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An incorrectly-encoded multibyte character near the end of a string could cause various processing loops to run past the string's terminating NUL, with results ranging from no detectable issue to a program crash, depending on what happens to be in the following memory. This isn't an issue in the server, because we take care to verify the encoding of strings before doing any interesting processing on them. However, that lack of care leaked into client-side code which shouldn't assume that anyone has validated the encoding of its input. Although this is certainly a bug worth fixing, the PG security team elected not to regard it as a security issue, primarily because any untrusted text should be sanitized by PQescapeLiteral or the like before being incorporated into a SQL or psql command. (If an app fails to do so, the same technique can be used to cause SQL injection, with probably much more dire consequences than a mere client-program crash.) Those functions were already made proof against this class of problem, cf CVE-2006-2313. To fix, invent PQmblenBounded() which is like PQmblen() except it won't return more than the number of bytes remaining in the string. In HEAD we can make this a new libpq function, as PQmblen() is. It seems imprudent to change libpq's API in stable branches though, so in the back branches define PQmblenBounded as a macro in the files that need it. (Note that just changing PQmblen's behavior would not be a good idea; notably, it would completely break the escaping functions' defense against this exact problem. So we just want a version for those callers that don't have any better way of handling this issue.) Per private report from houjingyi. Back-patch to all supported branches.
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/.