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| faq_su 2013-12-20 | faq_su 2024-09-09 (current) | ||
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| Easiest way is to allow direct login with the user account you need, if it is not allowed already. For accounts such as ''root'', the direct login is typically disabled by default for security reasons. So when enabling it, have security in mind. | Easiest way is to allow direct login with the user account you need, if it is not allowed already. For accounts such as ''root'', the direct login is typically disabled by default for security reasons. So when enabling it, have security in mind. | ||
| - | Particularly with SSH, you may want to keep password authentication (the most vulnerable one) disabled and use e.g. [[public_key|public key authentication]] instead. With OpenSSH server, you can do that by setting ''[[http://www.openbsd.org/cgi-bin/man.cgi?query=sshd_config|sshd_config]]'' keyword ''PermitRootLogin'' to ''without-password''·((Even more restrictive option ''forced-commands-only'' may work with SFTP protocol, but it has not been tested.)). | + | Particularly with SSH, you may want to keep password authentication (the most vulnerable one) disabled and use e.g. [[public_key|public key authentication]] instead. With OpenSSH server, you can do that by setting ''[[https://man.openbsd.org/sshd_config|sshd_config]]'' keyword ''PermitRootLogin'' to ''without-password''.((Even more restrictive option ''forced-commands-only'' may work with SFTP protocol, but it has not been tested.)) |
| - | ===== Use sudo on Login ===== | + | ===== [[sudo]] Use sudo on Login ===== |
| - | In some cases (with Unix/Linux server) you may be able to use ''[[http://www.gratisoft.us/sudo/man/sudo.html|sudo]]'' command straight after login to change a user, before file transfer session starts. | + | In some cases (with Unix/Linux server) you may be able to use ''[[&man_ref(8,sudo)|sudo]]'' command straight after login to change a user, before file transfer session starts. |
| [[ftp|FTP]] protocol does not allow this. | [[ftp|FTP]] protocol does not allow this. | ||
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| The [[scp|SFTP]] and [[scp|SCP]] protocols allow for this, but the actual method is platform dependent. | The [[scp|SFTP]] and [[scp|SCP]] protocols allow for this, but the actual method is platform dependent. | ||
| - | With SFTP protocol, you can use //[[ui_login_sftp#protocol_options|SFTP server]]// option on //SFTP page// of Advanced Site Settings dialog to execute SFTP binary under a different user. With OpenSSH server, you can specify: | + | * With SFTP protocol, you can use //[[ui_login_sftp#protocol_options|SFTP server]]// option on //SFTP page// of Advanced Site Settings dialog to execute SFTP binary under a different user. With OpenSSH server, you can specify: \\ <code> |
| + | sudo /bin/sftp-server | ||
| + | </code> Note that SFTP server binary may be located elsewhere((You can see path to SFTP binary in ''Subsystem sftp'' clause in ''/etc/ssh/sshd_config'', unless keyword ''internal-sftp'' is used instead of a path. You may also use ''whereis sftp-server'' command to locate the binary.)) (e.g. in ''/usr/lib/sftp-server'', ''/usr/lib/openssh/sftp-server'' or ''/usr/libexec/openssh/sftp-server''). | ||
| - | sudo /bin/sftp-server | + | * With SCP protocol, you can specify the following command as custom shell on the //[[ui_login_scp#shell|SCP/Shell page]]// of Advanced Site Settings dialog: \\ <code> |
| + | sudo -s | ||
| + | </code> | ||
| - | Note that SFTP server binary may be located elsewhere (e.g. in ''/usr/lib/openssh/sftp-server''). | + | However you will not be able to provide a password for ''su'' (see [[remote_command#limitations|remote command execution limitations]]). So you may be able to do the above only if you are allowed to do ''sudo su'' without being prompted with password. See ''[[&man_ref(8,sudo)|sudo]]'' documentation to learn how to do that. For example you can add following line to ''[[&man_ref(5,sudoers)|sudoers]]'' file (''/etc/sudoers''): |
| - | + | ||
| - | With SCP protocol, you can specify following command as custom shell on the //[[ui_login_scp#shell|SCP/Shell page]]// of Advanced Site Settings dialog: | + | |
| - | + | ||
| - | sudo -s | + | |
| - | + | ||
| - | However typically you will not be able to provide a password for ''su'' (see [[remote_command#limitations|remote command execution limitations]]). So you may be able to do the above only if you are allowed to do ''sudo su'' without being prompted with password. See ''[[http://www.gratisoft.us/sudo/man/sudo.html|sudo]]'' documentation to learn how to do that. For example you can add following line to ''[[http://www.gratisoft.us/sudo/man/sudoers.html|sudoers]]'' file (''/etc/sudoers''): | + | |
| yourusername ALL=NOPASSWD: ALL | yourusername ALL=NOPASSWD: ALL | ||
| - | The above line is very benevolent, it allows user ''yourusername'' connected from anywhere (the first ''ALL'') to run any command (the second ''ALL'') as a ''root'' without being asked for password. So you should restrict it as much as possible. | + | The above line is very permissive, it allows user ''yourusername'' connected from anywhere (the first ''ALL'') to run any command (the second ''ALL'') as a ''root'' without being asked for password. So you should restrict it as much as possible. |
| For example with OpenSSH you may restrict it only to SFTP session by: | For example with OpenSSH you may restrict it only to SFTP session by: | ||
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| yourusername ALL=NOPASSWD: /bin/sftp-server | yourusername ALL=NOPASSWD: /bin/sftp-server | ||
| - | Note that as WinSCP cannot implement terminal emulation, you need to have ''sudoers'' option ''requiretty'' turned off (what is default). | + | Note that as WinSCP cannot implement terminal emulation, you need to have ''sudoers'' option ''requiretty'' turned off (which is default). |