d1c6a14bac
The logic in PQconnectPoll() did not take care to ensure that all of a PGconn's internal state variables were reset before trying a new connection attempt. If we got far enough in the connection sequence to have changed any of these variables, and then decided to try a new server address or server name, the new connection might be completed with some state that really only applied to the failed connection. While this has assorted bad consequences, the only one that is clearly a security issue is that password_needed didn't get reset, so that if the first server asked for a password and the second didn't, PQconnectionUsedPassword() would return an incorrect result. This could be leveraged by unprivileged users of dblink or postgres_fdw to allow them to use server-side login credentials that they should not be able to use. Other notable problems include the possibility of forcing a v2-protocol connection to a server capable of supporting v3, or overriding "sslmode=prefer" to cause a non-encrypted connection to a server that would have accepted an encrypted one. Those are certainly bugs but it's harder to paint them as security problems in themselves. However, forcing a v2-protocol connection could result in libpq having a wrong idea of the server's standard_conforming_strings setting, which opens the door to SQL-injection attacks. The extent to which that's actually a problem, given the prerequisite that the attacker needs control of the client's connection parameters, is unclear. These problems have existed for a long time, but became more easily exploitable in v10, both because it introduced easy ways to force libpq to abandon a connection attempt at a late stage and then try another one (rather than just giving up), and because it provided an easy way to specify multiple target hosts. Fix by rearranging PQconnectPoll's state machine to provide centralized places to reset state properly when moving to a new target host or when dropping and retrying a connection to the same host. Tom Lane, reviewed by Noah Misch. Our thanks to Andrew Krasichkov for finding and reporting the problem. Security: CVE-2018-10915 |
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README
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/.