PHP process the code without decode it

Question

My php hosting injected by unknown code. I don't post the whole file,

$x0d = "b\x61se\x364\137dec\x6f\144\145";

How can the PHP process this line of code without any function to decode.

\x61 = a , what is \x61? how can web server understand this character? I try with HEX / OCT encoding also can't provide me \x61

I give an example inside the code, the below code will execute sha1

$a = "s\x68\x61\061"; 
echo $a("hello");

*The whole file does not have any eval() function inside there.

Community · Accepted Answer · 2017-05-23 10:32:15Z

1

OK. After I referring to this post, I understand it is PHP string type.

Escaped characters in double quote

[0-7]{1,3} : the sequence of characters matching the regular expression is a character in octal notation

\x[0-9A-Fa-f]{1,2} : the sequence of characters matching the regular expression is a character in hexadecimal notation

hexadecimal can refer from here: http://www.ascii.cl/

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answered Aug 23, 2013 at 6:01

Shiro

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