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| | 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;
@@ -945,6 +949,8 @@ unix_bind(char *path, int flags)
0)) < 0)
return -1;
+ unlink(path);
+
memset(&s_un, 0, sizeof(struct sockaddr_un));
s_un.sun_family = AF_UNIX;
@@ -1070,8 +1076,10 @@ unix_connect(char *path)
if ((s = unix_bind(unix_dg_tmp_socket, SOCK_CLOEXEC)) < 0)
return -1;
} else {
- if ((s = socket(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0)) < 0)
+ if ((s = socket(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0)) < 0) {
+ errx(1, "create unix socket failed");
return -1;
+ }
}
memset(&s_un, 0, sizeof(struct sockaddr_un));
@@ -1081,10 +1089,12 @@ 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)) < 0) {
save_errno = errno;
+ warn("unix connect failed");
close(s);
errno = save_errno;
return -1;
|