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bfd: fix ConditionalField condition for optional_auth always being True #4965

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Merged
gpotter2 merged 1 commit into from
Apr 12, 2026
+32 −2
Merged

bfd: fix ConditionalField condition for optional_auth always being True #4965

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2 changes: 1 addition & 1 deletion scapy/contrib/bfd.py
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Original file line number Diff line number Diff line change
Expand Up @@ -131,7 +131,7 @@ class BFD(Packet):
BitField("echo_rx_interval", 1000000000, 32),
ConditionalField(
PacketField("optional_auth", None, OptionalAuth),
lambda pkt: pkt.flags.names[2] == "A",
lambda pkt: pkt.flags.A,
),
]

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32 changes: 31 additions & 1 deletion test/contrib/bfd.uts
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Original file line number Diff line number Diff line change
Expand Up @@ -44,4 +44,34 @@ assert raw(p) == b'\x0e\xc8\x0e\xc8\x008\x00\x00 \xc4\x030\x11\x11\x11\x11"""";\

= BFD with OptionalAuth [Meticulous Keyed SHA1 Auth] [Build]
p = UDP(sport=3784, dport=3784)/BFD(flags="A", optional_auth=OptionalAuth(auth_type=5))
assert raw(p) == b'\x0e\xc8\x0e\xc8\x00<\x00\x00 \xc4\x034\x11\x11\x11\x11"""";\x9a\xca\x00;\x9a\xca\x00;\x9a\xca\x00\x05\x1c\x01\x00\x00\x00\x00\x00[\xaaa\xe4\xc9\xb9??\x06\x82%\x0bl\xf83\x1b~\xe6\x8f\xd8'
assert raw(p) == b'\x0e\xc8\x0e\xc8\x00<\x00\x00 \xc4\x034\x11\x11\x11\x11"""";\x9a\xca\x00;\x9a\xca\x00;\x9a\xca\x00\x05\x1c\x01\x00\x00\x00\x00\x00[\xaaa\xe4\xc9\xb9??\x06\x82%\x0bl\xf83\x1b~\xe6\x8f\xd8'

= BFD without Auth flag - dissection should not inject phantom optional_auth (Issue #4937)

a = UDP(sport=3784, dport=3784)/BFD()
p = UDP(raw(a))
assert p[BFD].optional_auth is None
assert not p[BFD].flags.A

= BFD with non-Auth flags set - optional_auth should still be None

a = UDP(sport=3784, dport=3784)/BFD(flags="DF")
p = UDP(raw(a))
assert p[BFD].flags.D
assert p[BFD].flags.F
assert not p[BFD].flags.A
assert p[BFD].optional_auth is None

= BFD round-trip without auth preserves raw bytes

a = UDP(sport=3784, dport=3784)/BFD()
raw1 = raw(a)
raw2 = raw(UDP(raw1))
assert raw1 == raw2

= BFD with Auth flag set - optional_auth should be present

p = UDP(b'\x04\x00\x0e\xc8\x00\x29\x72\x31\x20\x44\x05\x21\x00\x00\x00\x01\x00\x00\x00\x00\x00\x0f\x42\x40\x00\x0f\x42\x40\x00\x00\x00\x00\x01\x09\x02\x73\x65\x63\x72\x65\x74\x4e\x0a\x90\x40')
assert p[BFD].flags.A
assert p[BFD].optional_auth is not None
assert isinstance(p[BFD].optional_auth, OptionalAuth)
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