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)
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(Reporter: 174780597, Unassigned)
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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.
Comment 1•3 years ago
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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.
Comment 2•3 years ago
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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.
(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.
Comment 4•3 years ago
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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.
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