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Make cancel request keys longer

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Currently, the cancel request key is a 32-bit token, which isn't very
much entropy. If you want to cancel another session's query, you can
brute-force it. In most environments, an unauthorized cancellation of
a query isn't very serious, but it nevertheless would be nice to have
more protection from it. Hence make the key longer, to make it harder
to guess.

The longer cancellation keys are generated when using the new protocol
version 3.2. For connections using version 3.0, short 4-bytes keys are
still used.

The new longer key length is not hardcoded in the protocol anymore,
the client is expected to deal with variable length keys, up to 256
bytes. This flexibility allows e.g. a connection pooler to add more
information to the cancel key, which might be useful for finding the
connection.

Reviewed-by: Jelte Fennema-Nio <postgres@jeltef.nl>
Reviewed-by: Robert Haas <robertmhaas@gmail.com> (earlier versions)
Discussion: https://www.postgresql.org/message-id/508d0505-8b7a-4864-a681-e7e5edfe32aa@iki.fi
This commit is contained in:
Heikki Linnakangas
2025-04-02 16:41:48 +03:00
parent 285613c60a
commit a460251f0a
14 changed files with 252 additions and 84 deletions
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4
src/include/miscadmin.h
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@ -191,8 +191,8 @@ extern PGDLLIMPORT pg_time_t MyStartTime;
extern PGDLLIMPORT TimestampTz MyStartTimestamp;
extern PGDLLIMPORT struct Port *MyProcPort;
extern PGDLLIMPORT struct Latch *MyLatch;
extern PGDLLIMPORT bool MyCancelKeyValid;
extern PGDLLIMPORT int32 MyCancelKey;
extern PGDLLIMPORT char MyCancelKey[];
extern PGDLLIMPORT uint8 MyCancelKeyLength;
extern PGDLLIMPORT int MyPMChildSlot;
extern PGDLLIMPORT char OutputFileName[];