Migrate glance-replicator to requests for HTTPS Support

Migrate glance-replicator to requests for HTTPS Support

https://blueprints.launchpad.net/glance/+spec/migrate-replicator-to-requests

As operators and users become more security conscious, it is important to support deployments of Glance served only over HTTPS. In its current state, glance-replicator uses httplib and thus does not properly verify HTTPS connections. This allows for various and very serious attacks to be performed while the user of glance-replicator attempts to communicate with Glance.

Problem description

Many deployments currently support both HTTP and HTTPS connections to Glance’s API. As best practices evolve, it will become more common that Glance and other OpenStack services are served only over HTTPS with valid X.509 certificates. Currently, if an operator were to deploy Glance and serve it using only HTTPS, glance-replicator would still allow for a large range of attacks by an observer since it does not verify the certificate that the server provides.

Among other things, the user’s connection to Glance could easily be intercepted by a man-in-the-middle serving a phony certificate who would then proxy or even alter the data sent over the connection. Since the typical user of glance-replicator is an administrator, any service token they have could then be intercepted and used, which is dangerous given the privileges associated with an administrator.

Proposed change

This specification proposes that the code using httplib in glance-replicator be rewritten to use requests. requests supports automatic certificate verification on all HTTPS connections and allows users to provide custom certificate bundles for self-signed certificates.

Given that an operator may choose to sign their own ceritificates for their deployment of Glance, this specification also proposes the addition of a command-line option to glance-replicator to allow the operator to specify a custom certificate bundle to use when verifying the certificate.

Alternatives

One alternative to requests that’s already used in other OpenStack projects is httplib2. This library provides a nearly identical API to httplib and performs certificate verifcation. The library, however, is being actively replaced by many of these same projects by requests. Reducing the number of dependencies that an operator needs to install is also very favorable.

An alternative to making the user specify their custom certificate bundle is to provide a glance-replicator.conf file. This would be an entirely new file. Adding yet another configuration file may add to confusion as to which files are necessary when Glance is deployed as a whole.

Data model impact

None

REST API impact

None

Security impact

For deployments of Glance being served over HTTPS, this will improve the security of the user’s connection.

Notifications impact

None

Other end user impact

Users who have not properly configured HTTPS may receive errors. Since glance-replicator previously did not generate errors, this may be an unpleasant experience for the user. It is the position of the author of this specification that an option to insecurely connect to Glance is a poor choice since the errors will encourage the operators to properly configure Glance to be served over HTTPS.

Performance Impact

None

Other deployer impact

None

Developer impact

None

Implementation

Assignee(s)

Primary assignee:
icordasc
Other contributors:
junhongl

Reviewers

Core reviewer(s):
flaper87 flwang
Other reviewer(s):
nikhil-komawar kragniz

Work Items

  • Refactor glance-replicator to drop a some of its conventions surrounding httplib
  • Replace httplib with requests
  • Add option to specify a custom certificate bundle
  • Add documentation to glance-replicator surrounding the new option and features

Dependencies

None

Testing

requests-mock will be used to write unit tests for glance-replicator to ensure that proper coverage is achieved.

Documentation Impact

glance-replicator’s man page will need to be updated regarding the new configuration options. We should note the two current ways of setting a custom certificate:

  1. requests will look for REQUESTS_CA_BUNDLE and CURL_CA_BUNDLE environment variables
  2. The new glance-replicator option.
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