Hi OpenSSH devs,
I’m wondering if the following has any merit and can be done securely ...
If you could match on principals in the sshd_config, then (for example) on a gateway machine, you could have something like
/etc/ssh/authorized_keys/sshfwd:
cert-authority,principals=“batcha-fwd,batchb-fwd” ...
/etc/ssh/sshd_config containing:
Match User sshfwd
PubkeyAuthentication yes
PasswordAuthentication no
GatewayPorts no
AllowTcpForwarding yes
HostbasedAuthentication no
AllowAgentForwarding no
X11Forwarding no
Banner none
ForceCommand /bin/false
AuthorizedKeysFile /etc/ssh/authorized_keys/%u
Match Principal batcha-fwd
PermitOpen 10.0.0.1:22
Match Principal batcha-fwd
PermitOpen 10.0.0.2:22
This would mean that on the ssh gateway machine, you don’t need an account for every remote batch account that needs to connect, assuming that a signed key has previously been provided with appropriate principals (and maybe source-addresses etc). They would be configured to use something like the following in their ssh config file
Host sshgw.example.com <http://sshgw.example.com/>
User sshfwd
ProxyJump none
Host *.example.com
IdentitiesOnly yes
IdentityFile batcha
User batcha
ProxyJump batcha
I can also see other potential uses for it on target computers where I only allow connections using keys signed by a trusted CA.
Regards,
Bret
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