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Bgp: Fix an undefined behavior when it tries to parse a too-short packet
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It's not enough for the *packet* to be able to contain the RD;
the route data also has to be long enough; otherwise, we will
try to shift a negative length left in order to pass it to
bgp_vpn_ip_print()

print-bgp.c:1848:9: runtime error: left shift of negative value -8
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior print-bgp.c:1848:9

[Part of the PR the-tcpdump-group#1012]
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@fenner @fxlb
fenner authored and fxlb committed Aug 22, 2023
1 parent dbca207 commit 5a5646b
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2 changes: 2 additions & 0 deletions print-bgp.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1268,6 +1268,8 @@ decode_multicast_vpn(netdissect_options *ndo,
switch(route_type) {
case BGP_MULTICAST_VPN_ROUTE_TYPE_INTRA_AS_I_PMSI:
ND_TCHECK_LEN(pptr, BGP_VPN_RD_LEN);
if (route_length < BGP_VPN_RD_LEN)
goto trunc;
offset = (u_int)strlen(buf);
snprintf(buf + offset, buflen - offset, ", RD: %s, Originator %s",
bgp_vpn_rd_print(ndo, pptr),
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1 change: 1 addition & 0 deletions tests/TESTLIST
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Original file line number Diff line number Diff line change
Expand Up @@ -930,3 +930,4 @@ ip-snmp-leftshift-unsigned ip-snmp-leftshift-unsigned.pcap ip-snmp-leftshift-uns
ip6-snmp-oid-unsigned ip6-snmp-oid-unsigned.pcap ip6-snmp-oid-unsigned.out
lwres-pointer-arithmetic-ub lwres-pointer-arithmetic-ub.pcap lwres-pointer-arithmetic-ub.out
ospf-signed-integer-ubsan ospf-signed-integer-ubsan.pcap ospf-signed-integer-ubsan.out -vv
bgp-ub bgp-ub.pcap bgp-ub.out -v
227 changes: 227 additions & 0 deletions tests/bgp-ub.out
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Original file line number Diff line number Diff line change
@@ -0,0 +1,227 @@
1 13:29:37.678220 IP (tos 0x0, ttl 64, id 1, offset 0, flags [none], proto TCP (6), length 4748)
127.0.0.1.540 > 127.0.0.1.179: Flags [S], cksum 0xf1a8 (correct), seq 0:4708, win 8192, length 4708: BGP [|bgp]
Update Message (2), length: 154
Origin (1), length: 1, Flags [T]: Incomplete
AS Path (2), length: 0, Flags [T]: empty
Multi Exit Discriminator (4), length: 4, Flags [O]: 0
Local Preference (5), length: 4, Flags [T]: 4456548
Extended Community (16), length: 8, Flags [OT]:
target (0x0002), Flags [none]: 18826:630 (= 0.0.2.118)
Cluster List (10), length: 4, Flags [O]: 172.17.0.0
Originator ID (9), length: 4, Flags [O]: 172.17.0.5
Multi-Protocol Reach NLRI (14), length: 81, Flags [OE]:
AFI: IPv4 (1), SAFI: labeled VPN Unicast (128)
nexthop: RD: 0:0 (= 0.0.0.0), 172.145.0.5, nh-length: 12, no SNPA
RD: 18826:630 (= 0.0.2.118), 172.17.30.208/28, label:1027 (bottom)
RD: 18826:630 (= 0.0.2.118), 172.17.30.224/28, label:1027 (bottom)
(illegal prefix length)
Update Message (2), length: 105
Origin (1), length: 1, Flags [T]: Incomplete
AS Path (2), length: 0, Flags [T]: empty
Multi Exit Discriminator (4), length: 4, Flags [O]: 0
Local Preference (5), length: 4, Flags [T]: 100
Extended Community (16), length: 8, Flags [OT]:
target (0x0002), Flags [none]: 18826:620 (= 0.0.2.108)
Cluster List (10), length: 37, Flags [O]: invalid len
Unknown Attribute (73), length: 138 [path attrs too short]
Update Message (2), length: 154
Origin (1), length: 1, Flags [T]: Incomplete
AS Path (2), length: 0, Flags [T]: empty
Multi Exit Discriminator (4), length: 4, Flags [O]: 0
Local Preference (5), length: 4, Flags [T]: 100
Extended Community (16), length: 8, Flags [OT]:
target (0x0002), Flags [none]: 18826:640 (= 0.0.2.128)
Cluster List (10), length: 4, Flags [O]: 172.17.0.0
Originator ID (9), length: 4, Flags [O]: 172.17.0.5
Multi-Protocol Reach NLRI (14), length: 81, Flags [OE]:
AFI: IPv4 (1), SAFI: labeled VPN Unicast (128)
nexthop: RD: 0:0 (= 0.0.0.0), 172.17.0.5, nh-length: 12, no SNPA
RD: 18826:640 (= 0.0.2.128), 172.17.33.64/28, label:1028 (bottom)
RD: 18826:640 (= 0.0.2.128), 172.17.33.80/28, label:1028 (bottom)
RD: 18826:640 (= 0.0.2.128), 172.84.34.0/28, label:132100 (bottom)
RD: 18826:549 (= 0.0.2.37), 0.17.34.16/28, label:1028 (bottom)
Update Message (2), length: 202
Withdrawn routes:
0.0.0.0/0
(illegal prefix length) [|bgp] [|bgp]
Update Message (2), length: 106
Origin (1), length: 1, Flags [T]: Incomplete
AS Path (2), length: 0, Flags [T]: empty
Attribute Set (128), length: 3, Flags [O]: [|bgp] [|bgp]
Update Message (2), length: 172
Origin (1), length: 1, Flags [T]: Incomplete
AS Path (2), length: 4, Flags [T]: 64520
Multi Exit Discriminator (4), length: 4, Flags [O]: 131
Unknown Attribute (113), length: 16, Flags [T]:
no Attribute 113 decoder
0x0000: ffff ffff ffff ffff ffff ffff ffff ffff
Unknown Attribute (75), length: 2
no Attribute 75 decoder
0x0000: 0000
Unknown Attribute (47), length: 64
no Attribute 47 decoder
0x0000: 0101 0040 0206 0201 0001 0000 4003 04c0
0x0010: 0002 02c0 2018 0001 0000 0000 0001 0000
0x0020: 0001 0001 0000 0000 0001 0000 0002 20cb
0x0030: 0071 0cff ffff ffff ffff ffff ffff ffff
Reserved for development (255), length: 65280, Flags [OTPE+f]: [path attrs too short] [|bgp]
Update Message (2), length: 75
Origin (1), length: 1, Flags [T]: IGP
AS Path (2), length: 6, Flags [T]: 65536
Next Hop (3), length: 4, Flags [T]: 192.0.2.2
Large Community (32), length: 24, Flags [OT]:
65536:0:1, 65536:1:0
Updated routes:
203.0.113.15/32
Update Message (2), length: 87
Origin (1), length: 1, Flags [T]: IGP
AS Path (2), length: 6, Flags [T]: 65536
Next Hop (3), length: 4, Flags [T]: 5.12.0.0
Unknown Attribute (100), length: 192, Flags [+1]: [path attrs too short]
Updated routes:
0.0.0.0/0
(illegal prefix length) [|bgp]
Update Message (2), length: 105
Origin (1), length: 1, Flags [T]: Incomplete
AS Path (2), length: 0, Flags [T]: empty
Multi Exit Discriminator (4), length: 4, Flags [O]: 0
Local Preference (5), length: 4, Flags [T]: 100
Extended Community (16), length: 8, Flags [OT]:
target (0x0002), Flags [none]: 18826:620 (= 0.0.2.108)
Cluster List (10), length: 37, Flags [O]: invalid len
Unknown Attribute (73), length: 138 [path attrs too short]
Update Message (2), length: 154
Origin (1), length: 1, Flags [T]: Incomplete
AS Path (2), length: 0, Flags [T]: empty
Multi Exit Discriminator (4), length: 4, Flags [O]: 0
Local Preference (5), length: 4, Flags [T]: 100
Extended Community (16), length: 8, Flags [OT]:
target (0x0002), Flags [none]: 18826:640 (= 0.0.2.128)
Cluster List (10), length: 4, Flags [O]: 172.17.0.0
Originator ID (9), length: 4, Flags [O]: 172.17.0.5
Multi-Protocol Reach NLRI (14), length: 81, Flags [OE]:
AFI: IPv4 (1), SAFI: labeled VPN Unicast (128)
nexthop: RD: 0:0 (= 0.0.0.0), 172.17.0.5, nh-length: 12, no SNPA
RD: 18826:640 (= 0.0.2.128), 172.17.33.64/28, label:1028 (bottom)
RD: 18826:640 (= 0.0.2.128), 172.17.33.80/28, label:1028 (bottom)
RD: 18826:640 (= 0.0.2.128), 172.84.34.0/28, label:132100 (bottom)
RD: 18826:549 (= 0.0.2.37), 0.17.34.16/28, label:1028 (bottom)
Update Message (2), length: 202
Withdrawn routes:
0.0.0.0/0
(illegal prefix length) [|bgp] [|bgp]
Update Message (2), length: 106
Origin (1), length: 1, Flags [T]: Incomplete
AS Path (2), length: 0, Flags [T]: empty
Attribute Set (128), length: 3, Flags [O]: [|bgp] [|bgp]
Update Message (2), length: 172
Origin (1), length: 1, Flags [T]: Incomplete
AS Path (2), length: 4, Flags [T]: 64520
Multi Exit Discriminator (4), length: 4, Flags [O]: 131
Unknown Attribute (113), length: 16, Flags [T]:
no Attribute 113 decoder
0x0000: ffff ffff ffff ffff ffff ffff ffff ffff
Unknown Attribute (75), length: 2
no Attribute 75 decoder
0x0000: 0000
Unknown Attribute (47), length: 64
no Attribute 47 decoder
0x0000: 0101 0040 0206 0201 0001 0000 4003 04c0
0x0010: 0002 02c0 2018 0001 0000 0000 0001 0000
0x0020: 0001 0001 0000 0000 0001 0000 0002 20cb
0x0030: 0071 0cff ffff ffff ffff ffff ffff ffff
Reserved for development (255), length: 65280, Flags [OTPE+f]: [path attrs too short] [|bgp]
Update Message (2), length: 75
Origin (1), length: 1, Flags [T]: IGP
AS Path (2), length: 6, Flags [T]: 65536
Next Hop (3), length: 4, Flags [T]: 192.0.2.2
Large Community (32), length: 24, Flags [OT]:
65536:0:1, 65536:1:0
Updated routes:
203.0.113.15/32
Update Message (2), length: 87
Origin (1), length: 1, Flags [T]: IGP
AS Path (2), length: 6, Flags [T]: 65536
Next Hop (3), length: 4, Flags [T]: 5.12.0.0
Unknown Attribute (100), length: 192, Flags [+1]: [path attrs too short]
Updated routes:
0.0.0.0/0
(illegal prefix length) [|bgp]
Update Message (2), length: 106
Origin (1), length: 1, Flags [T]: Incomplete
AS Path (2), length: 0, Flags [T]: empty
Multi Exit Discriminator (4), length: 4, Flags [O]: 0
Local Preference (5), length: 4, Flags [T]: 100
Extended Community (16), length: 8, Flags [OT]:
target (0x0002), Flags [none]: 18826:610 (= 0.0.2.98)
Cluster List (10), length: 40, Flags [O]: 24.120.4.0, 0.0.0.41, 24.120.4.1, 64.15.19.0, 1.1.0.0, 2.188.24.32, 45.0.0.0, 2.189.24.32, 45.1.64.14, 61.0.2.1
Large Community (32), length: 0, Flags [E]: invalid len
Unknown Attribute (21), length: 24 [path attrs too short] [|bgp]
Update Message (2), length: 100
Unknown Attribute (0), length: 0
no Attribute 0 decoder
Reserved for development (255), length: 255 [path attrs too short] [|bgp]
Update Message (2), length: 95
Origin (1), length: 1, Flags [T]: IGP
AS Path (2), length: 0, Flags [T]: empty
Local Preference (5), length: 4, Flags [T]: 100
Extended Community (16), length: 8, Flags [OT]:
target (0x0002), Flags [none]: 1:1 (= 0.0.0.1)
PMSI Tunnel (22), length: 17, Flags [OT]:
Tunnel-type RSVP-TE P2MP LSP (1), Flags [none], MPLS Label 0
Extended-Tunnel-ID 10.0.0.4, P2MP-ID 0x00008173
Multi-Protocol Reach NLRI (14), length: 23, Flags [OE]:
AFI: IPv4 (1), SAFI: Multicast VPN (5)
nexthop: 10.0.0.4, nh-length: 4
8 SNPA
1 bytes
0 bytes
0 bytes
0 bytes
1 bytes
0 bytes
1 bytes
0 bytes
Route-Type: Unknown (181), length: 0 [|bgp] [|bgp]
Update Message (2), length: 106
Origin (1), length: 1, Flags [T]: Incomplete
AS Path (2), length: 0, Flags [T]: empty
Multi Exit Discriminator (4), length: 4, Flags [O]: 0
Local Preference (5), length: 4, Flags [T]: 100
Extended Community (16), length: 8, Flags [OT]:
target (0x0002), Flags [none]: 18826:610 (= 0.0.2.98)
Cluster List (10), length: 40, Flags [O]: 24.120.4.0, 0.0.0.41, 24.120.4.1, 64.15.19.0, 1.1.0.0, 2.188.24.32, 45.0.0.0, 2.189.24.32, 45.1.64.14, 61.0.2.1
Large Community (32), length: 0, Flags [E]: invalid len
Unknown Attribute (21), length: 24 [path attrs too short] [|bgp]
Update Message (2), length: 100
Unknown Attribute (0), length: 0
no Attribute 0 decoder
Reserved for development (255), length: 255 [path attrs too short] [|bgp]
Update Message (2), length: 95
Origin (1), length: 1, Flags [T]: IGP
AS Path (2), length: 0, Flags [T]: empty
Local Preference (5), length: 4, Flags [T]: 100
Extended Community (16), length: 8, Flags [OT]:
target (0x0002), Flags [none]: 1:1 (= 0.0.0.1)
PMSI Tunnel (22), length: 17, Flags [OT]:
Tunnel-type RSVP-TE P2MP LSP (1), Flags [none], MPLS Label 0
Extended-Tunnel-ID 10.0.0.4, P2MP-ID 0x00008173
Multi-Protocol Reach NLRI (14), length: 23, Flags [OE]:
AFI: IPv4 (1), SAFI: Multicast VPN (5)
nexthop: 10.0.0.4, nh-length: 4
8 SNPA
1 bytes
0 bytes
0 bytes
0 bytes
1 bytes
0 bytes
0 bytes
1 bytes
Route-Type: Unknown (0), length: 0
Route-Type: Intra-AS Segment-Leaf (4), length: 255
Update Message (2), length: 30
Multi-Protocol Unreach NLRI (15), length: 3, Flags [OE]:
AFI: IPv4 (1), SAFI: labeled VPN Unicast (128)
End-of-Rib Marker (empty NLRI)
[|BGP Unknown Message Type]
Binary file added tests/bgp-ub.pcap
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