quota: Add quota_max_mail_size setting

doc/example-config/conf.d/90-quota.conf

@@ -22,6 +22,9 @@ plugin {
   # over quota, if the quota doesn't grow too high. Default is to allow as
   # long as quota will stay under 10% above the limit. Also allowed e.g. 10M.
   #quota_grace = 10%%
+
+  # Quota plugin can also limit the maximum accepted mail size.
+  #quota_max_mail_size = 100M
 }
 
 ##

src/plugins/quota/Makefile.am

@@ -10,6 +10,7 @@ AM_CPPFLAGS = \
 	-I$(top_srcdir)/src/lib-dict \
 	-I$(top_srcdir)/src/lib-index \
 	-I$(top_srcdir)/src/lib-mail \
+	-I$(top_srcdir)/src/lib-settings \
 	-I$(top_srcdir)/src/lib-storage \
 	-I$(top_srcdir)/src/lib-storage/index \
 	-I$(top_srcdir)/src/lib-storage/index/maildir \

src/plugins/quota/quota-private.h

@@ -25,6 +25,7 @@ struct quota_settings {
 	enum quota_alloc_result (*test_alloc)(
 		struct quota_transaction_context *ctx, uoff_t size);
 
+	uoff_t max_mail_size;
 	const char *quota_exceeded_msg;
 	unsigned int debug:1;
 	unsigned int initialized:1;

src/plugins/quota/quota-status.c

@@ -102,6 +102,7 @@ static void client_handle_request(struct quota_client *client)
 			if (value == NULL)
 				value = "OK";
 			break;
+		case QUOTA_ALLOC_RESULT_OVER_MAXSIZE:
 		/* even over maximum quota */
 		case QUOTA_ALLOC_RESULT_OVER_QUOTA_LIMIT:
 			value = mail_user_plugin_getenv(user,

src/plugins/quota/quota-storage.c

@@ -52,6 +52,9 @@ static void quota_set_storage_error(struct quota_transaction_context *qt,
 {
 	const char *errstr = quota_alloc_result_errstr(res, qt);
 	switch (res) {
+	case QUOTA_ALLOC_RESULT_OVER_MAXSIZE:
+		mail_storage_set_error(storage, MAIL_ERROR_LIMIT, errstr);
+		break;
 	case QUOTA_ALLOC_RESULT_OVER_QUOTA_LIMIT:
 	case QUOTA_ALLOC_RESULT_OVER_QUOTA:
 		mail_storage_set_error(storage, MAIL_ERROR_NOQUOTA, errstr);

src/plugins/quota/quota.c

@@ -13,6 +13,7 @@
 #include "mailbox-list-private.h"
 #include "quota-private.h"
 #include "quota-fs.h"
+#include "settings-parser.h"
 
 #include <sys/wait.h>
 
@@ -226,6 +227,9 @@ const char *quota_alloc_result_errstr(enum quota_alloc_result res,
 		return "OK";
 	case QUOTA_ALLOC_RESULT_TEMPFAIL:
 		return "Internal quota calculation error";
+	case QUOTA_ALLOC_RESULT_OVER_MAXSIZE:
+		return "Mail size is larger than the maximum size allowed by "
+		       "server configuration";
 	case QUOTA_ALLOC_RESULT_OVER_QUOTA_LIMIT:
 	case QUOTA_ALLOC_RESULT_OVER_QUOTA:
 		return qt->quota->set->quota_exceeded_msg;
@@ -254,6 +258,18 @@ int quota_user_read_settings(struct mail_user *user,
 		quota_set->quota_exceeded_msg = DEFAULT_QUOTA_EXCEEDED_MSG;
 	quota_set->vsizes = mail_user_plugin_getenv(user, "quota_vsizes") != NULL;
 
+	const char *max_size = mail_user_plugin_getenv(user,
+						       "quota_max_mail_size");
+	if (max_size != NULL) {
+		const char *error = NULL;
+		if (settings_get_size(max_size, &quota_set->max_mail_size,
+					&error) < 0) {
+			*error_r = t_strdup_printf("quota_max_mail_size: %s",
+					error);
+			return -1;
+		}
+	}
+
 	p_array_init(&quota_set->root_sets, pool, 4);
 	if (i_strocpy(root_name, "quota", sizeof(root_name)) < 0)
 		i_unreached();
@@ -272,7 +288,8 @@ int quota_user_read_settings(struct mail_user *user,
 		if (i_snprintf(root_name, sizeof(root_name), "quota%d", i) < 0)
 			i_unreached();
 	}
-	if (array_count(&quota_set->root_sets) == 0) {
+	if (quota_set->max_mail_size == 0 &&
+	    array_count(&quota_set->root_sets) == 0) {
 		pool_unref(&pool);
 		return 0;
 	}
@@ -1211,6 +1228,11 @@ enum quota_alloc_result quota_test_alloc(struct quota_transaction_context *ctx,
 
 	if (quota_transaction_set_limits(ctx) < 0)
 		return QUOTA_ALLOC_RESULT_TEMPFAIL;
+
+	uoff_t max_size = ctx->quota->set->max_mail_size;
+	if (max_size > 0 && size > max_size)
+		return QUOTA_ALLOC_RESULT_OVER_MAXSIZE;
+
 	if (ctx->no_quota_updates)
 		return QUOTA_ALLOC_RESULT_OK;
 	/* this is a virtual function mainly for trash plugin and similar,

src/plugins/quota/quota.h

@@ -33,6 +33,7 @@ enum quota_recalculate {
 enum quota_alloc_result {
 	QUOTA_ALLOC_RESULT_OK,
 	QUOTA_ALLOC_RESULT_TEMPFAIL,
+	QUOTA_ALLOC_RESULT_OVER_MAXSIZE,
 	QUOTA_ALLOC_RESULT_OVER_QUOTA,
 	/* Mail size is larger than even the maximum allowed quota. */
 	QUOTA_ALLOC_RESULT_OVER_QUOTA_LIMIT,