Closed Bug 1719423 Opened 3 years ago Closed 3 years ago

Firefox will give no warnings if my self-signed CA certificate with md5 is added and trusted for verifying website on Ubuntu 18.04.

Categories

(Core :: Security: PSM, enhancement)

Firefox 89
enhancement

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()

RESOLVED WONTFIX

People

(Reporter: 174780597, Unassigned)

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(1 file)

1.02 MB, application/x-zip-compressed
Details
Attached file md5.zip

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.124 Safari/537.36

Steps to reproduce:

I used OpenSSL to issue a self-signed CA certificate with a digest algorithm of MD5 and generated a website certificate, which was deployed on my website (https://www.felixlab.shop). I tried to visit this website in Firefox. (We compressed the certificate file and screenshots and put them in the attached file.)

Actual results:

When I did not add the CA certificate to Firefox, the browser blocked my access and prompted "SEC_ERROR_CERT_SIGNATURE_ALGORITHM_DISABLED." But when I added the CA certificate and trusted it to verify a website, this website can be accessed normally without any security warnings. (But the Safari browser of macOS will tell me that the signature algorithm has security issues even if I trusted the CA certificate.)

Expected results:

Firefox should still give us a security warning that the signature algorithm of the CA certificate is insecure even if it is trusted and should not directly allow access.

The Bugbug bot thinks this bug should belong to the 'Core::Security: PSM' component, and is moving the bug to that component. Please revert this change in case you think the bot is wrong.

Component: Untriaged → Security: PSM
Product: Firefox → Core

To make sure I understand you, only the self-signature of the CA uses MD5, right? If that's the case, since that certificate is marked as a trust anchor, the data it contains is considered trustworthy, so the signature on it (and therefore signature algorithm) doesn't get checked.

Flags: needinfo?(174780597)

(In reply to Dana Keeler (she/her) (use needinfo) (:keeler for reviews) from comment #2)

To make sure I understand you, only the self-signature of the CA uses MD5, right? If that's the case, since that certificate is marked as a trust anchor, the data it contains is considered trustworthy, so the signature on it (and therefore signature algorithm) doesn't get checked.
You are right, and only the self-sighed CA certificate uses MD5. But I think Firefox should check the algorithm for security.

Flags: needinfo?(174780597)

By marking it as a trust anchor, you've indicated that you trust it. Firefox doesn't need to check its signature at that point.

Status: UNCONFIRMED → RESOLVED
Closed: 3 years ago
Resolution: --- → WONTFIX

Thank you!

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