* fix(postgres): prevent uint32 underflow & OOM in message parsing
* postgres: drop redundant startup guard, use maxStartupMessageSize const
The msgTotalLen < 8 check already guarantees msgLength >= 4, so the extra
msgLength < 4 guard before reading the protocol version was unreachable.
Point the startup size limit at maxStartupMessageSize instead of a literal.
* postgres: trim query terminator safely, cap pre-auth payloads
Use strings.TrimSuffix for the simple-query null terminator so a
non-null-terminated body isn't silently shortened, matching the auth
handlers. Bound password/MD5 reads with a dedicated maxAuthMessageSize
(10 KiB) instead of the 100 MiB maxMessageSize, since these payloads are
read before authentication.
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Co-authored-by: shangshuhan <shangshuhan@cmict.chinamobile.com>
Co-authored-by: Chris Lu <chris.lu@gmail.com>
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