generateChangeLog - required priveges? (Oracle)

Hi All, a beginner question…
I just configured liquibase and tried to do a generateChangeLog against an existing database schema with a standard (non-privileged) user. This fails as it tries to do a select from the system table or view ALL_USERS which is not generally visible to all in Oracle (I think, anyway in this database not).
I was hoping that for an export just read permission on ALL_TABLES, ALL_VIEWS. ALL_OBJECTS would be enough since they would define the objects in scope for export.
I haven’t found anything general about what privileges liquibase needs to do what. Does it normally expect to run with system or dba privileges?