Well I know I'm not going to convince you.
Likewise.
The OpenSSL announcement outlines
two distinct scenarios that are vulnerable. I'll break it down:
This issue will impact any application that verifies certificates including SSL/TLS/DTLS clients
This is what I am talking about.
and SSL/TLS/DTLS servers using client authentication.
This is what you are talking about. I don't disagree that this scenario is real, what I am pointing out is that this latter scenario
isn't the only scenario that is open to attack. For servers, yes, the latter scenario is the only scenario that matters. But to be useful, servers must have clients, and clients are affected (but there is nothing the server can do about that).
An HTTPS client performs certificate verification every time it connects to an HTTPS server (the first scenario). E.g. when you visit your online bank. If the client uses a vulnerable OpenSSL, it can be tricked to accept an invalid certificate for the bank.
The paragraph about how the attack works in your latest link is very accurate. The rest isn't.
Who is affected?
Probably [...]
Not very assuring.
Countermeasures
[...] Also, such scenarios with multiple paths for a single certificate might be avoided.
You don't get to choose how other handle their certificate. If someone wants to get their certificate signed by every trusted root CA on the planet, leading to multiple certificate paths, that's their choice. The only way to avoid it is to not use a service that uses a certificate signed by multiple roots. Suggesting this as a countermeasure shows a poor understanding of how certificates work. (Then again, it is written under the assumption that only servers authenticating their clients are affected.)
Some examples: wget is often used to download scripts and code on *NIX computers, the downloaded material may even be executed as root. It may use OpenSSL for TLS support (it also supports other libs). Curl has the same use, and is also used in library form by many
client applications to perform various kinds of connections. It also supports OpenSSL for TLS support. In recommended configurations, both OpenVPN clients and servers are affected, since it does two-way certificate verification. The client verifies the server cert (same as a typical HTTPS web browser), and the server verifies the client cert (which is the part of this vulnerability everyone is able to grasp). However OpenVPN recommendations also suggests use of a shared secret in addition to certificate verification, which will mitigate the vulnerability in both cases.
OpenSSL Patches Critical Certificate Validation Vulnerability
The vulnerability allows an attacker with an untrusted TLS certificate to be treated as a certificate authority and spoof another website. Attackers can use this scenario to redirect traffic, set up man-in-the-middle attacks, phishing schemes and anything else that compromises supposedly encrypted traffic.
/r/sysadmin references:
Joking explanation
Very short explanation
More serious explanation