efi_loader: don't load signature database from file

The UEFI specification requires that the signature database may only be
stored in tamper-resistant storage. So these variable may not be read
from an unsigned file.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>

diff --git a/include/efi_variable.h b/include/efi_variable.h
index 4623a64..2d97655 100644 (file)
--- a/include/efi_variable.h
+++ b/include/efi_variable.h
@@ -161,10 +161,13 @@ efi_status_t __maybe_unused efi_var_collect(struct efi_var_file **bufp, loff_t *
 /**
  * efi_var_restore() - restore EFI variables from buffer
  *
+ * Only if @safe is set secure boot related variables will be restored.
+ *
  * @buf:       buffer
+ * @safe:      restoring from tamper-resistant storage
  * Return:     status code
  */
-efi_status_t efi_var_restore(struct efi_var_file *buf);
+efi_status_t efi_var_restore(struct efi_var_file *buf, bool safe);
 
 /**
  * efi_var_from_file() - read variables from file

diff --git a/lib/efi_loader/efi_var_common.c b/lib/efi_loader/efi_var_common.c
index 3d92afe..005c03e 100644 (file)
--- a/lib/efi_loader/efi_var_common.c
+++ b/lib/efi_loader/efi_var_common.c
@@ -32,10 +32,8 @@ static const struct efi_auth_var_name_type name_type[] = {
        {u"KEK", &efi_global_variable_guid, EFI_AUTH_VAR_KEK},
        {u"db",  &efi_guid_image_security_database, EFI_AUTH_VAR_DB},
        {u"dbx",  &efi_guid_image_security_database, EFI_AUTH_VAR_DBX},
-       /* not used yet
        {u"dbt",  &efi_guid_image_security_database, EFI_AUTH_VAR_DBT},
        {u"dbr",  &efi_guid_image_security_database, EFI_AUTH_VAR_DBR},
-       */
 };
 
 static bool efi_secure_boot;

diff --git a/lib/efi_loader/efi_var_file.c b/lib/efi_loader/efi_var_file.c
index de076b8..c7c6805 100644 (file)
--- a/lib/efi_loader/efi_var_file.c
+++ b/lib/efi_loader/efi_var_file.c
@@ -148,9 +148,10 @@ error:
 #endif
 }
 
-efi_status_t efi_var_restore(struct efi_var_file *buf)
+efi_status_t efi_var_restore(struct efi_var_file *buf, bool safe)
 {
        struct efi_var_entry *var, *last_var;
+       u16 *data;
        efi_status_t ret;
 
        if (buf->reserved || buf->magic != EFI_VAR_FILE_MAGIC ||
@@ -160,21 +161,29 @@ efi_status_t efi_var_restore(struct efi_var_file *buf)
                return EFI_INVALID_PARAMETER;
        }
 
-       var = buf->var;
        last_var = (struct efi_var_entry *)((u8 *)buf + buf->length);
-       while (var < last_var) {
-               u16 *data = var->name + u16_strlen(var->name) + 1;
-
-               if (var->attr & EFI_VARIABLE_NON_VOLATILE && var->length) {
-                       ret = efi_var_mem_ins(var->name, &var->guid, var->attr,
-                                             var->length, data, 0, NULL,
-                                             var->time);
-                       if (ret != EFI_SUCCESS)
-                               log_err("Failed to set EFI variable %ls\n",
-                                       var->name);
-               }
-               var = (struct efi_var_entry *)
-                     ALIGN((uintptr_t)data + var->length, 8);
+       for (var = buf->var; var < last_var;
+            var = (struct efi_var_entry *)
+                  ALIGN((uintptr_t)data + var->length, 8)) {
+
+               data = var->name + u16_strlen(var->name) + 1;
+
+               /*
+                * Secure boot related and non-volatile variables shall only be
+                * restored from U-Boot's preseed.
+                */
+               if (!safe &&
+                   (efi_auth_var_get_type(var->name, &var->guid) !=
+                    EFI_AUTH_VAR_NONE ||
+                    !(var->attr & EFI_VARIABLE_NON_VOLATILE)))
+                       continue;
+               if (!var->length)
+                       continue;
+               ret = efi_var_mem_ins(var->name, &var->guid, var->attr,
+                                     var->length, data, 0, NULL,
+                                     var->time);
+               if (ret != EFI_SUCCESS)
+                       log_err("Failed to set EFI variable %ls\n", var->name);
        }
        return EFI_SUCCESS;
 }
@@ -213,7 +222,7 @@ efi_status_t efi_var_from_file(void)
                log_err("Failed to load EFI variables\n");
                goto error;
        }
-       if (buf->length != len || efi_var_restore(buf) != EFI_SUCCESS)
+       if (buf->length != len || efi_var_restore(buf, false) != EFI_SUCCESS)
                log_err("Invalid EFI variables file\n");
 error:
        free(buf);

diff --git a/lib/efi_loader/efi_variable.c b/lib/efi_loader/efi_variable.c
index ba0874e..a7d305f 100644 (file)
--- a/lib/efi_loader/efi_variable.c
+++ b/lib/efi_loader/efi_variable.c
@@ -426,7 +426,7 @@ efi_status_t efi_init_variables(void)
 
        if (IS_ENABLED(CONFIG_EFI_VARIABLES_PRESEED)) {
                ret = efi_var_restore((struct efi_var_file *)
-                                     __efi_var_file_begin);
+                                     __efi_var_file_begin, true);
                if (ret != EFI_SUCCESS)
                        log_err("Invalid EFI variable seed\n");
        }