Mongodb : Connecting to a user with password when tls is enabled

Question

I'm setting a replica set on 3 mongodb instances on debian 9 and I enabled TLS authentication for the replica set members. Here's the configuration:

security:
    authorization: enabled
    clusterAuthMode: x509
net:
   tls:
      mode: requireTLS
      certificateKeyFile: crt-key.pem
      CAFile: chain.crt
      clusterFile: crt-key.pem
      certificateKeyFilePassword: XXXXXX
      clusterPassword: XXXXXX
      allowConnectionsWithoutCertificates: true

replication:
   replSetName: "my-replica-set"

The replication works fine but I can't connect with a username/password to the database:

mongosh --port 27017  --authenticationDatabase "admin" -u "user" -p 
MongoServerSelectionError: connection <monitor> to 127.0.0.1:27017 closed

Here's the log:

{"t":{"$date":"2022-05-30T18:02:07.696+02:00"},"s":"I",  "c":"NETWORK",  "id":22988,   "ctx":"conn30","msg":"Error receiving request from client. Ending connection from remote","attr":{"error":{"code":141,"codeName":"SSLHandshakeFailed","errmsg":"The server is configured to only allow SSL connections"},"remote":"127.0.0.1:46486","connectionId":30}}

Answer 1

net:
   tls:
      certificateKeyFile: crt-key.pem
      clusterFile: crt-key.pem

is redundant. If clusterFile is not provided then certificateKeyFile is used. So, you can simply use

net:
   tls:
      mode: requireTLS
      certificateKeyFile: crt-key.pem
      CAFile: chain.crt
      certificateKeyFilePassword: XXXXXX
      allowConnectionsWithoutCertificates: true

mode: requireTLS means, client and replicaset members have to use TLS/SSL, thus you must enable TLS/SSL also for client.

You need to specify tls option:

mongosh --tls --port 27017 --authenticationDatabase "admin" -u "user" -p 

Depending on your openssl library version, you may also have to specify the CA-File, ie

mongosh --tls --tlsCAFile "chain.crt" --port 27017 --authenticationDatabase "admin" -u "user" -p 

If you like to enable TLS/SSL only for replicaset members, then use

net:
   tls:
      mode: preferTLS

Now, you can connect with

mongosh --port 27017 --authenticationDatabase "admin" -u "user" -p 

Note, depending on your CA this setup can be security risk. If chain.crt is your own CA protected with your secret private key, then you are on the safe side. However, chain.crt also could be a company wide, commonly used CA. In this case an attacker only needs to create an arbitrary certificate where the Organization attributes (O's), the Organizational Unit attributes (OU's), and the Domain Components (DC's) matches the crt-key.pem and which is accepted by chain.crt (which could be done by a simple ticket to your IT department).

Organization attributes (O's), the Organizational Unit attributes (OU's), and the Domain Components (DC's) of crt-key.pem server certificate you get simply by

openssl s_client -showcerts -connect <hostname>:27017