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stub: pass .pcrsig and .pcrpkey PE sections as cpio into invoked kernel

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Pick up the two new sections in sd-stub and pass them as initrds into
the booted kernels, where they'll show up as
/.extra/tpm2-pcr-signature.json and /.extra/tpm2-pcr-public-key.pem in
the initrd file system.

The initrd is then supposed to pick these files up from there and save
them at a place that will survive into the host OS.
This commit is contained in:
Lennart Poettering 2022-08-25 16:55:49 +02:00
parent df7ee6f8b0
commit 23002b45b1
1 changed files with 72 additions and 30 deletions
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102
src/boot/efi/stub.c
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@ -20,9 +20,7 @@ _used_ _section_(".sdmagic") static const char magic[] = "#### LoaderInfo: syste
static EFI_STATUS combine_initrd(
EFI_PHYSICAL_ADDRESS initrd_base, UINTN initrd_size,
const void *credential_initrd, UINTN credential_initrd_size,
const void *global_credential_initrd, UINTN global_credential_initrd_size,
const void *sysext_initrd, UINTN sysext_initrd_size,
const void * const extra_initrds[], const size_t extra_initrd_sizes[], size_t n_extra_initrds,
EFI_PHYSICAL_ADDRESS *ret_initrd_base, UINTN *ret_initrd_size) {
EFI_PHYSICAL_ADDRESS base = UINT32_MAX; /* allocate an area below the 32bit boundary for this */
@ -36,23 +34,15 @@ static EFI_STATUS combine_initrd(
/* Combines four initrds into one, by simple concatenation in memory */
n = ALIGN4(initrd_size); /* main initrd might not be padded yet */
if (credential_initrd) {
if (n > UINTN_MAX - credential_initrd_size)
for (size_t i = 0; i < n_extra_initrds; i++) {
if (!extra_initrds[i])
continue;
if (n > UINTN_MAX - extra_initrd_sizes[i])
return EFI_OUT_OF_RESOURCES;
n += credential_initrd_size;
}
if (global_credential_initrd) {
if (n > UINTN_MAX - global_credential_initrd_size)
return EFI_OUT_OF_RESOURCES;
n += global_credential_initrd_size;
}
if (sysext_initrd) {
if (n > UINTN_MAX - sysext_initrd_size)
return EFI_OUT_OF_RESOURCES;
n += sysext_initrd_size;
n += extra_initrd_sizes[i];
}
err = BS->AllocatePages(
@ -78,12 +68,12 @@ static EFI_STATUS combine_initrd(
}
}
if (credential_initrd)
p = mempcpy(p, credential_initrd, credential_initrd_size);
if (global_credential_initrd)
p = mempcpy(p, global_credential_initrd, global_credential_initrd_size);
if (sysext_initrd)
p = mempcpy(p, sysext_initrd, sysext_initrd_size);
for (size_t i = 0; i < n_extra_initrds; i++) {
if (!extra_initrds[i])
continue;
p = mempcpy(p, extra_initrds[i], extra_initrd_sizes[i]);
}
assert((uint8_t*) PHYSICAL_ADDRESS_TO_POINTER(base) + n == p);
@ -150,10 +140,9 @@ static void export_variables(EFI_LOADED_IMAGE_PROTOCOL *loaded_image) {
}
EFI_STATUS efi_main(EFI_HANDLE image, EFI_SYSTEM_TABLE *sys_table) {
_cleanup_free_ void *credential_initrd = NULL, *global_credential_initrd = NULL, *sysext_initrd = NULL, *pcrsig_initrd = NULL, *pcrpkey_initrd = NULL;
UINTN credential_initrd_size = 0, global_credential_initrd_size = 0, sysext_initrd_size = 0, pcrsig_initrd_size = 0, pcrpkey_initrd_size = 0;
UINTN cmdline_len = 0, linux_size, initrd_size, dt_size;
UINTN credential_initrd_size = 0, global_credential_initrd_size = 0, sysext_initrd_size = 0;
_cleanup_free_ void *credential_initrd = NULL, *global_credential_initrd = NULL;
_cleanup_free_ void *sysext_initrd = NULL;
EFI_PHYSICAL_ADDRESS linux_base, initrd_base, dt_base;
_cleanup_(devicetree_cleanup) struct devicetree_state dt_state = {};
EFI_LOADED_IMAGE_PROTOCOL *loaded_image;
@ -305,6 +294,45 @@ EFI_STATUS efi_main(EFI_HANDLE image, EFI_SYSTEM_TABLE *sys_table) {
if (sysext_measured)
(void) efivar_set_uint_string(LOADER_GUID, L"StubPcrInitRDSysExts", TPM_PCR_INDEX_INITRD_SYSEXTS, 0);
/* If the PCR signature was embedded in the PE image, then let's wrap it in a cpio and also pass it
* to the kernel, so that it can be read from /.extra/tpm2-pcr-signature.json. Note that this section
* is not measured, neither as raw section (see above), nor as cpio (here), because it is the
* signature of expected PCR values, i.e. it's input are PCR measurement, and hence it shouldn't
* itself be input for PCR measurements. */
if (szs[UNIFIED_SECTION_PCRSIG] > 0)
(void) pack_cpio_literal(
(uint8_t*) loaded_image->ImageBase + addrs[UNIFIED_SECTION_PCRSIG],
szs[UNIFIED_SECTION_PCRSIG],
".extra",
L"tpm2-pcr-signature.json",
/* dir_mode= */ 0555,
/* access_mode= */ 0444,
/* tpm_pcr= */ NULL,
/* n_tpm_pcr= */ 0,
/* tpm_description= */ NULL,
&pcrsig_initrd,
&pcrsig_initrd_size,
/* ret_measured= */ NULL);
/* If the public key used for the PCR signatures was embedded in the PE image, then let's wrap it in
* a cpio and also pass it to the kernel, so that it can be read from
* /.extra/tpm2-pcr-public-key.pem. This section is already measure above, hence we won't measure the
* cpio. */
if (szs[UNIFIED_SECTION_PCRPKEY] > 0)
(void) pack_cpio_literal(
(uint8_t*) loaded_image->ImageBase + addrs[UNIFIED_SECTION_PCRPKEY],
szs[UNIFIED_SECTION_PCRPKEY],
".extra",
L"tpm2-pcr-public-key.pem",
/* dir_mode= */ 0555,
/* access_mode= */ 0444,
/* tpm_pcr= */ NULL,
/* n_tpm_pcr= */ 0,
/* tpm_description= */ NULL,
&pcrpkey_initrd,
&pcrpkey_initrd_size,
/* ret_measured= */ NULL);
linux_size = szs[UNIFIED_SECTION_LINUX];
linux_base = POINTER_TO_PHYSICAL_ADDRESS(loaded_image->ImageBase) + addrs[UNIFIED_SECTION_LINUX];
@ -318,9 +346,21 @@ EFI_STATUS efi_main(EFI_HANDLE image, EFI_SYSTEM_TABLE *sys_table) {
/* If we have generated initrds dynamically, let's combine them with the built-in initrd. */
err = combine_initrd(
initrd_base, initrd_size,
credential_initrd, credential_initrd_size,
global_credential_initrd, global_credential_initrd_size,
sysext_initrd, sysext_initrd_size,
(const void*const[]) {
credential_initrd,
global_credential_initrd,
sysext_initrd,
pcrsig_initrd,
pcrpkey_initrd,
},
(const size_t[]) {
credential_initrd_size,
global_credential_initrd_size,
sysext_initrd_size,
pcrsig_initrd_size,
pcrpkey_initrd_size,
},
5,
&initrd_base, &initrd_size);
if (err != EFI_SUCCESS)
return err;
@ -329,6 +369,8 @@ EFI_STATUS efi_main(EFI_HANDLE image, EFI_SYSTEM_TABLE *sys_table) {
credential_initrd = mfree(credential_initrd);
global_credential_initrd = mfree(global_credential_initrd);
sysext_initrd = mfree(sysext_initrd);
pcrsig_initrd = mfree(pcrsig_initrd);
pcrpkey_initrd = mfree(pcrpkey_initrd);
}
if (dt_size > 0) {