This module is designed to impose quotas, both byte- and file-based, on FTP accounts, based on user, group, class, or for all accounts. It is based on the ideas contained in Eric Estabrook's mod_quota; however, this module has been written from scratch to implement quotas in a very different manner. A more detailed explanation of the usage of this module follows the directive explanations.

The most current version of mod_quotatab's submodules supports storage of quota table information in various formats:

• mod_quotatab_file for file-based quota tables
  
• mod_quotatab_ldap for LDAP-based quota limit tables
  
• mod_quotatab_radius for RADIUS-based quota tables
  
• mod_quotatab_sql for SQL-based quota tables
  

The most current version of mod_quotatab is distributed with the ProFTPD source code.

Author

Please contact TJ Saunders <tj at castaglia.org> with any questions, concerns, or suggestions regarding this module.

Thanks

2002-01-12: Thanks to SupaFly <ntlfy at ntlworld.com> for helping debug an issue with a missing tally table.

2002-03-30: Thanks to Kai Langheim <kl at q-nic.de> for pointing out several small bugs affecting users with no quota entries.

2003-01-24: Thanks to Arne Blankerts <Blankerts at tow.de> for noting small bug with the file upload counter being incorrectly incremented for overwritten files.

Directives

• QuotaDefault
• QuotaDirectoryTally
• QuotaDisplayUnits
• QuotaEngine
• QuotaExcludeFilter
• QuotaLimitTable
• QuotaLock
• QuotaLog
• QuotaOptions
• QuotaShowQuotas
• QuotaTallyTable

SITE Commands

• SITE QUOTA

QuotaDefault

The QuotaDefault directive configures a "default" quota limit, to be used when a limit is not found for the current user (e.g. a limit has not yet been configured for the user via one of the mod_quotatab backends). Since this "default" needs to provide all of the limit information required by mod_quotatab, there are quite a few required parameters:

• quota-type
• per-session
• limit-type
• bytes-avail-in
• bytes-avail-out
• bytes-avail-xfer
• files-avail-in
• files-avail-out
• files-avail-xfer

For example, you might use:

  QuotaDefault user false hard 10485760 0 0 0 0 0

QuotaDirectoryTally

The QuotaDirectoryTally directive configures mod_quotatab to take directory operations (e.g. creating a directory, removing a directory) into account when tallying.

QuotaDisplayUnits

This directive configures how the user's current byte quota values will be reported to them. Note that this directive does not affect how the quota values are stored in the quota table, only their presentation to the user.

"b" causes quotas to be displayed in bytes; "Kb", kilobytes; "Mb", megabytes; and "Gb", gigabytes.

Example:

  # display quota information in megabytes
  QuotaDisplayUnits Mb

QuotaEngine

The QuotaEngine directive enables or disables the module's runtime quota engine. If it is set to off this module does no runtime processing at all. Use this directive to disable the module instead of commenting out all mod_quotatab directives.

QuotaExcludeFilter

The QuotaExcludeFilter directive configures a regular expression filter that is applied to every file handled by mod_quotatab; this includes files that are scanned if:

  QuotaOptions ScanOnLogin

Note that the regular expression is applied to the absolute path of the file being handled. This allows for a regular expression which can exclude particular directories, or just certain filenames.

QuotaLimitTable

This directive configures the information necessary for the module to locate and use the table containing the quota limit, the maximum number of bytes and/or files defined for use by specific users, groups, classes, etc, and is required for mod_quotatab to function. Note that "groups" here refers to the groups of which the user is a member, the same groups as used for filesystem permissions; "classes" refers to connection classes.

Please consult the relevant submodule documentation for details on that module's syntax for this configuration directive.

See also: QuotaTallyTable

QuotaLock

The QuotaLock directive sets the filename for a synchronization lockfile which mod_quotatab needs when communicating with some submodules, such as for SQL-based tables, which have trouble providing the needed synchronization/locking semantics. Use of QuotaLock is recommended, but not required.

If QuotaLock is used, it is strongly advised that the configured lock file not be on an NFS (or any other network) filesystem.

QuotaLog

The QuotaLog directive is used to specify a log file for mod_quotatab reporting, and can be done a per-server basis. The file parameter must be the full path to the file to use for logging. Note that this path must not be to a world-writeable directory and, unless AllowLogSymlinks is explicitly set to on (generally a bad idea), the path must not be a symbolic link.

If file is "none", no logging will be done at all; this setting can be used to override a QuotaLog setting inherited from a <Global> context.

QuotaOptions

The QuotaOptions directive is used to configure various optional behavior of mod_quotatab.

Example:

  QuotaOptions ScanOnLogin

The currently implemented options are:

• ScanOnLogin
  

  If configured, this causes mod_quotatab to recursively scan the user's home directory when the user logs in, and to update the tally entry for that user, if any, with the number of bytes and files found. Note that these scans will cause a longer login time for the user, depending on the size of their home directory.

  Note that this scanning will only happen if the configured limits for the user have either a bytes-in value greater than zero or a files-in value greater than zero. (These are the only two limits related to upload, hence why ScanOnLogin only goes into effect based on them.)

QuotaShowQuotas

The QuotaShowQuotas directive can be used to enable/disable mod_quotatab's response to a SITE QUOTA request. For some sites, revealing the current quota information may be considered an unnecessary, perhaps even detrimental, information leak; other sites may consider this a definite feature.

QuotaTallyTable

This directive configures the information necessary for the module to locate and use the table containing the quota tally, or the current byte/file counts for users, groups, classes, etc, and is required for mod_quotatab to function. Note that "groups" here refers to the groups of which the user is a member, the same groups as used for filesystem permissions; "classes" refers to connection classes.

Please consult the relevant submodule documentation for details on that module's syntax for this configuration directive.

See also: QuotaLimitTable

SITE QUOTA

The SITE QUOTA command will display the quota, both the limit and the current tally, to the client. This SITE command accepts no parameters, and can only be used once the client has successfully logged in.

Example:

ftp> quote SITE QUOTA
200-The current quota for this session are [current/limit]:
 Name: tj
 Quota Type: User
 Per Session: True
 Limit Type: Hard
   Uploaded Kb:         unlimited
   Downloaded Kb:       unlimited
   Transferred Kb:      unlimited
   Uploaded files:      1/1
   Downloaded files:    unlimited
   Transferred files:   unlimited
200 Please contact root@familiar.castaglia.org if these entries are inaccurate
ftp> 

  <Limit SITE_QUOTA>
    AllowUser tj
    DenyAll
  </Limit>

Like many SITE commands, the FTP client will probably not recognize or support SITE QUOTA. Hopefully the client does have the ability to send arbitrary commands to the server, as the common ftp(1) client does via quote.

The email address displayed in the SITE QUOTA output can be configured via the ServerAdmin directive.

Usage

To use mod_quotatab's functionality, you must first define the tables that together contain the quota information.

There are two such quota tables: one table, called the limit table for providing quota information about the absolute byte/file limits for users, groups, and classes, and a separate table, called the tally table for maintaining the current tally, or number of bytes/files used, for those same users, groups, and classes. (Note that "groups" here refers to the groups of which the user is a member, the same groups as used for filesystem permissions; "classes" refers to connection classes.) This separation of information allows for a configuration such as using LDAP to efficiently distribute the limit information, and local SQL databases for efficiently storing the tally. The limit table is considered a read-only table, and is only accessed at the start of session in order to determine what the session limits should be. The tally table is accessed in read-write mode, and is updated after the relevant FTP commands have been processed.

This module was not explicitly designed for easy interaction with other applications, but rather for other criteria:

• Efficient lookups and updates
• No need for ~/.quota files
• No need of requirement for root privileges to access quotas
• Easy support for an abstraction layer for storing quota information in other formats
• Support for a SITE command that allows users to view their current quotas

This module maintains its quotas based solely on FTP commands - it does not enforce quotas based on files that may have been added, deleted, or moved via shell access or any mechanism other than through the proftpd server.

When a client logs in, assuming QuotaEngine is on, mod_quotatab will check the limit table for the record most appropriate for that client. This check first examines the table for records of type user that match the client's login name.

If no such matching records are found, it checks for records of type group that match any of the user's groups (both primary and supplemental). If there are multiple group-type limits available and applicable to the user's groups, which one is used? The mod_quotatab module first checks for a quota limit for the user's primary group. If there is a group limit for the user's primary group, that limit is used. Otherwise, the supplemental groups for the user are checked, in the order returned by the authenticating module (e.g. mod_auth_unix, mod_sql, mod_ldap, etc).

If no such matching group quotas are found, the mod_quotatab will check for records of type class that belong to the class (if enabled) from which the client is connecting. The order of classes matched is the order in which the classes are defined in the proftpd.conf file.

If still no matching records are found, the table will be searched for a record of type all; if absent, the module will assume that no quotas apply to the client.

Note that there is only one type of limit in effect at a given time; mod_quotatab does not combine multiple user/group/class/all limits for the same client. The module was designed such that only one limit (and its corresponding tally) would be enforced/used for a given session. In the case of multiple applicable group or class type quotas, only the matching quota limit and tally will be used and updated. Currently, there is no support for multiple simultaneous (or "layered") limits/tallies.

Once the limits for the current session have been established, mod_quotatab examines the tally table to see what the current numbers in the matching tally record are. Should the client have an applicable limit record but no matching tally record, the module will initialize a new record in the tally table. If the limit record specifies that quotas are per-session, mod_quotatab will ignore any existing tally records, and will not update the tallies.

For the purposes of tracking the number of uploaded bytes/files, the tally will be adjusted accordingly upon use of the following FTP commands: APPE (bytes only), DELE, STOR, and STOU. The number of bytes used for the calculation will be determined from the difference in file size of the file in question.

For the purposes of tracking the number of downloaded bytes/files, the tally will be adjusted accordingly upon use of the following FTP commands: RETR. The number of bytes used for the calculation will be determined from the number of bytes sent to the client.

For the purposes of tracking the number of transferred bytes/files, the tally will be adjusted accordingly upon use of the following FTP commands: APPE (bytes only), DELE, RETR, STOR, and STOU. The number of bytes used for the calculation will be determined from the number of bytes sent to the client. This type of limit allows for byte/file limits to be set that encompass both uploads and downloads.

Note that if all three types of quotas are set (upload, download, and transfer), any quota reached will cause denial of FTP commands. This means that a high upload quota will never be reached if a low transfer quota is in effect. This holds true for bytes and files quota. For example, if a user has a limited number of both bytes and files to be uploaded in their limit record, the first limit reached (bytes or files) is the effective limit. Caveat emptor.

For any quota limit that is set as "unlimited", mod_quotatab will not keep the tally. Many site administrators might want this ability, for accounting purposes. However, that ability is outside of the intended design of this module; other logging modules are much better suited for accounting purposes (e.g. mod_sql's SQLLog directive).

Quota Limit Enforcement
A "hard" limit type means that a user's tally will never be allowed to exceed the limit; any file uploaded that exceeds the user's quota limit will be deleted, and the tally will not be incremented. A "soft" limit type, on the other hand, is a little less strict, for it will allow a user to exceed the quota limit by one file only. For example, assume a user's tally is close their limit. That user uploads a large file, one that pushes the tally up over the quota limit. If their limit type is "hard", the large file will be deleted once uploaded, and a message returned to the client informing them of this. If the user's limit type is "soft", the large file will be allowed, but any other uploads are denied (until the user deletes some files, and brings their tally back down below the quota limit).

Note that the enforcement of "hard" limits, by deleting the uploaded file, can cause unpleasant surprises for users (and site administrators). In order to not lose large or important files because of hard limits, I recommend using the HiddenStores directive with your mod_quotatab configuration. If HiddenStores is enabled, then when the hard upload limit is exceeded, it will be the temporary HiddenStores file, and not the destination/target file, that will be deleted. This way, the quota-exceeding upload will fail, but users should not be surprised with unexpectedly deleted files.

Quota Internals
If any developers wish to make use of mod_quotatab's quota information, or to develop a new submodule, there is developer documentation available here.

Display Variables
The following variables are provided by mod_quotatab, and can be used in any Display file (e.g. DisplayLogin) other than DisplayConnect. The values for the variables are not known when the client connects to the daemon, hence why the variables are not useful in a DisplayConnect file.

  %{mod_quotatab.limit.bytes_in}
  %{mod_quotatab.limit.bytes_out}
  %{mod_quotatab.limit.bytes_xfer}
  %{mod_quotatab.limit.files_in}
  %{mod_quotatab.limit.files_out}
  %{mod_quotatab.limit.files_xfer}
  %{mod_quotatab.tally.bytes_in}
  %{mod_quotatab.tally.bytes_out}
  %{mod_quotatab.tally.bytes_xfer}
  %{mod_quotatab.tally.files_in}
  %{mod_quotatab.tally.files_out}
  %{mod_quotatab.tally.files_xfer}

Installation

  $ ./configure --with-modules=mod_quotatab:...
  $ make
  $ make install

For using file-based quota tables, include the mod_quotatab_file submodule, e.g.:

  --with-modules=mod_quotatab:mod_quotatab_file

  --enable-dso --with-shared=mod_quotatab:mod_quotatab_file

For using LDAP-based quota limit tables, include mod_quotatab_ldap in addition to either mod_quotatab_file or mod_quotatab_sql:

  --with-modules=mod_quotatab:mod_quotatab_file:mod_quotatab_ldap

  --enable-dso --with-shared=mod_quotatab:mod_quotatab_file:mod_quotatab_ldap

For using SQL-based quota tables, include the mod_quotatab_sql submodule, e.g.:

  --with-modules=mod_quotatab:mod_quotatab_sql

  --enable-dso --with-shared=mod_quotatab:mod_quotatab_sql

  --with-modules=mod_quotatab:mod_quotatab_file:mod_quotatab_sql

  --enable-dso --with-shared=mod_quotatab:mod_quotatab_file:mod_quotatab_sql