Be more tolerant when loading persistence files.

src/persist_read.c

@@ -121,6 +121,12 @@ static int persist__client_msg_restore(struct mosquitto_db *db, struct P_client_
 		return MOSQ_ERR_SUCCESS;
 	}
 
+	context = persist__find_or_add_context(db, chunk->client_id, 0);
+	if(!context){
+		log__printf(NULL, MOSQ_LOG_WARNING, "Warning: Persistence file contains client message with no matching client. File may be corrupt.");
+		return 0;
+	}
+
 	cmsg = mosquitto__calloc(1, sizeof(struct mosquitto_client_msg));
 	if(!cmsg){
 		log__printf(NULL, MOSQ_LOG_ERR, "Error: Out of memory.");
@@ -141,13 +147,6 @@ static int persist__client_msg_restore(struct mosquitto_db *db, struct P_client_
 	cmsg->store = load->store;
 	db__msg_store_ref_inc(cmsg->store);
 
-	context = persist__find_or_add_context(db, chunk->client_id, 0);
-	if(!context){
-		mosquitto__free(cmsg);
-		log__printf(NULL, MOSQ_LOG_ERR, "Error restoring persistent database, message store corrupt.");
-		return 1;
-	}
-
 	if(cmsg->direction == mosq_md_out){
 		msg_data = &context->msgs_out;
 	}else{
@@ -186,9 +185,13 @@ static int persist__client_chunk_restore(struct mosquitto_db *db, FILE *db_fptr)
 	}else{
 		rc = persist__chunk_client_read_v234(db_fptr, &chunk, db_version);
 	}
-	if(rc){
+	if(rc > 0){
 		fclose(db_fptr);
 		return rc;
+	}else if(rc < 0){
+		/* Client not loaded, but otherwise not an error */
+		log__printf(NULL, MOSQ_LOG_WARNING, "Warning: Empty client entry found in persistence database, it may be corrupt.");
+		return MOSQ_ERR_SUCCESS;
 	}
 
 	context = persist__find_or_add_context(db, chunk.client_id, chunk.F.last_mid);

src/persist_read_v5.c

@@ -74,8 +74,10 @@ int persist__chunk_client_read_v5(FILE *db_fptr, struct P_client *chunk)
 	chunk->F.id_len = ntohs(chunk->F.id_len);
 
 	rc = persist__read_string_len(db_fptr, &chunk->client_id, chunk->F.id_len);
-	if(rc || !chunk->client_id){
+	if(rc){
 		return 1;
+	}else if(chunk->client_id == NULL){
+		return -1;
 	}else{
 		return MOSQ_ERR_SUCCESS;
 	}

src/persist_write.c

@@ -175,6 +175,12 @@ static int persist__client_save(struct mosquitto_db *db, FILE *db_fptr)
 			chunk.F.id_len = strlen(context->id);
 			chunk.client_id = context->id;
 
+			if(chunk.F.id_len == 0){
+				/* This should never happen, but in case we have a client with
+				 * zero length ID, don't persist them. */
+				continue;
+			}
+
 			rc = persist__chunk_client_write_v5(db_fptr, &chunk);
 			if(rc){
 				return rc;