REQ023 Use QR codes, email links or other out-of-bound channel to exchange authorized tokens

Depends On:

• REQ011 OAuth2 administrator can register clients manually

It turns out to be security risk to exchange tokens using email links or QR codes. E-mails and smartphone camera can be accessed by other native applications that can steal the content. There are similar threats as described in [RFC draft] OAuth 2.0 for Native Apps with the only standard solution now of using PKCE [RFC 7636].

Because PKCE requires two-way communication between client and server but QR/emails is only one-way, it’s not possible to exchange security tokens this way.

However, there is another option for use of QR codes / email links to ease native clients integration: REQ024 [RFC draft] OAuth 2.0 Device Flow. This flow enables limited devices to be authorized using a PIN.

Prior starting the Device Flow, the client must be registered in portal and native application must obtain a random but public “client_id”. This “client_id” together with other metadata like authorization URLs and supported scopes can be provided as QR code or via email.