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- /*
- Copyright (C) 2014 nieyong
- This library is free software; you can redistribute it and/or
- modify it under the terms of the GNU Lesser General Public
- License as published by the Free Software Foundation; either
- version 2.1 of the License, or (at your option) any later version.
- This library is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- Lesser General Public License for more details.
- */
- /*
- LD_PRELOAD library to make bind and connect to use a virtual
- IP address as localaddress. Specified via the environment
- variable BIND_ADDR.
- Compile on Linux with:
- gcc -nostartfiles -fpic -shared bindp.c -o libindp.so -ldl -D_GNU_SOURCE
- or just use make be easy:
- make
- Example in bash to make inetd only listen to the localhost
- lo interface, thus disabling remote connections and only
- enable to/from localhost:
- BIND_ADDR="127.0.0.1" BIND_PORT="49888" LD_PRELOAD=./libindp.so curl http://192.168.190.128
- OR:
- BIND_ADDR="127.0.0.1" LD_PRELOAD=./libindp.so curl http://192.168.190.128
- Example in bash to use your virtual IP as your outgoing
- sourceaddress for ircII:
- BIND_ADDR="your-virt-ip" LD_PRELOAD=./bind.so ircII
- Note that you have to set up your servers virtual IP first.
- Add SO_REUSEPORT support within Centos7 or Linux OS with kernel >= 3.9, for the applications with multi-process support just listen one port now
- REUSE_ADDR=1 REUSE_PORT=1 LD_PRELOAD=./libindp.so python server.py &
- REUSE_ADDR=1 REUSE_PORT=1 LD_PRELOAD=./libindp.so java -server -jar your.jar &
- email: nieyong@staff.weibo.com
- web: http://www.blogjava.net/yongboy
- */
- #include <stdio.h>
- #include <stdlib.h>
- #include <sys/types.h>
- #include <sys/socket.h>
- #include <netinet/in.h>
- #include <dlfcn.h>
- #include <errno.h>
- #include <arpa/inet.h>
- int debug_enabled = 1 ;
- int (*real_bind)(int, const struct sockaddr *, socklen_t);
- int (*real_connect)(int, const struct sockaddr *, socklen_t);
- uint32_t bind_addr_saddr = 0;
- struct sockaddr_in local_sockaddr_in[] = { 0 };
- unsigned int bind_port_saddr = 0;
- unsigned int reuse_port = 0;
- unsigned int reuse_addr = 0;
- unsigned int ip_transparent = 0;
- void _init (void) {
- const char *err;
- real_bind = dlsym (RTLD_NEXT, "bind");
- if ((err = dlerror ()) != NULL) {
- fprintf (stderr, "dlsym (bind): %s\n", err);
- }
- real_connect = dlsym (RTLD_NEXT, "connect");
- if ((err = dlerror ()) != NULL) {
- fprintf (stderr, "dlsym (connect): %s\n", err);
- }
- char *bind_addr_env;
- if ((bind_addr_env = getenv ("BIND_ADDR"))) {
- bind_addr_saddr = inet_addr (bind_addr_env);
- local_sockaddr_in->sin_family = AF_INET;
- local_sockaddr_in->sin_addr.s_addr = bind_addr_saddr;
- local_sockaddr_in->sin_port = htons (0);
- }
- char *bind_port_env;
- if ((bind_port_env = getenv ("BIND_PORT"))) {
- bind_port_saddr = atoi(bind_port_env);
- local_sockaddr_in->sin_port = htons (bind_port_saddr);
- }
- char *reuse_addr_env;
- if ((reuse_addr_env = getenv ("REUSE_ADDR"))) {
- reuse_addr = atoi(reuse_addr_env);
- }
- char *reuse_port_env;
- if ((reuse_port_env = getenv ("REUSE_PORT"))) {
- reuse_port = atoi(reuse_port_env);
- }
- char *ip_transparent_env;
- if ((ip_transparent_env = getenv ("IP_TRANSPARENT"))) {
- ip_transparent = atoi(ip_transparent_env);
- }
- }
- unsigned short get_address_family(const struct sockaddr *sk) {
- /*
- As defined in linux/socket.h ,__kernel_sa_family_t is 2 bytes wide.
- We read the first two bytes of sk without using cast to protocol families
- */
- unsigned short _pf = *((unsigned short*) sk);
- return _pf;
- }
- int bind (int fd, const struct sockaddr *sk, socklen_t sl) {
- unsigned short _pf = get_address_family(sk);
- switch (_pf) {
- case AF_INET:
- {
- static struct sockaddr_in *lsk_in;
- lsk_in = (struct sockaddr_in *)sk;
- if (debug_enabled) {
- char original_ip [INET_ADDRSTRLEN];
- inet_ntop(AF_INET,&(lsk_in->sin_addr),original_ip,INET_ADDRSTRLEN);
- int original_port = ntohs(lsk_in->sin_port);
- char *l_bind_addr = getenv ("BIND_ADDR");
- char *l_bind_port = getenv ("BIND_PORT");
- printf("[-] LIB received AF_INET bind request\n");
- if (l_bind_addr && l_bind_port) {
- printf("[-] Changing %s:%d to %s:%s\n" , original_ip,original_port,l_bind_addr,l_bind_port);
- } else if (l_bind_addr) {
- printf("[-] Changing %s to %s\n" , original_ip,l_bind_addr);
- printf("[-] AF_INET: Leaving port unchanged\n");
- } else if (l_bind_port) {
- printf("[-] Changing %d to %s\n" ,original_port,l_bind_port);
- printf("[-] AF_INET: Leaving ip unchanged\n");
- } else {
- printf("[!] AF_INET: Leaving request unchanged\n");
- }
- }
- if (bind_addr_saddr)
- lsk_in->sin_addr.s_addr = bind_addr_saddr;
- if (bind_port_saddr)
- lsk_in->sin_port = htons (bind_port_saddr);
- break;
- }
- case AF_UNIX:
- if (debug_enabled) {
- printf("[-] LIB received AF_UNIX bind request\n");
- printf("[-] AF_UNIX: Leaving request unchanged\n");
- }
- break;
- /*
- Other families handling
- */
- default:
- if (debug_enabled) {
- printf("[!] LIB received unmanaged address family\n");
- }
- break;
- }
- /*
- FIXME: Be careful when using setsockopt
- Is it valid to use these options for AF_UNIX?
- Must be checked
- */
- if (reuse_addr) {
- setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &reuse_addr, sizeof(reuse_addr));
- }
- #ifdef SO_REUSEPORT
- if (reuse_port) {
- setsockopt(fd, SOL_SOCKET, SO_REUSEPORT, &reuse_port, sizeof(reuse_port));
- }
- #endif
- if (ip_transparent) {
- int opt =1;
- setsockopt(fd, SOL_IP, IP_TRANSPARENT, &ip_transparent, sizeof(ip_transparent));
- }
- return real_bind (fd, sk, sl);
- }
- int connect (int fd, const struct sockaddr *sk, socklen_t sl) {
- unsigned short _pf = get_address_family(sk);
- if (_pf == AF_INET) {
- /*
- the default behavior of connect function is that when you
- don't specify BIND_PORT environmental variable it sets port 0 for
- the local socket. OS network stack will choose a randome number
- for the port in this case and also in the case of duplicate port
- numbers for client sockets
- */
- if (debug_enabled) {
- printf("[-] connect(): AF_INET connect() call, binding to local address\n");
- }
- static struct sockaddr_in *rsk_in;
- rsk_in = (struct sockaddr_in *)sk;
- if (bind_addr_saddr || bind_port_saddr) {
- int r = bind (fd, (struct sockaddr *)local_sockaddr_in, sizeof (struct sockaddr));
- }
- return real_connect (fd, sk, sl);
- } else {
- if (debug_enabled) {
- printf("[-] connect(): ignoring to change local address for non AF_INET socket\n");
- }
- return real_connect (fd, sk, sl);
- }
- }
- int main(int argc,char **argv) {
- return 0;
- }
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