Best way to setup sudo authentication on servers that don't use a password?
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With sudo, you can either set it to ask for a password or not ask for a password.
Historically, everything was password-protected, which is the model that I am used to. However, encryption seems to be favoring public/private key authentication more and more nowadays.
This is evident in the fact that when I spin up a server on GCP, AWS, or DigitalOcean, I don't get a password. Instead I get a key that I use to log in.
Now, if I want to do sudo when I am logged in, it doesn't ask me for a password. This is obviously due to the fact that a password was never given to me, only a key was. And sudo doesn't ask for a password because of the following rule in /etc/sudoers.d/90-cloud-init-users:
ubuntu ALL=(ALL) NOPASSWD:ALL
This is fine for one user. But what happens if a server has 3-4 users, all of whom need sudo access, and all of whom are using keys to log in rather than a password. You want to make sure that one user can't do
sudo su - <someone else's username>
sudo <command>
Is the encouraged practice to not allow password authentication when connecting with sshd, but to give all the users a password that is used for sudo authentication? Or to use pam_ssh_agent_auth to allow sudo to authenticate with another set of private/public keys that have a passphrase? Or is there something else that should be done?
sudo key-authentication
edited Dec 25 '18 at 21:12
Peter Mortensen
88358
asked Dec 25 '18 at 12:07
modernNeo
283
add a comment |
With sudo, you can either set it to ask for a password or not ask for a password.
Historically, everything was password-protected, which is the model that I am used to. However, encryption seems to be favoring public/private key authentication more and more nowadays.
This is evident in the fact that when I spin up a server on GCP, AWS, or DigitalOcean, I don't get a password. Instead I get a key that I use to log in.
Now, if I want to do sudo when I am logged in, it doesn't ask me for a password. This is obviously due to the fact that a password was never given to me, only a key was. And sudo doesn't ask for a password because of the following rule in /etc/sudoers.d/90-cloud-init-users:
ubuntu ALL=(ALL) NOPASSWD:ALL
This is fine for one user. But what happens if a server has 3-4 users, all of whom need sudo access, and all of whom are using keys to log in rather than a password. You want to make sure that one user can't do
sudo su - <someone else's username>
sudo <command>
Is the encouraged practice to not allow password authentication when connecting with sshd, but to give all the users a password that is used for sudo authentication? Or to use pam_ssh_agent_auth to allow sudo to authenticate with another set of private/public keys that have a passphrase? Or is there something else that should be done?
sudo key-authentication
edited Dec 25 '18 at 21:12
Peter Mortensen
88358
asked Dec 25 '18 at 12:07
modernNeo
283
add a comment |
With sudo, you can either set it to ask for a password or not ask for a password.
Historically, everything was password-protected, which is the model that I am used to. However, encryption seems to be favoring public/private key authentication more and more nowadays.
This is evident in the fact that when I spin up a server on GCP, AWS, or DigitalOcean, I don't get a password. Instead I get a key that I use to log in.
Now, if I want to do sudo when I am logged in, it doesn't ask me for a password. This is obviously due to the fact that a password was never given to me, only a key was. And sudo doesn't ask for a password because of the following rule in /etc/sudoers.d/90-cloud-init-users:
ubuntu ALL=(ALL) NOPASSWD:ALL
This is fine for one user. But what happens if a server has 3-4 users, all of whom need sudo access, and all of whom are using keys to log in rather than a password. You want to make sure that one user can't do
sudo su - <someone else's username>
sudo <command>
Is the encouraged practice to not allow password authentication when connecting with sshd, but to give all the users a password that is used for sudo authentication? Or to use pam_ssh_agent_auth to allow sudo to authenticate with another set of private/public keys that have a passphrase? Or is there something else that should be done?
sudo key-authentication
edited Dec 25 '18 at 21:12
Peter Mortensen
88358
asked Dec 25 '18 at 12:07
modernNeo
283
With sudo, you can either set it to ask for a password or not ask for a password.
Historically, everything was password-protected, which is the model that I am used to. However, encryption seems to be favoring public/private key authentication more and more nowadays.
This is evident in the fact that when I spin up a server on GCP, AWS, or DigitalOcean, I don't get a password. Instead I get a key that I use to log in.
Now, if I want to do sudo when I am logged in, it doesn't ask me for a password. This is obviously due to the fact that a password was never given to me, only a key was. And sudo doesn't ask for a password because of the following rule in /etc/sudoers.d/90-cloud-init-users:
ubuntu ALL=(ALL) NOPASSWD:ALL
This is fine for one user. But what happens if a server has 3-4 users, all of whom need sudo access, and all of whom are using keys to log in rather than a password. You want to make sure that one user can't do
sudo su - <someone else's username>
sudo <command>
Is the encouraged practice to not allow password authentication when connecting with sshd, but to give all the users a password that is used for sudo authentication? Or to use pam_ssh_agent_auth to allow sudo to authenticate with another set of private/public keys that have a passphrase? Or is there something else that should be done?
sudo key-authentication
sudo key-authentication
edited Dec 25 '18 at 21:12
Peter Mortensen
88358
asked Dec 25 '18 at 12:07
modernNeo
283
edited Dec 25 '18 at 21:12
Peter Mortensen
88358
asked Dec 25 '18 at 12:07
modernNeo
283
edited Dec 25 '18 at 21:12
Peter Mortensen
88358
edited Dec 25 '18 at 21:12
Peter Mortensen
88358
edited Dec 25 '18 at 21:12
Peter Mortensen
88358
88358
asked Dec 25 '18 at 12:07
modernNeo
283
asked Dec 25 '18 at 12:07
modernNeo
283
asked Dec 25 '18 at 12:07
modernNeo
283
283
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
Password authentication for access to sudo doesn't restrict what commands can be run.
eg
myuser ALL=(ALL) NOPASSWD: ALL
youruser ALL=(ALL) ALL
lets both users run exactly the same commands, just you need to enter your password, and I don't.
Instead the idea is to only grant users the privileged commands they need, rather than "ALL" commands. So if user1 only needs to reboot the server you might give them
user1 ALL=(root) NOPASSWD: /usr/sbin/reboot
Now all they can do is reboot the server.
This follows the principle of least privilege; only give people the commands they need.
Further reading: https://www.sweharris.org/post/2018-08-26-minimal-sudo/
answered Dec 25 '18 at 15:14
Stephen Harris
25.2k24477
1
I never said that Password authentication for access to sudo restricts what commands can be run, I said that Password authentication for access to sudo restricts who can run the sudo command when logged in as each user.
– modernNeo
Dec 25 '18 at 20:20
and I want to give my users the ability to run any command they want via sudo, I just want to also make sure that there is a reliable way to authenticate them when they run sudo.
– modernNeo
Dec 25 '18 at 21:20
@modernNeo Password authentication would not prevent a user from running sudo su - youruser.
– user2233709
Dec 25 '18 at 21:40
@user2233709 I am not trying to prevent them from running sudo as themselves but rather running sudo as another user.
– modernNeo
Dec 25 '18 at 22:09
@user2233709 To put it another way, I want to know the best way to prevent someone from being able to run "sudo <command>" after switching to another user when sudo isnt using password authentication.
– modernNeo
Dec 25 '18 at 22:10
|
show 5 more comments
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1 Answer
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votes
Password authentication for access to sudo doesn't restrict what commands can be run.
eg
myuser ALL=(ALL) NOPASSWD: ALL
youruser ALL=(ALL) ALL
lets both users run exactly the same commands, just you need to enter your password, and I don't.
Instead the idea is to only grant users the privileged commands they need, rather than "ALL" commands. So if user1 only needs to reboot the server you might give them
user1 ALL=(root) NOPASSWD: /usr/sbin/reboot
Now all they can do is reboot the server.
This follows the principle of least privilege; only give people the commands they need.
Further reading: https://www.sweharris.org/post/2018-08-26-minimal-sudo/
answered Dec 25 '18 at 15:14
Stephen Harris
25.2k24477
1
I never said that Password authentication for access to sudo restricts what commands can be run, I said that Password authentication for access to sudo restricts who can run the sudo command when logged in as each user.
– modernNeo
Dec 25 '18 at 20:20
and I want to give my users the ability to run any command they want via sudo, I just want to also make sure that there is a reliable way to authenticate them when they run sudo.
– modernNeo
Dec 25 '18 at 21:20
@modernNeo Password authentication would not prevent a user from running sudo su - youruser.
– user2233709
Dec 25 '18 at 21:40
@user2233709 I am not trying to prevent them from running sudo as themselves but rather running sudo as another user.
– modernNeo
Dec 25 '18 at 22:09
@user2233709 To put it another way, I want to know the best way to prevent someone from being able to run "sudo <command>" after switching to another user when sudo isnt using password authentication.
– modernNeo
Dec 25 '18 at 22:10
|
show 5 more comments
Password authentication for access to sudo doesn't restrict what commands can be run.
eg
myuser ALL=(ALL) NOPASSWD: ALL
youruser ALL=(ALL) ALL
lets both users run exactly the same commands, just you need to enter your password, and I don't.
Instead the idea is to only grant users the privileged commands they need, rather than "ALL" commands. So if user1 only needs to reboot the server you might give them
user1 ALL=(root) NOPASSWD: /usr/sbin/reboot
Now all they can do is reboot the server.
This follows the principle of least privilege; only give people the commands they need.
Further reading: https://www.sweharris.org/post/2018-08-26-minimal-sudo/
answered Dec 25 '18 at 15:14
Stephen Harris
25.2k24477
1
I never said that Password authentication for access to sudo restricts what commands can be run, I said that Password authentication for access to sudo restricts who can run the sudo command when logged in as each user.
– modernNeo
Dec 25 '18 at 20:20
and I want to give my users the ability to run any command they want via sudo, I just want to also make sure that there is a reliable way to authenticate them when they run sudo.
– modernNeo
Dec 25 '18 at 21:20
@modernNeo Password authentication would not prevent a user from running sudo su - youruser.
– user2233709
Dec 25 '18 at 21:40
@user2233709 I am not trying to prevent them from running sudo as themselves but rather running sudo as another user.
– modernNeo
Dec 25 '18 at 22:09
@user2233709 To put it another way, I want to know the best way to prevent someone from being able to run "sudo <command>" after switching to another user when sudo isnt using password authentication.
– modernNeo
Dec 25 '18 at 22:10
|
show 5 more comments
Password authentication for access to sudo doesn't restrict what commands can be run.
eg
myuser ALL=(ALL) NOPASSWD: ALL
youruser ALL=(ALL) ALL
lets both users run exactly the same commands, just you need to enter your password, and I don't.
Instead the idea is to only grant users the privileged commands they need, rather than "ALL" commands. So if user1 only needs to reboot the server you might give them
user1 ALL=(root) NOPASSWD: /usr/sbin/reboot
Now all they can do is reboot the server.
This follows the principle of least privilege; only give people the commands they need.
Further reading: https://www.sweharris.org/post/2018-08-26-minimal-sudo/
answered Dec 25 '18 at 15:14
Stephen Harris
25.2k24477
Password authentication for access to sudo doesn't restrict what commands can be run.
eg
myuser ALL=(ALL) NOPASSWD: ALL
youruser ALL=(ALL) ALL
lets both users run exactly the same commands, just you need to enter your password, and I don't.
Instead the idea is to only grant users the privileged commands they need, rather than "ALL" commands. So if user1 only needs to reboot the server you might give them
user1 ALL=(root) NOPASSWD: /usr/sbin/reboot
Now all they can do is reboot the server.
This follows the principle of least privilege; only give people the commands they need.
Further reading: https://www.sweharris.org/post/2018-08-26-minimal-sudo/
answered Dec 25 '18 at 15:14
Stephen Harris
25.2k24477
answered Dec 25 '18 at 15:14
Stephen Harris
25.2k24477
answered Dec 25 '18 at 15:14
Stephen Harris
25.2k24477
answered Dec 25 '18 at 15:14
Stephen Harris
25.2k24477
25.2k24477
1
I never said that Password authentication for access to sudo restricts what commands can be run, I said that Password authentication for access to sudo restricts who can run the sudo command when logged in as each user.
– modernNeo
Dec 25 '18 at 20:20
and I want to give my users the ability to run any command they want via sudo, I just want to also make sure that there is a reliable way to authenticate them when they run sudo.
– modernNeo
Dec 25 '18 at 21:20
@modernNeo Password authentication would not prevent a user from running sudo su - youruser.
– user2233709
Dec 25 '18 at 21:40
@user2233709 I am not trying to prevent them from running sudo as themselves but rather running sudo as another user.
– modernNeo
Dec 25 '18 at 22:09
@user2233709 To put it another way, I want to know the best way to prevent someone from being able to run "sudo <command>" after switching to another user when sudo isnt using password authentication.
– modernNeo
Dec 25 '18 at 22:10
|
show 5 more comments
1
I never said that Password authentication for access to sudo restricts what commands can be run, I said that Password authentication for access to sudo restricts who can run the sudo command when logged in as each user.
– modernNeo
Dec 25 '18 at 20:20
and I want to give my users the ability to run any command they want via sudo, I just want to also make sure that there is a reliable way to authenticate them when they run sudo.
– modernNeo
Dec 25 '18 at 21:20
@modernNeo Password authentication would not prevent a user from running sudo su - youruser.
– user2233709
Dec 25 '18 at 21:40
@user2233709 I am not trying to prevent them from running sudo as themselves but rather running sudo as another user.
– modernNeo
Dec 25 '18 at 22:09
@user2233709 To put it another way, I want to know the best way to prevent someone from being able to run "sudo <command>" after switching to another user when sudo isnt using password authentication.
– modernNeo
Dec 25 '18 at 22:10
1
1
I never said that Password authentication for access to sudo restricts what commands can be run, I said that Password authentication for access to sudo restricts who can run the sudo command when logged in as each user.
– modernNeo
Dec 25 '18 at 20:20
I never said that Password authentication for access to sudo restricts what commands can be run, I said that Password authentication for access to sudo restricts who can run the sudo command when logged in as each user.
– modernNeo
Dec 25 '18 at 20:20
and I want to give my users the ability to run any command they want via sudo, I just want to also make sure that there is a reliable way to authenticate them when they run sudo.
– modernNeo
Dec 25 '18 at 21:20
and I want to give my users the ability to run any command they want via sudo, I just want to also make sure that there is a reliable way to authenticate them when they run sudo.
– modernNeo
Dec 25 '18 at 21:20
@modernNeo Password authentication would not prevent a user from running sudo su - youruser.
– user2233709
Dec 25 '18 at 21:40
@modernNeo Password authentication would not prevent a user from running sudo su - youruser.
– user2233709
Dec 25 '18 at 21:40
@user2233709 I am not trying to prevent them from running sudo as themselves but rather running sudo as another user.
– modernNeo
Dec 25 '18 at 22:09
@user2233709 I am not trying to prevent them from running sudo as themselves but rather running sudo as another user.
– modernNeo
Dec 25 '18 at 22:09
@user2233709 To put it another way, I want to know the best way to prevent someone from being able to run "sudo <command>" after switching to another user when sudo isnt using password authentication.
– modernNeo
Dec 25 '18 at 22:10
@user2233709 To put it another way, I want to know the best way to prevent someone from being able to run "sudo <command>" after switching to another user when sudo isnt using password authentication.
– modernNeo
Dec 25 '18 at 22:10
|
show 5 more comments
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