In trying to resolve some issues with using Cygwin + SSH on Windows 8.1, I'd like to know why the
ssh-host-config script creates two new accounts configuring OpenSSH from scratch? (Is this necessary?)
The two accounts are:
sshd, when using default selection + privilege escalation and service installation. I understand the first one is used only for starting the Cygwin SSHd service, but I don't understanding the function of the second one. I searched the Cygwin archives and the only developer explanation was "because it was designed to do so." It's also recommended against using these for actual login.
Here's my installation:
----------------------------------------------------------- ssh-keygen: generating new host keys: RSA1 RSA DSA ECDSA ED25519 *** Info: Creating default /etc/ssh_config file *** Info: Creating default /etc/sshd_config file *** Info: Privilege separation is set to yes by default since OpenSSH 3.3. *** Info: However, this requires a non-privileged account called 'sshd'. *** Info: For more info on privilege separation read /usr/share/doc/openssh/README.privsep. *** Query: Should privilege separation be used? (yes/no) yes *** Info: Note that creating a new user requires that the current account have *** Info: Administrator privileges. Should this script attempt to create a *** Query: new local account 'sshd'? (yes/no) yes *** Info: Updating /etc/sshd_config file *** Query: Do you want to install sshd as a service? *** Query: (Say "no" if it is already installed as a service) (yes/no) yes *** Query: Enter the value of CYGWIN for the daemon:  *** Info: On Windows Server 2003, Windows Vista, and above, the *** Info: SYSTEM account cannot setuid to other users -- a capability *** Info: sshd requires. You need to have or to create a privileged *** Info: account. This script will help you do so. *** Info: You appear to be running Windows XP 64bit, Windows 2003 Server, *** Info: or later. On these systems, it's not possible to use the LocalSystem *** Info: account for services that can change the user id without an *** Info: explicit password (such as passwordless logins [e.g. public key *** Info: authentication] via sshd). *** Info: If you want to enable that functionality, it's required to create *** Info: a new account with special privileges (unless a similar account *** Info: already exists). This account is then used to run these special *** Info: servers. *** Info: Note that creating a new user requires that the current account *** Info: have Administrator privileges itself. *** Info: No privileged account could be found. *** Info: This script plans to use 'cyg_server'. *** Info: 'cyg_server' will only be used by registered services. *** Query: Do you want to use a different name? (yes/no) no *** Query: Create new privileged user account 'cyg_server'? (yes/no) yes *** Info: Please enter a password for new user cyg_server. Please be sure *** Info: that this password matches the password rules given on your system. *** Info: Entering no password will exit the configuration. *** Query: Please enter the password: *** Query: Reenter: *** Info: User 'cyg_server' has been created with password 'XXXXXXXXXX'. *** Info: If you change the password, please remember also to change the *** Info: password for the installed services which use (or will soon use) *** Info: the 'cyg_server' account. *** Info: Also keep in mind that the user 'cyg_server' needs read permissions *** Info: on all users' relevant files for the services running as 'cyg_server'. *** Info: In particular, for the sshd server all users' .ssh/authorized_keys *** Info: files must have appropriate permissions to allow public key *** Info: authentication. (Re-)running ssh-user-config for each user will set *** Info: these permissions correctly. [Similar restrictions apply, for *** Info: instance, for .rhosts files if the rshd server is running, etc]. *** Info: The sshd service has been installed under the 'cyg_server' *** Info: account. To start the service now, call `net start sshd' or *** Info: `cygrunsrv -S sshd'. Otherwise, it will start automatically *** Info: after the next reboot. *** Info: Host configuration finished. Have fun! -----------------------------------------------------------
In addition, 'cyg_server' is a visible account, that can be used to for Windows login, but 'sshd' seem hidden. So I'm left with the conclusion I'll have to add yet another 3rd account to be able to use SSH properly, which seem rather crazy!
EDIT-1: Not only that, the sshd account also has a password expiration date set 40 days from installation and has a password (according to WMIC). (I was never asked to entered a password for this account, during ssh setup.)
wmic useraccount get AccountType,...,Status:
AccountType Disabled Lockout Name PasswordChangeable PasswordExpires PasswordRequired Status 512 FALSE FALSE cyg_server TRUE FALSE TRUE OK 512 TRUE FALSE sshd TRUE TRUE TRUE Degraded
net user sshd:
User name sshd Full Name sshd privsep Comment User's comment Country/region code 000 (System Default) Account active No Account expires Never Password last set 2014-03-01 23:20:19 Password expires 2014-04-12 23:20:19 Password changeable 2014-03-01 23:20:19 Password required Yes User may change password Yes Workstations allowed All Logon script User profile Home directory C:\cygwin64\var\empty Last logon Never Logon hours allowed All Local Group Memberships *Users Global Group memberships *None The command completed successfully.
So this opens two more questions about this:
- What is the password set and why was the user not informed about this?
- Why does this password have an expiration date?
EDIT-2: Not being able to get through to the Cygwin developer list, I had to do further investigation on my own. So far I don't have an answer to question 1, but there are several other issues with the ssh-host-config script used for setup. Bottom line is, that you can always remove both sshd & cyg_server accounts, and setup one proper admin account using their settings as reference.
Question 2: Windows 8.1 has a default password expiration set to 42 days. This has to be either changed or disabled, using normal Windows tools (UI, WMIC, net user, etc)