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/*
* Copyright (c) 2020 Darren Tucker <dtucker@openbsd.org>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include "includes.h"
#include <sys/socket.h>
#include <sys/types.h>
#include <limits.h>
#include <netdb.h>
#include <stdio.h>
#include <string.h>
#include "addr.h"
#include "canohost.h"
#include "log.h"
#include "misc.h"
#include "srclimit.h"
#include "xmalloc.h"
static int max_children, max_persource, ipv4_masklen, ipv6_masklen;
/* Per connection state, used to enforce unauthenticated connection limit. */
static struct child_info {
int id;
struct xaddr addr;
} *child;
void
srclimit_init(int max, int persource, int ipv4len, int ipv6len)
{
int i;
max_children = max;
ipv4_masklen = ipv4len;
ipv6_masklen = ipv6len;
max_persource = persource;
if (max_persource == INT_MAX) /* no limit */
return;
debug("%s: max connections %d, per source %d, masks %d,%d", __func__,
max, persource, ipv4len, ipv6len);
if (max <= 0)
fatal("%s: invalid number of sockets: %d", __func__, max);
child = xcalloc(max_children, sizeof(*child));
for (i = 0; i < max_children; i++)
child[i].id = -1;
}
/* returns 1 if connection allowed, 0 if not allowed. */
int
srclimit_check_allow(int sock, int id)
{
struct xaddr xa, xb, xmask;
struct sockaddr_storage addr;
socklen_t addrlen = sizeof(addr);
struct sockaddr *sa = (struct sockaddr *)&addr;
int i, bits, first_unused, count = 0;
char xas[NI_MAXHOST];
if (max_persource == INT_MAX) /* no limit */
return 1;
debug("%s: sock %d id %d limit %d", __func__, sock, id, max_persource);
if (getpeername(sock, sa, &addrlen) != 0)
return 1; /* not remote socket? */
if (addr_sa_to_xaddr(sa, addrlen, &xa) != 0)
return 1; /* unknown address family? */
/* Mask address off address to desired size. */
bits = xa.af == AF_INET ? ipv4_masklen : ipv6_masklen;
if (addr_netmask(xa.af, bits, &xmask) != 0 ||
addr_and(&xb, &xa, &xmask) != 0) {
debug3("%s: invalid mask %d bits", __func__, bits);
return 1;
}
first_unused = max_children;
/* Count matching entries and find first unused one. */
for (i = 0; i < max_children; i++) {
if (child[i].id == -1) {
if (i < first_unused)
first_unused = i;
} else if (addr_cmp(&child[i].addr, &xb) == 0) {
count++;
}
}
if (addr_ntop(&xa, xas, sizeof(xas)) != 0) {
debug3("%s: addr ntop failed", __func__);
return 1;
}
debug3("%s: new unauthenticated connection from %s/%d, at %d of %d",
__func__, xas, bits, count, max_persource);
if (first_unused == max_children) { /* no free slot found */
debug3("%s: no free slot", __func__);
return 0;
}
if (first_unused < 0 || first_unused >= max_children)
fatal("%s: internal error: first_unused out of range",
__func__);
if (count >= max_persource)
return 0;
/* Connection allowed, store masked address. */
child[first_unused].id = id;
memcpy(&child[first_unused].addr, &xb, sizeof(xb));
return 1;
}
void
srclimit_done(int id)
{
int i;
if (max_persource == INT_MAX) /* no limit */
return;
debug("%s: id %d", __func__, id);
/* Clear corresponding state entry. */
for (i = 0; i < max_children; i++) {
if (child[i].id == id) {
child[i].id = -1;
return;
}
}
}
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