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c1faa462e0
Provide a mechanism for a physically present end user to disable signature verification. This is handled by the OS passing down a variable that contains a UINT32 and a SHA256 hash. If this variable is present, MokManager prompts the user to choose whether to enable or disable signature validation (depending on the value of the UINT32). They are then asked to type the passphrase that matches the hash. This then saves a boot services variable which is checked by shim, and if set will skip verification of signatures. |
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|---|---|---|
| Cryptlib | ||
| cert.S | ||
| COPYRIGHT | ||
| Makefile | ||
| MokManager.c | ||
| PeImage.h | ||
| README | ||
| shim.c | ||
| shim.h | ||
| signature.h | ||
| TODO | ||
shim is a trivial EFI application that, when run, attempts to open and execute another application. It will initially attempt to do this via the standard EFI LoadImage() and StartImage() calls. If these fail (because secure boot is enabled and the binary is not signed with an appropriate key, for instance) it will then validate the binary against a built-in certificate. If this succeeds and if the binary or signing key are not blacklisted then shim will relocate and execute the binary. shim will also install a protocol which permits the second-stage bootloader to perform similar binary validation. This protocol has a GUID as described in the shim.h header file and provides a single entry point. On 64-bit systems this entry point expects to be called with SysV ABI rather than MSABI, and so calls to it should not be wrapped. To use shim, simply place a hex dump of the public certificate in cert.h and build it with make.