Glance is still using outdated md5 for image signing

[Michael Xin]

Glance is still using md5 for image signing. MD5 is outdated and should not be used for security reason. It makes it possible for malicious users to generate malicious image with same hash values.

https://specs.openstack.org/openstack/glance-specs/specs/liberty/image-signing-and-verification-support.html
Glance already supports computing checksums of images when an image is uploaded, and this checksum is stored with the image. This same hash (which by default is MD5) will be used for the signature verification.

In the code:
https://github.com/openstack/glance/blob/2682dfe2000604bd1a77cfad5ad259f084a1359f/glance/image_cache/__init__.py

line 242:
 def cache_tee_iter(self, image_id, image_iter, image_checksum):
        try:
            current_checksum = hashlib.md5()

            with self.driver.open_for_write(image_id) as cache_file:
                for chunk in image_iter:
                    try:
                        cache_file.write(chunk)
                    finally:
                        current_checksum.update(chunk)
                        yield chunk
                cache_file.flush()

[Tristan Cacqueray (tristan-cacqueray)]

Since this report concerns a possible security risk, an incomplete security advisory task has been added while the core security reviewers for the affected project or projects confirm the bug and discuss the scope of any vulnerability along with potential solutions.

Is this a duplicate of bug 1516031, and is this affecting stable/release ?

[Jeremy Stanley (fungi)]

Regardless, the fact that Glance uses MD5 for image signatures in currently supported stable releases is already widely publicized in https://wiki.openstack.org/wiki/OSSN/OSSN-0061 so there's no need for this bug to be reported in private. I recommend switching it to public and either marking it as a duplicate if appropriate or security hardening opportunity otherwise.