add non-working SQL logger backend

It doesn't work with sqlite for the following reasons:
 (1) sqlite is buggy and needs sql_connect() before starting a transaction
     although the API states that isn't the case
 (2) sqlite doesn't understand ON DUPLICATE

(1) leads to a segfault when used with dict-proxy. Also see the comment
in the source code for the broken transaction handling in this backend.

3 files changed, 151 insertions, 2 deletions

diff --git a/Makefile b/Makefile
index 2b0a1e0..0720cfa 100644
--- a/Makefile
+++ b/Makefile
@@ -9,6 +9,7 @@ CFLAGS += -I$(DOVECOT)/src/lib/
 CFLAGS += -I$(DOVECOT)/src/lib-storage/
 CFLAGS += -I$(DOVECOT)/src/lib-mail/
 CFLAGS += -I$(DOVECOT)/src/lib-imap/
+CFLAGS += -I$(DOVECOT)/src/lib-dict/
 CFLAGS += -I$(DOVECOT)/src/imap/
 
 # debug rules
@@ -33,6 +34,9 @@ endif
 ifeq ("$(BACKEND)", "dspam-exec")
 objs += signature.o
 endif
+ifeq ("$(BACKEND)", "signature-log")
+objs += signature.o
+endif
 
 # main make rules
 CFLAGS += -fPIC -shared -Wall
diff --git a/defconfig b/defconfig
index b22f5ed..c1d158d 100644
--- a/defconfig
+++ b/defconfig
@@ -24,8 +24,10 @@ DOVECOT_VERSION=1.0
 #DOVECOT_VERSION=1.1	# CURRENTLY BROKEN
 
 # backend
-#  - dspam-exec: direct dspam training by calling dspam executable
-BACKEND=dspam-exec
+#  dspam-exec		- direct dspam training by calling dspam executable
+#  signature-log	- signature logging using dovecot's dict API
+#BACKEND=dspam-exec
+BACKEND=signature-log
 
 
 # install directory for 'make install'
diff --git a/signature-log.c b/signature-log.c
new file mode 100644
index 0000000..bddca5b
--- /dev/null
+++ b/signature-log.c
@@ -0,0 +1,143 @@
+/*
+ * signature logging 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
+ */
+
+/*
+ * A training implementation must still be written, it needs, to be atomic,
+ * use transactions to get a list of all values and delete them at the same
+ * time, or use a temporary table that is copied from the original while the
+ * original is emptied (again, atomically)
+ */
+
+#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 "antispam-plugin.h"
+#include "signature.h"
+
+static const char *dict_uri = NULL;
+static const char *dict_user = NULL;
+
+struct antispam_transaction_context {
+	struct dict *dict;
+	struct dict_transaction_context *dict_ctx;
+};
+
+struct antispam_transaction_context *backend_start(struct mailbox *box)
+{
+	struct antispam_transaction_context *ast;
+
+	ast = i_new(struct antispam_transaction_context, 1);
+
+	ast->dict = dict_init(dict_uri, dict_user);
+
+	/* see comment below */
+//	if (ast->dict)
+//		ast->dict_ctx = dict_transaction_begin(ast->dict);
+	return ast;
+}
+
+void backend_rollback(struct antispam_transaction_context *ast)
+{
+	if (ast->dict) {
+//		dict_transaction_rollback(ast->dict_ctx);
+		dict_deinit(&ast->dict);
+	}
+
+	i_free(ast);
+}
+
+int backend_commit(struct mailbox_transaction_context *ctx,
+		   struct antispam_transaction_context *ast)
+{
+	int ret = 0;
+
+	if (ast->dict) {
+		ret = 0;
+//		ret = dict_transaction_commit(ast->dict_ctx);
+		dict_deinit(&ast->dict);
+	}
+	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)
+{
+	const char *signature;
+	int ret;
+
+	if (!ast->dict) {
+		mail_storage_set_error(t->box->storage,
+				       "Failed to initialise dict connection");
+		return -1;
+	}
+
+	signature = signature_extract(t, mail);
+
+	/*
+	 * We really should have a global transaction as implemented
+	 * by the code that is commented out with C99 comments (//).
+	 * However, this breaks because
+	 * (1) sqlite cannot nest transactions
+	 * (2) the dict proxy keeps only a single connection open
+	 * (3) we here have a transaction per mailbox which makes two
+	 *     when moving messages (we might be able to hack around
+	 *     this but it's not trivial)
+	 */
+	ast->dict_ctx = dict_transaction_begin(ast->dict);
+	signature = t_strconcat("priv/", signature, NULL);
+	dict_atomic_inc(ast->dict_ctx, signature, from_spam ? -1 : 1);
+	ret = dict_transaction_commit(ast->dict_ctx);
+	if (ret)
+		mail_storage_set_error(t->box->storage,
+				       "Failed to count signature");
+
+	return ret;
+}
+
+void backend_init(pool_t pool)
+{
+	char *tmp;
+
+	tmp = getenv("ANTISPAM_SIGLOG_DICT_URI");
+	if (tmp) {
+		dict_uri = tmp;
+		debug("antispam: signature logger dict URI set to %s\n", tmp);
+	}
+
+	tmp = getenv("ANTISPAM_SIGLOG_DICT_USER");
+	if (tmp) {
+		dict_user = tmp;
+		debug("antispam: signature logger dict user set to %s\n", tmp);
+	}
+
+	signature_init();
+}
+
+void backend_exit(void)
+{
+}