AWS4 authentication for Requests
Amazon Web Services version 4 authentication for the Python Requests library.
- Requests authentication for all AWS services that support AWS auth v4
- Independent signing key objects
- Automatic regeneration of keys when scope date boundary is passed
- Support for STS temporary credentials
Implements header-based authentication, GET URL parameter and POST parameter authentication are not supported.
This package has been tested as working against:
AppStream, Auto-Scaling, CloudFormation, CloudFront, CloudHSM, CloudSearch, CloudTrail, CloudWatch Monitoring, CloudWatch Logs, CodeDeploy, Cognito Identity, Cognito Sync, Config, DataPipeline, Direct Connect, DynamoDB, Elastic Beanstalk, ElastiCache, EC2, EC2 Container Service, Elastic Load Balancing, Elastic MapReduce, ElasticSearch, Elastic Transcoder, Glacier, Identity and Access Management (IAM), Key Management Service (KMS), Kinesis, Lambda, Opsworks, Redshift, Relational Database Service (RDS), Route 53, Simple Storage Service (S3), Simple Notification Service (SNS), Simple Queue Service (SQS), Storage Gateway, Security Token Service (STS)
The following services do not support AWS auth version 4 and are not usable with this package:
Simple Email Service (SES), Simple Workflow Service (SWF), Import/Export, SimpleDB, DevPay, Mechanical Turk
The AWS Support API has not been tested as it requires a premium subscription.
Install via pip:
$ pip install requests-aws4auth
requests-aws4auth requires the Requests library by Kenneth Reitz.
requests-aws4auth is tested on Python 2.7 and 3.3 and up.
Behaviour changes in 0.8
Version 0.8 introduces request date checking and automatic key regeneration behaviour as default. This has implications for sharing authentication objects between threads, and for storage of secret keys. See the relevant sections below for details. See also the discussion in GitHub issue #10.
>>> import requests >>> from requests_aws4auth import AWS4Auth >>> endpoint = 'http://s3-eu-west-1.amazonaws.com' >>> auth = AWS4Auth('<ACCESS ID>', '<ACCESS KEY>', 'eu-west-1', 's3') >>> response = requests.get(endpoint, auth=auth) >>> response.text <?xml version="1.0" encoding="UTF-8"?> <ListAllMyBucketsResult xmlns="http://s3.amazonaws.com/doc/2006-03-01"> <Owner> <ID>bcaf1ffd86f461ca5fb16fd081034f</ID> <DisplayName>webfile</DisplayName> ...
This example would list your buckets in the eu-west-1 region of the Amazon S3 service.
STS Temporary Credentials
>>> from requests_aws4auth import AWS4Auth >>> auth = AWS4Auth('<ACCESS ID>', '<ACCESS KEY>', 'eu-west-1', 's3', session_token='<SESSION TOKEN>') ...
This example shows how to construct an AWS4Auth object for use with STS temporary credentials. The x-amz-security-token header is added with the session token. Temporary credential timeouts are not managed – in case the temporary credentials expire, they need to be re-generated and the AWS4Auth object re-constructed with the new credentials.
If an HTTP request to be authenticated contains a Date or X-Amz-Date header, AWS will only accept the authorised request if the date in the header matches the scope date of the signing key (see the AWS REST API date docs).
>From version 0.8 of requests-aws4auth, if the header date does not match the scope date, an AWS4Auth instance will automatically regenerate its signing key, using the same scope parameters as the previous key except for the date, which will be changed to match the request date. If a request does not include a date, the current date is added to the request in an X-Amz-Date header, and the signing key is regenerated if this differs from the scope date.
This means that AWS4Auth now extracts and parses dates from the values of X-Amz-Date and Date headers. Supported date formats are:
- RFC 7231 (e.g. Mon, 09 Sep 2011 23:36:00 GMT)
- RFC 850 (e.g. Sunday, 06-Nov-94 08:49:37 GMT)
- C time (e.g. Wed Dec 4 00:00:00 2002)
- Amz-Date format (e.g. 20090325T010101Z)
- ISO 8601 / RFC 3339 (e.g. 2009-03-25T10:11:12.13-01:00)
If either header is present but AWS4Auth cannot extract a date because all present date headers are in an unrecognisable format, AWS4Auth will delete any X-Amz-Date and Date headers present and replace with a single X-Amz-Date header containing the current date. This behaviour can be modified using the raise_invalid_date keyword argument of the AWS4Auth constructor.
Automatic key regeneration
If you do not want the signing key to be automatically regenerated when a mismatch between the request date and the scope date is encountered, use the alternative StrictAWS4Auth class, which is identical to AWS4Auth except that upon encountering a date mismatch it just raises a DateMismatchError. You can also use the PassiveAWS4Auth class, which mimics the AWS4Auth behaviour prior to version 0.8 and just signs and sends the request, whether the date matches or not. In this case it is up to the calling code to handle an authentication failure response from AWS caused by the date mismatch.
Secret key storage
To allow automatic key regeneration, the secret key is stored in the AWS4Auth instance, in the signing key object. If you do not want this to occur, instantiate the instance using an AWS4Signing key which was created with the store_secret_key parameter set to False:
>>> sig_key = AWS4SigningKey(secret_key, region, service, date, False) >>> auth = StrictAWS4Auth(access_id, sig_key)
The AWS4Auth class will then raise a NoSecretKeyError when it attempts to regenerate its key. A slightly more conceptually elegant way to handle this is to use the alternative StrictAWS4Auth class, again instantiating it with an AWS4SigningKey instance created with store_secret_key = False.
If you share AWS4Auth (or even StrictAWS4Auth) instances between threads you are likely to encounter problems. Because AWS4Auth instances may unpredictably regenerate their signing key as part of signing a request, threads using the same instance may find the key changed by another thread halfway through the signing process, which may result in undefined behaviour.
It may be possible to rig up a workable instance sharing mechanism using locking primitives and the StrictAWS4Auth class, however this poor author can’t think of a scenario which works safely yet doesn’t suffer from at some point blocking all threads for at least the duration of an HTTP request, which could be several seconds. If several requests come in in close succession which all require key regenerations then the system could be forced into serial operation for quite a length of time.
In short, it’s probably best to create a thread-local instance of AWS4Auth for each thread that needs to do authentication.
See the doctrings in aws4auth.py and aws4signingkey.py.
A test suite is included in the test folder.
The package passes all tests in the AWS auth v4 test_suite, and contains tests against the supported live services. See docstrings in test/requests_aws4auth_test.py for details about running the tests.
Connection parameters are included in the tests for the AWS Support API, should you have access and want to try it. The documentation says it supports auth v4 so it should work if you have a subscription. Do pass on your results!
Unsupported AWS features / todo
- Currently does not support Amazon S3 chunked uploads
- Tests for new AWS services
- Requires Requests library to be present even if only using AWS4SigningKey
- Coherent documentation
- Support for STS temporary credentials. Thanks to https://github.com/magdalene
- Tests for the STS temporary credentials functionality
- Fixed AWS4SigningKey.amz_date deprecation warning test
- Elastic MapReduce live service test no longer using deprecated DescribeJobFlows action
This version introduces some behaviour changes designed to reduce the legwork needed when a signing key goes out of date. This has implications for multithreading and secret key storage. See the README for further details.
- AWS4Auth class now checks request header date against signing key scope date, and automatically regenerates the signing key with the request date if they don’t match
- Added exceptions module with new exceptions: RequestsAWS4AuthException, DateMismatchError, NoSecretKeyError, DateFormatError
- Added StrictAWS4Auth and PassiveAWS4Auth classes
- Added regenerate_signing_key() method, to allow regeneration of current signing key with parameter overrides
- Added methods for checking and extracting dates from requests: get_request_date(), parse_date(), handle_date_mismatch()
- __call__() now checks for a date header in the request and attempts to automatically regenerate the signing key with the request date if request date differs from the signing key date
- Can now supply a date to the constructor
- Changed default included sig headers to include ‘Date’ header if present
- Added new store_secret_key instantiation parameter which allows control of whether the secret key is stored in the instance
- Deprecated the amz_date property in favour of just ‘date’
- Spelling typo fix in AWS4AuthSigningKey module docstring. Thanks to jhgorrell
- Dropped support for Python 3.2. Now only supported on Python 2.7 and 3.3 and up, to match versions supported by Requests.
- Many new tests for the new functionality
- Added tests for generating canonical path, including test for fix added in 0.7 for percent encoding of paths
- Added tests for generating canonical querystrings
- Fixed percent encoded characters in URL paths not being encoded again for signature generation, as is expected for all services except S3. This was causing authentication failures whenever these characters appeared in a URL. Thanks to ipartola and cristi23 for the report.
- Two bugfixes for ElasticSearch, thanks to Matthew Thompson for both: * No longer setting body to b’’ during signing if it’s None * Now stripping port from URL netloc for signature generation
- Upgraded the included version of six.py to 1.10
- Fixed a couple of broken Unicode tests on Python 2
- Added a couple more tests for encoding Unicode request bodies
- Included HISTORY.rst in built package to fix pip source install failure. Thanks to Beirdo for the bug report.
- Fixed bug when uploading to S3 with x-amz-acl header which caused authentication failure - headers used in signature are now: host, content-type and all x-amz-* headers (except for x-amz-client-context which breaks Mobile Analytics auth if included)
- Minor docstring and comment updates
- Changed content of LICENSE to vanilla MIT license
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