Fix CVE-2017-8779:

https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-8779

Patch copied from the bug reporter's 3rd-party repository:

https://github.com/guidovranken/rpcbomb/blob/master/libtirpc_patch.txt

diff --git a/src/rpc_generic.c b/src/rpc_generic.c
index 2f09a8f..589cbd5 100644
--- a/src/rpc_generic.c
+++ b/src/rpc_generic.c
@@ -615,6 +615,9 @@ __rpc_taddr2uaddr_af(int af, const struct netbuf *nbuf)
 
 	switch (af) {
 	case AF_INET:
+		if (nbuf->len < sizeof(*sin)) {
+			return NULL;
+		}
 		sin = nbuf->buf;
 		if (inet_ntop(af, &sin->sin_addr, namebuf, sizeof namebuf)
 		    == NULL)
@@ -626,6 +629,9 @@ __rpc_taddr2uaddr_af(int af, const struct netbuf *nbuf)
 		break;
 #ifdef INET6
 	case AF_INET6:
+		if (nbuf->len < sizeof(*sin6)) {
+			return NULL;
+		}
 		sin6 = nbuf->buf;
 		if (inet_ntop(af, &sin6->sin6_addr, namebuf6, sizeof namebuf6)
 		    == NULL)
@@ -667,6 +673,8 @@ __rpc_uaddr2taddr_af(int af, const char *uaddr)
 
 	port = 0;
 	sin = NULL;
+	if (uaddr == NULL)
+		return NULL;
 	addrstr = strdup(uaddr);
 	if (addrstr == NULL)
 		return NULL;
diff --git a/src/rpcb_prot.c b/src/rpcb_prot.c
index 43fd385..a923c8e 100644
--- a/src/rpcb_prot.c
+++ b/src/rpcb_prot.c
@@ -41,6 +41,7 @@
 #include <rpc/types.h>
 #include <rpc/xdr.h>
 #include <rpc/rpcb_prot.h>
+#include "rpc_com.h"
 
 bool_t
 xdr_rpcb(xdrs, objp)
@@ -53,13 +54,13 @@ xdr_rpcb(xdrs, objp)
 	if (!xdr_u_int32_t(xdrs, &objp->r_vers)) {
 		return (FALSE);
 	}
-	if (!xdr_string(xdrs, &objp->r_netid, (u_int)~0)) {
+	if (!xdr_string(xdrs, &objp->r_netid, RPC_MAXDATASIZE)) {
 		return (FALSE);
 	}
-	if (!xdr_string(xdrs, &objp->r_addr, (u_int)~0)) {
+	if (!xdr_string(xdrs, &objp->r_addr, RPC_MAXDATASIZE)) {
 		return (FALSE);
 	}
-	if (!xdr_string(xdrs, &objp->r_owner, (u_int)~0)) {
+	if (!xdr_string(xdrs, &objp->r_owner, RPC_MAXDATASIZE)) {
 		return (FALSE);
 	}
 	return (TRUE);
@@ -159,19 +160,19 @@ xdr_rpcb_entry(xdrs, objp)
 	XDR *xdrs;
 	rpcb_entry *objp;
 {
-	if (!xdr_string(xdrs, &objp->r_maddr, (u_int)~0)) {
+	if (!xdr_string(xdrs, &objp->r_maddr, RPC_MAXDATASIZE)) {
 		return (FALSE);
 	}
-	if (!xdr_string(xdrs, &objp->r_nc_netid, (u_int)~0)) {
+	if (!xdr_string(xdrs, &objp->r_nc_netid, RPC_MAXDATASIZE)) {
 		return (FALSE);
 	}
 	if (!xdr_u_int32_t(xdrs, &objp->r_nc_semantics)) {
 		return (FALSE);
 	}
-	if (!xdr_string(xdrs, &objp->r_nc_protofmly, (u_int)~0)) {
+	if (!xdr_string(xdrs, &objp->r_nc_protofmly, RPC_MAXDATASIZE)) {
 		return (FALSE);
 	}
-	if (!xdr_string(xdrs, &objp->r_nc_proto, (u_int)~0)) {
+	if (!xdr_string(xdrs, &objp->r_nc_proto, RPC_MAXDATASIZE)) {
 		return (FALSE);
 	}
 	return (TRUE);
@@ -292,7 +293,7 @@ xdr_rpcb_rmtcallres(xdrs, p)
 	bool_t dummy;
 	struct r_rpcb_rmtcallres *objp = (struct r_rpcb_rmtcallres *)(void *)p;
 
-	if (!xdr_string(xdrs, &objp->addr, (u_int)~0)) {
+	if (!xdr_string(xdrs, &objp->addr, RPC_MAXDATASIZE)) {
 		return (FALSE);
 	}
 	if (!xdr_u_int(xdrs, &objp->results.results_len)) {
@@ -312,6 +313,11 @@ xdr_netbuf(xdrs, objp)
 	if (!xdr_u_int32_t(xdrs, (u_int32_t *) &objp->maxlen)) {
 		return (FALSE);
 	}
+
+	if (objp->maxlen > RPC_MAXDATASIZE) {
+		return (FALSE);
+	}
+
 	dummy = xdr_bytes(xdrs, (char **)&(objp->buf),
 			(u_int *)&(objp->len), objp->maxlen);
 	return (dummy);
diff --git a/src/rpcb_st_xdr.c b/src/rpcb_st_xdr.c
index 08db745..28e6a48 100644
--- a/src/rpcb_st_xdr.c
+++ b/src/rpcb_st_xdr.c
@@ -37,6 +37,7 @@
 
 
 #include <rpc/rpc.h>
+#include "rpc_com.h"
 
 /* Link list of all the stats about getport and getaddr */
 
@@ -58,7 +59,7 @@ xdr_rpcbs_addrlist(xdrs, objp)
 	    if (!xdr_int(xdrs, &objp->failure)) {
 		return (FALSE);
 	    }
-	    if (!xdr_string(xdrs, &objp->netid, (u_int)~0)) {
+	    if (!xdr_string(xdrs, &objp->netid, RPC_MAXDATASIZE)) {
 		return (FALSE);
 	    }
 
@@ -109,7 +110,7 @@ xdr_rpcbs_rmtcalllist(xdrs, objp)
 		IXDR_PUT_INT32(buf, objp->failure);
 		IXDR_PUT_INT32(buf, objp->indirect);
 	}
-	if (!xdr_string(xdrs, &objp->netid, (u_int)~0)) {
+	if (!xdr_string(xdrs, &objp->netid, RPC_MAXDATASIZE)) {
 		return (FALSE);
 	}
 	if (!xdr_pointer(xdrs, (char **)&objp->next,
@@ -147,7 +148,7 @@ xdr_rpcbs_rmtcalllist(xdrs, objp)
 		objp->failure = (int)IXDR_GET_INT32(buf);
 		objp->indirect = (int)IXDR_GET_INT32(buf);
 	}
-	if (!xdr_string(xdrs, &objp->netid, (u_int)~0)) {
+	if (!xdr_string(xdrs, &objp->netid, RPC_MAXDATASIZE)) {
 		return (FALSE);
 	}
 	if (!xdr_pointer(xdrs, (char **)&objp->next,
@@ -175,7 +176,7 @@ xdr_rpcbs_rmtcalllist(xdrs, objp)
 	if (!xdr_int(xdrs, &objp->indirect)) {
 		return (FALSE);
 	}
-	if (!xdr_string(xdrs, &objp->netid, (u_int)~0)) {
+	if (!xdr_string(xdrs, &objp->netid, RPC_MAXDATASIZE)) {
 		return (FALSE);
 	}
 	if (!xdr_pointer(xdrs, (char **)&objp->next,
diff --git a/src/xdr.c b/src/xdr.c
index f3fb9ad..b9a1558 100644
--- a/src/xdr.c
+++ b/src/xdr.c
@@ -42,8 +42,10 @@
 #include <stdlib.h>
 #include <string.h>
 
+#include <rpc/rpc.h>
 #include <rpc/types.h>
 #include <rpc/xdr.h>
+#include <rpc/rpc_com.h>
 
 typedef quad_t          longlong_t;     /* ANSI long long type */
 typedef u_quad_t        u_longlong_t;   /* ANSI unsigned long long type */
@@ -53,7 +55,6 @@ typedef u_quad_t        u_longlong_t;   /* ANSI unsigned long long type */
  */
 #define XDR_FALSE	((long) 0)
 #define XDR_TRUE	((long) 1)
-#define LASTUNSIGNED	((u_int) 0-1)
 
 /*
  * for unit alignment
@@ -629,6 +630,7 @@ xdr_bytes(xdrs, cpp, sizep, maxsize)
 {
 	char *sp = *cpp;  /* sp is the actual string pointer */
 	u_int nodesize;
+	bool_t ret, allocated = FALSE;
 
 	/*
 	 * first deal with the length since xdr bytes are counted
@@ -652,6 +654,7 @@ xdr_bytes(xdrs, cpp, sizep, maxsize)
 		}
 		if (sp == NULL) {
 			*cpp = sp = mem_alloc(nodesize);
+			allocated = TRUE;
 		}
 		if (sp == NULL) {
 			warnx("xdr_bytes: out of memory");
@@ -660,7 +663,14 @@ xdr_bytes(xdrs, cpp, sizep, maxsize)
 		/* FALLTHROUGH */
 
 	case XDR_ENCODE:
-		return (xdr_opaque(xdrs, sp, nodesize));
+		ret = xdr_opaque(xdrs, sp, nodesize);
+		if ((xdrs->x_op == XDR_DECODE) && (ret == FALSE)) {
+			if (allocated == TRUE) {
+				free(sp);
+				*cpp = NULL;
+			}
+		}
+		return (ret);
 
 	case XDR_FREE:
 		if (sp != NULL) {
@@ -754,6 +764,7 @@ xdr_string(xdrs, cpp, maxsize)
 	char *sp = *cpp;  /* sp is the actual string pointer */
 	u_int size;
 	u_int nodesize;
+	bool_t ret, allocated = FALSE;
 
 	/*
 	 * first deal with the length since xdr strings are counted-strings
@@ -793,8 +804,10 @@ xdr_string(xdrs, cpp, maxsize)
 	switch (xdrs->x_op) {
 
 	case XDR_DECODE:
-		if (sp == NULL)
+		if (sp == NULL) {
 			*cpp = sp = mem_alloc(nodesize);
+			allocated = TRUE;
+		}
 		if (sp == NULL) {
 			warnx("xdr_string: out of memory");
 			return (FALSE);
@@ -803,7 +816,14 @@ xdr_string(xdrs, cpp, maxsize)
 		/* FALLTHROUGH */
 
 	case XDR_ENCODE:
-		return (xdr_opaque(xdrs, sp, size));
+		ret = xdr_opaque(xdrs, sp, size);
+		if ((xdrs->x_op == XDR_DECODE) && (ret == FALSE)) {
+			if (allocated == TRUE) {
+				free(sp);
+				*cpp = NULL;
+			}
+		}
+		return (ret);
 
 	case XDR_FREE:
 		mem_free(sp, nodesize);
@@ -823,7 +843,7 @@ xdr_wrapstring(xdrs, cpp)
 	XDR *xdrs;
 	char **cpp;
 {
-	return xdr_string(xdrs, cpp, LASTUNSIGNED);
+	return xdr_string(xdrs, cpp, RPC_MAXDATASIZE);
 }
 
 /*
