rpcbind: Security Advisory - rpcbind - CVE-2015-7236

rpcbind: Fix memory corruption in PMAP_CALLIT code

Use-after-free vulnerability in xprt_set_caller in rpcb_svc_com.c in
rpcbind 0.2.1 and earlier allows remote attackers to cause a denial of
service (daemon crash) via crafted packets, involving a PMAP_CALLIT
code.

The patch comes from
<http://www.openwall.com/lists/oss-security/2015/09/18/7>, and it hasn't
been in rpcbind upstream yet.

(From OE-Core rev: cc4f62f3627f3804907e8ff9c68d9321979df32b)

Signed-off-by: Li Zhou <li.zhou@windriver.com>
Signed-off-by: Wenzong Fan <wenzong.fan@windriver.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-extended/rpcbind/rpcbind/cve-2015-7236.patch

@@ -0,0 +1,83 @@
+commit 06f7ebb1dade2f0dbf872ea2bedf17cff4734bdd
+Author: Olaf Kirch <okir@...e.de>
+Date:   Thu Aug 6 16:27:20 2015 +0200
+
+    Fix memory corruption in PMAP_CALLIT code
+    
+     - A PMAP_CALLIT call comes in on IPv4 UDP
+     - rpcbind duplicates the caller's address to a netbuf and stores it in
+       FINFO[0].caller_addr. caller_addr->buf now points to a memory region A
+       with a size of 16 bytes
+     - rpcbind forwards the call to the local service, receives a reply
+     - when processing the reply, it does this in xprt_set_caller:
+         xprt->xp_rtaddr = *FINFO[0].caller_addr
+       It sends out the reply, and then frees the netbuf caller_addr and
+       caller_addr.buf.
+       However, it does not clear xp_rtaddr, so xp_rtaddr.buf now refers
+       to memory region A, which is free.
+     - When the next call comes in on the UDP/IPv4 socket, svc_dg_recv will
+       be called, which will set xp_rtaddr to the client's address.
+       It will reuse the buffer inside xp_rtaddr, ie it will write a
+       sockaddr_in to region A
+    
+    Some time down the road, an incoming TCP connection is accepted,
+    allocating a fresh SVCXPRT. The memory region A is inside the
+    new SVCXPRT
+    
+     - While processing the TCP call, another UDP call comes in, again
+       overwriting region A with the client's address
+     - TCP client closes connection. In svc_destroy, we now trip over
+       the garbage left in region A
+    
+    We ran into the case where a commercial scanner was triggering
+    occasional rpcbind segfaults. The core file that was captured showed
+    a corrupted xprt->xp_netid pointer that was really a sockaddr_in.
+    
+    Signed-off-by: Olaf Kirch <okir@...e.de>
+
+    Upstream-Status: Backport
+
+    Signed-off-by: Li Zhou <li.zhou@windriver.com>
+---
+ src/rpcb_svc_com.c |   23 ++++++++++++++++++++++-
+ 1 file changed, 22 insertions(+), 1 deletion(-)
+
+Index: rpcbind-0.1.6+git20080930/src/rpcb_svc_com.c
+===================================================================
+--- rpcbind-0.1.6+git20080930.orig/src/rpcb_svc_com.c
++++ rpcbind-0.1.6+git20080930/src/rpcb_svc_com.c
+@@ -1298,12 +1298,33 @@ check_rmtcalls(struct pollfd *pfds, int
+ 	return (ncallbacks_found);
+ }
+ 
++/*
++ * This is really a helper function defined in libtirpc, but unfortunately, it hasn't
++ * been exported yet.
++ */
++static struct netbuf *
++__rpc_set_netbuf(struct netbuf *nb, const void *ptr, size_t len)
++{
++	if (nb->len != len) {
++		if (nb->len)
++			mem_free(nb->buf, nb->len);
++		nb->buf = mem_alloc(len);
++		if (nb->buf == NULL)
++			return NULL;
++
++		nb->maxlen = nb->len = len;
++	}
++	memcpy(nb->buf, ptr, len);
++	return nb;
++}
++
+ static void
+ xprt_set_caller(SVCXPRT *xprt, struct finfo *fi)
+ {
++	const struct netbuf *caller = fi->caller_addr;
+ 	u_int32_t *xidp;
+ 
+-	*(svc_getrpccaller(xprt)) = *(fi->caller_addr);
++	__rpc_set_netbuf(svc_getrpccaller(xprt), caller->buf, caller->len);
+ 	xidp = __rpcb_get_dg_xidp(xprt);
+ 	*xidp = fi->caller_xid;
+ }

meta/recipes-extended/rpcbind/rpcbind_0.2.3.bb

@@ -19,6 +19,7 @@ SRC_URI = "${SOURCEFORGE_MIRROR}/rpcbind/rpcbind-${PV}.tar.bz2 \
            file://rpcbind.conf \
            file://rpcbind.socket \
            file://rpcbind.service \
+           file://cve-2015-7236.patch \
           "
 MUSLPATCHES_libc-musl = "file://musl-sunrpc.patch"