How do Django authentication backends authenticate users and resolve permissions?

Explains backend ordering, session affinity, permission aggregation, and the difference between identity and authorization.

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Django calls the configured authentication backends in order until one authenticates the supplied credentials. A backend implements authenticate() and get_user(), and may also provide permission methods. Django stores the successful backend path in the user's session and uses it to load that user later. Authentication success still does not grant every permission or bypass application resource checks.

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Explains backend ordering, session affinity, permission aggregation, and the difference between identity and authorization.

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Explains backend ordering, session affinity, permission aggregation, and the difference between identity and authorization.
Django calls the configured authentication backends in order until one authenticates the supplied credentials. A backend implements authenticate() and get_user(), and may also provide permission methods. Django stores the successful backend path in the user's session and uses it to load that user later. Authentication success still does not grant every permission or bypass application resource checks.
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Backend order matters when more than one source can accept the same identity. Returning None lets Django try the next backend, while raising stops the authentication attempt. Permission results are normally combined across backends, so one backend granting a permission can be enough. I account for inactive users explicitly because a custom backend can accidentally change the default behavior.

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Assuming backend order never matters
Returning a user without checking account state
Confusing a successful backend with full authorization

How do Django authentication backends authenticate users and resolve permissions?

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