lib-smtp: server: Add workarounds for well-known MAIL and RCPT comman…

…d syntax deviations.

src/lib-smtp/smtp-server-cmd-mail.c

@@ -73,6 +73,7 @@ void smtp_server_cmd_mail(struct smtp_server_cmd_ctx *cmd,
 	const struct smtp_server_callbacks *callbacks = conn->callbacks;
 	struct smtp_server_command *command = cmd->cmd;
 	struct smtp_server_cmd_mail *mail_data;
+	enum smtp_address_parse_flags path_parse_flags;
 	struct smtp_address *path;
 	enum smtp_param_parse_error pperror;
 	const char *error;
@@ -91,9 +92,26 @@ void smtp_server_cmd_mail(struct smtp_server_cmd_ctx *cmd,
 		smtp_server_reply(cmd, 501, "5.5.4", "Invalid parameters");
 		return;
 	}
-	if (smtp_address_parse_path_full(pool_datastack_create(), params + 5,
-					 SMTP_ADDRESS_PARSE_FLAG_ALLOW_EMPTY,
-					 &path, &error, &params) < 0) {
+	if (params[5] != ' ' && params[5] != '\t') {
+		params += 5;
+	} else if ((set->workarounds &
+		    SMTP_SERVER_WORKAROUND_WHITESPACE_BEFORE_PATH) != 0) {
+		params += 5;
+		while (*params == ' ' || *params == '\t')
+			params++;
+	} else {
+		smtp_server_reply(cmd, 501, "5.5.4",
+				  "Invalid FROM: "
+				  "Unexpected whitespace before path");
+		return;
+	}
+	path_parse_flags = SMTP_ADDRESS_PARSE_FLAG_ALLOW_EMPTY;
+	if (*params != '\0' &&
+	    (set->workarounds & SMTP_SERVER_WORKAROUND_MAILBOX_FOR_PATH) != 0)
+		path_parse_flags |= SMTP_ADDRESS_PARSE_FLAG_BRACKETS_OPTIONAL;
+	if (smtp_address_parse_path_full(pool_datastack_create(), params,
+					 path_parse_flags, &path, &error,
+					 &params) < 0) {
 		smtp_server_reply(cmd, 501, "5.5.4", "Invalid FROM: %s", error);
 		return;
 	}

src/lib-smtp/smtp-server-cmd-rcpt.c

@@ -100,6 +100,7 @@ void smtp_server_cmd_rcpt(struct smtp_server_cmd_ctx *cmd,
 	const struct smtp_server_callbacks *callbacks = conn->callbacks;
 	struct smtp_server_command *command = cmd->cmd;
 	struct smtp_server_cmd_rcpt *rcpt_data;
+	enum smtp_address_parse_flags path_parse_flags;
 	struct smtp_address *path;
 	enum smtp_param_parse_error pperror;
 	const char *error;
@@ -120,9 +121,25 @@ void smtp_server_cmd_rcpt(struct smtp_server_cmd_ctx *cmd,
 			501, "5.5.4", "Invalid parameters");
 		return;
 	}
-	if (smtp_address_parse_path_full(pool_datastack_create(), params + 3,
-					 SMTP_ADDRESS_PARSE_FLAG_ALLOW_LOCALPART,
-					 &path, &error, &params) < 0) {
+	if (params[3] != ' ' && params[3] != '\t') {
+		params += 3;
+	} else if ((set->workarounds &
+		    SMTP_SERVER_WORKAROUND_WHITESPACE_BEFORE_PATH) != 0) {
+		params += 3;
+		while (*params == ' ' || *params == '\t')
+			params++;
+	} else {
+		smtp_server_reply(cmd, 501, "5.5.4",
+				  "Invalid TO: "
+				  "Unexpected whitespace before path");
+		return;
+	}
+	path_parse_flags = SMTP_ADDRESS_PARSE_FLAG_ALLOW_LOCALPART;
+	if ((set->workarounds & SMTP_SERVER_WORKAROUND_MAILBOX_FOR_PATH) != 0)
+		path_parse_flags |= SMTP_ADDRESS_PARSE_FLAG_BRACKETS_OPTIONAL;
+	if (smtp_address_parse_path_full(pool_datastack_create(), params,
+					 path_parse_flags, &path, &error,
+					 &params) < 0) {
 		smtp_server_reply(cmd,
 			501, "5.5.4", "Invalid TO: %s", error);
 		return;

src/lib-smtp/smtp-server-connection.c

@@ -794,6 +794,8 @@ smtp_server_connection_alloc(struct smtp_server *server,
 		}
 		if (set->capabilities != 0)
 			conn->set.capabilities = set->capabilities;
+		conn->set.workarounds |= set->workarounds;
+
 		if (set->max_client_idle_time_msecs > 0) {
 			conn->set.max_client_idle_time_msecs =
 				set->max_client_idle_time_msecs;

src/lib-smtp/smtp-server.c

@@ -43,6 +43,7 @@ struct smtp_server *smtp_server_init(const struct smtp_server_settings *set)
 	} else  {
 		server->set.capabilities = set->capabilities;
 	}
+	server->set.workarounds = set->workarounds;
 	server->set.max_client_idle_time_msecs = set->max_client_idle_time_msecs;
 	server->set.max_pipelined_commands = (set->max_pipelined_commands > 0 ?
 		set->max_pipelined_commands : 1);

src/lib-smtp/smtp-server.h

@@ -226,9 +226,15 @@ struct smtp_server_callbacks {
  * Server
  */
 
+enum smtp_server_workarounds {
+	SMTP_SERVER_WORKAROUND_WHITESPACE_BEFORE_PATH   = BIT(0),
+	SMTP_SERVER_WORKAROUND_MAILBOX_FOR_PATH         = BIT(1)
+};
+
 struct smtp_server_settings {
 	enum smtp_protocol protocol;
 	enum smtp_capability capabilities;
+	enum smtp_server_workarounds workarounds;
 
 	const char *hostname;
 	const char *login_greeting;