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Just for fun, most users on Github have RSA keys exclusively. Did you know that your SSH keys are public on Github? https://github.com/taylorotwell.keys https

Just for fun, most users on Github have RSA keys exclusively. Did you know that your SSH keys are public on Github? https://github.com/taylorotwell.keys https://github.com/taylorotwell.keys https://github.com/alexcrichton.keys https://github.com/alexcrichton.keys https://github.com/andrew.keys https://github.com/andrew.keys https://github.com/egoist.keys https://github.com/egoist.keys https://github.com/fabpot.keys https://github.com/fabpot.keys Some of the most popular users even have DSS keys.

egyiedfyfrtjjf 7y ago
As a RSA-user myself, because I learnt about ssh through the github setup guides: Will ssh-keygen generate a secure key if I don’t pass it any parameters?
- RL_Quine 7y ago
  I haven't built the new version, but I assume it defaults to ed25519 now. You can otherwise make one with ssh-keygen -t ed25519.
  - techntoke 7y ago
    Last time I tried AWS doesn't support anything but RSA keys.
    - RL_Quine 7y ago
      That’s right. Nothing stopping you having both though.
    - zenexer 7y ago
      They don’t need to. Boot up a default AMI, change the key to whatever you want, then create your own custom AMI from that. Or you can use something like Cloud-Init.
    - lawnchair_larry 7y ago
      This is good news, because AWS will finally be forced to get with the times. Their certificate manager is stuck on RSA too.
- jlgaddis 7y ago
  It will generate a 2048-bit RSA keypair by default. It will be "a secure key" as long as you protect it with an appropriate passphrase.
  - gnufx 7y ago
    You need recent ssh-keygen's -o to make the passphprase effective (default for ed25519). That was covered here at some stage, but I don't have a reference.
zimmerfrei 7y ago
You are conflating RSA (the algorithm) with "ssh-rsa" (the option of the SSH suite indicating authentication with RSA in combination with SHA-1). They deprecate the latter. Other options also based on RSA such as "rsa-sha2-256/512" are fine and will remain supported. In other words, the security problem is not with RSA per se. Having said that, I have not checked whether the people you list have RSA keys bound to SHA-1...
- deleted 7y ago
  [deleted]
- mkj 7y ago
  The keys themselves are not bound to sha1 or sha256. The hash is just used for the ephemeral signatures during authentication (or certificates as mentioned in the release notes). "ssh-rsa" signature scheme at runtime (sha1) will be deprecated, but rsa keys themselves are fine (edit typo name)
  - tialaramex 7y ago
    Indeed, and so to actually use this $50k attack on SSH you'd need to somehow arrange for your target to pick random numbers you expected so that your attack works. But for clarity, OpenSSH isn't saying this can be used against SSH today - the deprecation is because we should abandon broken hashes before they actually cause us harm, not wait until after. Don't Walk Past.
    - RL_Quine 7y ago
      People are still obviously using 1024 bit RSA keys which are more of a problem.
  - xorcist 7y ago
    Right. Most SSH keys are just keys, not hashes. The hash used for key exchange during authentication is something that is enforced by the server (and client) and not a property of the key. The option in ssh-keygen for a signature algorithm is for signing keys in an SSH CA. This is not something Github supports.
numlock86 7y ago
> Just for fun, most users on Github have RSA keys exclusively. Rare ecdsa-sha2-nistp256 guy here. I'd welcome Brainpool, but support mostly boils down to NIST compromised curves on the majority of applications. sadface > Did you know that your SSH keys are public on Github? Wait, what? Github makes public keys public? Outrageous!
- RL_Quine 7y ago
  It's not intuitive because there's really no need for it.
  - dspillett 7y ago
    No harm in it either though. Unless for some reason someone imports one into their authorized_keys (which presumably would require deliberate steps not random numbskullary) in which case there is a (low) risk as they have just given a dev access to an account said dev does not know exists.
    - RL_Quine 7y ago
      What you described is quite literally a feature in Ubuntu Server. Type in a github username during the installer to import from github.com/%s.keys to /root/.ssh/authorized_keys.
      - tialaramex 7y ago
        My instinct is that's actually safer than a "set your password and open SSH to the world" step.
      - 3fe9a03ccd14ca5 7y ago
        A cronjob on every one of my IoT crap devices, which sometimes stay stuffed in a shoebox without internet for years: @reboot root ssh-import-id gh:my-username That way when I want to tinker with one, it will pull down my newest GitHub once it reboots and I’ll be able to login. The GitHub key is always up to date.
pnutjam 7y ago
Those are just the public portion of the key, not the private key.
- RL_Quine 7y ago
  I didn't say they were private keys.
joeyh 7y ago
github also appears to only have RSA and DSA host keys, the latter is already deprecated

egyiedfyfrtjjf 7y ago

As a RSA-user myself, because I learnt about ssh through the github setup guides: Will ssh-keygen generate a secure key if I don’t pass it any parameters?

RL_Quine 7y ago
I haven't built the new version, but I assume it defaults to ed25519 now. You can otherwise make one with ssh-keygen -t ed25519.
- techntoke 7y ago
  Last time I tried AWS doesn't support anything but RSA keys.
  - RL_Quine 7y ago
    That’s right. Nothing stopping you having both though.
  - zenexer 7y ago
    They don’t need to. Boot up a default AMI, change the key to whatever you want, then create your own custom AMI from that. Or you can use something like Cloud-Init.
  - lawnchair_larry 7y ago
    This is good news, because AWS will finally be forced to get with the times. Their certificate manager is stuck on RSA too.
jlgaddis 7y ago
It will generate a 2048-bit RSA keypair by default. It will be "a secure key" as long as you protect it with an appropriate passphrase.
- gnufx 7y ago
  You need recent ssh-keygen's -o to make the passphprase effective (default for ed25519). That was covered here at some stage, but I don't have a reference.

zimmerfrei 7y ago

You are conflating RSA (the algorithm) with "ssh-rsa" (the option of the SSH suite indicating authentication with RSA in combination with SHA-1). They deprecate the latter. Other options also based on RSA such as "rsa-sha2-256/512" are fine and will remain supported. In other words, the security problem is not with RSA per se. Having said that, I have not checked whether the people you list have RSA keys bound to SHA-1...

deleted 7y ago
[deleted]
mkj 7y ago
The keys themselves are not bound to sha1 or sha256. The hash is just used for the ephemeral signatures during authentication (or certificates as mentioned in the release notes). "ssh-rsa" signature scheme at runtime (sha1) will be deprecated, but rsa keys themselves are fine (edit typo name)
- tialaramex 7y ago
  Indeed, and so to actually use this $50k attack on SSH you'd need to somehow arrange for your target to pick random numbers you expected so that your attack works. But for clarity, OpenSSH isn't saying this can be used against SSH today - the deprecation is because we should abandon broken hashes before they actually cause us harm, not wait until after. Don't Walk Past.
  - RL_Quine 7y ago
    People are still obviously using 1024 bit RSA keys which are more of a problem.
- xorcist 7y ago
  Right. Most SSH keys are just keys, not hashes. The hash used for key exchange during authentication is something that is enforced by the server (and client) and not a property of the key. The option in ssh-keygen for a signature algorithm is for signing keys in an SSH CA. This is not something Github supports.

numlock86 7y ago

> Just for fun, most users on Github have RSA keys exclusively. Rare ecdsa-sha2-nistp256 guy here. I'd welcome Brainpool, but support mostly boils down to NIST compromised curves on the majority of applications. sadface > Did you know that your SSH keys are public on Github? Wait, what? Github makes public keys public? Outrageous!

RL_Quine 7y ago
It's not intuitive because there's really no need for it.
- dspillett 7y ago
  No harm in it either though. Unless for some reason someone imports one into their authorized_keys (which presumably would require deliberate steps not random numbskullary) in which case there is a (low) risk as they have just given a dev access to an account said dev does not know exists.
  - RL_Quine 7y ago
    What you described is quite literally a feature in Ubuntu Server. Type in a github username during the installer to import from github.com/%s.keys to /root/.ssh/authorized_keys.
    - tialaramex 7y ago
      My instinct is that's actually safer than a "set your password and open SSH to the world" step.
    - 3fe9a03ccd14ca5 7y ago
      A cronjob on every one of my IoT crap devices, which sometimes stay stuffed in a shoebox without internet for years: @reboot root ssh-import-id gh:my-username That way when I want to tinker with one, it will pull down my newest GitHub once it reboots and I’ll be able to login. The GitHub key is always up to date.

pnutjam 7y ago

Those are just the public portion of the key, not the private key.

RL_Quine 7y ago
I didn't say they were private keys.

joeyh 7y ago

github also appears to only have RSA and DSA host keys, the latter is already deprecated