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Microsoft .NET Initiative
CSE 333
Fall 2002
Keith Bessette
Hardik Davé
Jaladhi Mehta
Introduction and Overview
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What is .NET ?
History and Evolution of .NET
What is .NET made up of ?
Scope of the paper
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.NET languages and Java
Database Connectivity using .NET.
Security Issues Concerning .NET and Java
Interoperability: Middleware and Languages
.NET Languages
• Supported Languages in .NET
• C# Background
C# vs. Java – Differences and Similarities
• Class Hierarchies
– Both have single rooted class hierarchies System.Object and
Java.lang.object
– Both classes have methods sharing some similarities and difference
• Execution Environment
– JAVA compiled to bytecodes which are interpreted or natively
compiled and run in managed exec envt JVM
– C# code gets compiled to IL which runs in CLR C# code is never
interpreted, it is always natively compiled C#’s IL is more type
neutral
C# vs. Java – Differences and Similarities
(Continued)
• Object Creation
– In JAVA objects are Heap based
– In C# objects are Heap based as well as Stack based
(called value types)
• NameSpaces
– In JAVA packages reflect the physical directory layout
– C# has complete separation of physical packaging and
logical naming
C# vs. Java – Differences and Similarities
(Continued)
• Access Modifiers
C# access modifier
Private
Public
Internal
protected
internal protected
Java access modifier
Private
public
protected
N/A
N/A
• Serialization and Documentation
• C# supports XML format as well as binary format
for serialization while Java only supports binary
format by default.
• JAVA uses Javadoc while C# uses XML for
documentation
C# vs. Java – Differences and Similarities
(Continued)
• Deterministic object cleanup
– C# supports dispose() method
– C++ like destructors without memory allocation woes Best of both
worlds
• Pointers and unsafe code
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C# can have pointers when it is running in unsafe mode
Program must have full trust granted earlier
Unsafe keyword, /unsafe compiler switch
Fixed keyword to avoid the garbage collector moving the variable
during the mark and collect algorithm phase
C# and interoperability
• Platform interoperability
– How C# and JAVA run on various platforms
– JAVA is a single language platform
– C# supports multiple languages as long as they conform
to CLS
– JAVA has better portability for various o/s and
platforms
– C# currently runs on only windows platforms
– .NET platform files complied to PE files
C# and interoperability
• Standards Interoperability
– How both languages access standards like
database systems, graphics library, etc.?
– C# and JAVA both don’t scale too well due to
Microsoft and Sun’s business motivations
– C# has been submitted to ECMA to derive to a
standard
– .NET is sort of an open platform
C# and interoperability
• Language interoperability
– Level and ease of integration with other
languages
– JAVA supports language interoperability
through JNI, CORBA
– .NET has language independence
– .NET supports any languages as long as they
conform to CLS and CTS
Database Connectivity
• Database connectivity in .NET
– Different APIs for connecting to the Database.
– JDBC was introduced by Sun Microsystems in
1996
– History of ADO and JDBC.
ADO.NET Architecture
• Three Level Architecture
• XML and DataSet as objects of interaction
Presentation Tier
Windows Forms
MyApp.Ex
e
DataSet
Internet
Intranet
Web Forms
I
E
DataSet
Business to Business
(BizTalk, for example)
XM
L
Business
Tier
Data Object (Class)
DataSet
Data
Adapter
Data
Adapter
Data
Tier
ADO.NET Architecture
• Three Layers of
Architecture
• RecordSets,
Statements – Connection
and DriverManager
Offline DB Access
• Primitive offline DB access using ResultSets in
JDBC
• Complete offline access in .NET using DataSets
• ADO.NET’s DataSet Architecture
DataSet
DataTableCollections
• DataSet functionality
DataTable
• XML as a method of choice.
DataRowcollection
DataColumncollection
ConstraintCollection
DataRelationCollection
Fig 4.3
ADO.NET DataSet
Interoperability with XML
• ADO.NET’s powerful support for XML
• XML functions in DataSets and ADO.NET
• Oracle’s support for XML
SQL
DB
XML
.NET
developed
Application
XML
Oracle
DB
Security Issues concerning .NET and Java
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Secure development and execution environments
CBAC: permission for code to access resources
RBAC: permission for users/roles to access resources
Code verification and execution: semantics, bytecode, safe
execution environment
• Secure communication: pass data/messages securely
• Code and data integrity: no unauthorized code
modification, cryptography
Code Based Access Control
• CBAC is the security that allows and prevents a
piece of code to access resources
• Evidence Based Security, Permissions, Security
Policy
• CLR reviews evidence of an assembly
• Determines identity from evidence
• Looks up and grants permissions based on the
security policy for that assembly identity
Evidence Based Security
• The CLR examines assemblies to determine
their origin
• CLR looks at metadata for:
– where the code originate
– creator of the assembly
– URL and zone the assembly came from
• CLR verifies the association of metadata w/
an assembly
Permissions
• Permission: assigned to a piece of code, the
allowance to execute a certain method or access a
certain resource
• Assemblies request permissions to execute, and
the CLR answers at runtime
• Permissions are grouped into sets w/ the same
level of security and trust
• Assembly from Internet zone maybe granted
Internet permission set for untrusted code
Security Policy
• SP is set by an admin to make permission
decisions for assemblies and domains
• Three policies: Total Enterprise, Machine
executing code, Requesting User
• Any policy file may partially restrict permissions
of another policy file
• SP groups code into hierarchal categories based on
identity determined by the CLR
• SP determines permissions for assembly after code
is grouped and categorized
Java CBAC vs. .NET CBAC
• Permissions are grouped into protection domains and associated
w/ groups of classes
• Permissions are grouped into sets and assoc w/ code groups
• Classes are grouped by their origin like Code is categorized by
assembly’s zone
• No Security Manager by default in Java
• J2EE has 2 SP types: executing machine & requesting user
• .NET provides a lot of standard permissions
• Stronger credentials needed for permissions in .NET (evidence)
• SP files are more configurable in Java, but doesn’t help w/o all
perm sets
Role Based Access Control
• .NET applies ‘Principal’ term to role membership
• .NET uses many plug-in authentication modules
• Windows: windows apps using Security Support Provided
Interface
• Passport: Microsoft implemented centralized
authentication service
• Form based: HTML logon form from ASP.NET; identity
cookies
• IIS Server: built in mechanisms like Basic, Digest, X.509
certs w/SSL
• Impersonation: allows a user to use another identity to
access another application
Java RBAC vs. .NET RBAC
• .NET supports both imperative and declarative role
permission checking
• Java servlets provide declarative checking at the servlet
level
• EJB’s provide declarative checking down to method level
• JAAS provides imperative checking within method level
• .NET flexibility is limited severely
• IIS is only supported server of .NET framework
• Passport requires users to be members of Microsoft
Passport service
Code Verification and Execution
• Prevent system weaknesses exposure by application errors;
malicious or not
• .NET and Java perform security checks during code
execution
• Stack integrity, bytecode structure, buffer overflows,
semantics
• Application Domains have static boundaries
• Protection Domains have dynamic boundaries
• All security checks to verify code are done on managed
code
• Both .NET and Java allow unmanaged code to bypass the
CLR and JRE
Secure Communication
• Secure Communications are done at the
application level
• Both platforms support SSL and TLS
• .NET apps can use Windows SSPI and IIS
• Java provides Java Secure Sockets
Extensions (JSSE)
• JSSE is very flexible, can be configured
easily for RMI
Secure Code and Data Protection
• .NET uses Windows Crypto API
• Java Crypto Extensions (JCE) and Java Crypto
Architecture (JCA)
• Signed distribution files are necessary for source
verification
• .NET uses strong named assemblies signed with an RSA
keypair
• Java’s JAR files are sealed and each class is signed
• Java’s manifest files don’t require version info
• Once again .NET is tied to Windows so Java is more
flexible
• Crypto algorithms are based on published standards
Middleware Interoperability: COM
• .NET can access COM client as COM can access a
.NET client
• Runtime Callable Wrapper (RCW) wraps the
COM object
• COM Callable Wrapper (CCW) wraps the .NET
object
• System.Runtime.InteropServices.ComVisible
limits what COM client can call
Middleware Interoperability: .NET Remoting vs. RMI
• .NET creates ‘Channels’ to remotely access
objects; HTTP, TCP
• .NET does allow ability to create custom
channels; IIOP
• RMI creates sockets to remotely access
objects; IIOP, JRMP
• .NET doesn’t have a naming registry for
services
Middleware Interoperability: Corba
• Corba is one of the most used middlewares
today
• Microsoft doesn’t support IIOP, Java does
• Create custom channel using TCP/IIOP
• Use wrappers, connect to a Corba object via
a COM object