From 7ea36eeece56b59f98e469934e4c20b4da043346 Mon Sep 17 00:00:00 2001 From: Doran Moppert Date: Thu, 11 May 2017 11:42:54 -0400 Subject: [PATCH 2/6] 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 Signed-off-by: Steve Dickson --- 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) ?: "", 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) -- 2.13.0