OtterIO Multi-user Quickstart Guide

June 4, 2026 ยท View on GitHub

OtterIO supports multiple long term users in addition to default user created during server startup. New users can be added after server starts up, and server can be configured to deny or allow access to buckets and resources to each of these users. This document explains how to add/remove users and modify their access rights.

Get started

In this document we will explain in detail on how to configure multiple users.

1. Prerequisites

2. Create a new user with canned policy

Use mc admin policy to create canned policies. Server provides a default set of canned policies namely writeonly, readonly and readwrite (these policies apply to all resources on the server). These can be overridden by custom policies using mc admin policy command.

Create new canned policy file getonly.json. This policy enables users to download all objects under my-bucketname.

cat > getonly.json << EOF
{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Action": [
        "s3:GetObject"
      ],
      "Effect": "Allow",
      "Resource": [
        "arn:aws:s3:::my-bucketname/*"
      ],
      "Sid": ""
    }
  ]
}
EOF

Create new canned policy by name getonly using getonly.json policy file.

mc admin policy add myotterio getonly getonly.json

Create a new user newuser on OtterIO use mc admin user.

mc admin user add myotterio newuser newuser123

Once the user is successfully created you can now apply the getonly policy for this user.

mc admin policy set myotterio getonly user=newuser

3. Create a new group

mc admin group add myotterio newgroup newuser

Once the group is successfully created you can now apply the getonly policy for this group.

mc admin policy set myotterio getonly group=newgroup

4. Disable user

Disable user newuser.

mc admin user disable myotterio newuser

Disable group newgroup.

mc admin group disable myotterio newgroup

5. Remove user

Remove the user newuser.

mc admin user remove myotterio newuser

Remove the user newuser from a group.

mc admin group remove myotterio newgroup newuser

Remove the group newgroup.

mc admin group remove myotterio newgroup

6. Change user or group policy

Change the policy for user newuser to putonly canned policy.

mc admin policy set myotterio putonly user=newuser

Change the policy for group newgroup to putonly canned policy.

mc admin policy set myotterio putonly group=newgroup

7. List all users or groups

List all enabled and disabled users.

mc admin user list myotterio

List all enabled or disabled groups.

mc admin group list myotterio

8. Configure mc

mc alias set myotterio-newuser http://localhost:9000 newuser newuser123 --api s3v4
mc cat myotterio-newuser/my-bucketname/my-objectname

Policy Variables

You can use policy variables in the Resource element and in string comparisons in the Condition element.

You can use a policy variable in the Resource element, but only in the resource portion of the ARN. This portion of the ARN appears after the 5th colon (:). You can't use a variable to replace parts of the ARN before the 5th colon, such as the service or account. The following policy might be attached to a group. It gives each of the users in the group full programmatic access to a user-specific object (their own "home directory") in OtterIO.

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Action": ["s3:ListBucket"],
      "Effect": "Allow",
      "Resource": ["arn:aws:s3:::mybucket"],
      "Condition": {"StringLike": {"s3:prefix": ["${aws:username}/*"]}}
    },
    {
      "Action": [
        "s3:GetObject",
        "s3:PutObject"
      ],
      "Effect": "Allow",
      "Resource": ["arn:aws:s3:::mybucket/${aws:username}/*"]
    }
  ]
}

If the user is authenticating using an STS credential which was authorized from OpenID connect we allow all jwt:* variables specified in the JWT specification, custom jwt:* or extensions are not supported.

List of policy variables for OpenID based STS.

"jwt:sub"
"jwt:iss"
"jwt:aud"
"jwt:jti"
"jwt:upn"
"jwt:name"
"jwt:groups"
"jwt:given_name"
"jwt:family_name"
"jwt:middle_name"
"jwt:nickname"
"jwt:preferred_username"
"jwt:profile"
"jwt:picture"
"jwt:website"
"jwt:email"
"jwt:gender"
"jwt:birthdate"
"jwt:phone_number"
"jwt:address"
"jwt:scope"
"jwt:client_id"

Following example shows OpenID users with full programmatic access to a OpenID user-specific directory (their own "home directory") in OtterIO.

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Action": ["s3:ListBucket"],
      "Effect": "Allow",
      "Resource": ["arn:aws:s3:::mybucket"],
      "Condition": {"StringLike": {"s3:prefix": ["${jwt:preferred_username}/*"]}}
    },
    {
      "Action": [
        "s3:GetObject",
        "s3:PutObject"
      ],
      "Effect": "Allow",
      "Resource": ["arn:aws:s3:::mybucket/${jwt:preferred_username}/*"]
    }
  ]
}

If the user is authenticating using an STS credential which was authorized from AD/LDAP we allow ldap:* variables, currently only supports ldap:user. Following example shows LDAP users full programmatic access to a LDAP user-specific directory (their own "home directory") in OtterIO.

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Action": ["s3:ListBucket"],
      "Effect": "Allow",
      "Resource": ["arn:aws:s3:::mybucket"],
      "Condition": {"StringLike": {"s3:prefix": ["${ldap:user}/*"]}}
    },
    {
      "Action": [
        "s3:GetObject",
        "s3:PutObject"
      ],
      "Effect": "Allow",
      "Resource": ["arn:aws:s3:::mybucket/${ldap:user}/*"]
    }
  ]
}

Common information available in all requests

  • aws:CurrentTime - This can be used for conditions that check the date and time.
  • aws:EpochTime - This is the date in epoch or Unix time, for use with date/time conditions.
  • aws:PrincipalType - This value indicates whether the principal is an account (Root credential), user (OtterIO user), or assumed role (STS)
  • aws:SecureTransport - This is a Boolean value that represents whether the request was sent over TLS.
  • aws:SourceIp - This is the requester's IP address, for use with IP address conditions. If running behind Nginx like proxies, OtterIO preserve's the source IP.
{
  "Version": "2012-10-17",
  "Statement": {
    "Effect": "Allow",
    "Action": "s3:ListBucket*",
    "Resource": "arn:aws:s3:::mybucket",
    "Condition": {"IpAddress": {"aws:SourceIp": "203.0.113.0/24"}}
  }
}
  • aws:UserAgent - This value is a string that contains information about the requester's client application. This string is generated by the client and can be unreliable. You can only use this context key from mc or other OtterIO SDKs which standardize the User-Agent string.
  • aws:username - This is a string containing the friendly name of the current user, this value would point to STS temporary credential in AssumeRoleed requests, instead use jwt:preferred_username in case of OpenID connect and ldap:user in case of AD/LDAP connect. aws:userid is an alias to aws:username in OtterIO.

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