[PATCH v4 08/16] efi_loader: image_loader: support image authentication
AKASHI Takahiro
takahiro.akashi at linaro.org
Wed Jan 22 08:42:29 CET 2020
Heinrich,
On Wed, Jan 22, 2020 at 10:13:48AM +0900, AKASHI Takahiro wrote:
> On Tue, Jan 21, 2020 at 08:15:06AM +0100, Heinrich Schuchardt wrote:
> > On 1/21/20 7:12 AM, AKASHI Takahiro wrote:
> > >On Fri, Jan 17, 2020 at 06:51:50AM +0100, Heinrich Schuchardt wrote:
> > >>On 1/17/20 6:11 AM, AKASHI Takahiro wrote:
> > >>>On Thu, Jan 09, 2020 at 12:55:17AM +0100, Heinrich Schuchardt wrote:
> > >>>>On 12/18/19 1:45 AM, AKASHI Takahiro wrote:
> > >>>>>With this commit, image validation can be enforced, as UEFI specification
> > >>>>>section 32.5 describes, if CONFIG_EFI_SECURE_BOOT is enabled.
> > >>>>>
> > >>>>>Currently we support
> > >>>>>* authentication based on db and dbx,
> > >>>>> so dbx-validated image will always be rejected.
> > >>>>>* following signature types:
> > >>>>> EFI_CERT_SHA256_GUID (SHA256 digest for unsigned images)
> > >>>>> EFI_CERT_X509_GUID (x509 certificate for signed images)
> > >>>>>Timestamp-based certificate revocation is not supported here.
> > >>>>>
> > >>>>>Internally, authentication data is stored in one of certificates tables
> > >>>>>of PE image (See efi_image_parse()) and will be verified by
> > >>>>>efi_image_authenticate() before loading a given image.
> > >>>>>
> > >>>>>It seems that UEFI specification defines the verification process
> > >>>>>in a bit ambiguous way. I tried to implement it as closely to as
> > >>>>>EDK2 does.
> > >>>>>
> > >>>>>Signed-off-by: AKASHI Takahiro <takahiro.akashi at linaro.org>
> > >>>>>---
> > >>>>> include/efi_loader.h | 7 +-
> > >>>>> lib/efi_loader/efi_boottime.c | 2 +-
> > >>>>> lib/efi_loader/efi_image_loader.c | 454 +++++++++++++++++++++++++++++-
> > >>>>> 3 files changed, 449 insertions(+), 14 deletions(-)
> > >>>>>
> > >>>>>diff --git a/include/efi_loader.h b/include/efi_loader.h
> > >>>>>index 1f88caf86709..e12b49098fb0 100644
> > >>>>>--- a/include/efi_loader.h
> > >>>>>+++ b/include/efi_loader.h
> > >>>>>@@ -11,6 +11,7 @@
> > >>>>> #include <common.h>
> > >>>>> #include <part_efi.h>
> > >>>>> #include <efi_api.h>
> > >>>>>+#include <pe.h>
> > >>>>>
> > >>>>> static inline int guidcmp(const void *g1, const void *g2)
> > >>>>> {
> > >>>>>@@ -398,7 +399,8 @@ efi_status_t efi_set_watchdog(unsigned long timeout);
> > >>>>> /* Called from places to check whether a timer expired */
> > >>>>> void efi_timer_check(void);
> > >>>>> /* PE loader implementation */
> > >>>>>-efi_status_t efi_load_pe(struct efi_loaded_image_obj *handle, void *efi,
> > >>>>>+efi_status_t efi_load_pe(struct efi_loaded_image_obj *handle,
> > >>>>>+ void *efi, size_t efi_size,
> > >>>>> struct efi_loaded_image *loaded_image_info);
> > >>>>> /* Called once to store the pristine gd pointer */
> > >>>>> void efi_save_gd(void);
> > >>>>>@@ -726,6 +728,9 @@ void efi_sigstore_free(struct efi_signature_store *sigstore);
> > >>>>> struct efi_signature_store *efi_sigstore_parse_sigdb(u16 *name);
> > >>>>>
> > >>>>> bool efi_secure_boot_enabled(void);
> > >>>>>+
> > >>>>>+bool efi_image_parse(void *efi, size_t len, struct efi_image_regions **regp,
> > >>>>>+ WIN_CERTIFICATE **auth, size_t *auth_len);
> > >>>>> #endif /* CONFIG_EFI_SECURE_BOOT */
> > >>>>>
> > >>>>> #else /* CONFIG_IS_ENABLED(EFI_LOADER) */
> > >>>>>diff --git a/lib/efi_loader/efi_boottime.c b/lib/efi_loader/efi_boottime.c
> > >>>>>index 493d906c641d..311681764034 100644
> > >>>>>--- a/lib/efi_loader/efi_boottime.c
> > >>>>>+++ b/lib/efi_loader/efi_boottime.c
> > >>>>>@@ -1879,7 +1879,7 @@ efi_status_t EFIAPI efi_load_image(bool boot_policy,
> > >>>>> efi_dp_split_file_path(file_path, &dp, &fp);
> > >>>>> ret = efi_setup_loaded_image(dp, fp, image_obj, &info);
> > >>>>> if (ret == EFI_SUCCESS)
> > >>>>>- ret = efi_load_pe(*image_obj, dest_buffer, info);
> > >>>>>+ ret = efi_load_pe(*image_obj, dest_buffer, source_size, info);
> > >>>>> if (!source_buffer)
> > >>>>> /* Release buffer to which file was loaded */
> > >>>>> efi_free_pages((uintptr_t)dest_buffer,
> > >>>>>diff --git a/lib/efi_loader/efi_image_loader.c b/lib/efi_loader/efi_image_loader.c
> > >>>>>index 13541cfa7a28..939758e61e3c 100644
> > >>>>>--- a/lib/efi_loader/efi_image_loader.c
> > >>>>>+++ b/lib/efi_loader/efi_image_loader.c
> > >>>>>@@ -9,7 +9,9 @@
> > >>>>>
> > >>>>> #include <common.h>
> > >>>>> #include <efi_loader.h>
> > >>>>>+#include <malloc.h>
> > >>>>> #include <pe.h>
> > >>>>>+#include "../lib/crypto/pkcs7_parser.h"
> > >>>>>
> > >>>>> const efi_guid_t efi_global_variable_guid = EFI_GLOBAL_VARIABLE_GUID;
> > >>>>> const efi_guid_t efi_guid_device_path = EFI_DEVICE_PATH_PROTOCOL_GUID;
> > >>>>>@@ -205,6 +207,367 @@ static void efi_set_code_and_data_type(
> > >>>>> }
> > >>>>> }
> > >>>>>
> > >>>>>+#ifdef CONFIG_EFI_SECURE_BOOT
> > >>>>>+/**
> > >>>>>+ * efi_image_parse - parse a PE image
> > >>>>>+ * @efi: Pointer to image
> > >>>>>+ * @len: Size of @efi
> > >>>>>+ * @regs: Pointer to a list of regions
> > >>>>>+ * @auth: Pointer to a pointer to authentication data in PE
> > >>>>>+ * @auth_len: Size of @auth
> > >>>>>+ *
> > >>>>>+ * Parse image binary in PE32(+) format, assuming that sanity of PE image
> > >>>>>+ * has been checked by a caller.
> > >>>>>+ * On success, an address of authentication data in @efi and its size will
> > >>>>>+ * be returned in @auth and @auth_len, respectively.
> > >>>>>+ *
> > >>>>>+ * Return: true on success, false on error
> > >>>>>+ */
> > >>>>>+bool efi_image_parse(void *efi, size_t len, struct efi_image_regions **regp,
> > >>>>>+ WIN_CERTIFICATE **auth, size_t *auth_len)
> > >>>>
> > >>>>
> > >>>>This function is way too long (> 100 lines). Please, cut it into logical
> > >>>>units.
> > >>>>
> > >>>>
> > >>>>
> > >>>>>+{
> > >>>>>+ struct efi_image_regions *regs;
> > >>>>>+ IMAGE_DOS_HEADER *dos;
> > >>>>>+ IMAGE_NT_HEADERS32 *nt;
> > >>>>>+ IMAGE_SECTION_HEADER *sections, **sorted;
> > >>>>>+ int num_regions, num_sections, i, j;
> > >>>>>+ int ctidx = IMAGE_DIRECTORY_ENTRY_SECURITY;
> > >>>>>+ u32 align, size, authsz, authoff;
> > >>>>>+ size_t bytes_hashed;
> > >>>>>+
> > >>>>>+ dos = (void *)efi;
> > >>>>>+ nt = (void *)(efi + dos->e_lfanew);
> > >>>>>+
> > >>>>>+ /*
> > >>>>>+ * Count maximum number of regions to be digested.
> > >>>>>+ * We don't have to have an exact number here.
> > >>>>>+ * See efi_image_region_add()'s in parsing below.
> > >>>>>+ */
> > >>>>>+ num_regions = 3; /* for header */
> > >>>>>+ num_regions += nt->FileHeader.NumberOfSections;
> > >>>>>+ num_regions++; /* for extra */
> > >>>>>+
> > >>>>>+ regs = calloc(sizeof(*regs) + sizeof(struct image_region) * num_regions,
> > >>>>>+ 1);
> > >>>>>+ if (!regs)
> > >>>>>+ goto err;
> > >>>>>+ regs->max = num_regions;
> > >>>>>+
> > >>>>>+ /*
> > >>>>>+ * Collect data regions for hash calculation
> > >>>>>+ * 1. File headers
> > >>>>>+ */
> > >>>>>+ if (nt->OptionalHeader.Magic == IMAGE_NT_OPTIONAL_HDR64_MAGIC) {
> > >>>>>+ IMAGE_NT_HEADERS64 *nt64 = (void *)nt;
> > >>>>>+ IMAGE_OPTIONAL_HEADER64 *opt = &nt64->OptionalHeader;
> > >>>>>+
> > >>>>>+ /* Skip CheckSum */
> > >>>>>+ efi_image_region_add(regs, efi, &opt->CheckSum, 0);
> > >>>>>+ if (nt64->OptionalHeader.NumberOfRvaAndSizes <= ctidx) {
> > >>>>>+ efi_image_region_add(regs,
> > >>>>>+ &opt->CheckSum + 1,
> > >>>>>+ efi + opt->SizeOfHeaders, 0);
> > >>>>>+ } else {
> > >>>>>+ /* Skip Certificates Table */
> > >>>>>+ efi_image_region_add(regs,
> > >>>>>+ &opt->CheckSum + 1,
> > >>>>>+ &opt->DataDirectory[ctidx], 0);
> > >>>>>+ efi_image_region_add(regs,
> > >>>>>+ &opt->DataDirectory[ctidx] + 1,
> > >>>>>+ efi + opt->SizeOfHeaders, 0);
> > >>>>>+ }
> > >>>>>+
> > >>>>>+ bytes_hashed = opt->SizeOfHeaders;
> > >>>>>+ align = opt->FileAlignment;
> > >>>>>+ authoff = opt->DataDirectory[ctidx].VirtualAddress;
> > >>>>>+ authsz = opt->DataDirectory[ctidx].Size;
> > >>>>>+ } else if (nt->OptionalHeader.Magic == IMAGE_NT_OPTIONAL_HDR32_MAGIC) {
> > >>>>>+ IMAGE_OPTIONAL_HEADER32 *opt = &nt->OptionalHeader;
> > >>>>>+
> > >>>>>+ efi_image_region_add(regs, efi, &opt->CheckSum, 0);
> > >>>>>+ efi_image_region_add(regs, &opt->CheckSum + 1,
> > >>>>>+ &opt->DataDirectory[ctidx], 0);
> > >>>>>+ efi_image_region_add(regs, &opt->DataDirectory[ctidx] + 1,
> > >>>>>+ efi + opt->SizeOfHeaders, 0);
> > >>>>>+
> > >>>>>+ bytes_hashed = opt->SizeOfHeaders;
> > >>>>>+ align = opt->FileAlignment;
> > >>>>>+ authoff = opt->DataDirectory[ctidx].VirtualAddress;
> > >>>>>+ authsz = opt->DataDirectory[ctidx].Size;
> > >>>>>+ } else {
> > >>>>>+ debug("%s: Invalid optional header magic %x\n", __func__,
> > >>>>>+ nt->OptionalHeader.Magic);
> > >>>>>+ goto err;
> > >>>>>+ }
> > >>>>>+
> > >>>>>+ /* 2. Sections */
> > >>>>>+ num_sections = nt->FileHeader.NumberOfSections;
> > >>>>>+ sections = (void *)((uint8_t *)&nt->OptionalHeader +
> > >>>>>+ nt->FileHeader.SizeOfOptionalHeader);
> > >>>>>+ sorted = calloc(sizeof(IMAGE_SECTION_HEADER *), num_sections);
> > >>>>>+ if (!sorted) {
> > >>>>>+ debug("%s: Out of memory\n", __func__);
> > >>>>>+ goto err;
> > >>>>>+ }
> > >>>>>+
> > >>>>>+ /*
> > >>>>>+ * Make sure the section list is in ascending order.
> > >>>>>+ * As we can assume that it is already ordered in most cases,
> > >>>>>+ * the following code is optimized for this.
> > >>>>>+ */
> > >>>>>+ for (sorted[0] = §ions[0], i = 1; i < num_sections; i++) {
> > >>>>
> > >>>>If sections[0] is not the lowest entry this function fails.
> > >>>>
> > >>>>Please, use qsort() supplied in lib/qsort.c.
> > >>>
> > >>>I'd rather fix my code as it is much simpler than qsort.
> > >>
> > >>Using qsort will result in a smaller code size. With qsort your code
> > >>will also be much easier to read.
> > >>
> > >>>
> > >>>>>+ if (sorted[i - 1]->VirtualAddress
> > >>>>>+ <= sections[i].VirtualAddress) {
> > >>>>>+ sorted[i] = §ions[i];
> > >>>>>+ } else {
> > >>>>>+ if (i == 1) {
> > >>>>>+ sorted[1] = sorted[0];
> > >>>>>+ sorted[0] = §ions[1];
> > >>>>>+ continue;
> > >>>>>+ }
> > >>>>>+
> > >>>>>+ sorted[i] = sorted[i - 1];
> > >>>>>+ for (j = i - 2; j >= 0; j--) {
> > >>>>>+ if (!j || sorted[j]->VirtualAddress
> > >>>>>+ <= sections[i].VirtualAddress) {
> > >>>>>+ sorted[j + 1] = §ions[i];
> > >>>>>+ continue;
> > >>>>>+ } else {
> > >>>>>+ sorted[j + 1] = sorted[j];
> > >>>>>+ }
> > >>>>>+ }
> > >>>>>+ }
> > >>>>>+ }
> > >>>>>+
> > >>>>>+ for (i = 0; i < num_sections; i++) {
> > >>>>>+ if (!sorted[i]->SizeOfRawData)
> > >>>>>+ continue;
> > >>>>>+
> > >>>>>+ size = (sorted[i]->SizeOfRawData + align - 1) & ~(align - 1);
> > >>>>>+ efi_image_region_add(regs, efi + sorted[i]->PointerToRawData,
> > >>>>>+ efi + sorted[i]->PointerToRawData + size,
> > >>>>>+ 0);
> > >>>>>+ debug("section[%d](%s): raw: 0x%x-0x%x, virt: %x-%x\n",
> > >>>>>+ i, sorted[i]->Name,
> > >>>>>+ sorted[i]->PointerToRawData,
> > >>>>>+ sorted[i]->PointerToRawData + size,
> > >>>>>+ sorted[i]->VirtualAddress,
> > >>>>>+ sorted[i]->VirtualAddress
> > >>>>>+ + sorted[i]->Misc.VirtualSize);
> > >>>>>+
> > >>>>>+ bytes_hashed += size;
> > >>>>>+ }
> > >>>>>+ free(sorted);
> > >>>>>+
> > >>>>>+ /* 3. Extra data excluding Certificates Table */
> > >>>>>+ if (bytes_hashed + authsz < len) {
> > >>>>>+ debug("extra data for hash: %lu\n",
> > >>>>>+ len - (bytes_hashed + authsz));
> > >>>>>+ efi_image_region_add(regs, efi + bytes_hashed,
> > >>>>>+ efi + len - authsz, 0);
> > >>>>>+ }
> > >>>>>+
> > >>>>>+ /* Return Certificates Table */
> > >>>>>+ if (authsz) {
> > >>>>>+ if (len < authoff + authsz) {
> > >>>>>+ debug("%s: Size for auth too large: %u >= %zu\n",
> > >>>>>+ __func__, authsz, len - authoff);
> > >>>>>+ goto err;
> > >>>>>+ }
> > >>>>>+ if (authsz < sizeof(*auth)) {
> > >>>>>+ debug("%s: Size for auth too small: %u < %zu\n",
> > >>>>>+ __func__, authsz, sizeof(*auth));
> > >>>>>+ goto err;
> > >>>>>+ }
> > >>>>>+ *auth = efi + authoff;
> > >>>>>+ *auth_len = authsz;
> > >>>>>+ debug("WIN_CERTIFICATE: 0x%x, size: 0x%x\n", authoff, authsz);
> > >>>>>+ } else {
> > >>>>>+ *auth = NULL;
> > >>>>>+ *auth_len = 0;
> > >>>>>+ }
> > >>>>>+
> > >>>>>+ *regp = regs;
> > >>>>>+
> > >>>>>+ return true;
> > >>>>>+
> > >>>>>+err:
> > >>>>>+ free(regs);
> > >>>>>+
> > >>>>>+ return false;
> > >>>>>+}
> > >>>>>+
> > >>>>>+/**
> > >>>>>+ * efi_image_unsigned_authenticate - authenticate unsigned image with
> > >>>>>+ * SHA256 hash
> > >>>>>+ * @regs: List of regions to be verified
> > >>>>>+ *
> > >>>>>+ * If an image is not signed, it doesn't have a signature. In this case,
> > >>>>>+ * its message digest is calculated and it will be compared with one of
> > >>>>>+ * hash values stored in signature databases.
> > >>>>>+ *
> > >>>>>+ * Return: true if authenticated, false if not
> > >>>>>+ */
> > >>>>>+static bool efi_image_unsigned_authenticate(struct efi_image_regions *regs)
> > >>>>>+{
> > >>>>>+ struct efi_signature_store *db = NULL, *dbx = NULL;
> > >>>>>+ bool ret = false;
> > >>>>>+
> > >>>>>+ dbx = efi_sigstore_parse_sigdb(L"dbx");
> > >>>>>+ if (!dbx) {
> > >>>>>+ debug("Getting signature database(dbx) failed\n");
> > >>>>>+ goto out;
> > >>>>>+ }
> > >>>>>+
> > >>>>>+ db = efi_sigstore_parse_sigdb(L"db");
> > >>>>>+ if (!db) {
> > >>>>>+ debug("Getting signature database(db) failed\n");
> > >>>>>+ goto out;
> > >>>>>+ }
> > >>>>>+
> > >>>>>+ /* try black-list first */
> > >>>>>+ if (efi_signature_verify_with_sigdb(regs, NULL, dbx, NULL)) {
> > >>>>>+ debug("Image is not signed and rejected by \"dbx\"\n");
> > >>>>>+ goto out;
> > >>>>>+ }
> > >>>>>+
> > >>>>>+ /* try white-list */
> > >>>>>+ if (efi_signature_verify_with_sigdb(regs, NULL, db, NULL))
> > >>>>>+ ret = true;
> > >>>>>+ else
> > >>>>>+ debug("Image is not signed and not found in \"db\" or \"dbx\"\n");
> > >>>>>+
> > >>>>>+out:
> > >>>>>+ efi_sigstore_free(db);
> > >>>>>+ efi_sigstore_free(dbx);
> > >>>>>+
> > >>>>>+ return ret;
> > >>>>>+}
> > >>>>>+
> > >>>>>+/**
> > >>>>>+ * efi_image_authenticate - verify a signature of signed image
> > >>>>>+ * @efi: Pointer to image
> > >>>>>+ * @len: Size of @efi
> > >>>>>+ *
> > >>>>>+ * A signed image should have its signature stored in a table of its PE header.
> > >>>>>+ * So if an image is signed and only if if its signature is verified using
> > >>>>>+ * signature databases, an image is authenticated.
> > >>>>>+ * If an image is not signed, its validity is checked by using
> > >>>>>+ * efi_image_unsigned_authenticated().
> > >>>>>+ * TODO:
> > >>>>>+ * When AuditMode==0, if the image's signature is not found in
> > >>>>>+ * the authorized database, or is found in the forbidden database,
> > >>>>>+ * the image will not be started and instead, information about it
> > >>>>>+ * will be placed in this table.
> > >>>>>+ * When AuditMode==1, an EFI_IMAGE_EXECUTION_INFO element is created
> > >>>>>+ * in the EFI_IMAGE_EXECUTION_INFO_TABLE for every certificate found
> > >>>>>+ * in the certificate table of every image that is validated.
> > >>>>>+ *
> > >>>>>+ * Return: true if authenticated, false if not
> > >>>>>+ */
> > >>>>>+static bool efi_image_authenticate(void *efi, size_t len)
> > >>>>>+{
> > >>>>>+ struct efi_image_regions *regs = NULL;
> > >>>>>+ WIN_CERTIFICATE *wincerts = NULL, *wincert;
> > >>>>>+ size_t wincerts_len;
> > >>>>>+ struct pkcs7_message *msg = NULL;
> > >>>>>+ struct efi_signature_store *db = NULL, *dbx = NULL;
> > >>>>>+ struct x509_certificate *cert = NULL;
> > >>>>>+ bool ret = false;
> > >>>>>+
> > >>>>>+ if (!efi_secure_boot_enabled())
> > >>>>>+ return true;
> > >>>>>+
> > >>>>>+ if (!efi_image_parse(efi, len, ®s, &wincerts,
> > >>>>>+ &wincerts_len)) {
> > >>>>>+ debug("Parsing PE executable image failed\n");
> > >>>>>+ return false;
> > >>>>>+ }
> > >>>>>+
> > >>>>>+ if (!wincerts) {
> > >>>>>+ /* The image is not signed */
> > >>>>>+ ret = efi_image_unsigned_authenticate(regs);
> > >>>>>+ free(regs);
> > >>>>>+
> > >>>>>+ return ret;
> > >>>>>+ }
> > >>>>>+
> > >>>>>+ /*
> > >>>>>+ * verify signature using db and dbx
> > >>>>>+ */
> > >>>>>+ db = efi_sigstore_parse_sigdb(L"db");
> > >>>>>+ if (!db) {
> > >>>>>+ debug("Getting signature database(db) failed\n");
> > >>>>>+ goto err;
> > >>>>>+ }
> > >>>>>+
> > >>>>>+ dbx = efi_sigstore_parse_sigdb(L"dbx");
> > >>>>>+ if (!dbx) {
> > >>>>>+ debug("Getting signature database(dbx) failed\n");
> > >>>>>+ goto err;
> > >>>>>+ }
> > >>>>>+
> > >>>>>+ /* go through WIN_CERTIFICATE list */
> > >>>>>+ for (wincert = wincerts;
> > >>>>>+ (void *)wincert < (void *)wincerts + wincerts_len;
> > >>>>>+ wincert = (void *)wincert + ALIGN(wincert->dwLength, 8)) {
> > >>>>>+ if (wincert->dwLength < sizeof(*wincert)) {
> > >>>>>+ debug("%s: dwLength too small: %u < %zu\n",
> > >>>>>+ __func__, wincert->dwLength, sizeof(*wincert));
> > >>>>>+ goto err;
> > >>>>>+ }
> > >>>>>+ msg = pkcs7_parse_message((void *)wincert + sizeof(*wincert),
> > >>>>>+ wincert->dwLength - sizeof(*wincert));
> > >>>>>+ if (!msg) {
> > >>>>>+ debug("Parsing image's signature failed\n");
> > >>>>>+ goto err;
> > >>>>>+ }
> > >>>>>+
> > >>>>>+ /* try black-list first */
> > >>>>>+ if (efi_signature_verify_with_sigdb(regs, msg, dbx, NULL)) {
> > >>>>>+ debug("Signature was rejected by \"dbx\"\n");
> > >>>>>+ goto err;
> > >>>>>+ }
> > >>>>>+
> > >>>>>+ if (!efi_signature_verify_signers(msg, dbx)) {
> > >>>>>+ debug("Signer was rejected by \"dbx\"\n");
> > >>>>>+ goto err;
> > >>>>>+ } else {
> > >>>>>+ ret = true;
> > >>>>>+ }
> > >>>>>+
> > >>>>>+ /* try white-list */
> > >>>>>+ if (!efi_signature_verify_with_sigdb(regs, msg, db, &cert)) {
> > >>>>>+ debug("Verifying signature with \"db\" failed\n");
> > >>>>>+ goto err;
> > >>>>>+ } else {
> > >>>>>+ ret = true;
> > >>>>>+ }
> > >>>>>+
> > >>>>>+ if (!efi_signature_verify_cert(cert, dbx)) {
> > >>>>>+ debug("Certificate was rejected by \"dbx\"\n");
> > >>>>>+ goto err;
> > >>>>>+ } else {
> > >>>>>+ ret = true;
> > >>>>>+ }
> > >>>>>+ }
> > >>>>>+
> > >>>>>+err:
> > >>>>>+ x509_free_certificate(cert);
> > >>>>>+ efi_sigstore_free(db);
> > >>>>>+ efi_sigstore_free(dbx);
> > >>>>>+ pkcs7_free_message(msg);
> > >>>>>+ free(regs);
> > >>>>>+
> > >>>>>+ return ret;
> > >>>>>+}
> > >>>>>+#else
> > >>>>>+static bool efi_image_authenticate(void *efi, size_t len)
> > >>>>>+{
> > >>>>>+ return true;
> > >>>>>+}
> > >>>>>+#endif /* CONFIG_EFI_SECURE_BOOT */
> > >>>>>+
> > >>>>> /**
> > >>>>> * efi_load_pe() - relocate EFI binary
> > >>>>> *
> > >>>>>@@ -216,7 +579,8 @@ static void efi_set_code_and_data_type(
> > >>>>> * @loaded_image_info: loaded image protocol
> > >>>>> * Return: status code
> > >>>>> */
> > >>>>>-efi_status_t efi_load_pe(struct efi_loaded_image_obj *handle, void *efi,
> > >>>>>+efi_status_t efi_load_pe(struct efi_loaded_image_obj *handle,
> > >>>>>+ void *efi, size_t efi_size,
> > >>>>> struct efi_loaded_image *loaded_image_info)
> > >>>>> {
> > >>>>> IMAGE_NT_HEADERS32 *nt;
> > >>>>>@@ -231,17 +595,57 @@ efi_status_t efi_load_pe(struct efi_loaded_image_obj *handle, void *efi,
> > >>>>> uint64_t image_base;
> > >>>>> unsigned long virt_size = 0;
> > >>>>> int supported = 0;
> > >>>>>+ void *new_efi = NULL;
> > >>>>>+ size_t new_efi_size;
> > >>>>>+ efi_status_t ret;
> > >>>>>+
> > >>>>>+ /*
> > >>>>>+ * Size must be 8-byte aligned and the trailing bytes must be
> > >>>>>+ * zero'ed. Otherwise hash value may be incorrect.
> > >>>>>+ */
> > >>>>>+ if (efi_size & 0x7) {
> > >>>>>+ new_efi_size = (efi_size + 0x7) & ~0x7ULL;
> > >>>>>+ new_efi = calloc(new_efi_size, 1);
> > >>>>>+ if (!new_efi)
> > >>>>>+ return EFI_OUT_OF_RESOURCES;
> > >>>>>+ memcpy(new_efi, efi, efi_size);
> > >>>>>+ efi = new_efi;
> > >>>>>+ efi_size = new_efi_size;
> > >>>>>+ }
> > >>>>>+
> > >>>>>+ /* Sanity check for a file header */
> > >>>>>+ if (efi_size < sizeof(*dos)) {
> > >>>>>+ printf("%s: Truncated DOS Header\n", __func__);
> > >>>>>+ ret = EFI_LOAD_ERROR;
> > >>>>>+ goto err;
> > >>>>>+ }
> > >>>>>
> > >>>>> dos = efi;
> > >>>>> if (dos->e_magic != IMAGE_DOS_SIGNATURE) {
> > >>>>> printf("%s: Invalid DOS Signature\n", __func__);
> > >>>>>- return EFI_LOAD_ERROR;
> > >>>>>+ ret = EFI_LOAD_ERROR;
> > >>>>>+ goto err;
> > >>>>>+ }
> > >>>>>+
> > >>>>>+ /* assume sizeof(IMAGE_NT_HEADERS32) <= sizeof(IMAGE_NT_HEADERS64) */
> > >>>>>+ if (efi_size < dos->e_lfanew + sizeof(IMAGE_NT_HEADERS32)) {
> > >>>>>+ printf("%s: Invalid offset for Extended Header\n", __func__);
> > >>>>>+ ret = EFI_LOAD_ERROR;
> > >>>>>+ goto err;
> > >>>>> }
> > >>>>>
> > >>>>> nt = (void *) ((char *)efi + dos->e_lfanew);
> > >>>>>+ if ((nt->OptionalHeader.Magic == IMAGE_NT_OPTIONAL_HDR64_MAGIC) &&
> > >>>>>+ (efi_size < dos->e_lfanew + sizeof(IMAGE_NT_HEADERS64))) {
> > >>>>>+ printf("%s: Invalid offset for Extended Header\n", __func__);
> > >>>>>+ ret = EFI_LOAD_ERROR;
> > >>>>>+ goto err;
> > >>>>>+ }
> > >>>>>+
> > >>>>> if (nt->Signature != IMAGE_NT_SIGNATURE) {
> > >>>>> printf("%s: Invalid NT Signature\n", __func__);
> > >>>>>- return EFI_LOAD_ERROR;
> > >>>>>+ ret = EFI_LOAD_ERROR;
> > >>>>>+ goto err;
> > >>>>> }
> > >>>>>
> > >>>>> for (i = 0; machines[i]; i++)
> > >>>>>@@ -253,14 +657,29 @@ efi_status_t efi_load_pe(struct efi_loaded_image_obj *handle, void *efi,
> > >>>>> if (!supported) {
> > >>>>> printf("%s: Machine type 0x%04x is not supported\n",
> > >>>>> __func__, nt->FileHeader.Machine);
> > >>>>>- return EFI_LOAD_ERROR;
> > >>>>>+ ret = EFI_LOAD_ERROR;
> > >>>>>+ goto err;
> > >>>>> }
> > >>>>>
> > >>>>>- /* Calculate upper virtual address boundary */
> > >>>>> num_sections = nt->FileHeader.NumberOfSections;
> > >>>>> sections = (void *)&nt->OptionalHeader +
> > >>>>> nt->FileHeader.SizeOfOptionalHeader;
> > >>>>>
> > >>>>>+ if (efi_size < ((void *)sections + sizeof(sections[0]) * num_sections
> > >>>>>+ - efi)) {
> > >>>>>+ printf("%s: Invalid number of sections: %d\n",
> > >>>>>+ __func__, num_sections);
> > >>>>>+ ret = EFI_LOAD_ERROR;
> > >>>>>+ goto err;
> > >>>>>+ }
> > >>>>>+
> > >>>>>+ /* Authenticate an image */
> > >>>>>+ if (!efi_image_authenticate(efi, efi_size)) {
> > >>>>>+ ret = EFI_ACCESS_DENIED;
> > >>>>
> > >>>>According to the UEFI specification LoadImage() should return
> > >>>>EFI_SECURITY_VIOLATION in this case.
> > >>>
> > >>>Will check.
> > >>>
> > >>>>Further behaviour should depend on variables AuditMode and DeployedMode.
> > >>>>
> > >>>>If authentication fails, you must update the configuration table
> > >>>>identified by EFI_IMAGE_SECURITY_DATABASE_GUID containing the Image
> > >>>>Execution Information. If the authentication succeeds you may enter a
> > >>>>record.
> > >>>>
> > >>>>It seems to me that in your patch series you are not creating the
> > >>>>configuration table at all.
> > >>>
> > >>>>From the very beginning of my submissions, I have clearly said
> > >>>that this feature was *beyond the scope* in my current series.
> > >>>===8<===
> > >>>Unsupported features: (marked as TODO in most cases in the source code,
> > >>> and won't be included in this series)
> > >>>(snip)
> > >>>* recording rejected images in EFI_IMAGE_EXECUTION_INFO_TABLE
> > >>>===>8===
> > >>>
> > >>>>The content of the Image Execution Information Table should be used to
> > >>>>decide if StartImage() may start an image. This is still missing in the
> > >>>>patch series.
> > >>>
> > >>>No.
> > >>>Whether such information be in configuration table or not,
> > >>>non-authenticated image won't be started if secure boot is in force.
> > >>
> > >>I cannot find any such check in efi_start_image().
> > >
> > >Because my current code *rejects* any unauthenticated images being loaded
> > >and return no valid pointer to image handle.
> > >If an error code in this case is changed and efi_load_image() still returns
> > >a valid handle, we will also have to modify efi_start_image().
> > >
> > >>Please, provide an implementation that complies with the UEFI specification:
> > >>
> > >>"The information is used to create the Image Execution Information
> > >>Table, which is added to the EFI System Configuration Table and assigned
> > >>the GUID EFI_IMAGE_SECURITY_DATABASE_GUID."
> > >
> > >Regarding "Image Execution Information Table", Heavily disagree.
> > >The current UEFI code, not only mine but yours, has bunch of unimplemented
> > >features.
> >
> > What is the point of this patch if efi_start_image() does not provide
> > any check?
>
> As I said in the previous reply,
> efi_load_image() doesn't return any valid handle for unauthenticated binaries
> in my *current* implementation, efi_start_image() has no chance to execute them.
> No check is necessary. That's it.
I double-checked edk2 code as well as UEFI specification, and found
a couple of insights:
a. EDK2 code has several internal help functions for verifications.
If they fail to find any valid signature in db's, the status (or
internal error code) is set to ACCESS_DENIED.
Then, at the end of verification, if the status is not EFI_SUCCESS,
the return code is anyhow rewritten to SECURITY_VIOLATION.
(That is why my code returns ACCESS_DENIED right now.)
b. While UEFI specification requires that efiLoadImage() return
SECURITY_VIOLATION if "the image signature is not valid,"
it doesn't mention if a handle to the image be returned or not.
c. "Status Codes Returned" can also read that it depends on
"platform policy" if we return ACCESS_DENIED or SECURITY_VIOLATION.
But the policy may be vendor/platform, or even U-Boot specific as
UEFI specification doesn't mention anything about that.
Thinking of the fact that we don't have any consensus nor implementation
of "policy" yet, I believe that the best solution for now is:
efi_load_image() return EFI_SECURITY_VIOLATION if the image signature
is not verified and does *not* return a handle to image.
This behavior is safe and yet won't prevent us from additionally implementing
"policy" framework as well as image information table when adding
Audit/DeployedMode support in the future.
Can you agree?
-Takahiro Akashi
> -Takahiro Akashi
>
> > Best regards
> >
> > Heinrich
> >
> > >
> > >-Takahiro Akashi
> > >
> > >
> > >>Best regards
> > >>
> > >>Heinrich
> > >>
> > >>>
> > >>>Thanks,
> > >>>-Takahiro Akashi
> > >>>
> > >>>>
> > >>>>Best regards
> > >>>>
> > >>>>Heinrich
> > >>>>
> > >>>>>+ goto err;
> > >>>>>+ }
> > >>>>>+
> > >>>>>+ /* Calculate upper virtual address boundary */
> > >>>>> for (i = num_sections - 1; i >= 0; i--) {
> > >>>>> IMAGE_SECTION_HEADER *sec = §ions[i];
> > >>>>> virt_size = max_t(unsigned long, virt_size,
> > >>>>>@@ -279,7 +698,8 @@ efi_status_t efi_load_pe(struct efi_loaded_image_obj *handle, void *efi,
> > >>>>> if (!efi_reloc) {
> > >>>>> printf("%s: Could not allocate %lu bytes\n",
> > >>>>> __func__, virt_size);
> > >>>>>- return EFI_OUT_OF_RESOURCES;
> > >>>>>+ ret = EFI_OUT_OF_RESOURCES;
> > >>>>>+ goto err;
> > >>>>> }
> > >>>>> handle->entry = efi_reloc + opt->AddressOfEntryPoint;
> > >>>>> rel_size = opt->DataDirectory[rel_idx].Size;
> > >>>>>@@ -295,7 +715,8 @@ efi_status_t efi_load_pe(struct efi_loaded_image_obj *handle, void *efi,
> > >>>>> if (!efi_reloc) {
> > >>>>> printf("%s: Could not allocate %lu bytes\n",
> > >>>>> __func__, virt_size);
> > >>>>>- return EFI_OUT_OF_RESOURCES;
> > >>>>>+ ret = EFI_OUT_OF_RESOURCES;
> > >>>>>+ goto err;
> > >>>>> }
> > >>>>> handle->entry = efi_reloc + opt->AddressOfEntryPoint;
> > >>>>> rel_size = opt->DataDirectory[rel_idx].Size;
> > >>>>>@@ -304,13 +725,16 @@ efi_status_t efi_load_pe(struct efi_loaded_image_obj *handle, void *efi,
> > >>>>> } else {
> > >>>>> printf("%s: Invalid optional header magic %x\n", __func__,
> > >>>>> nt->OptionalHeader.Magic);
> > >>>>>- return EFI_LOAD_ERROR;
> > >>>>>+ ret = EFI_LOAD_ERROR;
> > >>>>>+ goto err;
> > >>>>> }
> > >>>>>
> > >>>>> /* Copy PE headers */
> > >>>>>- memcpy(efi_reloc, efi, sizeof(*dos) + sizeof(*nt)
> > >>>>>- + nt->FileHeader.SizeOfOptionalHeader
> > >>>>>- + num_sections * sizeof(IMAGE_SECTION_HEADER));
> > >>>>>+ memcpy(efi_reloc, efi,
> > >>>>>+ sizeof(*dos)
> > >>>>>+ + sizeof(*nt)
> > >>>>>+ + nt->FileHeader.SizeOfOptionalHeader
> > >>>>>+ + num_sections * sizeof(IMAGE_SECTION_HEADER));
> > >>>>>
> > >>>>> /* Load sections into RAM */
> > >>>>> for (i = num_sections - 1; i >= 0; i--) {
> > >>>>>@@ -327,7 +751,8 @@ efi_status_t efi_load_pe(struct efi_loaded_image_obj *handle, void *efi,
> > >>>>> (unsigned long)image_base) != EFI_SUCCESS) {
> > >>>>> efi_free_pages((uintptr_t) efi_reloc,
> > >>>>> (virt_size + EFI_PAGE_MASK) >> EFI_PAGE_SHIFT);
> > >>>>>- return EFI_LOAD_ERROR;
> > >>>>>+ ret = EFI_LOAD_ERROR;
> > >>>>>+ goto err;
> > >>>>> }
> > >>>>>
> > >>>>> /* Flush cache */
> > >>>>>@@ -340,4 +765,9 @@ efi_status_t efi_load_pe(struct efi_loaded_image_obj *handle, void *efi,
> > >>>>> loaded_image_info->image_size = virt_size;
> > >>>>>
> > >>>>> return EFI_SUCCESS;
> > >>>>>+
> > >>>>>+err:
> > >>>>>+ free(new_efi);
> > >>>>>+
> > >>>>>+ return ret;
> > >>>>> }
> > >>>>>
> > >>>>
> > >>>
> > >>
> > >
> >
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