參考地址：https://github.com/dotnet/corefx/issues/40538
According to https://www.ssllabs.com/ssltest/analyze.html?d=api-fxpractice.oanda.com their key exchanges are preferring DHE-1024 over ECDHE. Using the guidance from NIST SP 800-57, a 1024-bit DHE key has 80 bits of security (or smaller).
Debian Buster has raised the OpenSSL TLS security level to 2 (https://www.debian.org/releases/stable/i386/release-notes/ch-information.en.html#openssl-defaults), which requires DHE at 2048-bit or higher (112 bits of security).
Theoretically, editing /etc/ssl/openssl.cnf and setting CipherString = DEFAULT:@SECLEVEL=1 will change the security level back to 1.
看起來貌似是debian的安全級別提高了，但是我的應用在.net core 2.2是沒有報這個錯誤的。
解決方式是在dockerfile加上命令
RUN sed -i "s|DEFAULT@SECLEVEL=2|DEFAULT@SECLEVEL=1|g" /etc/ssl/openssl.cnf