cognitoinator 0.2.2
Log into Cognito, assume an IAM role, directly access JWT's from your Cognito session, and use boto3 all with Cognito credentials
License: Apache 2.0
Requires Python: >=3.8

Easy way to log into Cognito, assume IAM roles, access Cognito JWT, and use boto3 with Cognito credentials
===========================================================================================================

IMPORTANT!
----------

**If you have come here looking for cognito-assume-role then you should
update your code to use cognitoinator. cognito-assume-role is no longer
maintained**

Currently supports USER_SRP_AUTH and USER_PASSWORD_AUTH using
enhanced Cognito auth flow. Custom auth flows or administrative auth are
not currently supported although I suppose you could monkey patch the
needed code. It was written using only public methods exposed by the
boto3/botocore API to help ensure that changes to boto3 wont break
any (what would be otherwise) monkey patched code. This should also
maintain the ability to use this library for your boto3 calls that are
not using Cognito within the same script by simply passing a normal
boto3 client credential argument.

USAGE
=====

This module can insert a botocore.credentials.CredentialProvider into
the provider chain. Using this provider we can assume an IAM role
through get_credentials_for_identity(). To do this we provide three
functions:

-   client (wraps boto3.client())
-   resource (wraps boto3.resource())
-   Session (wraps boto3.session.Session())

All three of these functions accept all normal boto3 args and kwargs
plus some that are specific to this module. We provide three ways of
providing the initial credentials.

Configuration
=============

### Env vars

These will take affect before any other credential provider, including
the standard env provider that looks for AWS\_SECRET\_ACCESS\_KEY and
AWS\_ACCESS\_KEY\_ID. If one or more of the following non-optional
variables are found in environ then we will automatically go to env
based credential mapping

-   COGNITO_USERNAME
-   COGNITO_PASSWORD
-   COGNITO_USER_POOL_ID
-   COGNITO_IDENTITY_POOL_ID
-   COGNITO_APP_ID
-   COGNITO_METADATA (Deserialized and passed as ClientMetadata in
    boto3.client("cognito-idp").initiate_auth()) - Optional
-   AWS_ROLE_ARN - Optional

### Profile

Credential file locations, if not specified, will be resolved in the
order of
- direct arguments to client
- COGNITO_CREDENTIALS_FILE env var
- ~/.aws/cognito_credentials file

Config files take the following form:

``` {.toml}
[default]
username=myusername
password=***********
app_id=1234567890
user_pool_id=abcdefg
identity_pool_id=us-east-1:1234567890
region=us-east-1
metadata={"foo": "bar"}
auth_type=user_srp
```

All values except for region and metadata are required if using a profile. Using a profile is done by passing the kwarg "cognito_profile=profile name" to client, Session, or resource.

### Direct configuration

``` {.json}
{
  "username": "myusername",
  "password": "***********",
  "app_id": "1234567890",
  "user_pool_id": "abcdefg",
  "identity_pool_id": "us-east-1:1234567890",
  "region": "us-east-1",
  "metadata": {"foo": "bar"},
  "auth_type": "user_srp"
}
```

Same rules apply for required values as when using a profile. Direct
configuration is done by passing the config dictionary to kwarg
cognito_config when creating a client, resource, or Session. Note that
cognito_profile and cognito_config are mutually exclusive. Trying to
use both at once will raise an Assertion exception.

### Precedence of CredentialProviders

The order of resolution for credential providers remains unchanged
except for setting environment variables for Cognito will take affect
before any AWS credential environment variables.

**Precedence of arguments** Any value that can be defined in either an
environment variable, explicitly passed as a kwarg ( passed to client,
resource, or Session) or can be part of a config or profile is resolved
in the following order:

-   explicit arguments
-   specified by config or profile
-   environment variables

### Auth types

The client, resource, and Session functions also accept an argument of
auth_type. This can be user_srp (default) or user_password.

Assuming a role
===============

### Creating a client and assuming a role using env config

``` {.python}
from cognitoinator import client

client = boto3.client("s3")
client.list_buckets()
```

### Creating a client that uses a config

``` {.python}
from cognitoinator import client

client = boto3.client("s3", profile="my_profile")
client.list_buckets()
```

### Using resource with env vars and specifying auth\_type and region

``` {.python}
from cognitoinator import resource

resource = boto3.resource("s3", auth_type="user_password", region_name="us-east-2")
resource.create_bucket(Bucket="my-file-dump-woot-woot")
```

### Creating a session that we can reuse for multiple clients

``` {.python}
from cognitoinator import Session
session = Session(auth_type="user_srp", region_name="us-east-2")
s3 = session.client("s3")
dynamo = resource("dynamodb")
table = dynamo.Table("my_table")
```

Important notes on assuming roles
=================================

-   passing a role arn directly only works when your Identity Pool is
    configured for "Use default role" in (See Identity Pool -> Edit
    -> Authentication Providers -> Authenticated role selection). When
    using "rules" or "token" you cannot directly pass a role.
-   Assuming a role requires using enhanced_auth_flow. This is a
    requirement of AWS's assume-role-with-web-identity
-   Cognitoinator automatically will append the sub of the Cognito user
    to the role_session_name. This causes the IAM user accessing
    resources to be identified by their sub. This is very handy for
    creating resource based policies with grants to specific Cognito
    users based on their role_session_name.

Getting a JWT
=============

### Basic use

If you do not want to assume a role but would still like to access
cognito id token directly, for instance to make Appsync calls, you can
use the TokenFetcher class. It provides the following properties:

-   tokens (dict): A dictionary containing id_token, access_token,
    token_expires, and refresh_token
-   id_token
-   access_token
-   refresh_token
-   token_expires

Methods: - fetch(): Updates and returns self.tokens

All properties are available upon instantiation. The constructor accepts
the same kwargs as Session(), along with option "server (bool)".
Setting "server=True" will start a background process to keep tokens
refreshed automatically, which means that your tokens will always be up
to date.

**Example**

``` {.python}
from cognitoinator import TokenFetcher

cognito_credentials = TokenFetcher()
print(cognito_credentials)

print(cognito_credentials.id_token)
print(cognito_credentials.access_token)
print(cognito_credentials.token_expires)
print(cognito_credentials.refresh_token)
```

### Getting tokens from cognitoinator.Session

If creating a Session directly the cognito id, refresh, and access
tokens, as well as the expires time are available as properties on the
Session object. Tokens are stored in memory by default, but passing a
file name as "token_cache=/file/path.txt" into Session() will write
cause the tokens to be written to the specified file as JSON. Passing a
path to a file that does not exist will raise a FileNotFoundError.
Passing a path to a file that is not writeable will raise OSError.
Properties to access tokens:

-   Session().id_token
-   Session().access_token
-   Session().refresh_token
-   Session().token_expires
-   Session().cognito_tokens (All of the above in a dict)

Because of how boto3 generates clients there is no way to access the
"parent" session. This means that to use this feature you will need to
create a Session() object and then create your clients/resources off of
that Session(). Example:

``` {.python}
from cognitoinator import Session

session = Session()
s3 = session.s3()
s3.list_buckets()
print(session.token_expires)

# Outputs 2020-09-19T23:17:28CDT
```

``` {.python}
from cognitoinator import TokenFetcher

s = TokenFetcher()
# Strings shortened for brevity
print(s.id_token[-10:-1])
print(s.access_token[-10:-1])
print(s.refresh_token[-10:-1])
print(s.expires)

"""
Results in:
  6xAb_vMKv
  4Ruc_TB_h
  m3Htft_Op
  2020-09-19T05:16:31
"""
```