From: Aron Xu <aron@debian.org>
Date: Mon, 13 Feb 2012 19:06:52 +0800
Subject: misc failures and features

---
 Makefile |    3 ++-
 nc.1     |   51 +++++++++++++++++++++++++++++++++++++++++++++++++++
 netcat.c |   14 ++++++++++++--
 3 files changed, 65 insertions(+), 3 deletions(-)

--- a/Makefile
+++ b/Makefile
@@ -3,7 +3,8 @@
 PROG=	nc
 SRCS=	netcat.c atomicio.c socks.c
 
-LIBS=  `pkg-config --libs libbsd` -lresolv
+PKG_CONFIG ?= pkg-config
+LIBS=  `$(PKG_CONFIG) --libs libbsd` -lresolv
 OBJS=  $(SRCS:.c=.o)
 CFLAGS=  -g -O2
 LDFLAGS=  -Wl,--no-add-needed
--- a/nc.1
+++ b/nc.1
@@ -365,6 +365,54 @@ and which side is being used as a
 The connection may be terminated using an
 .Dv EOF
 .Pq Sq ^D .
+.Pp
+There is no
+.Fl c
+or
+.Fl e
+option in this netcat, but you still can execute a command after connection
+being established by redirecting file descriptors. Be cautious here because
+opening a port and let anyone connected execute arbitrary command on your
+site is DANGEROUS. If you really need to do this, here is an example:
+.Pp
+On
+.Sq server
+side:
+.Pp
+.Dl $ rm -f /tmp/f; mkfifo /tmp/f
+.Dl $ cat /tmp/f | /bin/sh -i 2>&1 | nc -l 127.0.0.1 1234 > /tmp/f
+.Pp
+On
+.Sq client
+side:
+.Pp
+.Dl $ nc host.example.com 1234
+.Dl $ (shell prompt from host.example.com)
+.Pp
+By doing this, you create a fifo at /tmp/f and make nc listen at port 1234
+of address 127.0.0.1 on
+.Sq server
+side, when a
+.Sq client
+establishes a connection successfully to that port, /bin/sh gets executed
+on
+.Sq server
+side and the shell prompt is given to
+.Sq client
+side.
+.Pp
+When connection is terminated,
+.Nm
+quits as well. Use
+.Fl k
+if you want it keep listening, but if the command quits this option won't
+restart it or keep
+.Nm
+running. Also don't forget to remove the file descriptor once you don't need
+it anymore:
+.Pp
+.Dl $ rm -f /tmp/f
+.Pp
 .Sh DATA TRANSFER
 The example in the previous section can be expanded to build a
 basic data transfer model.
@@ -517,6 +565,9 @@ Original implementation by
 .br
 Rewritten with IPv6 support by
 .An Eric Jackson Aq Mt ericj@monkey.org .
+.br
+Modified for Debian port by Aron Xu
+.Aq aron@debian.org .
 .Sh CAVEATS
 UDP port scans using the
 .Fl uz
--- a/netcat.c
+++ b/netcat.c
@@ -98,6 +98,7 @@
 #include <netdb.h>
 #include <poll.h>
 #include <signal.h>
+#include <stddef.h>
 #include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -246,7 +247,10 @@ main(int argc, char *argv[])
 	struct addrinfo hints;
 	struct servent *sv;
 	socklen_t len;
-	struct sockaddr_storage cliaddr;
+	union {
+		struct sockaddr_storage storage;
+		struct sockaddr_un forunix;
+	} cliaddr;
 	char *proxy = NULL, *proxyport = NULL;
 	const char *errstr;
 	struct addrinfo proxyhints;
@@ -948,6 +952,8 @@ unix_bind(char *path, int flags)
 	    0)) == -1)
 		return -1;
 
+	unlink(path);
+
 	memset(&s_un, 0, sizeof(struct sockaddr_un));
 	s_un.sun_family = AF_UNIX;
 
@@ -1073,8 +1079,10 @@ unix_connect(char *path)
 		if ((s = unix_bind(unix_dg_tmp_socket, SOCK_CLOEXEC)) == -1)
 			return -1;
 	} else {
-		if ((s = socket(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0)) == -1)
+		if ((s = socket(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0)) == -1) {
+			errx(1, "create unix socket failed");
 			return -1;
+		}
 	}
 
 	memset(&s_un, 0, sizeof(struct sockaddr_un));
@@ -1084,10 +1092,12 @@ unix_connect(char *path)
 	    sizeof(s_un.sun_path)) {
 		close(s);
 		errno = ENAMETOOLONG;
+		warn("unix connect abandoned");
 		return -1;
 	}
 	if (connect(s, (struct sockaddr *)&s_un, sizeof(s_un)) == -1) {
 		save_errno = errno;
+		warn("unix connect failed");
 		close(s);
 		errno = save_errno;
 		return -1;