From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001

From: Daniel Axtens <dja@axtens.net>

Date: Thu, 30 Jul 2020 01:35:43 +1000

Subject: [PATCH] appended signatures: support verifying appended signatures

Building on the parsers and the ability to embed x509 certificates, as

well as the existing gcrypt functionality, add a module for verifying

appended signatures.

This includes:

 - a verifier that requires that kernels and grub modules have appended

   signatures. It shares lots of logic with shim-lock verifier about what

   files need to be verified and what modules are unsafe to have loaded.

 - commands to manage the list of trusted certificates for verification.

Similar to the PGP verifier, if a certificate is embedded in the core

image, verification will be enforced unless disabled on the the grub

command line or by load_env.

Thus, as with the PGP verifier, it is not a complete secure-boot solution:

other mechanisms must be used to ensure that a user cannot drop to the

grub shell and disable verification.

Signed-off-by: Daniel Axtens <dja@axtens.net>

---

 grub-core/Makefile.core.def                  |  12 +

 grub-core/commands/appendedsig/appendedsig.c | 644 +++++++++++++++++++++++++++

 include/grub/file.h                          |   2 +

 3 files changed, 658 insertions(+)

 create mode 100644 grub-core/commands/appendedsig/appendedsig.c

diff --git a/grub-core/Makefile.core.def b/grub-core/Makefile.core.def

index fd1229c6328..1cf6b60f82e 100644

--- a/grub-core/Makefile.core.def

+++ b/grub-core/Makefile.core.def

@@ -921,6 +921,18 @@ module = {

   cppflags = '-I$(srcdir)/lib/posix_wrap';

 };

+module = {

+  name = appendedsig;

+  common = commands/appendedsig/appendedsig.c;

+  common = commands/appendedsig/x509.c;

+  common = commands/appendedsig/pkcs7.c;

+  common = commands/appendedsig/asn1util.c;

+  common = commands/appendedsig/gnutls_asn1_tab.c;

+  common = commands/appendedsig/pkix_asn1_tab.c;

+  cflags = '$(CFLAGS_POSIX)';

+  cppflags = '-I$(srcdir)/lib/posix_wrap';

+};

+

 module = {

   name = verifiers;

   common = commands/verifiers.c;

diff --git a/grub-core/commands/appendedsig/appendedsig.c b/grub-core/commands/appendedsig/appendedsig.c

new file mode 100644

index 00000000000..5d8897be5c8

--- /dev/null

+++ b/grub-core/commands/appendedsig/appendedsig.c

@@ -0,0 +1,644 @@

+/*

+ *  GRUB  --  GRand Unified Bootloader

+ *  Copyright (C) 2020  IBM Corporation.

+ *

+ *  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/misc.h>

+#include <grub/mm.h>

+#include <grub/err.h>

+#include <grub/dl.h>

+#include <grub/file.h>

+#include <grub/command.h>

+#include <grub/crypto.h>

+#include <grub/pkcs1_v15.h>

+#include <grub/i18n.h>

+#include <grub/gcrypt/gcrypt.h>

+#include <grub/kernel.h>

+#include <grub/extcmd.h>

+#include <grub/verify.h>

+#include <grub/libtasn1.h>

+#include <grub/env.h>

+

+#include "appendedsig.h"

+

+GRUB_MOD_LICENSE ("GPLv3+");

+

+const char magic[] = "~Module signature appended~\n";

+

+/*

+ * This structure is extracted from scripts/sign-file.c in the linux kernel

+ * source. It was licensed as LGPLv2.1+, which is GPLv3+ compatible.

+ */

+struct module_signature

+{

+  grub_uint8_t algo;		/* Public-key crypto algorithm [0] */

+  grub_uint8_t hash;		/* Digest algorithm [0] */

+  grub_uint8_t id_type;		/* Key identifier type [PKEY_ID_PKCS7] */

+  grub_uint8_t signer_len;	/* Length of signer's name [0] */

+  grub_uint8_t key_id_len;	/* Length of key identifier [0] */

+  grub_uint8_t __pad[3];

+  grub_uint32_t sig_len;	/* Length of signature data */

+} GRUB_PACKED;

+

+

+/* This represents an entire, parsed, appended signature */

+struct grub_appended_signature

+{

+  grub_size_t signature_len;		/* Length of PKCS#7 data +

+                                         * metadata + magic */

+

+  struct module_signature sig_metadata;	/* Module signature metadata */

+  struct pkcs7_signedData pkcs7;	/* Parsed PKCS#7 data */

+};

+

+/* Trusted certificates for verifying appended signatures */

+struct x509_certificate *grub_trusted_key;

+

+/*

+ * Force gcry_rsa to be a module dependency.

+ *

+ * If we use grub_crypto_pk_rsa, then then the gcry_rsa module won't be built

+ * in if you add 'appendedsig' to grub-install --modules. You would need to

+ * add 'gcry_rsa' too. That's confusing and seems suboptimal, especially when

+ * we only support RSA.

+ *

+ * Dynamic loading also causes some concerns. We can't load gcry_rsa from the

+ * the filesystem after we install the verifier - we won't be able to verify

+ * it without having it already present. We also shouldn't load it before we

+ * install the verifier, because that would mean it wouldn't be verified - an

+ * attacker could insert any code they wanted into the module.

+ *

+ * So instead, reference the internal symbol from gcry_rsa. That creates a

+ * direct dependency on gcry_rsa, so it will be built in when this module

+ * is built in. Being built in (assuming the core image is itself signed!)

+ * also resolves our concerns about loading from the filesystem.

+ */

+extern gcry_pk_spec_t _gcry_pubkey_spec_rsa;

+

+static int check_sigs = 0;

+

+static char *

+grub_env_write_sec (struct grub_env_var *var __attribute__((unused)),

+		    const char *val)

+{

+  check_sigs = (*val == '1') || (*val == 'e');

+  return grub_strdup (check_sigs ? "enforce" : "no");

+}

+

+static grub_err_t

+read_cert_from_file (grub_file_t f, struct x509_certificate *certificate)

+{

+  grub_err_t err;

+  grub_uint8_t *buf = NULL;

+  grub_ssize_t read_size;

+  grub_off_t total_read_size = 0;

+  grub_off_t file_size = grub_file_size (f);

+

+

+  if (file_size == GRUB_FILE_SIZE_UNKNOWN)

+    return grub_error (GRUB_ERR_BAD_ARGUMENT,

+		       N_("Cannot parse a certificate file of unknown size"));

+

+  buf = grub_zalloc (file_size);

+  if (!buf)

+    return grub_error (GRUB_ERR_OUT_OF_MEMORY,

+		       N_("Could not allocate buffer for certificate file contents"));

+

+  while (total_read_size < file_size)

+    {

+      read_size =

+	grub_file_read (f, &buf[total_read_size],

+			file_size - total_read_size);

+      if (read_size < 0)

+	{

+	  err = grub_error (GRUB_ERR_READ_ERROR,

+			    N_("Error reading certificate file"));

+	  goto cleanup_buf;

+	}

+      total_read_size += read_size;

+    }

+

+  err = certificate_import (buf, total_read_size, certificate);

+  if (err != GRUB_ERR_NONE)

+    goto cleanup_buf;

+

+  return GRUB_ERR_NONE;

+

+cleanup_buf:

+  grub_free (buf);

+  return err;

+}

+

+static grub_err_t

+extract_appended_signature (grub_uint8_t * buf, grub_size_t bufsize,

+			    struct grub_appended_signature *sig)

+{

+  grub_err_t err;

+  grub_size_t pkcs7_size;

+  grub_size_t remaining_len;

+  grub_uint8_t *appsigdata = buf + bufsize - grub_strlen (magic);

+

+  if (bufsize < grub_strlen (magic))

+    return grub_error (GRUB_ERR_BAD_SIGNATURE,

+		       N_("File too short for signature magic"));

+

+  if (grub_memcmp (appsigdata, (grub_uint8_t *) magic, grub_strlen (magic)))

+    return grub_error (GRUB_ERR_BAD_SIGNATURE,

+		       N_("Missing or invalid signature magic"));

+

+  remaining_len = bufsize - grub_strlen (magic);

+

+  if (remaining_len < sizeof (struct module_signature))

+    return grub_error (GRUB_ERR_BAD_SIGNATURE,

+		       N_("File too short for signature metadata"));

+

+  appsigdata -= sizeof (struct module_signature);

+

+  /* extract the metadata */

+  grub_memcpy (&(sig->sig_metadata), appsigdata,

+	       sizeof (struct module_signature));

+

+  remaining_len -= sizeof (struct module_signature);

+

+  if (sig->sig_metadata.id_type != 2)

+    return grub_error (GRUB_ERR_BAD_SIGNATURE, N_("Wrong signature type"));

+

+#ifdef GRUB_TARGET_WORDS_BIGENDIAN

+  pkcs7_size = sig->sig_metadata.sig_len;

+#else

+  pkcs7_size = __builtin_bswap32 (sig->sig_metadata.sig_len);

+#endif

+

+  if (pkcs7_size > remaining_len)

+    return grub_error (GRUB_ERR_BAD_SIGNATURE,

+		       N_("File too short for PKCS#7 message"));

+

+  grub_dprintf ("appendedsig", "sig len %" PRIuGRUB_SIZE "\n", pkcs7_size);

+

+  sig->signature_len =

+    grub_strlen (magic) + sizeof (struct module_signature) + pkcs7_size;

+

+  /* rewind pointer and parse pkcs7 data */

+  appsigdata -= pkcs7_size;

+

+  err = parse_pkcs7_signedData (appsigdata, pkcs7_size, &sig->pkcs7);

+  if (err != GRUB_ERR_NONE)

+    return err;

+

+  return GRUB_ERR_NONE;

+}

+

+static grub_err_t

+grub_verify_appended_signature (grub_uint8_t * buf, grub_size_t bufsize)

+{

+  grub_err_t err = GRUB_ERR_NONE;

+  grub_size_t datasize;

+  void *context;

+  unsigned char *hash;

+  gcry_mpi_t hashmpi;

+  gcry_err_code_t rc;

+  struct x509_certificate *pk;

+  struct grub_appended_signature sig;

+

+  if (!grub_trusted_key)

+    return grub_error (GRUB_ERR_BAD_SIGNATURE,

+		       N_("No trusted keys to verify against"));

+

+  err = extract_appended_signature (buf, bufsize, &sig);

+  if (err != GRUB_ERR_NONE)

+    return err;

+

+  datasize = bufsize - sig.signature_len;

+

+  context = grub_zalloc (sig.pkcs7.hash->contextsize);

+  if (!context)

+    return grub_errno;

+

+  sig.pkcs7.hash->init (context);

+  sig.pkcs7.hash->write (context, buf, datasize);

+  sig.pkcs7.hash->final (context);

+  hash = sig.pkcs7.hash->read (context);

+  grub_dprintf ("appendedsig",

+		"data size %" PRIxGRUB_SIZE ", hash %02x%02x%02x%02x...\n",

+		datasize, hash[0], hash[1], hash[2], hash[3]);

+

+  err = GRUB_ERR_BAD_SIGNATURE;

+  for (pk = grub_trusted_key; pk; pk = pk->next)

+    {

+      rc = grub_crypto_rsa_pad (&hashmpi, hash, sig.pkcs7.hash, pk->mpis[0]);

+      if (rc)

+	{

+	  err = grub_error (GRUB_ERR_BAD_SIGNATURE,

+			    N_("Error padding hash for RSA verification: %d"),

+			    rc);

+	  goto cleanup;

+	}

+

+      rc = _gcry_pubkey_spec_rsa.verify (0, hashmpi, &sig.pkcs7.sig_mpi,

+					 pk->mpis, NULL, NULL);

+      gcry_mpi_release (hashmpi);

+

+      if (rc == 0)

+	{

+	  grub_dprintf ("appendedsig", "verify with key '%s' succeeded\n",

+			pk->subject);

+	  err = GRUB_ERR_NONE;

+	  break;

+	}

+

+      grub_dprintf ("appendedsig", "verify with key '%s' failed with %d\n",

+		    pk->subject, rc);

+    }

+

+  /* If we didn't verify, provide a neat message */

+  if (err != GRUB_ERR_NONE)

+      err = grub_error (GRUB_ERR_BAD_SIGNATURE,

+			N_("Failed to verify signature against a trusted key"));

+

+cleanup:

+  grub_free (context);

+  pkcs7_signedData_release (&sig.pkcs7);

+

+  return err;

+}

+

+static grub_err_t

+grub_cmd_verify_signature (grub_command_t cmd __attribute__((unused)),

+			   int argc, char **args)

+{

+  grub_file_t f;

+  grub_err_t err = GRUB_ERR_NONE;

+  grub_uint8_t *data;

+  grub_ssize_t read_size;

+  grub_off_t file_size, total_read_size = 0;

+

+  if (argc < 1)

+    return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("one argument expected"));

+

+  grub_dprintf ("appendedsig", "verifying %s\n", args[0]);

+

+  f = grub_file_open (args[0], GRUB_FILE_TYPE_VERIFY_SIGNATURE);

+  if (!f)

+    {

+      err = grub_errno;

+      goto cleanup;

+    }

+

+  file_size = grub_file_size (f);

+  if (file_size == GRUB_FILE_SIZE_UNKNOWN)

+    return grub_error (GRUB_ERR_BAD_ARGUMENT,

+		       N_("Cannot verify the signature of a file of unknown size"));

+

+  data = grub_malloc (file_size);

+  if (!data)

+    return grub_error (GRUB_ERR_OUT_OF_MEMORY,

+		       N_("Could not allocate data buffer size "

+		       PRIuGRUB_UINT64_T " for verification"), file_size);

+

+  while (total_read_size < file_size)

+    {

+      read_size =

+	grub_file_read (f, &data[total_read_size],

+			file_size - total_read_size);

+      if (read_size < 0)

+	{

+	  err = grub_error (GRUB_ERR_READ_ERROR,

+			    N_("Error reading file to verify"));

+	  goto cleanup_data;

+	}

+      total_read_size += read_size;

+    }

+

+  err = grub_verify_appended_signature (data, file_size);

+

+cleanup_data:

+  grub_free (data);

+cleanup:

+  if (f)

+    grub_file_close (f);

+  return err;

+}

+

+static grub_err_t

+grub_cmd_distrust (grub_command_t cmd __attribute__((unused)),

+		   int argc, char **args)

+{

+  unsigned long cert_num, i;

+  struct x509_certificate *cert, *prev;

+

+  if (argc != 1)

+    return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("One argument expected"));

+

+  grub_errno = GRUB_ERR_NONE;

+  cert_num = grub_strtoul (args[0], NULL, 10);

+  if (grub_errno != GRUB_ERR_NONE)

+    return grub_errno;

+

+  if (cert_num < 1)

+    return grub_error (GRUB_ERR_BAD_ARGUMENT,

+		       N_("Certificate number too small - numbers start at 1"));

+

+  if (cert_num == 1)

+    {

+      cert = grub_trusted_key;

+      grub_trusted_key = cert->next;

+

+      certificate_release (cert);

+      grub_free (cert);

+      return GRUB_ERR_NONE;

+    }

+  i = 2;

+  prev = grub_trusted_key;

+  cert = grub_trusted_key->next;

+  while (cert)

+    {

+      if (i == cert_num)

+	{

+	  prev->next = cert->next;

+	  certificate_release (cert);

+	  grub_free (cert);

+	  return GRUB_ERR_NONE;

+	}

+      i++;

+      prev = cert;

+      cert = cert->next;

+    }

+

+  return grub_error (GRUB_ERR_BAD_ARGUMENT,

+		     N_("No certificate number %d found - only %d certificates in the store"),

+		     cert_num, i - 1);

+}

+

+static grub_err_t

+grub_cmd_trust (grub_command_t cmd __attribute__((unused)),

+		int argc, char **args)

+{

+  grub_file_t certf;

+  struct x509_certificate *cert = NULL;

+  grub_err_t err;

+

+  if (argc != 1)

+    return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("one argument expected"));

+

+  certf = grub_file_open (args[0],

+			  GRUB_FILE_TYPE_CERTIFICATE_TRUST

+			  | GRUB_FILE_TYPE_NO_DECOMPRESS);

+  if (!certf)

+    return grub_errno;

+

+

+  cert = grub_zalloc (sizeof (struct x509_certificate));

+  if (!cert)

+    return grub_error (GRUB_ERR_OUT_OF_MEMORY,

+		       N_("Could not allocate memory for certificate"));

+

+  err = read_cert_from_file (certf, cert);

+  grub_file_close (certf);

+  if (err != GRUB_ERR_NONE)

+    {

+      grub_free (cert);

+      return err;

+    }

+  grub_dprintf ("appendedsig", "Loaded certificate with CN: %s\n",

+		cert->subject);

+

+  cert->next = grub_trusted_key;

+  grub_trusted_key = cert;

+

+  return GRUB_ERR_NONE;

+}

+

+static grub_err_t

+grub_cmd_list (grub_command_t cmd __attribute__((unused)),

+	       int argc __attribute__((unused)),

+	       char **args __attribute__((unused)))

+{

+  struct x509_certificate *cert;

+  int cert_num = 1;

+  grub_size_t i;

+

+  for (cert = grub_trusted_key; cert; cert = cert->next)

+    {

+      grub_printf (N_("Certificate %d:\n"), cert_num);

+

+      grub_printf (N_("\tSerial: "));

+      for (i = 0; i < cert->serial_len - 1; i++)

+	{

+	  grub_printf ("%02x:", cert->serial[i]);

+	}

+      grub_printf ("%02x\n", cert->serial[cert->serial_len - 1]);

+

+      grub_printf ("\tCN: %s\n\n", cert->subject);

+      cert_num++;

+

+    }

+

+  return GRUB_ERR_NONE;

+}

+

+static grub_err_t

+appendedsig_init (grub_file_t io, enum grub_file_type type,

+		  void **context __attribute__((unused)),

+		  enum grub_verify_flags *flags)

+{

+  const char *dangerous_mod;

+

+  if (!check_sigs)

+    {

+      *flags = GRUB_VERIFY_FLAGS_SKIP_VERIFICATION;

+      return GRUB_ERR_NONE;

+    }

+

+  switch (type & GRUB_FILE_TYPE_MASK)

+    {

+    case GRUB_FILE_TYPE_GRUB_MODULE:

+      if (grub_is_dangerous_module (io))

+	return grub_error (GRUB_ERR_ACCESS_DENIED,

+			   N_("module cannot be loaded in appended signature mode: %s"),

+			   io->name);

+

+      *flags = GRUB_VERIFY_FLAGS_SINGLE_CHUNK;

+      return GRUB_ERR_NONE;

+

+    case GRUB_FILE_TYPE_ACPI_TABLE:

+    case GRUB_FILE_TYPE_DEVICE_TREE_IMAGE:

+      *flags = GRUB_VERIFY_FLAGS_DEFER_AUTH;

+      return GRUB_ERR_NONE;

+

+    case GRUB_FILE_TYPE_CERTIFICATE_TRUST:

+      /*

+       * This is a certificate to add to trusted keychain.

+       *

+       * This needs to be verified or blocked. Ideally we'd write an x509

+       * verifier, but we lack the hubris required to take this on. Instead,

+       * require that it have an appended signature.

+       */

+

+      /* Fall through */

+

+    case GRUB_FILE_TYPE_LINUX_KERNEL:

+    case GRUB_FILE_TYPE_MULTIBOOT_KERNEL:

+    case GRUB_FILE_TYPE_BSD_KERNEL:

+    case GRUB_FILE_TYPE_XNU_KERNEL:

+    case GRUB_FILE_TYPE_PLAN9_KERNEL:

+

+      dangerous_mod = grub_dangerous_module_loaded ();

+      if (dangerous_mod)

+	return grub_error (GRUB_ERR_ACCESS_DENIED,

+			   N_("cannot proceed due to dangerous module in memory: %s"),

+			   dangerous_mod);

+

+      *flags = GRUB_VERIFY_FLAGS_SINGLE_CHUNK;

+      return GRUB_ERR_NONE;

+

+    default:

+      /*

+       * powerpc only supports the linux loader. If you support more,

+       * (especially chain loaded binaries) make sure they're checked!

+       */

+      *flags = GRUB_VERIFY_FLAGS_SKIP_VERIFICATION;

+      return GRUB_ERR_NONE;

+    }

+}

+

+static grub_err_t

+appendedsig_write (void *ctxt __attribute__((unused)),

+		   void *buf, grub_size_t size)

+{

+  return grub_verify_appended_signature (buf, size);

+}

+

+struct grub_file_verifier grub_appendedsig_verifier = {

+  .name = "appendedsig",

+  .init = appendedsig_init,

+  .write = appendedsig_write,

+};

+

+static grub_ssize_t

+pseudo_read (struct grub_file *file, char *buf, grub_size_t len)

+{

+  grub_memcpy (buf, (grub_uint8_t *) file->data + file->offset, len);

+  return len;

+}

+

+/* Filesystem descriptor.  */

+static struct grub_fs pseudo_fs = {

+  .name = "pseudo",

+  .read = pseudo_read

+};

+

+static grub_command_t cmd_verify, cmd_list, cmd_distrust, cmd_trust;

+

+GRUB_MOD_INIT (appendedsig)

+{

+  int rc;

+  struct grub_module_header *header;

+  const char *val;

+

+  val = grub_env_get ("check_appended_signatures");

+  grub_dprintf ("appendedsig", "check_appended_signatures='%s'\n", val);

+

+  if (val && (val[0] == '1' || val[0] == 'e'))

+    check_sigs = 1;

+  else

+    check_sigs = 0;

+

+  grub_trusted_key = NULL;

+

+  grub_register_variable_hook ("check_appended_signatures", 0,

+			       grub_env_write_sec);

+  grub_env_export ("check_appended_signatures");

+

+  rc = asn1_init ();

+  if (rc)

+    grub_fatal ("Error initing ASN.1 data structures: %d: %s\n", rc,

+		asn1_strerror (rc));

+

+  FOR_MODULES (header)

+  {

+    struct grub_file pseudo_file;

+    struct x509_certificate *pk = NULL;

+    grub_err_t err;

+

+    /* Not an ELF module, skip.  */

+    if (header->type != OBJ_TYPE_X509_PUBKEY)

+      continue;

+

+    grub_memset (&pseudo_file, 0, sizeof (pseudo_file));

+    pseudo_file.fs = &pseudo_fs;

+    pseudo_file.size = header->size - sizeof (struct grub_module_header);

+    pseudo_file.data = (char *) header + sizeof (struct grub_module_header);

+

+    grub_dprintf ("appendedsig",

+		  "Found an x509 key, size=%" PRIuGRUB_UINT64_T "\n",

+		  pseudo_file.size);

+

+    pk = grub_zalloc (sizeof (struct x509_certificate));

+    if (!pk)

+      {

+	grub_fatal ("Out of memory loading initial certificates");

+      }

+

+    err = read_cert_from_file (&pseudo_file, pk);

+    if (err != GRUB_ERR_NONE)

+      grub_fatal ("Error loading initial key: %s", grub_errmsg);

+

+    grub_dprintf ("appendedsig", "loaded certificate CN='%s'\n", pk->subject);

+

+    pk->next = grub_trusted_key;

+    grub_trusted_key = pk;

+  }

+

+  if (!val || val[0] == '\0')

+    {

+      grub_env_set ("check_appended_signatures",

+		    grub_trusted_key ? "enforce" : "no");

+    }

+

+  cmd_trust =

+    grub_register_command ("trust_certificate", grub_cmd_trust,

+			   N_("X509_CERTIFICATE"),

+			   N_("Add X509_CERTIFICATE to trusted certificates."));

+  cmd_list =

+    grub_register_command ("list_certificates", grub_cmd_list, 0,

+			   N_("Show the list of trusted x509 certificates."));

+  cmd_verify =

+    grub_register_command ("verify_appended", grub_cmd_verify_signature,

+			   N_("FILE"),

+			   N_("Verify FILE against the trusted x509 certificates."));

+  cmd_distrust =

+    grub_register_command ("distrust_certificate", grub_cmd_distrust,

+			   N_("CERT_NUMBER"),

+			   N_("Remove CERT_NUMBER (as listed by list_certificates) from trusted certificates."));

+

+  grub_verifier_register (&grub_appendedsig_verifier);

+  grub_dl_set_persistent (mod);

+}

+

+GRUB_MOD_FINI (appendedsig)

+{

+  /*

+   * grub_dl_set_persistent should prevent this from actually running, but

+   * it does still run under emu.

+   */

+

+  grub_verifier_unregister (&grub_appendedsig_verifier);

+  grub_unregister_command (cmd_verify);

+  grub_unregister_command (cmd_list);

+  grub_unregister_command (cmd_trust);

+  grub_unregister_command (cmd_distrust);

+}

diff --git a/include/grub/file.h b/include/grub/file.h

index cbbd294655b..2e337dbd68d 100644

--- a/include/grub/file.h

+++ b/include/grub/file.h

@@ -82,6 +82,8 @@ enum grub_file_type

     GRUB_FILE_TYPE_PUBLIC_KEY,

     /* File holding public key to add to trused keys.  */

     GRUB_FILE_TYPE_PUBLIC_KEY_TRUST,

+    /* File holding x509 certificiate to add to trusted keys.  */

+    GRUB_FILE_TYPE_CERTIFICATE_TRUST,

     /* File of which we intend to print a blocklist to the user.  */

     GRUB_FILE_TYPE_PRINT_BLOCKLIST,

     /* File we intend to use for test loading or testing speed.  */