# Az - Pass the Cookie

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## Why Cookies?

Browser **cookies** are a great mechanism to **bypass authentication and MFA**. Because the user has already authenticated in the application, the session **cookie** can just be used to **access data** as that user, without needing to re-authenticate.

You can see where are **browser cookies located** in:

{{#ref}}
https://book.hacktricks.wiki/en/generic-methodologies-and-resources/basic-forensic-methodology/specific-software-file-type-tricks/browser-artifacts.html#google-chrome
{{#endref}}

## Attack

The challenging part is that those **cookies are encrypted** for the **user** via the Microsoft Data Protection API (**DPAPI**). This is encrypted using cryptographic [keys tied to the user](https://book.hacktricks.wiki/en/windows-hardening/windows-local-privilege-escalation/dpapi-extracting-passwords.html) the cookies belong to. You can find more information about this in:

{{#ref}}
https://book.hacktricks.wiki/en/windows-hardening/windows-local-privilege-escalation/dpapi-extracting-passwords.html
{{#endref}}

With Mimikatz in hand, I am able to **extract a user’s cookies** even though they are encrypted with this command:

```bash
mimikatz.exe privilege::debug log "dpapi::chrome /in:%localappdata%\google\chrome\USERDA~1\default\cookies /unprotect" exit
```

For Azure, we care about the authentication cookies including **`ESTSAUTH`**, **`ESTSAUTHPERSISTENT`**, and **`ESTSAUTHLIGHT`**. Those are there because the user has been active on Azure lately.

Just navigate to login.microsoftonline.com and add the cookie **`ESTSAUTHPERSISTENT`** (generated by “Stay Signed In” option) or **`ESTSAUTH`**. And you will be authenticated.

## References

- [https://stealthbits.com/blog/bypassing-mfa-with-pass-the-cookie/](https://stealthbits.com/blog/bypassing-mfa-with-pass-the-cookie/)

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