CryptoPkg/Library/BaseCryptLib/Pk/CryptPkcs7VerifyEku.c

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