Securing .NET – further issues

Question 1

What is Code Access Security (CAS)?

Answer 1

A .NET mechanism to run code with varying trust levels.

Question 2

Why is CAS needed?

Answer 2

Allows protected execution of code from untrusted systems.

Question 3

How does CAS protect systems?

Answer 3

Shields against malicious mobile code.

Question 4

What does CAS allow?

Answer 4

Code from unknown origins to run with protection.

Question 5

How does CAS prevent security issues?

Answer 5

Stops trusted code from unintentionally compromising security.

Question 6

How is trust assigned in CAS?

Answer 6

Based on code origin and identity, not just user.

Question 7

What minimizes fully trusted code in CAS?

Answer 7

Enforces varying trust levels to reduce risk.

Question 8

How does CAS reduce code misuse?

Answer 8

Limits operations exploitable by malicious code.

Question 9

How does CAS reduce liability?

Answer 9

Specifies allowed and forbidden code operations.

Question 10

How does CAS minimize vulnerability damage?

Answer 10

Restricts code impact from security flaws.

Question 11

Who benefits from CAS?

Answer 11

All managed code targeting the CLR.

Question 12

Should .NET apps make CAS requests?

Answer 12

Yes, to ensure proper security enforcement.

Question 13

What is a CAS versioning problem?

Answer 13

Inconsistent behavior across .NET versions.

Question 14

How did CAS policy confuse users?

Answer 14

Managed apps ran differently from native apps.

Question 15

Why is CAS complex?

Answer 15

Involves multiple policy and permission layers.

Question 16

What does CAS policy include?

Answer 16

Policy levels, code groups, caspol.exe.

Question 17

What is CAS enforcement?

Answer 17

Demanding and asserting permissions.

Question 18

What are CAS permissions?

Answer 18

Operations an app is allowed, set by policy or host.

Question 19

What changed in .NET v4 for CAS?

Answer 19

CAS policy deprecated, decisions left to app host.

Question 20

How are desktop apps treated in .NET v4?

Answer 20

Run as full-trust applications.

Question 21

What apps run as full-trust in .NET v4?

Answer 21

Computer apps and network share apps.

Question 22

How do partially trusted apps run in .NET v4?

Answer 22

In a sandbox determining their grant set.

Question 23

What overrides permissions in .NET v4?

Answer 23

Security transparency rules.

Question 24

What is a strong name signature?

Answer 24

A public-key digital signature for assembly identity.

Question 25

What does a strong name verify?

Answer 25

Data integrity from signer to verifier.

Question 26

Why use strong names?

Answer 26

Ensures unambiguous assembly references.

Question 27

How are strong names created?

Answer 27

Signed during the build process, verified on load.

Question 28

How do strong names prevent tampering?

Answer 28

Stop malicious parties from altering assemblies.

Question 29

Do strong names verify publisher trust?

Answer 29

No, only that the key owner signed the assembly.

Question 30

What does Microsoft recommend over strong names?

Answer 30

Authenticode for trusting third-party code.

Question 31

Why are strong name keys vulnerable?

Answer 31

Private keys can be inferred from public keys.

Question 32

What is the default strong name key size?

Answer 32

1024 bits, inadequate for modern security.

Question 33

Why is upgrading strong name keys hard?

Answer 33

Breaks binaries referencing the old identity.

Question 34

What algorithm do strong names use?

Answer 34

SHA-1, found inadequate for secure hashing.

Question 35

Why is SHA-1 problematic?

Answer 35

May lose FIPS-compliant status.

Question 36

What is a FIPS standard?

Answer 36

Federal guidelines for security and communications.

Question 37

What algorithm is recommended over SHA-1?

Answer 37

SHA-256 or stronger.

Question 38

What is an enhanced strong name?

Answer 38

Supports SHA-2 while maintaining compatibility.

Question 39

How do enhanced strong names help?

Answer 39

Allow migration to SHA-2 without breaking references.

Question 40

Can new assemblies use SHA-2?

Answer 40

Yes, if unconcerned with old strong name compatibility.

Question 41

What is a benefit of enhanced strong names?

Answer 41

Claims identity equivalence for compatibility.

Question 42

Why is SHA-1 inadequate?

Answer 42

Vulnerable to attacks, less secure than SHA-2.

Question 43

What happens if CAS permissions are missing?

Answer 43

Code may fail, needing extra error handling.

Question 44

How does CAS reduce mobile code risks?

Answer 44

Limits capabilities of untrusted code.

Question 45

What is a sandbox in .NET v4?

Answer 45

A restricted environment for partially trusted apps.

Question 46

Why was CAS policy deprecated?

Answer 46

Caused confusion and inconsistent app behavior.

Question 47

What is caspol.exe?

Answer 47

Tool to manage CAS policy settings.

Question 48

What is a stack walk in CAS?

Answer 48

Verifies permissions across the call stack.

Question 49

Why specify forbidden operations in CAS?

Answer 49

Reduces unintended security breaches.

Question 50

How does CAS differ from OS security?

Answer 50

Considers code identity, not just user.

Question 51

What is the CLR in .NET?

Answer 51

Common Language Runtime, manages code execution.

Question 52

Why use Authenticode over strong names?

Answer 52

Provides publisher trust and certificate hierarchy.

Question 53

What is a strong name’s limitation?

Answer 53

No certificate hierarchy or publisher verification.

Question 54

How does CAS enhance security?

Answer 54

Reduces trusted code needed to run apps.

Question 55

What is security transparency in .NET v4?

Answer 55

Rules overriding traditional permission systems.

Question 56

Why are larger keys needed?

Answer 56

Protect against attacks inferring private keys.

Question 57

How does .NET v4 handle network apps?

Answer 57

Runs them as full-trust by default.

Question 58

What is the role of a host in .NET v4?

Answer 58

Determines security policy for apps.

Question 59

Why is strong name compatibility important?

Answer 59

Ensures existing binaries reference assemblies correctly.

Question 60

How does CAS minimize vulnerability impact?

Answer 60

Limits damage from code flaws via restricted trust.