• PostgreSQL 9.4.6
  • OpenSSL 1.0.2f

If my server or client certificate use SHA256, I get the following error on the client:

psql: SSL error: tlsv1 alert decrypt error

And the following log message on the server:

LOG:  could not accept SSL connection: unknown message digest algorithm

If I generate the client key with SHA1, it works fine:

openssl x509 -req -in user.csr -CA root.crt -CAkey server.key -out user.crt -CAcreateserial -days 365 -sha1

How can I get it to work with SHA256?

  • Do you set pg_hba.conf correctly? If this file is set correctly, i think it is a problem of openssl library, because the log message unknown message digest algorithm is written by ssl lib.
    – shx
    Feb 23, 2016 at 15:56
  • Yes if I use sha1 certs without changing pg_hba.conf it works fine.
    – RazerM
    Feb 23, 2016 at 15:57
  • Here is the source code of postgres. line 390 generates your log message. More precisely, SSLerrmessage (line 958) creates that message by calling the openssl's function ERR_reason_error_string. Therefore postgres only returns the openssl's error message. On the other words, (i think) the problem has occured on the openssl layer.
    – shx
    Feb 23, 2016 at 16:14

1 Answer 1


This can happen if PostgreSQL is compiled against an older version of openssl than the version used to generate the keys.

Recompiling with the correct openssl library fixes the problem.

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