code.delx.au - refind/blob - mok/mok.c

   1 /* mok/mok.c
   2  *
   3  * Based mostly on shim.c by Matthew J. Garrett/Red Hat (see below
   4  * copyright notice).
   5  *
   6  * Code to perform Secure Boot verification of boot loader programs
   7  * using the Shim program and its Machine Owner Keys (MOKs), to
   8  * supplement standard Secure Boot checks performed by the firmware.
   9  *
  10  */
  11
  12 /*
  13  * shim - trivial UEFI first-stage bootloader
  14  *
  15  * Copyright 2012 Red Hat, Inc <mjg@redhat.com>
  16  *
  17  * Redistribution and use in source and binary forms, with or without
  18  * modification, are permitted provided that the following conditions
  19  * are met:
  20  *
  21  * Redistributions of source code must retain the above copyright
  22  * notice, this list of conditions and the following disclaimer.
  23  *
  24  * Redistributions in binary form must reproduce the above copyright
  25  * notice, this list of conditions and the following disclaimer in the
  26  * documentation and/or other materials provided with the
  27  * distribution.
  28  *
  29  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  30  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  31  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  32  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
  33  * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
  34  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  35  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  36  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  37  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  38  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  39  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
  40  * OF THE POSSIBILITY OF SUCH DAMAGE.
  41  *
  42  * Significant portions of this code are derived from Tianocore
  43  * (http://tianocore.sf.net) and are Copyright 2009-2012 Intel
  44  * Corporation.
  45  */
  46
  47 #include "global.h"
  48 #include "mok.h"
  49 #include "../include/refit_call_wrapper.h"
  50
  51 static EFI_STATUS get_variable (CHAR16 *name, EFI_GUID guid, UINT32 *attributes, UINTN *size, VOID **buffer)
  52 {
  53    EFI_STATUS efi_status;
  54    char allocate = !(*size);
  55
  56    efi_status = uefi_call_wrapper(RT->GetVariable, 5, name, &guid, attributes, size, buffer);
  57
  58    if (efi_status != EFI_BUFFER_TOO_SMALL || !allocate) {
  59       return efi_status;
  60    }
  61
  62    *buffer = AllocatePool(*size);
  63
  64    if (!*buffer) {
  65       Print(L"Unable to allocate variable buffer\n");
  66       return EFI_OUT_OF_RESOURCES;
  67    }
  68
  69    efi_status = uefi_call_wrapper(RT->GetVariable, 5, name, &guid, attributes, size, *buffer);
  70
  71    return efi_status;
  72 } // get_variable()
  73
  74 /*
  75  * Check whether we're in Secure Boot and user mode
  76  */
  77 BOOLEAN secure_mode (VOID)
  78 {
  79    EFI_STATUS status;
  80    EFI_GUID global_var = EFI_GLOBAL_VARIABLE;
  81    UINTN charsize = sizeof(char);
  82    UINT8 sb, setupmode;
  83    UINT32 attributes;
  84
  85    status = get_variable(L"SecureBoot", global_var, &attributes, &charsize, (VOID *)&sb);
  86
  87    /* FIXME - more paranoia here? */
  88    if (status != EFI_SUCCESS || sb != 1) {
  89       return FALSE;
  90    }
  91
  92    status = get_variable(L"SetupMode", global_var, &attributes, &charsize, (VOID *)&setupmode);
  93
  94    if (status == EFI_SUCCESS && setupmode == 1) {
  95       return FALSE;
  96    }
  97
  98    return TRUE;
  99 } // secure_mode()
 100
 101 // Returns TRUE if the shim program is available to verify binaries,
 102 // FALSE if not
 103 BOOLEAN ShimLoaded(void) {
 104    SHIM_LOCK   *shim_lock;
 105    EFI_GUID    ShimLockGuid = SHIM_LOCK_GUID;
 106
 107    return (refit_call3_wrapper(BS->LocateProtocol, &ShimLockGuid, NULL, (VOID**) &shim_lock) == EFI_SUCCESS);
 108 } // ShimLoaded()
 109
 110 // The following is based on the grub_linuxefi_secure_validate() function in Fedora's
 111 // version of GRUB 2.
 112 // Returns TRUE if the specified data is validated by Shim's MOK, FALSE otherwise
 113 BOOLEAN ShimValidate (VOID *data, UINT32 size)
 114 {
 115    SHIM_LOCK   *shim_lock;
 116    EFI_GUID    ShimLockGuid = SHIM_LOCK_GUID;
 117
 118    if ((data != NULL) && (refit_call3_wrapper(BS->LocateProtocol, &ShimLockGuid, NULL, (VOID**) &shim_lock) == EFI_SUCCESS)) {
 119       if (!shim_lock)
 120          return FALSE;
 121
 122       if (shim_lock->shim_verify(data, size) == EFI_SUCCESS)
 123          return TRUE;
 124    }
 125
 126    return FALSE;
 127 } // BOOLEAN ShimValidate()