OAuth is an open standard for authorization. OAuth provides client applications a 'secure delegated access' to server resources on behalf of a resource owner. It specifies a process for resource owners to authorize third-party access to their server resources without sharing their credentials.

 

 

Inside SharePoint 2013 OAuth Context TokensGP0|#f573dc2f-c5f4-41fa-a51a-97d9709762c7;L0|#0f573dc2f-c5f4-41fa-a51a-97d9709762c7|OAuth;GTSet|#68e31ecf-dbe9-45e0-8a3c-fc6bd6ad0ce6;GPP|#6553c9ac-7cd3-4c35-9ee0-494641495101;GPP|#1b064965-36f6-40b1-a474-78053852e564;GPP|#74f9ea2a-fcec-489f-9ca4-da563b559213;GP0|#afeedca3-6eba-4b1c-9465-f1b1f76d3e3d;L0|#0afeedca3-6eba-4b1c-9465-f1b1f76d3e3d|Apps;GPP|#a5205c2f-ad79-446f-8d9e-afd0eeecf427 ​This post will show you how to inspect the SharePoint 2013 context token to better understand how OAuth is used in SharePoint 2013 apps
OAuth and the Rehydrated User in SharePoint 2013 GP0|#f573dc2f-c5f4-41fa-a51a-97d9709762c7;L0|#0f573dc2f-c5f4-41fa-a51a-97d9709762c7|OAuth;GTSet|#68e31ecf-dbe9-45e0-8a3c-fc6bd6ad0ce6;GPP|#6553c9ac-7cd3-4c35-9ee0-494641495101;GPP|#1b064965-36f6-40b1-a474-78053852e564;GPP|#74f9ea2a-fcec-489f-9ca4-da563b559213 ​Why inter-farm service application authentication requires users to be in the User Profile Service.