@@ -765,6 +765,8 @@ struct efi_signature_store {
struct x509_certificate;
struct pkcs7_message;
+bool efi_signature_lookup_digest(struct efi_image_regions *regs,
+ struct efi_signature_store *db);
bool efi_signature_verify_one(struct efi_image_regions *regs,
struct pkcs7_message *msg,
struct efi_signature_store *db);
@@ -449,16 +449,16 @@ static bool efi_image_unsigned_authenticate(struct efi_image_regions *regs)
}
/* try black-list first */
- if (efi_signature_verify_one(regs, NULL, dbx)) {
- EFI_PRINT("Image is not signed and rejected by \"dbx\"\n");
+ if (efi_signature_lookup_digest(regs, dbx)) {
+ EFI_PRINT("Image is not signed and its digest found in \"dbx\"\n");
goto out;
}
/* try white-list */
- if (efi_signature_verify_one(regs, NULL, db))
+ if (efi_signature_lookup_digest(regs, db))
ret = true;
else
- EFI_PRINT("Image is not signed and not found in \"db\" or \"dbx\"\n");
+ EFI_PRINT("Image is not signed and its digest not found in \"db\" or \"dbx\"\n");
out:
efi_sigstore_free(db);
@@ -606,6 +606,25 @@ static bool efi_image_authenticate(void *efi, size_t efi_size)
continue;
}
+ /*
+ * NOTE:
+ * UEFI specification defines two signature types possible
+ * in signature database:
+ * a. x509 certificate, where a signature in image is
+ * a message digest encrypted by RSA public key
+ * (EFI_CERT_X509_GUID)
+ * b. bare hash value of message digest
+ * (EFI_CERT_SHAxxx_GUID)
+ *
+ * efi_signature_verify() handles case (a), while
+ * efi_signature_lookup_digest() handles case (b).
+ *
+ * There is a third type:
+ * c. message digest of a certificate
+ * (EFI_CERT_X509_SHAAxxx_GUID)
+ * This type of signature is used only in revocation list
+ * (dbx) and handled as part of efi_signatgure_verify().
+ */
/* try black-list first */
if (efi_signature_verify_one(regs, msg, dbx)) {
EFI_PRINT("Signature was rejected by \"dbx\"\n");
@@ -617,11 +636,22 @@ static bool efi_image_authenticate(void *efi, size_t efi_size)
goto err;
}
- /* try white-list */
- if (!efi_signature_verify_with_sigdb(regs, msg, db, dbx)) {
- EFI_PRINT("Signature was not verified by \"db\"\n");
+ if (efi_signature_lookup_digest(regs, dbx)) {
+ EFI_PRINT("Image's digest was found in \"dbx\"\n");
goto err;
}
+
+ /* try white-list */
+ if (efi_signature_verify_with_sigdb(regs, msg, db, dbx))
+ continue;
+
+ debug("Signature was not verified by \"db\"\n");
+
+ if (efi_signature_lookup_digest(regs, db))
+ continue;
+
+ debug("Image's digest was not found in \"db\" or \"dbx\"\n");
+ goto err;
}
ret = true;
@@ -199,55 +199,43 @@ out:
}
/**
- * efi_signature_verify_with_list - verify a signature with signature list
- * @regs: List of regions to be authenticated
- * @msg: Signature
- * @signed_info: Pointer to PKCS7's signed_info
- * @siglist: Signature list for certificates
- * @valid_cert: x509 certificate that verifies this signature
+ * efi_signature_lookup_digest - search for an image's digest in sigdb
+ * @regs: List of regions to be authenticated
+ * @db: Signature database for trusted certificates
*
- * Signature pointed to by @signed_info against image pointed to by @regs
- * is verified by signature list pointed to by @siglist.
- * Signature database is a simple concatenation of one or more
- * signature list(s).
+ * A message digest of image pointed to by @regs is calculated and
+ * its hash value is compared to entries in signature database pointed
+ * to by @db.
*
- * Return: true if signature is verified, false if not
+ * Return: true if found, false if not
*/
-static
-bool efi_signature_verify_with_list(struct efi_image_regions *regs,
- struct pkcs7_message *msg,
- struct pkcs7_signed_info *signed_info,
- struct efi_signature_store *siglist,
- struct x509_certificate **valid_cert)
+bool efi_signature_lookup_digest(struct efi_image_regions *regs,
+ struct efi_signature_store *db)
{
- struct x509_certificate *cert;
+ struct efi_signature_store *siglist;
struct efi_sig_data *sig_data;
- bool verified = false;
+ void *hash = NULL;
+ size_t size = 0;
+ bool found = false;
- EFI_PRINT("%s: Enter, %p, %p, %p, %p\n", __func__,
- regs, signed_info, siglist, valid_cert);
+ EFI_PRINT("%s: Enter, %p, %p\n", __func__, regs, db);
- if (!signed_info) {
- void *hash = NULL;
- size_t size;
+ if (!regs || !db || !db->sig_data_list)
+ goto out;
- EFI_PRINT("%s: unsigned image\n", __func__);
- /*
- * verify based on calculated hash value
- * TODO: support other hash algorithms
- */
+ for (siglist = db; siglist; siglist = siglist->next) {
+ /* TODO: support other hash algorithms */
if (guidcmp(&siglist->sig_type, &efi_guid_sha256)) {
EFI_PRINT("Digest algorithm is not supported: %pUl\n",
&siglist->sig_type);
- goto out;
+ break;
}
if (!efi_hash_regions(regs->reg, regs->num, &hash, &size)) {
- EFI_PRINT("Digesting unsigned image failed\n");
- goto out;
+ EFI_PRINT("Digesting an image failed\n");
+ break;
}
- /* go through the list */
for (sig_data = siglist->sig_data_list; sig_data;
sig_data = sig_data->next) {
#ifdef DEBUG
@@ -255,18 +243,52 @@ bool efi_signature_verify_with_list(struct efi_image_regions *regs,
print_hex_dump(" ", DUMP_PREFIX_OFFSET, 16, 1,
sig_data->data, sig_data->size, false);
#endif
- if ((sig_data->size == size) &&
+ if (sig_data->size == size &&
!memcmp(sig_data->data, hash, size)) {
- verified = true;
+ found = true;
free(hash);
goto out;
}
}
+
free(hash);
- goto out;
+ hash = NULL;
}
- EFI_PRINT("%s: signed image\n", __func__);
+out:
+ EFI_PRINT("%s: Exit, found: %d\n", __func__, found);
+ return found;
+}
+
+/**
+ * efi_signature_verify_with_list - verify a signature with signature list
+ * @regs: List of regions to be authenticated
+ * @msg: Signature
+ * @signed_info: Pointer to PKCS7's signed_info
+ * @siglist: Signature list for certificates
+ * @valid_cert: x509 certificate that verifies this signature
+ *
+ * Signature pointed to by @signed_info against image pointed to by @regs
+ * is verified by signature list pointed to by @siglist.
+ * Signature database is a simple concatenation of one or more
+ * signature list(s).
+ *
+ * Return: true if signature is verified, false if not
+ */
+static
+bool efi_signature_verify_with_list(struct efi_image_regions *regs,
+ struct pkcs7_message *msg,
+ struct pkcs7_signed_info *signed_info,
+ struct efi_signature_store *siglist,
+ struct x509_certificate **valid_cert)
+{
+ struct x509_certificate *cert;
+ struct efi_sig_data *sig_data;
+ bool verified = false;
+
+ EFI_PRINT("%s: Enter, %p, %p, %p, %p\n", __func__,
+ regs, signed_info, siglist, valid_cert);
+
if (guidcmp(&siglist->sig_type, &efi_guid_cert_x509)) {
EFI_PRINT("Signature type is not supported: %pUl\n",
&siglist->sig_type);
@@ -413,19 +435,6 @@ bool efi_signature_verify_one(struct efi_image_regions *regs,
if (!db->sig_data_list)
goto out;
- /* for unsigned image */
- if (!msg) {
- EFI_PRINT("%s: Verify unsigned image with db\n", __func__);
- for (siglist = db; siglist; siglist = siglist->next)
- if (efi_signature_verify_with_list(regs, NULL, NULL,
- siglist, &cert)) {
- verified = true;
- break;
- }
- goto out;
- }
-
- /* for signed image or variable */
EFI_PRINT("%s: Verify signed image with db\n", __func__);
for (sinfo = msg->signed_infos; sinfo; sinfo = sinfo->next) {
EFI_PRINT("Signed Info: digest algo: %s, pkey algo: %s\n",
@@ -469,26 +478,9 @@ bool efi_signature_verify_with_sigdb(struct efi_image_regions *regs,
EFI_PRINT("%s: Enter, %p, %p, %p, %p\n", __func__, regs, msg, db, dbx);
- if (!db)
- goto out;
-
- if (!db->sig_data_list)
+ if (!regs || !msg || !db || !db->sig_data_list)
goto out;
- /* for unsigned image */
- if (!msg) {
- EFI_PRINT("%s: Verify unsigned image with db\n", __func__);
- for (siglist = db; siglist; siglist = siglist->next)
- if (efi_signature_verify_with_list(regs, NULL, NULL,
- siglist, &cert)) {
- verified = true;
- break;
- }
- goto out;
- }
-
- /* for signed image or variable */
- EFI_PRINT("%s: Verify signed image with db\n", __func__);
for (info = msg->signed_infos; info; info = info->next) {
EFI_PRINT("Signed Info: digest algo: %s, pkey algo: %s\n",
info->sig->hash_algo, info->sig->pkey_algo);
In case that a type of certificate in "db" or "dbx" is EFI_CERT_X509_SHA256_GUID, it is actually not a certificate which contains a public key for RSA decryption, but a digest of image to be loaded. If the value matches to a value calculated from a given binary image, it is granted for loading. With this patch, common digest check code, which used to be used for unsigned image verification, will be extracted from efi_signature_verify_with_sigdb() into efi_signature_lookup_digest(), and extra step for digest check will be added to efi_image_authenticate(). Signed-off-by: AKASHI Takahiro <takahiro.akashi at linaro.org> --- include/efi_loader.h | 2 + lib/efi_loader/efi_image_loader.c | 44 ++++++++-- lib/efi_loader/efi_signature.c | 128 ++++++++++++++---------------- 3 files changed, 99 insertions(+), 75 deletions(-)