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Fix widespread off-by-one error dealing with port numbers

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Port numbers (for both TCP and UDP) are 16-bit, and so fit exactly into a
'short'.  USHRT_MAX is therefore the maximum port number and this is widely
used in the code.  Unfortunately, a lot of those places don't actually
want the maximum port number (USHRT_MAX == 65535), they want the total
number of ports (65536).  This leads to a number of potentially nasty
consequences:

 * We have buffer overruns on the port_fwd::delta array if we try to use
   port 65535
 * We have similar potential overruns for the tcp_sock_* arrays
 * Interestingly udp_act had the correct size, but we can calculate it in
   a more direct manner
 * We have a logical overrun of the ports bitmap as well, although it will
   just use an unused bit in the last byte so isnt harmful
 * Many loops don't consider port 65535 (which does mitigate some but not
   all of the buffer overruns above)
 * In udp_invert_portmap() we incorrectly compute the reverse port
   translation for return packets

Correct all these by using a new NUM_PORTS defined explicitly for this
purpose.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
This commit is contained in:
David Gibson 2022-09-24 19:08:22 +10:00 committed by Stefano Brivio
parent 3ede07aac9
commit d5b80ccc72
5 changed files with 19 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
conf.c
View File

@ -209,7 +209,7 @@ static int conf_ports(const struct ctx *c, char optname, const char *optarg,
if (sep == p)
break;
if (port > USHRT_MAX || errno)
if (port >= NUM_PORTS || errno)
goto bad;
switch (*sep) {
@ -276,7 +276,7 @@ static int conf_ports(const struct ctx *c, char optname, const char *optarg,
if (sep == p)
break;
if (port > USHRT_MAX || errno)
if (port >= NUM_PORTS || errno)
goto bad;
/* -p 22

7
port_fwd.h
View File

@ -7,6 +7,9 @@
#ifndef PORT_FWD_H
#define PORT_FWD_H
/* Number of ports for both TCP and UDP */
#define NUM_PORTS (1U << 16)
enum port_fwd_mode {
FWD_SPEC = 1,
FWD_NONE,
@ -14,7 +17,7 @@ enum port_fwd_mode {
FWD_ALL,
};
#define PORT_BITMAP_SIZE DIV_ROUND_UP(USHRT_MAX, 8)
#define PORT_BITMAP_SIZE DIV_ROUND_UP(NUM_PORTS, 8)
/**
* port_fwd - Describes port forwarding for one protocol and direction
@ -25,7 +28,7 @@ enum port_fwd_mode {
struct port_fwd {
enum port_fwd_mode mode;
uint8_t map[PORT_BITMAP_SIZE];
in_port_t delta[USHRT_MAX];
in_port_t delta[NUM_PORTS];
};
#endif /* PORT_FWD_H */

12
tcp.c
View File

@ -547,9 +547,9 @@ static const char *tcp_flag_str[] __attribute((__unused__)) = {
};
/* Listening sockets, used for automatic port forwarding in pasta mode only */
static int tcp_sock_init_lo [USHRT_MAX][IP_VERSIONS];
static int tcp_sock_init_ext [USHRT_MAX][IP_VERSIONS];
static int tcp_sock_ns [USHRT_MAX][IP_VERSIONS];
static int tcp_sock_init_lo [NUM_PORTS][IP_VERSIONS];
static int tcp_sock_init_ext [NUM_PORTS][IP_VERSIONS];
static int tcp_sock_ns [NUM_PORTS][IP_VERSIONS];
/* Table of destinations with very low RTT (assumed to be local), LRU */
static struct in6_addr low_rtt_dst[LOW_RTT_TABLE_SIZE];
@ -3186,7 +3186,7 @@ static int tcp_sock_init_ns(void *arg)
ns_enter(c);
for (port = 0; port < USHRT_MAX; port++) {
for (port = 0; port < NUM_PORTS; port++) {
if (!bitmap_isset(c->tcp.fwd_out.map, port))
continue;
@ -3386,7 +3386,7 @@ static int tcp_port_rebind(void *arg)
if (a->bind_in_ns) {
ns_enter(a->c);
for (port = 0; port < USHRT_MAX; port++) {
for (port = 0; port < NUM_PORTS; port++) {
if (!bitmap_isset(a->c->tcp.fwd_out.map, port)) {
if (tcp_sock_ns[port][V4] >= 0) {
close(tcp_sock_ns[port][V4]);
@ -3410,7 +3410,7 @@ static int tcp_port_rebind(void *arg)
tcp_sock_init(a->c, 1, AF_UNSPEC, NULL, port);
}
} else {
for (port = 0; port < USHRT_MAX; port++) {
for (port = 0; port < NUM_PORTS; port++) {
if (!bitmap_isset(a->c->tcp.fwd_in.map, port)) {
if (tcp_sock_init_ext[port][V4] >= 0) {
close(tcp_sock_init_ext[port][V4]);

10
udp.c
View File

@ -164,8 +164,8 @@ struct udp_splice_port {
};
/* Port tracking, arrays indexed by packet source port (host order) */
static struct udp_tap_port udp_tap_map [IP_VERSIONS][USHRT_MAX];
static struct udp_splice_port udp_splice_map [IP_VERSIONS][USHRT_MAX];
static struct udp_tap_port udp_tap_map [IP_VERSIONS][NUM_PORTS];
static struct udp_splice_port udp_splice_map [IP_VERSIONS][NUM_PORTS];
enum udp_act_type {
UDP_ACT_TAP,
@ -175,7 +175,7 @@ enum udp_act_type {
};
/* Activity-based aging for bindings */
static uint8_t udp_act[IP_VERSIONS][UDP_ACT_TYPE_MAX][(USHRT_MAX + 1) / 8];
static uint8_t udp_act[IP_VERSIONS][UDP_ACT_TYPE_MAX][DIV_ROUND_UP(NUM_PORTS, 8)];
/* Static buffers */
@ -271,7 +271,7 @@ static void udp_invert_portmap(struct udp_port_fwd *fwd)
in_port_t delta = fwd->f.delta[i];
if (delta)
fwd->rdelta[(in_port_t)i + delta] = USHRT_MAX - delta;
fwd->rdelta[(in_port_t)i + delta] = NUM_PORTS - delta;
}
}
@ -1198,7 +1198,7 @@ int udp_sock_init_ns(void *arg)
if (ns_enter(c))
return 0;
for (dst = 0; dst < USHRT_MAX; dst++) {
for (dst = 0; dst < NUM_PORTS; dst++) {
if (!bitmap_isset(c->udp.fwd_out.f.map, dst))
continue;

2
udp.h
View File

@ -50,7 +50,7 @@ union udp_epoll_ref {
*/
struct udp_port_fwd {
struct port_fwd f;
in_port_t rdelta[USHRT_MAX];
in_port_t rdelta[NUM_PORTS];
};
/**