I have a bunch of pools of windows IIS servers behind haproxy, and from time to time (I can't reproduce it on demand) they can't stablish a secure connection between pools.
For example, I have servers 1 through 4 with APP and servers 5 through 9 with API. APP needs to stablish an encrypted https connections with API and on rare occasions they can't manage to get a connection stablished. I'm doing https termination on haproxy and the backends are setup with https. The IIS servers have https configured properly (with a "good" certificate). I am using haproxy v1.5.19 (Ubuntu 14.04) and IIS 8.5 on Windows 2012R2. Checking with openssl I get this when I ask for a connection: from haproxy:* Cipher : ECDHE-RSA-AES128-SHA* from iis: *Cipher : ECDHE-RSA-AES256-SHA* Can this be a problem? Should I try to have everything match and use the same preferred encryption? The actual app error is: *The request was aborted: Could not create SSL/TLS secure channel. at System.Net.HttpWebRequest.EndGetRequestStream(IAsyncResult asyncResult, TransportContext& context) at System.Net.Http.HttpClientHandler.GetRequestStreamCallback(IAsyncResult ar) * The error I get on the IIS side is per the Event Viewer: *A fatal alert was received from the remote endpoint. The TLS protocol defined fatal alert code is 20.* According to this page (event ID 36887): *https://blogs.msdn.microsoft.com/kaushal/2012/10/05/ssltls-alert-protocol-the-alert-codes/ <https://blogs.msdn.microsoft.com/kaushal/2012/10/05/ssltls-alert-protocol-the-alert-codes/> *it has something to do with "*bad_record_mac. Received a record with an incorrect MAC. This message is always fatal.*" My settings on haproxy related to encryption ( https://ssl-config.mozilla.org/#server=haproxy&server-version=1.5.19&config=old&openssl-version=1.0.1f&hsts=false&ocsp=false ): tune.ssl.default-dh-param 2048 ssl-default-bind-ciphers ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-AES128-SHA:ECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES128-SHA:ECDHE-ECDSA-AES256-SHA384:ECDHE-ECDSA-AES256-SHA:ECDHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA256:DHE-RSA-AES128-SHA:DHE-RSA-AES256-SHA256:DHE-RSA-AES256-SHA:ECDHE-ECDSA-DES-CBC3-SHA:ECDHE-RSA-DES-CBC3-SHA:EDH-RSA-DES-CBC3-SHA:AES128-GCM-SHA256:AES256-GCM-SHA384:AES128-SHA256:AES256-SHA256:AES128-SHA:AES256-SHA:DES-CBC3-SHA:!DSS ssl-default-bind-options no-sslv3 no-tls-tickets ssl-default-server-ciphers ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-AES128-SHA:ECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES128-SHA:ECDHE-ECDSA-AES256-SHA384:ECDHE-ECDSA-AES256-SHA:ECDHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA256:DHE-RSA-AES128-SHA:DHE-RSA-AES256-SHA256:DHE-RSA-AES256-SHA:ECDHE-ECDSA-DES-CBC3-SHA:ECDHE-RSA-DES-CBC3-SHA:EDH-RSA-DES-CBC3-SHA:AES128-GCM-SHA256:AES256-GCM-SHA384:AES128-SHA256:AES256-SHA256:AES128-SHA:AES256-SHA:DES-CBC3-SHA:!DSS ssl-default-server-options no-sslv3 no-tls-tickets
