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Troubleshoot PostgreSQL TLS

PostgreSQL

Could not accept SSL connection

If you receive either of the following error messages, you are experiencing an issue with mismatched SSL versions.

  1. LOG:  could not accept SSL connection: wrong version number
  2. HINT:  This may indicate that the client does not support any SSL protocol version between TLSv1.1 and TLSv1.1.
  1. LOG:  could not accept SSL connection: unsupported protocol
  2. HINT:  This may indicate that the client does not support any SSL protocol version between TLSv1.2 and TLSv1.3.

In this case, the client is trying to connect to the server using a version of the TLS protocol that is not supported by the server. Check which version PostgreSQL supports and adjust the client-side TLS version.

You can check the TLS version by running the pg_config --configure command.

Kong recommends TLSv1.2 or higher. Lower versions are deprecated and are not considered secure.

Could not load server certificate file

If you are receiving this error message:

  1. FATAL:  could not load server certificate file "server.crt": No such file or directory

The server is unable to find the certificate file. By default, the certificate file should be named server.crt, and it should be placed in the server’s data directory. Other names are allowed, but they should be explicitly specified in the ssl_cert_file.

Could not access private key file

If you are receiving this error message:

  1. FATAL:  could not access private key file "server.key": No such file or directory

The server is unable to find the private key file. By default, the private key file should be named server.key, and it should be placed in the server’s data directory. If you used another naming convention it should be explicitly set using the ssl_key_file parameter in the postgresql.conf file.

Incorrect private key permissions

  1. FATAL:  private key file "/certs/example.com.key" has group or world access
  2. DETAIL:  File must have permissions u=rw (0600) or less if owned by the database user, or permissions u=rw,g=r (0640) or less if owned by root.

If you receive this error, the permissions for the private key are incorrect. Use the information in the error message to apply the correct permissions to your private key.

Failed to verify the SSL certificate

  1. LOG:  could not accept SSL connection: tlsv1 alert unknown ca

The client has failed to verify the PostgreSQL server certificate. To resolve this issue, make sure that the certificate matches the one applied to Kong Gateway.

Certificate verify failed

  1. LOG:  could not accept SSL connection: certificate verify failed

The PostgreSQL server failed to verify the client certificate. You can fix this by verifying that the server provided in the ssl_ca_file parameter in postgres.conf is trusted by the CA.

Certificate authentication failed for user

  1. LOG:  provided user name (kong) and authenticated user name (foo@example.com) do not match
  2. FATAL:  certificate authentication failed for user "kong"

This error message happens when the client certificate doesn’t match the username specified in the database.

Connection requires a valid client certificate

  1. FATAL:  connection requires a valid client certificate

This error occurs when the PostgreSQL server requires a client certificate for authentication, but the client, in this case Kong Gateway, was unable to provide a valid certificate. For this type of error, check if pg_ssl_cert and pg_ssl_cert_key are correctly set in kong.conf.

Troubleshooting TLS on Kong Gateway

Protocol versions are not a match

If you receive either of the following error messages:

  1. Error: [PostgreSQL error] failed to retrieve PostgreSQL server_version_num: tlsv1 alert protocol version
  1. Error: [PostgreSQL error] failed to retrieve PostgreSQL server_version_num: unsupported protocol

The server and client versions are not in sync. Check the version that the PostgreSQL server is using and adjust the Kong Gateway version accordingly.

The server does not support SSL connections

  1. Error: [PostgreSQL error] failed to retrieve PostgreSQL server_version_num: the server does not support SSL connections

This error occurs when SSL is not supported by PostgreSQL. Configure PostgreSQL according to the configuration instructions.

Certificate verify failed

  1. Error: [PostgreSQL error] failed to retrieve PostgreSQL server_version_num: certificate verify failed

This error occurs when Kong Gateway fails to verify the PostgreSQL server certificate. Ensure that the PostgreSQL server has configured a trusted certificate and the corresponding CA chain is correctly set in lua_ssl_trusted_certificate within kong.conf.

Connection requires a valid client certificate

  1. Error: [PostgreSQL error] failed to retrieve PostgreSQL server_version_num: FATAL: connection requires a valid client certificate

Kong Gateway requires a client certificate for authentication, but the client was unable to provide a valid certificate.

This error occurs when the PostgreSQL server requires a client certificate for authentication, but the Kong Gateway is unable to provide a valid certificate. For this type of error, check if pg_ssl_cert and pg_ssl_cert_key are correctly set in kong.conf.

tlsv1 alert unknown ca

  1. Error: [PostgreSQL error] failed to retrieve PostgreSQL server_version_num: tlsv1 alert unknown ca

The PostgreSQL server failed to verify the client certificate. Use a client certificate which is trusted by the CA set in ssl_ca_file within postgres.conf.

Certificate authentication failed for user

  1. Error: [PostgreSQL error] failed to retrieve PostgreSQL server_version_num: FATAL: certificate authentication failed for user "kong"

The common name of the client certificate doesn’t match the username set in the database. Add a username mapping in pg_ident.conf as described in the PostgreSQL configuration instructions.