Improve input validation for some parameters having a too small reported length.

Thanks to Natalie Silvanovich from Google for finding one of these
issues in the SCTP userland stack and reporting it.
diff --git a/usrsctplib/netinet/sctp_auth.c b/usrsctplib/netinet/sctp_auth.c
index 5e5813b..bc645b3 100755
--- a/usrsctplib/netinet/sctp_auth.c
+++ b/usrsctplib/netinet/sctp_auth.c
@@ -34,7 +34,7 @@
 
 #ifdef __FreeBSD__
 #include <sys/cdefs.h>
-__FBSDID("$FreeBSD: head/sys/netinet/sctp_auth.c 334532 2018-06-02 16:28:10Z tuexen $");
+__FBSDID("$FreeBSD: head/sys/netinet/sctp_auth.c 355931 2019-12-20 15:25:08Z tuexen $");
 #endif
 
 #include <netinet/sctp_os.h>
@@ -1455,7 +1455,8 @@
 		ptype = ntohs(phdr->param_type);
 		plen = ntohs(phdr->param_length);
 
-		if ((plen == 0) || (offset + plen > length))
+		if ((plen < sizeof(struct sctp_paramhdr)) ||
+		    (offset + plen > length))
 			break;
 
 		if (ptype == SCTP_RANDOM) {
diff --git a/usrsctplib/netinet/sctp_pcb.c b/usrsctplib/netinet/sctp_pcb.c
index 6efcbab..355686f 100755
--- a/usrsctplib/netinet/sctp_pcb.c
+++ b/usrsctplib/netinet/sctp_pcb.c
@@ -34,7 +34,7 @@
 
 #ifdef __FreeBSD__
 #include <sys/cdefs.h>
-__FBSDID("$FreeBSD: head/sys/netinet/sctp_pcb.c 334532 2018-06-02 16:28:10Z tuexen $");
+__FBSDID("$FreeBSD: head/sys/netinet/sctp_pcb.c 355931 2019-12-20 15:25:08Z tuexen $");
 #endif
 
 #include <netinet/sctp_os.h>
@@ -7246,7 +7246,7 @@
 		if (offset + plen > limit) {
 			break;
 		}
-		if (plen == 0) {
+		if (plen < sizeof(struct sctp_paramhdr)) {
 			break;
 		}
 #ifdef INET
@@ -7462,6 +7462,9 @@
 			if (plen > sizeof(lstore)) {
 				return (-23);
 			}
+			if (plen < sizeof(struct sctp_asconf_addrv4_param)) {
+				return (-101);
+			}
 			phdr = sctp_get_next_param(m, offset,
 						   (struct sctp_paramhdr *)&lstore,
 						   plen);