Reviewed: https://review.openstack.org/308466 Committed: https://git.openstack.org/cgit/openstack/glance/commit/?id=5ab63107b69e381f04bfa4aa9143e229ac2a9857 Submitter: Jenkins Branch: master
commit 5ab63107b69e381f04bfa4aa9143e229ac2a9857 Author: Dane Fichter <[email protected]> Date: Tue Apr 19 01:27:02 2016 -0400 Remove deprecated "sign-the-hash" approach This change removes the "sign-the-hash" signature verification code in the signature_utils module and the ImageProxy class. This code was deprecated in Mitaka and scheduled for removal in Newton. Change-Id: I8862f6c94538dd818c7360ba287e14c1264ff20f Closes-Bug: #1516031 ** Changed in: glance Status: In Progress => Fix Released -- You received this bug notification because you are a member of Yahoo! Engineering Team, which is subscribed to Glance. https://bugs.launchpad.net/bugs/1516031 Title: Use of MD5 in OpenStack Glance image signature (CVE-2015-8234) Status in Glance: Fix Released Status in OpenStack Security Advisory: Won't Fix Status in OpenStack Security Notes: Fix Released Bug description: This have been reported by Daniel P. Berrange: " In the OpenStack Liberty release, the Glance project added support for image signature verification. http://specs.openstack.org/openstack/glance-specs/specs/liberty/image- signing-and-verification-support.html The verification code was added in the following git commit https://github.com/openstack/glance/commit/484ef1b40b738c87adb203bba6107ddb4b04ff6e Unfortunately the design of this signature verification method is flawed by design. The generalized approach to creating signatures of content is to apply a hash to the content and then encrypt it in some manner. Consider that the signature is defined to use hash=sha256 and cipher=rsa we can describe the signature computation as signature = rsa(sha256(content)) In the case of verifying a disk image, the content we care about verifying is the complete disk image file. Unfortunately, the glance specification chose *not* to compute the signature against the disk image file. Glance already had an MD5 checksum calculated for the disk image file, so they instead chose to compute the signature against the MD5 checksum instead. ie glance is running signature = rsa(sha256(md5(disk-image-content))) This degrades the security of the system to that of the weakest hash, which is obviously MD5 here. The code where glance verifies the signature is in the glance/locations.py, the 'set_data' method where is does result = signature_utils.verify_signature( self.context, checksum, self.image.extra_properties) if result: LOG.info(_LI("Successfully verified signature for image %s"), self.image.image_id) The 'checksum' variable is populate by the glance_store driver, but it is hardcoded to always be md5 in all current glance storage backends: $ git grep hashlib glance_store/_drivers/ | grep checksum glance_store/_drivers/filesystem.py: checksum = hashlib.md5() glance_store/_drivers/rbd.py: checksum = hashlib.md5() glance_store/_drivers/s3.py: checksum = hashlib.md5() glance_store/_drivers/s3.py: checksum = hashlib.md5() glance_store/_drivers/sheepdog.py: checksum = hashlib.md5() glance_store/_drivers/swift/store.py: checksum = hashlib.md5() glance_store/_drivers/vmware_datastore.py: self.checksum = hashlib.md5() Since we will soon be shipping OpenStack Liberty release, we need to at least give a security notice to alert our customers to the fact that the signature verification is cryptographically weak/broken. IMHO, it quite likely deserves a CVE though NB, this is public knowledge as I first became aware of this flawed design in comments / discussion on a public specification proposed to implement the same approach in the Nova project. My suggested way to fix this is to simply abandon the current impl and re-do it such that it directly computes the signature against the disk image, and does not use the existing md5 checksum in any way. Regards, Daniel " Mailing list thread for Nova impl: http://lists.openstack.org/pipermail/openstack-dev/2015-November/079348.html Nova Spec: https://review.openstack.org/#/c/188874/ To manage notifications about this bug go to: https://bugs.launchpad.net/glance/+bug/1516031/+subscriptions -- Mailing list: https://launchpad.net/~yahoo-eng-team Post to : [email protected] Unsubscribe : https://launchpad.net/~yahoo-eng-team More help : https://help.launchpad.net/ListHelp
