有害的，另外利用二次攻擊我們可以實(shí)現(xiàn)一個(gè)webrootkit，把我們的惡意構(gòu)造直接放到數(shù)據(jù)庫(kù)里。我們應(yīng)當(dāng)把這樣的代碼看成一個(gè)vul？

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魔術(shù)引號(hào)帶來(lái)的新的安全問(wèn)題

首先我們看下魔術(shù)引號(hào)的處理機(jī)制：

<span style="color: #666600;" class="pun">[\-->\\,</span><span style="color: #008800;" class="str">'-->\',"-->\",null-->\0]</span>

這給我們引進(jìn)了一個(gè)非常有用的符號(hào)“\”，“\”符號(hào)不僅僅是轉(zhuǎn)義符號(hào)，在WIN系統(tǒng)下也是目錄轉(zhuǎn)跳的符號(hào)。這個(gè)特點(diǎn)可能導(dǎo)致php應(yīng)用程序里產(chǎn)生非常有意思的漏洞：

1)得到原字符（',\,",null]）

<span class="pln">$order_sn</span><span style="color: #666600;" class="pun">=</span><span class="pln">substr</span><span style="color: #666600;" class="pun">(</span><span class="pln">$_GET</span><span style="color: #666600;" class="pun">[</span><span style="color: #008800;" class="str">'order_sn'</span><span style="color: #666600;" class="pun">],</span><span style="color: #006666;" class="lit">1</span><span style="color: #666600;" class="pun">);</span><span class="pln"></span><span style="color: #880000;" class="com">//提交 ? ? ? ? ? ? ? ? '</span><span class="pln"></span><span style="color: #880000;" class="com">//魔術(shù)引號(hào)處理 ? ? ? ? \'</span><span class="pln"></span><span style="color: #880000;" class="com">//substr ? ? ? ? ? ? ? '</span><span class="pln">$sql </span><span style="color: #666600;" class="pun">=</span><span style="color: #008800;" class="str">"SELECT order_id, order_status, shipping_status, pay_status, "</span><span style="color: #666600;" class="pun">.</span><span class="pln">? ?</span><span style="color: #008800;" class="str">" shipping_time, shipping_id, invoice_no, user_id "</span><span style="color: #666600;" class="pun">.</span><span class="pln">? ?</span><span style="color: #008800;" class="str">" FROM "</span><span style="color: #666600;" class="pun">.</span><span class="pln"> $ecs</span><span style="color: #666600;" class="pun">-></span><span class="pln">table</span><span style="color: #666600;" class="pun">(</span><span style="color: #008800;" class="str">'order_info'</span><span style="color: #666600;" class="pun">).</span><span class="pln">? ?</span><span style="color: #008800;" class="str">" WHERE order_sn = '$order_sn' LIMIT 1"</span><span style="color: #666600;" class="pun">;</span>

2)得到“\”字符

<span class="pln">$order_sn</span><span style="color: #666600;" class="pun">=</span><span class="pln">substr</span><span style="color: #666600;" class="pun">(</span><span class="pln">$_GET</span><span style="color: #666600;" class="pun">[</span><span style="color: #008800;" class="str">'order_sn'</span><span style="color: #666600;" class="pun">],</span><span style="color: #006666;" class="lit">0</span><span style="color: #666600;" class="pun">,</span><span style="color: #006666;" class="lit">1</span><span style="color: #666600;" class="pun">);</span><span class="pln"></span><span style="color: #880000;" class="com">//提交 ? ? ? ? ? ? ? ? '</span><span class="pln"></span><span style="color: #880000;" class="com">//魔術(shù)引號(hào)處理 ? ? ? ? \'</span><span class="pln"></span><span style="color: #880000;" class="com">//substr ? ? ? ? ? ? ? \ ? ?</span><span class="pln">$sql </span><span style="color: #666600;" class="pun">=</span><span style="color: #008800;" class="str">"SELECT order_id, order_status, shipping_status, pay_status, "</span><span style="color: #666600;" class="pun">.</span><span class="pln">? ?</span><span style="color: #008800;" class="str">" shipping_time, shipping_id, invoice_no, user_id "</span><span style="color: #666600;" class="pun">.</span><span class="pln">? ?</span><span style="color: #008800;" class="str">" FROM "</span><span style="color: #666600;" class="pun">.</span><span class="pln"> $ecs</span><span style="color: #666600;" class="pun">-></span><span class="pln">table</span><span style="color: #666600;" class="pun">(</span><span style="color: #008800;" class="str">'order_info'</span><span style="color: #666600;" class="pun">).</span><span class="pln">? ?</span><span style="color: #008800;" class="str">" WHERE order_sn = '$order_sn' and order_tn='"</span><span style="color: #666600;" class="pun">.</span><span class="pln">$_GET</span><span style="color: #666600;" class="pun">[</span><span style="color: #008800;" class="str">'order_tn'</span><span style="color: #666600;" class="pun">].</span><span style="color: #008800;" class="str">"'"</span><span style="color: #666600;" class="pun">;</span>

提交內(nèi)容：

<span style="color: #666600;" class="pun">?</span><span class="pln">order_sn</span><span style="color: #666600;" class="pun">=</span><span style="color: #008800;" class="str">'&order_tn=%20and%201=1/* </span>

執(zhí)行的SQL語(yǔ)句為：

<span class="pln">SELECT order_id</span><span style="color: #666600;" class="pun">,</span><span class="pln"> order_status</span><span style="color: #666600;" class="pun">,</span><span class="pln"> shipping_status</span><span style="color: #666600;" class="pun">,</span><span class="pln"> pay_status</span><span style="color: #666600;" class="pun">,</span><span class="pln"> shipping_time</span><span style="color: #666600;" class="pun">,</span><span class="pln"> shipping_id</span><span style="color: #666600;" class="pun">,</span><span class="pln"> invoice_no</span><span style="color: #666600;" class="pun">,</span><span class="pln"> user_id FROM order_info WHERE order_sn </span><span style="color: #666600;" class="pun">=</span><span style="color: #008800;" class="str">'\' and order_tn='</span><span style="color: #000088;" class="kwd">and</span><span style="color: #006666;" class="lit">1</span><span style="color: #666600;" class="pun">=</span><span style="color: #006666;" class="lit">1</span><span style="color: #880000;" class="com">/*'</span>

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變量key與魔術(shù)引號(hào)

我們最在這一節(jié)的開頭就提到了變量key，PHP的魔術(shù)引號(hào)對(duì)它有什么影響呢？

<span style="color: #666600;" class="pun"><?</span><span class="pln">php</span><span style="color: #880000;" class="com">//key.php?aaaa'aaa=1&bb'b=2 </span><span class="pln"></span><span style="color: #880000;" class="com">//print_R($_GET); </span><span class="pln">?</span><span style="color: #000088;" class="kwd">foreach</span><span style="color: #666600;" class="pun">(</span><span class="pln">$_GET AS $key </span><span style="color: #666600;" class="pun">=></span><span class="pln"> $value</span><span style="color: #666600;" class="pun">)</span><span class="pln">? ? ? ? </span><span style="color: #666600;" class="pun">{</span><span class="pln">? ? ? ? </span><span style="color: #000088;" class="kwd">print</span><span class="pln"> $key</span><span style="color: #666600;" class="pun">.</span><span style="color: #008800;" class="str">"\n"</span><span style="color: #666600;" class="pun">;</span><span class="pln">? ? ? ? </span><span style="color: #666600;" class="pun">}</span><span class="pln"></span><span style="color: #666600;" class="pun">?></span>

1)當(dāng)magic_quotes_gpc = On時(shí)，在php5.24下測(cè)試顯示：

<span class="pln">aaaa</span><span style="color: #666600;" class="pun">\</span><span style="color: #008800;" class="str">'aaabb\'b</span>

從上面結(jié)果可以看出來(lái)，在設(shè)置了magic_quotes_gpc = On下，變量key受魔術(shù)引號(hào)影響。但是在php4和php<5.2.1的版本中，不處理數(shù)組第一維變量的key，測(cè)試代碼如下：

<span style="color: #666600;" class="pun"><?</span><span class="pln">php</span><span style="color: #880000;" class="com">//key.php?aaaa'aaa[bb']=1 </span><span class="pln">print_R</span><span style="color: #666600;" class="pun">(</span><span class="pln">$_GET</span><span style="color: #666600;" class="pun">);</span><span class="pln"> </span><span style="color: #666600;" class="pun">?></span>

結(jié)果顯示:

<span style="color: #660066;" class="typ">Array</span><span style="color: #666600;" class="pun">(</span><span style="color: #666600;" class="pun">[</span><span class="pln">aaaa</span><span style="color: #008800;" class="str">'aaa] => Array ( [bb\'] => 1 ) ) </span>

數(shù)組第一維變量的key不受魔術(shù)引號(hào)的影響。

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2)當(dāng)magic_quotes_gpc = Off時(shí)，在php5.24下測(cè)試顯示：

<span class="pln">aaaa</span><span style="color: #008800;" class="str">'aaabb'</span><span class="pln">b</span>

對(duì)于magic_quotes_gpc = Off時(shí)所有的變量都是不安全的，考慮到這個(gè)，很多程序都通過(guò)addslashes等函數(shù)來(lái)實(shí)現(xiàn)魔術(shù)引號(hào)對(duì)變量的過(guò)濾，示例代碼如下：

<span style="color: #666600;" class="pun"><?</span><span class="pln">php </span><span style="color: #880000;" class="com">//keyvul.php?aaa'aa=1'</span><span class="pln"></span><span style="color: #880000;" class="com">//magic_quotes_gpc = Off</span><span class="pln">?</span><span style="color: #000088;" class="kwd">if</span><span style="color: #666600;" class="pun">(!</span><span class="pln">get_magic_quotes_gpc</span><span style="color: #666600;" class="pun">())</span><span class="pln"></span><span style="color: #666600;" class="pun">{</span><span class="pln">?$_GET ?</span><span style="color: #666600;" class="pun">=</span><span class="pln"> addslashes_array</span><span style="color: #666600;" class="pun">(</span><span class="pln">$_GET</span><span style="color: #666600;" class="pun">);</span><span class="pln"></span><span style="color: #666600;" class="pun">}</span><span class="pln"></span><span style="color: #000088;" class="kwd">function</span><span class="pln"> addslashes_array</span><span style="color: #666600;" class="pun">(</span><span class="pln">$value</span><span style="color: #666600;" class="pun">)</span><span class="pln"></span><span style="color: #666600;" class="pun">{</span><span class="pln">? ? ? ? </span><span style="color: #000088;" class="kwd">return</span><span class="pln"> is_array</span><span style="color: #666600;" class="pun">(</span><span class="pln">$value</span><span style="color: #666600;" class="pun">)</span><span style="color: #666600;" class="pun">?</span><span class="pln"> array_map</span><span style="color: #666600;" class="pun">(</span><span style="color: #008800;" class="str">'addslashes_array'</span><span style="color: #666600;" class="pun">,</span><span class="pln"> $value</span><span style="color: #666600;" class="pun">)</span><span style="color: #666600;" class="pun">:</span><span class="pln"> addslashes</span><span style="color: #666600;" class="pun">(</span><span class="pln">$value</span><span style="color: #666600;" class="pun">);</span><span class="pln"></span><span style="color: #666600;" class="pun">}</span><span class="pln">print_R</span><span style="color: #666600;" class="pun">(</span><span class="pln">$_GET</span><span style="color: #666600;" class="pun">);</span><span class="pln"></span><span style="color: #000088;" class="kwd">foreach</span><span style="color: #666600;" class="pun">(</span><span class="pln">$_GET AS $key </span><span style="color: #666600;" class="pun">=></span><span class="pln"> $value</span><span style="color: #666600;" class="pun">)</span><span class="pln"></span><span style="color: #666600;" class="pun">{</span><span class="pln">? ? ? ? </span><span style="color: #000088;" class="kwd">print</span><span class="pln"> $key</span><span style="color: #666600;" class="pun">;</span><span class="pln"></span><span style="color: #666600;" class="pun">}</span><span class="pln"></span><span style="color: #666600;" class="pun">?></span>

以上的代碼看上去很完美，但是他這個(gè)代碼里addslashes($value)只處理了變量的具體的值，但是沒有處理變量本身的key，上面的代碼顯示結(jié)果如下：

<span style="color: #660066;" class="typ">Array</span><span class="pln"></span><span style="color: #666600;" class="pun">(</span><span class="pln">? ? </span><span style="color: #666600;" class="pun">[</span><span class="pln">aaa</span><span style="color: #008800;" class="str">'aa] => 1\')aaa'</span><span class="pln">aa</span>

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代碼注射

PHP中可能導(dǎo)致代碼注射的函數(shù)

很多人都知道eval、preg_replace+/e可以執(zhí)行代碼，但是不知道php還有很多的函數(shù)可以執(zhí)行代碼如：

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這里我們看看最近出現(xiàn)的幾個(gè)關(guān)于create_function()代碼執(zhí)行漏洞的代碼：

<span style="color: #666600;" class="pun"></span><span class="pln">php</span><span style="color: #880000;" class="com">//how to exp this code</span><span class="pln">$sort_by</span><span style="color: #666600;" class="pun">=</span><span class="pln">$_GET</span><span style="color: #666600;" class="pun">[</span><span style="color: #008800;" class="str">'sort_by'</span><span style="color: #666600;" class="pun">];</span><span class="pln">$sorter</span><span style="color: #666600;" class="pun">=</span><span style="color: #008800;" class="str">'strnatcasecmp'</span><span style="color: #666600;" class="pun">;</span><span class="pln">$databases</span><span style="color: #666600;" class="pun">=</span><span class="pln">array</span><span style="color: #666600;" class="pun">(</span><span style="color: #008800;" class="str">'test'</span><span style="color: #666600;" class="pun">,</span><span style="color: #008800;" class="str">'test'</span><span style="color: #666600;" class="pun">);</span><span class="pln">$sort_function </span><span style="color: #666600;" class="pun">=</span><span style="color: #008800;" class="str">' ?return 1 * '</span><span style="color: #666600;" class="pun">.</span><span class="pln"> $sorter </span><span style="color: #666600;" class="pun">.</span><span style="color: #008800;" class="str">'($a["'</span><span style="color: #666600;" class="pun">.</span><span class="pln"> $sort_by </span><span style="color: #666600;" class="pun">.</span><span style="color: #008800;" class="str">'"], $b["'</span><span style="color: #666600;" class="pun">.</span><span class="pln"> $sort_by </span><span style="color: #666600;" class="pun">.</span><span style></span>