forked from rhboot/shim
/
shim.c
1372 lines (1129 loc) · 35.1 KB
/
shim.c
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
/*
* shim - trivial UEFI first-stage bootloader
*
* Copyright 2012 Red Hat, Inc <mjg@redhat.com>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
*
* Significant portions of this code are derived from Tianocore
* (http://tianocore.sf.net) and are Copyright 2009-2012 Intel
* Corporation.
*/
#include <efi.h>
#include <efilib.h>
#include <Library/BaseCryptLib.h>
#include "PeImage.h"
#include "shim.h"
#include "signature.h"
#include "netboot.h"
#define SECOND_STAGE L"\\grub.efi"
#define MOK_MANAGER L"\\MokManager.efi"
static EFI_SYSTEM_TABLE *systab;
static EFI_STATUS (EFIAPI *entry_point) (EFI_HANDLE image_handle, EFI_SYSTEM_TABLE *system_table);
/*
* The vendor certificate used for validating the second stage loader
*/
extern UINT8 vendor_cert[];
extern UINT32 vendor_cert_size;
extern EFI_SIGNATURE_LIST *vendor_dbx;
extern UINT32 vendor_dbx_size;
#define EFI_IMAGE_SECURITY_DATABASE_GUID { 0xd719b2cb, 0x3d3a, 0x4596, { 0xa3, 0xbc, 0xda, 0xd0, 0x0e, 0x67, 0x65, 0x6f }}
static UINT8 insecure_mode;
typedef enum {
DATA_FOUND,
DATA_NOT_FOUND,
VAR_NOT_FOUND
} CHECK_STATUS;
typedef struct {
UINT32 MokSize;
UINT8 *Mok;
} MokListNode;
static EFI_STATUS get_variable (CHAR16 *name, EFI_GUID guid, UINT32 *attributes,
UINTN *size, void **buffer)
{
EFI_STATUS efi_status;
char allocate = !(*size);
efi_status = uefi_call_wrapper(RT->GetVariable, 5, name, &guid,
attributes, size, buffer);
if (efi_status != EFI_BUFFER_TOO_SMALL || !allocate) {
return efi_status;
}
*buffer = AllocatePool(*size);
if (!*buffer) {
Print(L"Unable to allocate variable buffer\n");
return EFI_OUT_OF_RESOURCES;
}
efi_status = uefi_call_wrapper(RT->GetVariable, 5, name, &guid,
attributes, size, *buffer);
return efi_status;
}
/*
* Perform basic bounds checking of the intra-image pointers
*/
static void *ImageAddress (void *image, int size, unsigned int address)
{
if (address > size)
return NULL;
return image + address;
}
/*
* Perform the actual relocation
*/
static EFI_STATUS relocate_coff (PE_COFF_LOADER_IMAGE_CONTEXT *context,
void *data)
{
EFI_IMAGE_BASE_RELOCATION *RelocBase, *RelocBaseEnd;
UINT64 Adjust;
UINT16 *Reloc, *RelocEnd;
char *Fixup, *FixupBase, *FixupData = NULL;
UINT16 *Fixup16;
UINT32 *Fixup32;
UINT64 *Fixup64;
int size = context->ImageSize;
void *ImageEnd = (char *)data + size;
context->PEHdr->Pe32Plus.OptionalHeader.ImageBase = (UINT64)data;
if (context->NumberOfRvaAndSizes <= EFI_IMAGE_DIRECTORY_ENTRY_BASERELOC) {
Print(L"Image has no relocation entry\n");
return EFI_UNSUPPORTED;
}
RelocBase = ImageAddress(data, size, context->RelocDir->VirtualAddress);
RelocBaseEnd = ImageAddress(data, size, context->RelocDir->VirtualAddress + context->RelocDir->Size - 1);
if (!RelocBase || !RelocBaseEnd) {
Print(L"Reloc table overflows binary\n");
return EFI_UNSUPPORTED;
}
Adjust = (UINT64)data - context->ImageAddress;
while (RelocBase < RelocBaseEnd) {
Reloc = (UINT16 *) ((char *) RelocBase + sizeof (EFI_IMAGE_BASE_RELOCATION));
RelocEnd = (UINT16 *) ((char *) RelocBase + RelocBase->SizeOfBlock);
if ((void *)RelocEnd < data || (void *)RelocEnd > ImageEnd) {
Print(L"Reloc entry overflows binary\n");
return EFI_UNSUPPORTED;
}
FixupBase = ImageAddress(data, size, RelocBase->VirtualAddress);
if (!FixupBase) {
Print(L"Invalid fixupbase\n");
return EFI_UNSUPPORTED;
}
while (Reloc < RelocEnd) {
Fixup = FixupBase + (*Reloc & 0xFFF);
switch ((*Reloc) >> 12) {
case EFI_IMAGE_REL_BASED_ABSOLUTE:
break;
case EFI_IMAGE_REL_BASED_HIGH:
Fixup16 = (UINT16 *) Fixup;
*Fixup16 = (UINT16) (*Fixup16 + ((UINT16) ((UINT32) Adjust >> 16)));
if (FixupData != NULL) {
*(UINT16 *) FixupData = *Fixup16;
FixupData = FixupData + sizeof (UINT16);
}
break;
case EFI_IMAGE_REL_BASED_LOW:
Fixup16 = (UINT16 *) Fixup;
*Fixup16 = (UINT16) (*Fixup16 + (UINT16) Adjust);
if (FixupData != NULL) {
*(UINT16 *) FixupData = *Fixup16;
FixupData = FixupData + sizeof (UINT16);
}
break;
case EFI_IMAGE_REL_BASED_HIGHLOW:
Fixup32 = (UINT32 *) Fixup;
*Fixup32 = *Fixup32 + (UINT32) Adjust;
if (FixupData != NULL) {
FixupData = ALIGN_POINTER (FixupData, sizeof (UINT32));
*(UINT32 *)FixupData = *Fixup32;
FixupData = FixupData + sizeof (UINT32);
}
break;
case EFI_IMAGE_REL_BASED_DIR64:
Fixup64 = (UINT64 *) Fixup;
*Fixup64 = *Fixup64 + (UINT64) Adjust;
if (FixupData != NULL) {
FixupData = ALIGN_POINTER (FixupData, sizeof(UINT64));
*(UINT64 *)(FixupData) = *Fixup64;
FixupData = FixupData + sizeof(UINT64);
}
break;
default:
Print(L"Unknown relocation\n");
return EFI_UNSUPPORTED;
}
Reloc += 1;
}
RelocBase = (EFI_IMAGE_BASE_RELOCATION *) RelocEnd;
}
return EFI_SUCCESS;
}
static CHECK_STATUS check_db_cert_in_ram(EFI_SIGNATURE_LIST *CertList,
UINTN dbsize,
WIN_CERTIFICATE_EFI_PKCS *data,
UINT8 *hash)
{
EFI_SIGNATURE_DATA *Cert;
UINTN CertCount, Index;
BOOLEAN IsFound = FALSE;
EFI_GUID CertType = EfiCertX509Guid;
while ((dbsize > 0) && (dbsize >= CertList->SignatureListSize)) {
if (CompareGuid (&CertList->SignatureType, &CertType) == 0) {
CertCount = (CertList->SignatureListSize - CertList->SignatureHeaderSize) / CertList->SignatureSize;
Cert = (EFI_SIGNATURE_DATA *) ((UINT8 *) CertList + sizeof (EFI_SIGNATURE_LIST) + CertList->SignatureHeaderSize);
for (Index = 0; Index < CertCount; Index++) {
IsFound = AuthenticodeVerify (data->CertData,
data->Hdr.dwLength - sizeof(data->Hdr),
Cert->SignatureData,
CertList->SignatureSize,
hash, SHA256_DIGEST_SIZE);
if (IsFound)
break;
Cert = (EFI_SIGNATURE_DATA *) ((UINT8 *) Cert + CertList->SignatureSize);
}
}
if (IsFound)
break;
dbsize -= CertList->SignatureListSize;
CertList = (EFI_SIGNATURE_LIST *) ((UINT8 *) CertList + CertList->SignatureListSize);
}
if (IsFound)
return DATA_FOUND;
return DATA_NOT_FOUND;
}
static CHECK_STATUS check_db_cert(CHAR16 *dbname, EFI_GUID guid,
WIN_CERTIFICATE_EFI_PKCS *data, UINT8 *hash)
{
CHECK_STATUS rc;
EFI_STATUS efi_status;
EFI_SIGNATURE_LIST *CertList;
UINTN dbsize = 0;
UINT32 attributes;
void *db;
efi_status = get_variable(dbname, guid, &attributes, &dbsize, &db);
if (efi_status != EFI_SUCCESS)
return VAR_NOT_FOUND;
CertList = db;
rc = check_db_cert_in_ram(CertList, dbsize, data, hash);
FreePool(db);
return rc;
}
/*
* Check a hash against an EFI_SIGNATURE_LIST in a buffer
*/
static CHECK_STATUS check_db_hash_in_ram(EFI_SIGNATURE_LIST *CertList,
UINTN dbsize, UINT8 *data,
int SignatureSize, EFI_GUID CertType)
{
EFI_SIGNATURE_DATA *Cert;
UINTN CertCount, Index;
BOOLEAN IsFound = FALSE;
while ((dbsize > 0) && (dbsize >= CertList->SignatureListSize)) {
CertCount = (CertList->SignatureListSize - CertList->SignatureHeaderSize) / CertList->SignatureSize;
Cert = (EFI_SIGNATURE_DATA *) ((UINT8 *) CertList + sizeof (EFI_SIGNATURE_LIST) + CertList->SignatureHeaderSize);
if (CompareGuid(&CertList->SignatureType, &CertType) == 0) {
for (Index = 0; Index < CertCount; Index++) {
if (CompareMem (Cert->SignatureData, data, SignatureSize) == 0) {
//
// Find the signature in database.
//
IsFound = TRUE;
break;
}
Cert = (EFI_SIGNATURE_DATA *) ((UINT8 *) Cert + CertList->SignatureSize);
}
if (IsFound) {
break;
}
}
dbsize -= CertList->SignatureListSize;
CertList = (EFI_SIGNATURE_LIST *) ((UINT8 *) CertList + CertList->SignatureListSize);
}
if (IsFound)
return DATA_FOUND;
return DATA_NOT_FOUND;
}
/*
* Check a hash against an EFI_SIGNATURE_LIST in a UEFI variable
*/
static CHECK_STATUS check_db_hash(CHAR16 *dbname, EFI_GUID guid, UINT8 *data,
int SignatureSize, EFI_GUID CertType)
{
EFI_STATUS efi_status;
EFI_SIGNATURE_LIST *CertList;
UINT32 attributes;
UINTN dbsize = 0;
void *db;
efi_status = get_variable(dbname, guid, &attributes, &dbsize, &db);
if (efi_status != EFI_SUCCESS) {
return VAR_NOT_FOUND;
}
CertList = db;
CHECK_STATUS rc = check_db_hash_in_ram(CertList, dbsize, data,
SignatureSize, CertType);
FreePool(db);
return rc;
}
/*
* Check whether the binary signature or hash are present in dbx or the
* built-in blacklist
*/
static EFI_STATUS check_blacklist (WIN_CERTIFICATE_EFI_PKCS *cert,
UINT8 *sha256hash, UINT8 *sha1hash)
{
EFI_GUID secure_var = EFI_IMAGE_SECURITY_DATABASE_GUID;
if (check_db_hash_in_ram(vendor_dbx, vendor_dbx_size, sha256hash,
SHA256_DIGEST_SIZE, EfiHashSha256Guid) ==
DATA_FOUND)
return EFI_ACCESS_DENIED;
if (check_db_hash_in_ram(vendor_dbx, vendor_dbx_size, sha1hash,
SHA1_DIGEST_SIZE, EfiHashSha1Guid) ==
DATA_FOUND)
return EFI_ACCESS_DENIED;
if (check_db_cert_in_ram(vendor_dbx, vendor_dbx_size, cert,
sha256hash) == DATA_FOUND)
return EFI_ACCESS_DENIED;
if (check_db_hash(L"dbx", secure_var, sha256hash, SHA256_DIGEST_SIZE,
EfiHashSha256Guid) == DATA_FOUND)
return EFI_ACCESS_DENIED;
if (check_db_hash(L"dbx", secure_var, sha1hash, SHA1_DIGEST_SIZE,
EfiHashSha1Guid) == DATA_FOUND)
return EFI_ACCESS_DENIED;
if (check_db_cert(L"dbx", secure_var, cert, sha256hash) == DATA_FOUND)
return EFI_ACCESS_DENIED;
return EFI_SUCCESS;
}
/*
* Check whether the binary signature or hash are present in db or MokList
*/
static EFI_STATUS check_whitelist (WIN_CERTIFICATE_EFI_PKCS *cert,
UINT8 *sha256hash, UINT8 *sha1hash)
{
EFI_GUID secure_var = EFI_IMAGE_SECURITY_DATABASE_GUID;
EFI_GUID shim_var = SHIM_LOCK_GUID;
if (check_db_hash(L"db", secure_var, sha256hash, SHA256_DIGEST_SIZE,
EfiHashSha256Guid) == DATA_FOUND)
return EFI_SUCCESS;
if (check_db_hash(L"db", secure_var, sha1hash, SHA1_DIGEST_SIZE,
EfiHashSha1Guid) == DATA_FOUND)
return EFI_SUCCESS;
if (check_db_hash(L"MokList", shim_var, sha256hash, SHA256_DIGEST_SIZE,
EfiHashSha256Guid) == DATA_FOUND)
return EFI_SUCCESS;
if (check_db_cert(L"db", secure_var, cert, sha256hash) == DATA_FOUND)
return EFI_SUCCESS;
if (check_db_cert(L"MokList", shim_var, cert, sha256hash) == DATA_FOUND)
return EFI_SUCCESS;
return EFI_ACCESS_DENIED;
}
/*
* Check whether we're in Secure Boot and user mode
*/
static BOOLEAN secure_mode (void)
{
EFI_STATUS status;
EFI_GUID global_var = EFI_GLOBAL_VARIABLE;
UINTN charsize = sizeof(char);
UINT8 sb, setupmode;
UINT32 attributes;
if (insecure_mode)
return FALSE;
status = get_variable(L"SecureBoot", global_var, &attributes, &charsize,
(void *)&sb);
/* FIXME - more paranoia here? */
if (status != EFI_SUCCESS || sb != 1) {
Print(L"Secure boot not enabled\n");
return FALSE;
}
status = get_variable(L"SetupMode", global_var, &attributes, &charsize,
(void *)&setupmode);
if (status == EFI_SUCCESS && setupmode == 1) {
Print(L"Platform is in setup mode\n");
return FALSE;
}
return TRUE;
}
/*
* Calculate the SHA1 and SHA256 hashes of a binary
*/
static EFI_STATUS generate_hash (char *data, int datasize,
PE_COFF_LOADER_IMAGE_CONTEXT *context,
UINT8 *sha256hash, UINT8 *sha1hash)
{
unsigned int sha256ctxsize, sha1ctxsize;
unsigned int size = datasize;
void *sha256ctx = NULL, *sha1ctx = NULL;
char *hashbase;
unsigned int hashsize;
unsigned int SumOfBytesHashed, SumOfSectionBytes;
unsigned int index, pos;
EFI_IMAGE_SECTION_HEADER *Section;
EFI_IMAGE_SECTION_HEADER *SectionHeader = NULL;
EFI_IMAGE_SECTION_HEADER *SectionCache;
EFI_STATUS status = EFI_SUCCESS;
sha256ctxsize = Sha256GetContextSize();
sha256ctx = AllocatePool(sha256ctxsize);
sha1ctxsize = Sha1GetContextSize();
sha1ctx = AllocatePool(sha1ctxsize);
if (!sha256ctx || !sha1ctx) {
Print(L"Unable to allocate memory for hash context\n");
return EFI_OUT_OF_RESOURCES;
}
if (!Sha256Init(sha256ctx) || !Sha1Init(sha1ctx)) {
Print(L"Unable to initialise hash\n");
status = EFI_OUT_OF_RESOURCES;
goto done;
}
/* Hash start to checksum */
hashbase = data;
hashsize = (char *)&context->PEHdr->Pe32.OptionalHeader.CheckSum -
hashbase;
if (!(Sha256Update(sha256ctx, hashbase, hashsize)) ||
!(Sha1Update(sha1ctx, hashbase, hashsize))) {
Print(L"Unable to generate hash\n");
status = EFI_OUT_OF_RESOURCES;
goto done;
}
/* Hash post-checksum to start of certificate table */
hashbase = (char *)&context->PEHdr->Pe32.OptionalHeader.CheckSum +
sizeof (int);
hashsize = (char *)context->SecDir - hashbase;
if (!(Sha256Update(sha256ctx, hashbase, hashsize)) ||
!(Sha1Update(sha1ctx, hashbase, hashsize))) {
Print(L"Unable to generate hash\n");
status = EFI_OUT_OF_RESOURCES;
goto done;
}
/* Hash end of certificate table to end of image header */
hashbase = (char *) &context->PEHdr->Pe32Plus.OptionalHeader.DataDirectory[EFI_IMAGE_DIRECTORY_ENTRY_SECURITY + 1];
hashsize = context->PEHdr->Pe32Plus.OptionalHeader.SizeOfHeaders -
(int) ((char *) (&context->PEHdr->Pe32Plus.OptionalHeader.DataDirectory[EFI_IMAGE_DIRECTORY_ENTRY_SECURITY + 1]) - data);
if (!(Sha256Update(sha256ctx, hashbase, hashsize)) ||
!(Sha1Update(sha1ctx, hashbase, hashsize))) {
Print(L"Unable to generate hash\n");
status = EFI_OUT_OF_RESOURCES;
goto done;
}
/* Sort sections */
SumOfBytesHashed = context->PEHdr->Pe32Plus.OptionalHeader.SizeOfHeaders;
Section = (EFI_IMAGE_SECTION_HEADER *) (
(char *)context->PEHdr + sizeof (UINT32) +
sizeof (EFI_IMAGE_FILE_HEADER) +
context->PEHdr->Pe32.FileHeader.SizeOfOptionalHeader
);
SectionCache = Section;
for (index = 0, SumOfSectionBytes = 0; index < context->PEHdr->Pe32.FileHeader.NumberOfSections; index++, SectionCache++) {
SumOfSectionBytes += SectionCache->SizeOfRawData;
}
if (SumOfSectionBytes >= datasize) {
Print(L"Malformed binary: %x %x\n", SumOfSectionBytes, size);
status = EFI_INVALID_PARAMETER;
goto done;
}
SectionHeader = (EFI_IMAGE_SECTION_HEADER *) AllocateZeroPool (sizeof (EFI_IMAGE_SECTION_HEADER) * context->PEHdr->Pe32.FileHeader.NumberOfSections);
if (SectionHeader == NULL) {
Print(L"Unable to allocate section header\n");
status = EFI_OUT_OF_RESOURCES;
goto done;
}
/* Sort the section headers */
for (index = 0; index < context->PEHdr->Pe32.FileHeader.NumberOfSections; index++) {
pos = index;
while ((pos > 0) && (Section->PointerToRawData < SectionHeader[pos - 1].PointerToRawData)) {
CopyMem (&SectionHeader[pos], &SectionHeader[pos - 1], sizeof (EFI_IMAGE_SECTION_HEADER));
pos--;
}
CopyMem (&SectionHeader[pos], Section, sizeof (EFI_IMAGE_SECTION_HEADER));
Section += 1;
}
/* Hash the sections */
for (index = 0; index < context->PEHdr->Pe32.FileHeader.NumberOfSections; index++) {
Section = &SectionHeader[index];
if (Section->SizeOfRawData == 0) {
continue;
}
hashbase = ImageAddress(data, size, Section->PointerToRawData);
hashsize = (unsigned int) Section->SizeOfRawData;
if (!hashbase) {
Print(L"Malformed section header\n");
status = EFI_INVALID_PARAMETER;
goto done;
}
if (!(Sha256Update(sha256ctx, hashbase, hashsize)) ||
!(Sha1Update(sha1ctx, hashbase, hashsize))) {
Print(L"Unable to generate hash\n");
status = EFI_OUT_OF_RESOURCES;
goto done;
}
SumOfBytesHashed += Section->SizeOfRawData;
}
/* Hash all remaining data */
if (size > SumOfBytesHashed) {
hashbase = data + SumOfBytesHashed;
hashsize = (unsigned int)(
size -
context->PEHdr->Pe32Plus.OptionalHeader.DataDirectory[EFI_IMAGE_DIRECTORY_ENTRY_SECURITY].Size -
SumOfBytesHashed);
if (!(Sha256Update(sha256ctx, hashbase, hashsize)) ||
!(Sha1Update(sha1ctx, hashbase, hashsize))) {
Print(L"Unable to generate hash\n");
status = EFI_OUT_OF_RESOURCES;
goto done;
}
}
if (!(Sha256Final(sha256ctx, sha256hash)) ||
!(Sha1Final(sha1ctx, sha1hash))) {
Print(L"Unable to finalise hash\n");
status = EFI_OUT_OF_RESOURCES;
goto done;
}
done:
if (SectionHeader)
FreePool(SectionHeader);
if (sha1ctx)
FreePool(sha1ctx);
if (sha256ctx)
FreePool(sha256ctx);
return status;
}
/*
* Ensure that the MOK database hasn't been set or modified from an OS
*/
static EFI_STATUS verify_mok (void) {
EFI_GUID shim_lock_guid = SHIM_LOCK_GUID;
EFI_STATUS status = EFI_SUCCESS;
void *MokListData = NULL;
UINTN MokListDataSize = 0;
UINT32 attributes;
status = get_variable(L"MokList", shim_lock_guid, &attributes,
&MokListDataSize, &MokListData);
if (attributes & EFI_VARIABLE_RUNTIME_ACCESS) {
Print(L"MokList is compromised!\nErase all keys in MokList!\n");
if (LibDeleteVariable(L"MokList", &shim_lock_guid) != EFI_SUCCESS) {
Print(L"Failed to erase MokList\n");
}
status = EFI_ACCESS_DENIED;
return status;
}
return EFI_SUCCESS;
}
/*
* Check that the signature is valid and matches the binary
*/
static EFI_STATUS verify_buffer (char *data, int datasize,
PE_COFF_LOADER_IMAGE_CONTEXT *context)
{
UINT8 sha256hash[SHA256_DIGEST_SIZE];
UINT8 sha1hash[SHA1_DIGEST_SIZE];
EFI_STATUS status = EFI_ACCESS_DENIED;
WIN_CERTIFICATE_EFI_PKCS *cert;
unsigned int size = datasize;
if (context->SecDir->Size == 0) {
Print(L"Empty security header\n");
return EFI_INVALID_PARAMETER;
}
cert = ImageAddress (data, size, context->SecDir->VirtualAddress);
if (!cert) {
Print(L"Certificate located outside the image\n");
return EFI_INVALID_PARAMETER;
}
if (cert->Hdr.wCertificateType != WIN_CERT_TYPE_PKCS_SIGNED_DATA) {
Print(L"Unsupported certificate type %x\n",
cert->Hdr.wCertificateType);
return EFI_UNSUPPORTED;
}
status = generate_hash(data, datasize, context, sha256hash, sha1hash);
if (status != EFI_SUCCESS)
return status;
/*
* Check that the MOK database hasn't been modified
*/
verify_mok();
/*
* Ensure that the binary isn't blacklisted
*/
status = check_blacklist(cert, sha256hash, sha1hash);
if (status != EFI_SUCCESS) {
Print(L"Binary is blacklisted\n");
return status;
}
/*
* Check whether the binary is whitelisted in any of the firmware
* databases
*/
status = check_whitelist(cert, sha256hash, sha1hash);
if (status == EFI_SUCCESS) {
Print(L"Binary is whitelisted\n");
return status;
}
/*
* And finally, check against shim's built-in key
*/
if (AuthenticodeVerify(cert->CertData,
context->SecDir->Size - sizeof(cert->Hdr),
vendor_cert, vendor_cert_size, sha256hash,
SHA256_DIGEST_SIZE)) {
status = EFI_SUCCESS;
Print(L"Binary is verified by the vendor certificate\n");
return status;
}
Print(L"Invalid signature\n");
status = EFI_ACCESS_DENIED;
return status;
}
/*
* Read the binary header and grab appropriate information from it
*/
static EFI_STATUS read_header(void *data, unsigned int datasize,
PE_COFF_LOADER_IMAGE_CONTEXT *context)
{
EFI_IMAGE_DOS_HEADER *DosHdr = data;
EFI_IMAGE_OPTIONAL_HEADER_UNION *PEHdr = data;
if (datasize < sizeof(EFI_IMAGE_DOS_HEADER)) {
Print(L"Invalid image\n");
return EFI_UNSUPPORTED;
}
if (DosHdr->e_magic == EFI_IMAGE_DOS_SIGNATURE)
PEHdr = (EFI_IMAGE_OPTIONAL_HEADER_UNION *)((char *)data + DosHdr->e_lfanew);
if ((((UINT8 *)PEHdr - (UINT8 *)data) + sizeof(EFI_IMAGE_OPTIONAL_HEADER_UNION)) > datasize) {
Print(L"Invalid image\n");
return EFI_UNSUPPORTED;
}
if (PEHdr->Te.Signature != EFI_IMAGE_NT_SIGNATURE) {
Print(L"Unsupported image type\n");
return EFI_UNSUPPORTED;
}
if (PEHdr->Pe32.FileHeader.Characteristics & EFI_IMAGE_FILE_RELOCS_STRIPPED) {
Print(L"Unsupported image - Relocations have been stripped\n");
return EFI_UNSUPPORTED;
}
if (PEHdr->Pe32.OptionalHeader.Magic != EFI_IMAGE_NT_OPTIONAL_HDR64_MAGIC) {
Print(L"Only 64-bit images supported\n");
return EFI_UNSUPPORTED;
}
context->PEHdr = PEHdr;
context->ImageAddress = PEHdr->Pe32Plus.OptionalHeader.ImageBase;
context->ImageSize = (UINT64)PEHdr->Pe32Plus.OptionalHeader.SizeOfImage;
context->SizeOfHeaders = PEHdr->Pe32Plus.OptionalHeader.SizeOfHeaders;
context->EntryPoint = PEHdr->Pe32Plus.OptionalHeader.AddressOfEntryPoint;
context->RelocDir = &PEHdr->Pe32Plus.OptionalHeader.DataDirectory[EFI_IMAGE_DIRECTORY_ENTRY_BASERELOC];
context->NumberOfRvaAndSizes = PEHdr->Pe32Plus.OptionalHeader.NumberOfRvaAndSizes;
context->NumberOfSections = PEHdr->Pe32.FileHeader.NumberOfSections;
context->FirstSection = (EFI_IMAGE_SECTION_HEADER *)((char *)PEHdr + PEHdr->Pe32.FileHeader.SizeOfOptionalHeader + sizeof(UINT32) + sizeof(EFI_IMAGE_FILE_HEADER));
context->SecDir = (EFI_IMAGE_DATA_DIRECTORY *) &PEHdr->Pe32Plus.OptionalHeader.DataDirectory[EFI_IMAGE_DIRECTORY_ENTRY_SECURITY];
if (context->ImageSize < context->SizeOfHeaders) {
Print(L"Invalid image\n");
return EFI_UNSUPPORTED;
}
if (((UINT8 *)context->SecDir - (UINT8 *)data) > (datasize - sizeof(EFI_IMAGE_DATA_DIRECTORY))) {
Print(L"Invalid image\n");
return EFI_UNSUPPORTED;
}
if (context->SecDir->VirtualAddress >= datasize) {
Print(L"Malformed security header\n");
return EFI_INVALID_PARAMETER;
}
return EFI_SUCCESS;
}
/*
* Once the image has been loaded it needs to be validated and relocated
*/
static EFI_STATUS handle_image (void *data, unsigned int datasize,
EFI_LOADED_IMAGE *li)
{
EFI_STATUS efi_status;
char *buffer;
int i, size;
EFI_IMAGE_SECTION_HEADER *Section;
char *base, *end;
PE_COFF_LOADER_IMAGE_CONTEXT context;
/*
* The binary header contains relevant context and section pointers
*/
efi_status = read_header(data, datasize, &context);
if (efi_status != EFI_SUCCESS) {
Print(L"Failed to read header\n");
return efi_status;
}
/*
* We only need to verify the binary if we're in secure mode
*/
if (secure_mode ()) {
efi_status = verify_buffer(data, datasize, &context);
if (efi_status != EFI_SUCCESS) {
Print(L"Verification failed\n");
return efi_status;
}
}
buffer = AllocatePool(context.ImageSize);
if (!buffer) {
Print(L"Failed to allocate image buffer\n");
return EFI_OUT_OF_RESOURCES;
}
CopyMem(buffer, data, context.SizeOfHeaders);
/*
* Copy the executable's sections to their desired offsets
*/
Section = context.FirstSection;
for (i = 0; i < context.NumberOfSections; i++) {
size = Section->Misc.VirtualSize;
if (size > Section->SizeOfRawData)
size = Section->SizeOfRawData;
base = ImageAddress (buffer, context.ImageSize, Section->VirtualAddress);
end = ImageAddress (buffer, context.ImageSize, Section->VirtualAddress + size - 1);
if (!base || !end) {
Print(L"Invalid section size\n");
return EFI_UNSUPPORTED;
}
if (Section->SizeOfRawData > 0)
CopyMem(base, data + Section->PointerToRawData, size);
if (size < Section->Misc.VirtualSize)
ZeroMem (base + size, Section->Misc.VirtualSize - size);
Section += 1;
}
/*
* Run the relocation fixups
*/
efi_status = relocate_coff(&context, buffer);
if (efi_status != EFI_SUCCESS) {
Print(L"Relocation failed\n");
FreePool(buffer);
return efi_status;
}
entry_point = ImageAddress(buffer, context.ImageSize, context.EntryPoint);
/*
* grub needs to know its location and size in memory, so fix up
* the loaded image protocol values
*/
li->ImageBase = buffer;
li->ImageSize = context.ImageSize;
if (!entry_point) {
Print(L"Invalid entry point\n");
FreePool(buffer);
return EFI_UNSUPPORTED;
}
return EFI_SUCCESS;
}
/*
* Generate the path of an executable given shim's path and the name
* of the executable
*/
static EFI_STATUS generate_path(EFI_LOADED_IMAGE *li, CHAR16 *ImagePath,
EFI_DEVICE_PATH **grubpath, CHAR16 **PathName)
{
EFI_DEVICE_PATH *devpath;
EFI_HANDLE device;
int i;
unsigned int pathlen = 0;
EFI_STATUS efi_status = EFI_SUCCESS;
CHAR16 *bootpath;
device = li->DeviceHandle;
devpath = li->FilePath;
bootpath = DevicePathToStr(devpath);
pathlen = StrLen(bootpath);
for (i=pathlen; i>0; i--) {
if (bootpath[i] == '\\')
break;
}
bootpath[i+1] = '\0';
if (i == 0 || bootpath[i-i] == '\\')
bootpath[i] = '\0';
*PathName = AllocatePool(StrSize(bootpath) + StrSize(ImagePath));
if (!*PathName) {
Print(L"Failed to allocate path buffer\n");
efi_status = EFI_OUT_OF_RESOURCES;
goto error;
}
*PathName[0] = '\0';
StrCat(*PathName, bootpath);
StrCat(*PathName, ImagePath);
*grubpath = FileDevicePath(device, *PathName);
error:
return efi_status;
}
/*
* Open the second stage bootloader and read it into a buffer
*/
static EFI_STATUS load_image (EFI_LOADED_IMAGE *li, void **data,
int *datasize, CHAR16 *PathName)
{
EFI_GUID simple_file_system_protocol = SIMPLE_FILE_SYSTEM_PROTOCOL;
EFI_GUID file_info_id = EFI_FILE_INFO_ID;
EFI_STATUS efi_status;
EFI_HANDLE device;
EFI_FILE_INFO *fileinfo = NULL;
EFI_FILE_IO_INTERFACE *drive;
EFI_FILE *root, *grub;
UINTN buffersize = sizeof(EFI_FILE_INFO);
device = li->DeviceHandle;
/*
* Open the device
*/
efi_status = uefi_call_wrapper(BS->HandleProtocol, 3, device,
&simple_file_system_protocol,
(void **)&drive);
if (efi_status != EFI_SUCCESS) {
Print(L"Failed to find fs\n");
goto error;
}
efi_status = uefi_call_wrapper(drive->OpenVolume, 2, drive, &root);
if (efi_status != EFI_SUCCESS) {
Print(L"Failed to open fs\n");
goto error;
}
/*
* And then open the file
*/
efi_status = uefi_call_wrapper(root->Open, 5, root, &grub, PathName,
EFI_FILE_MODE_READ, 0);
if (efi_status != EFI_SUCCESS) {
Print(L"Failed to open %s - %lx\n", PathName, efi_status);
goto error;
}
fileinfo = AllocatePool(buffersize);
if (!fileinfo) {
Print(L"Unable to allocate file info buffer\n");
efi_status = EFI_OUT_OF_RESOURCES;
goto error;
}
/*
* Find out how big the file is in order to allocate the storage
* buffer
*/
efi_status = uefi_call_wrapper(grub->GetInfo, 4, grub, &file_info_id,
&buffersize, fileinfo);
if (efi_status == EFI_BUFFER_TOO_SMALL) {
FreePool(fileinfo);
fileinfo = AllocatePool(buffersize);
if (!fileinfo) {
Print(L"Unable to allocate file info buffer\n");
efi_status = EFI_OUT_OF_RESOURCES;
goto error;
}
efi_status = uefi_call_wrapper(grub->GetInfo, 4, grub,
&file_info_id, &buffersize,
fileinfo);