[dak.git] / tools / debianqueued-0.9 / README

           debianqueued -- daemon for managing Debian upload queues
           ========================================================

Copyright (C) 1997 Roman Hodek <Roman.Hodek@informatik.uni-erlangen.de>
$Id: README,v 1.20 1999/07/08 09:35:37 ftplinux Exp $


Copyright and Disclaimer
------------------------

This program is free software.  You can redistribute it and/or
modify it under the terms of the GNU General Public License as
published by the Free Software Foundation: either version 2 or
(at your option) any later version.

This program comes with ABSOLUTELY NO WARRANTY!

You're free to modify this program at your will, according to the GPL,
and I don't object if you modify the program. But it would be nice if
you could send me back such changes if they could be of public
interest. I will try to integrate them into the mainstream version
then.


Installation
------------

debianqueued has been written for running a new Debian upload queue at
ftp.uni-erlangen.de, but I tried to keep it as general as possible and
it should be useable for other sites, too. If there should be
non-portabilities, tell me about them and we'll try to get them fixed!

Before installing debianqueued, you should have the following
utilities installed:

 - pgp (needed for checking signatures)

 - ssh & Co. (but not necessarily sshd, only client programs used)

 - md5sum (for checking file integrity)

 - mkfifo (for creating the status FIFO)

 - GNU tar

 - gzip

 - ar (for analyzing .deb files)

The daemon needs a directory of its own where the scripts reside and
where it can put certain files. This directory is called $queued_dir
in the Perl scripts and below. There are no special requirements where
in the filesystem hierarchy this directory should be.

All configurations are done in file 'config' in $queued_dir. For
security reasons, the $queued_dir should not be in a public FTP area,
and should be writeable (as the files in it) only for the user
maintaining the local debianqueued.

The file Queue.README and Queue.message in the distribution archive
are examples for README and .message files to put into the queue
directory. Modify them as you like, or don't install them if you
don't like them...


Running debianqueued
--------------------

debianqueued is intended to run all time, not as a cron job.
Unfortunately, you can't start it at system boot time automatically,
because a human has to type in the pass phrase for the ssh key. So you
have to start the daemon manually.

The daemon can be stopped by simply killing it (with SIGTERM
preferrably). SIGTERM and SIGINT are blocked during some operations,
where it could leave files in a inconsistent state. So it make take
some time until the daemon really dies. If you have the urgent need
that it goes away immediately, use SIGQUIT. Please don't use SIGKILL
except unavoidable, because the daemon can't clean up after this
signal.

For your convenience, the daemon can kill and restart itself. If you
start debianqueued with a "-k" argument, it tries to kill a running
daemon (and it complains if none is running.) If "-r" is on the
command line, it tries to kill a running daemon first if there is one.
(If not, it starts anyway, but prints a little warning.) If a daemon
is running and a new one is started without "-r", you get an error
message about this. This is to protect you from restarting the daemon
without intention.

The other script, dqueued-watcher, is intended as cron job, and it
watches that the daemon is running, in case that it should crash
sometimes. It also takes care of updating the Debian keyring files if
necessary. You should enter it e.g. like

  0,30 *   *   *   *    .../dqueued-watcher

into your crontab. (Assuming you want to run it every 30 minutes,
which seems a good compromise.)

Both scripts (debianqueued and dqueued-watcher) need no special
priviledges and thus can be run as an ordinary user (not root). You
can create an own user for debianqueued (e.g. "dqueue"), but you need
not. The only difference could be which ssh key is used for connects
to the target host. But you can configure the file to take the ssh key
from in the config file.


The Config File
---------------

The config file, $queued_dir/config, is plain Perl code and is
included by debianqueued and dqueued-watcher. You can set the
following variables there:

 - $debug:
   Non-zero values enable debugging output (to log file).

The following are all programs that debianqueued calls. You should
always use absolute pathnames!

 - $pgp, $ssh, $scp, $ssh_agent, $ssh_add, $md5sum, $mail, $mkfifo,
   $tar, $gzip, $ar

   Notes:

    o $mail should support the -s option for supplying a subject.
      Therefore choose mailx if your mail doesn't know -s.

    o $tar should be GNU tar, several GNU features are used (e.g.
      --use-compress-program).

    o $ar must be able to unpack *.deb files and must understand the
      'p' command. Better check this first... If you don't define $ar
      (or define it to be empty), debianqueued won't be able to
      extract a maintainer address from .deb files. (Which isn't that
      disturbing...)

 - @test_binaries:

   All binaries listed in this variable are tested to be present
   before each queue run. If any is not available, the queue run is
   delayed. This test can be useful if those binaries reside on NFS
   filesystems which may be (auto-)mounted only slowly. It is
   specially annoying for users if pgp can't be found and a .changes
   is deleted.

 - $ssh_options:
   Options passed to ssh and scp on every call. General ssh
   configuration should be done here and not in ~/.ssh/config, to
   avoid dependency on the user's settings. A good idea for
   $ssh_options seems to be

     -o'BatchMode yes' -o'FallBackToRsh no' -o'ForwardAgent no'
     -o'ForwardX11 no' -o'PasswordAuthentication no'
     -o'StrictHostKeyChecking yes'

 - $ssh_key_file:
   The file containing the ssh key you want the daemon to use for
   connects to the target host. If you leave this empty, the default
   ~/.ssh/identity is used, which may or may not be what you want.

 - $incoming:
   This names the queue directory itself. Probably it will be inside
   the public FTP area. Don't forget to allow uploads to it in
   ftpaccess if you're using wu-ftpd.

   Maybe you should also allow anonymous users to rename files in that
   directory, to fix upload problems (they can't delete files, so they
   have to move the errorneous file out of the way). But this
   introduces a denial-of-service security hole, that an attacker
   renames files of other people and then a job won't be done. But at
   least the data aren't lost, and the rename command probably was
   logged by ftpd. Nevertheless, there's no urgent need to allow
   renamings, because the queue daemon deletes all bad files
   automatically, so they can be reuploaded under the same name.
   Decide on your own...

 - $keep_files:
   This is a regular expression for files that never should be deleted
   in the queue directory. The status file must be included here,
   other probable candicates are .message and/or README files.

 - $chmod_on_target:
   If this variable is true (i.e., not 0 or ""), all files belonging
   to a job are changed to mode 644 only on the target host. The
   alternative (if the variable is false, i.e. 0) is to change the
   mode already locally, after the sizes and md5 sums have been
   verified. The latter is the default.

   The background for this is the following: The files must be
   word-readable on master for dinstall to work, so they must be at
   least mode 444, but 644 seems more useful. If the upload policy of
   your site says that uploaded files shouldn't be readable for world,
   the queue daemon has to change the permission at some point of
   time. (scp copies a file's permissions just as the contents, so
   after scp, the files on the target have the same mode as in the
   queue directory.) If the files in the queue are mode 644 anyway,
   you don't need to care about this option. The default --to give
   word read permission in the queue already after some checks-- is
   obviously less restrictive, but might be against the policy of your
   site. The alternative keeps the files unreadable in the queue in
   any case, and they'll be readable only on the target host.

 - $statusfile:
   This is the name of the status file or FIFO, through which users
   can ask the daemon what it's currently doing. It should normally be
   in the queue directory. If you change the name, please don't forget
   to check $keep_files. See also the own section on the status file.

   If you leave $statusfile empty, the daemon doesn't create and
   manage a status file at all, if you don't want it. Unfortunately,
   dqueued-watcher's algorithm to determine whether it already has
   reported a missing daemon depends on the status file, so this
   doesn't work anymore in this case. You'll get dead daemon mails on
   every run of dqueued-watcher.

 - $statusdelay:
   If this number is greater than 0, the status file is implemented as
   a regular file, and updated at least every $statusdelay seconds. If
   $statusdelay is 0, the FIFO implementation is used (see status file
   section).

 - $keyring:
   The name of the PGP keyring the daemon uses to check PGP signatures
   of .changes files. This is usually $queued_dir/debian-keyring.pgp.
   It should contain exactly the keys of all Debian developers (i.e.
   those and no other keys).

 - $gpg_keyring:
   The name of the GnuPG keyring. The daemon now alternatively accepts
   GnuPG signatures on .changes and .commands files. The value here is
   usually $queued_dir/debian-keyring.gpg. It should contain only keys
   of Debian developers (but not all developers have a GPG key
   yet...).

 - $keyring_archive:
   Path of the debian-keyring.tar.gz file inside a Debian mirror. The
   file is "/debian/doc/debian-keyring.tar.gz" on ftp.debian.org,
   don't know where you mirror it to... Leave it empty if you don't
   have that file on your local machine. But then you'll have to
   update the keyring manually from time to time.

 - $keyring_archive_name:
   Name of the PGP keyring file in the archive $keyring_archive. Currently
   "debian-keyring*/debian-keyring.pgp".

 - $gpg_keyring_archive_name:
   Name of the GnuPG keyring file in the archive $keyring_archive. Currently
   "debian-keyring*/debian-keyring.gpg".

 - $logfile:
   The file debianqueued writes its logging data to. Usually "log" in
   $queued_dir.

 - $pidfile:
   The file debianqueued writes its pid to. Usually "pid" in
   $queued_dir.

 - $target:
   Name of the target host, i.e. the host where the queue uploads to.
   Usually "master.debian.org". (Ignored with "copy" upload method.)

 - $targetlogin:
   The login on the target to use for uploads. (Ignored with "copy"
   and "ftp" upload methods; "ftp" always does anonymous logins.)

 - $targetdir:
   The directory on the target to where files should be uploaded. On
   master.debian.org this currently is
   "/home/Debian/ftp/private/project/Incoming".

 - $max_upload_retries:
   This is the number how often the daemon tries to upload a job (a
   .changes + the files belonging to it). After that number is
   exhausted, all these files are deleted.

 - $log_age:
   This is how many days are waited before logfiles are rotated. (The
   age of the current log files is derived from the first date found
   in it.)

 - $log_keep:
   How many old log files to keep. The current logfile is what you
   configured as $logfile above, older versions have ".0", ".1.gz",
   ".2.gz", ... appended. I.e., all old versions except the first are
   additionally gzipped. $log_keep is one higher than the max.
   appended number that should exist.

 - $mail_summary:
   If this is set to a true value (not 0 and not ""), dqueued-watcher
   will send a mail with a summary of the daemon's acivities whenever
   logfiles are rotated.

 - $summary_file:
   If that value is a file name (and not an empty string),
   dqueued-watcher will write the same summary of daemon activities as
   above to the named file. This can be in addition to sending a mail.

 - @nonus_packages:
   This is a (Perl) list of names of packages that must be uploaded to
   nonus.debian.org and not to master. Since the queue daemon only can
   deal with one target, it can't do that upload and thus must reject
   the job. Generally you can treat this variable as a list of any
   packages that should be rejected.

All the following timing variables are in seconds:

 - $upload_delay_1:
   The time between the first (failed) upload try and the next one.
   Usually shorter then $upload_delay_2 for quick retry after
   transient errors.

 - $upload_delay_2:
   The time between the following (except the first) upload retries.

 - $queue_delay:
   The time between two queue runs. (May not be obeyed too exactly...
   a few seconds deviation are normal).

 - $stray_remove_timeout:
   If a file not associated with any .changes file is found in the
   queue directory, it is removed after this many seconds.

 - $problem_report_timeout:
   If there are problems with a job that could also be result of a
   not-yet-complete upload (missing or too small files), the daemon
   waits this long before reporting the problem to the uploader. This
   avoids warning mails for slow but ongoing uploads.

 - $no_changes_timeout:

   If files are found in the queue directory that look like a Debian
   upload (*.tar.gz, *.diff.gz, *.deb, or *.dsc files), but aren't
   accompanied by a .changes file, then debianqueued tries to notify
   the uploader after $no_changes_timeout seconds about this. This
   value is somewhat similar to $problem_report_timeout, and the
   values can be equal.

   Since there's no .changes, the daemon can't never be sure who
   really uploaded the files, but it tries to extract the maintainer
   address from all of the files mentioned above. If they're real
   Debian files (except a .orig.tar.gz), this works in most cases.

 - $bad_changes_timeout:
   After this time, a job with persisting problems (missing files,
   wrong size or md5 checksum) is removed.

 - $remote_timeout:
   This is the maximum time a remote command (ssh/scp) may take. It's
   to protect against network unreliabilities and the like. Choose the
   number sufficiently high, so that the timeout doesn't inadventedly
   kill a longish upload. A few hours seems ok.

Contents of $queued_dir
-----------------------

$queued_dir contains usually the following files:

 - config:
   The configuration file, described above.

 - log:
   Log file of debianqueued. All interesting actions and errors are
   logged there, in a format similar to syslog.

 - pid:
   This file contains the pid of debianqueued, to detect double
   daemons and for killing a running daemon.

 - debian-keyring.pgp, debian-keyring.gpg:
   These are the PGP and GnuPG key rings used by debianqueued to
   verify the signatures of .changes files. It should contain the keys
   of all Debian developers and no other keys. The current Debian key
   ring can be obtained from
   ftp.debian.org:/debian/doc/debian-keyring.tar.gz. dqueued-watcher
   supports the facility to update this file automatically if you also
   run a Debian mirror.

 - debianqueued, dqueued-watcher:
   The Perl scripts.

All filenames except "config" can be changed in the config file. The
files are not really required to reside in $queued_dir, but it seems
practical to have them all together...


Details of Queue Processing
---------------------------

The details of how the files in the queue are processed may be a bit
complicated. You can skip this section if you're not interested in
those details and everything is running fine... :-)

The first thing the daemon does on every queue run is determining all
the *.changes files present. All of them are subsequently read and
analyzed. The .changes MUST contain a Maintainer: field, and the
contents of that field should be the mail address of the uploader. The
address is used for sending back acknowledges and error messages.
(dinstall on master uses the same convention.)

Next, the PGP or GnuPG signature of the .changes is checked. The
signature must be valid and must belong to one of the keys in the
Debian keyring (see config variables $keyring and $gpg_keyring). This
ensures that only registered Debian developers can use the upload
queue to transfer files to master.

Then all files mentioned in the Files: field of the .changes are
checked. All of them must be present, and must have correct size and
md5 checksum. If any of this conditions is violated, the upload
doesn't happen and an error message is sent to the uploader. If the
error is a incorrect size/md5sum, the file is also deleted, because it
has to be reuploaded anyway, and it could be the case that the
uploader cannot easily overwrite a file in the queue dir (due to
upload permission restrictions). If the error is a missing file or a
too small file, the error message is hold back for some time
($problems_report_timeout), because they can also be result of an
not-yet-complete upload.

The time baseline for when to send such a problem report is the
maximum modification time of the .changes itself and all files
mentioned in it. When such a report is sent, the setgid bit (show as
'S' in ls -l listing, in group x position) on the .changes is set to
note that fact, and to avoid the report being sent on every following
queue run. If any modification time becomes greater than the time the
setgid bit was set, a new problem report is sent, because obviously
something has changed to the files.

If a job is hanging around for too long with errors
($bad_changes_timeout), the .changes and all its files are deleted.
The base for that timeout is again the maximum modification time as
explained above.

If now the .changes itself and all its files are ok, an upload is
tried. The upload itself is done with scp. In that stage, various
errors from the net and/or ssh can occur. All these simply count as
upload failures, since it's not easy to distinguish transient and
permanent failures :-( If the scp goes ok, the md5sums of the files on
the target are compared with the local ones. This is to ensure that
the transfer didn't corrupt anything. On any error in the upload or in
the md5 check, the files written to the target host are deleted again
(they may be broken), and an error message is sent to the uploader.

The upload is retied $upload_delay_1 seconds later. If it fails again,
the next retries have a (longer) delay $upload_delay_2 between them.
At most $max_upload_retries retries are done. After all these failed,
all the files are deleted, since it seems we can't move them... For
remembering how many tries were alredy done (and when), debianqueued
uses a separate file. Its name is the .changes' filename with
".failures" appended. It contains simply two integers, the retry count
and the last upload time (in Unix time format).

After a successfull upload, the daemon also checks for files that look
like they belonged to the same job, but weren't listed in the
.changes. Due to experience, this happens rather often with
.orig.tar.gz files, which people upload though they're aren't needed
nor mentioned in the .changes. The daemon uses the filename pattern
<pkg-name>_<version>* to find such unneeded files, where the Debian
revision is stripped from <version>. The latter is needed to include
.orig.tar.gz files, which don't have the Debian revision part. But
this also introduces the possibility that files of another upload for
the same package but with another revision are deleted though they
shouldn't. However, this case seems rather unlikely, so I didn't care
about it. If such files are deleted, that fact is mentioned in the
reply mail to the uploader.

If any files are found in the queue dir that don't belong to any
.changes, they are considered "stray". Such files are remove after 
$stray_remove_timeout. This should be around 1 day or so, to avoid
files being removed that belong to a job, but whose .changes is still
to come. The daemon also tries to find out whether such stray files
could be part of an incomplete upload, where the .changes file is
still missing or has been forgotten. Files that match the patterns
*.deb, *.dsc, *.diff.gz, or *.tar.gz are analyzed whether a maintainer
address can be extracted from them. If yes, the maintainer is notified
about the incomplete upload after $no_changes_timeout seconds.
However, the maintainer needs not really be the uploader... It could
be a binary-only upload for another architecture, or a non-maintainer
upload. In these cases, the mail goes to the wrong wrong person :-(
But better than not writing at all, IMHO...


The status file
---------------

debianqueued provides a status file for the user in the queue
directory. By reading this file, the user can get an idea what the
daemon is currently doing.

There are two possible implementations of the status file: as a plain
file, or as a named pipe (FIFO). Both have their advantages and
disadvantages.

If using the FIFO, the data printed (last ping time, next queue run)
are always up to date, because they're interrogated (by a signal) just
at the time the FIFO is opened for reading. Also, the daemon hasn't to
care about the status file if nobody accesses it. The bad things about
the FIFO: It is a potential portability problem, because not all
systems have FIFOs, or they behave different than I expect... But the
more severe problem: wu-ftpd refuses to send the contents of a FIFO on
a FTP GET request :-(( It does an explicit check whether a file to be
retrieved is a regular file. This can be easily patched [1], but not
everybody wants to do that or can do that (but I did it for
ftp.uni-erlangen.de). (BTW, there could still be problems (races) if
more than one process try to read the status file at the same time...)

The alternative is using a plain file, which is updated regularily by
the daemon. This works on every system, but causes more overhead (the
daemon has to wake up each $statusdelay seconds and write a file), and
the time figures in the file can't be exact. $statusdelay should be a
compromise between CPU wastage and desired accuracy of the times found
in the status file. I think 15 or 30 seconds should be ok, but your
milage may vary.

If the status file is a FIFO, the queue daemon forks a second process
for watching the FIFO (so don't wonder if debianqueued shows up twice
in ps output :-), to avoid blocking a reading process too long until
the main daemon has time to watch the pipe. The status daemon requests
data from the main daemon by sending a signal (SIGUSR1). Nevertheless
it can happen that a process that opens the status file (for reading)
is blocked, because the daemon has crashed (or never has been started,
after reboot). To minimize chances for that situation, dqueued-watcher
replaces the FIFO by a plain file (telling that the daemon is down) if
it sees that no queue daemon is running.


  [1]: This is such a patch, for wu-ftpd-2.4.2-BETA-13:

--- wu-ftpd/src/ftpd.c~ Wed Jul  9 13:18:44 1997
+++ wu-ftpd/src/ftpd.c  Wed Jul  9 13:19:15 1997
@@ -1857,7 +1857,9 @@
         return;
     }
     if (cmd == NULL &&
-        (fstat(fileno(fin), &st) < 0 || (st.st_mode & S_IFMT) != S_IFREG)) {
+        (fstat(fileno(fin), &st) < 0 ||
+        ((st.st_mode & S_IFMT) != S_IFREG &&
+         (st.st_mode & S_IFMT) != S_IFIFO))) {
         reply(550, "%s: not a plain file.", name);
         goto done;
     }


Command Files
-------------

The practical experiences with debianqueued showed that users
sometimes make errors with their uploads, resulting in misnamed or
corrupted files... Formerly they didn't have any chance to fix such
errors, because the ftpd usually doesn't allow deleting or renaming
files in the queue directory. (If you would allow this, *anybody* can
remove/rename files, which isn't desirable.) So users had to wait
until the daemon deleted the bad files (usually ~ 24 hours), before
they could start the next try.

To overcome this, I invented the *.command files. The daemon looks for
such files just as it tests for *.changes files on every queue run,
and processes them before the usual jobs. *.commands files must be PGP
or GnuPG signed by a known Debian developer (same test as for
*.changes), so only these people can give the daemon commands. Since
Debian developers can also delete files in master's incoming, the
*.commands feature doesn't give away any security.

The syntax of a *.commands file is much like a *.changes, but it
contains only two (mandatory) fields: Uploader: and Commands.
Uploader: contains the e-mail address of the uploader for reply mails,
and should have same contents as Maintainer: in a .changes. Commands:
is a multi-line field like e.g. Description: or Changes:. Every
continuation line must start with a space. Each line in Commands:
contains a command for the daemon that looks like a shell command (but
it isn't one, the daemon parses and executes it itself and doesn't use
sh or the respective binaries).

Example:
-----BEGIN PGP SIGNED MESSAGE-----

Uploader: Roman Hodek <Roman.Hodek@informatik.uni-erlangen.de>
Commands: 
 rm hello_1.0-1_i386.deb
 mv hello_1.0-1.dsx hello_1.0-1.dsc

-----BEGIN PGP SIGNATURE-----
Version: 2.6.3ia

iQCVAwUBNFiQSXVhJ0HiWnvJAQG58AP+IDJVeSWmDvzMUphScg1EK0mvChgnuD7h
BRiVQubXkB2DphLJW5UUSRnjw1iuFcYwH/lFpNpl7XP95LkLX3iFza9qItw4k2/q
tvylZkmIA9jxCyv/YB6zZCbHmbvUnL473eLRoxlnYZd3JFaCZMJ86B0Ph4GFNPAf
Z4jxNrgh7Bc=
=pH94
-----END PGP SIGNATURE-----

The only commands implemented at this time are 'rm' and 'mv'. No
options are implemented, and filenames may not contain slashes and are
interpreted relative to the queue directory. This ensures that only
files there can be modified. 'mv' always takes two arguments. 'rm' can
take any number of args. It also knows about the following shell
wildcard chars: *, ?, and [...]. {..,..} constructs are *not*
supported. The daemon expands these patterns itself and doesn't use sh
for that (for security reasons).

*.commands files are processed before the usual *.changes jobs, so if
a commands file fixes a job so that it can be processed, that
processing happens in the same queue run and no unnecessary delay is
introduced.

The uploader of a *.commands will receive a reply mail with a comment
(OK or error message) to each of the commands given. The daemon not
only logs the contents of the Uploader: field, but also the owner of
the PGP/GnuPG key that was used to sign the file. In case you want to
find out who issued some commands, the Uploader: field is insecure,
since its contents can't be checked.


Security Considerations
-----------------------

You already know that debianqueued uses ssh & Co. to get access to
master, or in general any target host. You also probably know that you
need to unlock your ssh secret key with a passphrase before it can be
used. For the daemon this creates a problem: It needs the passphrase
to be able to use ssh/scp, but obviously you can't type in the phrase
every time the daemon needs it... It would also be very ugly and
insecure to write the passphase into some config file of the daemon!

The solution is using ssh-agent, which comes with the ssh package.
This agent's purpose is to store passphrases and give it to
ssh/scp/... if they need it. ssh-agent has to ways how it can be
accessed: through a Unix domain socket, or with an inherited file
descriptor (ssh-agent is the father of your login shell then). The
second method is much more secure than the first, because the socket
can be easily exploited by root. On the other hand, an inherited file
descriptor can be access *only* from a child process, so even root has
bad chances to get its hands on it. Unfortunately, the fd method has
been removed in ssh-1.2.17, so I STRONGLY recommend to use ssh-1.2.16.
(You can still have a newer version for normal use, but separate
binaries for debianqueued.) Also, using debianqueued with Unix domain
sockets is basically untested, though I've heard that it doesn't
work...

debianqueued starts the ssh-agent automatically and runs ssh-add. This
will ask you for your passphrase. The phrase is stored in the agent
and available only to child processes of the agent. The agent will
also start up a second instance of the queue daemon that notices that
the agent is already running.

Currently, there's no method to store the passphrase in a file, due to
all the security disadvantages of this. If you don't mind this and
would like to have some opportunity to do it nevertheless, please ask
me. If there's enough demand, I'll do it.


New Upload Methods
------------------

Since release 0.9, debianqueued has two new upload methods as
alternatives to ssh: copy and ftp.

The copy method simply moves the files to another directory on the
same host. This seems a bit silly, but is for a special purpose: The
admins of master intend to run an upload queue there, too, in the
future to avoid non-anonymous FTP connections, which transmit the
password in cleartext. And, additionally to simply moving the files,
the queue daemon also checks the signature and integrity of uploads
and can reject non-US packages.

The ftp method uploads to a standard anon-FTP incoming directory. The
intention here is that you could create second-level queue daemons.
I.e., those daemons would upload into the queue of another daemon
(and, for example, this could be the queue of the daemon on master).

However, the ftp method still has some limitations:

 1) Files in the target dir can't be deleted.
 2) Uploaded files can't be verified as good as with the other methods.
 3) $chmod_on_target often doesn't work.
 4) The check for a writable incoming directory leaves temporary files
    behind.

Ad 1): In anon-FTP incoming directories removing of files usually
isn't allowed (this would widely open doors to denial-of-service
attacks). But debianqueued has to remove files on the target as part
of handling upload errors. So if an transmission error happens during
a job, the bad file can't be deleted. On the next try, the file is
already present on the target and can't be overwritten, so all the
following tries will fail, too, except the upstream queue daemon has
deleted them already. And if the .changes was among the files already
(at least partially) uploaded, the daemon even will think that the
whole job is already present on the target and will delete the job in
its queue.

Ad 2): Uploaded files are usually verified with md5sum if they're
really the same as the originals. But getting the md5sum for a file on
a FTP server usually isn't possible. It's currently handled as
follows: If the server supports a SITE MD5SUM command (non-standard!),
then this is used and you have the same checking quality. Otherwise,
debianqueued falls back to only comparing the file sizes. This is
better than nothing, but doesn't detected changed contents that don't
result in size changes.

Ad 3): Often SITE CHMOD (standard) isn't allowed in incoming
directories. If this is the case, $chmod_on_target must be off,
otherwise all uploads will fail. The mode of uploaded files if forced
anyway by the FTP server in most cases.

Ad 4): As you know, the queue daemon has a special check if the target
directory is writable at all (it isn't during a freeze) to protect
against repeated upload errors. (Jobs would be even deleted otherwise
if the target dir is unaccessible for too long.) This check is
performed by creating a test file and deleting it immediately again.
But since in FTP incoming dirs deletion isn't permitted, the temporary
file ("junk-for-writable-test-DATE") will remain there. As a partial
fix, the daemon deletes such files immediately, it doesn't even wait
for $stray_remove_timeout. So if the upload goes to the queue dir of
an upstream debianqueued, those temporary files won't be there for
long.

These problems of the FTP method might be remove in future, if I have
better ideas how to bypass the limitations of anon-FTP incoming
directories. Hints welcome :-)


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