input_WriteUp(pwnable.kr input) 파일의 입력
6993 단어 PWN
제면
Mom? how can I pass my input to a computer program?
ssh [email protected] -p2222 (pw:guest)
코드
#include
#include
#include
#include
#include
int main(int argc, char* argv[], char* envp[]){
printf("Welcome to pwnable.kr
");
printf("Let's see if you know how to give input to program
");
printf("Just give me correct inputs then you will get the flag :)
");
// argv
if(argc != 100) return 0;
if(strcmp(argv['A'],"\x00")) return 0;
if(strcmp(argv['B'],"\x20\x0a\x0d")) return 0;
printf("Stage 1 clear!
");
// stdio
char buf[4];
read(0, buf, 4);
if(memcmp(buf, "\x00\x0a\x00\xff", 4)) return 0;
read(2, buf, 4);
if(memcmp(buf, "\x00\x0a\x02\xff", 4)) return 0;
printf("Stage 2 clear!
");
// env
if(strcmp("\xca\xfe\xba\xbe", getenv("\xde\xad\xbe\xef"))) return 0;
printf("Stage 3 clear!
");
// file
FILE* fp = fopen("\x0a", "r");
if(!fp) return 0;
if( fread(buf, 4, 1, fp)!=1 ) return 0;
if( memcmp(buf, "\x00\x00\x00\x00", 4) ) return 0;
fclose(fp);
printf("Stage 4 clear!
");
// network
int sd, cd;
struct sockaddr_in saddr, caddr;
sd = socket(AF_INET, SOCK_STREAM, 0);
if(sd == -1){
printf("socket error, tell admin
");
return 0;
}
saddr.sin_family = AF_INET;
saddr.sin_addr.s_addr = INADDR_ANY;
saddr.sin_port = htons( atoi(argv['C']) );
if(bind(sd, (struct sockaddr*)&saddr, sizeof(saddr)) < 0){
printf("bind error, use another port
");
return 1;
}
listen(sd, 1);
int c = sizeof(struct sockaddr_in);
cd = accept(sd, (struct sockaddr *)&caddr, (socklen_t*)&c);
if(cd < 0){
printf("accept error, tell admin
");
return 0;
}
if( recv(cd, buf, 4, 0) != 4 ) return 0;
if(memcmp(buf, "\xde\xad\xbe\xef", 4)) return 0;
printf("Stage 5 clear!
");
// here's your flag
system("/bin/cat flag");
return 0;
}
Mommy! I learned how to pass various input in Linux :)