Mobile Native app OAuth decision framework Paul Madsen Ping Identity
Premise• Based on a number of different deployment characteristics, you will be led to/from choices you need to make about – How you authenticate the user – How you get the tokens to the native app – The OAuth grant type to use• Note – the rules are not hard & fast• Generally, certain characteristics will tend to preclude particular choices
Characteristics1. Local authn vs 3rd party authn – will the AS authenticate the user of the app itself, or will it rely on SSO from a 3rd party IdP?2. Own app vs do not own app – does the AS/RS create and distribute its own native application (eg Salesforce Chatter) or is the app created by a 3rd party (e.g. Seesmic as client of Chatter)3. Need refresh vs do not need refresh – do you need refresh tokens to enable long-lived SSO?4. Does the app distribution channel guard against rogue apps getting installed and creating a phishing risk?5. Is it important to keep user in application context or not?6. Is the app hybrid, ie a native shell around web app internals?
Key Choices1. User authentication mechanism - Will the app use a browser as the means of getting the user authenticated? If so, will the browser be separate or embedded in the app? If not, will the app collect the user credentials directly?2. OAuth grant type – authz code, implicit, or RO creds?3. Token passing mechanism - If you use a browser for user authentication, how will you get the token from the browser to the native app, via cookie, HTML title, or a custom URI scheme?
User authentication mechanism Embedded External browser Inline browser Custom Authz code Cookie Implicit Title RO Creds OAuth grant typeToken passing mechanism
Embedded External browser Inline browser Need 3rd party authn?Custom Authz code Cookie Implicit Title RO Creds Justification – if you need 3rd party authn, you likely want a browser for SSO. The alternative is collecting the creds in the app, and having the AS proxy the verification
Embedded External browser Inline browser Don’t own app?Custom Authz code Cookie Implicit Title RO Creds Justification – if the AS/RS doesn’t distribute its own app, it shouldnt ask user to enter creds into a 3rd party app, or into an embedded browser, in which the native app could see passwords presented
Embedded External browser Inline browser Need refresh?Custom Authz code Cookie Implicit Title RO Creds Justification – the implicit grant doesn’t support refresh tokens
Embedded External browser Inline browser Phishing risk?Custom Authz code Cookie Implicit Title RO Creds Justification – if the app distribution channel cant guarantee a rogue app cant claim the custom scheme, may lead to preference for embedded browser or inline
Embedded External browser Inline browser Keep user in app context?Custom Authz code Cookie Implicit Title RO Creds Justification - external browser takes user out of application context. And if you are embedding the browser, the custom scheme may be unnecessary overhead.
Embedded External browser Inline browser Hybrid app?Custom Authz code Cookie Implicit Title RO Creds Justification - a hybrid app relies on an embedded browser by definition.
Comparison of different authn models Embedded browser Inline •No need to leave app context •Pwd shared with 3rd party •Enables SSO •App owns login UI •Enables strong authn •AS owns login UI •Visual trust cues •Authn can leverage stored pwds •Authn can leverage existing sessions Separate browser