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
MFC after:	3 days
Sponsored by:	Orange Business Services

2 files changed, 56 insertions, 5 deletions

diff --git a/sys/netpfil/pf/pf.c b/sys/netpfil/pf/pf.c
index b5f872d40b02..cf077e001ae9 100644
--- a/sys/netpfil/pf/pf.c
+++ b/sys/netpfil/pf/pf.c
@@ -5925,7 +5925,7 @@ again:
 
 static int
 pf_multihome_scan(struct mbuf *m, int start, int len, struct pf_pdesc *pd,
-    struct pfi_kkif *kif, int op)
+    struct pfi_kkif *kif, int op, bool asconf)
 {
 	int			 off = 0;
 	struct pf_sctp_multihome_job	*job;
@@ -6019,13 +6019,16 @@ pf_multihome_scan(struct mbuf *m, int start, int len, struct pf_pdesc *pd,
 			int ret;
 			struct sctp_asconf_paramhdr ah;
 
+			if (asconf)
+				return (PF_DROP);
+
 			if (!pf_pull_hdr(m, start + off, &ah, sizeof(ah),
 			    NULL, NULL, pd->af))
 				return (PF_DROP);
 
 			ret = pf_multihome_scan(m, start + off + sizeof(ah),
 			    ntohs(ah.ph.param_length) - sizeof(ah), pd, kif,
-			    SCTP_ADD_IP_ADDRESS);
+			    SCTP_ADD_IP_ADDRESS, true);
 			if (ret != PF_PASS)
 				return (ret);
 			break;
@@ -6034,12 +6037,15 @@ pf_multihome_scan(struct mbuf *m, int start, int len, struct pf_pdesc *pd,
 			int ret;
 			struct sctp_asconf_paramhdr ah;
 
+			if (asconf)
+				return (PF_DROP);
+
 			if (!pf_pull_hdr(m, start + off, &ah, sizeof(ah),
 			    NULL, NULL, pd->af))
 				return (PF_DROP);
 			ret = pf_multihome_scan(m, start + off + sizeof(ah),
 			    ntohs(ah.ph.param_length) - sizeof(ah), pd, kif,
-			    SCTP_DEL_IP_ADDRESS);
+			    SCTP_DEL_IP_ADDRESS, true);
 			if (ret != PF_PASS)
 				return (ret);
 			break;
@@ -6061,7 +6067,8 @@ pf_multihome_scan_init(struct mbuf *m, int start, int len, struct pf_pdesc *pd,
 	start += sizeof(struct sctp_init_chunk);
 	len -= sizeof(struct sctp_init_chunk);
 
-	return (pf_multihome_scan(m, start, len, pd, kif, SCTP_ADD_IP_ADDRESS));
+	return (pf_multihome_scan(m, start, len, pd, kif, SCTP_ADD_IP_ADDRESS,
+	    false));
 }
 
 int
@@ -6071,7 +6078,8 @@ pf_multihome_scan_asconf(struct mbuf *m, int start, int len,
 	start += sizeof(struct sctp_asconf_chunk);
 	len -= sizeof(struct sctp_asconf_chunk);
 
-	return (pf_multihome_scan(m, start, len, pd, kif, SCTP_ADD_IP_ADDRESS));
+	return (pf_multihome_scan(m, start, len, pd, kif, SCTP_ADD_IP_ADDRESS,
+	    false));
 }
 
 int
diff --git a/tests/sys/netpfil/pf/sctp.py b/tests/sys/netpfil/pf/sctp.py
index 38bb9f2dff74..7cf88c969d48 100644
--- a/tests/sys/netpfil/pf/sctp.py
+++ b/tests/sys/netpfil/pf/sctp.py
@@ -426,6 +426,49 @@ class TestSCTP(VnetTestTemplate):
         assert re.search(r"all sctp 192.0.2.4:.*192.0.2.3:1234", states)
         assert re.search(r"all sctp 192.0.2.4:.*192.0.2.2:1234", states)
 
+class TestSCTP_SRV(VnetTestTemplate):
+    REQUIRED_MODULES = ["sctp", "pf"]
+    TOPOLOGY = {
+        "vnet1": {"ifaces": ["if1"]},
+        "vnet2": {"ifaces": ["if1"]},
+        "if1": {"prefixes4": [("192.0.2.1/24", "192.0.2.2/24")]},
+    }
+
+    def vnet2_handler(self, vnet):
+        ToolsHelper.print_output("/sbin/pfctl -e")
+        ToolsHelper.pf_rules([
+            "set state-policy if-bound",
+            "pass inet proto sctp",
+            "pass on lo"])
+
+        # Start an SCTP server process, pipe the ppid + data back to the other vnet?
+        srv = SCTPServer(socket.AF_INET, port=1234)
+        while True:
+            srv.accept(vnet)
+
+    @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 = {