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23c3178c BB |
1 | /** @file\r |
2 | This module verifies that Enhanced Key Usages (EKU's) are present within\r | |
3 | a PKCS7 signature blob using OpenSSL.\r | |
4 | \r | |
5 | Copyright (C) Microsoft Corporation. All Rights Reserved.\r | |
6 | Copyright (c) 2019, Intel Corporation. All rights reserved.<BR>\r | |
7 | \r | |
8 | SPDX-License-Identifier: BSD-2-Clause-Patent\r | |
9 | \r | |
10 | **/\r | |
11 | \r | |
12 | #include <Base.h>\r | |
13 | #include "InternalCryptLib.h"\r | |
14 | #include <openssl/x509v3.h>\r | |
15 | #include <openssl/asn1.h>\r | |
16 | #include <openssl/x509.h>\r | |
17 | #include <openssl/bio.h>\r | |
18 | #include <internal/x509_int.h>\r | |
19 | #include <openssl/pkcs7.h>\r | |
20 | #include <openssl/bn.h>\r | |
21 | #include <openssl/x509_vfy.h>\r | |
22 | #include <openssl/pem.h>\r | |
23 | #include <openssl/evp.h>\r | |
24 | #include <internal/asn1_int.h>\r | |
25 | \r | |
26 | /**\r | |
27 | This function will return the leaf signer certificate in a chain. This is\r | |
28 | required because certificate chains are not guaranteed to have the\r | |
29 | certificates in the order that they were issued.\r | |
30 | \r | |
31 | A typical certificate chain looks like this:\r | |
32 | \r | |
33 | \r | |
34 | ----------------------------\r | |
35 | | Root |\r | |
36 | ----------------------------\r | |
37 | ^\r | |
38 | |\r | |
39 | ----------------------------\r | |
40 | | Policy CA | <-- Typical Trust Anchor.\r | |
41 | ----------------------------\r | |
42 | ^\r | |
43 | |\r | |
44 | ----------------------------\r | |
45 | | Issuing CA |\r | |
46 | ----------------------------\r | |
47 | ^\r | |
48 | |\r | |
49 | -----------------------------\r | |
50 | / End-Entity (leaf) signer / <-- Bottom certificate.\r | |
51 | ----------------------------- EKU: "1.3.6.1.4.1.311.76.9.21.1"\r | |
52 | (Firmware Signing)\r | |
53 | \r | |
54 | \r | |
55 | @param[in] CertChain Certificate chain.\r | |
56 | \r | |
57 | @param[out] SignerCert Last certificate in the chain. For PKCS7 signatures,\r | |
58 | this will be the end-entity (leaf) signer cert.\r | |
59 | \r | |
60 | @retval EFI_SUCCESS The required EKUs were found in the signature.\r | |
61 | @retval EFI_INVALID_PARAMETER A parameter was invalid.\r | |
62 | @retval EFI_NOT_FOUND The number of signers found was not 1.\r | |
63 | \r | |
64 | **/\r | |
65 | EFI_STATUS\r | |
66 | GetSignerCertificate (\r | |
67 | IN CONST PKCS7 *CertChain,\r | |
68 | OUT X509 **SignerCert\r | |
69 | )\r | |
70 | {\r | |
71 | EFI_STATUS Status;\r | |
72 | STACK_OF(X509) *Signers;\r | |
73 | INT32 NumberSigners;\r | |
74 | \r | |
75 | Status = EFI_SUCCESS;\r | |
76 | Signers = NULL;\r | |
77 | NumberSigners = 0;\r | |
78 | \r | |
79 | if (CertChain == NULL || SignerCert == NULL) {\r | |
80 | Status = EFI_INVALID_PARAMETER;\r | |
81 | goto Exit;\r | |
82 | }\r | |
83 | \r | |
84 | //\r | |
85 | // Get the signers from the chain.\r | |
86 | //\r | |
87 | Signers = PKCS7_get0_signers ((PKCS7*) CertChain, NULL, PKCS7_BINARY);\r | |
88 | if (Signers == NULL) {\r | |
89 | //\r | |
90 | // Fail to get signers form PKCS7\r | |
91 | //\r | |
92 | Status = EFI_INVALID_PARAMETER;\r | |
93 | goto Exit;\r | |
94 | }\r | |
95 | \r | |
96 | //\r | |
97 | // There should only be one signer in the PKCS7 stack.\r | |
98 | //\r | |
99 | NumberSigners = sk_X509_num (Signers);\r | |
100 | if (NumberSigners != 1) {\r | |
101 | //\r | |
102 | // The number of singers should have been 1\r | |
103 | //\r | |
104 | Status = EFI_NOT_FOUND;\r | |
105 | goto Exit;\r | |
106 | }\r | |
107 | \r | |
108 | *SignerCert = sk_X509_value (Signers, 0);\r | |
109 | \r | |
110 | Exit:\r | |
111 | //\r | |
112 | // Release Resources\r | |
113 | //\r | |
b3d00df6 | 114 | if (Signers != NULL) {\r |
23c3178c BB |
115 | sk_X509_free (Signers);\r |
116 | }\r | |
117 | \r | |
118 | return Status;\r | |
119 | }\r | |
120 | \r | |
121 | \r | |
122 | /**\r | |
123 | Determines if the specified EKU represented in ASN1 form is present\r | |
124 | in a given certificate.\r | |
125 | \r | |
126 | @param[in] Cert The certificate to check.\r | |
127 | \r | |
128 | @param[in] Asn1ToFind The EKU to look for.\r | |
129 | \r | |
130 | @retval EFI_SUCCESS We successfully identified the signing type.\r | |
131 | @retval EFI_INVALID_PARAMETER A parameter was invalid.\r | |
132 | @retval EFI_NOT_FOUND One or more EKU's were not found in the signature.\r | |
133 | \r | |
134 | **/\r | |
135 | EFI_STATUS\r | |
136 | IsEkuInCertificate (\r | |
137 | IN CONST X509 *Cert,\r | |
138 | IN ASN1_OBJECT *Asn1ToFind\r | |
139 | )\r | |
140 | {\r | |
141 | EFI_STATUS Status;\r | |
142 | X509 *ClonedCert;\r | |
143 | X509_EXTENSION *Extension;\r | |
144 | EXTENDED_KEY_USAGE *Eku;\r | |
145 | INT32 ExtensionIndex;\r | |
146 | INTN NumExtensions;\r | |
147 | ASN1_OBJECT *Asn1InCert;\r | |
148 | INTN Index;\r | |
149 | \r | |
150 | Status = EFI_NOT_FOUND;\r | |
151 | ClonedCert = NULL;\r | |
152 | Extension = NULL;\r | |
153 | Eku = NULL;\r | |
154 | ExtensionIndex = -1;\r | |
155 | NumExtensions = 0;\r | |
156 | Asn1InCert = NULL;\r | |
157 | \r | |
158 | if (Cert == NULL || Asn1ToFind == NULL) {\r | |
159 | Status = EFI_INVALID_PARAMETER;\r | |
160 | goto Exit;\r | |
161 | }\r | |
162 | \r | |
163 | //\r | |
164 | // Clone the certificate. This is required because the Extension API's\r | |
165 | // only work once per instance of an X509 object.\r | |
166 | //\r | |
167 | ClonedCert = X509_dup ((X509*)Cert);\r | |
168 | if (ClonedCert == NULL) {\r | |
169 | //\r | |
170 | // Fail to duplicate cert.\r | |
171 | //\r | |
172 | Status = EFI_INVALID_PARAMETER;\r | |
173 | goto Exit;\r | |
174 | }\r | |
175 | \r | |
176 | //\r | |
177 | // Look for the extended key usage.\r | |
178 | //\r | |
179 | ExtensionIndex = X509_get_ext_by_NID (ClonedCert, NID_ext_key_usage, -1);\r | |
180 | \r | |
181 | if (ExtensionIndex < 0) {\r | |
182 | //\r | |
183 | // Fail to find 'NID_ext_key_usage' in Cert.\r | |
184 | //\r | |
185 | goto Exit;\r | |
186 | }\r | |
187 | \r | |
188 | Extension = X509_get_ext (ClonedCert, ExtensionIndex);\r | |
189 | if (Extension == NULL) {\r | |
190 | //\r | |
191 | // Fail to get Extension form cert.\r | |
192 | //\r | |
193 | goto Exit;\r | |
194 | }\r | |
195 | \r | |
196 | Eku = (EXTENDED_KEY_USAGE*)X509V3_EXT_d2i (Extension);\r | |
197 | if (Eku == NULL) {\r | |
198 | //\r | |
199 | // Fail to get Eku from extension.\r | |
200 | //\r | |
201 | goto Exit;\r | |
202 | }\r | |
203 | \r | |
204 | NumExtensions = sk_ASN1_OBJECT_num (Eku);\r | |
205 | \r | |
206 | //\r | |
207 | // Now loop through the extensions, looking for the specified Eku.\r | |
208 | //\r | |
209 | for (Index = 0; Index < NumExtensions; Index++) {\r | |
210 | Asn1InCert = sk_ASN1_OBJECT_value (Eku, (INT32)Index);\r | |
211 | if (Asn1InCert == NULL) {\r | |
212 | //\r | |
213 | // Fail to get ASN object from Eku.\r | |
214 | //\r | |
215 | goto Exit;\r | |
216 | }\r | |
217 | \r | |
218 | if (Asn1InCert->length == Asn1ToFind->length &&\r | |
219 | CompareMem (Asn1InCert->data, Asn1ToFind->data, Asn1InCert->length) == 0) {\r | |
220 | //\r | |
221 | // Found Eku in certificate.\r | |
222 | //\r | |
223 | Status = EFI_SUCCESS;\r | |
224 | goto Exit;\r | |
225 | }\r | |
226 | }\r | |
227 | \r | |
228 | Exit:\r | |
229 | \r | |
230 | //\r | |
231 | // Release Resources\r | |
232 | //\r | |
b3d00df6 | 233 | if (ClonedCert != NULL) {\r |
23c3178c BB |
234 | X509_free (ClonedCert);\r |
235 | }\r | |
236 | \r | |
b3d00df6 | 237 | if (Eku != NULL) {\r |
23c3178c BB |
238 | sk_ASN1_OBJECT_pop_free (Eku, ASN1_OBJECT_free);\r |
239 | }\r | |
240 | \r | |
241 | return Status;\r | |
242 | }\r | |
243 | \r | |
244 | \r | |
245 | /**\r | |
246 | Determines if the specified EKUs are present in a signing certificate.\r | |
247 | \r | |
248 | @param[in] SignerCert The certificate to check.\r | |
249 | @param[in] RequiredEKUs The EKUs to look for.\r | |
250 | @param[in] RequiredEKUsSize The number of EKUs\r | |
251 | @param[in] RequireAllPresent If TRUE, then all the specified EKUs\r | |
252 | must be present in the certificate.\r | |
253 | \r | |
254 | @retval EFI_SUCCESS We successfully identified the signing type.\r | |
255 | @retval EFI_INVALID_PARAMETER A parameter was invalid.\r | |
256 | @retval EFI_NOT_FOUND One or more EKU's were not found in the signature.\r | |
257 | **/\r | |
258 | EFI_STATUS\r | |
259 | CheckEKUs(\r | |
260 | IN CONST X509 *SignerCert,\r | |
261 | IN CONST CHAR8 *RequiredEKUs[],\r | |
262 | IN CONST UINT32 RequiredEKUsSize,\r | |
263 | IN BOOLEAN RequireAllPresent\r | |
264 | )\r | |
265 | {\r | |
266 | EFI_STATUS Status;\r | |
267 | ASN1_OBJECT *Asn1ToFind;\r | |
268 | UINT32 NumEkusFound;\r | |
269 | UINT32 Index;\r | |
270 | \r | |
271 | Status = EFI_SUCCESS;\r | |
272 | Asn1ToFind = NULL;\r | |
273 | NumEkusFound = 0;\r | |
274 | \r | |
275 | if (SignerCert == NULL || RequiredEKUs == NULL || RequiredEKUsSize == 0) {\r | |
276 | Status = EFI_INVALID_PARAMETER;\r | |
277 | goto Exit;\r | |
278 | }\r | |
279 | \r | |
280 | for (Index = 0; Index < RequiredEKUsSize; Index++) {\r | |
281 | //\r | |
282 | // Finding required EKU in cert.\r | |
283 | //\r | |
b3d00df6 | 284 | if (Asn1ToFind != NULL) {\r |
23c3178c BB |
285 | ASN1_OBJECT_free(Asn1ToFind);\r |
286 | Asn1ToFind = NULL;\r | |
287 | }\r | |
288 | \r | |
289 | Asn1ToFind = OBJ_txt2obj (RequiredEKUs[Index], 0);\r | |
b3d00df6 | 290 | if (Asn1ToFind == NULL) {\r |
23c3178c BB |
291 | //\r |
292 | // Fail to convert required EKU to ASN1.\r | |
293 | //\r | |
294 | Status = EFI_INVALID_PARAMETER;\r | |
295 | goto Exit;\r | |
296 | }\r | |
297 | \r | |
298 | Status = IsEkuInCertificate (SignerCert, Asn1ToFind);\r | |
299 | if (Status == EFI_SUCCESS) {\r | |
300 | NumEkusFound++;\r | |
301 | if (!RequireAllPresent) {\r | |
302 | //\r | |
303 | // Found at least one, so we are done.\r | |
304 | //\r | |
305 | goto Exit;\r | |
306 | }\r | |
307 | } else {\r | |
308 | //\r | |
309 | // Fail to find Eku in cert\r | |
310 | break;\r | |
311 | }\r | |
312 | }\r | |
313 | \r | |
314 | Exit:\r | |
315 | \r | |
b3d00df6 | 316 | if (Asn1ToFind != NULL) {\r |
23c3178c BB |
317 | ASN1_OBJECT_free(Asn1ToFind);\r |
318 | }\r | |
319 | \r | |
320 | if (RequireAllPresent &&\r | |
321 | NumEkusFound == RequiredEKUsSize) {\r | |
322 | //\r | |
323 | // Found all required EKUs in certificate.\r | |
324 | //\r | |
325 | Status = EFI_SUCCESS;\r | |
326 | }\r | |
327 | \r | |
328 | return Status;\r | |
329 | }\r | |
330 | \r | |
331 | /**\r | |
332 | This function receives a PKCS#7 formatted signature blob,\r | |
333 | looks for the EKU SEQUENCE blob, and if found then looks\r | |
334 | for all the required EKUs. This function was created so that\r | |
335 | the Surface team can cut down on the number of Certificate\r | |
336 | Authorities (CA's) by checking EKU's on leaf signers for\r | |
337 | a specific product. This prevents one product's certificate\r | |
338 | from signing another product's firmware or unlock blobs.\r | |
339 | \r | |
340 | Note that this function does not validate the certificate chain.\r | |
341 | That needs to be done before using this function.\r | |
342 | \r | |
343 | @param[in] Pkcs7Signature The PKCS#7 signed information content block. An array\r | |
344 | containing the content block with both the signature,\r | |
345 | the signer's certificate, and any necessary intermediate\r | |
346 | certificates.\r | |
347 | @param[in] Pkcs7SignatureSize Number of bytes in Pkcs7Signature.\r | |
348 | @param[in] RequiredEKUs Array of null-terminated strings listing OIDs of\r | |
349 | required EKUs that must be present in the signature.\r | |
350 | @param[in] RequiredEKUsSize Number of elements in the RequiredEKUs string array.\r | |
351 | @param[in] RequireAllPresent If this is TRUE, then all of the specified EKU's\r | |
352 | must be present in the leaf signer. If it is\r | |
353 | FALSE, then we will succeed if we find any\r | |
354 | of the specified EKU's.\r | |
355 | \r | |
356 | @retval EFI_SUCCESS The required EKUs were found in the signature.\r | |
357 | @retval EFI_INVALID_PARAMETER A parameter was invalid.\r | |
358 | @retval EFI_NOT_FOUND One or more EKU's were not found in the signature.\r | |
359 | \r | |
360 | **/\r | |
361 | EFI_STATUS\r | |
362 | EFIAPI\r | |
363 | VerifyEKUsInPkcs7Signature (\r | |
364 | IN CONST UINT8 *Pkcs7Signature,\r | |
365 | IN CONST UINT32 SignatureSize,\r | |
366 | IN CONST CHAR8 *RequiredEKUs[],\r | |
367 | IN CONST UINT32 RequiredEKUsSize,\r | |
368 | IN BOOLEAN RequireAllPresent\r | |
369 | )\r | |
370 | {\r | |
371 | EFI_STATUS Status;\r | |
372 | PKCS7 *Pkcs7;\r | |
373 | STACK_OF(X509) *CertChain;\r | |
374 | INT32 SignatureType;\r | |
375 | INT32 NumberCertsInSignature;\r | |
376 | X509 *SignerCert;\r | |
377 | UINT8 *SignedData;\r | |
378 | UINT8 *Temp;\r | |
379 | UINTN SignedDataSize;\r | |
380 | BOOLEAN IsWrapped;\r | |
381 | BOOLEAN Ok;\r | |
382 | \r | |
383 | Status = EFI_SUCCESS;\r | |
384 | Pkcs7 = NULL;\r | |
385 | CertChain = NULL;\r | |
386 | SignatureType = 0;\r | |
387 | NumberCertsInSignature = 0;\r | |
388 | SignerCert = NULL;\r | |
389 | SignedData = NULL;\r | |
390 | SignedDataSize = 0;\r | |
391 | IsWrapped = FALSE;\r | |
392 | Ok = FALSE;\r | |
393 | \r | |
394 | //\r | |
395 | //Validate the input parameters.\r | |
396 | //\r | |
397 | if (Pkcs7Signature == NULL ||\r | |
398 | SignatureSize == 0 ||\r | |
399 | RequiredEKUs == NULL ||\r | |
400 | RequiredEKUsSize == 0) {\r | |
401 | Status = EFI_INVALID_PARAMETER;\r | |
402 | goto Exit;\r | |
403 | }\r | |
404 | \r | |
405 | if (RequiredEKUsSize == 1) {\r | |
406 | RequireAllPresent = TRUE;\r | |
407 | }\r | |
408 | \r | |
409 | //\r | |
410 | // Wrap the PKCS7 data if needed.\r | |
411 | //\r | |
412 | Ok = WrapPkcs7Data (Pkcs7Signature,\r | |
413 | SignatureSize,\r | |
414 | &IsWrapped,\r | |
415 | &SignedData,\r | |
416 | &SignedDataSize);\r | |
417 | if (!Ok) {\r | |
418 | //\r | |
419 | // Fail to Wrap the PKCS7 data.\r | |
420 | //\r | |
421 | Status = EFI_INVALID_PARAMETER;\r | |
422 | goto Exit;\r | |
423 | }\r | |
424 | \r | |
425 | Temp = SignedData;\r | |
426 | \r | |
427 | //\r | |
428 | // Create the PKCS7 object.\r | |
429 | //\r | |
430 | Pkcs7 = d2i_PKCS7 (NULL, (const unsigned char **)&Temp, (INT32)SignedDataSize);\r | |
431 | if (Pkcs7 == NULL) {\r | |
432 | //\r | |
433 | // Fail to read PKCS7 data.\r | |
434 | //\r | |
435 | Status = EFI_INVALID_PARAMETER;\r | |
436 | goto Exit;\r | |
437 | }\r | |
438 | \r | |
439 | //\r | |
440 | // Get the certificate chain.\r | |
441 | //\r | |
442 | SignatureType = OBJ_obj2nid (Pkcs7->type);\r | |
443 | switch (SignatureType) {\r | |
444 | case NID_pkcs7_signed:\r | |
445 | if (Pkcs7->d.sign != NULL) {\r | |
446 | CertChain = Pkcs7->d.sign->cert;\r | |
447 | }\r | |
448 | break;\r | |
449 | case NID_pkcs7_signedAndEnveloped:\r | |
450 | if (Pkcs7->d.signed_and_enveloped != NULL) {\r | |
451 | CertChain = Pkcs7->d.signed_and_enveloped->cert;\r | |
452 | }\r | |
453 | break;\r | |
454 | default:\r | |
455 | break;\r | |
456 | }\r | |
457 | \r | |
458 | //\r | |
459 | // Ensure we have a certificate stack\r | |
460 | //\r | |
461 | if (CertChain == NULL) {\r | |
462 | //\r | |
463 | // Fail to get the certificate stack from signature.\r | |
464 | //\r | |
465 | Status = EFI_INVALID_PARAMETER;\r | |
466 | goto Exit;\r | |
467 | }\r | |
468 | \r | |
469 | //\r | |
470 | // Find out how many certificates were in the PKCS7 signature.\r | |
471 | //\r | |
472 | NumberCertsInSignature = sk_X509_num (CertChain);\r | |
473 | \r | |
474 | if (NumberCertsInSignature == 0) {\r | |
475 | //\r | |
476 | // Fail to find any certificates in signature.\r | |
477 | //\r | |
478 | Status = EFI_INVALID_PARAMETER;\r | |
479 | goto Exit;\r | |
480 | }\r | |
481 | \r | |
482 | //\r | |
483 | // Get the leaf signer.\r | |
484 | //\r | |
485 | Status = GetSignerCertificate (Pkcs7, &SignerCert);\r | |
486 | if (Status != EFI_SUCCESS || SignerCert == NULL) {\r | |
487 | //\r | |
488 | // Fail to get the end-entity leaf signer certificate.\r | |
489 | //\r | |
490 | Status = EFI_INVALID_PARAMETER;\r | |
491 | goto Exit;\r | |
492 | }\r | |
493 | \r | |
494 | Status = CheckEKUs (SignerCert, RequiredEKUs, RequiredEKUsSize, RequireAllPresent);\r | |
495 | if (Status != EFI_SUCCESS) {\r | |
496 | goto Exit;\r | |
497 | }\r | |
498 | \r | |
499 | Exit:\r | |
500 | \r | |
501 | //\r | |
502 | // Release Resources\r | |
503 | //\r | |
504 | // If the signature was not wrapped, then the call to WrapData() will allocate\r | |
505 | // the data and add a header to it\r | |
506 | //\r | |
507 | if (!IsWrapped && SignedData) {\r | |
508 | free (SignedData);\r | |
509 | }\r | |
510 | \r | |
b3d00df6 | 511 | if (SignerCert != NULL) {\r |
23c3178c BB |
512 | X509_free (SignerCert);\r |
513 | }\r | |
514 | \r | |
b3d00df6 | 515 | if (Pkcs7 != NULL) {\r |
23c3178c BB |
516 | PKCS7_free (Pkcs7);\r |
517 | }\r | |
518 | \r | |
519 | return Status;\r | |
520 | }\r | |
521 | \r |