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Implement a new IP option (not compiled/enabled by default) to allow

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applications to specify a non-local IP address when bind()'ing a socket
to a local endpoint.

This allows applications to spoof the client IP address of connections
if (obviously!) they somehow are able to receive the traffic normally
destined to said clients.

This patch doesn't include any changes to ipfw or the bridging code to
redirect the client traffic through the PCB checks so TCP gets a shot
at it. The normal behaviour is that packets with a non-local destination
IP address are not handled locally. This can be dealth with some IPFW hackery;
modifications to IPFW to make this less hacky will occur in subsequent
commmits.

Thanks to Julian Elischer and others at Ironport. This work was approved
and donated before Cisco acquired them.

Obtained from:	Julian Elischer and others
MFC after:	2 weeks
This commit is contained in:
Adrian Chadd 2009-01-09 16:02:19 +00:00
parent b9a2c48954
commit be9347e3fe
6 changed files with 37 additions and 1 deletions
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8
sys/conf/NOTES
View File

@ -633,6 +633,14 @@ options ALTQ_PRIQ # Priority Queueing
options ALTQ_NOPCC # Required if the TSC is unusable
options ALTQ_DEBUG
# IP optional behaviour.
# IP_NONLOCALBIND disables the check that bind() usually makes that the
# Address is one that is assigned to an interface on this machine.
# It allows transparent proxies to pretend to be other machines.
# How the packet GET to that machine is a problem solved elsewhere,
# smart routers, ipfw fwd, etc.
options IP_NONLOCALBIND #Allow impersonation for proxies.
# netgraph(4). Enable the base netgraph code with the NETGRAPH option.
# Individual node types can be enabled with the corresponding option
# listed below; however, this is not strictly necessary as netgraph

1
sys/conf/options
View File

@ -392,6 +392,7 @@ IPFIREWALL_VERBOSE opt_ipfw.h
IPFIREWALL_VERBOSE_LIMIT opt_ipfw.h
IPSEC opt_ipsec.h
IPSEC_DEBUG opt_ipsec.h
IP_NONLOCALBIND opt_inet.h
IPSEC_FILTERTUNNEL opt_ipsec.h
IPSTEALTH
IPX

1
sys/netinet/in.h
View File

@ -441,6 +441,7 @@ __END_DECLS
#define IP_FAITH 22 /* bool; accept FAITH'ed connections */
#define IP_ONESBCAST 23 /* bool: send all-ones broadcast */
#define IP_NONLOCALOK 24 /* allow bind to spoof other machines */
#define IP_FW_TABLE_ADD 40 /* add entry */
#define IP_FW_TABLE_DEL 41 /* delete entry */

7
sys/netinet/in_pcb.c
View File

@ -35,6 +35,7 @@
__FBSDID("$FreeBSD$");
#include "opt_ddb.h"
#include "opt_inet.h"
#include "opt_ipsec.h"
#include "opt_inet6.h"
#include "opt_mac.h"
@ -346,7 +347,11 @@ in_pcbbind_setup(struct inpcb *inp, struct sockaddr *nam, in_addr_t *laddrp,
} else if (sin->sin_addr.s_addr != INADDR_ANY) {
sin->sin_port = 0; /* yech... */
bzero(&sin->sin_zero, sizeof(sin->sin_zero));
if (ifa_ifwithaddr((struct sockaddr *)sin) == 0)
if (
#if defined(IP_NONLOCALBIND)
((inp->inp_flags & INP_NONLOCALOK) == 0) &&
#endif
(ifa_ifwithaddr((struct sockaddr *)sin) == 0))
return (EADDRNOTAVAIL);
}
laddr = sin->sin_addr;

2
sys/netinet/in_pcb.h
View File

@ -411,6 +411,8 @@ void inp_4tuple_get(struct inpcb *inp, uint32_t *laddr, uint16_t *lp,
#define INP_FAITH 0x200 /* accept FAITH'ed connections */
#define INP_RECVTTL 0x400 /* receive incoming IP TTL */
#define INP_DONTFRAG 0x800 /* don't fragment packet */
#define INP_NONLOCALOK 0x1000 /* Allow bind to spoof any address */
/* - requires options IP_NONLOCALBIND */
#define IN6P_IPV6_V6ONLY 0x008000 /* restrict AF_INET6 socket for v6 */

19
sys/netinet/ip_output.c
View File

@ -33,6 +33,7 @@
__FBSDID("$FreeBSD$");
#include "opt_ipfw.h"
#include "opt_inet.h"
#include "opt_ipsec.h"
#include "opt_mac.h"
#include "opt_mbuf_stress_test.h"
@ -95,6 +96,12 @@ SYSCTL_INT(_net_inet_ip, OID_AUTO, mbuf_frag_size, CTLFLAG_RW,
&mbuf_frag_size, 0, "Fragment outgoing mbufs to this size");
#endif
#if defined(IP_NONLOCALBIND)
static int ip_nonlocalok = 0;
SYSCTL_INT(_net_inet_ip, OID_AUTO, nonlocalok,
CTLFLAG_RW|CTLFLAG_SECURE, &ip_nonlocalok, 0, "");
#endif
static void ip_mloopback
(struct ifnet *, struct mbuf *, struct sockaddr_in *, int);
@ -866,6 +873,13 @@ ip_ctloutput(struct socket *so, struct sockopt *sopt)
return (error);
}
#if defined(IP_NONLOCALBIND)
case IP_NONLOCALOK:
if (! ip_nonlocalok) {
error = ENOPROTOOPT;
break;
}
#endif
case IP_TOS:
case IP_TTL:
case IP_MINTTL:
@ -937,6 +951,11 @@ ip_ctloutput(struct socket *so, struct sockopt *sopt)
case IP_DONTFRAG:
OPTSET(INP_DONTFRAG);
break;
#if defined(IP_NONLOCALBIND)
case IP_NONLOCALOK:
OPTSET(INP_NONLOCALOK);
break;
#endif
}
break;
#undef OPTSET