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24 lines
1.2 KiB
Plaintext
24 lines
1.2 KiB
Plaintext
shim is a trivial EFI application that, when run, attempts to open and
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execute another application. It will initially attempt to do this via the
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standard EFI LoadImage() and StartImage() calls. If these fail (because secure
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boot is enabled and the binary is not signed with an appropriate key, for
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instance) it will then validate the binary against a built-in certificate. If
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this succeeds and if the binary or signing key are not blacklisted then shim
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will relocate and execute the binary.
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shim will also install a protocol which permits the second-stage bootloader
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to perform similar binary validation. This protocol has a GUID as described
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in the shim.h header file and provides a single entry point. On 64-bit systems
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this entry point expects to be called with SysV ABI rather than MSABI, and
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so calls to it should not be wrapped.
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On systems with a TPM chip enabled and supported by the system firmware,
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shim will extend various PCRs with the digests of the targets it is
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loading. A full list is in the file README.tpm .
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To use shim, simply place a DER-encoded public certificate in a file such as
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pub.cer and build with "make VENDOR_CERT_FILE=pub.cer".
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There are a couple of build options, and a couple of ways to customize the
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build, described in BUILDING.
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