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From 7ea36eeece56b59f98e469934e4c20b4da043346 Mon Sep 17 00:00:00 2001
From: Doran Moppert <dmoppert@redhat.com>
Date: Thu, 11 May 2017 11:42:54 -0400
Subject: [PATCH] rpcbind: pair all svc_getargs() calls with svc_freeargs() to
avoid memory leak
This patch is to address CVE-2017-8779 "rpcbomb" in rpcbind, discussed
at [1], [2], [3]. The last link suggests this issue is actually a bug
in rpcbind, which led me here.
The leak caused by the reproducer at [4] appears to come from
rpcb_service_4(), in the case where svc_getargs() returns false and the
function had an early return, rather than passing through the cleanup
path at done:, as would otherwise occur.
It also addresses a couple of other locations where the same fault seems
to exist, though I haven't been able to exercise those. I hope someone
more intimate with rpc(3) can confirm my understanding is correct, and
that I haven't introduced any new bugs.
Without this patch, using the reproducer (and variants) repeatedly
against rpcbind with a numBytes argument of 1_000_000_000, /proc/$(pidof
rpcbind)/status reports VmSize increase of 976564 kB each call, and
VmRSS increase of around 260 kB every 33 calls - the specific numbers
are probably an artifact of my rhel/glibc version. With the patch,
there is a small (~50 kB) VmSize increase with the first message, but
thereafter both VmSize and VmRSS remain steady.
[1]: http://seclists.org/oss-sec/2017/q2/209
[2]: https://bugzilla.redhat.com/show_bug.cgi?id=1448124
[3]: https://sourceware.org/ml/libc-alpha/2017-05/msg00129.html
[4]: https://github.com/guidovranken/rpcbomb/
Signed-off-by: Doran Moppert <dmoppert@redhat.com>
Signed-off-by: Steve Dickson <steved@redhat.com>
---
src/pmap_svc.c | 56 +++++++++++++++++++++++++++++++++++++++++++++---------
src/rpcb_svc.c | 2 +-
src/rpcb_svc_4.c | 2 +-
src/rpcb_svc_com.c | 8 ++++++++
4 files changed, 57 insertions(+), 11 deletions(-)
diff --git a/src/pmap_svc.c b/src/pmap_svc.c
index 4c744fe..e926cdc 100644
--- a/src/pmap_svc.c
+++ b/src/pmap_svc.c
@@ -175,6 +175,7 @@ pmapproc_change(struct svc_req *rqstp /*__unused*/, SVCXPRT *xprt, unsigned long
long ans;
uid_t uid;
char uidbuf[32];
+ int rc = TRUE;
/*
* Can't use getpwnam here. We might end up calling ourselves
@@ -194,7 +195,8 @@ pmapproc_change(struct svc_req *rqstp /*__unused*/, SVCXPRT *xprt, unsigned long
if (!svc_getargs(xprt, (xdrproc_t) xdr_pmap, (char *)®)) {
svcerr_decode(xprt);
- return (FALSE);
+ rc = FALSE;
+ goto done;
}
#ifdef RPCBIND_DEBUG
if (debugging)
@@ -205,7 +207,8 @@ pmapproc_change(struct svc_req *rqstp /*__unused*/, SVCXPRT *xprt, unsigned long
if (!check_access(xprt, op, reg.pm_prog, PMAPVERS)) {
svcerr_weakauth(xprt);
- return (FALSE);
+ rc = (FALSE);
+ goto done;
}
rpcbreg.r_prog = reg.pm_prog;
@@ -258,7 +261,16 @@ done_change:
rpcbs_set(RPCBVERS_2_STAT, ans);
else
rpcbs_unset(RPCBVERS_2_STAT, ans);
- return (TRUE);
+done:
+ if (!svc_freeargs(xprt, (xdrproc_t) xdr_pmap, (char *)®)) {
+ if (debugging) {
+ (void) xlog(LOG_DEBUG, "unable to free arguments\n");
+ if (doabort) {
+ rpcbind_abort();
+ }
+ }
+ }
+ return (rc);
}
/* ARGSUSED */
@@ -272,15 +284,18 @@ pmapproc_getport(struct svc_req *rqstp /*__unused*/, SVCXPRT *xprt)
#ifdef RPCBIND_DEBUG
char *uaddr;
#endif
+ int rc = TRUE;
if (!svc_getargs(xprt, (xdrproc_t) xdr_pmap, (char *)®)) {
svcerr_decode(xprt);
- return (FALSE);
+ rc = FALSE;
+ goto done;
}
if (!check_access(xprt, PMAPPROC_GETPORT, reg.pm_prog, PMAPVERS)) {
svcerr_weakauth(xprt);
- return FALSE;
+ rc = FALSE;
+ goto done;
}
#ifdef RPCBIND_DEBUG
@@ -330,21 +345,34 @@ pmapproc_getport(struct svc_req *rqstp /*__unused*/, SVCXPRT *xprt)
pmap_ipprot2netid(reg.pm_prot) ?: "<unknown>",
port ? udptrans : "");
- return (TRUE);
+done:
+ if (!svc_freeargs(xprt, (xdrproc_t) xdr_pmap, (char *)®)) {
+ if (debugging) {
+ (void) xlog(LOG_DEBUG, "unable to free arguments\n");
+ if (doabort) {
+ rpcbind_abort();
+ }
+ }
+ }
+ return (rc);
}
/* ARGSUSED */
static bool_t
pmapproc_dump(struct svc_req *rqstp /*__unused*/, SVCXPRT *xprt)
{
+ int rc = TRUE;
+
if (!svc_getargs(xprt, (xdrproc_t)xdr_void, NULL)) {
svcerr_decode(xprt);
- return (FALSE);
+ rc = FALSE;
+ goto done;
}
if (!check_access(xprt, PMAPPROC_DUMP, 0, PMAPVERS)) {
svcerr_weakauth(xprt);
- return FALSE;
+ rc = FALSE;
+ goto done;
}
if ((!svc_sendreply(xprt, (xdrproc_t) xdr_pmaplist_ptr,
@@ -354,7 +382,17 @@ pmapproc_dump(struct svc_req *rqstp /*__unused*/, SVCXPRT *xprt)
rpcbind_abort();
}
}
- return (TRUE);
+
+done:
+ if (!svc_freeargs(xprt, (xdrproc_t) xdr_pmap, (char *)NULL)) {
+ if (debugging) {
+ (void) xlog(LOG_DEBUG, "unable to free arguments\n");
+ if (doabort) {
+ rpcbind_abort();
+ }
+ }
+ }
+ return (rc);
}
int pmap_netid2ipprot(const char *netid)
diff --git a/src/rpcb_svc.c b/src/rpcb_svc.c
index 709e3fb..091f530 100644
--- a/src/rpcb_svc.c
+++ b/src/rpcb_svc.c
@@ -166,7 +166,7 @@ rpcb_service_3(struct svc_req *rqstp, SVCXPRT *transp)
svcerr_decode(transp);
if (debugging)
(void) xlog(LOG_DEBUG, "rpcbind: could not decode");
- return;
+ goto done;
}
if (rqstp->rq_proc == RPCBPROC_SET
diff --git a/src/rpcb_svc_4.c b/src/rpcb_svc_4.c
index 5094879..eebbbbe 100644
--- a/src/rpcb_svc_4.c
+++ b/src/rpcb_svc_4.c
@@ -218,7 +218,7 @@ rpcb_service_4(struct svc_req *rqstp, SVCXPRT *transp)
svcerr_decode(transp);
if (debugging)
(void) xlog(LOG_DEBUG, "rpcbind: could not decode\n");
- return;
+ goto done;
}
if (rqstp->rq_proc == RPCBPROC_SET
diff --git a/src/rpcb_svc_com.c b/src/rpcb_svc_com.c
index 5862c26..cb63afd 100644
--- a/src/rpcb_svc_com.c
+++ b/src/rpcb_svc_com.c
@@ -927,6 +927,14 @@ error:
if (call_msg.rm_xid != 0)
(void) free_slot_by_xid(call_msg.rm_xid);
out:
+ if (!svc_freeargs(transp, (xdrproc_t) xdr_rmtcall_args, (char *) &a)) {
+ if (debugging) {
+ (void) xlog(LOG_DEBUG, "unable to free arguments\n");
+ if (doabort) {
+ rpcbind_abort();
+ }
+ }
+ }
if (local_uaddr)
free(local_uaddr);
if (buf_alloc)
--
1.8.3.1
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