If you follow any infosec sources you’ve probably already heard a lot about Meltdown and Spectre, Kaiser and KPTI. If not, you’ve probably seen headlines like Major flaw in millions of Intel chips revealed or Intel sells off for a second day as massive security exploit shakes the stock. What is it? These are all about a cluster of related security issues that exploit features shared...
I just got some mail claiming to be from “Bank of America <secure@bofasecure.com>”. It passes SPF: Received-SPF: Pass (sender SPF authorized) identity=mailfrom; client-ip=185.235.176.160; helo=bofasecure.com; It passes DKIM: Authentication-Results: mx.wordtothewise.com (amavisd-new); dkim=pass (1024-bit key) header.d=bofasecure.com The visible RFC 822 From address is strictly...
We often want to know whether two hostnames are controlled by the same person, or not. One case for that is cookie privacy in web browsers. We want pages at www.blighty.com and images.blighty.com and blighty.com to all be able to set and read cookies for each other – so a user only needs to log in once for pages or images on all of them to work well together. So we allow all of them to...
Well, not exactly mandatory but Chrome will start labeling any text or email form field on a non-TLS page as “NOT SECURE”. Chrome 62 will be released as stable some time around October 24th. If you want to avoid the customer support overhead then, regardless of whether any of the information on a form is sensitive, you should probably make sure that all your forms are accessible via...
An email address has two main parts. The local-part is the bit before the @-sign and the domain is the bit after it. Loosely, the domain part tells SMTP how to get an email to the destination mailserver while the local part tells that server whose mailbox to put it in. I’m just looking at the local part today, the “steve” in “steve@example.com”. Talkin’...
Transport Layer Security (TLS) is what gives you the little padlock in your browser bar. Some people still call it SSL, but TLS has been around for 18 years – it’s time to move on. TLS provides two things. One is encryption of traffic as it goes across the wire, the other is a cryptographic proof that you’re talking to the domain you think you’re talking to. The second...
It’s easy to tell if a domain is using SPF – look up the TXT record for the domain and see if any of them begin with “v=spf1”. If one does, they’re using SPF. If none do, they’re not. (If more than one does? They’re publishing invalid SPF.) AOL are publishing SPF. Geocities aren’t. For DKIM it’s harder, as a DKIM key isn’t published at a...
When you link to an external resource – an image, a javascript file, some css style – from a web page you do so with a URL, usually something like “; or “;. The world is beginning to go all https, all the time, but until recently good practice was to make a web page available via both http and https. The problem is that if you try and load a resource from an http URL from...
On Friday I talked a little about DMARC being a negative assertion rather than an authentication method, and also about how and when it could be deployed without causing problems. Today, how DMARC went wrong and a partial fix for it that is coming down the standards pipeline. What breaks? DMARC (with p=reject) risks causing problems any time mail with the protected domain in the From: field is...
We know that legitimate email sent with valid SPF and a DKIM signature often breaks in transit. SPF will fail any time mail is forwarded – via a mailing list, a forwarding service used by the recipient, or just ad-hoc forwarding. DKIM will fail any time the message is modified in transit. That can be obviously visible changes, such as a mailing list tagging a subject header or adding a...
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