558d4ada18
It's not terribly hard to devise regular expressions that take large amounts of time and/or memory to process. Recent testing by Greg Stark has also shown that machines with small stack limits can be driven to stack overflow by suitably crafted regexps. While we intend to fix these things as much as possible, it's probably impossible to eliminate slow-execution cases altogether. In any case we don't want to treat such things as security issues. The history of that code should already discourage prudent DBAs from allowing execution of regexp patterns coming from possibly-hostile sources, but it seems like a good idea to warn about the hazard explicitly. Currently, similar_escape() allows access to enough of the underlying regexp behavior that the warning has to apply to SIMILAR TO as well. We might be able to make it safer if we tightened things up to allow only SQL-mandated capabilities in SIMILAR TO; but that would be a subtly non-backwards-compatible change, so it requires discussion and probably could not be back-patched. Per discussion among pgsql-security list. |
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