Web Security - PowerPoint Presentation

Slide1

Web Security

CS598MCC Spring 2013

Yiwei

YangSlide2

Definition

a set of procedures, practices, and technologies for assuring the reliable, predictable operation of web servers, web browsers, other programs that communicate with web servers, and the surrounding Internet infrastructure.Slide3

Three components

Data in transit

Web Browser

Web

ServerSlide4

Privacy issue with web browser

Where does information leak out?

1. Provided by users (registration form)

2. Log files

- Web logs (IP, time, requested URL, browser type,

username if authentication is used …) proxy servers can obscure web log - Mail logs (from, to, …)

- DNS logs (name, IP, query…) - RADIUS logs Slide5

Privacy issue with web browser

Where does information leak out?

3. Web bugs

<

img src=“ … “width=1 height=1 border=0 />

outsourced web site monitoring 4. Cookie - user’s actual data

- a number of codes that key into a database that resides at the web provider Slide6

Privacy issue with web browser

Attacks related with cookies

1.XSS(Cross-site scripting)

-

Nonpersistent - Persistent Prevention

- Better cookie handling - Disable the script Slide7

Privacy issue with web browser

Attacks related with cookies

2. CSRF(

Cross-Site Request Forgery)

- belongs to Deputy attack - carried out attack from user

himself Prevention

- Better cookie handling - Authentication for each operation - Random numberSlide8

RADIUS(

Remote Authentication Dial In User Service

)

Application layer client/server protocol on top of UDP Authentication, Authorization, Accounting (AAA)

RADIUS Server - daemon process running on Unix or Window NT machineRADIUS Client - access server(gateway) that control access to network( RAS, NAS, VPN server)Slide9

Radius Packet formatSlide10

Authentication and Authorization

1.User initiates authentication to the NAS.

2.NAS prompts for username and password.

3.User replies.

4.RADIUS client sends username and encrypted password to the

RADIUS server.5.RADIUS server responds with Accept, Reject, or Challenge.6.The RADIUS client acts upon services and services parameters bundled with Accept or Reject. Slide11

Client sends out access-request packet

-

request authenticator is a random 16 octet string

- password is encrypted p is divided into p1

,p2,…..pn where pi

is a 16-octet block c1 = p1 XOR MD5(S || request authenticator )

c2 = p2 XOR MD5(S || c1 ) …….

cn = p

n

XOR MD5(S || c

n-1

)

- sent to port 1812 of server

Authentication and AuthorizationSlide12

Server received the packet

Drop it if no shared secret

Otherwise authenticate the user

- access-accept( parameters used for this session including access list to apply)

- access-reject - access-challenge response authenticator = MD5 (code || ID|| length|| request authenticator|| attributes || s)

Send out the packet to client

Authentication and AuthorizationSlide13

Client drop the packet if it doesn’t have corresponding identifier or calculation on response authenticator doesn’t match

Otherwise the user is authenticated if received access-accept

What can go wrong?

Authentication and AuthorizationSlide14

Attacks on RAIDUS

Response Authenticator Based Shared Secret Attack

User-Password Attribute Based Shared Secret Attack

User-Password Based Password Attack

Active User-Password Compromise through Repeated Request AuthenticatorsWe need to secure the trafficSlide15

AccountingSlide16

Secure Network Connection

Cryptographic protocol

Offline encryption communication protocol

-PGP/

OpenPGP, S/MIMEOnline encryption communication protocol -SSL, IPsec, Kerberos, SET, SSH Slide17

SSL(Secure Sockets Layer)Slide18

SSL Record Protocol Slide19

Handshake Protocol: Phase 1 and 2 Slide20

SSL: Handshake Round 1

Client

Server

{

v

C

||

r

1

||

s

1

||

ciphers

||

comps

}

Client

Server

{

v

||

r

2

||

s

1

||

cipher

||

comp

}

v

C

Client’s version of SSL

v

Highest version of SSL that Client, Server both understand

r

1

,

r

2

nonces (timestamp and 28 random bytes)

s

1

Current session id (0 if new session)

ciphers

Ciphers that client understands

comps

Compression algorithms that client understand

cipher

Cipher to be used

comp

Compression algorithm to be usedSlide21

SSL: Handshake Round 2

Client

Server

{

certificate

}

Note: if Server not to authenticate itself, only last message sent; third

step omitted if Server does not need Client certificate

k

S

Server’s private key

ctype

Certificate type requested (by cryptosystem)

gca

Acceptable certification authorities

er2

End round 2 message

Client

Server

{

mod

||

exp

|| Sig

S

(

h

(

r

1

||

r

2

||

mod

||

exp

)) }

Client

Server

{

ctype

||

gca

}

Client

Server

{

er2

}Slide22

Handshake Protocols: Phases 3 and 4 Slide23

SSL: Handshake Round 3

Client

Server

{

pre

}Pub

S

msgs

Concatenation of previous messages sent/received this handshake

opad

,

ipad

As above

Client

Server

{

h

(

master || opad || h

(

msgs || master | ipad

)) }

Both Client, Server compute master secret

master

:

master

= MD5(

pre

|| SHA(‘A’ ||

pre

||

r

1

||

r

2

) ||

MD5(

pre

|| SHA(‘BB’ ||

pre

||

r

1

||

r

2

) ||

MD5(

pre

|| SHA(‘CCC’ ||

pre

||

r

1

||

r

2

)

Client

Server

{

client_cert

}Slide24

SSL: Handshake Round 4

Client

Server

{

h

(

master || opad || h

(

msgs ||

0x434C4E54

|| master || ipad

)) }

msgs

Concatenation of messages sent/received this handshake in

previous

rounds (does notinclude these messages)

opad

,

ipad

,

master

As above

Client

Server

{

h

(

master || opad || h

(

msgs || 0x53525652 || master | ipad

)) }

Server sends “change cipher spec” message using that protocol

Client

Server

Client sends “change cipher spec” message using that protocol

Client

ServerSlide25

SSL

What does SSL provide us?

- Data integrity, Confidentiality

- Authentication(handshake)Limitation on SSL - doesn’t work with connection less protocol - doesn’t support non-repudiation

- doesn’t protect the application itself - general-purpose data securityMisuse of SSL Slide26

TLS(Transport Layer Security)

SSL 3.0 served as the basis for TLS 1.0(SSL 3.1)

Slightly different from SSL

- Message Authentication (HMAC)

- key derivation - Finished -Alert protocol message typeSlide27

Secure Web Server

Based on CIA, what do we need to secure?

Three steps to secure server

1. Host security 2. Secure web service

3. Examine interaction between OS and web service Slide28

References

RADIUS

http://en.wikipedia.org/wiki/RADIUS

http://www.cisco.com/en/US/tech/tk59/technologies_tech_note09186a00800945cc.shtml

SSLhttps://wiki.engr.illinois.edu/download/attachments/202934655/ssl-ipsec.pdf?version=1&modificationDate=1348193253000Slide29

Thank you!