> Assuming uint8 remains - should not you check that variable size is exactly 1
> byte in this case?
There are reports of a buggy firmware returning 4 bytes size for uint8
variables, however did not encounter them myself.
> Do we really need unit8 at all? "hex" already provides exactly the same
> functionality, not? Do you think there are cases when uint8 is really
> required?
Well, when checking for SecureBoot variable in grub configuration file
hex mode makes it look weird and creates a point of confusion. For
example to check if SecureBoot (suppose the result of the our command
is stored in secure_boot env variable in hex mode) is enabled one
should write:
if [ secure_boot = "01" ]
...
uint8 just allows to do a more straightforward config
if [ secure_boot = 1] - this case would be false for hex mode -
possible security breach
...
Added goto err in the module as pointed, see patch below. I will do a
follow-up patch for documentation once we get this confirmed.
diff --git a/grub-core/Makefile.core.def b/grub-core/Makefile.core.def
index 0cc40bb..aa7b927 100644
--- a/grub-core/Makefile.core.def
+++ b/grub-core/Makefile.core.def
@@ -735,6 +735,12 @@ module = {
};
module = {
+ name = efivar;
+ efi = commands/efi/efivar.c;
+ enable = efi;
+};
+
+module = {
name = blocklist;
common = commands/blocklist.c;
};
diff --git a/grub-core/commands/efi/efivar.c b/grub-core/commands/efi/efivar.c
new file mode 100644
index 0000000..7f5a957
--- /dev/null
+++ b/grub-core/commands/efi/efivar.c
@@ -0,0 +1,251 @@
+/* efivar.c - Read EFI global variables. */
+/*
+ * GRUB -- GRand Unified Bootloader
+ * Copyright (C) 2015 Free Software Foundation, Inc.
+ * Copyright (C) 2015 CloudFlare, Inc.
+ *
+ * GRUB is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * GRUB is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with GRUB. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <grub/types.h>
+#include <grub/mm.h>
+#include <grub/misc.h>
+#include <grub/efi/api.h>
+#include <grub/efi/efi.h>
+#include <grub/extcmd.h>
+#include <grub/env.h>
+#include <grub/lib/hexdump.h>
+
+GRUB_MOD_LICENSE ("GPLv3+");
+
+static const struct grub_arg_option options[] = {
+ {"format", 'f', GRUB_ARG_OPTION_OPTIONAL, N_("Parse EFI_VAR in
specific format (hex, uint8, ascii, raw, dump). Default: hex."),
N_("FORMAT"), ARG_TYPE_STRING},
+ {"set", 's', GRUB_ARG_OPTION_OPTIONAL, N_("Save parsed result to
environment variable (does not work with dump)."), N_("ENV_VAR"),
ARG_TYPE_STRING},
+ {0, 0, 0, 0, 0, 0}
+};
+
+enum efi_var_type
+ {
+ EFI_VAR_ASCII = 0,
+ EFI_VAR_RAW,
+ EFI_VAR_UINT8,
+ EFI_VAR_HEX,
+ EFI_VAR_DUMP,
+ EFI_VAR_INVALID = -1
+ };
+
+static enum efi_var_type
+parse_efi_var_type (const char *type)
+{
+ if (!grub_strncmp (type, "ascii", sizeof("ascii")))
+ return EFI_VAR_ASCII;
+
+ if (!grub_strncmp (type, "raw", sizeof("raw")))
+ return EFI_VAR_ASCII;
+
+ if (!grub_strncmp (type, "uint8", sizeof("uint8")))
+ return EFI_VAR_UINT8;
+
+ if (!grub_strncmp (type, "hex", sizeof("hex")))
+ return EFI_VAR_HEX;
+
+ if (!grub_strncmp (type, "dump", sizeof("dump")))
+ return EFI_VAR_DUMP;
+
+ return EFI_VAR_INVALID;
+}
+
+static int
+grub_print_ascii (char *str, char c)
+{
+ if (grub_iscntrl (c))
+ {
+ switch (c)
+ {
+ case '\0':
+ str[0] = '\\';
+ str[1] = '0';
+ return 2;
+
+ case '\a':
+ str[0] = '\\';
+ str[1] = 'a';
+ return 2;
+
+ case '\b':
+ str[0] = '\\';
+ str[1] = 'b';
+ return 2;
+
+ case '\f':
+ str[0] = '\\';
+ str[1] = 'f';
+ return 2;
+
+ case '\n':
+ str[0] = '\\';
+ str[1] = 'n';
+ return 2;
+
+ case '\r':
+ str[0] = '\\';
+ str[1] = 'r';
+ return 2;
+
+ case '\t':
+ str[0] = '\\';
+ str[1] = 't';
+ return 2;
+
+ case '\v':
+ str[0] = '\\';
+ str[1] = 'v';
+ return 2;
+
+ default:
+ str[0] = '.'; /* as in hexdump -C */
+ return 1;
+ }
+ }
+
+ str[0] = c;
+ return 1;
+}
+
+static grub_err_t
+grub_cmd_get_efi_var (struct grub_extcmd_context *ctxt,
+ int argc, char **args)
+{
+ struct grub_arg_list *state = ctxt->state;
+ grub_err_t status;
+ void *efi_var = NULL;
+ grub_size_t efi_var_size = 0;
+ enum efi_var_type efi_type = EFI_VAR_HEX;
+ grub_efi_guid_t global = GRUB_EFI_GLOBAL_VARIABLE_GUID;
+ char *env_var = NULL;
+ grub_size_t i;
+ char *ptr;
+
+ if (1 != argc)
+ return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("one argument expected"));
+
+ if (state[0].set)
+ efi_type = parse_efi_var_type (state[0].arg);
+
+ if (EFI_VAR_INVALID == efi_type)
+ return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("invalid format specifier"));
+
+ efi_var = grub_efi_get_variable (args[0], &global, &efi_var_size);
+ if (!efi_var || !efi_var_size)
+ {
+ status = grub_error (GRUB_ERR_READ_ERROR, N_("cannot read variable"));
+ goto err;
+ }
+
+ switch (efi_type)
+ {
+ case EFI_VAR_ASCII:
+ env_var = grub_malloc (efi_var_size * 2 + 1);
+ if (!env_var)
+ {
+ status = grub_error (GRUB_ERR_OUT_OF_MEMORY, N_("out of memory"));
+ goto err;
+ }
+
+ ptr = env_var;
+
+ for (i = 0; i < efi_var_size; i++)
+ ptr += grub_print_ascii (ptr, ((const char *)efi_var)[i]);
+ *ptr = '\0';
+ break;
+
+ case EFI_VAR_RAW:
+ env_var = grub_malloc (efi_var_size + 1);
+ if (!env_var)
+ {
+ status = grub_error (GRUB_ERR_OUT_OF_MEMORY, N_("out of memory"));
+ goto err;
+ }
+ grub_memcpy (env_var, efi_var, efi_var_size);
+ env_var[efi_var_size] = '\0';
+ break;
+
+ case EFI_VAR_UINT8:
+ env_var = grub_malloc (4);
+ if (!env_var)
+ {
+ status = grub_error (GRUB_ERR_OUT_OF_MEMORY, N_("out of memory"));
+ goto err;
+ }
+ grub_snprintf (env_var, 4, "%u", *((grub_uint8_t *)efi_var));
+ break;
+
+ case EFI_VAR_HEX:
+ env_var = grub_malloc (efi_var_size * 2 + 1);
+ if (!env_var)
+ {
+ status = grub_error (GRUB_ERR_OUT_OF_MEMORY, N_("out of memory"));
+ goto err;
+ }
+ for (i = 0; i < efi_var_size; i++)
+ grub_snprintf (env_var + (i * 2), 3, "%02x", ((grub_uint8_t
*)efi_var)[i]);
+ break;
+
+ case EFI_VAR_DUMP:
+ if (state[1].set)
+ status = grub_error (GRUB_ERR_BAD_ARGUMENT, N_("cannot set
variable with dump format specifier"));
+ else
+ {
+ hexdump (0, (char *)efi_var, efi_var_size);
+ status = GRUB_ERR_NONE;
+ }
+ break;
+
+ default:
+ status = grub_error (GRUB_ERR_BUG, N_("should not happen (bug
in module?)"));
+ goto err;
+ }
+
+ if (efi_type != EFI_VAR_DUMP)
+ {
+ if (state[1].set)
+ status = grub_env_set (state[1].arg, env_var);
+ else
+ {
+ grub_printf ("%s\n", (const char *)env_var);
+ status = GRUB_ERR_NONE;
+ }
+ }
+
+err:
+
+ grub_free (env_var);
+ grub_free (efi_var);
+
+ return status;
+}
+
+static grub_extcmd_t cmd = NULL;
+
+GRUB_MOD_INIT (efivar)
+{
+ cmd = grub_register_extcmd ("get_efivar", grub_cmd_get_efi_var, 0,
N_("[-f FORMAT] [-s ENV_VAR] EFI_VAR"),
+ N_("Read EFI variable and print it or save its contents to
environment variable."), options);
+}
+
+GRUB_MOD_FINI (efivar)
+{
+ if (cmd)
+ grub_unregister_extcmd (cmd);
+}
_______________________________________________
Grub-devel mailing list
Grub-devel@gnu.org
https://lists.gnu.org/mailman/listinfo/grub-devel
