Feature Suggestion - Including Dropbear and Network by default

[sm-tradeboox]

Hello.

I would like to suggest that you include Dropbear in ZBM builds by default. Dropbear and network could be enabled/configured via the commandline. If the ZBM EFI also includes gdisk (not needed if the disk is already formatted), then installing any new OS via chroot would be a breeze. And pretty much makes all the complicated installation instructions provided by OpenZFS redundant.

[ahesford]

The ZFSBootMenu recovery image includes basic networking, including dhclient. A case could be made for inclusion of an SSH client, but including Dropbear in a release or recovery image is a different matter. To be useful and somewhat secure, an SSH server should have host keys that are machine specific and not widely publicized. A means to authenticate access is also required. We don't intend to ship images with unlocked root accounts, making key-based authentication the only advisable approach; it is obviously not possible to make key-based authentication feasible in publicly distributed images.

For remote access via SSH, a custom ZBM image will always be required.

[sm-tradeboox]

Perhaps directions on how users could add their own keys, etc. or add dropbear/tinyssh to the image? I've managed to set it up but I just get a feeling I'm not doing it correctly.

[ahesford]

https://github.com/zbm-dev/zfsbootmenu/wiki/Remote-Access-to-ZBM

[ahesford]

Cf. https://github.com/zbm-dev/zfsbootmenu/blob/master/contrib/remote-ssh-build.sh

[emad-elsaid]

Sorry for reviving this discussion.

• Thank you for the script it simplified the steps significantly. the documentation page was a bit cryptic for me and this is how I found this page.
• I tried the script and so far I see the SSH server is running on port 222 and accepts public key auth but the public key in /dropbear/authorized_keys is not working.
• When I ssh to the server ssh -vvvv [email protected] -p 222 I'm getting unauthorized response [email protected]: Permission denied (publickey). .
• When I inspected the log I noticed the public key is sent but then I'm getting debug3: receive packet: type 51 which I believe code for unauthorized

Here is the full log

OpenSSH_9.3p1, OpenSSL 3.1.1 30 May 2023
debug1: Reading configuration data /home/<username>/.ssh/config
debug1: Reading configuration data /etc/ssh/ssh_config
debug2: resolve_canonicalize: hostname 192.168.8.2 is address
debug3: expanded UserKnownHostsFile '~/.ssh/known_hosts' -> '/home/<username>/.ssh/known_hosts'
debug3: expanded UserKnownHostsFile '~/.ssh/known_hosts2' -> '/home/<username>/.ssh/known_hosts2'
debug3: ssh_connect_direct: entering
debug1: Connecting to 192.168.8.2 [192.168.8.2] port 222.
debug3: set_sock_tos: set socket 3 IP_TOS 0x48
debug1: Connection established.
debug1: identity file /home/<username>/.ssh/id_rsa type -1
debug1: identity file /home/<username>/.ssh/id_rsa-cert type -1
debug1: identity file /home/<username>/.ssh/id_ecdsa type -1
debug1: identity file /home/<username>/.ssh/id_ecdsa-cert type -1
debug1: identity file /home/<username>/.ssh/id_ecdsa_sk type -1
debug1: identity file /home/<username>/.ssh/id_ecdsa_sk-cert type -1
debug1: identity file /home/<username>/.ssh/id_ed25519 type -1
debug1: identity file /home/<username>/.ssh/id_ed25519-cert type -1
debug1: identity file /home/<username>/.ssh/id_ed25519_sk type -1
debug1: identity file /home/<username>/.ssh/id_ed25519_sk-cert type -1
debug1: identity file /home/<username>/.ssh/id_xmss type -1
debug1: identity file /home/<username>/.ssh/id_xmss-cert type -1
debug1: identity file /home/<username>/.ssh/id_dsa type -1
debug1: identity file /home/<username>/.ssh/id_dsa-cert type -1
debug1: Local version string SSH-2.0-OpenSSH_9.3
debug1: Remote protocol version 2.0, remote software version dropbear_2022.83
debug1: compat_banner: no match: dropbear_2022.83
debug2: fd 3 setting O_NONBLOCK
debug1: Authenticating to 192.168.8.2:222 as 'root'
debug3: put_host_port: [192.168.8.2]:222
debug3: record_hostkey: found key type ECDSA in file /home/<username>/.ssh/known_hosts:157
debug3: load_hostkeys_file: loaded 1 keys from [192.168.8.2]:222
debug1: load_hostkeys: fopen /home/<username>/.ssh/known_hosts2: No such file or directory
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts: No such file or directory
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts2: No such file or directory
debug3: order_hostkeyalgs: prefer hostkeyalgs: [email protected],ecdsa-sha2-nistp256
debug3: send packet: type 20
debug1: SSH2_MSG_KEXINIT sent
debug3: receive packet: type 20
debug1: SSH2_MSG_KEXINIT received
debug2: local client KEXINIT proposal
debug2: KEX algorithms: [email protected],curve25519-sha256,[email protected],ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group14-sha256,ext-info-c
debug2: host key algorithms: [email protected],ecdsa-sha2-nistp256,[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],ssh-ed25519,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,[email protected],[email protected],rsa-sha2-512,rsa-sha2-256
debug2: ciphers ctos: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected]
debug2: ciphers stoc: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected]
debug2: MACs ctos: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: none,[email protected],zlib
debug2: compression stoc: none,[email protected],zlib
debug2: languages ctos:
debug2: languages stoc:
debug2: first_kex_follows 0
debug2: reserved 0
debug2: peer server KEXINIT proposal
debug2: KEX algorithms: curve25519-sha256,[email protected],ecdh-sha2-nistp521,ecdh-sha2-nistp384,ecdh-sha2-nistp256,diffie-hellman-group14-sha256,diffie-hellman-group14-sha1,[email protected]
debug2: host key algorithms: ecdsa-sha2-nistp256,rsa-sha2-256,ssh-rsa
debug2: ciphers ctos: [email protected],aes128-ctr,aes256-ctr
debug2: ciphers stoc: [email protected],aes128-ctr,aes256-ctr
debug2: MACs ctos: hmac-sha1,hmac-sha2-256
debug2: MACs stoc: hmac-sha1,hmac-sha2-256
debug2: compression ctos: [email protected],none
debug2: compression stoc: [email protected],none
debug2: languages ctos:
debug2: languages stoc:
debug2: first_kex_follows 0
debug2: reserved 0
debug1: kex: algorithm: curve25519-sha256
debug1: kex: host key algorithm: ecdsa-sha2-nistp256
debug1: kex: server->client cipher: [email protected] MAC: <implicit> compression: none
debug1: kex: client->server cipher: [email protected] MAC: <implicit> compression: none
debug3: send packet: type 30
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug3: receive packet: type 31
debug1: SSH2_MSG_KEX_ECDH_REPLY received
debug1: Server host key: ecdsa-sha2-nistp256 SHA256:Gc0Cn3foP3sXVy37Y2oyXCV13qpAJq2vZTUPny4AolA
debug3: put_host_port: [192.168.8.2]:222
debug3: put_host_port: [192.168.8.2]:222
debug3: record_hostkey: found key type ECDSA in file /home/<username>/.ssh/known_hosts:157
debug3: load_hostkeys_file: loaded 1 keys from [192.168.8.2]:222
debug1: load_hostkeys: fopen /home/<username>/.ssh/known_hosts2: No such file or directory
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts: No such file or directory
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts2: No such file or directory
debug1: Host '[192.168.8.2]:222' is known and matches the ECDSA host key.
debug1: Found key in /home/<username>/.ssh/known_hosts:157
debug3: send packet: type 21
debug2: ssh_set_newkeys: mode 1
debug1: rekey out after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug3: receive packet: type 21
debug1: SSH2_MSG_NEWKEYS received
debug2: ssh_set_newkeys: mode 0
debug1: rekey in after 134217728 blocks
debug3: ssh_get_authentication_socket_path: path '/run/user/1000/ssh-agent.socket'
debug1: get_agent_identities: bound agent to hostkey
debug1: get_agent_identities: agent returned 1 keys
debug1: Will attempt key: /home/<username>/.ssh/id_rsa RSA SHA256:3duiJcZnryzgTvZ9WxE4ih+BcApvnpOfd5Q2wDssPMc agent
debug1: Will attempt key: /home/<username>/.ssh/id_rsa
debug1: Will attempt key: /home/<username>/.ssh/id_ecdsa
debug1: Will attempt key: /home/<username>/.ssh/id_ecdsa_sk
debug1: Will attempt key: /home/<username>/.ssh/id_ed25519
debug1: Will attempt key: /home/<username>/.ssh/id_ed25519_sk
debug1: Will attempt key: /home/<username>/.ssh/id_xmss
debug1: Will attempt key: /home/<username>/.ssh/id_dsa
debug2: pubkey_prepare: done
debug3: send packet: type 5
debug3: receive packet: type 7
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=<ssh-ed25519,[email protected],ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,[email protected],rsa-sha2-256,ssh-rsa,ssh-dss>
debug3: receive packet: type 6
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug3: send packet: type 50
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey
debug3: start over, passed a different list publickey
debug3: preferred publickey,keyboard-interactive,password
debug3: authmethod_lookup publickey
debug3: remaining preferred: keyboard-interactive,password
debug3: authmethod_is_enabled publickey
debug1: Next authentication method: publickey
debug1: Offering public key: /home/<username>/.ssh/id_rsa RSA SHA256:3duiJcZnryzgTvZ9WxE4ih+BcApvnpOfd5Q2wDssPMc agent
debug3: send packet: type 50
debug2: we sent a publickey packet, wait for reply
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey
debug1: Trying private key: /home/<username>/.ssh/id_rsa
debug3: no such identity: /home/<username>/.ssh/id_rsa: No such file or directory
debug1: Trying private key: /home/<username>/.ssh/id_ecdsa
debug3: no such identity: /home/<username>/.ssh/id_ecdsa: No such file or directory
debug1: Trying private key: /home/<username>/.ssh/id_ecdsa_sk
debug3: no such identity: /home/<username>/.ssh/id_ecdsa_sk: No such file or directory
debug1: Trying private key: /home/<username>/.ssh/id_ed25519
debug3: no such identity: /home/<username>/.ssh/id_ed25519: No such file or directory
debug1: Trying private key: /home/<username>/.ssh/id_ed25519_sk
debug3: no such identity: /home/<username>/.ssh/id_ed25519_sk: No such file or directory
debug1: Trying private key: /home/<username>/.ssh/id_xmss
debug3: no such identity: /home/<username>/.ssh/id_xmss: No such file or directory
debug1: Trying private key: /home/<username>/.ssh/id_dsa
debug3: no such identity: /home/<username>/.ssh/id_dsa: No such file or directory
debug2: we did not send a packet, disable method
debug1: No more authentication methods to try.
[email protected]: Permission denied (publickey).

• authorized_keys file looks like so

ssh-rsa <public-key> root@homeserver

• I'm using the EFI image from a USB stick. not sure if this makes a difference.

any pointers is appreciated. I spent a couple of hours already trying to figure out what's wrong but I'm running out of ideas.

[ahesford]

What are the permissions on /root, /root/.ssh and /root/.ssh/authorized_keys? Is there a possibility that SELinux is involved? https://unix.stackexchange.com/questions/709054/ssh-publickey-authentication-failure-receive-packet-type-51-sshd-is-not-accep

[emad-elsaid]

• I dropped into a recovery shell to inspect the permissions

/root drwxr-xr-x
/root/.ssh drwxr-xr-x
/root/.ssh/authorized_keys -rw-r--r--

• I see /root/.ss/authorized_keys contains my public key as expected
• also permissions for /etc/dropbear files are -rw-------
• I'm not sure if there is any logs inside I can follow that gives me a bit more information
• I was able to kill dropbear process. but running it with dropbear -F doesn't dhow any output and the port is not open. when I try to ssh to it from another machine. maybe I can run dropbear in the foreground and follow the logs?

[emad-elsaid]

I was able to run dropbear with this command

dropbear -F -E -a -s -g -p 222

• when I ssh it shows this error

/root/.ssh/authorized_keys must be owned by user or root, and not writable by group or others

so permissions error. the authorized_keys is owned by user 1000 which is also my user id in the machine that generated the EFI image. I guess then I must add something to the script to chown.

I tried to change the file ownership in the recovery shell and sshing worked

chown root:0 /root/.ssh/authorized_keys

thanks for the help. I'm wondering what can I add to the script to change the owner. maybe after copying the file I should run chown or even chown it manually on my machine?

[emad-elsaid]

Changing the file ownership on my machine and rebuilding the EFI image worked. thanks for the help really appreciate it

[olfway]

I was going to open a ticket with same feature request.

I'm building custom zfsbootmenu image with docker and I have to install busybox, iputils, iproute2, dropbear and dracut-crypt-ssh in builder image (zbm-builder). Sometimes xbps-install fails and given that I know nothing about void and xbps it's difficult to make it work or find a reason

in ideal case – it would be fantastic to have everything needed in pre-built images, so you will only need to enable it via command line

To be useful and somewhat secure, an SSH server should have host keys that are machine specific and not widely publicized.

Well, it actually depends and if I want to deploy a new virtual machine in cloud with zfsbootmenu – I don't think that pre-build ssh server key will make the whole thing insecure. Another option would be to generate a new server ssh key on start and show a fingerprint

A means to authenticate access is also required.

This could be done providing password in command line (insecure in general, but can be enough for some usages) or provide a public ed25519 key in command line (it's only 68 characters, so not a problem)

If it's too much for you to include everything in pre-build zfsbootmenu images, may be at least include all of it in zbm-builder image?

[no-usernames-left]

Under absolutely no circumstances would I want (or accept) a bootloader with network access enabled by default, and I feel as though I am far from the only one who feels this way.

If it's too much for you to include everything in pre-build zfsbootmenu images, may be at least include all of it in zbm-builder image?

That sounds like the right way forward.

[olfway]

Just to note, it must not accept network connections or start ssh server until it's enabled via command line

[ahesford]

We are definitely not going to provide prebuilt ZBM images with dropbear "ready to go", in whatever form that would take.

For the builder images, we already expose a means (via the -p command-line argument) to install optional packages. Any containerized build that enables network access already requires custom setup to put keys and configuration in place. An extra argument (which can be set via zbm-builder.conf for persistence) to install dropbear seems like a negligible imposition on the margin.