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array_get_element and array_get_slice qualify as leakproof, since they will silently return NULL for bogus subscripts. But array_set_element and array_set_slice throw errors for such cases, making them clearly not leakproof. contain_leaked_vars was evidently written with only the former case in mind, as it gave the wrong answer for assignment SubscriptingRefs (nee ArrayRefs). This would be a live security bug, were it not that assignment SubscriptingRefs can only occur in INSERT and UPDATE target lists, while we only care about leakproofness for qual expressions; so the wrong answer can't occur in practice. Still, that's a rather shaky answer for a security-related question; and maybe in future somebody will want to ask about leakproofness of a tlist. So it seems wise to fix and even back-patch this correction. (We would need some change here anyway for the upcoming generic-subscripting patch, since extensions might make different tradeoffs about whether to throw errors. Commit 558d77f20 attempted to lay groundwork for that by asking check_functions_in_node whether a SubscriptingRef contains leaky functions; but that idea fails now that the implementation methods of a SubscriptingRef are not SQL-visible functions that could be marked leakproof or not.) Back-patch to 9.6. While 9.5 has the same issue, the code's a bit different. It seems quite unlikely that we'd introduce any actual bug in the short time 9.5 has left to live, so the work/risk/reward balance isn't attractive for changing 9.5. Discussion: https://postgr.es/m/3143742.1607368115@sss.pgh.pa.us
PostgreSQL Database Management System ===================================== This directory contains the source code distribution of the PostgreSQL database management system. PostgreSQL is an advanced object-relational database management system that supports an extended subset of the SQL standard, including transactions, foreign keys, subqueries, triggers, user-defined types and functions. This distribution also contains C language bindings. PostgreSQL has many language interfaces, many of which are listed here: https://www.postgresql.org/download See the file INSTALL for instructions on how to build and install PostgreSQL. That file also lists supported operating systems and hardware platforms and contains information regarding any other software packages that are required to build or run the PostgreSQL system. Copyright and license information can be found in the file COPYRIGHT. A comprehensive documentation set is included in this distribution; it can be read as described in the installation instructions. The latest version of this software may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.