175 lines
6.1 KiB
TeX
175 lines
6.1 KiB
TeX
\section{FTP server}\label{sec:ftpd}
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\begin{description}
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\item[Used files:] ftpd.scm
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\item[Name of the package:] ftpd
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\end{description}
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\subsection{What users want to know}
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\subsubsection*{Entry points}
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\defun {ftpd} {anonymous-home \ovar{port}} {\noreturn}
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\begin{defundescx}{ftp-inetd} {anonymous-home} {\noreturn}
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\ex{ftpd} starts the server, using \semvar{anonymous-home} as the
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root directory of the server. Usage of relative paths is not
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encouraged. \semvar{port} specifies the port the server is
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listening for connections. It defaults to 21.
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As the procedure does not return, you have to do a \ex{fork} in
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order to have a ``real'' daemon:
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\codex{(fork (lambda () (ftpd "/data/ftp" 8080)))}
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\ex{ftpd-inetd} is the version to be used with a daemon like
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\ex{inetd}. If the server is started this way, it handles the
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connection through the current standard output and input ports.
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\end{defundescx}
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\subsubsection*{Examples}
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To start the server with the current home directory as root directory
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and listening on port 8080, use
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\codex{(ftpd (cwd) 8080)}
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This is how the ftp server at the computing faculty of the university
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of Tuebingen\footnote{\texttt{archive.informatik.uni-tuebingen.de}} is
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started:
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\begin{code}
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#!/bin/sh /scsh-0.6-alpha/bin/scsh <<EOF
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,batch on
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,config ,load modules.scm
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,open ftpd
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,open threads
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(define (archive-ftpd args)
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(with-syslog-destination
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#f
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#f
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(syslog-facility local0)
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#f
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(lambda ()
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(ftpd "/data/archive/"))))
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(dump-scsh-program archive-ftpd "archive-ftpd.image")
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;; (dump-scsh "archive-ftpd.image")
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EOF\end{code}
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Perhaps you have noticed the \ex{with-syslog-destination} command.
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\ex{ftpd} generates syslog-messages that can be controlled via this
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command. The following section gives you an overview of what is logged
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at which level. See \ex{man 3 syslog} or the
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\ex{with-syslog-destination} command in the scsh-manual for further
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details.
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\subsubsection*{Syslog messages}
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\ex{ftpd} outputs a lot of syslog-messages. A syslog-message may look like
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this:
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\codex{Jul 24 18:34:52 axl ftpd: (thread 21) anonymous user login (230)}
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The log gives you following informations (including those delivered by
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the syslog-daemon):
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\begin{enumerate}
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\item The date and time the log was made (here: Jul 24 18:34:52)
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\item The machine the log was made on (here: axl)
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\item The program, that output the log (ftpd)
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\item The thread the message concerns (here thread 21)
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Each connection is linked with a thread, that handles the commands
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of this connection. When the thread is created, there is a entry in
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the log file containing the remote address and the thread number, so
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in future logs the thread number labels the connection. As at any
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given time the thread number is unique, this is a bijection. (Note
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that the thread numbers are not unique over a period of time).
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\item The log message (here: notification about an anonymous user login)
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\item The reply code returned by ftpd, if any (here: 230)
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\end{enumerate}
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\subsubsection*{The Syslog-levels used\footnote{For further details
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on syslog levels see \ex{man 3 syslog}}}
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Following events are logged as
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\begin{description}
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\item{\ex{NOTICE} level:}
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\begin{itemize}
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\item Messages concerning \emph{connections} (establishing connection,
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connection refused, closing connection due to timeout, etc.)
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\item The execution of the \ex{STOR} command. Its success (\ie
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somebody is putting something on your server via ftp, also known as
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\ex{PUT}) is also logged at notice-level. In fact, the log is made
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before the storing is started actually.
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\item Internal errors
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\item Unix errors
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\item Reaching of actually unreachable case branches
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\end{itemize}
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\item{\ex{INFO} level:} Messages concerning all \emph{other commands},
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including the \ex{RETR} command.
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\item{\ex{DEBUG} level:} All other messages, including debug messages.
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If you want to debug ftpd, put all the messages in one single file,
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since the debug-messages may refer to messages of other levels.
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\end{description}
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Success (as long as interesting) and failure of commands are logged at
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info-level, except the success of the STOR-command, that is logged at
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notice-level (as mentioned above).
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\subsubsection*{Supported commands}
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For those of you who are intrested, the table \ref{ftpd-commands}
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shows the list of supported commands by \ex{ftpd} according to
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RFC~959:
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\FIXME{Can there be a pagebreak in a table?}
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\begin{table}
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\label{ftpd-commands}
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\begin{center}
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\begin{tabular}{|lp{10cm}|}
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\hline
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\ex{ABOR} & abort connection \\
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\ex{CDUP} & move to parent directory \\
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\ex{CWD} & move to specified directory (relative paths may be used) \\
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\ex{DELE} & delete file \\
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\ex{LIST} & list files in current directory (long format) \\
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\ex{MDTM} & deliver modification time of a regular file \\
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\ex{MKD} & make directory \\
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\ex{MODE} & change mode (only stream mode (S) is supported) \\
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\ex{NLST} & list files in current directory (short format) \\
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\ex{NOOP} & do nothing \\
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\ex{PASS} & read in passphrase (\ex{ftpd} currently does not support
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non-anonymous logins) \\
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\ex{PASV} & change to passive mode \\
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\ex{PORT} & change connection port \\
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\ex{PWD} & return name of working directory (print working directory) \\
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\ex{QUIT} & quit session \\
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\ex{RETR} & return file (GET) \\
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\ex{RMD} & remove directory \\
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\ex{RNFR} & read in the name of a file to be renamed (use \ex{RNTO} next) \\
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\ex{RNTO} & rename file mentioned before in a \ex{RNFR} command \\
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\ex{SIZE} & return size of a regular file \\
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\ex{STOR} & store file (PUT) \\
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\ex{STRU}& change structure to transfer files
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(only the file structure is supported) \\
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\ex{SYST} & return system type \\
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\ex{TYPE} & change type (supported types: A is ascii mode,
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I or L8 are 8-bit binary mode) \\
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\ex{USER} & login user (only anonymous logins allowed,
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use ``anonymous'' or ``ftp'' as user name) \\
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\hline
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\end{tabular}
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\caption{Supported RFC~959 commands by the server.}
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\end{center}
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\end{table}
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%\subsection{What programmers want to know}
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%Let me know what you want to know. As long as you are waiting for my
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%answer, have a look in the source file (I'm sorry).
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%%% Local Variables:
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%%% mode: latex
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%%% TeX-master: t
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%%% End:
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