Bryan Sullivan Senior Security Program Manager …ipma-wa.com/prof_dev/2010/SDLforManagedCode.pdf · Bryan Sullivan. Senior Security Program Manager. ... Guide product teams to ...

Bryan SullivanSenior Security Program Manager

Microsoft Corporation

Agenda

Introduction to the SDLSecure coding practices for ASP.NET and the OWASP Top 10SDL tools demonstrationsSDL-Agile (if we have time and interest…)

Cybercrime evolution

LANs First PC virusMotivation: damage

1986–1995

Internet Era “Big Worms”Motivation: damage

1995–2003

OS, DB attacksSpyware, SpamMotivation: Financial

2004+

Targeted attacksSocial engineeringFinancial + Political

2006+

Attacks are focusing on applications

Calculated from the Microsoft Security Intelligence Report V6

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

% of vulnerability disclosures:Operating system vs browser and application

vulnerabilities

OS vulns Browser vulns Application vulns

Most vulnerabilities are in smaller organizations’ applications

11%89%

Vendors' accountability for vulnerabilities

Top 5 ISVsOthers

Sources: IBM X‐Force 2008 Security Report

The Microsoft SDL

Administer and track security training

IncidentResponse (MSRC)

Sign up with SECDefine business ownerDefine security lead

Define product-specific security measures Meet SDL requirements

Guide product teams to meet SDL requirements

Security engineeringFeedback for SDL improvements

Establish release criteria and sign-off as part of FSR

Meetrelease criteria

Ongoing Process Improvements

Education Process Accountability

Training Requirements Design Implementation Verification Release ResponseTraining Requirements Design Implementation Verification Release Response

Phases of the SDL

Windows: 45% reduction of vulnerabilities

Source: Windows Vista One Year Vulnerability Report, Microsoft Security Blog 23 Jan 2008

11966

400

242

157

Windows XP Windows Vista OS I OS II OS III

Total vulnerabilities disclosed one year after release

Before SDL After SDL

45% reduction in vulnerabilities

http://blogs.technet.com/security/archive/2007/11/30/download-internet-explorer-and-firefox-vulnerability-analysis.aspx

Microsoft SDL and SQL Server

Sources: Analysis by Jeff Jones (Microsoft technet security blog)

34

3

187

SQL Server 2000 SQL Server 2005 Competing commercial DB


91% reduction in Vulnerabilities

Total Vulnerabilities Disclosed 36 Months After Release


Microsoft SDL and Internet Explorer (IE)

Source: Browser Vulnerability Analysis, Microsoft Security Blog 27-NOV-2007

18 14

8

3

Internet Explorer 6 Internet Explorer 7

Medium High


35% reduction in vulnerabilities63% reduction in high severity vulnerabilities

Vulnerabilities Fixed One Year After Release


Secure Software Development Requires Process Improvement

Simply “looking for bugs” doesn’t make software secure

Must reduce the chance vulnerabilities enter into design and code

Requires executive commitment

Requires ongoing process improvement

Requires education & training

Requires tools and automation

Requires incentives and consequences

OWASP Top 10

InjectionCross-Site ScriptingBroken Authentication and Session ManagementInsecure Direct Object ReferencesCross-Site Request ForgerySecurity MisconfigurationInsecure Cryptographic StorageFailure to Restrict URL AccessInsufficient Transport Layer ProtectionUnvalidated Redirects and Forwards

Looks innocent enough…

String sql = "SELECT * FROM [Users] WHERE username = '" + Request["username"] + "' AND password = '" + Request["password"] + "'";

bryansul

Elv1sL1ves4ever#

SELECT * FROM [Users] WHERE username = 'bryansul' AND password = 'Elv1sL1ves4ever#'

…but roguery abounds

String sql = "SELECT * FROM [Users] WHERE username = '" + Request["username"] + "' AND password = '" + Request["password"] + "'";

admin

' OR '1' = '1

SELECT * FROM [Users] WHERE username = 'admin' AND password = '' OR '1='1'

Obligatory XKCD Slide

SQL Injection in the News

7-Eleven

Dave & Busters

BJ’s Wholesale Club

OfficeMax

Boston Market

Barnes & Noble

Sports AuthorityForever 21

DSW

Use Stored Procedures

Bad code:

SqlCommand command = new SqlCommand("SELECT * FROM Customers WHERE CustomerId = '" + customerId + "'");

Good code:

SqlCommand command = new SqlCommand("GetCustomer");command.CommandType = CommandType.StoredProcedure;command.Parameters.Add(new SqlParameter("@customerId",customerId);

Use Parameterized Queries

Bad code:

SqlCommand command = new SqlCommand("SELECT * FROM Customers WHERE CustomerId = '" + customerId + "'");

Good code:

SqlCommand command = new SqlCommand("SELECT * FROM Customers WHERE CustomerId = @customerId");

command.Parameters.Add(new SqlParameter("@customerId",customerId);

Use LINQ

But don’t use ExecuteQuery

Bad code:ExecuteQuery<Customer>("SELECT * FROM Customers");

Good code:from c in this.Customers select c;

Avoid EXEC @sql

Moving the string concatenation to the stored proc code still leaves you vulnerable…

EXEC ('SELECT * FROM Customers WHERE CustomerId = ''' + @CustomerId + ''')

The only approved use of EXEC is to call other stored procedures

Remove Database Privileges

Allow only EXECUTE privileges on the necessary stored procedures

All other privileges on all objects must be removed

This is defense in depth

More than just SQL…

XPathXQueryLDAP…just about anything

The World’s Easiest XSS Exploit

XSS is the new buffer overflowBuffer overflows are a path to own the machine…

…but owning a machine is only a means to an end.

Steal private dataLog victims’ keystrokesCreate botnets for DDoS attacksLaunch self-propagating webwormsCreate darknets to trade pirated software or pornography

You can do all of these with XSS, and it’s a lot easier

Input ValidationEnsure the data is what the application expects

FormatLength

Regular expressions can work great hereSystem.Text.RegularExpressions.RegexSystem.Web.UI.WebControls.RegularExpressionValidator

Be careful with your regexes!

Input Sanitization

AntiXSS GetSafeHtml methods

string output = AntiXss.GetSafeHtml(input);

Output Encoding

Harder than it sounds!7 different cases

Use Microsoft AntiXSS/WPL Library

ValidateRequestPage directive

<%@ Page ValidateRequest="true" %>

Web.config setting<configuration><system.web><pages validateRequest="true" />

</system.web></configuration>

More of a defense-in-depth measureDon’t rely solely on ValidateRequest

EnableViewStateMac

Page directive<%@ Page EnableViewStateMac="true" %>

Web.config setting<configuration><system.web><pages enabledViewStateMac="true" />

</system.web></configuration>

CSRF in action

ViewStateUserKeyBuilt-in canary defense for ASPX pages

protected void Page_Init(object sender, EventArgs e){this.ViewStateUserKey = Session.SessionID;

}

Use AntiForgeryToken for ASP.NET MVC

The Same Origin PolicyTwo frames/windows can only communicate with each other if they have the same origin

Origin is defined as having the same:DomainPortProtocol

Also applies to XMLHttpRequest

SOP Example

If my page is http://www.mysite.com/foo/bar.aspx

Page Allowed? Why?

http://blogs.mysite.com/page.aspx No Different domain

https://www.mysite.com/page.aspx No Different protocol

http://www.mysite.com:81/page.aspx No Different port

http://mysite.com/page.aspx No Different domain

http://www.mysite.com/bar/page.aspx Yes Everything ok

Take a guess…

Take a guess…

Take a guess…

Take a guess…

Take a guess…

Document.Domain

Two cooperating pages can lower their domain so they can talk to each other

Do not lower document.domain unless all data and functionality on the site is public

No authenticated accessNo PII

Cross-Domain Access PoliciesUsed by Flash, Silverlight

crossdomain.xmlclientaccesspolicy.xml

<cross-domain-policy><allow-access-from domain="www.good.com"/><allow-access-from domain="*.net"/><allow-access-from domain="*"/>

</cross-domain-policy>

Watcher by Casaba Security

Crypto Algorithm Requirements

AlgorithmType

Banned Allowed Recommended

Symmetric block DES, DESX, RC2, SKIPJACK

3DES (2 or 3 key)

AES (>= 128 bit)

Symmetric stream

SEAL, CYLINK_MEK, RC4 (<128 bit or unreviewed)

RC4 (reviewed and >= 128 bit)

None – block cipher is preferred

Asymmetric RSA (<2048 bit),Diffie-Hellman (<2048 bit)

RSA (>= 2048 bit), Diffie-Hellman (>= 2048 bit)

RSA (>= 2048 bit), Diffie-Hellman (>= 2048 bit), ECC (>= 256 bit)

Hash (includes HMAC usage)

SHA-0 (SHA), SHA-1, MD2, MD4, MD5

SHA-2 SHA-2

HMAC key lengths

<112 bit >= 112 bit >= 128 bit

.NET Crypto LibrariesSystem.Security.Cryptography

AESAESCryptoServiceProvider (XP SP2 & later)AESManaged

RSARSACryptoServiceProvider

ECCECDiffieHelmanCng

SHA-2SHA256CryptoServiceProvider (Windows 2003)SHA384CryptoServiceProvider (Windows 2003)SHA512CryptoServiceProvider (Windows 2003)SHA256Cng (Vista)SHA384Cng (Vista)SHA512Cng (Vista)

Crypto systems get broken

Why assume that current algorithms really are unbreakable, unlike every other time in

the history of cryptography?

eh vxuh wr gulqn brxu rydowlqhbe sure to drink your ovaltine

http://upload.wikimedia.org/wikipedia/commons/b/b0/Gaius_Julius_Caesar.jpg

Consequences

Change codeRebuildRetestDeploy patches to n users

Pretty big window of attack…

Other concerns

Export controlsInternational regulationsFIPS-140

Solution

Plan for this from the beginning

Assume the crypto algorithms you use will be defeated in your application’s lifetime

Code your apps in a cryptographically agile manner

Steps toward crypto agility

Step 1: Avoid hardcoded algorithms

Abstraction

Want one of these?

Are you sure?

.NET top-level abstract classes

SymmetricAlgorithmAsymmetricAlgorithmHashAlgorithm

KeyedHashAlgorithm○ HMAC

RandomNumberGenerator

.NET Crypto ArchitectureHashAlgorithm

+ComputeHash()

SHA512

SHA512Cng SHA1ManagedSHA512Managed

#HashCore()+Create()

SHA1

.NET examples

Non-agile:

MD5Cng hashObj = new MD5Cng();byte[] result = hashObj.ComputeHash(data);

.NET examples

More agile:

HashAlgorithm hashObj = HashAlgorithm.Create("MD5");

byte[] result = hashObj.ComputeHash(data);


Step 1: Avoid hardcoded algorithmsStep 2: Reconfigure the algorithm provider

.NET

Application

mscorlib

machine.config

HashAlgorithm.Create("MD5")

Altering machine.config

<configuration><mscorlib> <cryptographySettings>

<nameEntry name="MD5" class="MyPreferredHash" />

<cryptoClasses><cryptoClassMyPreferredHash="SHA512Cng, …" />

</cryptoClasses>

Remapping algorithm names is dangerous

MD5 SHA-1This is a good thing, right?What could possibly go wrong?


Step 1: Avoid hardcoded algorithmsStep 2: Avoid hardcoded implementationsStep 3: Reconfigure the algorithm providerStep 3 (alternate): Avoid default algorithm names

HashAlgorithm.Create("ApplicationFooPreferredHash");

Web.Config security is hard

Hierarchical structureCan change at any time

Enable Custom Errors<configuration><system.web><customErrors mode=“RemoteOnly”/>

Why give attackers more information to attack you with?

Disable Tracing<configuration><system.web><trace enabled="false"/>

Ensure no Page directives override the application-level tracing

Bad: <%@ Page Trace="true" %>Good: <%@ Page Trace="false" %> or no Trace directive specified

Disable Debugging for ASP.NET

<configuration><system.web>

<compilation debug="false"/>

Enable HTTPOnly cookies<configuration><system.web><httpCookies httpOnlyCookies=”true”>

Disable cookieless session state


<sessionState cookieless=”UseCookies”>

What kind of attacks could sessionless URLs enable?

http://myserver/MyApp/(123ABC)/default.aspx

Disable cookieless authentication


<authentication mode=”Forms”><forms cookieless=”UseCookies”>

Same problem as before

Require SSL for auth cookies<configuration><system.web>

<authentication mode=”Forms”><forms requireSSL=”true”>

Disable “sliding” expiration<configuration><system.web>

<authentication mode=”Forms”><forms slidingExpiration=“false”>

Expert Advice?“…the developer should be able to define a very strong validation pattern, usually based on regular expressions, for validating [user] input.”

OWASP SQL Injection Prevention Cheat Sheet

“Regular expressions are a good way to validate text fields such as names, addresses, phone numbers, and other user information.”

MSDN Patterns & Practices

“Regex is a perfect tool for input validation.”Bryan Sullivan, Ajax Security

71

The Root of the Problem

Example 1: ^\d+$Evaluate this pattern against test input: 123456X

123456 [no match, backtrack]12345 [no match, backtrack]1234 [no match, backtrack]123 [no match, backtrack]12 [no match, backtrack]1 [no match]

Fails in 13 steps (including backtracks)• Operates in O(n) time

72

Exponential Execution

Example 2: ^(\d+)+$Evaluate this pattern against test input: 123456X

123456 [no match, backtrack]12345123456 [no match, backtrack]123 45123456 [no match, backtrack]…

Fails in 223 steps• Operates in O(2n) time

73

ReDoS

More Irony…

“Just as we perform whitelist input validation on the server for security purposes, developers must perform client-side validation to ensure security of their offline applications.”

Ajax Security

75

Detecting Vulnerable Regexes

Look for:Grouping expressions containing repetition that is itself repeatedGroups containing alternation where the alternate subexpressions overlap each other

This is harder than it sounds, and it doesn’t sound easy

76

Regex Testing Strategies

Test each regex clause with a large, valid sample

[email protected]@aaaaaaaaaaaaaaaaaaaaaaaaaaaaa.com

Add one invalid character to the end of the sample

[email protected][email protected]!

Why does this work?

77

XML Entities

Like macros for XML

<!DOCTYPE employees [<!ENTITY companyname "Contoso Inc.">]><employees>

<employee>Bryan S,companyname;</employee><employee>Steve L,&companyname;</employee>

</employees>

79

Nesting Entities

You can nest entities too:

<!DOCTYPE employees [<!ENTITY companyname "Contoso Inc."><!ENTITY divisionname "&companyname; SaaS">]>

80

Exponential Entity Expansion Attack

AKA “The billion laughs attack”

<!DOCTYPE lolz [<!ENTITY lol "lol"><!ENTITY lol2 "&lol;&lol;&lol;&lol;&lol"><!ENTITY lol3 "&lol2;&lol2;&lol2;&lol2;&lol2">…<!ENTITY lol9 "&lol8;&lol8;&lol8;&lol8;&lol8">]><lolz>&lol9;</lolz>

81

Exponential Entity Expansion Attack

82

Infinite Recursion Entity Expansion?

<!DOCTYPE lolz [<!ENTITY lol1 "&lol2;"><!ENTITY lol2 "&lol1;">]><lolz>&lol1;</lolz>

Fortunately (or unfortunately?) not legal

83

Variation: Quadratic blowup Attack

<!DOCTYPE kaboom [<!ENTITY a "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa…">]><kaboom>&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;…</kaboom>

84

External Entity Attacks

You call pull entity data from external sources too:

<!ENTITY stockprice SYSTEM "http://www.contoso.com/stockticker.ashx">

Attack ideas:Infinite delayVery large file downloadsInfinite data pipeIntranet resource redirection

85

XML Entity Attack Defenses

Reduce as much attack surface as possible:

Best solution: Disable inline DTD processing completely

ProhibitDtd propertyIf you can’t do that, then disable external entity resolution

Set resolver to null, or implement a custom resolver If you can’t do that, then throttle external entity resolution

Will need a custom resolver

86

What does “Agile” mean, anyway?

www.goldenrice.org

The Agile Manifesto

Individuals and interactions

Working software

Customer collaboration

Responding to change

Processes and tools

Comprehensive documentation

Contract negotiation

Following a plan

SDL “Classic”

Fits spiral or waterfall……but Agile doesn’t have phases…and it may not even have a release!

Idea: Move SDL to product backlog

Very Agile……but not secure

“Security is not a freakin’ task card.”- Adrian Lane, Securosis

Idea: Do the full SDL every iteration

Very secure……but not Agile!

Idea: Drop some requirements

But every requirement is, well, required

Need to keep all requirementsNeed to reorganize into Agile-friendly form

Three classes of requirements

Every Sprint

Training

Threat modeling

etc...

One-Time Only

Set up tracking

Upgrade compilers

etc...

Bucket

Fuzz parsers

Create response

plan

etc…

Requirements as backlog items

One-time requirements get added to the Product Backlog (with deadlines)So do bucket requirementsEvery-sprint requirements go to the Sprint Backlog directly

Product Backlog• Set up tracking system• Upgrade to VS2010• Fuzz image parser• Fuzz network parser• …

Sprint Backlog• Threat model new stored

procedures• Run static analysis• …

Sprint exit criteria

All every-sprint requirements completeNo bucket items over six months oldNo expired one-time requirementsNo open security bugs over the bugbar

Categorization specifics

SDL v5.0 process guidance documentMSF-A+SDL process template

Both available on www.microsoft.com/sdl

Bug bar• EoP: Remote Anonymous• Info Disc: HBI/PIICritical

• EoP: Local Anonymous• DoS: Asymmetric PersistentImportant

• Info Disc: LBI• DoS: TemporaryModerate

• Info Disc: Random memoryLow

Exception workflow

Level 1

Level 2

Level 3

Level 4

Level 5

Agile Security Challenges

Iterative natureProjects may never endJust-in-time planning/YAGNI mentalityGeneral avoidance of project artifactsEmphasis on project/iteration backlogsGeneral avoidance of automated tools

Security Incident Response

Because 2:00 AM Christmas morning is a poor time to hold a Scrum meeting…



Security bug tracking

Must track bug causeBuffer overflowXSSEtc

And effectSTRIDE

Important for bugbar criteria

Threat modeling“The cornerstone of the SDL”

Data Flow Diagrams (DFDs)STRIDE/elementMitigationsAssumptionsExternal dependencies



Writing secure code

90% Writing SecureFeatures

Overflow defenseInput validationOutput encoding

10% Writing SecurityFeatures

CryptographyFirewallsACLs

Secure code does not featurize

Not a User Story

Doesn’t go in the Product

Backlog

Can’t get prioritized in or

out

Can’t decide to not do security

this sprint

Taskifying the SDL

Some are straightforward...Enable compiler switchesRun static analysis tools

…some are tougher (not actionable)Avoid banned APIsAccess databases safely

Two strategies

Verify these things by hand (alone or in pairs)Verify these things with tools

www.sondheim.com www.dow.com

Static analysis requirements

FxCopCAT.NETPREFast (/analyze)And/or your alternative tool(s) of choice

These are “every-sprint” requirementsBetter still: Continuous Integration

Dynamic analysis requirementsFuzzers (homegrown)

File parsersRPC interfacesActiveX controlsCOM objects

AppVerifierPassive HTTP traffic analysisAnd/or your alternative tool(s) of choice

These are “bucket” requirementsOr CI…

Secure coding librariesAntiXss/Web Protection LibraryStrSafeSafeInt

Use always, check every sprint

<opinion>

This is the future of the SDL</opinion>

Strengths: Adapting SDL to Agile

Bucket activities easily move in & out of sprintsTeams self-select best security activitiesSDL versioning is simpler and more currentEach iteration is a gate



“Welcome changing requirements, even late in development. Agile processes harness change

for the customer’s competitive advantage.”



“At regular intervals, the team reflects on how to become more effective, then tunes and adjusts

its behavior accordingly.”



SDL-Agile “versioning”

SDL-Classic

Updated yearlyGrandfather clause

SDL-Agile

Updated at any timeAutomatic updating



Each iteration is a gate

“Security and privacy are most effective when ‘built-in’ throughout the entire development

lifecycle”

“Security is most effective when it is ‘baked-in’ from the start”

This fits Agile perfectly

The Agile Manifesto

Individuals and interactions

Working software

Customer collaboration

Responding to change

Processes and tools

Comprehensive documentation

Contract negotiation

Following a plan

The SDL-Agile Manifesto

Continuous, incremental effort

Automated tasks

Planned incident response

Heroic pushes

Manual processes

Ad-hoc response

More Resources

SDL 5.0 process guidanceMSF-A+SDL process template

http://www.microsoft.com/sdlhttp://blogs.msdn.com/sdl

My alias: bryansul

Bryan Sullivan Senior Security Program Manager …ipma-wa.com/prof_dev/2010/SDLforManagedCode.pdf · Bryan Sullivan. Senior Security Program Manager. ... Guide product teams to ...

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