Question

我正在尝试使用Scapy发送具有BGP层的数据包

我目前陷入了这个问题的基本部分，因为我无法设置BGP层。我按照说明设置了常规IP和TCP层。

例如：

>>a=IP(src="192.168.1.1",dst="192.168.1.2")/TCP(sport=179,dport=50)

但是当我这样做时会出现问题：

>>a=a/BGP()
NameError: name BGP is not defined

我在Scapy Github（https://github.com/secdev/scapy/blob/9201f1cf1318edd5768d7e2ee968b7fba0a24c5e/scapy/contrib/bgp.py）的contrib文件中看到了BGP实现，所以我认为Scapy确实支持BGP实现

我是网络新手，所以我想知道你是否可以帮我设置BGP层

感谢您花时间阅读本文！

Answer 1

在这里尝试帮助。我对BGP类型数据包没有经验，但是......我将你提供的链接中的bgp.py文件复制到scapy / layers中。使用ls（）我发现了以下内容：

BGPAuthenticationData : BGP Authentication Data
BGPErrorSubcodes : BGP Error Subcodes
BGPHeader  : BGP header
BGPNotification : BGP Notification fields
BGPOpen    : BGP Open Header
BGPOptionalParameter : BGP Optional Parameters
BGPPathAttribute : BGP Attribute fields
BGPUpdate  : BGP Update fields

然后我可以使用say ls（BGPUpdate）来显示：

withdrawn_len : ShortField           = (None)
withdrawn  : FieldListField       = ([])
tp_len     : ShortField           = (None)
total_path : PacketListField      = ([])
nlri       : FieldListField       = ([])

并且能够创建此数据包：

pkt = pkt = IP()/TCP()/BGPUpdate()
pkt.show()
###[ IP ]###
  version   = 4
  ihl       = None
  tos       = 0x0
  len       = None
  id        = 1
  flags     = 
  frag      = 0
  ttl       = 64
  proto     = tcp
  chksum    = None
  src       = 127.0.0.1
  dst       = 127.0.0.1
  \options   \
###[ TCP ]###
     sport     = ftp_data
     dport     = http
     seq       = 0
     ack       = 0
     dataofs   = None
     reserved  = 0
     flags     = S
     window    = 8192
     chksum    = None
     urgptr    = 0
     options   = {}
###[ BGP Update fields ]###
        withdrawn_len= None
        withdrawn = []
        tp_len    = None
        \total_path\
        nlri      = []

我不确定所有不同类型的BGP层/数据包的用途或社区号码的设置位置。可能在BGPPathAttribute（type = x）中。类型5是＆＃34; LOCAL_PREF＆＃34;这可能对应于社区价值观。试试这个Link.

pkt = BGPPathAttribute(type=5)
pkt.show()
###[ BGP Attribute fields ]###
  flags     = Transitive
  type      = LOCAL_PREF
  attr_len  = None
  value     = ''

无论如何，希望有所帮助。

编辑：忘记。我还添加了＆＃34; bgp＆＃34;到scapy / config.py的load_layers部分。第373行。像这样：

   load_layers =  ["l2", "inet", "dhcp", "dns", "dot11", "gprs", "hsrp", "inet6", "ir", "isakmp", "l2tp",
               "mgcp", "mobileip", "netbios", "netflow", "ntp", "ppp", "radius", "rip", "rtp",
               "sebek", "skinny", "smb", "snmp", "tftp", "x509", "bluetooth", "dhcp6", "llmnr", "sctp", "vrrp",
               "ipsec","bgp"]

Answer 2

我们希望使用scapy的BGP层。 BGP通过TCP传输时。因此，我们必须有一个已建立的（3 way handshake）tcp套接字。 TCP通过IP传输。因此，我们可以用以下格式表示完整的数据包。

packet = IP Layer / TCP Layer / BGP Layer
但是BGP本身分为两个部分，即BGP标头和BGP有效负载（例如：OPEN，UPDATE，etc）。因此，上面的层表示如下。

packet = IP Layer / TCP Layer / BGP Header / BGP payload
此处的BGP标头指定了BGP有效负载的身份验证，长度和类型。为了表示整个情况，我们可以执行以下练习。（我在这里假设您已经建立了TCP套接字。）

from scapy.layers.inet import IP, TCP
from scapy.contrib.bgp import BGPHeader, BGPUpdate, BGPPathAttr, BGPNLRI_IPv4

base = IP(src=src_ipv4_addr, dst=dst_ipv4_addr, proto=6, ttl=255)  # proto=6 represents that, TCP will be travelling above this layer. This is simple IPV4 communication.
tcp = TCP(sport=established_port, dport=179, seq=current_seq_num, ack=expected_seq_num, flags='PA'])  # dport=179 means, we are communicating with bgp port of the destination router/ host. sport is a random port over which tcp is established. seq and ack are the sequence number and acknowledgement numbers. flags = PA are the PUSH and ACK flags.
hdr = BGPHeader(type=2, marker=0xffffffffffffffffffffffffffffffff)  # type=2 means UPDATE packet will be the BGP Payload, marker field is for authentication. max hex int (all f) are used for no auth.
up = BGPUpdate(path_attr=[BGPPathAttr(type_flags=64, type_code=5, attribute=BGPPALocalPref(local_pref=100))], nlri=BGPNLRI_IPv4(prefix=NLRI_PREFIX))      # update packet consist of path attributes and NLRI (Network layer reachability information),  type_code in path attributes is for which type of path attribute it is. [more][3]

packet = base / tcp / hdr / up
packet.show2()

使用以下变量值（出于示例目的）。

src_ipv4_addr = '10.110.99.2'  # eth0
dst_ipv4_addr = '10.110.99.50'
established_port = 1223
expected_seq_num=1000 # ack
current_seq_num=1500 # seq
NLRI_PREFIX = '10.110.99.0/24'

输出将紧随其后。

###[ IP ]### 
  version   = 4
  ihl       = 5
  tos       = 0x0
  len       = 74
  id        = 1
  flags     = 
  frag      = 0
  ttl       = 255
  proto     = tcp
  chksum    = 0xe09c
  src       = 10.110.99.2
  dst       = 10.110.99.50
  \options   \
###[ TCP ]### 
     sport     = 1223
     dport     = bgp
     seq       = 1500
     ack       = 1000
     dataofs   = 5
     reserved  = 0
     flags     = PA
     window    = 8192
     chksum    = 0x102d
     urgptr    = 0
     options   = []
###[ HEADER ]### 
        marker    = 0xffffffffffffffffffffffffffffffff
        len       = 34
        type      = UPDATE
###[ UPDATE ]### 
           withdrawn_routes_len= 0
           \withdrawn_routes\
           path_attr_len= 7
           \path_attr \
            |###[ BGPPathAttr ]### 
            |  type_flags= Transitive
            |  type_code = LOCAL_PREF
            |  attr_len  = 4
            |  \attribute \
            |   |###[ LOCAL_PREF ]### 
            |   |  local_pref= 100
           \nlri      \
            |###[ IPv4 NLRI ]### 
            |  prefix    = 10.110.99.0/24

使用Scapy设置BGP层

2 个答案: