php中hash比较缺陷
文章目录
哈希算法(Hash Algorithm)又称散列算法、散列函数、哈希函数，哈希算法主要有
MD4、MD5、SHA
php中处理hash时的缺陷
我们比较 hash字符串的时候，常常用到 等于（ == ）、不等于（ != ）来进行比较
一个hash的值如果是以0e开头，并且后面全是数字的话，在php中这种特殊的hash(也就是所谓的Magic Hash)，会被解析为科学计数法0 x 10^n，即和0相等
所以如果两个不同的密码经过哈希以后，其哈希值都是以0e开头的，那么php将会认为他们相同，都是0
此外，0 == 字符会被认为是正确的，可以绕过验证
强弱类型比较
==弱类型比较中，字符'0e123'和字符'0e456'虽然是字符类型，但是因为==比较不比较数据类型，只比较值，结果都是0，所以相等，返回true===强类型比较中，字符'0e123'和字符'0e456'在比较数据类型的时候就被当作字符类型，而字符'0e123'和字符'0e456'当然不相等，所以返回false
这种缺陷在PHP程序中使用哈希算法加密(如md5、md4、SHA1等)进行有关强弱类型比较的地方很容易被用来进行绕过，在CTF题目中算是比较常见的
Magic Hashes
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hash以0e开头
Plaintext MD5 Hash 240610708 0e462097431906509019562988736854 QLTHNDT 0e405967825401955372549139051580 QNKCDZO 0e830400451993494058024219903391 PJNPDWY 0e291529052894702774557631701704 NWWKITQ 0e763082070976038347657360817689 NOOPCJF 0e818888003657176127862245791911 MMHUWUV 0e701732711630150438129209816536 MAUXXQC 0e478478466848439040434801845361 IHKFRNS 0e256160682445802696926137988570 GZECLQZ 0e537612333747236407713628225676 GGHMVOE 0e362766013028313274586933780773 GEGHBXL 0e248776895502908863709684713578 EEIZDOI 0e782601363539291779881938479162 DYAXWCA 0e424759758842488633464374063001 DQWRASX 0e742373665639232907775599582643 BRTKUJZ 00e57640477961333848717747276704 ABJIHVY 0e755264355178451322893275696586 aaaXXAYW 0e540853622400160407992788832284 aabg7XSs 0e087386482136013740957780965295 aabC9RqS 0e041022518165728065344349536299 s878926199a 0e545993274517709034328855841020 s155964671a 0e342768416822451524974117254469 s214587387a 0e848240448830537924465865611904 s214587387a 0e848240448830537924465865611904 0e215962017 0e291242476940776845150308577824 Plaintext MD4 Hash bhhkktQZ 0e949030067204812898914975918567 0e001233333333333334557778889 0e434041524824285414215559233446 0e00000111222333333666788888889 0e641853458593358523155449768529 0001235666666688888888888 0e832225036643258141969031181899 Plaintext SHA1 Hash aaroZmOk 0e66507019969427134894567494305185566735 aaK1STfY 0e76658526655756207688271159624026011393 aaO8zKZF 0e89257456677279068558073954252716165668 aa3OFF9m 0e36977786278517984959260394024281014729 -
hash转换前后相等（等于0）
Plaintext MD5 Hash 0e215962017 0e291242476940776845150308577824 0e1284838308 0e708279691820928818722257405159 0e1137126905 0e291659922323405260514745084877 0e807097110 0e318093639164485566453180786895 0e730083352 0e870635875304277170259950255928 Plaintext MD4 Hash 0e001233333333333334557778889 0e434041524824285414215559233446 0e00000111222333333666788888889 0e641853458593358523155449768529 0001235666666688888888888 0e832225036643258141969031181899 Plaintext SHA1 Hash 0e00000000000000000000081614617300000000 0e65307525940999632287492285468259219070 0e00000000000000000000721902017120000000 0e94981159498252295418182453841140483274 0e01011001101011010001101110101100101000 0e48906523151976751117677463787111106598 0e11001000001010011000100000010001101000 0e63407184960930419027062777705081379452 0e01000001100000001010011011001000000100 0e55962072388397083814346733718698213796 0e10011110000101101000011101011010100100 0e31188585417285828785355336774237712792 0e01010111000111111010101011010111010100 0e45906344569616659428808892091261969181 0e00100001110000001111010000010011101100 0e14860258669052332549568607710438132953 0e11110000111010001001101111111110010010 0e12174258436385758552874426941686538483 0e10111110011100101100010101111010000110 0e99774398282593376043462038572281385389 0e11001111110111110010111010000011110110 0e63185221301034624940345471074357888797 0e00001010010101100100101011101110001110 0e90943988772171749054413593888105986782 0e01011101110010111011110010010010101110 0e01608800192659803576771346607441737826 0e10111110101111001000000100011101101110 0e49094541458479495263034294421025186938 0e11100111101110011010111001010101111110 0e55770706149948760086200713505841887543 0e11111001010101100110011001010001110001 0e91120687121163809515824135435029958137 0e01000111101111110010010010000001001001 0e78071797328546369301825420848872451849 0e00100110100010100110001101110110110101 0e06077380408260614659219920561082767632 0e11111100001011000011110100100010111101 0e12149120354415335220758399492713921588 0e00111100110101101001000101011011111101 0e38661126569790555598431905065403870516 0e10100011100101000001110010100110100011 0e55745078154640212511596259055910278070 0e10011110011111001001100100000111011011 0e20319731123101477913295720812414482217
更多Magic Hashes请参考：https://github.com/spaze/hashes
与hash缺陷无关的数组绕过方法
一般用于强比较
利用的是md5()、md4()、sha1()等在处理非字符数据的时候异常返回，如这里传入数组，返回的是NULL
PS：这里无论===或者==，两边都是NULL
payload: a[]=1&b[]=2
关于MD5强碰撞问题
当php对传参进行了类型控制，那么强比较就不能和上面一样一个数组传参就能解决
例：
需要寻找md5完全相等，本身却不一样的字符
参考：https://crypto.stackexchange.com/questions/1434/are-there-two-known-strings-which-have-the-same-md5-hash-value
file1的十六进制字节流数据
d131dd02c5e6eec4693d9a0698aff95c2fcab58712467eab4004583eb8fb7f8955ad340609f4b30283e488832571415a085125e8f7cdc99fd91dbdf280373c5bd8823e3156348f5bae6dacd436c919c6dd53e2b487da03fd02396306d248cda0e99f33420f577ee8ce54b67080a80d1ec69821bcb6a8839396f9652b6ff72a70
file2的十六进制字节流数据
d131dd02c5e6eec4693d9a0698aff95c2fcab50712467eab4004583eb8fb7f8955ad340609f4b30283e4888325f1415a085125e8f7cdc99fd91dbd7280373c5bd8823e3156348f5bae6dacd436c919c6dd53e23487da03fd02396306d248cda0e99f33420f577ee8ce54b67080280d1ec69821bcb6a8839396f965ab6ff72a70
将字节流写入成文件可以发现这两个不相同的文件它们的md5值完全相等
将十六进制数据解码然后url编码一遍得到：
file1
%D11%DD%02%C5%E6%EE%C4i%3D%9A%06%98%AF%F9%5C/%CA%B5%87%12F~%AB%40%04X%3E%B8%FB%7F%89U%AD4%06%09%F4%B3%02%83%E4%88%83%25qAZ%08Q%25%E8%F7%CD%C9%9F%D9%1D%BD%F2%807%3C%5B%D8%82%3E1V4%8F%5B%AEm%AC%D46%C9%19%C6%DDS%E2%B4%87%DA%03%FD%029c%06%D2H%CD%A0%E9%9F3B%0FW~%E8%CET%B6p%80%A8%0D%1E%C6%98%21%BC%B6%A8%83%93%96%F9e%2Bo%F7%2Ap
file2
%D11%DD%02%C5%E6%EE%C4i%3D%9A%06%98%AF%F9%5C/%CA%B5%07%12F~%AB%40%04X%3E%B8%FB%7F%89U%AD4%06%09%F4%B3%02%83%E4%88%83%25%F1AZ%08Q%25%E8%F7%CD%C9%9F%D9%1D%BDr%807%3C%5B%D8%82%3E1V4%8F%5B%AEm%AC%D46%C9%19%C6%DDS%E24%87%DA%03%FD%029c%06%D2H%CD%A0%E9%9F3B%0FW~%E8%CET%B6p%80%28%0D%1E%C6%98%21%BC%B6%A8%83%93%96%F9e%ABo%F7%2Ap
以上两串字符的md5值都为：79054025255fb1a26e4bc422aef54eb4
构造payload：
param1=%D11%DD%02%C5%E6%EE%C4i%3D%9A%06%98%AF%F9%5C/%CA%B5%87%12F~%AB%40%04X%3E%B8%FB%7F%89U%AD4%06%09%F4%B3%02%83%E4%88%83%25qAZ%08Q%25%E8%F7%CD%C9%9F%D9%1D%BD%F2%807%3C%5B%D8%82%3E1V4%8F%5B%AEm%AC%D46%C9%19%C6%DDS%E2%B4%87%DA%03%FD%029c%06%D2H%CD%A0%E9%9F3B%0FW~%E8%CET%B6p%80%A8%0D%1E%C6%98%21%BC%B6%A8%83%93%96%F9e%2Bo%F7%2Ap¶m2=%D11%DD%02%C5%E6%EE%C4i%3D%9A%06%98%AF%F9%5C/%CA%B5%07%12F~%AB%40%04X%3E%B8%FB%7F%89U%AD4%06%09%F4%B3%02%83%E4%88%83%25%F1AZ%08Q%25%E8%F7%CD%C9%9F%D9%1D%BDr%807%3C%5B%D8%82%3E1V4%8F%5B%AEm%AC%D46%C9%19%C6%DDS%E24%87%DA%03%FD%029c%06%D2H%CD%A0%E9%9F3B%0FW~%E8%CET%B6p%80%28%0D%1E%C6%98%21%BC%B6%A8%83%93%96%F9e%ABo%F7%2Ap
总结部分md5强比较相等字符
%D11%DD%02%C5%E6%EE%C4i%3D%9A%06%98%AF%F9%5C/%CA%B5%87%12F~%AB%40%04X%3E%B8%FB%7F%89U%AD4%06%09%F4%B3%02%83%E4%88%83%25qAZ%08Q%25%E8%F7%CD%C9%9F%D9%1D%BD%F2%807%3C%5B%D8%82%3E1V4%8F%5B%AEm%AC%D46%C9%19%C6%DDS%E2%B4%87%DA%03%FD%029c%06%D2H%CD%A0%E9%9F3B%0FW~%E8%CET%B6p%80%A8%0D%1E%C6%98%21%BC%B6%A8%83%93%96%F9e%2Bo%F7%2Ap
%D11%DD%02%C5%E6%EE%C4i%3D%9A%06%98%AF%F9%5C/%CA%B5%07%12F~%AB%40%04X%3E%B8%FB%7F%89U%AD4%06%09%F4%B3%02%83%E4%88%83%25%F1AZ%08Q%25%E8%F7%CD%C9%9F%D9%1D%BDr%807%3C%5B%D8%82%3E1V4%8F%5B%AEm%AC%D46%C9%19%C6%DDS%E24%87%DA%03%FD%029c%06%D2H%CD%A0%E9%9F3B%0FW~%E8%CET%B6p%80%28%0D%1E%C6%98%21%BC%B6%A8%83%93%96%F9e%ABo%F7%2Ap
以上两串字符的md5值都为：79054025255fb1a26e4bc422aef54eb4
M%C9h%FF%0E%E3%5C%20%95r%D4w%7Br%15%87%D3o%A7%B2%1B%DCV%B7J%3D%C0x%3E%7B%95%18%AF%BF%A2%00%A8%28K%F3n%8EKU%B3_Bu%93%D8Igm%A0%D1U%5D%83%60%FB_%07%FE%A2
M%C9h%FF%0E%E3%5C%20%95r%D4w%7Br%15%87%D3o%A7%B2%1B%DCV%B7J%3D%C0x%3E%7B%95%18%AF%BF%A2%02%A8%28K%F3n%8EKU%B3_Bu%93%D8Igm%A0%D1%D5%5D%83%60%FB_%07%FE%A2
以上两串字符的md5值都为：008ee33a9d58b51cfeb425b0959121c9
%0E0eaU%9A%A7%87%D0%0B%C6%F7%0B%BD%FE4%04%CF%03e%9EpO%854%C0%0F%FBe%9CL%87%40%CC%94/%EB-%A1%15%A3%F4%15%5C%BB%86%07Is%86em%7D%1F4%A4%20Y%D7%8FZ%8D%D1%EF
%0E0eaU%9A%A7%87%D0%0B%C6%F7%0B%BD%FE4%04%CF%03e%9EtO%854%C0%0F%FBe%9CL%87%40%CC%94/%EB-%A1%15%A3%F4%15%DC%BB%86%07Is%86em%7D%1F4%A4%20Y%D7%8FZ%8D%D1%EF
以上两串字符的md5值都为：cee9a457e790cf20d4bdaa6d69f01e41