[aerogear-dev] iOS Basic/Digest Thoughts

Corinne Krych corinnekrych at gmail.com
Wed May 29 04:57:35 EDT 2013


Hi Christos,

Looking at the integration test code for the second approach (the one not
using the Auth Module), you just set the credentials and you don't have to
explicitly call login/logout?

Sure it looks like magic.
You don't have the nested callback structure. But where do you put the
failure block code then, in case of wrong credentials?

++
Corinne


On 29 May 2013 10:20, Christos Vasilakis <cvasilak at gmail.com> wrote:

> Hi,
>
> iOS platform provides built-in implementations for authenticating against
> HTTP endpoints that support Basic / Digest authentication (among others).
> The workflow when iOS tries to authenticate against those endpoints is
> basically:
>
> a) A credential storage singleton object<https://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/NSURLCredentialStorage_Class/Reference/Reference.html> provided
> by the system is consulted for authentication credentials. If credentials
> are found, the system proceeds with authentication. Understandably for this
> to work, the developer has to initially push the credentials to the system
> object (and remove when done).
>
> b) If credentials are NOT found, the system tries to call the delegate
> method e.g. 'connection:didReceiveAuthenticationChallenge<http://developer.apple.com/library/mac/documentation/Foundation/Reference/NSURLConnectionDelegate_Protocol/Reference/Reference.html#//apple_ref/occ/intfm/NSURLConnectionDelegate/connection:didReceiveAuthenticationChallenge:>',
> giving a chance for the user to provide the credentials, by calling the
> appropriate methods on the authentication challenge object passed in.
>
> AeroGear library,  currently has a notion of pluggable authentication
> modules providing an interface for clients to implement  'login', and
> 'logout' methods, depending on the authentication scenarios that they try
> to support. This fits nicely with singleton credential storage approach, in
> the sense when doing 'login' and 'logout', we simply edit the credential
> storage adding or removing credentials appropriately. A branch for this
> work can be found here<https://github.com/cvasilak/aerogear-ios/tree/basic.digest.auth>.
> For usage, have a look at our integration test<https://github.com/cvasilak/aerogear-ios-integration/blob/basic.digest.auth/AeroGear-iOS-Integration/AeroGear-iOS-IntegrationTests/AGHttpBasicAuthenticationTests.m>
>
> For testing purposes, another branch<https://github.com/cvasilak/aerogear-ios/tree/basic.digest.nsurlcredential> was
> created, this time letting the user to directly pass<https://github.com/cvasilak/aerogear-ios-integration/blob/basic.digest.nsurlcredential/AeroGear-iOS-Integration/AeroGear-iOS-IntegrationTests/AGHttpBasicAuthenticationTests.m#L50>
>  an NSURLCredential<http://developer.apple.com/library/ios/#Documentation/Cocoa/Reference/Foundation/Classes/NSURLCredential_Class/Reference/Reference.html> object
> initialised with the username/password combination during the Pipe
> configuration. Those credentials are internally stored and given back to
> the system by implementing the necessary callback <https://github.com/cvasilak/aerogear-ios/blob/basic.digest.nsurlcredential/AeroGear-iOS/AeroGear-iOS/core/AGHttpClient.m#L240>.
> A usage example can be found in our  integration test<https://github.com/cvasilak/aerogear-ios-integration/blob/basic.digest.nsurlcredential/AeroGear-iOS-Integration/AeroGear-iOS-IntegrationTests/AGHttpBasicAuthenticationTests.m>
>
> advantages of using the singleton approach:
> - fits nicely with the authentication mechanism we have in place (as an
> extension HTTPBasicDigestAuthenticationModule<https://github.com/cvasilak/aerogear-ios/blob/basic.digest.auth/AeroGear-iOS/AeroGear-iOS/security/AGHttpBasicDigestAuthentication.m>)
> so user familiarity when looking to add basic/digest support to the Pipe.
> - we control the credential type e.g.
> 'NSURLCredentialPersistenceForSession'. This eliminates errors of using
> 'NSURLCredentialPersistencePermanent' and having the user to explicitly
> clear the keychain when trying to login with a different combination. For
> my search, many errors occurs because of this.
>
> disadvantages of using the singleton approach:
> - not sure if many iOS dev will like the fact of creating an Authenticator
> object instead of using directly an NSURLCredential object that are used to.
>
> ---
> advantages of using the 'nsurlcredential' directly:
> - users familiarity with the object.
> - not explicit login logout request.
>
> disadvantages of using the 'nsurlcredential' directly:
> - error credential type can lead to errors.
>
> With discussions with Matthias, we are more keen in following the
> HTTPBasicDigestAuthenticationModule<https://github.com/cvasilak/aerogear-ios/blob/basic.digest.auth/AeroGear-iOS/AeroGear-iOS/security/AGHttpBasicDigestAuthentication.m> approach
> instead of providing the NSURLCredential<http://developer.apple.com/library/ios/#Documentation/Cocoa/Reference/Foundation/Classes/NSURLCredential_Class/Reference/Reference.html> configuration
> option on the Pipe. Surely enough, in the documentation we will explicitly
> state that "login"/ "logout" methods,  serve as a mean to setup internally
> the iOS authentication system so users don't have too (instead of calling
> remote endpoints)
>
> Wdyt?
>
> Thanks,
> Christos
>
>
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