When you create an application link between two applications, the Application Links plugin automatically creates a link using OAuth authentication; this authentication method lets logged-in users take advantage of all the integration points between Atlassian applications.
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When you need to change the configuration of an application link
Depending on your permissions when you create an application (or the settings required in the application you are linking to), you might need to modify the authentication settings for an application link after it's been created. There are a few common scenarios in which you might need to change the configuration of an application link:
- You've set up an application link but users still have to authenticate regularly. This can occur when the application link has been configured to not share the same userbase. If those applications do share the same user base, you can update your application link authentication by selecting the Allow user impersonation through 2-Legged OAuth check box on the incoming authentication settings for the application link configuration.
- You want to continue using a link to an application that now allows public sign-on and the link was previously configured with a shared userbase. You can update your application link authentication by clearing the Allow user impersonation through 2-Legged OAuth check box on the incoming authentication settings for the application link configuration.
- You use a plugin that requires a specific authentication type.
Security implications for each authentication type
If you configure OAuth authentication for your application, please be aware of the following security implications:
- Adding an OAuth consumer requires the transmission of sensitive data. To prevent 'man-in-the-middle' attacks, it is recommended that you use SSL for your applications while configuring OAuth authentication.
- Do not link to an application using OAuth authentication, unless you trust all code in the application to behave itself at all times. OAuth consumers are a potential security risk to the applications that they are linked to because of the ability to impersonate users. If your server is compromised, the data there and on linked servers is at risk.
- Note that creating a new application link now uses OAuth by default and enables both 3-legged OAuth (3LO) and 2-legged OAuth (2LO).
- When updating older application links (that perhaps used Trusted Apps authentication) to use OAuth, 3LO is used by default, but you need to explicitly enable 2LO using the check box in the application link configuration settings.
- Only use the 2LO with impersonation option in the application link configuration settings if your servers both have the same set of users and they fully trust each other.
If you configure Trusted Applications authentication for your application (your servers have the same set of users and they fully trust each other), please be aware of the following security implications:
- Trusted applications are a potential security risk. When you configure Trusted Applications authentication, you are allowing one application to access another as any user. This allows all of the built-in security measures to be bypassed. Do not configure a trusted application unless you know that all code in the application you are trusting will behave itself at all times, and you are sure that the application will maintain the security of its private key.
About impersonating and non-impersonating authentication types
Application links allow you to configure 'impersonating' and 'non-impersonating' authentication types:
- Impersonating authentication types make requests on behalf of the user who is currently logged in. People will see only the information that they have permission to see. This includes OAuth and Trusted Applications authentication, and should only be used when two servers share the same user base.
- Non-impersonating authentication types always use a pre-configured user, and not the logged-in user, when making a request. The server handling the request determines the level of access to use, and this is used for requests from all users. This includes basic HTTP authentication.