Saas webinar-dec6-01

So you're building a native app?

(Or at least you should be)

Paul Madsen
Sr. Technical Architect

© 2010 Ping Identity Corporation

Agenda
•Drivers
•Very brief discussion of web vs native
•Authentication for native apps
•OAuth 2.0
•What does a client need to do to do
OAuth?


Mobile Application Models
Web Applications Native Applications

Web Server Web Server

Mobile Web
Page

HTML JSON/XML

Mobile Device Mobile Device

Web App Native App

Browser


Native

Web


Pros/cons


Native Applications Authentication

Service Provider 1. User trades credentials
for a token
2. Token delivered through
the browser to native
application
3. Native application
Token Token presents token on API
1 4 calls

Password 4. API endpoint returns
2
3 JSON/XML application data as
Device JSON/XML

Native
Browser
App


OAuth 2.0
– An open protocol to allow secure API authorization in a simple
and standard method from desktop, mobile and web applications.
– Defines authorization & authentication framework for RESTful
APIs
– Applied to delegated authorization – mitigates password anti-
pattern - archetypical use case
– Provides a standard way to give a ‘key’ to a third-party which
allows only limited access to perform specific functions without
divulging your credentials


Native Mobile OAuth Options
• DIY
• Launching the browser (externally or embedded)
• Detecting callback from the browser
• JSON response parsing
• Secure storage of persistent tokens

• Use OAuth Client Library – Provides the above functionality with
a higher level of abstraction. E.g.:
• Google Toolbox for Mac - OAuth Controllers
• http://code.google.com/p/gtm-
oauth/wiki/GTMOAuthIntroduction
• Google APIs Client Library for Java
• http://code.google.com/p/google-api-java-
client/downloads/detail?name=google-api-java-client-
1.4.1-beta.zip

• (In Android) Android AccountManager
11

AccountManager

•As of Android 2.0,
AccountManager
manages accounts on
device
•Handles the OAuth 2.0
authorization flow on
behalf of applications
•Collects user consent
(as opposed to via a
browsert window)


Android OAuth options
OAuth authz
Device App Browser
AS
API call w token
RS
DIY & external browser

Device Library OAuth authz
App
Browser
AS
API call w token
RS

Use OAuth library & embedded browser

OAuth authz
Device App Account AS
Manager
API call w token
RS
AccountManager

Detailed walk through
• For completeness, we'll show the DIY model
• We'll show what the native application needs to
do to
1. Get user authenticated and get their authorization
2. Obtain an access token
3. Use that access token on an API call
4. Get a fresh access token when the original expires


Getting a token overview

1. Open a browser and pass scopes
2. Deal with callback when it comes
3. Trade code for token


Native Mobile Client Integration
Getting a Token

• Identify when a user needs to grant access to something at the Resource
Server

• When this situation occurs, open a browser to:
https://as.example.com/as/authorization.oauth2?c
lient_id=<mobappclient_id>&response_type=code

Pre-requisites: Note: Additional query parameters are possible:
• The partner OAuth Client must be • scope – space delimited (URL encoded as %20) requested
defined in PingFederate config. permissions of the client
• Client must be assigned (at min.) the • state – an opaque value used by the partner to maintain state on
Authorization Code grant type - callback
and thus a defined callback URL. • idp – custom parameter to request SAML IdP based authentication
• IdP Adapter Mappings to • pfidpadapterid – custom parameter to authenticate the user with a
authenticate via an adapter named IdP Adapter

18

Getting a Token (cont’d)

• Open browser to authorization endpoint sample code:

- (IBAction)doAction:(id)sender
{
NSLog(@"About to open Safari to Oauth AS Authorization Endpoint...");

// In this example, use a named IDP connection for user authentication
NSString* launchUrl =
@"https://as.pingidentity.com/as/authorization.oauth2?client_id=mobileclient1&respons
e_type=code&idp=https://idp.acme.com/saml-entity-id";

[[UIApplicationsharedApplication] openURL:[NSURL URLWithString: launchUrl]];
}

19

Comparison of grant types &
models

Authorization Code ( Resource Owner
Embedded browser) Credentials
• No need to leave app context

• Password shared with 3rd party
• Application owns login UI
• Enables SSO
• Enables strong authn
• AS owns login UI

• Visual trust cues (SSL lock)
• Authentication can leverage stored passwords
• Authentication can leverage existing sessions

Authorization Code
(Separate browser)


Authenticating the user
• Talk about SSO options



• Authorization Page (default template):

Requested
Scope

Partner
Details

23


• After the user authenticates and authorizes access at
the Authorization Service, a callback (via HTTP redirect)
will be made back to the Mobile Client Application.

• Approaches for callback to the native application:
• Use a custom registered URI scheme (e.g.:
mobileapp://oauth-callback?code=xxxx). (Example
follows)
• Use a custom registered MIME-type. A redirect
would send the browser to a HTTP endpoint that
responds with that content-type HTTP header (e.g.:
Content-type: application/mobileapp).
24


• Registering a custom URI scheme in iOS:

25


• Registering a custom URI scheme in Android:

<activity android:name=".MyAppRegisterAccount" android:label="@string/addAccount" >
<intent-filter>
<action android:name="android.intent.action.VIEW"/>
<category android:name="android.intent.category.DEFAULT"/>
<category android:name="android.intent.category.BROWSABLE"/>
<data android:scheme="mymobileapp" />
</intent-filter>
</activity>

26


• Receiving callback – sample code:

- (BOOL)application:(UIApplication *)application handleOpenURL:(NSURL *)url
{
// Schema based application call.
NSLog(@"Schema based call received. URL: %@", url);

NSLog(@"Parsing query string...");
NSMutableDictionary *qsParms = [[NSMutableDictionaryalloc] init];
for (NSString *param in [[url query] componentsSeparatedByString:@"&"]) {
NSArray *elts = [paramcomponentsSeparatedByString:@"="];
if([elts count] < 2) continue;
[qsParmssetObject:[elts objectAtIndex:1] forKey:[elts objectAtIndex:0]];
};

// Process received URL parameters (code, error, etc.)...

27


• Receiving callback – sample code:

@Override
public void onCreate(Bundle savedInstanceState)
{
// Could also be inside onNewInstance depending on the launchMode type
super.onCreate(savedInstanceState);
setContentView(R.layout.main);

Intent intent = getIntent();
Uri uri = intent.getData();

if (uri != null)
{
// Callback from browser link / redirection
// Process received URL parameters (code, error, etc.)...
}

28


• The following parameters are possible on the callback:
• code – the authorization code to resolve the OAuth token
• error – an error code (e.g.: access_denied)
• error_description– descriptive text about the error
• state – the same state value given in the original redirection

• Callback processing:
• The code callback parameter must be subsequentlyresolved
into OAuth tokens by making a REST API call to the
Authorization Server token endpoint .
• If error is present in the callback, the application should
gracefully fail and present a meaningful error to the user
(possibly leveraging error_description).

29


• Example token endpoint Request:

POST /as/token.oauth2 HTTP/1.1
Host: as.example.com
Content-Type: application/x-www-form-urlencoded;charset=UTF-8

grant_type=authorization_code&code=SplxlOBeZQQYbYS6WxSbIA

30


• Example token endpoint Response:

HTTP/1.1 200 OK
Content-Type: application/json;charset=UTF-8
Cache-Control: no-store
Pragma: no-cache

{"token_type":"Bearer","expires_in":60,"refresh_token":"uyAVrtyLZ2qPzI8rQ5
UUTckCdGaJsz8XE8S58ecnt8","access_token":"PeRTSD9RQrbiuoaHVPxV41MzW1qS"}

31


• Handling parameters – sample code:

// Parse of URL query string complete
if (error != nil) {
// TODO: Show error message to user
}
else {
NSString *code = [qsParmsobjectForKey:@"code"];

// Form HTTP POST to resolve JSON structure
NSString*post = [NSStringstringWithFormat:@"grant_type=authorization_code&code=%@",
code];
NSData*postData = [post
dataUsingEncoding:NSASCIIStringEncodingallowLossyConversion:YES];

32


• Handling parameters – sample code (cont'd):

NSString*postLength = [NSStringstringWithFormat:@"%d",
[postDatalength]];
NSMutableURLRequest *request = [[[NSMutableURLRequestalloc] init] autorelease];
[requestsetURL:[NSURL URLWithString:@"https://as.idp.com/as/token.oauth2"]];
[requestsetHTTPMethod:@"POST"];
[requestsetValue:postLengthforHTTPHeaderField:@"Content-Length"];
[requestsetValue:@"application/x-www-form-urlencoded"
forHTTPHeaderField:@"Content-Type"];
[requestsetHTTPBody:postData];

NSURLConnection *conn=[[NSURLConnectionalloc] initWithRequest:requestdelegate:self];
if (conn) {
receivedData = [[NSMutableData data] retain];
}
}

33



- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
// json-framework library: https://github.com/stig/json-framework/
SBJsonParser*jsonParser = [[SBJsonParseralloc] init];
NSString*aStr = [[NSStringalloc] initWithData:receivedDataencoding:NSASCIIStringEncoding];
NSString*accessToken = nil;
NSString*refreshToken = nil;

id object = [jsonParserobjectWithString:aStr];
if (object) {
NSLog(@"JSON parsed successfully.");

if ([object isKindOfClass:[NSDictionary class]]) {
NSDictionary *nsDict = (NSDictionary*)object;
accessToken = [nsDictobjectForKey:@"access_token"];
refreshToken = [nsDictobjectForKey:@"refresh_token"];
}

34


• Handling parameters – sample code:

// Callback from browser link / redirection
String code = uri.getQueryParameter("code");
String error = uri.getQueryParameter("error");

if (error != null)
{
// TODO: Show error message to user
}
elseif (code != null)
{
// Gotauthorizationcode, resolve OAuth tokens. OAuthTaskis an AsyncTask
// tomakenetworkcalls(which must be off themainapplicationthread)
OAuthTasktask = newOAuthTask();
task.execute(new String[] { code });
}

35



private class OAuthTask extends AsyncTask<String, String, String>
{ @Override
protected String doInBackground(String... params)
{
String result = null;
try {
// param[0] = authorization code
JSONObjectjsonObject = getJSONFromTokenEndpoint(params[0]);

String accessToken = (String)jsonObject.get("access_token");
String refreshToken = (String)jsonObject.get("refresh_token");

// TODO: Use tokens
}
catch (Exception e) { // Errorhandling, etc. }
}
} 36

Using a Token

• Once an access_token is obtained, it can be used in the REST API call
to the Resource Server.
• "Bearer" tokens should be inserted into an HTTP Authorization header.
They may also appear in the query string or request body.
• Example REST API Request:

POST /msg/api HTTP/1.1
Host: rs.pingidentity.com
Authorization: Bearer PeRTSD9RQrbiuoaHVPxV41MzW1qS

msg=This%20is%20a%20test%20message.%20%20Please%20respond.

38

Using a Token (cont'd)

• Sample code:

// Form the Bearer token Authorization header
NSString*authzHeader = [NSStringstringWithFormat:@"Bearer %@", accessToken];

NSMutableURLRequest*request = [[[NSMutableURLRequestalloc] init] autorelease];
[request setURL:[NSURL URLWithString:@"https://rs.idp.com/msg/api"]];
[request setValue:authzHeaderforHTTPHeaderField:@"Authorization"];

NSLog(@"Initiating URL connection to RS with access_token...");
NSURLConnection*conn=[[NSURLConnectionalloc] initWithRequest:requestdelegate:self];

39

Using a Token (cont'd)

• Sample code:

// Helper function to create HTTPS POST connections
HttpsURLConnectioncreateHttpsPostConnection(String urlString) throws IOException
{
URL url = new URL(urlString);
URLConnectionurlConn = url.openConnection();
HttpsURLConnectionhttpsConn = (HttpsURLConnection) urlConn;

httpsConn.setRequestMethod("POST");
httpsConn.setDoOutput(true);
return httpsConn;
}
// ... Making RS call:
{
HttpsURLConnectionhttpsConn = createHttpsPostConnection(RS_API_ENDPOINT);
httpsConn.setRequestProperty("Authorization", "Bearer " + accessToken);
OutputStreamWriterwriter = new OutputStreamWriter(httpsConn.getOutputStream());
writer.flush();
} © 2010 Ping Identity Corporation
40

Refreshing a Token

• The JSON structure returned by the token endpoint containing the
access_tokenalso contains other useful parameters – namely:
• expires_in – number of seconds before access_token can no
longer be used.
• refresh_token – can be stored persistently to request another
access_token after expiry. Secure storage should be used (e.g.:
iOS keychain).

{"token_type":"Bearer",
"expires_in":60,
"refresh_token":"uyAVrtyLZ2qPzI8rQ5UUTckCdGaJsz8XE8S58ecnt8",
"access_token":"PeRTSD9RQrbiuoaHVPxV41MzW1qS"}

42

Native Integration
Refreshing a Token (cont’d)
Ping specific:
• To refresh an access token after expiry, The partner OAuth client as
use the refresh token to make a call to defined in PingFederate must
the token endpoint. have assigned (at a minimum)
the Refresh Grant Type.
Additional token mapping
• Example Request: configuration is also required for
persistent grants.

POST /as/token.oauth2 HTTP/1.1
Host: as.pingidentity.com

grant_type=refresh_token&refresh_token=qANLTbu17rk17lPszecHRi7rqJt46pG1qx0
nTAqXWH

43

Native Client Integration
Refreshing a Token (cont’d)

• The JSON response structure will contain an access token, expiry and type
details – and depending on policy - a refresh token to replace the
previously one sent.

• Example JSON response structure:

{"token_type":"Bearer",
"expires_in":60,
"refresh_token":"5HmQjHHP6lGDDWxNh3tuwCzxtRjl95xYnVgvrfh5Kt",
"access_token":"sqhZPzxb7IAIa4kxdyLDJpxpgTFj"}

Ping Specific : The default policy in PingFederate is to roll the refresh token on each use. Once a
refresh token is returned in the response, the previously sent one is rendered invalid.

44

Other options
• Talk about RO Creds etc


Saas webinar-dec6-01

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