Internet Attacks: The Gory Details Bill Cheswick

1
Internet Attacks The Gory DetailsBill Cheswick

• ches_at_lumeta.com

2
(No Transcript)
3
Some Internet BasicsInternet communication
Client
Server
Application level
TCP/UDP
IP
Hardware
Internet
4
Some Internet BasicsInternet communication
Client
Server
Application level
TCP/UDP
IP
Hardware
Internet
5
Some Internet BasicsInternet communication
6
Application level

• Talks to a host with some protocol
• Examples
• SMTP, POP3, IMAP (mail)
• telnet, rlogin (login)
• HTTP (web access)
• DNS (name service)
• RIP, BGP4, OSPF (routing)
• NFS, SMB (network file access)
• Any one can invent a new protocol between two
  hosts.

7
TCP

• TCP supplies a reliable connection to the other
  end
• Sets up circuit between client and server
• Breaks a stream of data into packets
• Reassembles packets into a stream
• Services 1 - 65535

8
UDP

• Connectionless messages
• No error correction
• No flow control
• Suitable for some network services that dont
  have to be reliable, like voice
• Services are numbered
• 1-65535
• As a rule, its connectionless-nature makes it
  dangerous

9
IP

• Packets have limited sizes
• May be dropped in transit if congestion
• May arrive out of order
• May be duplicated
• Addressing by IP number
• Currently using IP Version 4
• Version 6 is dubious
• IP/SEC gives authentication and/or encryption
• May be tunneled

10
ICMP

• Provides various controls and auxiliary
  functions
• ping
• ping replies
• TTL time exceeded
• source quench (TCP only)
• net unreachable
• host unreachable
• packet filtered

11
TCP/IP stack is hard to do

• 25,000 lines of code is typical
• RFCs dont give all the details
• It takes practice and experience to get it right
• Learning curve is still evident in Linux and
  Microsoft

• Usually kernel-level code debugging is tedious
• Hard to debug error states in a protocol
• crashme attacks
• send random packets with valid checksums
• IP options
• TCP reassembly

12
Hardware level

• Sniffable if on same net.
• There are attacks that fiddle at this level

Ethernet, ATM, wireless
13
InternetWeaknesses
14
The Internet

• Ad hoc collection of TCP/IP interconnections
• No real central authority
• No central knowledge of connections
• maybe flows, but not yet
• No per-packet billing, in most places
• Core equipment too busy to help law enforcement
• Large perimeters are impossible to control

15
Remote Attacks, and anonymity, are easy

• Attacks can be laundered through many hosts
  around the world
• brief attacks are hard to track down
• the average defender is clueless

16
Traceback can be very hard

• clueless ISPs
• ignorant law enforcement
• treaties with foreign countries
• may not be against the local law

• attacker may cease attack before traceback is
  completed

17
Monoculture

• Small set of target types and versions
• Microsoft OS and applications
• Apache
• Samba
• DNS
• Cisco IOS
• Like planting Kansas with a single strain of
  wheat, or vineyards with a single root stock

18
Attacking scripts are published and shared

• Loners develop attack software for the rest of us
• Hacking FAQs are common
• Software tools are easily available
• look up rootkit
• Script kiddies are a major source of current
  Internet attacks

19
Unsafe Services

• Useful
• Poorly written
• Poor auditing
• Found in most hosts
• Safer services and protocols are rare
• Vendors sell flawed software
• Users dont fix holes
• Host-based security is usually broken

• Security requires discipline not found in market
  leaders
• And often not found in open source software either

20
Unsafe ServicesSome Typical Errors

• Unchecked user input submitted to the shell or
  Perl
• wildcard and escape characters take over the
  process
• CGI scripts
• Secret options, commands, or back doors
• DEBUG and others in sendmail

• Input string length is not checked
• string buffer overrun corrupts stack
• strcpy, gets, sprintf
• caller supplies assembly code, and jumps to it
• finger (Morris worm)
• early Netscape
• statd (latest)

21
Unsafe Services Privileged programs are much too
large

• Sendmail is tens of thousands of lines of complex
  code, running as root.
• Netscape browser/communicator is huge
• Operating systems are huge
• Windows
• Unix
• Features are never retired, only added
• A short, simple program is hard to get right

22
Unsafe Protocols

• Passwords transmitted in the clear
• Challenge/response is better, though subject to
  dictionary attacks
• EKE can hide this
• Machine generated passwords are better, but
  require devices or printouts
• Address-based authentication
• Can be OK in controlled environments
• DNS and routing attacks can fool these

23
Weakest Link Compromisesmany targets

• Vulnerabilities are common in network services
• One break-in compromises
• the rest of the host
• the hosts net (via sniffers)
• trusting hosts

• non-vital targets may be vital

24
How Do They Find Dangerous Ports?

• Port scanners
• Easy to write
• Half-open (SYN-only) scanners often dont show up
  in logs
• Harder to scan for UDP services, but not by much
• Firewalking can scan through a firewall
• Uses packets that a firewall often admits, such
  as ICMP or TCP SYN/ACK

25
Attacks

• Stack Smashing

26
Programs dont check their input

• Routines like gets, strcpy, and sprintf, which
  are inherently dangerous
• If input length is too long, it can overwrite
  memory in C, overwriting variables and subroutine
  return addresses.
• Every piece of external data must be checked
  before it is used.
• It doesnt hurt to check internal stuff, too
• assert.h
• CPU time is cheap

27
A Stack before a procedure call
Variables
28
A Stack while a procedure is running
Where to go after the procedure is finished
29
A Stack while a procedure is running
Input line goes in here
30
A Stack while a procedure is running
Input line goes in here
31
Stack smashing attack
New return address, points to...
32
Stack smashing attack
new code loaded in some space on the stack
The code runs with the privileges of the
attacked program, usually root
33
Some former victims of stack-smashing attacks

• Fingerd (Morris worm)
• sendmail
• syslogd
• rstatd
• early Netscape browsers
• file names in attachments to mail
• sshd

• IIS web server

34
Attacks

• Portable Programs

35
Dangerous servicesportable programs

• JAVA
• ActiveXHHHHHHHCOMXHHHHSOAP
• Viruses
• PC
• Word
• Excel

36
Where do Programs Run?
37
Where do Programs Run?
This model is wrong!
38
Applets run in an incompletely-defined
environment
Kernel
Program
39
Javas sandbox

• Is incompletely defined
• Can be different for each vendor
• Often optimized for speed, not security

• Allows native methods, which can break the
  security model
• ActiveX
• like Java, but no sandbox at all

40
Attacks

• Sniffing attacks (eavesdropping)

41
Host withTCP Services
Client
Server
Attacker
42
Ethernet and Passwords

• Was never secure from eavesdropping
• Sniffing tools are common
• grab host name, user name, and password
• check any hacker collection
• Credit card numbers are easy

• Over 1,000,000 captured in 1994
• It doesnt matter how good your password is if it
  can be sniffed!
• Still in wide use - even for root!

43
Wireless passwords
44
Wireless passwords
45
Attacks

• IP Spoofing a trusted host

46
IP Spoofing

• Defeats address-based authentication
• i.e. rlogin, rsh, tcp wrappers
• Common tools available to the hackers
• they dont have to be TCP/IP experts
• This was used to crack Tsutomu Shimomuras
  machines in Takedown.
• Robert Morris Jr. wrote a paper on this in 1984
• Steve Bellovin republished it in 1989
• First known use in 1994

47
Normal TCP connection,initial SYN packet
Client
Server
SYN,SEQ0
48
Response to Open, connection is half open
Client
Server
SYN,SEQ0
SYN,ACK, SEQ01,SEQ0
49
Client completes handshake, TCP connection is now
open
Client
Server
SYN,SEQ0
SYN,ACK, SEQ01,SEQ0
ACK, SEQ01,SEQ01
50
IP Spoof of a Trusted Client Determine Likely SEQ0
Client
Server
Attacker
51
IP Spoof of a Trusted ClientSuppress the Trusted
Client
Client
Server
killer packet or SYN attack
Attacker
52
IP Spoof of a Trusted ClientSuppress the Trusted
Client
Client
Server
Attacker
53
Attacker opens connection from trusted client
Client
Server
SYN,SEQ0
Attacker
54
Open seems to come fromtrusted client
Client
Server
SYN,SEQ0
Attacker
55
IP Spoof of a Trusted ClientServer responds to
dead client
Client
Server
SYN,ACK, SEQ01,SEQ0
Attacker
56
IP Spoof of a Trusted ClientSpoof final open
message
Client
Server
ACK, SEQ01,SEQ01
Attacker
57
IP Spoof of a Trusted ClientOpen is complete
Client
Server
Attacker
58
IP Spoof of a Trusted ClientOpen Server to
outside access
Client
Server
evil trusted command
Attacker
59
Preventing IP spoofing

• Spoofing can be stopped at the perimeter
• No internal addresses accepted from the outside
• Helps to have a coherent address space
• A firewall can prevent access also
• Address-based authentication is a BAD IDEA.

60
Attacks

• TCP hijacking

61
Attacker is watching an existing connection,
perhaps through the strong authentication stage
Client
Server
Attacker
62
Kill the client connection...
Client
Server
killer packet
Attacker
63
and continue the connection
Client
Server
Attacker
64
TCP hijacking

• Takes over an existing, authenticated connection
• Needs access to the packet flow
• Common tools are available to the hackers now
• Cryptographic signatures of packets can defeat
  this

65
Attacks

• Denial of Service

66
Host withTCP Services
Client
Server
Attacker
67
Denial-of-service Attacks

• In your face - not subtle like traditional
  hacking attacks
• Random packets are very hard to trace
• Can go on for weeks
• Attackers can exploit poor local software or...
• Simply flood the sites network with incoming
  packets
• These attacks are always possible on a public
  service

68
Attacks

• Denial of Service SYN packet attacks

69
Normal TCP open
Client
Server
SYN,SEQ0
SYN,ACK, SEQ01,SEQ0
ACK, SEQ01,SEQ01
70
Normal TCP open
Client
half-open lt300ms
71
SYN Attacks

• First seen at Panix.com in fall 1996
• Half-open processing was implemented poorly
• Quadratic behavior
• Wasnt much call for improving it
• Weve been expecting it
• The only thing we left out of our firewalls book
• Removed at the last minute
• We knew of no good solution
• We are sorry we left it out

• A new one appeared in fall 1997
• SYN with same source and destination address
  kills some TCP/IP implementation
• There will be more attacks on TCP/IP
  implementations
• lots of code involved
• hard to test code in a kernel

72
Attacks

• Denial of Service
• Ping flood (smurf)

73
Identify ping generatornetworks
G
G
target
G
G
G
G
74
Trigger packets withspoofed return address
G
G
target
G
G
G
G
packet cannon
75
Generators flood the targetwith packets
G
G
target
G
G
G
G
packet cannon
76
Traceback

• The target cannot tell where the trigger is
  coming from
• Attacking hosts may not know that they are being
  used
• Broadcast storms can generate more load

77
Attacks

• DNS, routing, and infrastructure attacks

78
Routing attacksPacket Diversion and
man-in-the-middle attacks
Client
Server
Attacker
79
Routing attacksPacket Diversion and
man-in-the-middle attacks
Client
Server
(router)
Attacker
80
Routing attacksPacket Diversion and
man-in-the-middle attacks
Client
Server
(router)
Attacker
81
DNS attacks

• Include an extra glue record on a DNS query
• short cache time-out hides the evidence
• newest bind program checks for this
• DNS cache poisoning
• Capture DNS server and return incorrect result
• DNSSEC can fix this
• going through final comments now

82
Infrastructure attacks

• Our tools are still weak
• authenticated SBGP4 is coming, maybe
• Keep up with the latest name server
• Move to secure router implementations, when
  available
• Question what will you do if the entire
  Internet is down for a week?

83
Attacks

• Social Engineering
• (a.k.a. spying)

84
Social Engineering (cont.)
Click here to infect your computer.
85
Another problem with strange programs
86
Social Engineering
Hello, this is Dennis Ritchie calling. Im in
Israel now and I have forgotten my
password. Hello, ltadmin-namegt, Ive
just started work here. ltBoss-namegt said I
should have an account on lttarget-hostgt
87
Attacks

• Unsafe services

88
Host withTCP Services
Client
Server
Attacker
89
Host withTCP Services
Client
Server
Attacker
90
Default servicesSGI workstation
ftp stream tcp nowait root
/v/gate/ftpd telnet stream tcp nowait root
/usr/etc/telnetd shell stream tcp
nowait root /usr/etc/rshd login stream tcp
nowait root /usr/etc/rlogind exec
stream tcp nowait root /usr/etc/rexecd
finger stream tcp nowait guest
/usr/etc/fingerd bootp dgram udp wait
root /usr/etc/bootp tftp dgram udp
wait guest /usr/etc/tftpd ntalk dgram
udp wait root /usr/etc/talkd tcpmux
stream tcp nowait root internal echo
stream tcp nowait root internal discard
stream tcp nowait root internal chargen
stream tcp nowait root internal daytime
stream tcp nowait root internal time
stream tcp nowait root internal echo
dgram udp wait root internal discard
dgram udp wait root internal chargen
dgram udp wait root internal daytime
dgram udp wait root internal time
dgram udp wait root internal sgi-dgl
stream tcp nowait root/rcv dgld uucp
stream tcp nowait root
/usr/lib/uucp/uucpd
91
More default services
mountd/1 stream rpc/tcp wait/lc root
rpc.mountd mountd/1 dgram rpc/udp wait/lc
root rpc.mountd sgi_mountd/1 stream rpc/tcp
wait/lc root rpc.mountd sgi_mountd/1 dgram
rpc/udp wait/lc root rpc.mountd rstatd/1-3
dgram rpc/udp wait root rpc.rstatd
walld/1 dgram rpc/udp wait root
rpc.rwalld rusersd/1 dgram rpc/udp wait
root rpc.rusersd rquotad/1 dgram rpc/udp
wait root rpc.rquotad sprayd/1 dgram
rpc/udp wait root rpc.sprayd
bootparam/1 dgram rpc/udp wait root
rpc.bootparamd sgi_videod/1 stream rpc/tcp wait
root ?videod sgi_fam/1 stream
rpc/tcp wait root ?fam
sgi_snoopd/1 stream rpc/tcp wait root
?rpc.snoopd sgi_pcsd/1 dgram rpc/udp wait
root ?cvpcsd sgi_pod/1 stream rpc/tcp
wait root ?podd tcpmux/sgi_scanner
stream tcp nowait root ?scan/net/scannerd tcp
mux/sgi_printer stream tcp nowait root
?print/printerd 9fs stream tcp
nowait root /v/bin/u9fs u9fs webproxy
stream tcp nowait root
/usr/local/etc/webserv
92
Some Dangerous Services

• Telnet
• FTP
• NFS
• RPC
• secure RPC
• rlogin/rsh/rcp
• X11

• DNS
• (web servers)

93
Why are they insecure?telnet

• Eavesdropping attacks sniff passwords
• gt1,000,000 sniffed in 1994 from hacked ISPs
• TCP hijacking takes over authenticated
  connections strong passwords arent enough
• Insecure accounts are subject to probes and use
• Corruption of client host compromises the session

94
Why are they insecure?FTP

• Same as telnet, plus
• history of bugs in servers
• setup errors for anonymous FTP
• get permissions wrong
• distribute the real password file to the masses
• why

95
Why are they insecure?NFS

• Root file handle can be sniffed
• Relies on RPC software

96
Why are they insecure?RPC and secure RPC

• RPC
• address-based
• local relay feature can obscure address
  information from the server

• Secure RPC
• cryptographically weak

97
Why are they insecure?Rlogin, rsh, rcp

• rlogin, rsh, rcp
• can be hijacked
• can be spoofed
• use addressed-based authentication
• .rhosts and /etc/hosts.equiv leak trusted host
  information
• .rhosts users should not be making security
  policy

98
Why are they insecure?X11

• Clear text leaks secrets
• Cookie authentication is in the clear
• Advanced authentication not widely available
• xhost configuration errors
• Historically, bugs in xdm

99
Why are they insecure?DNS - domain name system

• Bind runs as root
• it is big, and not well understood
• runs on vital hosts
• Cache poisoning cache wrong answers
• attack address-based auth
• spoof servers

100
DNS lookupA asks D for Bs IP address
D
B 1.2.3.4
cache
Server
B -gt 1.2.3.4
A
B?
Client
Attacker
101
DNS lookup D asks B (or someone who knows about
B)
D
B 1.2.3.4
cache
Server
B?
B -gt 1.2.3.4
A
Client
Attacker
102
DNS lookup B answers, D caches the answer, and
tells A
D
B 1.2.3.4
cache
Server
B -gt 1.2.3.4
B -gt 1.2.3.4
A
Client
B -gt 1.2.3.4
Attacker
103
DNS lookupA uses the answer
D
B 1.2.3.4
cache
Server
B -gt 1.2.3.4
B -gt 1.2.3.4
A
Client
X 5.6.7.8
Attacker
104
DNS lookup D remembers the answer for a given
period
D
B 1.2.3.4
cache
Server
B -gt 1.2.3.4
B -gt 1.2.3.4
A
Client
X 5.6.7.8
Attacker
105
DNS cache poisoning attackAttacker C arranges
for D to ask him a question
D
B 1.2.3.4
cache
Server
B -gt 1.2.3.4
A
X?
Client
X 5.6.7.8
Attacker
106
DNS cache poisoning attackAttacker C arranges
for D to ask him a question
D
B 1.2.3.4
cache
Server
B -gt 1.2.3.4
A
Client
X?
X 5.6.7.8
Attacker
107
DNS cache poisoning attack The attacker gives an
answer, plus
D
B 1.2.3.4
cache
Server
X -gt 5.6.7.8
B -gt 5.6.7.8
B -gt 1.2.3.4
A
Client
X 5.6.7.8
Attacker
108
DNS cache poisoning attackA gets his answer,
and uses it
D
B 1.2.3.4
cache
Server
X -gt 5.6.7.8
B -gt 5.6.7.8
B -gt 1.2.3.4
A
Client
X 5.6.7.8
X -gt 5.6.7.8
Attacker
109
DNS cache poisoning attackThe cache has an
extra answer
D
B 1.2.3.4
cache
Server
X -gt 5.6.7.8
B -gt 5.6.7.8
B -gt 1.2.3.4
A
Client
X 5.6.7.8
Attacker
110
DNS cache poisoning attackNow A asks for Bs
address
D
B 1.2.3.4
cache
Server
X -gt 5.6.7.8
B -gt 5.6.7.8
B -gt 1.2.3.4
A
B?
Client
X 5.6.7.8
Attacker
111
DNS cache poisoning attack D knows the answer
already, and returns it
D
B 1.2.3.4
cache
Server
X -gt 5.6.7.8
B -gt 5.6.7.8
B -gt 1.2.3.4
A
Client
X 5.6.7.8
B -gt 5.6.7.8
Attacker
112
DNS cache poisoning attack A uses the answer
D
B 1.2.3.4
cache
Server
X -gt 5.6.7.8
B -gt 5.6.7.8
B -gt 1.2.3.4
A
Client
X 5.6.7.8
B -gt 5.6.7.8
Attacker
113
DNS cache poisoning

• Gives the wrong answer on inverse lookups,
  foiling rsh, rlogin
• If you connect to the wrong site they can
• spoof a login, and capture passwords
• spoof a web page, and give wrong answers
• set themselves up for man-in-the-middle attacks,
  relaying info to the real server

114
DNS cache poisoning

• Older versions of bind fall for this
• You can even send an answer without a query, to
  some implementations!
• DNS responses can be spoofed to
• what if the query gets two answers use the
  first?!
• DNSSEC fixes this

115
Why are they insecure?Web servers

• Complex, and buggy
• stack smashing attacks, etc
• CGI scripts it is always dangerous to add
  programs

• Numerous configuration options
• Apache security relies on good configuration
• Needs access to internal databases

116
Unsafe services SMB

• Protocol uses weak authentication
• samba is big I prefer using chroot

117
Unsafe services Microsoft authentication over
PPTP

• Weak authentication
• Probably weak encryption implementation
• see Bruce Schneiers paper in ACM CCS-5

118
Other services

• POP3 and IMAP
• IRC - no!
• Realaudio
• UDP is dangerous, TCP ok
• Mbone
• hard to gate
• some UDP implementations respond to multicast
  packets

119
Exponential attacks
120
Viruses

• PC viruses
• there are tens of thousands of them, including
  variants
• defense is best made at the host, with a virus
  checker
• update the database often
• Unix viruses
• Tom duff made one
• Shell viruses are easy
• Unix viruses are rare!

121
Viruses

• Firewalls can filter them
• It seems like the right place
• It requires a lot of work, and they can be hidden
• Macro viruses are the most alarming
• They have access to the entire PC, with a little
  work

122
The Morris Worm

• November 2, 1988
• Spread using
• fingerd (stack smashing)
• sendmail (DEBUG back door)
• password guessing
• Poorly controlled exponential growth
• A team of experts fought it quickly

123
Attacks

• Unsafe programs

124
Root the gateway to privilege
find / -perm -4000 -user root -print wc -l
125
Setuid-root
AIX 4.2 242 a staggering
number \\ BSD/OS 3.0 78\\ FreeBSD
4.3 42 someone's guard
machine\\ FreeBSD 4.3 47 2
appear to be third-party\\ FreeBSD 4.5
43 see text for closer analysis \\ HPUX
A.09.07 227 about half may be
special for this host \\ Linux (Mandrake 8.1)
39 3 appear to be third-party \\ Linux
(Red Hat 2.4.2-2) 39 2 third-party
programs \\ Linux (Red Hat 2.4.7-10) 31
2 third-party programs\\ Linux (Red Hat 5.0)
59\\ Linux (Red Hat 6.0) 38 2--4
third-party \\ Linux 2.0.36 26
approved distribution for one university \\ Linux
2.2.16-3 47 \\ Linux 7.2
42\\ NCR Intel 4.0v3.0 113 34
may be special to this host \\ NetBSD 1.6
35 \\ SGI Irix 5.3 83 \\ SGI
Irix 5.3 102 \\ Sinux 5.42c1002
60 2 third-party programs\\ Sun
Solaris 5.4 52 6 third-party
programs\\ Sun Solaris 5.6 74 11
third-party programs\\ Sun Solaris 5.8
70 6 third-party programs\\ Sun Solaris 5.8
82 6 third-party programs\\ Tru64
4.0r878 72 \\
126
Insecure clients

• This is not the same as TCP hijacking
• encryption on the link wont fix this
• any persistent connection is vulnerable
• rlogin, ftp, ssh
• Tsutomu left an rlogin session running when he
  went skiing
• YOU HAVE TO BE ABLE TO TRUST YOUR CLIENT
• laptop PCs vs. terminal rooms

127
Insecure clientsattacker takes over client host
Client
Server
Attacker
128
Insecure clientsattacker takes over client host
Client
Server
Attacker
129
installs the TAP kernel load module
Client
Server
TAP
Attacker
130
user makes authenticated connection to server
Client
Server
TAP
Attacker
131
hacker takes over terminal connection with TAP
Client
Server
TAP
Attacker
132
Weve been losing ground for decades

• Bad guys are figuring out attacks that we have
  been waiting for over the years
• Very few surprises
• Defense has not improved much
• Ssh
• IPsec
• Better Linux and Unix systems

133
How Do We Fix All This?
134
How Do We Fix All This?

• Hide behind a perimeter defense?

135
Firewalls Perimeter defenses
136
Firewalls Not a panacea

• Backdoors usually diminish the effectiveness
• Commercial firewalls are probably OK
• May give community a false sense of security

• The firewall is often the only secure part of a
  configuration
• People go around them
• People go through the bad ones
• No protection from insiders

137
Anything large enough to be calledan intranet
is probably out of control
138
(No Transcript)
139
This was Supposed To be a VPN
140
Some intranet statisticsfrom Lumeta clients
141
You dont know to whom you are connected

• Modems are cheap and easy to hook up.
• Suns fax machines
• Home commuting networks may link to spouses
  company, or the Internet.
• even routing worked!

• Remote managers can make extranet connections
  that arent authorized.
• these connections can be very hard to find
• but the security threat is still there

142
You dont know how many hosts you have

• Most control is at the network level, not the
  host level.
• Name server entries are optional.
• Nobody keeps the reverse name service information
  up-to-date.
• Mapping takes work, and doesnt catch hosts that
  are down
• Some network links are ephemeral.

143
Lucents intranetc. 1997
The Internet
Columbus
Murray Hill
Murray Hill
Holmdel
Allentown
SLIP PPP ISDN X.25 cable ...
Lucent - 130,000, 266K IP addresses, 3000 nets
ann.
thousands of telecommuters
200 business partners
144
None of this protects us from an insider threat,
so
145
How Do We Fix All This?

• Life without a firewall
• skinny dipping

146
Secure computing needs

• Safe clients
• Secure communication
• Safe servers
• Strong, 2-factor authentication
• Something you have and something you know
• Emergency 1-factor authentication, something you
  know, used extremely rarely

147
Safe clients and servers need

• A trustable Trusted Computing Base
• Simple, well-specified and debugged kernel
• Check out the semantics of setuid in Unix flavors
  (Setuid Demystified. Chen, Wagner, and Dean
  Usenix Security 2002)
• MAC controls more permissions, use of file
  system permissions, and programs that know how to
  use them
• root is bad see Multics!)
• Better, more routing sandboxing
• Make chroot much better, and easier

148
Free, new servers by Don Knuth?

• Hes busy with Volume 4
• Literate programming of key servers might be the
  way to go
• Other languages might be better C and C still
  have buffer overflow problems
• Modula 3?
• Java?

149
We need better suspenders

• We should never trust the application writers to
  get it right, though they should try hard
• Jails/chroot/sandboxes need to be easy and
  common-place
• More restrictive jails should be possible
• Unprivileged user should be able to set these up,
  even if he is already in a jail
• The /etc/passwd problem
• Static builds should be easier
• Careful documentation of what a program needs to
  access.

150
Improve chroot

• Already some new work in this area FreeBSD jail
• Goal routine jailing of everything that
  processes external input
• Netscape client routinely jailed
• mail readers
• SpamAssassin
• Openssl (!)
• See Plan 9 for some good ideas
• Network access through the file system?!

151
Related chroot wishes

• Easier builds of static binaries dynamic
  libraries make the TCB tougher to build
• Chroot options to all the useful network
  services they should jail themselves!
• Apache (Ben Laurie is considering this)
• Samba
• Ntp
• DNS (done)

152
Microsoft desperately needs to do this

• I am convinced that they actually are trying to
  get better
• They have a long way to go
• I wonder if they can wedge good sandboxing into
  their OS

153
Simpler Software

• One of the underlying problems with Microsoft
  applications is creeping featurism
• For most uses, is Word much better than WordStar
  or any of the other early word processors?
• Is this version of PowerPoint that much better
  than the first ones (bugs aside)?

154
Simpler Software in Unix

• Skim through the Unix V7 man pages
  (http//plan9.bell-labs.com)
• How many options does cat(1) need?
• How many setuid-to-root programs does your system
  have?

155
New file system switch

• Revisit the DOOFUS wars of the mid 80s
• Check Plan 9 for possible uses
• Kernel file system switch that has userland file
  system computation
• Must be robusthung inodes, etc.
• Does not involve the network, as NFS does
• Reimplement SFS, Samba client, etc.,

156
Communications
157
Communication encryption options

• Ssh
• IPsec
• SSL

158
Communications solutions ssh

• Source code is available
• Widely examined
• But 2 protocol flaws found so far
• stack smashing scare
• Tunneling is valuable
• IPsec has better crypto, maybe

159
IPsec

• Protocol well-vetted by expert community
• We have the CPUs, I want everyone to use it, for
  all communications
• Needs simpler setup
• Microsoft requires certificates, no?
• Secret key pairs are fine for small setups
• Key exchange daemons worry me
• They gotta run as root, no?
• They can use complicated crypto libraries, and
  are exposed network services

160
SSL

• Well-documented and ver. 3 is probably ok
• Implemented by openssl
• which uses X.509
• which uses ASN.1
• which is complicated, a monoculture, and has had
  several bugs exposed
• Can you jail the SSL parts of your web server?
  (I have sslwrap chroot)

161
Authentication
162
Security doesnt need to be inconvenient

• Modern hotel room keys
• Modern car keys

163
Some solutionsHardware tokens

• SecureID
• time-based
• S/Key
• software or printout solution
• Many others
• usually proprietary server software
• New USB dongles are just the ticket!

Digital Pathways SNK-004
164
One-time Passwords
RISC/os (inet) Authentication Server. Id?
ches Enter response code for 70202
04432234 Destination? cetus
165
How does it work? Server and client share a
secret key
Client
Server
166
How does it work? Server generates a unique
challenge
Client
Server
70202
challenge
167
How does it work? The client encrypts the
challenge with key
Client
Server
70202
168
How does it work?and returns the result
Client
Server
70202
04432234
169
How does it work?The server checks the result
Client
Server
70202
04432234
04432234
170
One-time passwords

• The client proves he has the key, without
  revealing it
• With hardware, he may not even know the key
• the keys are computer-generated
• no weak passwords
• If the challenges dont repeat, an eavesdropper
  cant predict the answer, unless the encryption
  (DES) is broken

171
One-time passwords

• The key can be generated from a password but the
  challenge/response pair is subject to a
  dictionary attack
• This extra work for the user is worth the effort
• very strong authentication
• spies use this
• needs about a page of C code
• can be implemented in a remote authentication
  server

172
Human-computed one-time password a research
project
challenge 00193 Wed Sep 11 112209
2002 response ab0dh1kd0jkfj1kye./
173
Not Gory Enough For You?

• Bugtraq mailing list
• Firewalls and Internet Security
• Chapman and Zwicky
• Keyword search in search engines for hacking
  tools
• rootkit

174
(No Transcript)
175
Questions

• http//research.lumeta.com/ches/
• ches_at_lumeta.com
• Yes, Id love to sign your book