intermittent report of invalid SSL certificate: but only when I connect via virginmedia

[andrew91]

Over the last few months I have seen an intermittent problem when
connecting to my internet banking website (using https).
On each occasion the problem remains constant for a few days,
then goes away for a while.

Details of the problem are below.

BUT this problem only happens when I am using my Virginmedia internet
connection.
If I switch my connection to BT or EE, the problem never occurs.

To work around the problem I just have to disconnect from VM and connect
via BT or EE - no reboots, no browser restarts, no clearing the cache
etc; just switch from one ISP to another.
But when I go back to my VM connection the problem comes back.

After a few days the problem goes away ... until next time ...

I have also seen this problem (once) when connecting to a particular
page on a UK government website that used https
(I forget which one now).
But connections to other https pages on the same site worked fine.

Because, when it happens, it ONLY happens when connecting via VM
broadband and not when connecting via BT or EE, it looks a lot like the
problem is with VM rather than with the website or with my browsers.

So I wonder what is it about the VM connection that causes this
intermittent problem.
Maybe it is something to do with VM's transparent proxy servers?

Has anyone else seem this kind of issue?
Or does anyone have any idea how I could contact someone at VM who
would even understand the issue?

thanks
andrew

Details
This is on an apple macbook with firefox and safari browsers.
Since the machine runs macos, it typically stays up for months
between reboots.
I normally connect to the internet using Virgin Media broadband
service that is part of VM's cable TV network.

If I connect to my online banking service (RBS) using firefox
(my preferred browser) I get a page that says:

     The page isn't directing properly

[and no other useful information]

But if I connect using safari, I get rather more information about the
problem.
First I get a page that says:

     This connection is not private

Then, if I select "Show Details", it says that the site's certificate is
not valid.
Then, if I select "view the certificate", it shows details of a
certificate issued by COMODO CA Limited to Royal Bank of Scotland,
and says:

     This certificate was signed by an untrusted user

Assuming that the certificate is actually signed by a trusted user,
and considering that the problem only occurs when I connect using VM,
it looks like something in VM's network may be corrupting the certificate.

[Tom_F]

Hi andrew91, thanks for your post.

Sorry to hear you've encountered this problem. 

Is the hub running in router or modem mode when this happens? If you haven't already - please try a factory reset and let us know if that helps:

With the Hub turned on, push the pinhole button all the way in and hold it there for a timed 60 seconds. Bear in mind your Hub settings and your passwords/passphrase for both the WiFi networks & settings will revert to the two printed on the Hub sticker on its base/side/card so all devices will need to be reconnected manually.  

Tom

[用心棒]

It maybe useful to know the fingerprint of each certificate within the chain when this problem next occurs.

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[andrew91]

Thanks for your response.
I have tried power-cycling the router when the problem happens, but it makes no difference.
I don't now remember whether I tried pressing the reset button; but will do so next time the problem occurs.

[andrew91]

This problem has happened again - details in my original post dated 8th July.

Tom_F suggested that I should reset my VM router - I did this, but it made no difference - so what next?

用心棒 wanted details of the certificates - safari doesn't seem to support printing of certificate info, so I took screenshots and uploaded them here: https://btcloud.bt.com/web/app/share/invite/Mb1mhrr9Y1 ... then navigate to the directory virginmedia-forum/oneaccount-certificates/via-virginmedia/20200908

(please bear in mind that these files contain screenshots that span more than one screen; so, in each file, some info on the second-to-last page may be replicated on the last page)

Does anyone know if VM still processes web traffic through transparent web proxy servers?  If they do, I wonder if this is the cause of the problem.

[用心棒]

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@andrew91 wrote:
⋮
用心棒 wanted details of the certificates - safari doesn't seem to support printing of certificate info, so I took screenshots and uploaded them here: https://btcloud.bt.com/web/app/share/invite/Mb1mhrr9Y1 ... then navigate to the directory virginmedia-forum/oneaccount-certificates/via-virginmedia/20200908

⋮

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Can you post  these images here; be aware images are moderated so may not appear immediately after posting?

[andrew91]

The screenshots are in PDF files; with each file containing several pages.
It seems that the forum doesn't permit posting files of this type.

Are you not able to access the files using the URL that I provided?

[newapollo]

Strangely enough it's a matter of security.

We are just names on a forum and don't know each other from Adam, so there is a risk involved opening files from sources we don't know?

[用心棒]

There is a Drag and drop here or browse files to attach area below your (new / reply) post's body where PDFs can be attached.

[andrew91]

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@用心棒 wrote:

There is a Drag and drop here or browse files to attach area below your (new / reply) post's body where PDFs can be attached.

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There is ???

This is what I get if I try to drag a PDF file to the message area:

 And this is what I get if I try to attach a PDF file as an image: