Side effects of SMBIOS changes (broken MacOS keychains, web logins, et al)

[Coaster]

There are significant side effects for migrating SMBIOS related values, e.g. for an iMacPro 1,1 => MacPro 7,1 configuration for an existing system. The root cause of this is the Hardware UUID, as can be obtained by executing system_profiler SPHardwareDataType

The Hardware UUID output by this command is very significant. If this value changes, all the values in "Local Items" in Keychain Access will disappear (as this is based on that UUID). Most of the saved logins in browsers are based on this "Local Items" keychain database, which is physically stored in a subdirectory of ~/Library/Keychains/ that matches that Hardware UUID. Additionally, almost all browsers will lose their configuration (e.g. all your installed extensions and choice of search engine/privacy settings will be gone), because reasons.

It is unclear what exactly comprises that Hardware UUID, but it is not the same as the SystemUUID in OC config. That said, reverting my SystemUUID, Board Serial/MLB, and SystemSerialNumber back to what I had for my iMacPro 1,1 config, while retaining the SystemProductName and ROM values from my MacPro 7,1 config allowed me to boot without issue as a Mac Pro, had the system_profiler Hardware UUID once again report the same as my prior iMacPro 1,1 config => all my Keychain "Local Items" (i.e. all the saved logins) returned.

Perhaps this is well known, but I didn't find it discussed elsewhere. Also, the effect is somewhat surprising given that there is no user visible error message to indicate the problem ... your saved logins and browser extensions are simply gone (some browsers present a vague error message about "settings being corrupted & reset").

Note that Time Machine backups are useless for this purpose. The files may be backed up, but Keychain Access simply will not access/will not add/will not import database items under a UUID subdirectory for "Local Items" for a "wrong" Hardware UUID.

 

[Coaster]

Furthermore, there is no current way to directly export/import the "Local Items" keychain or its contents. That is to say, you cannot copy/paste Local Items entries into any other keychain, and the File=>Export Items function is disabled. The "Local Items" keychain storage schema is considered to be obfuscated (my guess is salted w/ UUID somehow), so no third party utilities can operate on it either.

Workarounds to migrate "Local Items" entries are:

• Enable iCloud (no thanks)
• Use Migration Assistant somehow (excessive for a simple SMBIOS change that only affects EFI, and this utility is reportedly hit or miss for this purpose anyway)
• Manually export/import all your browser passwords via CSV using the browsers themselves
• Use the Keychain Access utility to copy/reenter your passwords manually, one by one, painfully, with multiple clicks per entry and entering your login password each time (presumably this could be performed with AppleScript, but that would be quite a kludge).