upstream: split PerSourcePenalties address tracking. Previously it

used one shared table and overflow policy for IPv4 and IPv6 addresses, now it
will use separate tables and optionally different overflow policies.

This prevents misbehaviour from IPv6 addresses (which are vastly easier
to obtain many of) from affecting IPv4 connections and may allow for
stricter overflow policies.

ok deraadt@

OpenBSD-Commit-ID: 12637ed0aa4d5f1f3e702da42ea967cbd8bfdfd9
This commit is contained in:
djm@openbsd.org 2024-06-12 22:36:00 +00:00 committed by Damien Miller
parent 06ab4c6931
commit 4de80ff4e6
No known key found for this signature in database
4 changed files with 165 additions and 75 deletions

View File

@ -1,4 +1,4 @@
/* $OpenBSD: servconf.c,v 1.410 2024/06/11 00:36:20 djm Exp $ */
/* $OpenBSD: servconf.c,v 1.411 2024/06/12 22:36:00 djm Exp $ */
/*
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
* All rights reserved
@ -165,8 +165,10 @@ initialize_server_options(ServerOptions *options)
options->per_source_masklen_ipv6 = -1;
options->per_source_penalty_exempt = NULL;
options->per_source_penalty.enabled = -1;
options->per_source_penalty.max_sources = -1;
options->per_source_penalty.max_sources4 = -1;
options->per_source_penalty.max_sources6 = -1;
options->per_source_penalty.overflow_mode = -1;
options->per_source_penalty.overflow_mode6 = -1;
options->per_source_penalty.penalty_crash = -1;
options->per_source_penalty.penalty_authfail = -1;
options->per_source_penalty.penalty_noauth = -1;
@ -414,10 +416,14 @@ fill_default_server_options(ServerOptions *options)
options->per_source_masklen_ipv6 = 128;
if (options->per_source_penalty.enabled == -1)
options->per_source_penalty.enabled = 1;
if (options->per_source_penalty.max_sources == -1)
options->per_source_penalty.max_sources = 65536;
if (options->per_source_penalty.max_sources4 == -1)
options->per_source_penalty.max_sources4 = 65536;
if (options->per_source_penalty.max_sources6 == -1)
options->per_source_penalty.max_sources6 = 65536;
if (options->per_source_penalty.overflow_mode == -1)
options->per_source_penalty.overflow_mode = PER_SOURCE_PENALTY_OVERFLOW_PERMISSIVE;
if (options->per_source_penalty.overflow_mode6 == -1)
options->per_source_penalty.overflow_mode6 = options->per_source_penalty.overflow_mode;
if (options->per_source_penalty.penalty_crash == -1)
options->per_source_penalty.penalty_crash = 90;
if (options->per_source_penalty.penalty_grace == -1)
@ -2028,9 +2034,14 @@ process_server_config_line_depth(ServerOptions *options, char *line,
} else if (strncmp(arg, "min:", 4) == 0) {
p = arg + 4;
intptr = &options->per_source_penalty.penalty_min;
} else if (strncmp(arg, "max-sources:", 12) == 0) {
intptr = &options->per_source_penalty.max_sources;
if ((errstr = atoi_err(arg+12, &value)) != NULL)
} else if (strncmp(arg, "max-sources4:", 13) == 0) {
intptr = &options->per_source_penalty.max_sources4;
if ((errstr = atoi_err(arg+13, &value)) != NULL)
fatal("%s line %d: %s value %s.",
filename, linenum, keyword, errstr);
} else if (strncmp(arg, "max-sources6:", 13) == 0) {
intptr = &options->per_source_penalty.max_sources6;
if ((errstr = atoi_err(arg+13, &value)) != NULL)
fatal("%s line %d: %s value %s.",
filename, linenum, keyword, errstr);
} else if (strcmp(arg, "overflow:deny-all") == 0) {
@ -2039,6 +2050,12 @@ process_server_config_line_depth(ServerOptions *options, char *line,
} else if (strcmp(arg, "overflow:permissive") == 0) {
intptr = &options->per_source_penalty.overflow_mode;
value = PER_SOURCE_PENALTY_OVERFLOW_PERMISSIVE;
} else if (strcmp(arg, "overflow6:deny-all") == 0) {
intptr = &options->per_source_penalty.overflow_mode6;
value = PER_SOURCE_PENALTY_OVERFLOW_DENY_ALL;
} else if (strcmp(arg, "overflow6:permissive") == 0) {
intptr = &options->per_source_penalty.overflow_mode6;
value = PER_SOURCE_PENALTY_OVERFLOW_PERMISSIVE;
} else {
fatal("%s line %d: unsupported %s keyword %s",
filename, linenum, keyword, arg);
@ -3288,16 +3305,21 @@ dump_config(ServerOptions *o)
if (o->per_source_penalty.enabled) {
printf("persourcepenalties crash:%d authfail:%d noauth:%d "
"grace-exceeded:%d max:%d min:%d max-sources:%d "
"overflow:%s\n", o->per_source_penalty.penalty_crash,
"grace-exceeded:%d max:%d min:%d max-sources4:%d "
"max-sources6:%d overflow:%s overflow6:%s\n",
o->per_source_penalty.penalty_crash,
o->per_source_penalty.penalty_authfail,
o->per_source_penalty.penalty_noauth,
o->per_source_penalty.penalty_grace,
o->per_source_penalty.penalty_max,
o->per_source_penalty.penalty_min,
o->per_source_penalty.max_sources,
o->per_source_penalty.max_sources4,
o->per_source_penalty.max_sources6,
o->per_source_penalty.overflow_mode ==
PER_SOURCE_PENALTY_OVERFLOW_DENY_ALL ?
"deny-all" : "permissive",
o->per_source_penalty.overflow_mode6 ==
PER_SOURCE_PENALTY_OVERFLOW_DENY_ALL ?
"deny-all" : "permissive");
} else
printf("persourcepenalties no\n");

View File

@ -1,4 +1,4 @@
/* $OpenBSD: servconf.h,v 1.164 2024/06/06 17:15:25 djm Exp $ */
/* $OpenBSD: servconf.h,v 1.165 2024/06/12 22:36:00 djm Exp $ */
/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
@ -69,8 +69,10 @@ struct listenaddr {
#define PER_SOURCE_PENALTY_OVERFLOW_PERMISSIVE 2
struct per_source_penalty {
int enabled;
int max_sources;
int max_sources4;
int max_sources6;
int overflow_mode;
int overflow_mode6;
int penalty_crash;
int penalty_grace;
int penalty_authfail;

View File

@ -61,11 +61,11 @@ struct penalty {
};
static int penalty_addr_cmp(struct penalty *a, struct penalty *b);
static int penalty_expiry_cmp(struct penalty *a, struct penalty *b);
RB_HEAD(penalties_by_addr, penalty) penalties_by_addr;
RB_HEAD(penalties_by_expiry, penalty) penalties_by_expiry;
RB_HEAD(penalties_by_addr, penalty) penalties_by_addr4, penalties_by_addr6;
RB_HEAD(penalties_by_expiry, penalty) penalties_by_expiry4, penalties_by_expiry6;
RB_GENERATE_STATIC(penalties_by_addr, penalty, by_addr, penalty_addr_cmp)
RB_GENERATE_STATIC(penalties_by_expiry, penalty, by_expiry, penalty_expiry_cmp)
static size_t npenalties;
static size_t npenalties4, npenalties6;
static int
srclimit_mask_addr(const struct xaddr *addr, int bits, struct xaddr *masked)
@ -106,10 +106,14 @@ srclimit_init(int max, int persource, int ipv4len, int ipv6len,
ipv6_masklen = ipv6len;
max_persource = persource;
penalty_cfg = *penalty_conf;
if (penalty_cfg.max_sources4 < 0 || penalty_cfg.max_sources6 < 0)
fatal_f("invalid max_sources"); /* shouldn't happen */
penalty_exempt = penalty_exempt_conf == NULL ?
NULL : xstrdup(penalty_exempt_conf);
RB_INIT(&penalties_by_addr);
RB_INIT(&penalties_by_expiry);
RB_INIT(&penalties_by_addr4);
RB_INIT(&penalties_by_expiry4);
RB_INIT(&penalties_by_addr6);
RB_INIT(&penalties_by_expiry6);
if (max_persource == INT_MAX) /* no limit */
return;
debug("%s: max connections %d, per source %d, masks %d,%d", __func__,
@ -208,26 +212,36 @@ penalty_expiry_cmp(struct penalty *a, struct penalty *b)
}
static void
expire_penalties(time_t now)
expire_penalties_from_tree(time_t now, const char *t,
struct penalties_by_expiry *by_expiry,
struct penalties_by_addr *by_addr, size_t *npenaltiesp)
{
struct penalty *penalty, *tmp;
/* XXX avoid full scan of tree, e.g. min-heap */
RB_FOREACH_SAFE(penalty, penalties_by_expiry,
&penalties_by_expiry, tmp) {
RB_FOREACH_SAFE(penalty, penalties_by_expiry, by_expiry, tmp) {
if (penalty->expiry >= now)
break;
if (RB_REMOVE(penalties_by_expiry, &penalties_by_expiry,
if (RB_REMOVE(penalties_by_expiry, by_expiry,
penalty) != penalty ||
RB_REMOVE(penalties_by_addr, &penalties_by_addr,
RB_REMOVE(penalties_by_addr, by_addr,
penalty) != penalty)
fatal_f("internal error: penalty tables corrupt");
fatal_f("internal error: %s penalty table corrupt", t);
free(penalty);
if (npenalties-- == 0)
fatal_f("internal error: npenalties underflow");
if ((*npenaltiesp)-- == 0)
fatal_f("internal error: %s npenalties underflow", t);
}
}
static void
expire_penalties(time_t now)
{
expire_penalties_from_tree(now, "ipv4",
&penalties_by_expiry4, &penalties_by_addr4, &npenalties4);
expire_penalties_from_tree(now, "ipv6",
&penalties_by_expiry6, &penalties_by_addr6, &npenalties6);
}
static void
addr_masklen_ntop(struct xaddr *addr, int masklen, char *s, size_t slen)
{
@ -247,8 +261,10 @@ srclimit_penalty_check_allow(int sock, const char **reason)
struct xaddr addr;
struct penalty find, *penalty;
time_t now;
int bits;
int bits, max_sources, overflow_mode;
char addr_s[NI_MAXHOST];
struct penalties_by_addr *by_addr;
size_t npenalties;
if (!penalty_cfg.enabled)
return 1;
@ -261,8 +277,17 @@ srclimit_penalty_check_allow(int sock, const char **reason)
return 1;
}
}
if (npenalties >= (size_t)penalty_cfg.max_sources &&
penalty_cfg.overflow_mode == PER_SOURCE_PENALTY_OVERFLOW_DENY_ALL) {
now = monotime();
expire_penalties(now);
by_addr = addr.af == AF_INET ?
&penalties_by_addr4 : &penalties_by_addr6;
max_sources = addr.af == AF_INET ?
penalty_cfg.max_sources4 : penalty_cfg.max_sources6;
overflow_mode = addr.af == AF_INET ?
penalty_cfg.overflow_mode : penalty_cfg.overflow_mode6;
npenalties = addr.af == AF_INET ? npenalties4 : npenalties6;
if (npenalties >= (size_t)max_sources &&
overflow_mode == PER_SOURCE_PENALTY_OVERFLOW_DENY_ALL) {
*reason = "too many penalised addresses";
return 0;
}
@ -270,9 +295,7 @@ srclimit_penalty_check_allow(int sock, const char **reason)
memset(&find, 0, sizeof(find));
if (srclimit_mask_addr(&addr, bits, &find.addr) != 0)
return 1;
now = monotime();
if ((penalty = RB_FIND(penalties_by_addr,
&penalties_by_addr, &find)) == NULL)
if ((penalty = RB_FIND(penalties_by_addr, by_addr, &find)) == NULL)
return 1; /* no penalty */
if (penalty->expiry < now) {
expire_penalties(now);
@ -285,38 +308,52 @@ srclimit_penalty_check_allow(int sock, const char **reason)
}
static void
srclimit_remove_expired_penalties(void)
srclimit_early_expire_penalties_from_tree(const char *t,
struct penalties_by_expiry *by_expiry,
struct penalties_by_addr *by_addr, size_t *npenaltiesp, size_t max_sources)
{
struct penalty *p = NULL;
int bits;
char s[NI_MAXHOST + 4];
/* Delete the soonest-to-expire penalties. */
while (npenalties > (size_t)penalty_cfg.max_sources) {
if ((p = RB_MIN(penalties_by_expiry,
&penalties_by_expiry)) == NULL)
fatal_f("internal error: penalty tables corrupt (find)");
while (*npenaltiesp > max_sources) {
if ((p = RB_MIN(penalties_by_expiry, by_expiry)) == NULL)
fatal_f("internal error: %s table corrupt (find)", t);
bits = p->addr.af == AF_INET ? ipv4_masklen : ipv6_masklen;
addr_masklen_ntop(&p->addr, bits, s, sizeof(s));
debug3_f("overflow, remove %s", s);
if (RB_REMOVE(penalties_by_expiry,
&penalties_by_expiry, p) != p ||
RB_REMOVE(penalties_by_addr, &penalties_by_addr, p) != p)
fatal_f("internal error: penalty tables corrupt (remove)");
debug3_f("%s overflow, remove %s", t, s);
if (RB_REMOVE(penalties_by_expiry, by_expiry, p) != p ||
RB_REMOVE(penalties_by_addr, by_addr, p) != p)
fatal_f("internal error: %s table corrupt (remove)", t);
free(p);
npenalties--;
(*npenaltiesp)--;
}
}
static void
srclimit_early_expire_penalties(void)
{
srclimit_early_expire_penalties_from_tree("ipv4",
&penalties_by_expiry4, &penalties_by_addr4, &npenalties4,
(size_t)penalty_cfg.max_sources4);
srclimit_early_expire_penalties_from_tree("ipv6",
&penalties_by_expiry6, &penalties_by_addr6, &npenalties6,
(size_t)penalty_cfg.max_sources6);
}
void
srclimit_penalise(struct xaddr *addr, int penalty_type)
{
struct xaddr masked;
struct penalty *penalty, *existing;
struct penalty *penalty = NULL, *existing = NULL;
time_t now;
int bits, penalty_secs;
int bits, penalty_secs, max_sources = 0, overflow_mode;
char addrnetmask[NI_MAXHOST + 4];
const char *reason = NULL;
const char *reason = NULL, *t;
size_t *npenaltiesp = NULL;
struct penalties_by_addr *by_addr = NULL;
struct penalties_by_expiry *by_expiry = NULL;
if (!penalty_cfg.enabled)
return;
@ -358,9 +395,19 @@ srclimit_penalise(struct xaddr *addr, int penalty_type)
now = monotime();
expire_penalties(now);
if (npenalties > (size_t)penalty_cfg.max_sources &&
penalty_cfg.overflow_mode == PER_SOURCE_PENALTY_OVERFLOW_DENY_ALL) {
verbose_f("penalty table full, cannot penalise %s for %s",
by_expiry = addr->af == AF_INET ?
&penalties_by_expiry4 : &penalties_by_expiry6;
by_addr = addr->af == AF_INET ?
&penalties_by_addr4 : &penalties_by_addr6;
max_sources = addr->af == AF_INET ?
penalty_cfg.max_sources4 : penalty_cfg.max_sources6;
overflow_mode = addr->af == AF_INET ?
penalty_cfg.overflow_mode : penalty_cfg.overflow_mode6;
npenaltiesp = addr->af == AF_INET ? &npenalties4 : &npenalties6;
t = addr->af == AF_INET ? "ipv4" : "ipv6";
if (*npenaltiesp > (size_t)max_sources &&
overflow_mode == PER_SOURCE_PENALTY_OVERFLOW_DENY_ALL) {
verbose_f("%s penalty table full, cannot penalise %s for %s", t,
addrnetmask, reason);
return;
}
@ -369,48 +416,48 @@ srclimit_penalise(struct xaddr *addr, int penalty_type)
penalty->addr = masked;
penalty->expiry = now + penalty_secs;
penalty->reason = reason;
if ((existing = RB_INSERT(penalties_by_addr, &penalties_by_addr,
if ((existing = RB_INSERT(penalties_by_addr, by_addr,
penalty)) == NULL) {
/* penalty didn't previously exist */
if (penalty_secs > penalty_cfg.penalty_min)
penalty->active = 1;
if (RB_INSERT(penalties_by_expiry, &penalties_by_expiry,
penalty) != NULL)
fatal_f("internal error: penalty tables corrupt");
verbose_f("%s: new %s penalty of %d seconds for %s",
if (RB_INSERT(penalties_by_expiry, by_expiry, penalty) != NULL)
fatal_f("internal error: %s penalty tables corrupt", t);
verbose_f("%s: new %s %s penalty of %d seconds for %s", t,
addrnetmask, penalty->active ? "active" : "deferred",
penalty_secs, reason);
if (++npenalties > (size_t)penalty_cfg.max_sources)
srclimit_remove_expired_penalties(); /* permissive */
if (++(*npenaltiesp) > (size_t)max_sources)
srclimit_early_expire_penalties(); /* permissive */
return;
}
debug_f("%s penalty for %s already exists, %lld seconds remaining",
existing->active ? "active" : "inactive",
debug_f("%s penalty for %s %s already exists, %lld seconds remaining",
existing->active ? "active" : "inactive", t,
addrnetmask, (long long)(existing->expiry - now));
/* Expiry information is about to change, remove from tree */
if (RB_REMOVE(penalties_by_expiry, &penalties_by_expiry,
existing) != existing)
fatal_f("internal error: penalty tables corrupt (remove)");
if (RB_REMOVE(penalties_by_expiry, by_expiry, existing) != existing)
fatal_f("internal error: %s penalty table corrupt (remove)", t);
/* An entry already existed. Accumulate penalty up to maximum */
existing->expiry += penalty_secs;
if (existing->expiry - now > penalty_cfg.penalty_max)
existing->expiry = now + penalty_cfg.penalty_max;
if (existing->expiry - now > penalty_cfg.penalty_min &&
!existing->active) {
verbose_f("%s: activating penalty of %lld seconds for %s",
addrnetmask, (long long)(existing->expiry - now), reason);
verbose_f("%s: activating %s penalty of %lld seconds for %s",
addrnetmask, t, (long long)(existing->expiry - now),
reason);
existing->active = 1;
}
existing->reason = penalty->reason;
free(penalty);
penalty = NULL;
/* Re-insert into expiry tree */
if (RB_INSERT(penalties_by_expiry, &penalties_by_expiry,
existing) != NULL)
fatal_f("internal error: penalty tables corrupt (insert)");
if (RB_INSERT(penalties_by_expiry, by_expiry, existing) != NULL)
fatal_f("internal error: %s penalty table corrupt (insert)", t);
}
void
srclimit_penalty_info(void)
static void
srclimit_penalty_info_for_tree(const char *t,
struct penalties_by_expiry *by_expiry, size_t npenalties)
{
struct penalty *p = NULL;
int bits;
@ -418,8 +465,8 @@ srclimit_penalty_info(void)
time_t now;
now = monotime();
logit("%zu active penalties", npenalties);
RB_FOREACH(p, penalties_by_expiry, &penalties_by_expiry) {
logit("%zu active %s penalties", npenalties, t);
RB_FOREACH(p, penalties_by_expiry, by_expiry) {
bits = p->addr.af == AF_INET ? ipv4_masklen : ipv6_masklen;
addr_masklen_ntop(&p->addr, bits, s, sizeof(s));
if (p->expiry < now)
@ -430,3 +477,12 @@ srclimit_penalty_info(void)
}
}
}
void
srclimit_penalty_info(void)
{
srclimit_penalty_info_for_tree("ipv4",
&penalties_by_expiry4, npenalties4);
srclimit_penalty_info_for_tree("ipv6",
&penalties_by_expiry6, npenalties6);
}

View File

@ -33,8 +33,8 @@
.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
.\" $OpenBSD: sshd_config.5,v 1.360 2024/06/11 05:24:39 jmc Exp $
.Dd $Mdocdate: June 11 2024 $
.\" $OpenBSD: sshd_config.5,v 1.361 2024/06/12 22:36:00 djm Exp $
.Dd $Mdocdate: June 12 2024 $
.Dt SSHD_CONFIG 5
.Os
.Sh NAME
@ -1603,12 +1603,14 @@ Repeated penalties will accumulate up to this maximum.
.It Cm min:duration
Specifies the minimum penalty that must accrue before enforcement begins
(default: 15s).
.It Cm max-sources:number
Specifies the maximum number of penalise client address ranges to track
(default: 65536).
.It Cm max-sources4:number max-sources6:number
Specifies the maximum number of client IPv4 and IPv6 address ranges to
track for penalties (default: 65536 for both).
.It Cm overflow:mode
Controls how the server behaves when
.Cm max-sources
.Cm max-sources4
or
.Cm max-sources6
is exceeded.
There are two operating modes:
.Cm deny-all ,
@ -1618,6 +1620,14 @@ until a penalty expires, and
.Cm permissive ,
which allows new connections by removing existing penalties early
(default: permissive).
Note that client penalties below the
.Cm min
threshold count against the total number of tracked penalties.
IPv4 and IPv6 addresses are tracked separately, so an overflow in one will
not affect the other.
.It Cm overflow6:mode
Allows specifying a different overflow mode for IPv6 addresses.
The default it to use the same overflow mode as was specified for IPv4.
.El
.It Cm PerSourcePenaltyExemptList
Specifies a comma-separated list of addresses to exempt from penalties.