commit c9e091aceaded2d2f82674609d060036ace9d22e
Author: Tobias Girstmair <t-nmap () girst at>
Date:   Sun Feb 7 15:49:21 2021 +0100

    Ncat: match traditional and OpenBSD netcat behaviour of terminating on EOF
    
    Also implements a switch for backwards compatibility with the previous
    behaviour, --no-terminate. Previously discussed at
    https://seclists.org/nmap-dev/2017/q2/94
    
    Fixes #1779, #894 and #1413.

diff --git a/ncat/docs/ncat.xml b/ncat/docs/ncat.xml
index 653ae36a2..39c4d587b 100644
--- a/ncat/docs/ncat.xml
+++ b/ncat/docs/ncat.xml
@@ -874,6 +874,19 @@
         </listitem>
       </varlistentry>
 
+      <varlistentry>
+        <term>
+          <option>--no-terminate</option> (Do not terminate on stdin/socket EOF)
+          <indexterm><primary><option>--no-terminate</option> (Ncat option)</primary></indexterm>
+        </term>
+        <listitem>
+          <para>If this option is passed, Ncat will not terminate when EOF is
+          seen on the socket or stdin when connected over TCP. This used to be
+          the default in Ncat in the past, and is provided for
+          backwards-compatibility.</para>
+        </listitem>
+      </varlistentry>
+
       <varlistentry>
         <term>
           <option>-n</option>,
diff --git a/ncat/ncat_connect.c b/ncat/ncat_connect.c
index f59dd4372..dffec9a91 100644
--- a/ncat/ncat_connect.c
+++ b/ncat/ncat_connect.c
@@ -1274,8 +1274,8 @@ static void read_stdin_handler(nsock_pool nsp, nsock_event evt, void *data)
     if (status == NSE_STATUS_EOF) {
         if (!o.noshutdown)
             shutdown(nsock_iod_get_sd(cs.sock_nsi), SHUT_WR);
-        /* In --send-only mode or non-TCP mode, exit after EOF on stdin. */
-        if (o.proto != IPPROTO_TCP || (o.proto == IPPROTO_TCP && o.sendonly))
+        /* Unless --no-terminate is specified, exit after EOF on stdin. */
+        if (o.proto != IPPROTO_TCP || !o.noterminate)
             nsock_loop_quit(nsp);
         return;
     } else if (status == NSE_STATUS_ERROR) {
@@ -1325,8 +1325,8 @@ static void read_socket_handler(nsock_pool nsp, nsock_event evt, void *data)
 #else
         Close(STDOUT_FILENO);
 #endif
-        /* In --recv-only mode or non-TCP mode, exit after EOF on the socket. */
-        if (o.proto != IPPROTO_TCP || (o.proto == IPPROTO_TCP && o.recvonly))
+        /* Unless --no-terminate is specified, exit after EOF on the socket. */
+        if (o.proto != IPPROTO_TCP || !o.noterminate)
             nsock_loop_quit(nsp);
         return;
     } else if (status == NSE_STATUS_ERROR) {
diff --git a/ncat/ncat_core.c b/ncat/ncat_core.c
index 7c39e5d36..d5e5d7d68 100644
--- a/ncat/ncat_core.c
+++ b/ncat/ncat_core.c
@@ -107,6 +107,7 @@ void options_init(void)
     o.sendonly = 0;
     o.recvonly = 0;
     o.noshutdown = 0;
+    o.noterminate = 0;
     o.telnet = 0;
     o.linedelay = 0;
     o.chat = 0;
diff --git a/ncat/ncat_core.h b/ncat/ncat_core.h
index f03813dc5..9bd751264 100644
--- a/ncat/ncat_core.h
+++ b/ncat/ncat_core.h
@@ -111,6 +111,7 @@ struct options {
     int sendonly;
     int recvonly;
     int noshutdown;
+    int noterminate;
     int telnet;
     int linedelay;
     int chat;
diff --git a/ncat/ncat_main.c b/ncat/ncat_main.c
index 2792a6ac2..d49398f5f 100644
--- a/ncat/ncat_main.c
+++ b/ncat/ncat_main.c
@@ -263,6 +263,7 @@ int main(int argc, char *argv[])
         {"source",          required_argument,  NULL,         's'},
         {"send-only",       no_argument,        &o.sendonly,  1},
         {"no-shutdown",     no_argument,        &o.noshutdown,1},
+        {"no-terminate",    no_argument,        &o.noterminate,1},
         {"broker",          no_argument,        NULL,         0},
         {"chat",            no_argument,        NULL,         0},
         {"talk",            no_argument,        NULL,         0},
@@ -615,6 +616,7 @@ int main(int argc, char *argv[])
 "      --send-only            Only send data, ignoring received; quit on EOF\n"
 "      --recv-only            Only receive data, never send anything\n"
 "      --no-shutdown          Continue half-duplex when receiving EOF on stdin\n"
+"      --no-terminate         Do not exit when EOF is received on socket/stdin\n"
 "      --allow                Allow only given hosts to connect to Ncat\n"
 "      --allowfile            A file of hosts allowed to connect to Ncat\n"
 "      --deny                 Deny given hosts from connecting to Ncat\n"