1601735 - Untrusted and expired cert shows expiry message that implies it is trusted

Status: RESOLVED DUPLICATE of bug 1524323

(Firefox :: Security, defect, P3)

Description

[u652468]

User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Firefox/68.0

Steps to reproduce:

Create a self-signed certificate that expires yesterday.
Start MITM attack.
(Or connect to router settings page with expired, self-signed certificate over https)

Actual results:

User connects and sees potential security risk screen and clicks advanced.
"Websites prove their identity via certificates, which are valid for a set time period. The certificate for <website> expired on <yesterday>."
They assume the site forgot to renew their certificate which only expired yesterday, so they ignore the error and continue.

Below the message is the more important information: "Error code: SEC_ERROR_UNKNOWN_ISSUER", but the user is unlikely to read this as it has less details and is usually (and should probably always be) redundant.
I saw this on a page for 192.168.200.1 which expired on 9/6/2006, but I assume the date and domain make no difference.

Expected results:

The user should at least be primarily warned that the certificate is untrusted as the expiration date is irrelevant if we don't trust it anyway. The error code seems to be handled appropriately, but the message provided with it is not.

Comment 1

[u652468]

I signed in through github and wasn't aware my email would be made public. Please let me know once it's ok to disable my account.

Comment 2

[u652468]

This also occurs on desktop version 70 and desktop 68.2.0esr, however 68.2.0esr on Android (as Fennec F-Droid) shows "<website> uses an invalid security certificate. The certificate is not trusted because it is self-signed."

Comment 3

[Daniel Veditz [:dveditz]]

The text you've quoted is from the "Advanced" box once you've expanded it. Just so everyone's on the same page I'll include some STR that don't require generating a cert and running a server, and follow with some resulting screenshots.

1. Set your system clock far in the future. For the sites below Nov 2021 or later is currently fine.
2. Visit https://badssl.com/
3. Click the Advanced button (do NOT add the exception)
4. Visit https://untrusted-root.badssl.com/
5. Click the Advanced button (do NOT add the exception)

https://badssl.com/ has a perfectly fine certificate that currently expires in Oct 2021. Step 2 shows the main text which talks about the cert being expired and your clock being wrong. The advanced box has the text "s" quotes in comment 0 but the error code SEC_ERROR_EXPIRED_CERTIFICATE.

unrusted-root.badssl.com will have an untrusted cert that is also expired. The main text will talk about the server being misconfigured. The Advanced box will be as described in comment 0.

Comment 4

[Daniel Veditz [:dveditz]]

Attachment: Expired but otherwise OK

Comment 5

[Daniel Veditz [:dveditz]]

Attachment: Expired but otherwise OK (advanced box open)

Comment 6

[Daniel Veditz [:dveditz]]

Attachment: Unknown issuer and expired

Comment 7

[Daniel Veditz [:dveditz]]

Attachment: Unknown issuer and expired (advanced box open)

Comment 8

[Daniel Veditz [:dveditz]]

Attachment: EXPECTED advanced text

Comment 9

[Daniel Veditz [:dveditz]]

When there are multiple errors we correctly show the main page and error code of the "worst" error (expired is always least worst), but we select the wrong text for the Advanced box. We can hope that people follow our "Go Back" recommendation, and hope that advanced people will look at the error code, but we should fix the text because that's a lot of wishful thinking :-)

This doesn't need to be hidden as a security bug because knowing about the problem will help people more than it will help attackers (no decent attacker is going to take the risk on an interstitial error page alerting suspicions). I've moved it to MoCo confidential until "s" can change their email.

s: disabling your account will not hide your email. You may be able to file a request to have your account deleted entirely (I think the ability to do that is a GPDR requirement, but I'm not sure) but it may be easier to change your account's email address to some throwaway-mail service like mailinator. Has to be real enough that you can verify receipt of mail at that address. Like many other sites we might block some of the obvious services (like mailinator) so YMMV.

needinfo Johann since he worked on these pages and might know if someone else has taken over since.

Comment 10

[u652468]

Thanks for all your work on this. The account page says disabling removes email, but I changed it too just in case (an option which I somehow missed before).

Comment 11

[Johann Hofmann [:johannh]]

Ok, opening up then. I feel like there's a dupe of this somewhere already.

Comment 12

[Johann Hofmann [:johannh]]

Ah, yes.

Comment 13

[sandwichs]

Thank you for reporting this in detail.
I learned to rely on these explanation texts. I almost clicked through a "bening expiration warning"

I am not very happy that this got duped to 1524323, which fails to recognize the security implication