spool2dir backend

3 files changed, 286 insertions, 0 deletions

diff --git a/antispam.7 b/antispam.7
index efec9cd..f19e2c7 100644
--- a/antispam.7
+++ b/antispam.7
@@ -94,6 +94,11 @@ into a spam folder and other mail regularly.
 
 Has the same drawbacks as the dspam-exec approach.
 
+.SS spool2dir backend (general)
+
+This backend spools the message into a file. No further processing
+is performed. You need to write an extra daemon that picks up the
+spooled files and trains the spam filter as appropriate.
 
 .SH CONFIGURATION
 
@@ -194,6 +199,17 @@ plugin {
 
     # NOTE: you need to set the signature for this backend
     antispam_signature = X-CRM114-CacheID
+
+    #===================
+    # spool2dir plugin
+
+	# spam/not-spam spool2dir drop (default unset which will give errors)
+	# The first %%lu is replaced by the current time.
+	# The second %%lu is replaced by a counter to generate unique names.
+	# These two tokens MUST be present in the template! However
+	# you can insert any C-style modifier as shown.
+	# antispam_spool2dir_spam    = /tmp/spamspool/%%020lu-%u-%%05lus
+	# antispam_spool2dir_notspam = /tmp/spamspool/%%020lu-%u-%%05luh
 }
 .fi
 
diff --git a/defconfig b/defconfig
index ef22e81..3bbda18 100644
--- a/defconfig
+++ b/defconfig
@@ -14,10 +14,12 @@
 #  signature-log	- signature logging using dovecot's dict API
 #  mailtrain		- send mail to special addresses for training
 #  crm114-exec		- direct crm114 training by calling mailreaver.crm
+#  spool2dir		- spool trained emails to a directory
 #BACKEND=dspam-exec
 #BACKEND=signature-log
 #BACKEND=mailtrain
 #BACKEND=crm114-exec
+#BACKEND=spool2dir
 
 # Dovecot build/header directory
 # Building the plugin requires configured dovecot sources or having
diff --git a/spool2dir.c b/spool2dir.c
new file mode 100644
index 0000000..06bd307
--- /dev/null
+++ b/spool2dir.c
@@ -0,0 +1,268 @@
+/*
+ * mailing backend for dovecot antispam plugin
+ *
+ * Copyright (C) 2008       Steffen Kaiser <skdovecot@smail.inf.fh-brs.de>
+ * this backend "spool2dir" bases on "mailtrain" backend of
+ * Copyright (C) 2007       Johannes Berg <johannes@sipsolutions.net>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License Version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
+ */
+
+
+/*
+ * spool2dir antispam backend / plugin
+ *
+ * Any modification of SPAM status is recorded into a directory.
+ *
+ * Configuration
+ *
+ * Via settings similiar to the other antispam backends
+ *	antispam_spool2dir_spam :- filename tempate for SPAM messages
+ *	antispam_spool2dir_notsam :- filename tempate for HAM messages
+ *
+ * The templates _must_ provide two arguments:
+ *   1. %%lu - the current unix time (lowercase L, lowercase U)
+ *   2. %%lu - a counter to create different temporary files
+ * Note: The %-sign must be given two times to protect agains
+ *  the expansion by Dovecot itself. You can put any legal
+ *  format modification character of C's printf() function between
+ *  '%%' and 'lu'.
+ *
+ * e.g.:
+ *	antispam_spool2dir_spam = /tmp/spamspool/%%020lu-%%05lu-%u-S
+ *	antispam_spool2dir_ham  = /tmp/spamspool/%%020lu-%%05lu-%u-H
+ *
+ * This example will spool the messages into the directory
+ * /tmp/spamspool. The individual files start with 20 digits,
+ * followe by a dash, 5 digits, the current username and S or H,
+ * indicating Spam or Ham messages.
+ * The first %%lu placeholder is replace by the current unix time,
+ * the second %%lu with the counter. That way, if the same user
+ * trains the same message twice, the filename indicates the order
+ * in which it was done. So if the message was trained as SPAM first,
+ * as HAM later, HAM superceeds SPAM.
+ *
+ * Operation
+ *
+ * When the antispam plugin identifies detects a SPAM status change,
+ * e.g. moving/copying a message from any antispam_spam folder into
+ * a folder _not_ listed in antispam_spam or antispam_trash, this
+ * backend spools the complete message into antispam_mail_basedir.
+ * If there is an error copying _all_ messages around, old spools
+ * are kept, but the current one is deleted. For instance, if the
+ * user is copying 15 messages, but only 10 succeed, the 10 would
+ * be usually deleted. In this backend there is no rollback of
+ * successfully spooled message, only the failed message is
+ * deleted.
+ *
+ * Possible usage models
+ *
+ * A)
+ *   I use spool2dir for training the Bayes database as follows:
+ *
+ *   Every 10 seconds a service invokes the training program, unless
+ *   it already runs.
+ *
+ *   The training progran reads the content of the spool directory, sorts
+ *   the filenames alphanumerically, waits two seconds to allow any current
+ *   spool2dir processes to finish currently open files.
+ *   Then one message at a time is read and identified, if it contains
+ *   local modifications, e.g. user-visible SPAM reports, which are removed.
+ *   Furthermore, reports of untrustworthy people are discarded.
+ *   This process continues until either all messages are processed or
+ *   the next message would have another SPAM report type (HAM or SPAM). The
+ *   file names of the messages processed til now are passed to the Bayes
+ *   trainer to be processed within one run. Then those messages are removed.
+ *
+ * B)
+ *
+ *   An Inotify server watches the spamspool directory and passes the messages
+ *   to spamd. No need for the filenames to indicate the order anymore, unless
+ *   the inotify server is not fast enough.
+ */
+
+#include <unistd.h>
+#include <fcntl.h>
+#include <string.h>
+#include <errno.h>
+
+#include "lib.h"
+#include "mail-storage-private.h"
+#include "ostream.h"
+#include "istream.h"
+
+#include "antispam-plugin.h"
+
+static const char *spamspool = NULL;
+static const char * hamspool = NULL;
+
+struct antispam_transaction_context {
+	int count;
+};
+
+
+void backend_rollback(struct antispam_transaction_context *ast)
+{
+	i_free(ast);
+}
+
+int backend_commit(struct mailbox_transaction_context *ctx __attr_unused__,
+		   struct antispam_transaction_context *ast)
+{
+	i_free(ast);
+
+	return 0;
+}
+
+int backend_handle_mail(struct mailbox_transaction_context *t,
+			struct antispam_transaction_context *ast,
+			struct mail *mail, enum classification wanted)
+{
+	struct istream *mailstream;
+	struct ostream *outstream;
+	int ret;
+	const char *dest, *buf;
+	const unsigned char *beginning;
+	size_t size;
+	int fd;
+
+	i_assert(ast);
+
+	switch (wanted) {
+	case CLASS_SPAM:
+		dest = spamspool;
+		break;
+	case CLASS_NOTSPAM:
+		dest =  hamspool;
+		break;
+	default:	/* cannot handle this */
+		return -1;
+	}
+
+	if(!dest) {
+		mail_storage_set_error(t->box->storage,
+				       ME(NOTPOSSIBLE)
+				       "antispam plugin / spool2dir backend not configured");
+		return -1;
+	}
+
+	mailstream = get_mail_stream(mail);
+	if (!mailstream) {
+		mail_storage_set_error(t->box->storage,
+				       ME(EXPUNGED)
+				       "Failed to get mail contents");
+		return -1;
+	}
+
+	t_push();
+
+	/* atomically create a _new_ file */
+	while (ast->count <= 9999) {
+		buf = t_strdup_printf(dest, (long)time(0), (long)++ast->count);
+		fd = open(buf, O_CREAT | O_EXCL | O_WRONLY, 0600);
+		if(fd >= 0 || errno != EEXIST)
+			break;
+		/* current filename in buf already exists, zap it */
+		t_pop();
+		t_push();
+		/* buf is invalid now ! */
+	}
+	if (fd < 0) {
+		debug("spool2dir backend: Failed to create spool file %s: %s\n",
+		      dest, strerror(errno));
+		mail_storage_set_error(t->box->storage,
+				       ME(NOTPOSSIBLE)
+					   "Failed to create spool file");
+		goto out;
+	}
+
+	/* buf still points to allocated memory, because fd >= 0 */
+	outstream = o_stream_create_from_fd(fd, t->box->pool);
+	if (!outstream) {
+		mail_storage_set_error(t->box->storage,
+				       ME(NOTPOSSIBLE)
+				       "Failed to stream spool file");
+		goto out_close;
+	}
+
+	if (i_stream_read_data(mailstream, &beginning, &size, 5) < 0 ||
+	    size < 5) {
+		ret = -1;
+		mail_storage_set_error(t->box->storage,
+				       ME(NOTPOSSIBLE)
+				       "Failed to read mail beginning");
+		goto failed_to_copy;
+	}
+
+	/* "From "? skip line */
+	if (memcmp("From ", beginning, 5) == 0) {
+		i_stream_read_next_line(mailstream);
+	} else {
+		if (o_stream_send(outstream, beginning, 5) != 5) {
+			ret = -1;
+			mail_storage_set_error(t->box->storage,
+					       ME(NOTPOSSIBLE)
+					       "Failed to write line to temp");
+			goto failed_to_copy;
+		}
+	}
+
+	if (o_stream_send_istream(outstream, mailstream) < 0) {
+		ret = -1;
+		mail_storage_set_error(t->box->storage,
+				       ME(NOTPOSSIBLE)
+				       "Failed to copy to spool file");
+		goto failed_to_copy;
+	}
+
+	ret = 0;
+
+ failed_to_copy:
+	o_stream_destroy(&outstream);
+ out_close:
+	close(fd);
+ out:
+	if (ret)
+		unlink(buf);
+
+	t_pop();
+
+	return ret;
+}
+
+void backend_init(pool_t pool __attr_unused__)
+{
+	if((spamspool = get_setting("SPOOL2DIR_SPAM")))
+		debug("spool2dir spamspool %s\n", spamspool);
+
+	if((hamspool = get_setting("SPOOL2DIR_NOTSPAM")))
+		debug("spool2dir hamspool %s\n", hamspool);
+}
+
+struct antispam_transaction_context *
+ backend_start(struct mailbox *box __attr_unused__)
+{
+	struct antispam_transaction_context *ast;
+
+	ast = i_new(struct antispam_transaction_context, 1);
+
+	ast->count = 0;
+
+	return ast;
+}
+
+
+void backend_exit(void)
+{
+}