NAME

sftp-server — SFTP server subsystem

SYNOPSIS

sftp-server

[-ehR] [-d start_directory] [-f log_facility] [-l log_level] [-P blacklisted_requests] [-p whitelisted_requests] [-u umask]

sftp-server

-Q protocol_feature

DESCRIPTION

sftp-server is a program that speaks the server side of SFTP protocol to stdout and expects client requests from stdin. sftp-server is not intended to be called directly, but from sshd(8) using the Subsystem option.

Command-line flags to sftp-server should be specified in the Subsystem declaration. See sshd_config(5) for more information.

Valid options are:

-d start_directory

specifies an alternate starting directory for users. The pathname may contain the following tokens that are expanded at runtime: %% is replaced by a literal '%', %d is replaced by the home directory of the user being authenticated, and %u is replaced by the username of that user. The default is to use the user's home directory. This option is useful in conjunction with the sshd_config(5) ChrootDirectory option.

-e

Causes sftp-server to print logging information to stderr instead of syslog for debugging.

-f log_facility

Specifies the facility code that is used when logging messages from sftp-server. The possible values are: DAEMON, USER, AUTH, LOCAL0, LOCAL1, LOCAL2, LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7. The default is AUTH.

-h

Displays sftp-server usage information.

-l log_level

Specifies which messages will be logged by sftp-server. The possible values are: QUIET, FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3. INFO and VERBOSE log transactions that sftp-server performs on behalf of the client. DEBUG and DEBUG1 are equivalent. DEBUG2 and DEBUG3 each specify higher levels of debugging output. The default is ERROR.

-P blacklisted_requests

Specify a comma-separated list of SFTP protocol requests that are banned by the server. sftp-server will reply to any blacklisted request with a failure. The -Q flag can be used to determine the supported request types. If both a blacklist and a whitelist are specified, then the blacklist is applied before the whitelist.

-p whitelisted_requests

Specify a comma-separated list of SFTP protocol requests that are permitted by the server. All request types that are not on the whitelist will be logged and replied to with a failure message.

Care must be taken when using this feature to ensure that requests made implicitly by SFTP clients are permitted.

-Q protocol_feature

Query protocol features supported by sftp-server. At present the only feature that may be queried is “requests”, which may be used for black or whitelisting (flags -P and -p respectively).

-R

Places this instance of sftp-server into a read-only mode. Attempts to open files for writing, as well as other operations that change the state of the filesystem, will be denied.

-u umask

Sets an explicit umask(2) to be applied to newly-created files and directories, instead of the user's default mask.

On some systems, sftp-server must be able to access /dev/log for logging to work, and use of sftp-server in a chroot configuration therefore requires that syslogd(8) establish a logging socket inside the chroot directory.

SEE ALSO

sftp(1), ssh(1), sshd_config(5), sshd(8)

T. Ylonen and S. Lehtinen, SSH File Transfer Protocol, draft-ietf-secsh-filexfer-02.txt, October 2001, work in progress material.

HISTORY

sftp-server first appeared in OpenBSD 2.8.

AUTHORS

Markus Friedl <markus@openbsd.org>