You can also test your actual configuration with ssh-audit: https://github.com/jtesta/ssh-audit
Simple SSH Security
81–90 of 97 posts
Re: Simple SSH Security
#82Earlier quoted context omitted.
I use https://tailscale.com , Teleport looks similar? Or do you prefer one over the other?
Tailscale and Teleport are similar, but operate at different levels of the network stack. Tailscale governs access and routing at L3 in the OSI model. See Hashicorp's Boundary or VPNs for alternatives. As a generalization, Teleport works at L7 -- doing auth and routing at the application protocol (ssh, psql, k8s) level. There are ups and downs to both: L3 is relatively technology agnostic (e.g. you don't need differe…
We use ZSSH based on OpenZiti so that the SSH client itself has zero trust, private connectivity embedded in the SSH client (i.e., clientless) - https://ziti.dev/blog/zitifying-ssh/
Re: Simple SSH Security
#83I've always just used this guide: https://sshaudit.com/hardening_guides.html#rhel8 Any reason why I shouldn't?
If you are using DH kex (RSA), then you probably should regenerate the moduli file instead of just taking the distro’s version and filtering it as outline in your link.
To regenerate the moduli, you run:
ssh-keygen -M generate \
-O bits=4096 \
moduli.candidates
ssh-keygen -M screen \
-f moduli.candidates \
moduli.safe
awk '$5 > 3071' moduli.safe \
| tee /etc/ssh/moduli
Re: Simple SSH Security
#84Earlier quoted context omitted.
What? RSA keys are insecure?
I’m not an expert but I think RSA is discouraged these days because it’s strength is dependent on the key size which is regularly outdated as computers get faster/parallelize. Ten years ago a 512bit key was considered secure but these days I think 4096 is the recommended minimum length for a keypair that’s considered secure. Because of this it requires cycling through keys every now and again which can be tedious and…
As far as I have been able to figure, 2048 bit RSA is good for the ages. It would take some fundamental breakthrough like quantum computing to break. No conceivable incremental improvement in current computing technology will come close to touching it.
Re: Simple SSH Security
#85Earlier quoted context omitted.
The link to Mozilla infosec gives a better reason to disallow root login in ssh: auditing in multi-user environments. I am still unconvinced, though. Auditing can by done by recording the IP address, for instance.
Basing things on source IP is really inexact and easily muddied, though. For instance, the source IP is a workstation or a laptop—now we have to go through DHCP logs to figure out who had that IP address at the time the incident occurred. Or if we've properly implemented source limitations through a bastion host, all we'll see on the end server is the source IP of the bastion host, so we'll need to go to the bastion…
`sudo su -` is always a nuisance. As an individual developer I prefer to ssh as root directly. Even more, I use mosh and connect to hosts with something like `mosh root@host -- screen -xRR -D`.
Enterprisey server management tools issue short-lived keys that they push through backchannels to hosts. Hosts do not have users aside from system or applicaiton users.
Anything else is quickly becoming outdated.
Re: Simple SSH Security
#86Earlier quoted context omitted.
I’m not an expert but I think RSA is discouraged these days because it’s strength is dependent on the key size which is regularly outdated as computers get faster/parallelize. Ten years ago a 512bit key was considered secure but these days I think 4096 is the recommended minimum length for a keypair that’s considered secure. Because of this it requires cycling through keys every now and again which can be tedious and…
As far as I have been able to figure, 2048 bit RSA is good for the ages. It would take some fundamental breakthrough like quantum computing to break. No conceivable incremental improvement in current computing technology will come close to touching it.
> 2048 bit RSA is good for the ages
Estimates shows that state-level factorisation will be readily possible by 2030, and academic-size factorisation by five to ten years after that (this is just using classical computers).
Re: Simple SSH Security
#87Earlier quoted context omitted.
As far as I have been able to figure, 2048 bit RSA is good for the ages. It would take some fundamental breakthrough like quantum computing to break. No conceivable incremental improvement in current computing technology will come close to touching it.
> 2048 bit RSA is good for the ages Estimates shows that state-level factorisation will be readily possible by 2030, and academic-size factorisation by five to ten years after that (this is just using classical computers).
State level factorization is probably somewhere in the 1024 bit RSA range with a Manhattan Project level of effort. The extra difficulty when going to 2048 bits is around a billion (1E9). So that would mean that the estimate assumes that we are going to be able to increase our computing capability by a factor of a billion in ten years. That seems very unlikely to me.
Mooore's law has the number of transistors doubling every 2 years (not for sure faster transistors, just transistors). So for 10 years we get 2^5=32. That seems well short of a billion and it is generally accepted that current technology is going to run into fundamental physical limits fairly soon.
Ignoring physical limits, if Moore's law holds it works out to 60 years for state level attacks on 2048 bit RSA.
Re: Simple SSH Security
#88Earlier quoted context omitted.
> 2048 bit RSA is good for the ages Estimates shows that state-level factorisation will be readily possible by 2030, and academic-size factorisation by five to ten years after that (this is just using classical computers).
State level factorization is probably somewhere in the 1024 bit RSA range with a Manhattan Project level of effort. The extra difficulty when going to 2048 bits is around a billion (1E9). So that would mean that the estimate assumes that we are going to be able to increase our computing capability by a factor of a billion in ten years. That seems very unlikely to me. Mooore's law has the number of transistors doublin…
> State level factorization is probably somewhere in the 1024 bit RSA range with a Manhattan Project level of effort. The extra difficulty when going to 2048 bits is around a billion (1E9). So that would mean that the estimate assumes that we are going to be able to increase our computing capability by a factor of a billion in ten years. That seems very unlikely to me.
I mean, Moore's law is hanging but that doesn't mean that they can just, you know, expand their computer footprint? To be precise, NSA (or is it NRO?) is preparing for a warehouse-size supercomputer and it is conceivable that other countries are bucking up with this.
Plus, after the "let's rely on Moore's law" tactic, chip design has another boost of investment, and it's paying off. IPCs, despite the clocks hovering around 5GHZ, is increasing and specialised chips and immersion and/or sub-zero cooling can boost this further. It's rather exciting after the relative stagnation last decade.
Re: Simple SSH Security
#89Earlier quoted context omitted.
State level factorization is probably somewhere in the 1024 bit RSA range with a Manhattan Project level of effort. The extra difficulty when going to 2048 bits is around a billion (1E9). So that would mean that the estimate assumes that we are going to be able to increase our computing capability by a factor of a billion in ten years. That seems very unlikely to me. Mooore's law has the number of transistors doublin…
> State level factorization is probably somewhere in the 1024 bit RSA range with a Manhattan Project level of effort. The extra difficulty when going to 2048 bits is around a billion (1E9). So that would mean that the estimate assumes that we are going to be able to increase our computing capability by a factor of a billion in ten years. That seems very unlikely to me. I mean, Moore's law is hanging but that doesn't…
>doesn't mean that they can just, you know, expand their computer footprint?
A billion times? Would there be enough money in the world to pay for it? Enough resources?
Re: Simple SSH Security
#90I always wonder if something like Teleport is going to catch on to change this conversation a little bit. https://goteleport.com/
I would also recommend checking out strongDM (I work there). We go a lot further than teleport does in the zero trust world.
See https://www.strongdm.com/compare for comparisons.