Metadata-Version: 2.1
Name: pysasl
Version: 1.0.0rc6
Summary: Pure Python SASL client and server library.
Home-page: https://github.com/icgood/pysasl/
Author: Ian Good
Author-email: ian@icgood.net
License: MIT
Classifier: Development Status :: 3 - Alpha
Classifier: Intended Audience :: Developers
Classifier: Intended Audience :: Information Technology
Classifier: License :: OSI Approved :: MIT License
Classifier: Programming Language :: Python
Classifier: Programming Language :: Python :: 3.7
Classifier: Programming Language :: Python :: 3.8
Classifier: Programming Language :: Python :: 3.9
Classifier: Programming Language :: Python :: 3.10
Requires-Python: ~=3.7
Description-Content-Type: text/markdown
Provides-Extra: hashing
License-File: LICENSE.md

pysasl
======

Pure Python SASL client and server library. The design of the library is
intended to be agnostic of the protocol or network library.

The library currently offers `PLAIN`, `LOGIN`, and `CRAM-MD5` mechanisms by
default. The `EXTERNAL` and `XOAUTH2` mechanisms are also available for special
circumstances.

There are currently no plans to implement security layer negotiation support.

[![build](https://github.com/icgood/pysasl/actions/workflows/python-package.yml/badge.svg)](https://github.com/icgood/pysasl/actions/workflows/python-package.yml)
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#### [API Documentation](https://icgood.github.io/pysasl/)

Installation
============

Available in [PyPi](https://pypi.python.org/):

```
pip install pysasl
```

### Running Tests

Install into a virtual environment:

```
python3 -m venv .venv
source .venv/bin/activate

pip install -r requirements-dev.txt
```

Run the tests and report coverage metrics:

```
invoke
```

Usage
=====

## Server-side

Server-side SASL has three basic requirements:

* Must advertise supported mechanisms,
* Must issue authentication challenges to the client and read responses,
* Must determine if credentials are considered valid.

#### Advertising Mechanisms

Implementations may decide on any sub-set of mechanisms to advertise. Make this
choice when instantiating the [`SASLAuth`][1] object:

```python
from pysasl import SASLAuth

auth1 = SASLAuth.defaults()  # equivalent to...
auth2 = SASLAuth.named([b'PLAIN', b'LOGIN'])
```

To get the names of all available mechanisms:

```python
mechanisms = [mech.name for mech in auth1.server_mechanisms]
mech = auth1.get_server(b'PLAIN')
```

#### Issuing Challenges

Once a mechanism has been chosen by the client, enter a loop of issuing
challenges to the client:

```python
def server_side_authentication(sock, mech):
    challenges = []
    while True:
        try:
            creds, _ = mech.server_attempt(challenges)
            return creds
        except ServerChallenge as chal:
            sock.send(chal.data + b'\r\n')
            resp = sock.recv(1024).rstrip(b'\r\n')
            challenges.append(ChallengeResponse(chal.data, resp))
```

It's worth noting that implementations are not quite that simple. Most will
expect all transmissions to base64-encoded, often with a prefix before the
server challenges such as `334` or `+`. See the appropriate RFC for your
protocol, such as [RFC 4954 for SMTP][3] or [RFC 3501 for IMAP][4].

#### Checking Credentials

Once the challenge-response loop has been completed and we are left with the
a [`ServerCredentials`][2] object, we can access information from the
attempt:

```python
from pysasl.identity import ClearIdentity, HashedIdentity

print('Authenticated as:', result.authcid)
print('Authorization ID:', result.authzid)

# To compare to a known cleartext password...
identity = ClearIdentity('myuser', 's3kr3t')
assert result.verify(identity)

# Or to compare hashes...
from pysasl.hashing import BuiltinHash
identity = HashedIdentity('myuser, '1baa33d03d0...', hash=BuiltinHash())
assert result.verify(identity)

# Or use passlib hashing...
from passlib.apps import custom_app_context
identity = HashedIdentity('myuser', '$6$rounds=656000$...', hash=custom_app_context)
assert result.verify(identity)
```

## Client-side

The goal of client-side authentication is to respond to server challenges until
the authentication attempt either succeeds or fails.

#### Choosing a Mechanism

The first step is to pick a SASL mechanism. The protocol should allow the server
to advertise to the client which mechanisms are available to it:

```python
from pysasl import SASLAuth

auth = SASLAuth.named(advertised_mechanism_names)
mech = auth.client_mechanisms[0]
```

Any mechanism name that is not recognized will be ignored.

#### Issuing Responses

Once a mechanism is chosen, we enter of a loop of responding to server
challenges:

```python
from pysasl.creds.client import ClientCredentials

def client_side_authentication(sock, mech, username, password):
    creds = ClientCredentials(username, password)
    challenges = []
    while True:
        resp = mech.client_attempt(creds, challenges)
        sock.send(resp + b'\r\n')
        data = sock.recv(1024).rstrip(b'\r\n')
        if data == 'SUCCESS':
            return True
        elif data == 'FAILURE':
            return False
        challenges.append(ServerChallenge(data))
```

As you might expect, a real protocol probably won't return `SUCCESS` or
`FAILURE`, that will depend entirely on the details of the protocol.

## Supporting Initial Responses

Some protocols (e.g. SMTP) support the client ability to send an initial
response before the first server challenge, for mechanisms that support it.
A perfectly valid authentication can then have no challenges at all:

```
AUTH PLAIN AHVzZXJuYW1lAHBhc3N3b3Jk
235 2.7.0 Authentication successful
```

In this case, both client-side and server-side authentication should be
handled a bit differently. For example for server-side:

```python
challenges = []
if initial_response:
    challenges.append(ChallengeResponse(b'', initial_response))
```

And for client-side, just call `resp = mech.client_attempt(creds, [])`
to get the initial response before starting the transmission. All
mechanisms should either return an initial response or an empty string
when given an empty list for the second argument.

[1]: https://icgood.github.io/pysasl/pysasl.html#pysasl.SASLAuth
[2]: https://icgood.github.io/pysasl/pysasl.creds.html#pysasl.creds.server.ServerCredentials
[3]: https://tools.ietf.org/html/rfc4954
[4]: https://tools.ietf.org/html/rfc3501#section-6.2.2
## The MIT License (MIT)

Copyright (c) 2022 Ian Good

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

