1 files changed, 119 insertions, 0 deletions
diff --git a/src/listener.c b/src/listener.c
new file mode 100644
index 0000000..c0d81ef
--- /dev/null
+++ b/src/listener.c
@@ -0,0 +1,119 @@
+/*
+** listener.c -- a datagram sockets "server" demo
+*/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <netdb.h>
+
+#include "common.h"
+
+// get sockaddr, IPv4 or IPv6:
+void *get_in_addr(struct sockaddr *sa)
+{
+    if (sa->sa_family == AF_INET) {
+        return &(((struct sockaddr_in*)sa)->sin_addr);
+    }
+
+    return &(((struct sockaddr_in6*)sa)->sin6_addr);
+}
+
+int main(int argc, char *argv[], char *envp[])
+{
+    int sockfd;
+    struct addrinfo hints, *servinfo, *p;
+    int rv;
+    int numbytes;
+    struct sockaddr_storage their_addr;
+    char buf[MAXBUFLEN];
+    socklen_t addr_len;
+    char s[INET6_ADDRSTRLEN];
+
+    memset(&hints, 0, sizeof hints);
+    hints.ai_family = AF_UNSPEC; // set to AF_INET to force IPv4
+    hints.ai_socktype = SOCK_DGRAM;
+    hints.ai_flags = AI_PASSIVE; // use my IP
+
+    if ((rv = getaddrinfo(NULL, SERVERPORT_S, &hints, &servinfo)) != 0) {
+        fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
+        return 1;
+    }
+
+    // loop through all the results and bind to the first we can
+    for(p = servinfo; p != NULL; p = p->ai_next) {
+        if ((sockfd = socket(p->ai_family, p->ai_socktype,
+                p->ai_protocol)) == -1) {
+            perror("listener: socket");
+            continue;
+        }
+
+        if (bind(sockfd, p->ai_addr, p->ai_addrlen) == -1) {
+            close(sockfd);
+            perror("listener: bind");
+            continue;
+        }
+
+        break;
+    }
+
+    if (p == NULL) {
+        fprintf(stderr, "listener: failed to bind socket\n");
+        return 2;
+    }
+
+    freeaddrinfo(servinfo);
+
+    // daemonize
+#ifndef DEBUG
+    switch (fork()) {
+    case 0:
+      setsid();
+      umask(0);
+      break;
+    case -1:
+      perror("fork (serious!)");
+      exit(-1);
+    default:
+      exit(0);
+    }
+#endif
+
+    // receive loop
+    addr_len = sizeof their_addr;
+    while ((numbytes = recvfrom(sockfd, buf, MAXBUFLEN-1 , 0,
+           (struct sockaddr *)&their_addr, &addr_len)) != -1) {
+      // decode packet & launch handler
+      buf[numbytes] = '\0';
+      char *task = buf,
+	*cl_argv[3] = {task, (strlen(task)<numbytes) ? (buf+strlen(task)+1) : NULL, NULL };
+
+      if (task[0] == '/' || strstr(task, "..")) {
+	fprintf(stderr, "payload tried directory traversal\n");
+	continue;
+      }
+
+      switch (fork()) {
+      case 0:
+	close(sockfd); // close socket handler, leave std io
+	execve(task, cl_argv, envp);
+	perror("exec");
+	exit(-1);
+      case -1:
+	perror("fork (serious!)");
+	exit(-1);
+      default:
+	wait();
+      }
+    }
+
+    perror("recvfrom");
+
+    return -1;
+}