lib-sieve: implementation of editheader extension completed

- Updated documentation.
- Made editheader extension disabled by default

INSTALL

@@ -259,6 +259,15 @@ and sieve_after using the sievec tool, as explained in the README file.
 Sieve Interpreter - Extension Configuration
 -------------------------------------------
 
+- Editheader extension:
+
+  The editheader extension [RFC5293] enables sieve scripts to interact with
+  other components that consume or produce header fields by allowing the script
+  to delete and add header fields.
+
+  The editheader extension requires explicit configuration and is not enabled
+  for use by default. Refer to doc/editheader.txt for configuration information.
+
 - Vacation extension:
 
   The Sieve vacation extension [RFC5230] defines a mechanism to generate
@@ -270,8 +279,8 @@ Sieve Interpreter - Extension Configuration
 
 - Include extension:
 
-	The Sieve include extension (draft) permits users to include one Sieve script
-	into another.
+  The Sieve include extension (draft) permits users to include one Sieve script
+  into another.
 
   The include extension is available by default, but it has its own specific
   configuration options. Refer to doc/include.txt for settings specific to the

TODO

 Current activities:
 
-* Finish editheader extension
-	- Document extension configuration
+-
 
 Parallel plugin-based efforts:
 

doc/editheader.txt

+Editheader Extension
+
+Relevant specifications
+=======================
+
+	RFC5293 - doc/rfc/editheader.rfc5293.txt
+
+Description
+===========
+
+The editheader extension [RFC5293] enables sieve scripts to interact with other
+components that consume or produce header fields by allowing the script to
+delete and add header fields.
+
+Configuration
+=============
+
+The editheader is not available by default and needs to be enabled explicitly by
+adding it to the sieve_extensions setting. 
+
+The following settings can be configured for the editheader extension (default
+values are indicated):
+
+sieve_editheader_max_header_size = 2048
+  The maximum size in bytes of a header field value passed to the addheader
+  command. The minumum value for this setting is 1024 bytes. The value is in
+	bytes, unless followed by a k(ilo).
+
+sieve_editheader_protected =
+  A space-separated list of headers that cannot be added to nor removed from the
+	message header. The `Received:' and `Auto-Submitted:' fields are always
+	protected and the `Subject:' header cannot be protected, as required by the
+  RFC specificiation; adding one of these headers to this setting has no effect.
+
+Invalid values for the settings above will make the Sieve interpreter log
+a warning and revert to the default values. 
+
+Example
+=======
+
+plugin {
+  # Use editheader
+  sieve_extensions = +editheader
+
+  # Header fiels must not exceed one 1k
+  sieve_editheader_max_header_size = 1k
+
+  # Protect special header
+  sieve_editheader_protected = X-Verified
+}
+

src/lib-sieve/sieve-extensions.c

@@ -135,7 +135,6 @@ const struct sieve_extension_def *sieve_core_extensions[] = {
 	&copy_extension, &include_extension, &body_extension,
 	&variables_extension, &enotify_extension, &environment_extension,
 	&mailbox_extension, &date_extension, &ihave_extension,
-	&editheader_extension
 };
 
 const unsigned int sieve_core_extensions_count =
@@ -147,8 +146,8 @@ const unsigned int sieve_core_extensions_count =
  */
 
 const struct sieve_extension_def *sieve_extra_extensions[] = {
-	&vacation_seconds_extension,
-	&spamtest_extension, &spamtestplus_extension, &virustest_extension,
+	&vacation_seconds_extension, &spamtest_extension, &spamtestplus_extension,
+	&virustest_extension, &editheader_extension,
 
 	/* vnd.dovecot. */
 	&debug_extension