Securing .NET

Question 1

Why was .NET expected to be secure?

Answer 1

Thought to eliminate all security issues, but it didn’t.

Question 2

What is a key lesson for .NET managed code?

Answer 2

Don’t store secrets in code or web.config files.

Question 3

How should encryption be handled in .NET?

Answer 3

Use System.Security.Cryptography namespace classes.

Question 4

Why validate input in .NET?

Answer 4

Ensures correctness before trusting user input.

Question 5

What vulnerabilities does managed code mitigate?

Answer 5

Buffer overruns and issues with fully trusted mobile code.

Question 6

What is an example of risky mobile code?

Answer 6

ActiveX controls, mitigated by managed code.

Question 7

How does traditional Windows security work?

Answer 7

Checks only the principal’s identity for trust.

Question 8

What enhances Windows security?

Answer 8

Restricted tokens and least privilege, available since Windows 2000.

Question 9

How does .NET differ from traditional security?

Answer 9

Assigns trust levels to code based on system policy and evidence.

Question 10

What is evidence in .NET security?

Answer 10

Properties like digital signatures or code’s site of origin.

Question 11

How does evidence affect .NET code?

Answer 11

Security policies use it to grant permissions.

Question 12

Why is .NET security important today?

Answer 12

Users run code from unknown authors on the internet.

Question 13

How does .NET handle untrusted code?

Answer 13

Restricts code capabilities, not user privileges.

Question 14

What is an example of restricted code?

Answer 14

Web page scripts with limited capabilities.

Question 15

What does .NET generalize?

Answer 15

Code trust, balancing security and functionality.

Question 16

Why avoid lazy programming in .NET?

Answer 16

Trust model doesn’t guarantee secure code.

Question 17

What is FxCop?

Answer 17

A Microsoft tool to check .NET assemblies for design guideline conformance.

Question 18

What does FxCop flag?

Answer 18

Lack of strong names or unspecified permission requests.

Question 19

What output does FxCop produce?

Answer 19

XML reports on assembly compliance.

Question 20

Since when is FxCop integrated with Visual Studio?

Answer 20

Visual Studio 2010 and later.

Question 21

Does FxCop guarantee secure code?

Answer 21

No, but it’s a good starting point.

Question 22

How does .NET prevent spoofing?

Answer 22

Uses strong names for assembly identity.

Question 23

What is a strong name in .NET?

Answer 23

Text name, version, culture, public key, and digital signature.

Question 24

How is a strong name created?

Answer 24

Using sn.exe with syntax SN -k keypair.snk.

Question 25

What does a strong name key pair contain?

Answer 25

Private and public keys for signing/verifying assemblies.

Question 26

Why protect strong name key files?

Answer 26

Prevent unauthorized use of signing keys.

Question 27

Where are strong-named assemblies stored?

Answer 27

In the global assembly cache (GAC).

Question 28

How are assemblies added to the GAC?

Answer 28

Using Mscorcfg.msc or gacutil.exe.

Question 29

What is gacutil.exe?

Answer 29

A tool to manage the global assembly cache.

Question 30

Why use the 64-bit gacutil.exe?

Answer 30

Required for 64-bit operating systems.

Question 31

What are assembly permission requests?

Answer 31

Declarations of permissions needed by .NET code.

Question 32

Why request permissions in .NET?

Answer 32

Informs CLR of code’s required capabilities.

Question 33

Are permission requests mandatory?

Answer 33

No, they are optional.

Question 34

What happens during a permission Demand?

Answer 34

CLR verifies all calling code has required permissions.

Question 35

What is a stack walk in .NET?

Answer 35

CLR checks the call stack for permission compliance.

Question 36

Why request permissions explicitly?

Answer 36

Increases likelihood of proper code execution.

Question 37

What happens if permissions are not granted?

Answer 37

Code needs extra error-handling for failures.

Question 38

What is RequireMinimum in .NET?

Answer 38

Defines the minimum permission set an app needs.

Question 39

What occurs if minimum permissions aren’t met?

Answer 39

CLR raises a PolicyException, and the app won’t run.

Question 40

What is UnmanagedCode permission?

Answer 40

Allows calling unmanaged code, a highly privileged action.

Question 41

What determines UnmanagedCode permission?

Answer 41

Flags on the SecurityPermission class.

Question 42

What risks does unmanaged code pose?

Answer 42

Can perform any action based on user account privileges.

Question 43

Why restrict code trust in .NET?

Answer 43

Protects highly trusted users from risky code.

Question 44

How does .NET balance security and functionality?

Answer 44

Grants permissions based on code evidence, not user.

Question 45

What is a digital signature in strong naming?

Answer 45

Verifies assembly integrity and authorship.

Question 46

Why store business logic assemblies in GAC?

Answer 46

Ensures trusted, strong-named code execution.

Question 47

What is the CLR?

Answer 47

Common Language Runtime, manages .NET code execution.

Question 48

Why validate input correctness?

Answer 48

Prevents exploitation of untrusted data.

Question 49

What is a benefit of managed code?

Answer 49

Reduces buffer overrun vulnerabilities.

Question 50

Why avoid custom encryption?

Answer 50

System.Security.Cryptography is more secure and tested.

Question 51

What is a web.config file?

Answer 51

Configuration file for .NET web applications.

Question 52

Why not store secrets in code?

Answer 52

Easily accessible to attackers if code is compromised.

Question 53

What is a PolicyException?

Answer 53

Raised when minimum permissions aren’t granted.

Question 54

How does .NET handle web scripts?

Answer 54

Restricts their capabilities for safe execution.

Question 55

What is Mscorcfg.msc?

Answer 55

.NET Configuration tool for managing assemblies.

Question 56

Why use strong names for excel.exe?

Answer 56

Prevents spoofing by verifying file identity.

Question 57

What is the role of system policy in .NET?

Answer 57

Grants permissions based on code evidence.

Question 58

Why is evidence-based trust flexible?

Answer 58

Allows nuanced security decisions for unknown code.

Question 59

How does .NET improve on ActiveX security?

Answer 59

Limits code trust, unlike ActiveX’s user-based trust.