86ec48882b
The loopback image is configured to function as a disk by being mapped as a block device. Instead of measuring the entire block device we should focus on tracking the individual files accessed from it. For example, we do not directly measure block devices like hd0 disk but the files opened from it. This method is important to avoid running out of memory since loopback images can be very large. Trying to read and measure the whole image at once could cause out of memory errors and disrupt the boot process. Signed-off-by: Michael Chang <mchang@suse.com> Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
126 lines
3.7 KiB
C
126 lines
3.7 KiB
C
/*
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* GRUB -- GRand Unified Bootloader
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* Copyright (C) 2018 Free Software Foundation, Inc.
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*
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* GRUB is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* GRUB is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with GRUB. If not, see <http://www.gnu.org/licenses/>.
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*
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* Core TPM support code.
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*/
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#include <grub/err.h>
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#include <grub/i18n.h>
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#include <grub/misc.h>
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#include <grub/mm.h>
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#include <grub/tpm.h>
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#include <grub/term.h>
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#include <grub/verify.h>
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#include <grub/dl.h>
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GRUB_MOD_LICENSE ("GPLv3+");
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static grub_err_t
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grub_tpm_verify_init (grub_file_t io,
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enum grub_file_type type __attribute__ ((unused)),
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void **context, enum grub_verify_flags *flags)
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{
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*context = io->name;
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*flags |= GRUB_VERIFY_FLAGS_SINGLE_CHUNK;
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/*
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* The loopback image is mapped as a disk allowing it to function like
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* a block device. However, we measure files read from the block device
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* not the device itself. For example, we don't measure block devices like
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* hd0 disk directly. This process is crucial to prevent out-of-memory
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* errors as loopback images are inherently large.
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*/
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if ((type & GRUB_FILE_TYPE_MASK) == GRUB_FILE_TYPE_LOOPBACK)
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*flags = GRUB_VERIFY_FLAGS_SKIP_VERIFICATION;
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return GRUB_ERR_NONE;
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}
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static grub_err_t
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grub_tpm_verify_write (void *context, void *buf, grub_size_t size)
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{
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grub_err_t status = grub_tpm_measure (buf, size, GRUB_BINARY_PCR, context);
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if (status == GRUB_ERR_NONE)
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return GRUB_ERR_NONE;
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grub_dprintf ("tpm", "Measuring buffer failed: %d\n", status);
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return grub_is_tpm_fail_fatal () ? status : GRUB_ERR_NONE;
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}
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static grub_err_t
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grub_tpm_verify_string (char *str, enum grub_verify_string_type type)
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{
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const char *prefix = NULL;
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char *description;
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grub_err_t status;
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switch (type)
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{
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case GRUB_VERIFY_KERNEL_CMDLINE:
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prefix = "kernel_cmdline: ";
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break;
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case GRUB_VERIFY_MODULE_CMDLINE:
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prefix = "module_cmdline: ";
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break;
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case GRUB_VERIFY_COMMAND:
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prefix = "grub_cmd: ";
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break;
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}
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description = grub_malloc (grub_strlen (str) + grub_strlen (prefix) + 1);
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if (!description)
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return grub_errno;
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grub_memcpy (description, prefix, grub_strlen (prefix));
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grub_memcpy (description + grub_strlen (prefix), str,
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grub_strlen (str) + 1);
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status =
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grub_tpm_measure ((unsigned char *) str, grub_strlen (str),
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GRUB_STRING_PCR, description);
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grub_free (description);
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if (status == GRUB_ERR_NONE)
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return GRUB_ERR_NONE;
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grub_dprintf ("tpm", "Measuring string %s failed: %d\n", str, status);
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return grub_is_tpm_fail_fatal () ? status : GRUB_ERR_NONE;
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}
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struct grub_file_verifier grub_tpm_verifier = {
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.name = "tpm",
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.init = grub_tpm_verify_init,
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.write = grub_tpm_verify_write,
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.verify_string = grub_tpm_verify_string,
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};
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GRUB_MOD_INIT (tpm)
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{
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/*
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* Even though this now calls ibmvtpm's grub_tpm_present() from GRUB_MOD_INIT(),
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* it does seem to call it late enough in the initialization sequence so
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* that whatever discovered "device nodes" before this GRUB_MOD_INIT() is
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* called, enables the ibmvtpm driver to see the device nodes.
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*/
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if (!grub_tpm_present())
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return;
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grub_verifier_register (&grub_tpm_verifier);
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}
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GRUB_MOD_FINI (tpm)
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{
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if (!grub_tpm_present())
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return;
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grub_verifier_unregister (&grub_tpm_verifier);
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}
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