Fix parser #2875
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Fix parser #2875
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1 func (m *BGP4MPHeader) decodeFromBytes(data []byte) ([]byte, error) {
2 if m.isAS4 && len(data) < 8 {
3 return nil, errors.New("not all BGP4MPMessageAS4 bytes available")
4 } else if !m.isAS4 && len(data) < 4 {
5 return nil, errors.New("not all BGP4MPMessageAS bytes available")
6 }
7
8 if m.isAS4 {
9 m.PeerAS = binary.BigEndian.Uint32(data[:4])
10 m.LocalAS = binary.BigEndian.Uint32(data[4:8])
11 data = data[8:]
12 } else {
13 m.PeerAS = uint32(binary.BigEndian.Uint16(data[:2]))
14 m.LocalAS = uint32(binary.BigEndian.Uint16(data[2:4]))
15 data = data[4:]
16 }
17 m.InterfaceIndex = binary.BigEndian.Uint16(data[:2])
18 m.AddressFamily = binary.BigEndian.Uint16(data[2:4])
19 switch m.AddressFamily {
20 case bgp.AFI_IP:
21 m.PeerIpAddress = net.IP(data[4:8]).To4()
22 m.LocalIpAddress = net.IP(data[8:12]).To4()
23 data = data[12:]
24 case bgp.AFI_IP6:
25 m.PeerIpAddress = net.IP(data[4:20])
26 m.LocalIpAddress = net.IP(data[20:36])
27 data = data[36:]
28 default:
29 return nil, fmt.Errorf("unsupported address family: %d",
m.AddressFamily)
30 }
31 return data, nil
32 }
The check at lines 2-6 is sufficient only to safely extract `PeerAS`
and `LocalAS`, after that slice is rebound to the leftover bytes,
i.e., the length of the slice is not 8 or 4 bytes less, depending on
the it is AS4 or not. That means that it could be empty, therefore any
line beyond 16 is vulnerable. E.g., we need to check for at least 4
bytes for lines 17 and 18, and then depending on the address family,
for 12 or 36 bytes.
case EC_SUBTYPE_FLOWSPEC_REDIRECT_IP6: ipv6 := net.IP(data[2:18]).String() localAdmin := binary.BigEndian.Uint16(data[18:20]) return NewRedirectIPv6AddressSpecificExtended(ipv6, localAdmin), nil Note that the `data` length is only checked for being at least 8 bytes, so any message with the given subtype but less than 20 bytes will crash the application.
…length
func (c *CapSoftwareVersion) DecodeFromBytes(data []byte) error {
c.DefaultParameterCapability.DecodeFromBytes(data)
data = data[2:]
if len(data) < 2 {
return NewMessageError(BGP_ERROR_OPEN_MESSAGE_ERROR, BGP_ERROR_SUB_UNSUPPORTED_CAPABILITY, nil, "Not all CapabilitySoftwareVersion bytes allowed")
}
softwareVersionLen := uint8(data[0])
if len(data[1:]) < int(softwareVersionLen) || softwareVersionLen > 64 {
return NewMessageError(BGP_ERROR_OPEN_MESSAGE_ERROR, BGP_ERROR_SUB_UNSUPPORTED_CAPABILITY, nil, "invalid length of software version capablity")
}
c.SoftwareVersionLen = softwareVersionLen
c.SoftwareVersion = string(data[1:c.SoftwareVersionLen]) // ivg: note the crash is here
return nil
}
Notice that `softwareVersionLen` is not checked for `0`, so
`data[1:c.SoftwareVersionLen]` becomes `data[1:0]`, which leads to a
runtime panic.
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