Check for errors on socket in send-only listen mode. Fixes #2827

ncat/ncat_listen.c

@@ -131,7 +131,7 @@ static int crlf_state = 0;
 
 static void handle_connection(int socket_accept, int type, fd_set *listen_fds);
 static int read_stdin(struct timeval *qtv);
-static int read_socket(int recv_fd);
+static int read_socket(int recv_fd, ssize_t (*writefunc)(int, const void *, size_t));
 static void post_handle_connection(struct fdinfo *sinfo);
 static void close_fd(struct fdinfo *fdn, int eof);
 static void read_and_broadcast(int recv_socket);
@@ -397,32 +397,26 @@ restart_fd_loop:
             if (checked_fd_isset(cfd, &listen_fds)) {
                 /* we have a new connection request */
                 handle_connection(cfd, type, &listen_fds);
+            } else if (o.broker) {
+                read_and_broadcast(cfd);
             } else if (cfd == STDIN_FILENO) {
-                if (o.broker) {
-                    read_and_broadcast(cfd);
-                } else {
-                    /* Read from stdin and write to all clients. */
-                    rc = read_stdin(&qtv);
-                    if (rc == 0 && (type == SOCK_STREAM || o.ssl)) {
-                        if (!o.noshutdown) shutdown_sockets(SHUT_WR);
-                        if (o.quitafter == 0 && (o.proto != IPPROTO_TCP || (o.proto == IPPROTO_TCP && o.sendonly))) {
-                            /* There will be nothing more to send. If we're not
-                               receiving anything, we can quit here. */
-                            return 0;
-                        }
+                /* Read from stdin and write to all clients. */
+                rc = read_stdin(&qtv);
+                if (rc == 0 && (type == SOCK_STREAM || o.ssl)) {
+                    if (!o.noshutdown) shutdown_sockets(SHUT_WR);
+                    if (o.quitafter == 0 && (o.proto != IPPROTO_TCP || (o.proto == IPPROTO_TCP && o.sendonly))) {
+                        /* There will be nothing more to send. If we're not
+                           receiving anything, we can quit here. */
+                        return 0;
                     }
-                    if (rc < 0)
-                        return 1;
-                }
-            } else if (!o.sendonly) {
-                if (o.broker) {
-                    read_and_broadcast(cfd);
-                } else {
-                    /* Read from a client and write to stdout. */
-                    rc = read_socket(cfd);
-                    if (rc <= 0 && !o.keepopen)
-                        return rc == 0 ? 0 : 1;
                 }
+                if (rc < 0)
+                    return 1;
+            } else {
+                /* Read from a client and write to stdout. */
+                rc = read_socket(cfd, o.sendonly ? Ignore : Write);
+                if (rc <= 0 && !o.keepopen)
+                    return rc == 0 ? 0 : 1;
             }
 
             fds_ready--;
@@ -605,20 +599,18 @@ static void post_handle_connection(struct fdinfo *sinfo)
         /* Now that a client is connected, pay attention to stdin. */
         if (!stdin_eof && !o.recvonly)
             checked_fd_set(STDIN_FILENO, &master_readfds);
-        if (!o.sendonly) {
-            /* add to our lists */
-            checked_fd_set(sinfo->fd, &master_readfds);
-            /* add it to our list of fds for maintaining maxfd */
+        /* add to our lists */
+        checked_fd_set(sinfo->fd, &master_readfds);
+        /* add it to our list of fds for maintaining maxfd */
 #ifdef HAVE_OPENSSL
-            /* Don't add it twice (see handle_connection above) */
-            if (!o.ssl) {
+        /* Don't add it twice (see handle_connection above) */
+        if (!o.ssl) {
 #endif
-            if (add_fdinfo(&client_fdlist, sinfo) < 0)
-                bye("add_fdinfo() failed.");
+          if (add_fdinfo(&client_fdlist, sinfo) < 0)
+            bye("add_fdinfo() failed.");
 #ifdef HAVE_OPENSSL
-            }
-#endif
         }
+#endif
         checked_fd_set(sinfo->fd, &master_broadcastfds);
         if (add_fdinfo(&broadcast_fdlist, sinfo) < 0)
             bye("add_fdinfo() failed.");
@@ -703,7 +695,7 @@ int read_stdin(struct timeval *qtv)
 
 /* Read from a client socket and write to stdout. Return the number of bytes
    read from the socket, or -1 on error. */
-int read_socket(int recv_fd)
+int read_socket(int recv_fd, ssize_t (*writefunc)(int, const void *, size_t))
 {
     char buf[DEFAULT_TCP_BUF_LEN];
     struct fdinfo *fdn;
@@ -728,7 +720,7 @@ int read_socket(int recv_fd)
             return n;
         }
         else {
-            Write(STDOUT_FILENO, buf, n);
+            writefunc(STDOUT_FILENO, buf, n);
             nbytes += n;
         }
     } while (pending);
@@ -795,6 +787,10 @@ static void read_and_broadcast(int recv_fd)
                 close_fd(fdn, n == 0);
                 return;
             }
+            /* Ignore any read data in sendonly mode */
+            if (o.sendonly) {
+              continue;
+            }
         }
 
         if (o.debug > 1)

ncat/sys_wrap.c

@@ -189,3 +189,15 @@ ssize_t Write(int fd, const void *buf, size_t count)
 
     return ret;
 }
+
+#ifndef UNUSED
+#define UNUSED(x) ((void) x)
+#endif
+/* Like Write, but does nothing. */
+ssize_t Ignore(int fd, const void *buf, size_t count)
+{
+  UNUSED(fd);
+  UNUSED(buf);
+  UNUSED(count);
+  return 0;
+}

ncat/sys_wrap.h

@@ -108,5 +108,6 @@ sighandler_t Signal(int signum, sighandler_t handler);
 int Socket(int domain, int type, int protocol);
 char *Strdup(const char *s);
 ssize_t Write(int fd, const void *buf, size_t count);
+ssize_t Ignore(int fd, const void *buf, size_t count);
 
 #endif