oauth_api.py

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"""
The MIT License

Copyright (c) 2007 Leah Culver

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.
"""

import cgi
import urllib
import time
import random
import urlparse
import hmac
import binascii


VERSION = '1.0' # Hi Blaine!
HTTP_METHOD = 'GET'
SIGNATURE_METHOD = 'PLAINTEXT'


class OAuthError(RuntimeError):
    """Generic exception class."""
    def __init__(self, message='OAuth error occured.'):
        self.message = message

def build_authenticate_header(realm=''):
    """Optional WWW-Authenticate header (401 error)"""
    return {'WWW-Authenticate': 'OAuth realm="%s"' % realm}

def escape(s):
    """Escape a URL including any /."""
    return urllib.quote(s, safe='~')

def _utf8_str(s):
    """Convert unicode to utf-8."""
    if isinstance(s, unicode):
        return s.encode("utf-8")
    else:
        return str(s)

def generate_timestamp():
    """Get seconds since epoch (UTC)."""
    return int(time.time())

def generate_nonce(length=8):
    """Generate pseudorandom number."""
    return ''.join([str(random.randint(0, 9)) for i in range(length)])

def generate_verifier(length=8):
    """Generate pseudorandom number."""
    return ''.join([str(random.randint(0, 9)) for i in range(length)])


class OAuthConsumer(object):
    """Consumer of OAuth authentication.

    OAuthConsumer is a data type that represents the identity of the Consumer
    via its shared secret with the Service Provider.

    """
    key = None
    secret = None

    def __init__(self, key, secret):
        self.key = key
        self.secret = secret


class OAuthToken(object):
    """OAuthToken is a data type that represents an End User via either an access
    or request token.

    key -- the token
    secret -- the token secret

    """
    key = None
    secret = None
    callback = None
    callback_confirmed = None
    verifier = None

    def __init__(self, key, secret):
        self.key = key
        self.secret = secret

    def set_callback(self, callback):
        self.callback = callback
        self.callback_confirmed = 'true'

    def set_verifier(self, verifier=None):
        if verifier is not None:
            self.verifier = verifier
        else:
            self.verifier = generate_verifier()

    def get_callback_url(self):
        if self.callback and self.verifier:
            # Append the oauth_verifier.
            parts = urlparse.urlparse(self.callback)
            scheme, netloc, path, params, query, fragment = parts[:6]
            if query:
                query = '%s&oauth_verifier=%s' % (query, self.verifier)
            else:
                query = 'oauth_verifier=%s' % self.verifier
            return urlparse.urlunparse((scheme, netloc, path, params,
                query, fragment))
        return self.callback

    def to_string(self):
        data = {
            'oauth_token': self.key,
            'oauth_token_secret': self.secret,
        }
        if self.callback_confirmed is not None:
            data['oauth_callback_confirmed'] = self.callback_confirmed
        return urllib.urlencode(data)

    def from_string(s):
        """ Returns a token from something like:
        oauth_token_secret=xxx&oauth_token=xxx
        """
        params = cgi.parse_qs(s, keep_blank_values=False)
        key = params['oauth_token'][0]
        secret = params['oauth_token_secret'][0]
        token = OAuthToken(key, secret)
        try:
            token.callback_confirmed = params['oauth_callback_confirmed'][0]
        except KeyError:
            pass # 1.0, no callback confirmed.
        return token
    from_string = staticmethod(from_string)

    def __str__(self):
        return self.to_string()


class OAuthRequest(object):
    """OAuthRequest represents the request and can be serialized.

    OAuth parameters:
        - oauth_consumer_key
        - oauth_token
        - oauth_signature_method
        - oauth_signature
        - oauth_timestamp
        - oauth_nonce
        - oauth_version
        - oauth_verifier
        ... any additional parameters, as defined by the Service Provider.
    """
    parameters = None # OAuth parameters.
    http_method = HTTP_METHOD
    http_url = None
    version = VERSION

    def __init__(self, http_method=HTTP_METHOD, http_url=None, parameters=None):
        self.http_method = http_method
        self.http_url = http_url
        self.parameters = parameters or {}

    def set_parameter(self, parameter, value):
        self.parameters[parameter] = value

    def get_parameter(self, parameter):
        try:
            return self.parameters[parameter]
        except:
            raise OAuthError('Parameter not found: %s' % parameter)

    def _get_timestamp_nonce(self):
        return self.get_parameter('oauth_timestamp'), self.get_parameter(
            'oauth_nonce')

    def get_nonoauth_parameters(self):
        """Get any non-OAuth parameters."""
        parameters = {}
        for k, v in self.parameters.iteritems():
            # Ignore oauth parameters.
            if k.find('oauth_') < 0:
                parameters[k] = v
        return parameters

    def to_header(self, realm=''):
        """Serialize as a header for an HTTPAuth request."""
        auth_header = 'OAuth realm="%s"' % realm
        # Add the oauth parameters.
        if self.parameters:
            for k, v in self.parameters.iteritems():
                if k[:6] == 'oauth_':
                    auth_header += ', %s="%s"' % (k, escape(str(v)))
        return {'Authorization': auth_header}

    def to_postdata(self):
        """Serialize as post data for a POST request."""
        return '&'.join(['%s=%s' % (escape(str(k)), escape(str(v))) \
            for k, v in self.parameters.iteritems()])

    def to_url(self):
        """Serialize as a URL for a GET request."""
        return '%s?%s' % (self.get_normalized_http_url(), self.to_postdata())

    def get_normalized_parameters(self):
        """Return a string that contains the parameters that must be signed."""
        params = self.parameters
        try:
            # Exclude the signature if it exists.
            del params['oauth_signature']
        except:
            pass
        # Escape key values before sorting.
        key_values = [(_utf8_str(k), _utf8_str(v)) \
            for k,v in params.items()]
        # Sort lexicographically, first after key, then after value.
        key_values.sort()
        # Combine key value pairs into a string.
        return '&'.join(['%s=%s' % (k, v) for k, v in key_values])

    def get_normalized_http_method(self):
        """Uppercases the http method."""
        return self.http_method.upper()

    def get_normalized_http_url(self):
        """Parses the URL and rebuilds it to be scheme://host/path."""
        parts = urlparse.urlparse(self.http_url)
        scheme, netloc, path = parts[:3]
        # Exclude default port numbers.
        if scheme == 'http' and netloc[-3:] == ':80':
            netloc = netloc[:-3]
        elif scheme == 'https' and netloc[-4:] == ':443':
            netloc = netloc[:-4]
        return '%s://%s%s' % (scheme, netloc, path)

    def sign_request(self, signature_method, consumer, token):
        """Set the signature parameter to the result of build_signature."""
        # Set the signature method.
        self.set_parameter('oauth_signature_method',
            signature_method.get_name())
        # Set the signature.
        self.set_parameter('oauth_signature',
            self.build_signature(signature_method, consumer, token))

    def build_signature(self, signature_method, consumer, token):
        """Calls the build signature method within the signature method."""
        return signature_method.build_signature(self, consumer, token)

    def from_request(http_method, http_url, headers=None, parameters=None,
            query_string=None):
        """Combines multiple parameter sources."""
        if parameters is None:
            parameters = {}

        # Headers
        if headers and 'Authorization' in headers:
            auth_header = headers['Authorization']
            # Check that the authorization header is OAuth.
            if auth_header[:6] == 'OAuth ':
                auth_header = auth_header[6:]
                try:
                    # Get the parameters from the header.
                    header_params = OAuthRequest._split_header(auth_header)
                    parameters.update(header_params)
                except:
                    raise OAuthError('Unable to parse OAuth parameters from '
                        'Authorization header.')

        # GET or POST query string.
        if query_string:
            query_params = OAuthRequest._split_url_string(query_string)
            parameters.update(query_params)

        # URL parameters.
        param_str = urlparse.urlparse(http_url)[4] # query
        url_params = OAuthRequest._split_url_string(param_str)
        parameters.update(url_params)

        if parameters:
            return OAuthRequest(http_method, http_url, parameters)

        return None
    from_request = staticmethod(from_request)

    def from_consumer_and_token(oauth_consumer, token=None,
            callback=None, verifier=None, http_method=HTTP_METHOD,
            http_url=None, parameters=None):
        if not parameters:
            parameters = {}

        defaults = {
            'oauth_consumer_key': oauth_consumer.key,
            'oauth_timestamp': generate_timestamp(),
            'oauth_nonce': generate_nonce(),
            'oauth_version': OAuthRequest.version,
        }

        defaults.update(parameters)
        parameters = defaults

        if token:
            parameters['oauth_token'] = token.key
            if token.callback:
                parameters['oauth_callback'] = token.callback
            # 1.0a support for verifier.
            if verifier:
                parameters['oauth_verifier'] = verifier
        elif callback:
            # 1.0a support for callback in the request token request.
            parameters['oauth_callback'] = callback
        return OAuthRequest(http_method, http_url, parameters)
    from_consumer_and_token = staticmethod(from_consumer_and_token)

    def from_token_and_callback(token, callback=None, http_method=HTTP_METHOD,
            http_url=None, parameters=None):
        if not parameters:
            parameters = {}

        parameters['oauth_token'] = token.key

        if callback:
            parameters['oauth_callback'] = callback

        return OAuthRequest(http_method, http_url, parameters)
    from_token_and_callback = staticmethod(from_token_and_callback)

    def _split_header(header):
        """Turn Authorization: header into parameters."""
        params = {}
        parts = header.split(',')
        for param in parts:
            # Ignore realm parameter.
            if param.find('realm') > -1:
                continue
            # Remove whitespace.
            param = param.strip()
            # Split key-value.
            param_parts = param.split('=', 1)
            # Remove quotes and unescape the value.
            params[param_parts[0]] = urllib.unquote(param_parts[1].strip('\"'))
        return params
    _split_header = staticmethod(_split_header)

    def _split_url_string(param_str):
        """Turn URL string into parameters."""
        parameters = cgi.parse_qs(param_str, keep_blank_values=False)
        for k, v in parameters.iteritems():
            parameters[k] = urllib.unquote(v[0])
        return parameters
    _split_url_string = staticmethod(_split_url_string)

class OAuthServer(object):
    """A worker to check the validity of a request against a data store."""
    timestamp_threshold = 300 # In seconds, five minutes.
    version = VERSION
    signature_methods = None
    data_store = None

    def __init__(self, data_store=None, signature_methods=None):
        self.data_store = data_store
        self.signature_methods = signature_methods or {}

    def set_data_store(self, data_store):
        self.data_store = data_store

    def get_data_store(self):
        return self.data_store

    def add_signature_method(self, signature_method):
        self.signature_methods[signature_method.get_name()] = signature_method
        return self.signature_methods

    def fetch_request_token(self, oauth_request):
        """Processes a request_token request and returns the
        request token on success.
        """
        try:
            # Get the request token for authorization.
            token = self._get_token(oauth_request, 'request')
        except OAuthError:
            # No token required for the initial token request.
            version = self._get_version(oauth_request)
            consumer = self._get_consumer(oauth_request)
            try:
                callback = self.get_callback(oauth_request)
            except OAuthError:
                callback = None # 1.0, no callback specified.
            self._check_signature(oauth_request, consumer, None)
            # Fetch a new token.
            token = self.data_store.fetch_request_token(consumer, callback)
        return token

    def fetch_access_token(self, oauth_request):
        """Processes an access_token request and returns the
        access token on success.
        """
        version = self._get_version(oauth_request)
        consumer = self._get_consumer(oauth_request)
        try:
            verifier = self._get_verifier(oauth_request)
        except OAuthError:
            verifier = None
        # Get the request token.
        token = self._get_token(oauth_request, 'request')
        self._check_signature(oauth_request, consumer, token)
        new_token = self.data_store.fetch_access_token(consumer, token, verifier)
        return new_token

    def verify_request(self, oauth_request):
        """Verifies an api call and checks all the parameters."""
        # -> consumer and token
        version = self._get_version(oauth_request)
        consumer = self._get_consumer(oauth_request)
        # Get the access token.
        token = self._get_token(oauth_request, 'access')
        self._check_signature(oauth_request, consumer, token)
        parameters = oauth_request.get_nonoauth_parameters()
        return consumer, token, parameters

    def authorize_token(self, token, user):
        """Authorize a request token."""
        return self.data_store.authorize_request_token(token, user)

    def get_callback(self, oauth_request):
        """Get the callback URL."""
        return oauth_request.get_parameter('oauth_callback')

    def build_authenticate_header(self, realm=''):
        """Optional support for the authenticate header."""
        return {'WWW-Authenticate': 'OAuth realm="%s"' % realm}

    def _get_version(self, oauth_request):
        """Verify the correct version request for this server."""
        try:
            version = oauth_request.get_parameter('oauth_version')
        except:
            version = VERSION
        if version and version != self.version:
            raise OAuthError('OAuth version %s not supported.' % str(version))
        return version

    def _get_signature_method(self, oauth_request):
        """Figure out the signature with some defaults."""
        try:
            signature_method = oauth_request.get_parameter(
                'oauth_signature_method')
        except:
            signature_method = SIGNATURE_METHOD
        try:
            # Get the signature method object.
            signature_method = self.signature_methods[signature_method]
        except:
            signature_method_names = ', '.join(self.signature_methods.keys())
            raise OAuthError('Signature method %s not supported try one of the '
                'following: %s' % (signature_method, signature_method_names))

        return signature_method

    def _get_consumer(self, oauth_request):
        consumer_key = oauth_request.get_parameter('oauth_consumer_key')
        consumer = self.data_store.lookup_consumer(consumer_key)
        if not consumer:
            raise OAuthError('Invalid consumer.')
        return consumer

    def _get_token(self, oauth_request, token_type='access'):
        """Try to find the token for the provided request token key."""
        token_field = oauth_request.get_parameter('oauth_token')
        token = self.data_store.lookup_token(token_type, token_field)
        if not token:
            raise OAuthError('Invalid %s token: %s' % (token_type, token_field))
        return token

    def _get_verifier(self, oauth_request):
        return oauth_request.get_parameter('oauth_verifier')

    def _check_signature(self, oauth_request, consumer, token):
        timestamp, nonce = oauth_request._get_timestamp_nonce()
        self._check_timestamp(timestamp)
        self._check_nonce(consumer, token, nonce)
        signature_method = self._get_signature_method(oauth_request)
        try:
            signature = oauth_request.get_parameter('oauth_signature')
        except:
            raise OAuthError('Missing signature.')
        # Validate the signature.
        valid_sig = signature_method.check_signature(oauth_request, consumer,
            token, signature)
        if not valid_sig:
            key, base = signature_method.build_signature_base_string(
                oauth_request, consumer, token)
            raise OAuthError('Invalid signature. Expected signature base '
                'string: %s' % base)
        built = signature_method.build_signature(oauth_request, consumer, token)

    def _check_timestamp(self, timestamp):
        """Verify that timestamp is recentish."""
        timestamp = int(timestamp)
        now = int(time.time())
        lapsed = abs(now - timestamp)
        if lapsed > self.timestamp_threshold:
            raise OAuthError('Expired timestamp: given %d and now %s has a '
                'greater difference than threshold %d' %
                (timestamp, now, self.timestamp_threshold))

    def _check_nonce(self, consumer, token, nonce):
        """Verify that the nonce is uniqueish."""
        nonce = self.data_store.lookup_nonce(consumer, token, nonce)
        if nonce:
            raise OAuthError('Nonce already used: %s' % str(nonce))


class OAuthClient(object):
    """OAuthClient is a worker to attempt to execute a request."""
    consumer = None
    token = None

    def __init__(self, oauth_consumer, oauth_token):
        self.consumer = oauth_consumer
        self.token = oauth_token

    def get_consumer(self):
        return self.consumer

    def get_token(self):
        return self.token

    def fetch_request_token(self, oauth_request):
        """-> OAuthToken."""
        raise NotImplementedError

    def fetch_access_token(self, oauth_request):
        """-> OAuthToken."""
        raise NotImplementedError

    def access_resource(self, oauth_request):
        """-> Some protected resource."""
        raise NotImplementedError


class OAuthDataStore(object):
    """A database abstraction used to lookup consumers and tokens."""

    def lookup_consumer(self, key):
        """-> OAuthConsumer."""
        raise NotImplementedError

    def lookup_token(self, oauth_consumer, token_type, token_token):
        """-> OAuthToken."""
        raise NotImplementedError

    def lookup_nonce(self, oauth_consumer, oauth_token, nonce):
        """-> OAuthToken."""
        raise NotImplementedError

    def fetch_request_token(self, oauth_consumer, oauth_callback):
        """-> OAuthToken."""
        raise NotImplementedError

    def fetch_access_token(self, oauth_consumer, oauth_token, oauth_verifier):
        """-> OAuthToken."""
        raise NotImplementedError

    def authorize_request_token(self, oauth_token, user):
        """-> OAuthToken."""
        raise NotImplementedError


class OAuthSignatureMethod(object):
    """A strategy class that implements a signature method."""
    def get_name(self):
        """-> str."""
        raise NotImplementedError

    def build_signature_base_string(self, oauth_request, oauth_consumer, oauth_token):
        """-> str key, str raw."""
        raise NotImplementedError

    def build_signature(self, oauth_request, oauth_consumer, oauth_token):
        """-> str."""
        raise NotImplementedError

    def check_signature(self, oauth_request, consumer, token, signature):
        built = self.build_signature(oauth_request, consumer, token)
        return built == signature


class OAuthSignatureMethod_HMAC_SHA1(OAuthSignatureMethod):

    def get_name(self):
        return 'HMAC-SHA1'

    def build_signature_base_string(self, oauth_request, consumer, token):
        sig = (
            escape(oauth_request.get_normalized_http_method()),
            escape(oauth_request.get_normalized_http_url()),
            escape(oauth_request.get_normalized_parameters()),
        )

        key = '%s&' % escape(consumer.secret)
        if token:
            key += escape(token.secret)
        raw = '&'.join(sig)
        return key, raw

    def build_signature(self, oauth_request, consumer, token):
        """Builds the base signature string."""
        key, raw = self.build_signature_base_string(oauth_request, consumer,
            token)
        # HMAC object.
        try:
            import hashlib # 2.5
            hashed = hmac.new(key, raw, hashlib.sha1)
        except:
            import sha # Deprecated
            hashed = hmac.new(key, raw, sha)

        # Calculate the digest base 64.
        return binascii.b2a_base64(hashed.digest())[:-1]


class OAuthSignatureMethod_PLAINTEXT(OAuthSignatureMethod):

    def get_name(self):
        return 'PLAINTEXT'

    def build_signature_base_string(self, oauth_request, consumer, token):
        """Concatenates the consumer key and secret."""
        sig = '%s&' % escape(consumer.secret)
        if token:
            sig = sig + escape(token.secret)
        return sig, sig

    def build_signature(self, oauth_request, consumer, token):
        key, raw = self.build_signature_base_string(oauth_request, consumer,
            token)
        return key

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