git: cc638b24d56a - stable/15 - pf: relax sctp v_tag verification

The branch stable/15 has been updated by kp:

URL: https://cgit.FreeBSD.org/src/commit/?id=cc638b24d56a1472eb366e4320529d6bf77fd4e8

commit cc638b24d56a1472eb366e4320529d6bf77fd4e8
Author:     Kristof Provost <kp@FreeBSD.org>
AuthorDate: 2025-11-25 09:59:02 +0000
Commit:     Kristof Provost <kp@FreeBSD.org>
CommitDate: 2025-12-11 09:22:22 +0000

    pf: relax sctp v_tag verification
    
    pf was too strict when validating SCTP tags. When a server receives a
    retransmitted INIT it will reply with a random initiate tag every time.
    However, pf saves the first initiate tag and expects every subsequent INIT_ACK
    retransmission to have the same tag. This is not the case, leading to endless
    INIT/INIT_ACK cycles.
    
    Allow the tag to be updated as long as we've not gone past COOKIE_WAIT.
    
    Add a test case to verify this.
    
    MFC after:      2 weeks
    See also:       https://redmine.pfsense.org/issues/16516
    Sponsored by:   Rubicon Communications, LLC ("Netgate")
    
    (cherry picked from commit bc3b72ff48953551e0e8bd6e5a2c718ecd973285)
---
 sys/netpfil/pf/pf.c          |  6 +++-
 tests/sys/netpfil/pf/sctp.py | 67 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 72 insertions(+), 1 deletion(-)

diff --git a/sys/netpfil/pf/pf.c b/sys/netpfil/pf/pf.c
index fa6dd41cecee..fb67c37b1556 100644
--- a/sys/netpfil/pf/pf.c
+++ b/sys/netpfil/pf/pf.c
@@ -7362,7 +7362,11 @@ pf_sctp_track(struct pf_kstate *state, struct pf_pdesc *pd,
 	}
 
 	if (src->scrub != NULL) {
-		if (src->scrub->pfss_v_tag == 0)
+		/*
+		 * Allow tags to be updated, in case of retransmission of
+		 * INIT/INIT_ACK chunks.
+		 **/
+		if (src->state <= SCTP_COOKIE_WAIT)
 			src->scrub->pfss_v_tag = pd->hdr.sctp.v_tag;
 		else  if (src->scrub->pfss_v_tag != pd->hdr.sctp.v_tag)
 			return (PF_DROP);
diff --git a/tests/sys/netpfil/pf/sctp.py b/tests/sys/netpfil/pf/sctp.py
index f492f26b63a1..9f1d7dea4ef6 100644
--- a/tests/sys/netpfil/pf/sctp.py
+++ b/tests/sys/netpfil/pf/sctp.py
@@ -551,6 +551,73 @@ class TestSCTP(VnetTestTemplate):
         assert re.search(r"epair.*sctp 192.0.2.1:.*192.0.2.3:1234", states)
         assert re.search(r"epair.*sctp 192.0.2.1:.*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_initiate_tag_check(self):
+        # Ensure we don't send ABORTs in response to the other end's INIT_ACK
+        # That'd interfere with our test.
+        ToolsHelper.print_output("/sbin/sysctl net.inet.sctp.blackhole=2")
+
+        import scapy.all as sp
+
+        packet = sp.IP(src="192.0.2.1", dst="192.0.2.2") \
+            / sp.SCTP(sport=1234, dport=1234) \
+            / sp.SCTPChunkInit(init_tag=1, n_in_streams=1, n_out_streams=1, a_rwnd=1500)
+        packet.show()
+
+        r = sp.sr1(packet, timeout=3)
+        assert r
+        r.show()
+        assert r.getlayer(sp.SCTP)
+        assert r.getlayer(sp.SCTPChunkInitAck)
+        assert r.getlayer(sp.SCTP).tag == 1
+
+        # Send another INIT with the same initiate tag, expect another init ack
+        packet = sp.IP(src="192.0.2.1", dst="192.0.2.2") \
+            / sp.SCTP(sport=1234, dport=1234) \
+            / sp.SCTPChunkInit(init_tag=1, n_in_streams=1, n_out_streams=1, a_rwnd=1500)
+        packet.show()
+
+        r = sp.sr1(packet, timeout=3)
+        assert r
+        r.show()
+        assert r.getlayer(sp.SCTP)
+        assert r.getlayer(sp.SCTPChunkInitAck)
+        assert r.getlayer(sp.SCTP).tag == 1
+
+        # Send an INIT with a different initiate tag, expect another init ack
+        packet = sp.IP(src="192.0.2.1", dst="192.0.2.2") \
+            / sp.SCTP(sport=1234, dport=1234) \
+            / sp.SCTPChunkInit(init_tag=42, n_in_streams=1, n_out_streams=1, a_rwnd=1500)
+        packet.show()
+
+        r = sp.sr1(packet, timeout=3)
+        assert r
+        r.show()
+        assert r.getlayer(sp.SCTP)
+        assert r.getlayer(sp.SCTPChunkInitAck)
+        assert r.getlayer(sp.SCTP).tag == 42
+
 class TestSCTPv6(VnetTestTemplate):
     REQUIRED_MODULES = ["sctp", "pf"]
     TOPOLOGY = {