I have an LTO tape drive with a built-in ATTO Thunderlink SH 1068 that relies on an end-of-life(EOL) ATTO SAS/HBA kernel extension, the ATTO ThunderLink SAS HBA Driver 1.25 .

Upon upgrading to macOS Sierra, the kernel extension won't load, so the LTO tape drive doesn't show up in the SAS device tree. It was working fine on El Capitan 10.11.6.

It seems that Gatekeeper in Sierra is now blocking this kernel extension.

Running kextutil -t in Terminal as a diagnostic reveals that the code signature is invalid:

MacBook-Pro:~ user$ sudo kextutil -t /Library/Extensions/ATTOThunderLinkSASHBA.kext Password: Diagnostics for /Library/Extensions/ATTOThunderLinkSASHBA.kext: Code Signing Failure: code signature is invalid Untrusted kexts are not allowed ERROR: invalid signature for com.ATTO.driver.ATTOThunderLinkSASHBA, will not load

What do I need to do to safely load the kernel extension so that my LTO tape drive will work again?