Skip to content
This repository
Fetching contributors…

Cannot retrieve contributors at this time

file 684 lines (580 sloc) 26.275 kb
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684
# Copyright 2010 Google Inc.
# Copyright (c) 2011 Mitch Garnaat http://garnaat.org/
# Copyright (c) 2011, Eucalyptus Systems, Inc.
#
# 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, dis-
# tribute, sublicense, and/or sell copies of the Software, and to permit
# persons to whom the Software is furnished to do so, subject to the fol-
# lowing 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 MERCHANTABIL-
# ITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
# SHALL THE AUTHOR 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.


"""
Handles authentication required to AWS and GS
"""

import base64
import boto
import boto.auth_handler
import boto.exception
import boto.plugin
import boto.utils
import hmac
import sys
import urllib
import time
import datetime
import copy
from email.utils import formatdate

from boto.auth_handler import AuthHandler
from boto.exception import BotoClientError
#
# the following is necessary because of the incompatibilities
# between Python 2.4, 2.5, and 2.6 as well as the fact that some
# people running 2.4 have installed hashlib as a separate module
# this fix was provided by boto user mccormix.
# see: http://code.google.com/p/boto/issues/detail?id=172
# for more details.
#
try:
    from hashlib import sha1 as sha
    from hashlib import sha256 as sha256

    if sys.version[:3] == "2.4":
        # we are using an hmac that expects a .new() method.
        class Faker:
            def __init__(self, which):
                self.which = which
                self.digest_size = self.which().digest_size

            def new(self, *args, **kwargs):
                return self.which(*args, **kwargs)

        sha = Faker(sha)
        sha256 = Faker(sha256)

except ImportError:
    import sha
    sha256 = None


class HmacKeys(object):
    """Key based Auth handler helper."""

    def __init__(self, host, config, provider):
        if provider.access_key is None or provider.secret_key is None:
            raise boto.auth_handler.NotReadyToAuthenticate()
        self.host = host
        self.update_provider(provider)

    def update_provider(self, provider):
        self._provider = provider
        self._hmac = hmac.new(self._provider.secret_key, digestmod=sha)
        if sha256:
            self._hmac_256 = hmac.new(self._provider.secret_key,
                                      digestmod=sha256)
        else:
            self._hmac_256 = None

    def algorithm(self):
        if self._hmac_256:
            return 'HmacSHA256'
        else:
            return 'HmacSHA1'

    def _get_hmac(self):
        if self._hmac_256:
            digestmod = sha256
        else:
            digestmod = sha
        return hmac.new(self._provider.secret_key,
                        digestmod=digestmod)

    def sign_string(self, string_to_sign):
        new_hmac = self._get_hmac()
        new_hmac.update(string_to_sign)
        return base64.encodestring(new_hmac.digest()).strip()

    def __getstate__(self):
        pickled_dict = copy.copy(self.__dict__)
        del pickled_dict['_hmac']
        del pickled_dict['_hmac_256']
        return pickled_dict

    def __setstate__(self, dct):
        self.__dict__ = dct
        self.update_provider(self._provider)


class AnonAuthHandler(AuthHandler, HmacKeys):
    """
Implements Anonymous requests.
"""

    capability = ['anon']

    def __init__(self, host, config, provider):
        AuthHandler.__init__(self, host, config, provider)

    def add_auth(self, http_request, **kwargs):
        pass


class HmacAuthV1Handler(AuthHandler, HmacKeys):
    """ Implements the HMAC request signing used by S3 and GS."""

    capability = ['hmac-v1', 's3']

    def __init__(self, host, config, provider):
        AuthHandler.__init__(self, host, config, provider)
        HmacKeys.__init__(self, host, config, provider)
        self._hmac_256 = None

    def update_provider(self, provider):
        super(HmacAuthV1Handler, self).update_provider(provider)
        self._hmac_256 = None

    def add_auth(self, http_request, **kwargs):
        headers = http_request.headers
        method = http_request.method
        auth_path = http_request.auth_path
        if 'Date' not in headers:
            headers['Date'] = formatdate(usegmt=True)

        if self._provider.security_token:
            key = self._provider.security_token_header
            headers[key] = self._provider.security_token
        string_to_sign = boto.utils.canonical_string(method, auth_path,
                                                     headers, None,
                                                     self._provider)
        boto.log.debug('StringToSign:\n%s' % string_to_sign)
        b64_hmac = self.sign_string(string_to_sign)
        auth_hdr = self._provider.auth_header
        headers['Authorization'] = ("%s %s:%s" %
                                    (auth_hdr,
                                     self._provider.access_key, b64_hmac))


class HmacAuthV2Handler(AuthHandler, HmacKeys):
    """
Implements the simplified HMAC authorization used by CloudFront.
"""
    capability = ['hmac-v2', 'cloudfront']

    def __init__(self, host, config, provider):
        AuthHandler.__init__(self, host, config, provider)
        HmacKeys.__init__(self, host, config, provider)
        self._hmac_256 = None

    def update_provider(self, provider):
        super(HmacAuthV2Handler, self).update_provider(provider)
        self._hmac_256 = None

    def add_auth(self, http_request, **kwargs):
        headers = http_request.headers
        if 'Date' not in headers:
            headers['Date'] = formatdate(usegmt=True)

        b64_hmac = self.sign_string(headers['Date'])
        auth_hdr = self._provider.auth_header
        headers['Authorization'] = ("%s %s:%s" %
                                    (auth_hdr,
                                     self._provider.access_key, b64_hmac))


class HmacAuthV3Handler(AuthHandler, HmacKeys):
    """Implements the new Version 3 HMAC authorization used by Route53."""

    capability = ['hmac-v3', 'route53', 'ses']

    def __init__(self, host, config, provider):
        AuthHandler.__init__(self, host, config, provider)
        HmacKeys.__init__(self, host, config, provider)

    def add_auth(self, http_request, **kwargs):
        headers = http_request.headers
        if 'Date' not in headers:
            headers['Date'] = formatdate(usegmt=True)

        if self._provider.security_token:
            key = self._provider.security_token_header
            headers[key] = self._provider.security_token

        b64_hmac = self.sign_string(headers['Date'])
        s = "AWS3-HTTPS AWSAccessKeyId=%s," % self._provider.access_key
        s += "Algorithm=%s,Signature=%s" % (self.algorithm(), b64_hmac)
        headers['X-Amzn-Authorization'] = s


class HmacAuthV3HTTPHandler(AuthHandler, HmacKeys):
    """
Implements the new Version 3 HMAC authorization used by DynamoDB.
"""

    capability = ['hmac-v3-http']

    def __init__(self, host, config, provider):
        AuthHandler.__init__(self, host, config, provider)
        HmacKeys.__init__(self, host, config, provider)

    def headers_to_sign(self, http_request):
        """
Select the headers from the request that need to be included
in the StringToSign.
"""
        headers_to_sign = {}
        headers_to_sign = {'Host': self.host}
        for name, value in http_request.headers.items():
            lname = name.lower()
            if lname.startswith('x-amz'):
                headers_to_sign[name] = value
        return headers_to_sign

    def canonical_headers(self, headers_to_sign):
        """
Return the headers that need to be included in the StringToSign
in their canonical form by converting all header keys to lower
case, sorting them in alphabetical order and then joining
them into a string, separated by newlines.
"""
        l = sorted(['%s:%s' % (n.lower().strip(),
                    headers_to_sign[n].strip()) for n in headers_to_sign])
        return '\n'.join(l)

    def string_to_sign(self, http_request):
        """
Return the canonical StringToSign as well as a dict
containing the original version of all headers that
were included in the StringToSign.
"""
        headers_to_sign = self.headers_to_sign(http_request)
        canonical_headers = self.canonical_headers(headers_to_sign)
        string_to_sign = '\n'.join([http_request.method,
                                    http_request.auth_path,
                                    '',
                                    canonical_headers,
                                    '',
                                    http_request.body])
        return string_to_sign, headers_to_sign

    def add_auth(self, req, **kwargs):
        """
Add AWS3 authentication to a request.

:type req: :class`boto.connection.HTTPRequest`
:param req: The HTTPRequest object.
"""
        # This could be a retry. Make sure the previous
        # authorization header is removed first.
        if 'X-Amzn-Authorization' in req.headers:
            del req.headers['X-Amzn-Authorization']
        req.headers['X-Amz-Date'] = formatdate(usegmt=True)
        if self._provider.security_token:
            req.headers['X-Amz-Security-Token'] = self._provider.security_token
        string_to_sign, headers_to_sign = self.string_to_sign(req)
        boto.log.debug('StringToSign:\n%s' % string_to_sign)
        hash_value = sha256(string_to_sign).digest()
        b64_hmac = self.sign_string(hash_value)
        s = "AWS3 AWSAccessKeyId=%s," % self._provider.access_key
        s += "Algorithm=%s," % self.algorithm()
        s += "SignedHeaders=%s," % ';'.join(headers_to_sign)
        s += "Signature=%s" % b64_hmac
        req.headers['X-Amzn-Authorization'] = s


class HmacAuthV4Handler(AuthHandler, HmacKeys):
    """
Implements the new Version 4 HMAC authorization.
"""

    capability = ['hmac-v4']

    def __init__(self, host, config, provider,
                 service_name=None, region_name=None):
        AuthHandler.__init__(self, host, config, provider)
        HmacKeys.__init__(self, host, config, provider)
        # You can set the service_name and region_name to override the
        # values which would otherwise come from the endpoint, e.g.
        # <service>.<region>.amazonaws.com.
        self.service_name = service_name
        self.region_name = region_name

    def _sign(self, key, msg, hex=False):
        if hex:
            sig = hmac.new(key, msg.encode('utf-8'), sha256).hexdigest()
        else:
            sig = hmac.new(key, msg.encode('utf-8'), sha256).digest()
        return sig

    def headers_to_sign(self, http_request):
        """
Select the headers from the request that need to be included
in the StringToSign.
"""
        headers_to_sign = {}
        headers_to_sign = {'Host': self.host}
        for name, value in http_request.headers.items():
            lname = name.lower()
            if lname.startswith('x-amz'):
                headers_to_sign[name] = value
        return headers_to_sign

    def query_string(self, http_request):
        parameter_names = sorted(http_request.params.keys())
        pairs = []
        for pname in parameter_names:
            pval = str(http_request.params[pname]).encode('utf-8')
            pairs.append(urllib.quote(pname, safe='') + '=' +
                         urllib.quote(pval, safe='-_~'))
        return '&'.join(pairs)

    def canonical_query_string(self, http_request):
        # POST requests pass parameters in through the
        # http_request.body field.
        if http_request.method == 'POST':
            return ""
        l = []
        for param in sorted(http_request.params):
            value = str(http_request.params[param])
            l.append('%s=%s' % (urllib.quote(param, safe='-_.~'),
                                urllib.quote(value, safe='-_.~')))
        return '&'.join(l)

    def canonical_headers(self, headers_to_sign):
        """
Return the headers that need to be included in the StringToSign
in their canonical form by converting all header keys to lower
case, sorting them in alphabetical order and then joining
them into a string, separated by newlines.
"""
        l = sorted(['%s:%s' % (n.lower().strip(),
                    ' '.join(headers_to_sign[n].strip().split()))
                    for n in headers_to_sign])
        return '\n'.join(l)

    def signed_headers(self, headers_to_sign):
        l = ['%s' % n.lower().strip() for n in headers_to_sign]
        l = sorted(l)
        return ';'.join(l)

    def canonical_uri(self, http_request):
        return http_request.auth_path

    def payload(self, http_request):
        body = http_request.body
        # If the body is a file like object, we can use
        # boto.utils.compute_hash, which will avoid reading
        # the entire body into memory.
        if hasattr(body, 'seek') and hasattr(body, 'read'):
            return boto.utils.compute_hash(body, hash_algorithm=sha256)[0]
        return sha256(http_request.body).hexdigest()

    def canonical_request(self, http_request):
        cr = [http_request.method.upper()]
        cr.append(self.canonical_uri(http_request))
        cr.append(self.canonical_query_string(http_request))
        headers_to_sign = self.headers_to_sign(http_request)
        cr.append(self.canonical_headers(headers_to_sign) + '\n')
        cr.append(self.signed_headers(headers_to_sign))
        cr.append(self.payload(http_request))
        return '\n'.join(cr)

    def scope(self, http_request):
        scope = [self._provider.access_key]
        scope.append(http_request.timestamp)
        scope.append(http_request.region_name)
        scope.append(http_request.service_name)
        scope.append('aws4_request')
        return '/'.join(scope)

    def credential_scope(self, http_request):
        scope = []
        http_request.timestamp = http_request.headers['X-Amz-Date'][0:8]
        scope.append(http_request.timestamp)
        # The service_name and region_name either come from:
        # * The service_name/region_name attrs or (if these values are None)
        # * parsed from the endpoint <service>.<region>.amazonaws.com.
        parts = http_request.host.split('.')
        if self.region_name is not None:
            region_name = self.region_name
        else:
            if len(parts) == 3:
                region_name = 'us-east-1'
            else:
                region_name = parts[1]
        if self.service_name is not None:
            service_name = self.service_name
        else:
            service_name = parts[0]

        http_request.service_name = service_name
        http_request.region_name = region_name

        scope.append(http_request.region_name)
        scope.append(http_request.service_name)
        scope.append('aws4_request')
        return '/'.join(scope)

    def string_to_sign(self, http_request, canonical_request):
        """
Return the canonical StringToSign as well as a dict
containing the original version of all headers that
were included in the StringToSign.
"""
        sts = ['AWS4-HMAC-SHA256']
        sts.append(http_request.headers['X-Amz-Date'])
        sts.append(self.credential_scope(http_request))
        sts.append(sha256(canonical_request).hexdigest())
        return '\n'.join(sts)

    def signature(self, http_request, string_to_sign):
        key = self._provider.secret_key
        k_date = self._sign(('AWS4' + key).encode('utf-8'),
                              http_request.timestamp)
        k_region = self._sign(k_date, http_request.region_name)
        k_service = self._sign(k_region, http_request.service_name)
        k_signing = self._sign(k_service, 'aws4_request')
        return self._sign(k_signing, string_to_sign, hex=True)

    def add_auth(self, req, **kwargs):
        """
Add AWS4 authentication to a request.

:type req: :class`boto.connection.HTTPRequest`
:param req: The HTTPRequest object.
"""
        # This could be a retry. Make sure the previous
        # authorization header is removed first.
        if 'X-Amzn-Authorization' in req.headers:
            del req.headers['X-Amzn-Authorization']
        now = datetime.datetime.utcnow()
        req.headers['X-Amz-Date'] = now.strftime('%Y%m%dT%H%M%SZ')
        if self._provider.security_token:
            req.headers['X-Amz-Security-Token'] = self._provider.security_token
        qs = self.query_string(req)
        if qs and req.method == 'POST':
            # Stash request parameters into post body
            # before we generate the signature.
            req.body = qs
            req.headers['Content-Type'] = 'application/x-www-form-urlencoded; charset=UTF-8'
            req.headers['Content-Length'] = str(len(req.body))
        else:
            # Safe to modify req.path here since
            # the signature will use req.auth_path.
            req.path = req.path.split('?')[0]
            req.path = req.path + '?' + qs
        canonical_request = self.canonical_request(req)
        boto.log.debug('CanonicalRequest:\n%s' % canonical_request)
        string_to_sign = self.string_to_sign(req, canonical_request)
        boto.log.debug('StringToSign:\n%s' % string_to_sign)
        signature = self.signature(req, string_to_sign)
        boto.log.debug('Signature:\n%s' % signature)
        headers_to_sign = self.headers_to_sign(req)
        l = ['AWS4-HMAC-SHA256 Credential=%s' % self.scope(req)]
        l.append('SignedHeaders=%s' % self.signed_headers(headers_to_sign))
        l.append('Signature=%s' % signature)
        req.headers['Authorization'] = ','.join(l)


class QuerySignatureHelper(HmacKeys):
    """
Helper for Query signature based Auth handler.

Concrete sub class need to implement _calc_sigature method.
"""

    def add_auth(self, http_request, **kwargs):
        headers = http_request.headers
        params = http_request.params
        params['AWSAccessKeyId'] = self._provider.access_key
        params['SignatureVersion'] = self.SignatureVersion
        params['Timestamp'] = boto.utils.get_ts()
        qs, signature = self._calc_signature(
            http_request.params, http_request.method,
            http_request.auth_path, http_request.host)
        boto.log.debug('query_string: %s Signature: %s' % (qs, signature))
        if http_request.method == 'POST':
            headers['Content-Type'] = 'application/x-www-form-urlencoded; charset=UTF-8'
            http_request.body = qs + '&Signature=' + urllib.quote_plus(signature)
            http_request.headers['Content-Length'] = str(len(http_request.body))
        else:
            http_request.body = ''
            # if this is a retried request, the qs from the previous try will
            # already be there, we need to get rid of that and rebuild it
            http_request.path = http_request.path.split('?')[0]
            http_request.path = (http_request.path + '?' + qs +
                                 '&Signature=' + urllib.quote_plus(signature))


class QuerySignatureV0AuthHandler(QuerySignatureHelper, AuthHandler):
    """Provides Signature V0 Signing"""

    SignatureVersion = 0
    capability = ['sign-v0']

    def _calc_signature(self, params, *args):
        boto.log.debug('using _calc_signature_0')
        hmac = self._get_hmac()
        s = params['Action'] + params['Timestamp']
        hmac.update(s)
        keys = params.keys()
        keys.sort(cmp=lambda x, y: cmp(x.lower(), y.lower()))
        pairs = []
        for key in keys:
            val = boto.utils.get_utf8_value(params[key])
            pairs.append(key + '=' + urllib.quote(val))
        qs = '&'.join(pairs)
        return (qs, base64.b64encode(hmac.digest()))


class QuerySignatureV1AuthHandler(QuerySignatureHelper, AuthHandler):
    """
Provides Query Signature V1 Authentication.
"""

    SignatureVersion = 1
    capability = ['sign-v1', 'mturk']

    def __init__(self, *args, **kw):
        QuerySignatureHelper.__init__(self, *args, **kw)
        AuthHandler.__init__(self, *args, **kw)
        self._hmac_256 = None

    def _calc_signature(self, params, *args):
        boto.log.debug('using _calc_signature_1')
        hmac = self._get_hmac()
        keys = params.keys()
        keys.sort(cmp=lambda x, y: cmp(x.lower(), y.lower()))
        pairs = []
        for key in keys:
            hmac.update(key)
            val = boto.utils.get_utf8_value(params[key])
            hmac.update(val)
            pairs.append(key + '=' + urllib.quote(val))
        qs = '&'.join(pairs)
        return (qs, base64.b64encode(hmac.digest()))


class QuerySignatureV2AuthHandler(QuerySignatureHelper, AuthHandler):
    """Provides Query Signature V2 Authentication."""

    SignatureVersion = 2
    capability = ['sign-v2', 'ec2', 'ec2', 'emr', 'fps', 'ecs',
                  'sdb', 'iam', 'rds', 'sns', 'sqs', 'cloudformation']

    def _calc_signature(self, params, verb, path, server_name):
        boto.log.debug('using _calc_signature_2')
        string_to_sign = '%s\n%s\n%s\n' % (verb, server_name.lower(), path)
        hmac = self._get_hmac()
        params['SignatureMethod'] = self.algorithm()
        if self._provider.security_token:
            params['SecurityToken'] = self._provider.security_token
        keys = sorted(params.keys())
        pairs = []
        for key in keys:
            val = boto.utils.get_utf8_value(params[key])
            pairs.append(urllib.quote(key, safe='') + '=' +
                         urllib.quote(val, safe='-_~'))
        qs = '&'.join(pairs)
        boto.log.debug('query string: %s' % qs)
        string_to_sign += qs
        boto.log.debug('string_to_sign: %s' % string_to_sign)
        hmac.update(string_to_sign)
        b64 = base64.b64encode(hmac.digest())
        boto.log.debug('len(b64)=%d' % len(b64))
        boto.log.debug('base64 encoded digest: %s' % b64)
        return (qs, b64)


class POSTPathQSV2AuthHandler(QuerySignatureV2AuthHandler, AuthHandler):
    """
Query Signature V2 Authentication relocating signed query
into the path and allowing POST requests with Content-Types.
"""

    capability = ['mws']

    def add_auth(self, req, **kwargs):
        req.params['AWSAccessKeyId'] = self._provider.access_key
        req.params['SignatureVersion'] = self.SignatureVersion
        req.params['Timestamp'] = boto.utils.get_ts()
        qs, signature = self._calc_signature(req.params, req.method,
                                             req.auth_path, req.host)
        boto.log.debug('query_string: %s Signature: %s' % (qs, signature))
        if req.method == 'POST':
            req.headers['Content-Length'] = str(len(req.body))
            req.headers['Content-Type'] = req.headers.get('Content-Type',
                                                          'text/plain')
        else:
            req.body = ''
        # if this is a retried req, the qs from the previous try will
        # already be there, we need to get rid of that and rebuild it
        req.path = req.path.split('?')[0]
        req.path = (req.path + '?' + qs +
                             '&Signature=' + urllib.quote_plus(signature))


def get_auth_handler(host, config, provider, requested_capability=None):
    """Finds an AuthHandler that is ready to authenticate.

Lists through all the registered AuthHandlers to find one that is willing
to handle for the requested capabilities, config and provider.

:type host: string
:param host: The name of the host

:type config:
:param config:

:type provider:
:param provider:

Returns:
An implementation of AuthHandler.

Raises:
boto.exception.NoAuthHandlerFound:
boto.exception.TooManyAuthHandlerReadyToAuthenticate:
"""
    ready_handlers = []
    auth_handlers = boto.plugin.get_plugin(AuthHandler, requested_capability)
    total_handlers = len(auth_handlers)
    for handler in auth_handlers:
        try:
            ready_handlers.append(handler(host, config, provider))
        except boto.auth_handler.NotReadyToAuthenticate:
            pass

    if not ready_handlers:
        checked_handlers = auth_handlers
        names = [handler.__name__ for handler in checked_handlers]
        raise boto.exception.NoAuthHandlerFound(
              'No handler was ready to authenticate. %d handlers were checked.'
              ' %s '
              'Check your credentials' % (len(names), str(names)))

    if len(ready_handlers) > 1:
        # NOTE: Even though it would be nice to accept more than one handler
        # by using one of the many ready handlers, we are never sure that each
        # of them are referring to the same storage account. Since we cannot
        # easily guarantee that, it is always safe to fail, rather than operate
        # on the wrong account.
        names = [handler.__class__.__name__ for handler in ready_handlers]
        raise boto.exception.TooManyAuthHandlerReadyToAuthenticate(
               '%d AuthHandlers %s ready to authenticate for requested_capability '
               '%s, only 1 expected. This happens if you import multiple '
               'pluging.Plugin implementations that declare support for the '
               'requested_capability.' % (len(names), str(names),
               requested_capability))

    return ready_handlers[0]
Something went wrong with that request. Please try again.