How to change default authentication method from SCRAM-SHA-1 back to MONGODB-CR

Question

I just upgrade to mongodb 3.0 from 2.4 and I am getting this error when I log in:

 "Failed to authenticate thisuser@admin with mechanism MONGODB-CR:    AuthenticationFailed MONGODB-CR credentials missing in the user document"

Elsewhere on stackoverflow I found people who had hacks for this, but where can I specify for the whole database to use CR as the method? Isn't this a global setting?

I'm using pymongo and it has CR style instructions that work fine for me.

Answer 1

After reading the same answer from several sources, I found a detailed enough step-by-step fix for this that is worth sharing back here. The paths are specific to webfaction.com, but you can obvious adjust ports and paths to suit yourself.

1) Start MongoDB 3.0 without --auth enabled, so you can change how it authenticates.

• from /webapps/mongo/bin/ run ./mongod --dbpath $HOME/webapps/mongo/data --port 1400

• SSH login as admin from /webapps/mongo/bin/ run ./mongo localhost:1400/admin

2) Run mongodb within SSH on the admin database:

>
> var schema = db.system.version.findOne({"_id" : "authSchema"})
> schema.currentVersion = 3
> db.system.version.save(schema)
> exit

currentVersion = 3 will make the default MONGODB-CR, the default for MongoDB version 2x. Version 3.0 uses SCRAM-SHA-1 by default instead.

3) restart MongoDB with --auth enabled. from /webapps/mongo/bin I would run ./mongod --dbpath $HOME/webapps/mongo/data --setParameter authenticationMechanisms=MONGODB-CR --auth --port 1400

... and if I want this service to remain active it would be: @reboot nohub nice <FULL PATH>/mongod --dbpath $HOME/webapps/mongo/data --setParameter authenticationMechanisms=MONGODB-CR --auth --port 1400

The setParameter authenticationMechanisms=MONGODB-CR may be redundant, or meaningless, but I'll leave it in there for now.

Now I can remotely connect so long as my user account is associated with that database, using db.grantRolesToUser( "marc", [ {role: "readWrite", db:"fbc"}, {role: "dbOwner", db:"fbc"}] ) ... and so forth in the admin database.