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arp(8): use getifaddrs(3) instead of ioctl(SIOCGIFCONF)

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The original code had used a fixed-size buffer for ioctl(SIOCGIFCONF),
that might cause the target ifreq spilled from the buffer.  Use the handy
getifaddrs(3) to fix the problem.

Reviewed by:		glebius
Differential revision:	https://reviews.freebsd.org/D35536
This commit is contained in:
KUROSAWA Takahiro 2022-07-04 20:56:29 -07:00 committed by Gleb Smirnoff
parent ec32fc2af5
commit d80d734937
1 changed files with 26 additions and 45 deletions
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71
usr.sbin/arp/arp.c
View file

@ -79,6 +79,7 @@ __FBSDID("$FreeBSD$");
#include <string.h>
#include <strings.h>
#include <unistd.h>
#include <ifaddrs.h>
#include <libxo/xo.h>
typedef void (action_fn)(struct sockaddr_dl *sdl, struct sockaddr_in *s_in,
@ -794,90 +795,70 @@ rtmsg(int cmd, struct sockaddr_in *dst, struct sockaddr_dl *sdl)
* get_ether_addr - get the hardware address of an interface on the
* the same subnet as ipaddr.
*/
#define MAX_IFS 32
static int
get_ether_addr(in_addr_t ipaddr, struct ether_addr *hwaddr)
{
struct ifreq *ifr, *ifend, *ifp;
struct ifaddrs *ifa, *ifd, *ifas = NULL;
in_addr_t ina, mask;
struct sockaddr_dl *dla;
struct ifreq ifreq;
struct ifconf ifc;
struct ifreq ifs[MAX_IFS];
int sock;
int retval = 0;
sock = socket(AF_INET, SOCK_DGRAM, 0);
if (sock < 0)
xo_err(1, "socket");
ifc.ifc_len = sizeof(ifs);
ifc.ifc_req = ifs;
if (ioctl(sock, SIOCGIFCONF, &ifc) < 0) {
xo_warnx("ioctl(SIOCGIFCONF)");
goto done;
}
#define NEXTIFR(i) \
((struct ifreq *)((char *)&(i)->ifr_addr \
+ MAX((i)->ifr_addr.sa_len, sizeof((i)->ifr_addr))) )
/*
* Scan through looking for an interface with an Internet
* address on the same subnet as `ipaddr'.
*/
ifend = (struct ifreq *)(ifc.ifc_buf + ifc.ifc_len);
for (ifr = ifc.ifc_req; ifr < ifend; ifr = NEXTIFR(ifr) ) {
if (ifr->ifr_addr.sa_family != AF_INET)
if (getifaddrs(&ifas) < 0) {
xo_warnx("getifaddrs");
goto done;
}
for (ifa = ifas; ifa != NULL; ifa = ifa->ifa_next) {
if (ifa->ifa_addr == NULL || ifa->ifa_netmask == NULL)
continue;
if (ifa->ifa_addr->sa_family != AF_INET)
continue;
strncpy(ifreq.ifr_name, ifr->ifr_name,
sizeof(ifreq.ifr_name));
ifreq.ifr_addr = ifr->ifr_addr;
/*
* Check that the interface is up,
* and not point-to-point or loopback.
*/
if (ioctl(sock, SIOCGIFFLAGS, &ifreq) < 0)
continue;
if ((ifreq.ifr_flags &
if ((ifa->ifa_flags &
(IFF_UP|IFF_BROADCAST|IFF_POINTOPOINT|
IFF_LOOPBACK|IFF_NOARP)) != (IFF_UP|IFF_BROADCAST))
continue;
/* Get its netmask and check that it's on the right subnet. */
if (ioctl(sock, SIOCGIFNETMASK, &ifreq) < 0)
continue;
mask = ((struct sockaddr_in *)
&ifreq.ifr_addr)->sin_addr.s_addr;
ifa->ifa_netmask)->sin_addr.s_addr;
ina = ((struct sockaddr_in *)
&ifr->ifr_addr)->sin_addr.s_addr;
ifa->ifa_addr)->sin_addr.s_addr;
if ((ipaddr & mask) == (ina & mask))
break; /* ok, we got it! */
}
if (ifr >= ifend)
if (ifa == NULL)
goto done;
/*
* Now scan through again looking for a link-level address
* for this interface.
*/
ifp = ifr;
for (ifr = ifc.ifc_req; ifr < ifend; ifr = NEXTIFR(ifr))
if (strcmp(ifp->ifr_name, ifr->ifr_name) == 0 &&
ifr->ifr_addr.sa_family == AF_LINK)
for (ifd = ifas; ifd != NULL; ifd = ifd->ifa_next) {
if (ifd->ifa_addr == NULL)
continue;
if (strcmp(ifa->ifa_name, ifd->ifa_name) == 0 &&
ifd->ifa_addr->sa_family == AF_LINK)
break;
if (ifr >= ifend)
}
if (ifd == NULL)
goto done;
/*
* Found the link-level address - copy it out
*/
dla = (struct sockaddr_dl *) &ifr->ifr_addr;
dla = (struct sockaddr_dl *)ifd->ifa_addr;
memcpy(hwaddr, LLADDR(dla), dla->sdl_alen);
printf("using interface %s for proxy with address %s\n", ifp->ifr_name,
printf("using interface %s for proxy with address %s\n", ifa->ifa_name,
ether_ntoa(hwaddr));
retval = dla->sdl_alen;
done:
close(sock);
if (ifas != NULL)
freeifaddrs(ifas);
return (retval);
}