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'clusterAuthMode: x509' failing with "Could not find user "CN=mongod1" for db $external"

spiffly423spiffly423 EntrantCurrent User Role Supporter
edited September 11 in Percona Server for MongoDB
Using the image percona/percona-server-mongodb:4.2, I am attempting to enable clusterAuthMode: x509 on a replicaset. I have followed the instructions here, making sure my certificates conform to the requirements. Each member is failing to connect to the other two members. Looking through the logs, I'm seeing entries like this:
authenticate db: $external { authenticate: 1, mechanism: "MONGODB-X509", user: "CN=mongod1", $db: "$external" }
2020-09-11T19:15:50.644+0000 I  ACCESS   [conn10] Failed to authenticate [email protected]$external from client with mechanism MONGODB-X509: UserNotFound: Could not find user "CN=mongod1" for db "$external"

This would suggest that a user with the same name as each connecting member's CN is expected; I've scoured the mongodb documentation and though there is documentation talking about the need for clients to authenticate with an existing user, I see no indication that such a user is needed for internal/membership authentication, which db they should be created on with what privileges, etc.

Is such a user necessary for each member when using x509 auth mode (if so, please point me to the documentation I've apparently overlooked!), or is there perhaps something else I'm missing here? Any help appreciated!

Here is my conf file: (edit: anyone know of a better way to display my conf file? when i wrapped it in code, it put it all in one line...)
  port: 17017
  bindIpAll: true
    mode: requireTLS
    CAFile: /certs/myCA.pem
    certificateKeyFile: /certs/myCert.pem
  oplogSizeMB: 4096
  replSetName: set1
  enableMajorityReadConcern: false
  enableLocalhostAuthBypass: true
  fork: "false"
  dbPath: /data/db
  engine: wiredTiger
    enabled: true
      blockCompressor: snappy
      directoryForIndexes: true
      cacheSizeGB: 20
  enableEncryption: true
  encryptionKeyFile: /etc/mongodb.keyfile
  authorization: enabled
  clusterAuthMode: x509


  • spiffly423spiffly423 Entrant Current User Role Supporter
    To put it in a nutshell: does anyone know if a user is needed for each member of a replica set when using `clusterAuthMode: x509`? Seems to be the case, but I'm not finding anything in the documentation that states this, what the user permissions should be, etc.
  • Igor SolodovnikovIgor Solodovnikov Percona Percona Staff Role
    edited October 5

    Hello @spiffly423

    Does 'mongod1' part of your "CN=mongod1" matches the hostname of the server?

    Here is quote from the

    > Either the Common Name (CN) or one of the Subject Alternative Name (SAN) entries must match the hostname of the server, used by the other members of the cluster.

  • spiffly423spiffly423 Entrant Current User Role Supporter
    edited October 27

    @Igor Solodovnikov thanks for your response. Yes, the CN had matched the hostname of the server.

    Finally figured this out. We had hosts that were named in an unorthodox way, e.g. "mongod1.dc1" that the x509 authentication didn't like. Once I dropped the .dc1 on the hostname, it played nice. We were probably breaking some convention by adding .dc1, etc. to the hostname.

    Perhaps the reason why it was failing is because it assumed everything after the first . was part of the domain? e.g. it was stripping down to mongod1 and then that of course failed to match with the actual hostname of mongod1.dc1.

    At any rate, very happy to have it working now!

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