[PATCH v2 1/5] protectors: Add key protectors framework

[Hernan Gatta <hegatta@linux.microsoft.com>]

A key protector encapsulates functionality to retrieve an unlocking key for a
fully-encrypted disk from a specific source. A key protector module registers
itself with the key protectors framework when it is loaded and unregisters when
unloaded. Additionally, a key protector may accept parameters that describe how
it should operate.

The key protectors framework, besides offering registration and unregistration
functions, also offers a one-stop routine for finding and invoking a key
protector by name. If a key protector with the specified name exists and if an
unlocking key is successfully retrieved by it, the function returns to the
caller the retrieved key and its length.

Signed-off-by: Hernan Gatta <hegatta@linux.microsoft.com>
---
 grub-core/Makefile.am       |  1 +
 grub-core/Makefile.core.def |  1 +
 grub-core/kern/protectors.c | 75 +++++++++++++++++++++++++++++++++++++++++++++
 include/grub/protector.h    | 48 +++++++++++++++++++++++++++++
 4 files changed, 125 insertions(+)
 create mode 100644 grub-core/kern/protectors.c
 create mode 100644 include/grub/protector.h

diff --git a/grub-core/Makefile.am b/grub-core/Makefile.am
index ee88e44..f78cd9d 100644
--- a/grub-core/Makefile.am
+++ b/grub-core/Makefile.am
@@ -90,6 +90,7 @@ endif
 KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/mm.h
 KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/parser.h
 KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/partition.h
+KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/protector.h
 KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/stack_protector.h
 KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/term.h
 KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/time.h
diff --git a/grub-core/Makefile.core.def b/grub-core/Makefile.core.def
index 8022e1c..e4ae78b 100644
--- a/grub-core/Makefile.core.def
+++ b/grub-core/Makefile.core.def
@@ -138,6 +138,7 @@ kernel = {
   common = kern/misc.c;
   common = kern/parser.c;
   common = kern/partition.c;
+  common = kern/protectors.c;
   common = kern/rescue_parser.c;
   common = kern/rescue_reader.c;
   common = kern/term.c;
diff --git a/grub-core/kern/protectors.c b/grub-core/kern/protectors.c
new file mode 100644
index 0000000..21954df
--- /dev/null
+++ b/grub-core/kern/protectors.c
@@ -0,0 +1,75 @@
+/*
+ *  GRUB  --  GRand Unified Bootloader
+ *  Copyright (C) 2022 Microsoft 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/list.h>
+#include <grub/misc.h>
+#include <grub/mm.h>
+#include <grub/protector.h>
+
+struct grub_key_protector *grub_key_protectors = NULL;
+
+grub_err_t
+grub_key_protector_register (struct grub_key_protector *protector)
+{
+  if (!protector || !protector->name || !grub_strlen(protector->name))
+    return GRUB_ERR_BAD_ARGUMENT;
+
+  if (grub_key_protectors &&
+      grub_named_list_find (GRUB_AS_NAMED_LIST (grub_key_protectors),
+                            protector->name))
+    return GRUB_ERR_BAD_ARGUMENT;
+
+  grub_list_push (GRUB_AS_LIST_P (&grub_key_protectors),
+                  GRUB_AS_LIST (protector));
+
+  return GRUB_ERR_NONE;
+}
+
+grub_err_t
+grub_key_protector_unregister (struct grub_key_protector *protector)
+{
+  if (!protector)
+    return GRUB_ERR_BAD_ARGUMENT;
+
+  grub_list_remove (GRUB_AS_LIST (protector));
+
+  return GRUB_ERR_NONE;
+}
+
+grub_err_t
+grub_key_protector_recover_key (const char *protector, grub_uint8_t **key,
+                                grub_size_t *key_size)
+{
+  struct grub_key_protector *kp = NULL;
+
+  if (!grub_key_protectors)
+    return GRUB_ERR_OUT_OF_RANGE;
+
+  if (!protector || !grub_strlen (protector))
+    return GRUB_ERR_BAD_ARGUMENT;
+
+  kp = grub_named_list_find (GRUB_AS_NAMED_LIST (grub_key_protectors),
+                             protector);
+  if (!kp)
+    return grub_error (GRUB_ERR_OUT_OF_RANGE,
+                       N_("A key protector with name '%s' could not be found. "
+                          "Is the name spelled correctly and is the "
+                          "corresponding module loaded?"), protector);
+
+  return kp->recover_key (key, key_size);
+}
diff --git a/include/grub/protector.h b/include/grub/protector.h
new file mode 100644
index 0000000..179020a
--- /dev/null
+++ b/include/grub/protector.h
@@ -0,0 +1,48 @@
+/*
+ *  GRUB  --  GRand Unified Bootloader
+ *  Copyright (C) 2022 Microsoft 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/>.
+ */
+
+#ifndef GRUB_PROTECTOR_HEADER
+#define GRUB_PROTECTOR_HEADER 1
+
+#include <grub/err.h>
+#include <grub/types.h>
+
+struct grub_key_protector
+{
+  struct grub_key_protector *next;
+  struct grub_key_protector **prev;
+
+  const char *name;
+
+  grub_err_t (*recover_key) (grub_uint8_t **key, grub_size_t *key_size);
+};
+
+extern struct grub_key_protector *EXPORT_VAR (grub_key_protectors);
+
+grub_err_t
+EXPORT_FUNC (grub_key_protector_register) (struct grub_key_protector *protector);
+
+grub_err_t
+EXPORT_FUNC (grub_key_protector_unregister) (struct grub_key_protector *protector);
+
+grub_err_t
+EXPORT_FUNC (grub_key_protector_recover_key) (const char *protector,
+                                              grub_uint8_t **key,
+                                              grub_size_t *key_size);
+
+#endif /* ! GRUB_PROTECTOR_HEADER */
-- 
1.8.3.1