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Why it’s not removed: backward compatibility I bet. I have to maintain a few VM’s and statically linked tools specifically for interacting with old network app

Why it’s not removed: backward compatibility I bet. I have to maintain a few VM’s and statically linked tools specifically for interacting with old network appliances that modern Linux hosts won’t “talk to” without crippling their SSL/TLS configuration or doing other horrendous workarounds like specific OpenSSL/OpenSSH config files for those things. It’s actually an interesting problem when performing security assessments - some tools for scanning will have false negatives because they can’t “talk to” old shit.

jopsen 2y ago
Couldn't you just fallback to HTTP/1.1? I guess it could be that it's not possible.
hannob 2y ago
You have some VMs that talk to old network appliances that require NPN? And if NPN is not supported they don't just fall back to simple HTTP/1.1? I find that sounds extremely unlikely. I am of course well aware of backwards compatibility issues. But I don't see how they'd impact NPN. You might have to update some code that hard-codes NPN functionality, but well, OpenSSL has done API changes in the past, quite significantly so.
- throwway120385 2y ago
  Not OP, but I have some old network-connected appliances in the field that I can't upgrade and that our current OpenSSH clients have deprecated all of the ciphers and methods for. You still have to be able to talk to these things over the network, and ideally you'd want to upgrade at least some of the systems out there. You have to understand that outside of silicon valley and the hobbyist realm there are tons and tons of systems out there where the security posture is "don't allow anyone to have physical or network access to these systems who doesn't belong here" because the companies that made them deprecated them a decade ago or they were built before the widespread practice of supporting the Linux BSP for more than a couple of months. These systems still work and you won't convince very many users of these systems to spend a bunch of money upgrading them for some notional security risk. You may also be working for a company that is contractually obligated to support these systems in some way. So what do you do? In many cases, you do the best you can to mitigate the risks you know are there with tools like firewalls, port knocking, non-standard ports, and so on. And you hope that the 2-3% of attackers that actually know what they're doing never try to crack these things.
  - hannob 2y ago
    I understand what you write, yet it doesn't have anything to do with NPN. Look, I get it. Deprecating things has tradeoffs. But NPN looks like an incredibly safe thing to deprecate. It has only been used for a very short timeframe. Its only use case (SPDY) has a fallback (HTTP/1.1) making sure things still work if it's not supported. Your story about OpenSSH ciphers has nothing to do with it.
    - throwway120385 2y ago
      It's hard sometimes to even upgrade the software to the version that deprecates it. I think that was hard to get from my nonsensical story about tying an onion to my belt.
    - fsckboy 2y ago
      OP couldn't talk to the old devices he used to, he installed some VMs with old stuff, that solved the problem. It's an adequate solution, why spend any more time on it?
  - fullspectrumdev 2y ago
    I have the exact same issue with OpenSSH on an absurdly regular basis, which is why I maintain a set of statically compiled versions and VM’s with old versions - just so I can actually talk to old appliances/hardware. I noticed also that some of the security scanning tools we use “silent fail” on some old appliances because they can no longer negotiate the appropriate SSH connection due to library updates :)
- fullspectrumdev 2y ago
  I was speaking in the more general case with regards OpenSSL - not NPN specific: where changes in OpenSSL have caused stupid devices that I have no control over to become “unmanageable”, hence having to either build static tools or use an ancient VM. I wish I could replace these old devices, and I recommend to do so, but usually replacing them won’t happen until they physically break. Think: Industrial IoT devices at client sites and other such security horrors.
Am4TIfIsER0ppos 2y ago
> without crippling their SSL/TLS configuration On that point: why is the previously allowed crypto settings now considered as good as nothing? I have to force SECLEVEL=0 for openvpn/openssl to allow connecting to my company's vpn. From my reading that would allow any old cipher or hash rather than the previous minimum. Why is the previous level not kept as M and the library bumps the default to N? I know that a theoretical weakness means M is vulnerable to breaking but you force people to make it even worse. I think my boss hasn't updated his openvpn so he doesn't have new openssl so he never saw the problem. His company, his problem.
- tialaramex 2y ago
  People aren't anywhere close to sophisticated enough to make meaningful use of this more complicated functionality. What they're going to do if given this is call your hypothetical "SECLEVEL=M" feature secure and then be outraged when it isn't. If nobody is attacking you, no security will work fine. If you are being attacked, obsolete security likely won't help anyway.
  - throwway120385 2y ago
    If you think of the ideal attacker as having a range of abilities and knowledge between "I found this tool on BitTorrent and am now going to try cracking your network from the outside with it" to "I spread my port scans out to multiple exit nodes over several days so you don't even notice me doing it" then having any security is better than nothing. All you have to do is make the sliver on the venn diagram of people who are trying to attack your system versus people who know how to attack your system as small as possible. It's not rocket science, and there are a lot of factors to balance here beyond the security level of a particular cipher.
  - pixl97 2y ago
    I'm not sure if you've ever plugged into the internet, but there are constant probes occurring. They may not be an attack but simple information gathering that is used later (say someone finds a weakness in your configuration) and you and everything like you is attacked at once.
ctz 2y ago
> Why it’s not removed: backward compatibility I bet. I mean, in the intervening period there was OpenSSL 3 which was a large backwards-incompatible (API and ABI) release, with a huge amount of effort on the part of OpenSSL developers and users to follow along. It was the ideal opportunity to drop this sort of old stuff.

jopsen 2y ago

Couldn't you just fallback to HTTP/1.1? I guess it could be that it's not possible.

hannob 2y ago

You have some VMs that talk to old network appliances that require NPN? And if NPN is not supported they don't just fall back to simple HTTP/1.1? I find that sounds extremely unlikely. I am of course well aware of backwards compatibility issues. But I don't see how they'd impact NPN. You might have to update some code that hard-codes NPN functionality, but well, OpenSSL has done API changes in the past, quite significantly so.

throwway120385 2y ago
Not OP, but I have some old network-connected appliances in the field that I can't upgrade and that our current OpenSSH clients have deprecated all of the ciphers and methods for. You still have to be able to talk to these things over the network, and ideally you'd want to upgrade at least some of the systems out there. You have to understand that outside of silicon valley and the hobbyist realm there are tons and tons of systems out there where the security posture is "don't allow anyone to have physical or network access to these systems who doesn't belong here" because the companies that made them deprecated them a decade ago or they were built before the widespread practice of supporting the Linux BSP for more than a couple of months. These systems still work and you won't convince very many users of these systems to spend a bunch of money upgrading them for some notional security risk. You may also be working for a company that is contractually obligated to support these systems in some way. So what do you do? In many cases, you do the best you can to mitigate the risks you know are there with tools like firewalls, port knocking, non-standard ports, and so on. And you hope that the 2-3% of attackers that actually know what they're doing never try to crack these things.
- hannob 2y ago
  I understand what you write, yet it doesn't have anything to do with NPN. Look, I get it. Deprecating things has tradeoffs. But NPN looks like an incredibly safe thing to deprecate. It has only been used for a very short timeframe. Its only use case (SPDY) has a fallback (HTTP/1.1) making sure things still work if it's not supported. Your story about OpenSSH ciphers has nothing to do with it.
  - throwway120385 2y ago
    It's hard sometimes to even upgrade the software to the version that deprecates it. I think that was hard to get from my nonsensical story about tying an onion to my belt.
  - fsckboy 2y ago
    OP couldn't talk to the old devices he used to, he installed some VMs with old stuff, that solved the problem. It's an adequate solution, why spend any more time on it?
- fullspectrumdev 2y ago
  I have the exact same issue with OpenSSH on an absurdly regular basis, which is why I maintain a set of statically compiled versions and VM’s with old versions - just so I can actually talk to old appliances/hardware. I noticed also that some of the security scanning tools we use “silent fail” on some old appliances because they can no longer negotiate the appropriate SSH connection due to library updates :)
fullspectrumdev 2y ago
I was speaking in the more general case with regards OpenSSL - not NPN specific: where changes in OpenSSL have caused stupid devices that I have no control over to become “unmanageable”, hence having to either build static tools or use an ancient VM. I wish I could replace these old devices, and I recommend to do so, but usually replacing them won’t happen until they physically break. Think: Industrial IoT devices at client sites and other such security horrors.

Am4TIfIsER0ppos 2y ago

> without crippling their SSL/TLS configuration On that point: why is the previously allowed crypto settings now considered as good as nothing? I have to force SECLEVEL=0 for openvpn/openssl to allow connecting to my company's vpn. From my reading that would allow any old cipher or hash rather than the previous minimum. Why is the previous level not kept as M and the library bumps the default to N? I know that a theoretical weakness means M is vulnerable to breaking but you force people to make it even worse. I think my boss hasn't updated his openvpn so he doesn't have new openssl so he never saw the problem. His company, his problem.

tialaramex 2y ago
People aren't anywhere close to sophisticated enough to make meaningful use of this more complicated functionality. What they're going to do if given this is call your hypothetical "SECLEVEL=M" feature secure and then be outraged when it isn't. If nobody is attacking you, no security will work fine. If you are being attacked, obsolete security likely won't help anyway.
- throwway120385 2y ago
  If you think of the ideal attacker as having a range of abilities and knowledge between "I found this tool on BitTorrent and am now going to try cracking your network from the outside with it" to "I spread my port scans out to multiple exit nodes over several days so you don't even notice me doing it" then having any security is better than nothing. All you have to do is make the sliver on the venn diagram of people who are trying to attack your system versus people who know how to attack your system as small as possible. It's not rocket science, and there are a lot of factors to balance here beyond the security level of a particular cipher.
- pixl97 2y ago
  I'm not sure if you've ever plugged into the internet, but there are constant probes occurring. They may not be an attack but simple information gathering that is used later (say someone finds a weakness in your configuration) and you and everything like you is attacked at once.

ctz 2y ago

> Why it’s not removed: backward compatibility I bet. I mean, in the intervening period there was OpenSSL 3 which was a large backwards-incompatible (API and ABI) release, with a huge amount of effort on the part of OpenSSL developers and users to follow along. It was the ideal opportunity to drop this sort of old stuff.