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#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include "common.h"
#include "crypto.h"
int main(int argc, char **argv, char **envp) {
int fd;
int numbytes;
struct sockaddr_storage their_addr;
byte buf[MAXBUFLEN];
socklen_t addr_len;
/* setup socket, parse cmd line */
{
struct sockaddr_in6 ba;
if (argc > 2) {
fprintf(stderr, "usage: %s [interface]\n", argv[0]);
exit(1);
}
ENP((fd = socket(AF_INET6, SOCK_DGRAM, IPPROTO_UDP)), "listener: socket");
if (argc == 2) {
inet_pton(AF_INET6, "ff02::1", &(ba.sin6_addr));
if ((ba.sin6_scope_id = if_nametoindex(argv[1])) == 0) {
fprintf(stderr, "interface not found\n");
exit(1);
}
}else{
ba.sin6_addr = in6addr_any;
ba.sin6_scope_id = 0;
}
ba.sin6_family = AF_INET6;
ba.sin6_port = htons(SERVERPORT);
ba.sin6_flowinfo = 0;
ENP(bind(fd, (struct sockaddr*) &ba, sizeof ba), "listener: bind");
}
/* daemonize */
#ifndef DEBUG
switch (fork()) {
case 0:
ENP(setsid(), "setsid");
umask(0);
break;
case -1:
perror("fork");
exit(1);
default:
exit(0);
}
#endif
/* receive loop */
addr_len = sizeof their_addr;
while ((numbytes = recvfrom(fd, buf, MAXBUFLEN-1 , 0,
(struct sockaddr *) &their_addr, &addr_len)) != -1) {
/* decode packet */
buf[numbytes] = '\0';
char *task = (char*) buf;
int task_len = strlen(task);
byte *payload = buf + task_len + 1;
int payload_len = numbytes - task_len - 1;
if (task[0] == '/' || strstr(task, "..")) {
fprintf(stderr, "payload tried directory traversal\n");
continue;
}
/* TODO: check if the task exists and is executable; save cpu
cycles trying to decode messages not intended for us */
/* decipher packet */
if (!decipher(task, &payload, &payload_len)) {
fprintf(stderr, "unable to decrypt payload\n");
continue;
}
/* launch handler */
int fd_payload[2];
ENP(pipe(fd_payload), "pipe");
switch (fork()) {
case 0:
/* redirect payload to stdio, leave stdout/err, close the rest */
ENP(dup2(fd_payload[0], 0), "dup");
ENP(close(fd_payload[0]), "close");
ENP(close(fd_payload[1]), "close");
ENP(close(fd), "close");
/* run our task task */
char *cl_argv[2] = {task, NULL};
execve(task, cl_argv, envp);
perror("exec");
exit(1);
case -1:
perror("fork");
exit(1);
}
/* write payload to child process; the return value of write is
intentionally ignored */
if (task_len < numbytes)
IGN(write(fd_payload[1], payload, payload_len))
ENP(close(fd_payload[1]), "close");
ENP(close(fd_payload[0]), "close");
ENP(wait(NULL), "wait");
}
perror("recvfrom");
return 1;
}
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