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The following error is shown intermittently when attempting to connect to DS/OpenDJ via LDAPS:LDAP local: ldap_simple_bind_s Can't contact LDAP server
An error similar to the following is shown in the DS/OpenDJ log when the above error is received:[21/Sep/2014:10:07:52 +0200] CONNECT conn=23 from=184.108.40.206:8080 to=220.127.116.11:1636 protocol=LDAPS [21/Sep/2014:10:07:52 +0200] DISCONNECT conn=2 reason="I/O Error" msg="An IO error occurred while reading a request from the client: javax.net.ssl.SSLHandshakeException: Invalid Padding length: 227"
Upgraded to Java 7.
Configured LDAPS (LDAP/SSL) between the client and the server.
The SSL error is caused by the client failing to encode the SSL handshake protocol properly; the invalid padding length refers to a block size error occurring when specific block based encryption is used.
This issue occurs when using DH (Diffie-Hellman) based cipher suites (such as: TLS_DHE_RSA_WITH_AES_128_CBC_SHA) and is a known issue on Linux® systems using Java 7: SSL intermittent problem when using DH-based ciphers in Java 7 with Linux although it can affect other operating systems.
You can check which cipher suites are being used by performing a simple search for "supportedTLSCiphers supportedTLSProtocols" as described in Administration Guide › To List Protocols and Cipher Suites.
This issue can be resolved by upgrading to Java 8 or by using non-DH cipher suites.
To use non-DH cipher suites:
You can either configure your client to use non-DH cipher suites or configure the LDAPS connection handler in DS/OpenDJ to offer a limited set of cipher suites using the dsconfig set-connection-handler-prop command.
For example, to permit TLS_RSA_WITH_AES_128_CBC_SHA and SSL_RSA_WITH_RC4_128_SHA cipher suites, you would use a command similar to the following:$ ./dsconfig set-connection-handler-prop --hostname ds1.example.com --port 4444 --bindDN "cn=Directory Manager" --bindPassword password --handler-name "LDAPS Connection Handler" --add ssl-cipher-suite:TLS_EMPTY_RENEGOTIATION_INFO_SCSV --add ssl-cipher-suite:TLS_RSA_WITH_AES_128_CBC_SHA --add ssl-cipher-suite:SSL_RSA_WITH_RC4_128_SHA -n -X
The TLS_EMPTY_RENEGOTIATION_INFO_SCSV cipher suite is a special cipher suite used by Java and should always be included.