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https://git.proxmox.com/git/efi-boot-shim
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c6bedd5b83
Currently, all three invocations of the translate_slashes() function may
lead to writes to the string literal that is #defined with the
DEFAULT_LOADER_CHAR macro. According to ISO C99 6.4.5p6, this is undefined
behavior ("If the program attempts to modify such an array, the behavior
is undefined").
This bug crashes shim on e.g. the 64-bit ArmVirtQemu platform ("Data
abort: Permission fault"), where the platform firmware maps the .text
section (which contains the string literal) read-only.
Modify translate_slashes() so that it copies and translates characters
from an input array of "char" to an output array of "CHAR8".
While at it, fix another bug. Before this patch, if translate_slashes()
ever encountered a double backslash (translating it to a single forward
slash), then the output would end up shorter than the input. However, the
output was not NUL-terminated in-place, therefore the original string
length (and according trailing garbage) would be preserved. After this
patch, the NUL-termination on contraction is automatic, as the output
array's contents are indeterminate when entering the function, and so we
must NUL-terminate it anyway.
Fixes:
|
||
|---|---|---|
| Cryptlib | ||
| include | ||
| lib | ||
| .gitignore | ||
| .syntastic_c_config | ||
| .travis.yml | ||
| buildid.c | ||
| BUILDING | ||
| cert.S | ||
| COPYRIGHT | ||
| crypt_blowfish.c | ||
| elf_aarch64_efi.lds | ||
| elf_arm_efi.lds | ||
| elf_ia32_efi.lds | ||
| elf_ia64_efi.lds | ||
| elf_x86_64_efi.lds | ||
| errlog.c | ||
| fallback.c | ||
| httpboot.c | ||
| make-certs | ||
| Make.coverity | ||
| Make.defaults | ||
| Make.rules | ||
| Make.scan-build | ||
| Makefile | ||
| model.c | ||
| mok.c | ||
| MokManager.c | ||
| MokVars.txt | ||
| netboot.c | ||
| PasswordCrypt.c | ||
| README | ||
| README.fallback | ||
| README.tpm | ||
| replacements.c | ||
| shim.c | ||
| shim.h | ||
| testplan.txt | ||
| TODO | ||
| tpm.c | ||
| travis-build.sh | ||
| version.c.in | ||
| version.h | ||
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. On systems with a TPM chip enabled and supported by the system firmware, shim will extend various PCRs with the digests of the targets it is loading. A full list is in the file README.tpm . To use shim, simply place a DER-encoded public certificate in a file such as pub.cer and build with "make VENDOR_CERT_FILE=pub.cer". There are a couple of build options, and a couple of ways to customize the build, described in BUILDING.