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ProFTPD Developer Guide: Internals: Configuration Contexts

Table of Contents

Configuration Contexts

At present, ProFTPD has seven different configuration sections or contexts:

  • "server config"
  • <Anonymous>
  • <Directory>
  • <Global>
  • <Limit>
  • <VirtualHost>
  • .ftpaccess

These contexts are determined, in configuration handlers, using the CHECK_CONF macro.

The "server config" Context

The "server config" context encompasses everything outside of the other contexts (i.e. every configuration directive that is not explicitly contained within another configuration context), and indicated by the value CONF_ROOT in a configuration directive handler.

The <Anonymous> Context

The <Anonymous> section is used to set up the very common configuration of an anonymous FTP server. It does a chroot(2) to the anonymous FTP directory by default, and turns off the requirement for a valid password, requesting only a valid email address as the password. Other system binaries or files need not be contained within the <Anonymous> directory.

The CONF_ANON value is used to indicate the <Anonymous> context. Since an <Anonymous> section is not considered a separate server, but rather a subset of its containing server, any configuration directives set for that server will be in effect for the <Anonymous> section as well, unless overridden by a directive of the same name within the <Anonymous> context itself.

Context checks via CHECK_CONF in configuration handlers should check for this CONF_ANON value if the configuration directive should be allowed in the <Anonymous> context.

The <Directory> Context

The <Directory> context is for configurations specific to directories (and files), of course. This includes views of the files in those directories, based on the logged-in user's name, or group membership, or on the name of the files (e.g. Unix-style "hidden" files), and on whether the user has permission to see the files. .ftpaccess files occur within this context by definition; <Limit> sections often appear in a <Directory> section as well.

Configuration handlers would check for the CONF_DIR value in order to make sure that the configuration directive in question is occurring in an allowed context.

The <Global> Context

The description in the documentation for the <Global> context is good. Another point to know is that if a directive is set in this context, and then the same directive is used in the "server config" or <VirtualHost> contexts with different parameters, those parameters take precedence over the <Global> parameters. This allows you to configure things for everyone equally, then tweak specific ervers individually, on a per-server basis.

In configuration directive handlers and context checks, this context uses the CONF_GLOBAL value.

The <Limit> Context

The <Limit> context is used to place limits on who and how individual FTP commands, or groups of FTP commands, may be used. The configuration context value for this section is CONF_LIMIT.

The <VirtualHost> Context

The <VirtualHost> section is used for configuring per-server settings; its value is CONF_VIRTUAL.

The .ftpaccess Context

These files are akin to Apache's .htaccess files, which are parsed-on-the-fly configuration files -- with restricted scopes -- that users can place in their own directories. Note that .ftpaccess are similar to Apache's .htaccess files, they are not the same. For example, ProFTPD's .ftpaccess files do not support a "require" directive, nor Apache's AuthRealm directive. That particular area of Apache configuration is targetted for restricting access to anonymous connections; by its nature, ProFTPD handles anonymous connections as special cases of the normal authenticated connections.

Configuration directive handlers that wish to allow their configuration directive to be placed in this context do so via the CONF_DYNDIR value.

Configuration Flags

The config_rec structure defines a flags member that is used for indicating different configuration types. At present, these configuration types include:

  • CF_DEFER
  • CF_DYNAMIC
  • CF_MERGEDOWN
  • CF_MERGEDOWN_MULTI

The CF_MERGEDOWN flag is the most interesting of the flags, and the one the developer is most likely to encounter. It is used within a configuration directive handler like so:

  config_rec *c = NULL;

  c = add_config_param(...);
  c->flags |= CF_MERGEDOWN;

This flag tells the context-processing functions that configuration sub-contexts are to inherit this config_rec setting, unless the sub-context already has a config_rec of the same directive name.

The other two flags, CF_DEFER and CF_DYNAMIC, are set automatically for <Anonymous> and .ftpacces contexts, respectively.

Table of Contents