SSL peer certificate validation failed:unsupported certificate purpose

[Micheal Shallop]

Trying to set-up SSL/TLS for a replication set.

Carefully generated and signed root, intermediate, and server certs.  All verified.  Server certs verified against the chain cert.  Chain cert verified against the root cert.

Took extra care in setting up the DNs for all the certs at all levels.  All nodes are defined in /etc/hosts and the node names match the CN in the server cert DNs.

Intermediate cert CN does not match the root cert CN.

The repl-set is solid - it connects and repls all day normally.  Until I add the SSL...

My mongod.conf ssl section:

    ssl:
        mode:                       requireSSL
        PEMKeyFile:                 /etc/ssl/mongo-prod1.pem
        CAFile:                     /etc/ssl/ca-chain.cert.pem
        PEMKeyPassword:             xxxxxxxxxxxxxxxx
        allowConnectionsWithoutCertificates:  true

Where the mongo-prod[1-3].pem key files contain the server key + the server cert cat'd into a single file...

When I attempt to enable SSL/TLS is when things blow-up and throw exceptions, most of which are similar to:

Tue Jan 26 16:13:52.588 E NETWORK  [conn8070] SSL peer certificate validation failed:unsupported certificate purpose

Tue Jan 26 16:13:52.588 W -        [conn8070] DBException thrown :: caused by :: 9001 socket exception [CONNECT_ERROR] for

Tue Jan 26 16:13:52.593 I -        [conn8070]

 0xf82712 0xf03fbd 0x857bce 0xf42da1 0xf3b302 0xf31181 0xf33c40 0x7f5875e66182 0x7f587492d47d

When I built the server certs, I was very careful to specify the -extensions server_cert flag.  My cert validation dumps show:

        X509v3 extensions:
            X509v3 Basic Constraints:
                CA:FALSE
            Netscape Cert Type:
                SSL Server
            Netscape Comment:
                OpenSSL Generated Server Certificate
            X509v3 Subject Key Identifier:
                F1:85:92:F6:9E:6F:DD:F8:11:52:CA:FA:45:34:A3:A1:E6:EF:BC:E7
            X509v3 Authority Key Identifier:
                keyid:A1:F5:E5:61:EE:CF:46:93:5A:2B:76:DA:E6:9E:DE:40:18:41:9F:25
                DirName:/C=US/ST=California/O=PathwayGenomics
                serial:10:01


            X509v3 Key Usage: critical
                Digital Signature, Key Encipherment
            X509v3 Extended Key Usage:
                TLS Web Server Authentication

output from rs.status():

ULPROD:SECONDARY> rs.status()
{
 "set" : "ULPROD",
 "date" : ISODate("2016-01-27T00:08:21.917Z"),
 "myState" : 2,
 "members" : [
 {
 "_id" : 0,
 "name" : "mongo-prod1:27017",
 "health" : 1,
 "state" : 2,
 "stateStr" : "SECONDARY",
 "uptime" : 2400,
 "optime" : Timestamp(1453333325, 28),
 "optimeDate" : ISODate("2016-01-20T23:42:05Z"),
 "configVersion" : 3,
 "self" : true
 },
 {
 "_id" : 1,
 "name" : "mongo-prod2:27017",
 "health" : 0,
 "state" : 8,
 "stateStr" : "(not reachable/healthy)",
 "uptime" : 0,
 "optime" : Timestamp(0, 0),
 "optimeDate" : ISODate("1970-01-01T00:00:00Z"),
 "lastHeartbeat" : ISODate("2016-01-27T00:08:19.749Z"),
 "lastHeartbeatRecv" : ISODate("1970-01-01T00:00:00Z"),
 "configVersion" : -1
 },
 {
 "_id" : 2,
 "name" : "mongo-prod3:27017",
 "health" : 0,
 "state" : 8,
 "stateStr" : "(not reachable/healthy)",
 "uptime" : 0,
 "optime" : Timestamp(0, 0),
 "optimeDate" : ISODate("1970-01-01T00:00:00Z"),
 "lastHeartbeat" : ISODate("2016-01-27T00:08:19.923Z"),
 "lastHeartbeatRecv" : ISODate("1970-01-01T00:00:00Z"),
 "configVersion" : -1
 }
 ],
 "ok" : 1
}

My mongo client alias:

alias mongo='mongo --ssl --sslAllowInvalidHostnames --sslCAFile /etc/ssl/ca-chain.cert.pem --host mongo-prod1'

Thanks for listening... hope someone has encountered this before and can steer me to a better path.

--mike

[Micheal Shallop]

Hey - for anyone else with similar issues, here's the solution...

When creating your certs, normally one would specify if the cert being generated as a server or a client certificate.  In order to get mongodb to work with SSL, you have to generate the (server and client) certs omitting the [ server | client ] parameter option.

For example:

openssl ca -config intermediate/openssl.cnf \
      -extensions server_cert -days 375 -notext -md sha256 \
      -in intermediate/csr/www.example.com.csr.pem \
      -out intermediate/certs/www.example.com.cert.pem

Would be:

openssl ca -config intermediate/openssl.cnf \
      -days 375 -notext -md sha256 \
      -in intermediate/csr/www.example.com.csr.pem \
      -out intermediate/certs/www.example.com.cert.pem

instead.

Hope this helps someone else....

--mike

[Derek Gransaull]

This helped me. It's a pity the Mongo Docs are so sparse and, in this case, likely incorrect. I had tried with both clientAuth and serverAuth like the docs say, but that didn't work either. The only way it works is as you've said ... with no extensions. Thanks Micheal! 

[Emilio Scalise]

Hi All,

If you set the SSL server extension for your server certificate, you can't use that certificate for client authentication and thus MongoDB can't use it to connect to the other replica set members. To specify a different client SSL certificate for the internal connections between the MongoDB replica set members or sharded cluster members you need to set the parameter "clusterFile" specifying a SSL PEM file with the client extension:

  ssl:
    CAFile: /opt/ca-bundle.crt
    PEMKeyFile: /opt/server.pem
    PEMKeyPassword: password
    clusterFile: /opt/client.pem
    clusterPassword: password
    mode: requireSSL

By default if "clusterFile" is not set it will be equal to "PEMKeyFile". This is why if you generate a SSL certificate without the "server" extension it will work.

I hope that this clarifies the issue discussed.

Kind regards,

Emilio