pf: improve SCTP validation

As per RFC5061 "4.2.  New Parameter Types" the add/delete IP address
parameters (0xc001, 0xc002) may not be present in an INIT or INIT-ACK
chunk. They are only allowed to be present in an ASCONF chunk.

This also prevents unbounded recursion while parsing an SCTP packet.

Approved by:	so
Security:	FreeBSD-SA-26:14.pf
Security:	CVE-2026-7164
PR:		294799
Reported by:	Igor Gabriel Sousa e Souza
Sponsored by:	Orange Business Services

sys/netpfil/pf/pf.c

@@ -8353,7 +8353,7 @@ pf_sctp_multihome_delayed(struct pf_pdesc *pd, struct pfi_kkif *kif,
 }
 
 static int
-pf_multihome_scan(int start, int len, struct pf_pdesc *pd, int op)
+pf_multihome_scan(int start, int len, struct pf_pdesc *pd, int op, bool asconf)
 {
 	int			 off = 0;
 	struct pf_sctp_multihome_job	*job;
@@ -8458,6 +8458,9 @@ pf_multihome_scan(int start, int len, struct pf_pdesc *pd, int op)
 			int ret;
 			struct sctp_asconf_paramhdr ah;
 
+			if (asconf)
+				return (PF_DROP);
+
 			if (!pf_pull_hdr(pd->m, start + off, &ah, sizeof(ah),
 			    NULL, pd->af))
 				return (PF_DROP);
@@ -8467,7 +8470,7 @@ pf_multihome_scan(int start, int len, struct pf_pdesc *pd, int op)
 
 			ret = pf_multihome_scan(start + off + sizeof(ah),
 			    ntohs(ah.ph.param_length) - sizeof(ah), pd,
-			    SCTP_ADD_IP_ADDRESS);
+			    SCTP_ADD_IP_ADDRESS, true);
 			if (ret != PF_PASS)
 				return (ret);
 			break;
@@ -8476,6 +8479,9 @@ pf_multihome_scan(int start, int len, struct pf_pdesc *pd, int op)
 			int ret;
 			struct sctp_asconf_paramhdr ah;
 
+			if (asconf)
+				return (PF_DROP);
+
 			if (!pf_pull_hdr(pd->m, start + off, &ah, sizeof(ah),
 			    NULL, pd->af))
 				return (PF_DROP);
@@ -8485,7 +8491,7 @@ pf_multihome_scan(int start, int len, struct pf_pdesc *pd, int op)
 
 			ret = pf_multihome_scan(start + off + sizeof(ah),
 			    ntohs(ah.ph.param_length) - sizeof(ah), pd,
-			    SCTP_DEL_IP_ADDRESS);
+			    SCTP_DEL_IP_ADDRESS, true);
 			if (ret != PF_PASS)
 				return (ret);
 			break;
@@ -8506,7 +8512,7 @@ pf_multihome_scan_init(int start, int len, struct pf_pdesc *pd)
 	start += sizeof(struct sctp_init_chunk);
 	len -= sizeof(struct sctp_init_chunk);
 
-	return (pf_multihome_scan(start, len, pd, SCTP_ADD_IP_ADDRESS));
+	return (pf_multihome_scan(start, len, pd, SCTP_ADD_IP_ADDRESS, false));
 }
 
 int
@@ -8515,7 +8521,7 @@ pf_multihome_scan_asconf(int start, int len, struct pf_pdesc *pd)
 	start += sizeof(struct sctp_asconf_chunk);
 	len -= sizeof(struct sctp_asconf_chunk);
 
-	return (pf_multihome_scan(start, len, pd, SCTP_ADD_IP_ADDRESS));
+	return (pf_multihome_scan(start, len, pd, SCTP_ADD_IP_ADDRESS, false));
 }
 
 int

tests/sys/netpfil/pf/sctp.py

@@ -618,6 +618,29 @@ def test_initiate_tag_check(self):
         assert r.getlayer(sp.SCTPChunkInitAck)
         assert r.getlayer(sp.SCTP).tag == 42
 
+    @pytest.mark.require_user("root")
+    @pytest.mark.require_progs(["scapy"])
+    def test_too_many_add_ip(self):
+        import scapy.all as sp
+        DEPTH=90
+        params=[]
+        for i in range(0, DEPTH):
+            ch = sp.SCTPChunkParamAddIPAddr(len=(DEPTH - i) * 8)
+            params.append(ch)
+        packet = sp.IP(src="192.0.2.1", dst="192.0.2.2") \
+            / sp.SCTP(sport=4321, dport=1234) \
+            / sp.SCTPChunkInit(init_tag=1, n_in_streams=1, n_out_streams=1, a_rwnd=1500,
+                params=params)
+        packet.show()
+        sp.hexdump(packet)
+        print("len %d" % len(packet))
+
+        r = sp.sr1(packet, timeout=3)
+        # We should not get a reply to this
+        if r:
+            r.show()
+        assert not r
+
 class TestSCTPv6(VnetTestTemplate):
     REQUIRED_MODULES = ["sctp", "pf"]
     TOPOLOGY = {