Topics address http://pwnable.kr/play.php
The first question FD
Environment is kali system
First, open the topic
Follow the prompts to connect ssh password for the guest
View the contents of the documents found flag file, but does not have read permission
View fd.c code file
Review function appears
int argc parameters to be entered
char * argv [] indicates the parameters including the filename, the file name is argv [0]
char * envp [] is an environment variable, such as path = c: \ windows or something like that. It is not an integer which is count [i] == NULL is represented by the end of the last evnp
atoi () ; atoi () function string str scan parameters, skip over whitespace characters (e.g., space, tab indents, () function detected by isspace becomes), or until the number meets the sign began do the conversion, but then encountered the end of the non-numeric or string ( '\ 0') before the end of the conversion, and returns the results.
read (a, b, c) ; stdio function a is 0 there are three types of standard input standard output when a read error reading output 2, b and c is a variable number of bytes
Example: read (0, buf, 32) is the input to the 32 bytes buf 'in
strcmp (a, b) comparing the value of ab if a == b returns 0 a> b returns a positive number a <b returns a negative
The goal is to achieve: system ( "/ bin / cat flag")
First argc can not <2 otherwise directly out of the
Analysis of the code must first meet strcmp ( "LETMEWIN \ n", buf) == 0;
fd = 0 then the input LETMEWIN \ n
I.e., argv [1] == 0x1234 = 4660
Get flag
