Testing desockmulti on server

[Filarna]

hello zyingp i have question on how desockmulti works
i write vulnerable server for testing desockmulti

 #include <netinet/in.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/socket.h>
 #include <unistd.h>
 #define PORT 8080
 int main(int argc, char const* argv[])
 {
	int server_fd, new_socket, valread;
	struct sockaddr_in address;
	int opt = 1;
	int addrlen = sizeof(address);
	char buffer[30] = { 0 };
	char* hello = "Hello from server";
	

        // Creating socket file descriptor
	if ((server_fd = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
		perror("socket failed");
		exit(EXIT_FAILURE);
	}

	// Forcefully attaching socket to the port 8080
	if (setsockopt(server_fd, SOL_SOCKET,
				SO_REUSEADDR | SO_REUSEPORT, &opt,
				sizeof(opt))) {
		perror("setsockopt");
		exit(EXIT_FAILURE);
	}
	address.sin_family = AF_INET;
	address.sin_addr.s_addr = INADDR_ANY;
	address.sin_port = htons(PORT);

	// Forcefully attaching socket to the port 8080
	if (bind(server_fd, (struct sockaddr*)&address,
			sizeof(address))
		< 0) {
		perror("bind failed");
		exit(EXIT_FAILURE);
	}
	if (listen(server_fd, 3) < 0) {
		perror("listen");
		exit(EXIT_FAILURE);
	}
	if ((new_socket
		= accept(server_fd, (struct sockaddr*)&address,
				(socklen_t*)&addrlen))
		< 0) {
		perror("accept");
		exit(EXIT_FAILURE);
	}
	valread = read(new_socket, buffer, 1024);
	printf("%s\n", buffer);
	send(new_socket, hello, strlen(hello), 0);
	printf("Hello message sent\n");

	// closing the connected socket
	close(new_socket);
	// closing the listening socket
	shutdown(server_fd, SHUT_RDWR);
	return 0;
}

and than i use afl to fuzz this program
but regarding of my buffer[30] or my input i cant get any error form this
i even test
USE_RAW_FORMAT=1 LD_PRELOAD=./desockmulti-master/desockmulti.so ss/server in/base_test.txt
to directly give input to sever but seems like its not working
Sorry for some newbie question and thanks for your time

[zyingp]

You can direct start your server to test whether it works. When I ran your code and the following error shows:

$ ./server
bind failed: Address already in use

Then I change the port to other uncommon port number like #define PORT 8040, after that, it seems both the server and desockmulti work as expected.

[Filarna]

I finally make it work but afl give me odd output .
As intentionally give buffer[30] length to get buffer overflow but surprisingly i get 1 saved crash and almost all other input of afl result in crash but not saved.
than when i saw saved crash it wasn't about overflow related errors at all despite that i where looking for something like this
"//////////////////////////////////////////////////////////////////////////////////////////////////////"
in that saved crash.
so I want to make sure you get same result and i config afl and desockmulti in right way.(if you can send me your saved crash it would be awesome)
and what your opinion about this subject ?

[zyingp]

I suggest you use AddressSanitizer (ASan) to build the program, either use it to re-run the crash input, or use ASan+AFL to instrument the program at the same time and use the instrumented program to fuzz directly.