AWS S3 Disabling SSLv3 Support

问题:

We received an email from AWS that basically says 'S3 is disabling SSLv3 Support, access will be cut-off in 15 days'. They then listed some buckets we have (one in production) that are 'currently accepting request from clients that specify SSLv3'. The full email is here, and other AWS users seem to have received one too:

https://gist.github.com/anonymous/4240c8af5208782c144c

My question is how do we test for this scenario, and what do we need to do to prepare for this cut-off date?

We use Rails 4.1 and the Fog (~> 1.28.0) and right_aws (~> 3.1.0) gems for AWS access and we're on Heroku. Our app provides signed HTTPS links to S3 resources to our browser users in our UI.

Is this just a client (browser) issue or something we need to understand better and test/fix?

回答1:

fog uses excon for its http(s) transport. excon is a low-level pure-ruby http client, which relies on the ruby openssl bindings to work. Though it is possible to explicitly set an ssl version to use, excon doesn't, which to the best of my knowledge should mean that it negotiates with the server to choose what to use (so if the server asks for not SSLv3, it should cooperate).

I believe that should mean no action would be required here, but the specifics of all that vary a bit across Ruby and OpenSSL versions (not to mention that it is just a bit hard to introspect/understand the specifics of those bindings), so it is hard to say for certain. excon does support an ssl_version argument, which can be used to force a specific version if it does end up being a problem (this is just not a good general choice because it disallows negotiation and the specifics vary between ruby versions).

Hope that helps.

回答2:

Deadline has been moved:

Based on the feedback received we are extending the deadline for discontinuing support of SSLv3 for securing connections to S3 buckets to 12:00 AM PDT May 20, 2015.

回答3:

Update May 7 2015, 11:26 AM IST

In carrierwave initializer, put things as following,

CarrierWave.configure do |config|
  config.fog_credentials = {
      :provider               => 'AWS',       # required
      :aws_access_key_id      => Settings.carrier_wave.amazon_s3.access_key,       # required
      :aws_secret_access_key  => Settings.carrier_wave.amazon_s3.secret_key,       # required
      :region                 => 'external-1'  # optional, defaults to 'us-east-1'
  }
  config.fog_directory  = Settings.carrier_wave.amazon_s3.bucket                    # required
  #config.fog_host       = 'http://aws.amazon.com/s3/'            # optional, defaults to nil
  config.fog_public     = false                                   # optional, defaults to true
  config.fog_authenticated_url_expiration = 600
  config.fog_attributes = {ssl_version: :TLSv1_2} #{'Cache-Control'=>'max-age=315576000'}  # optional, defaults to {}
end

This worked for me, and have a look at the wireshark trace log.

1577    22.611358000    192.168.0.113   8.8.8.8 DNS 87  Standard query 0xffd8  A s3-external-1.amazonaws.com
1578    22.611398000    192.168.0.113   8.8.8.8 DNS 87  Standard query 0xbf2f  AAAA s3-external-1.amazonaws.com
1580    22.731084000    8.8.8.8 192.168.0.113   DNS 103 Standard query response 0xffd8  A 54.231.1.234
1586    22.849595000    54.231.10.34    192.168.0.113   TLSv1.2 107 Encrypted Alert

1594    23.012866000    192.168.0.113   54.231.1.234    TLSv1.2 347 Client Hello
1607    23.310950000    192.168.0.113   54.231.1.234    TLSv1.2 204 Client Key Exchange, Change Cipher Spec, Encrypted Handshake Message
1608    23.578966000    54.231.1.234    192.168.0.113   TLSv1.2 129 Change Cipher Spec, Encrypted Handshake Message
1609    23.579480000    192.168.0.113   54.231.1.234    TLSv1.2 427 Application Data
1610    23.868725000    54.231.1.234    192.168.0.113   TLSv1.2 299 Application Data

---

Update May 6 2015, 6-53 PM IST

Ok, After updating the Excon gem, we are able to see the TLSv1.2 protocol between our server and S3 servers.

bundle update excon

Wireshark trace log statements,

29  1.989230000 192.168.0.115   54.231.32.0 SSL 336 Client Hello
34  2.215461000 54.231.32.0 192.168.0.115   TLSv1.2 1494    Server Hello
40  2.219301000 54.231.32.0 192.168.0.115   TLSv1.2 471 Certificate
42  2.222127000 192.168.0.115   54.231.32.0 TLSv1.2 204 Client Key Exchange, Change Cipher Spec, Encrypted Handshake Message

---

UPDATE May 6, 2015, 4-29 PM IST

After updating the hosts file, following is the wireshark trace log.

14  2.012094000 192.168.0.115   54.231.32.0 SSLv3   192 Client Hello 
17  2.242423000 54.231.32.0 192.168.0.115   SSLv3   61  Alert (Level:  Fatal, Description: Handshake Failure)

---

Please see the above wireshark request capture, when I upload a file from my local development rails on S3. As it shows, on initial handshake Amazon server uses SSLv3 and so my rails server sends all future requests with SSLv3.

Now, the question is, How can I change the bucket settings so that it would accept/initiate the process using TLS only? I have checked in amazon settings, there is nothing like that.

I have already changed my nginx to use TLS, but I think that is not needed because Rails will talk to S3 in the background using Excon as mentioned in above comment.

So, Please suggest what could be the best possible way to test this before 20th May, to make sure that it will not break on that day.

Any help would be great.

Just for information - My bucket name is like xyz.abc.com, so no - in the name.

回答4:

AWS's official FAQ https://forums.aws.amazon.com/thread.jspa?threadID=179904&tstart=0

54.231.32.0 s3.amazonaws.com
54.231.32.1 <bucket name>.s3.amazonaws.com
54.231.32.3 <bucket name>.s3-external-1.amazonaws.com

Configure the above in your /etc/hosts, replacing <bucket name> with your bucket name.

NOTE: when using with a non us-east-1 bucket you may get redirect and failure responses. This has more to do with their adhoc infrastructure for testing this than anything else. So ignore that.

Create a "standard US bucket" and test with that instead. Remember to configure your app to use s3 region external-1

FWIW, my app using paperclip (4.2.0) on ruby 2.1.4 works fine.

回答5:

It is a client-side issue entirely , if the protocol that the client (e.g the browser) uses to issue requests over https is SSLv3 , than the ssl handshake will not succeed and these requests will fail. So it's the client that needs to disable SSLv3.

AWS's action is a follow-up on the POODLE vulnerability uncovered last year , and since then also all the AWS CloudFront distributions that use the *.cloudfront.net domain name have been updated with discontinued SSLv3 support .Now AWS is moving on to S3 to do the same.

回答6:

I was able to force TLS using the following setting in my fog config:

connection_options: { ssl_version: :TLSv1_2 }

To test, update your host file (instructions from AWS):

54.231.32.0 s3.amazonaws.com
54.231.32.1 bucket.s3.amazonaws.com   #replace bucket with your bucket name
54.231.32.3 bucket.s3-external-1.amazonaws.com   #replace bucket with your bucket name

I was able to connect successfully. Also, If you change the setting to :SSLv3 you'll get an error. Good Luck!