MdeModulePkg/Universal/Variable/RuntimeDxe/TcgMorLockSmm.c

   1 /** @file
   2   TCG MOR (Memory Overwrite Request) Lock Control support (SMM version).
   3
   4   This module initilizes MemoryOverwriteRequestControlLock variable.
   5   This module adds Variable Hook and check MemoryOverwriteRequestControlLock.
   6
   7 Copyright (c) 2016 - 2018, Intel Corporation. All rights reserved.<BR>
   8 Copyright (c) Microsoft Corporation.
   9 SPDX-License-Identifier: BSD-2-Clause-Patent
  10
  11 **/
  12
  13 #include <PiDxe.h>
  14 #include <Guid/MemoryOverwriteControl.h>
  15 #include <IndustryStandard/MemoryOverwriteRequestControlLock.h>
  16 #include <Library/DebugLib.h>
  17 #include <Library/BaseLib.h>
  18 #include <Library/BaseMemoryLib.h>
  19 #include "Variable.h"
  20
  21 #include <Protocol/VariablePolicy.h>
  22
  23 #include <Library/VariablePolicyLib.h>
  24
  25 typedef struct {
  26   CHAR16                                 *VariableName;
  27   EFI_GUID                               *VendorGuid;
  28 } VARIABLE_TYPE;
  29
  30 VARIABLE_TYPE  mMorVariableType[] = {
  31   {MEMORY_OVERWRITE_REQUEST_VARIABLE_NAME,      &gEfiMemoryOverwriteControlDataGuid},
  32   {MEMORY_OVERWRITE_REQUEST_CONTROL_LOCK_NAME,  &gEfiMemoryOverwriteRequestControlLockGuid},
  33 };
  34
  35 BOOLEAN         mMorPassThru = FALSE;
  36
  37 #define MOR_LOCK_DATA_UNLOCKED           0x0
  38 #define MOR_LOCK_DATA_LOCKED_WITHOUT_KEY 0x1
  39 #define MOR_LOCK_DATA_LOCKED_WITH_KEY    0x2
  40
  41 #define MOR_LOCK_V1_SIZE      1
  42 #define MOR_LOCK_V2_KEY_SIZE  8
  43
  44 typedef enum {
  45   MorLockStateUnlocked = 0,
  46   MorLockStateLocked = 1,
  47 } MOR_LOCK_STATE;
  48
  49 BOOLEAN         mMorLockInitializationRequired = FALSE;
  50 UINT8           mMorLockKey[MOR_LOCK_V2_KEY_SIZE];
  51 BOOLEAN         mMorLockKeyEmpty = TRUE;
  52 BOOLEAN         mMorLockPassThru = FALSE;
  53 MOR_LOCK_STATE  mMorLockState = MorLockStateUnlocked;
  54
  55 /**
  56   Returns if this is MOR related variable.
  57
  58   @param  VariableName the name of the vendor's variable, it's a Null-Terminated Unicode String
  59   @param  VendorGuid   Unify identifier for vendor.
  60
  61   @retval  TRUE            The variable is MOR related.
  62   @retval  FALSE           The variable is NOT MOR related.
  63 **/
  64 BOOLEAN
  65 IsAnyMorVariable (
  66   IN CHAR16                                 *VariableName,
  67   IN EFI_GUID                               *VendorGuid
  68   )
  69 {
  70   UINTN   Index;
  71
  72   for (Index = 0; Index < sizeof(mMorVariableType)/sizeof(mMorVariableType[0]); Index++) {
  73     if ((StrCmp (VariableName, mMorVariableType[Index].VariableName) == 0) &&
  74         (CompareGuid (VendorGuid, mMorVariableType[Index].VendorGuid))) {
  75       return TRUE;
  76     }
  77   }
  78   return FALSE;
  79 }
  80
  81 /**
  82   Returns if this is MOR lock variable.
  83
  84   @param  VariableName the name of the vendor's variable, it's a Null-Terminated Unicode String
  85   @param  VendorGuid   Unify identifier for vendor.
  86
  87   @retval  TRUE            The variable is MOR lock variable.
  88   @retval  FALSE           The variable is NOT MOR lock variable.
  89 **/
  90 BOOLEAN
  91 IsMorLockVariable (
  92   IN CHAR16                                 *VariableName,
  93   IN EFI_GUID                               *VendorGuid
  94   )
  95 {
  96   if ((StrCmp (VariableName, MEMORY_OVERWRITE_REQUEST_CONTROL_LOCK_NAME) == 0) &&
  97       (CompareGuid (VendorGuid, &gEfiMemoryOverwriteRequestControlLockGuid))) {
  98     return TRUE;
  99   }
 100   return FALSE;
 101 }
 102
 103 /**
 104   Set MOR lock variable.
 105
 106   @param  Data         MOR Lock variable data.
 107
 108   @retval  EFI_SUCCESS            The firmware has successfully stored the variable and its data as
 109                                   defined by the Attributes.
 110   @retval  EFI_INVALID_PARAMETER  An invalid combination of attribute bits was supplied, or the
 111                                   DataSize exceeds the maximum allowed.
 112   @retval  EFI_INVALID_PARAMETER  VariableName is an empty Unicode string.
 113   @retval  EFI_OUT_OF_RESOURCES   Not enough storage is available to hold the variable and its data.
 114   @retval  EFI_DEVICE_ERROR       The variable could not be saved due to a hardware failure.
 115   @retval  EFI_WRITE_PROTECTED    The variable in question is read-only.
 116   @retval  EFI_WRITE_PROTECTED    The variable in question cannot be deleted.
 117   @retval  EFI_SECURITY_VIOLATION The variable could not be written due to EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS
 118                                   set but the AuthInfo does NOT pass the validation check carried
 119                                   out by the firmware.
 120   @retval  EFI_NOT_FOUND          The variable trying to be updated or deleted was not found.
 121 **/
 122 EFI_STATUS
 123 SetMorLockVariable (
 124   IN UINT8  Data
 125   )
 126 {
 127   EFI_STATUS  Status;
 128
 129   mMorLockPassThru = TRUE;
 130   Status = VariableServiceSetVariable (
 131              MEMORY_OVERWRITE_REQUEST_CONTROL_LOCK_NAME,
 132              &gEfiMemoryOverwriteRequestControlLockGuid,
 133              EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_RUNTIME_ACCESS,
 134              sizeof(Data),
 135              &Data
 136              );
 137   mMorLockPassThru = FALSE;
 138   return Status;
 139 }
 140
 141 /**
 142   This service is an MorLock checker handler for the SetVariable().
 143
 144   @param  VariableName the name of the vendor's variable, as a
 145                        Null-Terminated Unicode String
 146   @param  VendorGuid   Unify identifier for vendor.
 147   @param  Attributes   Point to memory location to return the attributes of variable. If the point
 148                        is NULL, the parameter would be ignored.
 149   @param  DataSize     The size in bytes of Data-Buffer.
 150   @param  Data         Point to the content of the variable.
 151
 152   @retval  EFI_SUCCESS            The MorLock check pass, and Variable driver can store the variable data.
 153   @retval  EFI_INVALID_PARAMETER  The MorLock data or data size or attributes is not allowed.
 154   @retval  EFI_ACCESS_DENIED      The MorLock is locked.
 155   @retval  EFI_WRITE_PROTECTED    The MorLock deletion is not allowed.
 156   @retval  EFI_ALREADY_STARTED    The MorLock variable is handled inside this function.
 157                                   Variable driver can just return EFI_SUCCESS.
 158 **/
 159 EFI_STATUS
 160 SetVariableCheckHandlerMorLock (
 161   IN CHAR16     *VariableName,
 162   IN EFI_GUID   *VendorGuid,
 163   IN UINT32     Attributes,
 164   IN UINTN      DataSize,
 165   IN VOID       *Data
 166   )
 167 {
 168   EFI_STATUS  Status;
 169
 170   //
 171   // Basic Check
 172   //
 173   if (Attributes == 0 || DataSize == 0 || Data == NULL) {
 174     //
 175     // Permit deletion for passthru request, deny it otherwise.
 176     //
 177     return mMorLockPassThru ? EFI_SUCCESS : EFI_WRITE_PROTECTED;
 178   }
 179
 180   if ((Attributes != (EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_RUNTIME_ACCESS)) ||
 181       ((DataSize != MOR_LOCK_V1_SIZE) && (DataSize != MOR_LOCK_V2_KEY_SIZE))) {
 182     return EFI_INVALID_PARAMETER;
 183   }
 184
 185   //
 186   // Do not check if the request is passthru.
 187   //
 188   if (mMorLockPassThru) {
 189     return EFI_SUCCESS;
 190   }
 191
 192   if (mMorLockState == MorLockStateUnlocked) {
 193     //
 194     // In Unlocked State
 195     //
 196     if (DataSize == MOR_LOCK_V1_SIZE) {
 197       //
 198       // V1 - lock permanently
 199       //
 200       if (*(UINT8 *)Data == MOR_LOCK_DATA_UNLOCKED) {
 201         //
 202         // Unlock
 203         //
 204         Status = SetMorLockVariable (MOR_LOCK_DATA_UNLOCKED);
 205         if (!EFI_ERROR (Status)) {
 206           //
 207           // return EFI_ALREADY_STARTED to skip variable set.
 208           //
 209           return EFI_ALREADY_STARTED;
 210         } else {
 211           //
 212           // SetVar fail
 213           //
 214           return Status;
 215         }
 216       } else if (*(UINT8 *)Data == MOR_LOCK_DATA_LOCKED_WITHOUT_KEY) {
 217         //
 218         // Lock without key
 219         //
 220         Status = SetMorLockVariable (MOR_LOCK_DATA_LOCKED_WITHOUT_KEY);
 221         if (!EFI_ERROR (Status)) {
 222           //
 223           // Lock success
 224           //
 225           mMorLockState = MorLockStateLocked;
 226           //
 227           // return EFI_ALREADY_STARTED to skip variable set.
 228           //
 229           return EFI_ALREADY_STARTED;
 230         } else {
 231           //
 232           // SetVar fail
 233           //
 234           return Status;
 235         }
 236       } else {
 237         return EFI_INVALID_PARAMETER;
 238       }
 239     } else if (DataSize == MOR_LOCK_V2_KEY_SIZE) {
 240       //
 241       // V2 lock and provision the key
 242       //
 243
 244       //
 245       // Need set here because the data value on flash is different
 246       //
 247       Status = SetMorLockVariable (MOR_LOCK_DATA_LOCKED_WITH_KEY);
 248       if (EFI_ERROR(Status)) {
 249         //
 250         // SetVar fail, do not provision the key
 251         //
 252         return Status;
 253       } else {
 254         //
 255         // Lock success, provision the key
 256         //
 257         mMorLockKeyEmpty = FALSE;
 258         CopyMem (mMorLockKey, Data, MOR_LOCK_V2_KEY_SIZE);
 259         mMorLockState = MorLockStateLocked;
 260         //
 261         // return EFI_ALREADY_STARTED to skip variable set.
 262         //
 263         return EFI_ALREADY_STARTED;
 264       }
 265     } else {
 266       ASSERT (FALSE);
 267       return EFI_OUT_OF_RESOURCES;
 268     }
 269   } else {
 270     //
 271     // In Locked State
 272     //
 273     if (mMorLockKeyEmpty || (DataSize != MOR_LOCK_V2_KEY_SIZE)) {
 274       return EFI_ACCESS_DENIED;
 275     }
 276     if ((CompareMem (Data, mMorLockKey, MOR_LOCK_V2_KEY_SIZE) == 0)) {
 277       //
 278       // Key match - unlock
 279       //
 280
 281       //
 282       // Need set here because the data value on flash is different
 283       //
 284       Status = SetMorLockVariable (MOR_LOCK_DATA_UNLOCKED);
 285       if (EFI_ERROR (Status)) {
 286         //
 287         // SetVar fail
 288         //
 289         return Status;
 290       } else {
 291         //
 292         // Unlock Success
 293         //
 294         mMorLockState = MorLockStateUnlocked;
 295         mMorLockKeyEmpty = TRUE;
 296         ZeroMem (mMorLockKey, sizeof(mMorLockKey));
 297         //
 298         // return EFI_ALREADY_STARTED to skip variable set.
 299         //
 300         return EFI_ALREADY_STARTED;
 301       }
 302     } else {
 303       //
 304       // Key mismatch - Prevent Dictionary Attack
 305       //
 306       mMorLockState = MorLockStateLocked;
 307       mMorLockKeyEmpty = TRUE;
 308       ZeroMem (mMorLockKey, sizeof(mMorLockKey));
 309       return EFI_ACCESS_DENIED;
 310     }
 311   }
 312 }
 313
 314 /**
 315   This service is an MOR/MorLock checker handler for the SetVariable().
 316
 317   @param[in]  VariableName the name of the vendor's variable, as a
 318                            Null-Terminated Unicode String
 319   @param[in]  VendorGuid   Unify identifier for vendor.
 320   @param[in]  Attributes   Attributes bitmask to set for the variable.
 321   @param[in]  DataSize     The size in bytes of Data-Buffer.
 322   @param[in]  Data         Point to the content of the variable.
 323
 324   @retval  EFI_SUCCESS            The MOR/MorLock check pass, and Variable
 325                                   driver can store the variable data.
 326   @retval  EFI_INVALID_PARAMETER  The MOR/MorLock data or data size or
 327                                   attributes is not allowed for MOR variable.
 328   @retval  EFI_ACCESS_DENIED      The MOR/MorLock is locked.
 329   @retval  EFI_ALREADY_STARTED    The MorLock variable is handled inside this
 330                                   function. Variable driver can just return
 331                                   EFI_SUCCESS.
 332 **/
 333 EFI_STATUS
 334 SetVariableCheckHandlerMor (
 335   IN CHAR16     *VariableName,
 336   IN EFI_GUID   *VendorGuid,
 337   IN UINT32     Attributes,
 338   IN UINTN      DataSize,
 339   IN VOID       *Data
 340   )
 341 {
 342   //
 343   // do not handle non-MOR variable
 344   //
 345   if (!IsAnyMorVariable (VariableName, VendorGuid)) {
 346     return EFI_SUCCESS;
 347   }
 348
 349   // Permit deletion when policy is disabled.
 350   if (!IsVariablePolicyEnabled() && ((Attributes == 0) || (DataSize == 0))) {
 351     return EFI_SUCCESS;
 352   }
 353
 354   //
 355   // MorLock variable
 356   //
 357   if (IsMorLockVariable (VariableName, VendorGuid)) {
 358     return SetVariableCheckHandlerMorLock (
 359              VariableName,
 360              VendorGuid,
 361              Attributes,
 362              DataSize,
 363              Data
 364              );
 365   }
 366
 367   //
 368   // Mor Variable
 369   //
 370
 371   //
 372   // Permit deletion for passthru request.
 373   //
 374   if (((Attributes == 0) || (DataSize == 0)) && mMorPassThru) {
 375     return EFI_SUCCESS;
 376   }
 377
 378   //
 379   // Basic Check
 380   //
 381   if ((Attributes != (EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_RUNTIME_ACCESS)) ||
 382       (DataSize != sizeof(UINT8)) ||
 383       (Data == NULL)) {
 384     return EFI_INVALID_PARAMETER;
 385   }
 386   if (mMorLockState == MorLockStateLocked) {
 387     //
 388     // If lock, deny access
 389     //
 390     return EFI_ACCESS_DENIED;
 391   }
 392   //
 393   // grant access
 394   //
 395   return EFI_SUCCESS;
 396 }
 397
 398 /**
 399   Initialization for MOR Control Lock.
 400
 401   @retval EFI_SUCCESS     MorLock initialization success.
 402   @return Others          Some error occurs.
 403 **/
 404 EFI_STATUS
 405 MorLockInit (
 406   VOID
 407   )
 408 {
 409   mMorLockInitializationRequired = TRUE;
 410   return EFI_SUCCESS;
 411 }
 412
 413 /**
 414   Delayed initialization for MOR Control Lock at EndOfDxe.
 415
 416   This function performs any operations queued by MorLockInit().
 417 **/
 418 VOID
 419 MorLockInitAtEndOfDxe (
 420   VOID
 421   )
 422 {
 423   UINTN      MorSize;
 424   EFI_STATUS MorStatus;
 425
 426   if (!mMorLockInitializationRequired) {
 427     //
 428     // The EFI_SMM_FAULT_TOLERANT_WRITE_PROTOCOL has never been installed, thus
 429     // the variable write service is unavailable. This should never happen.
 430     //
 431     ASSERT (FALSE);
 432     return;
 433   }
 434
 435   //
 436   // Check if the MOR variable exists.
 437   //
 438   MorSize = 0;
 439   MorStatus = VariableServiceGetVariable (
 440                 MEMORY_OVERWRITE_REQUEST_VARIABLE_NAME,
 441                 &gEfiMemoryOverwriteControlDataGuid,
 442                 NULL,                                   // Attributes
 443                 &MorSize,
 444                 NULL                                    // Data
 445                 );
 446   //
 447   // We provided a zero-sized buffer, so the above call can never succeed.
 448   //
 449   ASSERT (EFI_ERROR (MorStatus));
 450
 451   if (MorStatus == EFI_BUFFER_TOO_SMALL) {
 452     //
 453     // The MOR variable exists.
 454     //
 455     // Some OSes don't follow the TCG's Platform Reset Attack Mitigation spec
 456     // in that the OS should never create the MOR variable, only read and write
 457     // it -- these OSes (unintentionally) create MOR if the platform firmware
 458     // does not produce it. Whether this is the case (from the last OS boot)
 459     // can be deduced from the absence of the TCG / TCG2 protocols, as edk2's
 460     // MOR implementation depends on (one of) those protocols.
 461     //
 462     if (VariableHaveTcgProtocols ()) {
 463       //
 464       // The MOR variable originates from the platform firmware; set the MOR
 465       // Control Lock variable to report the locking capability to the OS.
 466       //
 467       SetMorLockVariable (0);
 468       return;
 469     }
 470
 471     //
 472     // The MOR variable's origin is inexplicable; delete it.
 473     //
 474     DEBUG ((
 475       DEBUG_WARN,
 476       "%a: deleting unexpected / unsupported variable %g:%s\n",
 477       __FUNCTION__,
 478       &gEfiMemoryOverwriteControlDataGuid,
 479       MEMORY_OVERWRITE_REQUEST_VARIABLE_NAME
 480       ));
 481
 482     mMorPassThru = TRUE;
 483     VariableServiceSetVariable (
 484       MEMORY_OVERWRITE_REQUEST_VARIABLE_NAME,
 485       &gEfiMemoryOverwriteControlDataGuid,
 486       0,                                      // Attributes
 487       0,                                      // DataSize
 488       NULL                                    // Data
 489       );
 490     mMorPassThru = FALSE;
 491   }
 492
 493   //
 494   // The MOR variable is absent; the platform firmware does not support it.
 495   // Lock the variable so that no other module may create it.
 496   //
 497   VariableLockRequestToLock (
 498     NULL,                                   // This
 499     MEMORY_OVERWRITE_REQUEST_VARIABLE_NAME,
 500     &gEfiMemoryOverwriteControlDataGuid
 501     );
 502
 503   //
 504   // Delete the MOR Control Lock variable too (should it exists for some
 505   // reason) and prevent other modules from creating it.
 506   //
 507   mMorLockPassThru = TRUE;
 508   VariableServiceSetVariable (
 509     MEMORY_OVERWRITE_REQUEST_CONTROL_LOCK_NAME,
 510     &gEfiMemoryOverwriteRequestControlLockGuid,
 511     0,                                          // Attributes
 512     0,                                          // DataSize
 513     NULL                                        // Data
 514     );
 515   mMorLockPassThru = FALSE;
 516
 517   VariableLockRequestToLock (
 518     NULL,                                       // This
 519     MEMORY_OVERWRITE_REQUEST_CONTROL_LOCK_NAME,
 520     &gEfiMemoryOverwriteRequestControlLockGuid
 521     );
 522 }