Developing Windows and Web Applications using Visual Studio'NET

1
Developing Windows and Web Applications using
Visual Studio.NET
Part 1 Developing Windows Applications using
Visual Studio.NET

• Session 4 Deployment and Security of
  Windows Forms (in C 2005)

Presented by Marten Ataalla
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About Marten

• Senior Software Architect at SSW
• Specialize in
• Application Deployment
• SQL Reporting Services
• Software Auditing
• SharePoint 2003 2007
• Speaker at Sydney .Net Usergroups UTS lectures

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Admin Stuff

• Attendance
• You initial sheet
• Hands On Lab
• You get me to initial sheet
• Homework

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Session 4 Deployment Security

• Agenda
• Part 1 Deployment of .NET Winforms apps
• History
• Deployment Updates
• Security
• Issues Warnings
• Part 2 Security
• Role-based security
• Authentication and Authorization
• Impersonation
• Code Access Security
• Assembly Strong Naming

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Part 1

• ClickOnce

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Windows vs Web forms

• Which side are you on? Why?

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ClickOnceThe Best of both Worlds
Click Once
Windows Forms
Web Forms
Rich UserExperience
NetworkDependency
Tough ToDeploy
Easy To Update
Offline Capable
Tough To Update
Limited UserExperience
Easy To Deploy
High User Productivity
Easy To Manage
Fragile DLL Hell
Responsive Flexible
Complex To Develop
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ClickOnceThe Best of both Worlds

• Which side are you on now?

ClickOnce
Web Apps
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History

• Remember the good old Windows Installer?
• Lets compare it to ClickOnce

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History Feel the pain Windows Installer vs
ClickOnce
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History Feel the pain.Net 1.x HREFing .EXEs

• The.NET Framework must be already installed
• Your application will run on the client as
  partially trusted code only.
• Bad performance as the executable will try to
  load several DLLs with localization resources
• No way to guarantee that all your files are
  indeed downloaded your client may be stuck with
  a "half updated" application.
• Only available offline if you are Working
  Offline
• Your application won't have a shortcut in the
  desktop or the Start menu.

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History Feel the painUpdater Application Block

• You must change your application substantially in
  order to use it
• Needed to write to C\Program Files\
• It runs as a fully trusted local application, so
  it pretty much ignores code access security
• It's not supported by Microsoft.
• Since it uses BITS to download the application
  pieces, it does not run under Windows 98/ME.
• However, Jamie Cool has a work around .NET
  Application Updater Component http//www.windowsf
  orms.net/articles/appupdater.aspx

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Demo

• SSW Diagnostics install

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ClickOnce DeploymentHow it works?

• Users download either
• 1. Setup.exe (500kb) checks pre-requisites
  (Recommended)
• OR
• 2. Application manifestBoo.application(small
  but does not check prerequisites)

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ClickOnce Deployment Deployment Manifests

• Architecture based on two XML manifest
• files
• Application manifest
• Authored by the developer
• Describes the application
• Example which assemblies constitute the
  application
• Deployment manifest
• Authored by the administrator
• Describes the application deployment
• Example which version clients should use

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ClickOnce DeploymentDeployment Manifests
1.0
? 1.1
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Deployed Files
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ClickOnce DeploymentBootstraper
Web Server
Setup.exe
Setup.exe
Dotnetfx.exe
Dotnetfx.exe
Mdac_typ.exe
a
Custom.msi
Custom.msi
Reboot
MDAC detected!
Bar.application
Bar.application
a
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ClickOnce DeploymentWhich download to provide?

• Q\ Which way?
• A\ Depends on pre-requisites
• Q\ What if the only pre-requisite is .NET 2?
• A\ TIP use Request.Browser.ClrVersion
• dim verHave as Version Request.Browser.ClrVersio
  n
• dim verNeed as Version new Version("2.0.50727")
• if ( verHave lt verNeed ) then
• Response.Write("lta href""./Download/Setup.exe""gt
  ")
• else
• Response.Write("lta href""./Download/SSWDiagnosti
  cs.application""gt")
• end if

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ClickOnce Deployment Prerequisites 

• Missing prerequisites must be installed using
  separate redistributable packages.
• The deployment tools in Visual Studio let you
  install the .NET Framework and other
  redistributables as a part of your installation
  (bootstrapping).
• Note Prerequisites can be downloaded
• beforehand into a network location
• to avoid redundant prerequisite
• downloads on networks

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ClickOnce Deployment Prerequisites 

• Before installing an application on a client
  computer, ClickOnce will examine the client to
  ensure that it has certain requirements specified
  in the application manifest.
• These include
• The minimum required version of the CLR
• The minimum required version of the Windows OS
• The minimum version of any and all assemblies
  that must be preinstalled in the GAC

Note 1 If you specify an alternate prerequisite
location, the packages must exist there these
errors are not handled with ClickOnce Note 2
While selecting your prerequisites, keep in mind
that prerequisites might need administrator
privileges to be installed.
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ClickOnce DeploymentStrategies

• Install from the Web or a Network Share
• (Default Strategy) (a Setup.exe)

Install from a CD (a Setup.exe)
Run the Application from the Web or a Network
Share
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ClickOnce Deployment Strategies Compared
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ClickOnce DeploymentSetup Interface
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ClickOnce DeploymentSetup Options Interface
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ClickOnce UpdateHow it works? 
Deployment Framework Service
Application Store
Yes
No
My Application
Installed
Startup SHIM
But, what is a SHIM? Its a small piece of
software that is added to an existing system
program or protocol in order to provide some
enhancement.
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ClickOnce UpdateHow it works? 

• ClickOnce uses the file version information
  specified in an application's deployment manifest
  to decide whether to update the application's
  files.
• After an update begins, ClickOnce uses a
  technique called file patching to avoid redundant
  downloading of application files.
• But, what is a File Patching? Compares the hash
  signatures of the files specified in the
  application manifest for the current application
  against the signatures in the manifest for the
  new version.

Note 1 If you use Visual Studio to compile your
application, it will generate new hash signatures
for all files whenever you rebuild the entire
project. Note 2 File patching does not work for
files that are marked as data and stored in the
data directory C\Documents and
Settings\AdamCogan\Local Settings\Apps\2.0
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ClickOnce UpdateStrategies

• Checking for Updates after Application Startup

• background thread will run to locate and read the
  deployment manifest
• best for low-bandwidth network connections or for
  larger applications
• Specifying Update Intervals

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ClickOnce UpdateStrategies

• Checking for Updates before Application Startup

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ClickOnce UpdateStrategies

• Making Updates Required

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ClickOnce UpdateOptional and Required Updates

• For optional updates, the user can either accept
  or skip the update.

This dialog will not appear when an update is
required. To make an update required in Visual
Studio 2005, you need to set the Minimum Required
Version field in the Updates dialog box to match
the version of the application youre currently
publishing We recommend just 4 prior versions
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ClickOnce UpdateBlocking

• Want more control over the update?
• You may block update checking altogether and
  provide UI for updates using Deployment API in
  your application

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What if it is bad
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AdvancedRolling back updates

• The latest 2 versions of the application are
  stored, the rest are removed.
• Clients may restore 1 application update.

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Demo

• Configure in VS.NET
• Install the application
• Update to a new version
• Rollback to a previous version
• Update again with a good version

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AdvancedScalability

• Server Processing is fineNormal activation of a
  ClickOnce application is very inexpensive for
  the server network
• Bandwidth is an issueConsider network bandwidth
  needed for initial application deployment
  application updates
• However, the standard methods techniques used
  to scale web or file servers can be used for
  ClickOnce applications (e.g server farms, etc)

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AdvancedCache

• Location for ClickOnce applications
• On XP userprofile\Local Settings\Apps
• On VISTA userprofile\AppData\Local\Apps
• Cache quota is 250MB.
• Data files do not count toward this limit
• Modify by changing Registry key
• HKEY_CURRENT_USER\Software\Classes\Software\Micros
  oft\Windows\CurrentVersion\Deployment\OnlineAppQuo
  taInKB

Note The value in the OnlineAppQuoteInKB
registry key is a DWORD that expresses the cache
size in kilobytes
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BUGSProxy Servers on Client Machines

• Issue
• Clients accessing the internet through proxy
  servers will get the error when launching the
  application
• The remote server returned an error (407) Proxy
  Authentication Required
• Default credentials to the proxy are not passed
  through, ClickOnce attempts to download the files
  without going through the proxy.
• Workaround
• A hot fix is available from Microsoft to replace
  the System.Deployment.dll or wait until the next
  service pack comes out for .Net 2. You must
  contact Microsoft for it.
• http//support.microsoft.com/kb/917952

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BUGS Publish Version sync issues

• Issue
• The problem is that (rarely) the publish revision
  number that Visual Studio has in memory sometime
  gets out of sync with the publish revision number
  that is stored is the user project file
  (.xxproj.user).
• Users would get the following
• Error 68 Publish failed with the following error
  Could not find a part of the path
• Workaround
• The easiest work around, which is to manually up
  the publish revision number and choose File -gt
  Save All.

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Warnings ClickOnce and non-IE Browsers

• Issue
• ClickOnce doesnt work on non-IE browsers (by
  default).
• ClickOnce provides IE with a mime handler
  interface for the mime type application/x-ms-appli
  cation which is associated with .application
  files on servers hosting ClickOnce application.
• So what happens in firefox?
• .application file is downloaded.
• If manifest contains relative paths, it will
  fall over.
• If it contains full paths, it will fail due to
  security checks (in place by ClickOnce team).
• Workaround
• Firefox There is an official Add-on
  https//addons.mozilla.org/firefox/1608/
• Non-Firefox ClickOnce helper is an attempted a
  solution, however it is not tested
  http//www.softwarepunk.com/cohelper/
• Note The ClickOnce team will fix this in the
  next release of the framework.

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Warnings File Patching and Rebuilds

• Issue
• The File Patching model for assemblies (even
  strong assemblies) is based entirely on file
  hash.
• Projects when rebuilt in VS often cause the same
  assemblies (exactly same source) to have
  different hashes. Hence if you are rebuilding
  your entire v2.0 solution its possible that
  assemblies that have not changed in terms of
  functionality will still have a different hash
  and hence be downloaded again by ClickOnce
  instead of being copied locally.
• Workaround
• Dont hit rebuild unless you need to! (when
  references mightve changed)

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WarningsManifest Overwriting

• Issue
• The manifest file for the ltAppNamegt.exe.manifest
  is overwritten, causes strange compile errors
  when included in the solution.
• Workaround
• You dont need the manifest file in .Net 2 for XP
  Styles. If you need it for any other reason, then
  merge your manifest into the one built with
  clickonce.
• Note If you are running SSW Code Auditor, this
  would not have been a problem ?

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Warnings File Compression

• Issue
• There are no file compression mechanisms in
  ClickOnce. By default, your file will be
  downloaded uncompressed across the
  network/internet.
• Workaround
• ClickOnce supports HTTP 1.1 compression. Simply
  enable this on your web server the files
  downloaded will be compressed.

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Suggestions Missing Features

• Rollback Feedback
• We want our clients to give us feedback as to why
  they are rolling back a version
• Rollback Count
• Clients should be able to rollback back to a
  certain number of versions (set by the developer)
• Version Download/Update/Rollback Stats
• What versions our clients are downloading,
  updating to and rolling back from. Presented in
  Reporting Services reports.
• Microsoft should release MSN messenger as a
  ClickOnce app.
• Staged Rollout
• Specify beta testers, and grouped downloads via
  authentication
• eg. MSN Messenger could let MVPs and RDs get the
  latest beta
• We want 10 released each day, to manage
  bandwidth and transition.
• Scalability
• limit to x concurrent - the rest would not be
  told of the new version until later.

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Moving your Application to ClickOnce

• You must consider
• What about your previous Windows Installer
  installation on the client machines?
• Suggestion Create a prerequisite that checks
  for and uninstalls the previous versions. (or
  uninstall it in the start of your app)
• Where is your data stored? ClickOnce uses
  different App folders for each new version, for
  each user.
• Suggestion Use ApplicationData folder if the
  settings are per user, otherwise
  CommonApplicationData per application for all
  users.
• You must consider the Limitations

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Limitations Overview

• Installation of shared files, drivers, assemblies
  in GAC, for multiple users, office addins, etc
• Installation UI cannot be changed
• Add application to Startup group, Favorites menu
• Bootstrappers still need admin privileges if
  there are prerequisite redistributables
• Register file types
• No Updating via FTP

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Part2

• Security

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Security

• Why do we need security in our applications?
• Protect our investment keep malicious users out
• Protect sensitive data
• Medical records, customer details, salary info

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Security in .NET

• 2 parts to .NET Security
• Role-based security
• protects the application from the bad users
• Code Access Security (CAS)
• protects the users system from bad application

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Role-based Security

• How do we know who is using our application?
  (Authentication)
• e.g. Who are you?
• And how do we control what they can and cannot
  do? (Authorisation)
• e.g. employee info dont want employees to see
  each others salaries

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Authentication Authorisation

• In .NET, Users Identities

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Authentication Authorisation

• In .NET, Groups Roles

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Authentication Authorisation

• Where can we store a list of valid users?
• Active Directory
• Database
• Web Service
• XML
• Excel
• etc.

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• Demo

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Authentication Authorisation

• We saw
• Windows (Integrated) Authentication
• Check against the user I am logged in as
• Authorisation
• Enable/disable button
• This can obviously be extended
• Locking methods e.g. ViewCreditCardInfo
• Custom messages

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Authentication Authorisation
Generic (Text-based)
Read from Database (Custom)

IIdentity (Authentication) IPrincipal
(Authorisation)

Active Directory (Windows Security)
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Impersonation

• What is Impersonation?
• Tim goes to pick up a parcel for Adam
• Tim goes to the PO but access is denied (only
  Adam is allowed to have the parcel)
• Tim returns with Adams ID
• Staff says OK Tim gets the parcel

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Impersonation

• Running the code under another persons
  permission. i.e. Doing something on someone
  elses behalf
• Webforms example
• Accessing network share as domain user instead of
  the default local ASPNET account
• Winforms example
• Manager in Supermarket has to login to offer the
  customer the discount.

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Impersonation

• How does it work?
• User logs in to website as DOMAIN\TomJones
• IIS checks the login against Active Directory
• If the login matches the one in Active Directory,
  the user is now impersonating a Windows user
• Application can now login to database, perform
  any functions that the Windows user can

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Impersonation

• Impersonation (example)

Login via web as DOMAIN\TomJones
IIS checks login against Active Directory
.NET code is now impersonating Windows
User DOMAIN\TomJones
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What about lots of users?

• e.g. you have a public web site (blog, forums,
  ebay etc.)
• How would the user connect to the database?
• Embed a login and password in your connection
  string
• VERY BAD this is stored in plain text
• AD / Impersonation
• BAD big list of users
• BAD cant extend data
• Give the web ASPNET account access to the
  database
• GOOD for unknown numbers of users (i.e. public
  websites)
• GOOD no stored credentials (using integrated
  security)

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Special case - Mixed

• e.g. you want your company users to log in on a
  public site
• So that they can get to company-only information
• Mixed mode
• Check against AD
• Check against Database
• Nice and flexible

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Code Access Security

• Imagine a world without SPAM and SpyWare

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Code Access Security

• What is Code Access Security (CAS)?
• Protect your system against evil code
• Rules enforced by the .NET Framework

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Code Access Security

• Who should control CAS policies?
• System administrators
• Not developers!

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Assembly Strong Naming

• How do you know your software came from its
  publisher?
• e.g. SSW Registration
• Someone could simply replace the DLLs in the
  folder and your application would use that

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Assembly Strong Naming

• Enter Strongly Named Assemblies
• Use a special private key to uniquely sign an
  assembly (e.g. SSW Registration)
• The caller (e.g. SSW Code Auditor) uses a public
  key to unlock the code
• This guarantees the authenticity of any external
  components your application is using
• Really easy to use

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ClickOnce Security
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ClickOnce SecurityPartial Trust Permission
Settings

• Custom Permission settings can be set for the
  following

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ClickOnce SecuritySecurity Features

• Zero-impact installation
• Files cached under user profile
• Cannot touch shared resources on machine
• Code Access Security sandbox execution
• Based on origin of files (deployment server)
• Can elevate permissions through user prompting
• Can elevate permissions automatically through
  trust license
• XML Signature
• Signed manifests to ensure authentication and
  integrity
• Note VS.NET 2005 enforces permissions during
  debugging ?

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Useful links

• Security in .NET
• www.4guysfromrolla.com/webtech/121901-1.shtml

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References

• http//blogs.msdn.com/saurabh/archive/2006/03/02/5
  41988.aspx
• http//blogs.msdn.com/clickonce/
• http//blogs.msdn.com/saurabh/archive/2006/01/25/5
  17613.aspx
• http//blogs.msdn.com/winformsue/archive/category/
  11821.aspx
• http//www.softwarepunk.com/cohelper/
• http//msdn2.microsoft.com/en-us/library/142dbbz4.
  aspx
• http//www.windowsforms.net/FAQs/default.aspx?Page
  ID3CategoryID24SubcategoryID27tabindex2
• http//forums.microsoft.com/MSDN/ShowPost.aspx?Pos
  tID615033SiteID1
• http//www.code-magazine.com/article.aspx?quickid
  0601041page3
• http//msdn.microsoft.com/library/default.asp?url
  /library/en-us/dnreal/html/realworld12012004.asp
• http//www.windowsforms.net/articles/appupdater.as
  px
• http//forums.microsoft.com/MSDN/ShowPost.aspx?Pos
  tID173747SiteID1
• http//support.microsoft.com/kb/917952

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Finally a whinge

• http//www.ssw.com.au/SSW/Standards/BetterSoftware
  Suggestions/