add mailtrain backend and docs

3 files changed, 333 insertions, 1 deletions

diff --git a/README b/README
index 2b720b6..c9c4e06 100644
--- a/README
+++ b/README
@@ -49,6 +49,28 @@ INSTALLATION
       # mail_plugin_dir = /usr/lib/dovecot/modules/imap
     }
 
+BACKENDS
+
+    The plugin supports multiple backends, there are currently two working
+    backends included in the distribution:
+
+    dspam executable backend (dspam specific)
+
+        This backend instantly retrains by calling dspam. There are some
+        problems with this approach including
+         (1) it can take a long time during which the IMAP session is
+             blocked
+         (2) when many users retrain many messages at once server load may
+             spike
+
+    email sender backend (spam filter agnostic)
+
+        This backend sends mail to ham@example.com or spam@example.com
+        (actual addresses are configurable) for retraining. This backend can
+        be very fast to set up if you already have a working setup that uses
+        training addresses as recommended by many spam filter setups.
+
+
 CONFIGURATION
 
     Aside from the build-configuration done in the '.config' file, you have
@@ -72,7 +94,8 @@ CONFIGURATION
         # BACKEND SPECIFIC OPTIONS
         #
 
-        # dspam-exec plugin:
+        #===================
+        # dspam-exec plugin
 
         # dspam binary
         antispam_dspam_binary = /usr/bin/dspam
@@ -82,6 +105,19 @@ CONFIGURATION
         # antispam_dspam_args =
         # antispam_dspam_args = --user;%u  # % expansion done by dovecot
         # antispam_dspam_args = --mode=teft
+
+        #=====================
+        # mail sending plugin
+
+        # temporary directory
+        antispam_mail_tmpdir = /tmp
+
+        # spam/not-spam addresses (default unset which will give errors)
+        # antispam_mail_spam =
+        # antispam_mail_ham =
+
+        # sendmail binary
+        antispam_mail_tmpdir = /usr/sbin/sendmail
     }
 
 AUTHORS
diff --git a/defconfig b/defconfig
index 30dca99..3ce8bdc 100644
--- a/defconfig
+++ b/defconfig
@@ -26,8 +26,10 @@ DOVECOT_VERSION=1.0
 # backend
 #  dspam-exec		- direct dspam training by calling dspam executable
 #  signature-log	- signature logging using dovecot's dict API
+#  mailtrain		- send mail to special addresses for training
 BACKEND=dspam-exec
 #BACKEND=signature-log
+#BACKEND=mailtrain
 
 
 # install directory for 'make install'
diff --git a/mailtrain.c b/mailtrain.c
new file mode 100644
index 0000000..ec8f066
--- /dev/null
+++ b/mailtrain.c
@@ -0,0 +1,294 @@
+/*
+ * mailing backend for dovecot antispam plugin
+ *
+ * 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
+ */
+
+#include <unistd.h>
+#include <stdlib.h>
+#include <sys/wait.h>
+#include <fcntl.h>
+
+#include "lib.h"
+#include "dict.h"
+#include "mail-storage-private.h"
+#include "ostream.h"
+#include "istream.h"
+
+#include "antispam-plugin.h"
+
+static const char *spamaddr = NULL;
+static const char *hamaddr = NULL;
+static const char *sendmail_binary = "/usr/sbin/sendmail";
+static const char *tmpdir = "/tmp";
+
+static int run_sendmail(int mailfd, bool from_spam)
+{
+	const char *dest = from_spam ? hamaddr : spamaddr;
+	pid_t pid;
+	int status;
+
+	if (!dest)
+		return -1;
+
+	pid = fork();
+
+	switch (pid) {
+	case -1:
+		return -1;
+	case 0:
+		dup2(mailfd, 0);
+		close(1);
+		close(2);
+		execl(sendmail_binary, sendmail_binary, dest, NULL);
+		_exit(1);
+	default:
+		if (waitpid(pid, &status, 0) == -1)
+			return -1;
+		if (!WIFEXITED(status))
+			return -1;
+		return WEXITSTATUS(status);
+	}
+}
+
+struct antispam_transaction_context {
+	char *tmpdir;
+	int count;
+	int tmplen;
+};
+
+struct antispam_transaction_context *backend_start(struct mailbox *box)
+{
+	struct antispam_transaction_context *ast;
+	char *tmp;
+
+	ast = i_new(struct antispam_transaction_context, 1);
+
+	ast->count = 0;
+
+	tmp = i_strconcat(tmpdir, "/antispam-mail-XXXXXX", NULL);
+
+	ast->tmpdir = mkdtemp(tmp);
+	if (!ast->tmpdir)
+		i_free(tmp);
+	else
+		ast->tmplen = strlen(ast->tmpdir);
+
+	return ast;
+}
+
+static int process_tmpdir(struct mailbox_transaction_context *ctx,
+			  struct antispam_transaction_context *ast)
+{
+	int cnt = ast->count;
+	int fd;
+	char *buf;
+	bool from_spam;
+
+	t_push();
+
+	buf = t_malloc(20 + ast->tmplen);
+
+	while (cnt > 0) {
+		cnt--;
+		i_snprintf(buf, 20 + ast->tmplen - 1, "%s/%d",
+			   ast->tmpdir, cnt);
+
+		fd = open(buf, O_RDONLY);
+		read(fd, &from_spam, sizeof(bool));
+
+		if (run_sendmail(fd, from_spam)) {
+			mail_storage_set_error(ctx->box->storage,
+					       "failed to send mail");
+			return -1;
+		}
+	}
+
+	t_pop();
+
+	return 0;
+}
+
+static void clear_tmpdir(struct antispam_transaction_context *ast)
+{
+	char *buf;
+
+	t_push();
+
+	buf = t_malloc(20 + ast->tmplen);
+
+	while (ast->count > 0) {
+		ast->count--;
+		i_snprintf(buf, 20 + ast->tmplen - 1, "%s/%d",
+			   ast->tmpdir, ast->count);
+		unlink(buf);
+	}
+	rmdir(ast->tmpdir);
+
+	t_pop();
+}
+
+void backend_rollback(struct antispam_transaction_context *ast)
+{
+	if (ast->tmpdir) {
+		/* clear it! */
+		clear_tmpdir(ast);
+		i_free(ast->tmpdir);
+	}
+
+	i_free(ast);
+}
+
+int backend_commit(struct mailbox_transaction_context *ctx,
+		   struct antispam_transaction_context *ast)
+{
+	int ret;
+
+	if (!ast->tmpdir) {
+		i_free(ast);
+		return 0;
+	}
+
+	ret = process_tmpdir(ctx, ast);
+
+	clear_tmpdir(ast);
+
+	i_free(ast->tmpdir);
+	i_free(ast);
+
+	return ret;
+}
+
+int backend_handle_mail(struct mailbox_transaction_context *t,
+			struct antispam_transaction_context *ast,
+			struct mail *mail, bool from_spam)
+{
+	struct istream *mailstream;
+	struct ostream *outstream;
+	int ret;
+	char *buf, *firstline;
+	int fd;
+
+	if (!ast->tmpdir) {
+		mail_storage_set_error(t->box->storage,
+				       "Failed to initialise temporary dir");
+		return -1;
+	}
+
+	if (!hamaddr || !spamaddr) {
+		mail_storage_set_error(t->box->storage,
+				       "antispam plugin not configured");
+		return -1;
+	}
+
+	mailstream = mail_get_stream(mail, NULL, NULL);
+	if (!mailstream) {
+		mail_storage_set_error(t->box->storage,
+				       "Failed to get mail contents");
+		return -1;
+	}
+
+	t_push();
+
+	buf = t_malloc(20 + ast->tmplen);
+	i_snprintf(buf, 20 + ast->tmplen - 1, "%s/%d", ast->tmpdir, ast->count);
+
+	fd = creat(buf, 0600);
+	if (fd < 0) {
+		mail_storage_set_error(t->box->storage,
+				       "Failed to create temporary file");
+		ret = -1;
+		goto out;
+	}
+
+	ast->count++;
+
+	outstream = o_stream_create_file(fd, t->box->pool, 0, TRUE);
+	if (!outstream) {
+		ret = -1;
+		mail_storage_set_error(t->box->storage,
+				       "Failed to stream temporary file");
+		goto out_close;
+	}
+
+	if (o_stream_send(outstream, &from_spam, sizeof(from_spam))
+			!= sizeof(from_spam)) {
+		ret = -1;
+		mail_storage_set_error(t->box->storage,
+				       "Failed to write marker to temp file");
+		goto failed_to_copy;
+	}
+
+	firstline = i_stream_read_next_line(mailstream);
+
+	if (strncmp(firstline, "From ", 5) != 0)
+		if (o_stream_send_str(outstream, firstline) < 0) {
+			ret = -1;
+			mail_storage_set_error(t->box->storage,
+					       "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,
+				       "Failed to copy to temporary file");
+		goto failed_to_copy;
+	}
+
+	ret = 0;
+
+ failed_to_copy:
+	o_stream_destroy(&outstream);
+ out_close:
+	close(fd);
+ out:
+	t_pop();
+
+	return ret;
+}
+
+void backend_init(pool_t pool)
+{
+	char *tmp;
+
+	tmp = getenv("ANTISPAM_MAIL_SPAM");
+	if (tmp) {
+		spamaddr = tmp;
+		debug("antispam: mail backend spam address %s\n", tmp);
+	}
+
+	tmp = getenv("ANTISPAM_MAIL_NOTSPAM");
+	if (tmp) {
+		hamaddr = tmp;
+		debug("antispam: mail backend not-spam address %s\n", tmp);
+	}
+
+	tmp = getenv("ANTISPAM_MAIL_SENDMAIL");
+	if (tmp) {
+		sendmail_binary = tmp;
+		debug("antispam: mail backend sendmail %s\n", tmp);
+	}
+
+	tmp = getenv("ANTISPAM_MAIL_TMPDIR");
+	if (tmp)
+		tmpdir = tmp;
+	debug("antispam: mail backend tmpdir %s\n", tmpdir);
+}
+
+void backend_exit(void)
+{
+}