Changes/NSSDBMRemoval

NSS dbm support removal

Summary

Network Security Services (NSS) historically supports 2 different database backends, based on SQLite and dbm. Since Fedora 28, the SQLite backend has been used by default and the dbm backend has been deprecated (NSS Default File Format SQL). This Change is about removing the support for the dbm backend entirely.

Owner

• Name: Daiki Ueno
• Email: dueno@redhat.com

Current status

• Targeted release: Fedora 33
• Last updated: 2020-07-27
• FESCo issue: #2415
• Tracker bug: #1860953
• Release notes tracker: #540

Detailed Description

Applications that use the NSS library often use a database for storage of keys, certificates and trust. NSS supports two different storage formats, one is based on SQLite and another one is based on dbm files.

Today's default file format used by NSS, used when applications omit the type parameter, is the SQLite file format, and the older dbm format has been considered as deprecated since Fedora 28, because it has several drawbacks such as lack of support for parallel access to the storage.

As the default change was made 2 years ago, and NSS provides a transparent migration mechanism from the dbm format to the SQLite format, the suggestion is to completely disable the dbm backend.

Benefit to Fedora

There are a few benefits:

• By disabling the dbm database, the size of the library binary will be slightly smaller
• The NSS developers will be able to focus on the new file format

Scope

• Proposal owners:

A build time environment variable (NSS_DISABLE_DBM) needs to be set.

• Other developers: N/A (not a System Wide Change)

• Release engineering: #Releng issue number (a check of an impact with Release Engineering is needed)

• Policies and guidelines: N/A (not a System Wide Change)

• Trademark approval: N/A (not needed for this Change)

Upgrade/compatibility impact

It is assured that the existing databases on the system are properly migrated, as long as they have been created or accessed with the default method on any supported Fedora releases (i.e., Fedora 31 or later). On the other hand, if a database is created explicitly as dbm, it needs to be converted before upgrading to F33. We will provide a script to check NSS databases on known locations and possibly run it during the package upgrade process.

Overall, as we consider the impact should be limited, we propose this as a Self Contained Change, rather than a System Wide Change.

Note: in the discussion on the fedora-devel list, it was pointed that pesign package embedded the dbm format database. It has now been resolved in bug 1827902.

How To Test

N/A (not a System Wide Change)

User Experience

No user visible changes.

Dependencies

N/A (not a System Wide Change)

Contingency Plan

• Contingency mechanism: Revert the shipped configuration
• Contingency deadline: N/A (not a System Wide Change)
• Blocks release? No
• Blocks product? No

Documentation

N/A (not a System Wide Change)