iam_generator
Generates AWS IAM Users, Groups, Roles, and Managed Policies from a YAML configuration and Jinja2 Templates
Build Environment
A Python 2.7 interpreter with the following libraries installed:
sudo pip install jinja2
sudo pip install troposphere
NOTE: At present, build is tested on OSX and Linux. Pull requests welcome for Windows build support!
General Function
Everything is driven by the config.yaml file. In this file you describe your account structure, and desired managed policies, roles, users and groups.
Managed policy json structure is kept in jinja2 templates files to allow for variable substitution for specific customization of ARNs and trusts etc.
When build.py is executed a CloudFormation template is built per account. They are availble in the output_templates directory to be uploaded to CloudFormation for deployment in each account.
This project wouldn't be possible without the hard work done by the Troposphere and Jinja project teams. Thanks!
config.yaml key sections
There are five main sections of the config.yaml:
global:
...
accounts:
...
policies:
...
roles:
...
users:
...
groups:
...
global:
section
Controls our our genereated templates behaviour. There are two key sections. names:
and template_outputs
.
The names:
section looks like this:
global:
names:
policies: False
roles: True
users: True
groups: True
This section allows control over the IAM Naming of the resources. When values are set to True
they will be explicitly named based on the config.yaml entry. When set to False
CloudFormation will generate a name for you.
For example:
policies:
cloudFormationAdmin:
description: CloudFormation Administrator
policy_file: cloudFormationAdmin.j2
if polices: True
is set, the name of the managed policy that CloudFormation creates will be cloudFormationAdmin
. If polices: False
then CloudFormation will generate a unique value using the stack prefix and a suffix eg: PolicyStack-cloudFormationAdmin-ACH753NADF
.
If the global:
section is omitted, it will function with the following default values:
global:
names:
policies: False
roles: True
users: True
groups: True
template_outputs: enabled
The template_outputs:
value allows control over whether the CloudFormation templates will include Output values for the elements they create. There is a limit in Cloudformation templates of 60 output values. You will hit this much sooner than the 200 Resource limit. The main reason to include an output is so it can be imported in a stack layered above. If you don't intend on layering any stacks above this one then disabling outputs is absolutely fine.
Set template_outputs: enabled
to include template outputs. Set template_outputs: disabled
to disable output values for templates.
accounts:
section
Here's an example of the accounts section:
accounts:
central:
id: 123456678910
parent: true
saml_provider: ProdADFS
dev1:
id: 109876543210
dev2:
id: 309876543210
prod:
id: 209876543210
accounts:
is a dictionary of friendly account names. These friendly names can be used throughout the rest of the YAML file and are available to the jinja2 templates.
Note that saml_provider
is optional. If it is used in a Role's trust:
list it will generate the appropriate trust policy for console federation.
Account resolution in the yaml:
- Use the keyword
all
to refer to all of the accounts in theaccounts:
section. - Use the keyword
parent
to refer to the account you've marked asparent: true
. - Use the keyword
children
to refer to all accounts except the parent. - You can also refer to a specific account by friendly name or it's ID. eg:
dev1
- You can also use python regular expressions. eg:
dev.*
to target both developement accounts.
Using these mechanisms it should be easy to specifically manage what account each element lands in.
policies:
section
Managed Policies derived from a jinja2 template
Here's an example of a managed policy based on a jinja2 policy template:
policies:
cloudFormationAdmin:
description: CloudFormation Administrator
policy_file: cloudFormationAdmin.j2
template_vars:
cloudformation_bucket: bucket-cloudformation
in_accounts:
- parent
- dev.*
This will create a managed policy with the name cloudFormationAdmin (along with the prefix and suffix that CloudFormation Adds automatically). It will base the policy document on the contents of of the cloudFormationAdmin.j2 jinja2 template. It will be placed into the accounts 123456678910 (which is our parent
) as well as accounts 109876543210 and 309876543210 because their friendly names (dev1
and dev2
) match our regular expression dev.*
.
Lets disect this a bit.
policies:
is a dictionary of policy names. This assures they are kept unique within the account and generated CloudFormation template.
policy_file:
needs to be located in the /policy/
directory, and would look something like this:
{
"Version": "2012-10-17",
"Statement": [
{
"Effect": "Allow",
"Action": [
"cloudformation:*"
],
"Resource": [
"*"
]
},
{
"Effect": "Allow",
"Action": [
"s3:ListBucket"
],
"Resource": [
"arn:aws:s3:::{{ template_vars.cloudformation_bucket }}"
]
},
{
"Effect": "Allow",
"Action": [
"s3:PutObject",
"s3:GetObject",
"s3:DeleteObject"
],
"Resource": ["arn:aws:s3:::{{ template_vars.cloudformation_bucket }}/*"]
}
]
}
Notice the variable substitution in the template {{ template_vars.cloudformation_bucket }}
.
Notice the value for this is derived from this section of the config.yaml:
...
template_vars:
cloudformation_bucket: bucket-cloudformation
...
Jinja2 templates will get the following variable namespaces passed to them:
template_vars
as described above.account
which is the account ID of the account that is being worked on.parent_account
which is the account ID of the account marked asparent: true
.config
which is the entire config.yaml file!
Managed Policies for sts:AssumeRole (auto generated!)
Here's an example of the yaml to create a managed policy for sts:AssumeRole with the specified roles into the specified accounts.
policies:
assumeAdmin:
description: Allow assumption of the Admin role in all children accounts from the parent
assume:
roles:
- Admin
accounts:
- children
in_accounts:
- parent
This will create this policy document . . .
"Version": "2012-10-17",
"Statement": [
{
"Action": "sts:AssumeRole",
"Effect": "Allow",
"Resource": "arn:aws:iam::109876543210:role/Admin"
},
{
"Action": "sts:AssumeRole",
"Effect": "Allow",
"Resource": "arn:aws:iam::309876543210:role/Admin"
},
{
"Action": "sts:AssumeRole",
"Effect": "Allow",
"Resource": "arn:aws:iam::209876543210:role/Admin"
},
]
. . . and insert it into the CloudFormation template for account 123456678910 (which was marked parent).
roles:
section
Example of a role that can be assumed from another account.
roles:
NetworkAdmin:
trusts:
- parent
managed_policies:
- arn:aws:iam::aws:policy/job-function/NetworkAdministrator
- arn:aws:iam::aws:policy/ReadOnlyAccess
- cloudFormationAdmin
in_accounts:
- all
This will create a role called NetworkAdmin. It will have two AWS managed policies, and one policy referenced from the policies:
section of the config.yaml.
The assume role policy document will be automatically generated to trust the parent:
{
"Version": "2012-10-17",
"Statement": [
{
"Action": "sts:AssumeRole",
"Effect": "Allow",
"Principal": {
"AWS": "arn:aws:iam::123456678910:root"
}
}
]
}
Example of an ec2 role
roles:
s3andDynamoWrite:
trusts:
- ec2.amazonaws.com
inline_policies: []
managed_policies:
- arn:aws:iam::aws:policy/AmazonS3FullAccess
- arn:aws:iam::aws:policy/AmazonDynamoDBFullAccess
- arn:aws:iam::aws:policy/AmazonElasticMapReduceFullAccess
in_accounts:
- all
In this case our trusts:
is ec2.amazonaws.com. This can be any service like config.amazonaws.com, lambda.amazonaws.com, etc.
Since we're trusting ec2.amazonaws.com we will automatically create an instance profile for this role so it can be used from ec2. No additional configuration required.
Example of a federated role.
In cases that we have a saml_provider:
in our parent account we can reference it in our trust.
roles:
AWS_Admins:
trusts:
- ProdADFS
managed_policies:
- assumeAdmin
in_accounts:
- parent
This will generate the following assume role policy document automatically . . .
{
"Version": "2012-10-17",
"Statement": [
{
"Action": "sts:AssumeRoleWithSAML",
"Condition": {
"StringEquals": {
"SAML:aud": "https://signin.aws.amazon.com/saml"
}
},
"Effect": "Allow",
"Principal": {
"Federated": "arn:aws:iam::123456678910:saml-provider/ProdADFS"
}
}
]
}
. . . and place it (along with the role definition) in the parent CloudFormation template.
users:
section
An example of a user that is not a member of a group, and has a managed_policy directly attached.
users:
adam:
managed_policies:
- assumeAdmin
password: CHANGEME
in_accounts:
- parent
Optionally specify a password:
for the user. The flag is set to force a password change at first login. The password is clear text, so be careful!
An example of a user as a member of groups
users:
adam:
groups:
- Admins
in_accounts:
- parent
Our group:
field is the name of a group. This can be a name that already exists, or is in the config.yaml file. Existing groups just need to be the name of the group, not an ARN.
groups:
section
groups:
Admins:
managed_policies:
- assumeAdmin
- arn:aws:iam::aws:policy/ReadOnlyAccess
in_accounts:
- parent
groups:
is once again a dictionary of group names that you'd like created. It allows for a list of managed_policies:
to attach. These can be either an existing managed policy arn, or the name of a policy created in the policies:
section of the YAML.
retain_on_delete
variable
CloudFormation permits retention on deletion of a resource. This is described here.
For any resource in the policies:
roles:
groups:
or users:
section include retain_on_delete: true
to configure the CloudFormation template to retain that resource on deletion. This let's you keep a resource that may not necessarily remain under management of this CloudFormation template any longer.
eg:
roles:
NetworkAdmin:
retain_on_delete: true
trusts:
- parent
managed_policies:
- arn:aws:iam::aws:policy/job-function/NetworkAdministrator
- arn:aws:iam::aws:policy/ReadOnlyAccess
- cloudFormationAdmin
in_accounts:
- all
If this section is removed from the config.yaml, and a stack-update executed, the 'NetworkAdmin' Role will persist in the account and no longer be managed by CloudFormation.
Default value is retain_on_delete: false
which does not need to be explicitly declared anywhere. This matches the default behaviour of CloudFormation.
Importing resources from other templates
You are able to specify the keyword of import:
within the config.yaml file. Use this for managed_policies, users, groups, or roles. This will substiute the appropraite Fn:ImportValue within the template to import from an existing CloudFormation templates Exports.
Example of an import for a role:
roles:
NetworkAdmin:
trusts:
- parent
managed_policies:
- import:name_of_cfn_export
in_accounts:
- all