Update: I found an old NpgSQL thread at
https://github.com/npgsql/npgsql/issues/576 that discusses this issue in more detail. This thread suggests adding "
UseSslStream=false" to the connection string. I tested this, and now NpgSQL 4.0.10 works with PostgreSQL 16.4. Unfortunately, I cannot control the connection string Power BI uses to connect to my PostgreSQL database, but I suppose recompiling NpgSQL 4.0.10 with that option disabled by default would work. I've read in a couple places that this issue only occurs when
ssl_ca_file is set, and I can confirm that my PostgreSQL server has this. So configuring
ssl_ca_file may be important for anyone wishing to reproduce the issue.
I don't know enough about TLS handshakes and session tickets to know where the bug truly lies (PostgreSQL/OpenSSL vs .NET's SslStream).
Cameron Vogt | Software Developer
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Automatic Controls Equipment Systems, Inc.
