SecurityPkg:AuthVariableLib:Implement ECR1707 for Private Auth Variable

ECR1707 for UEFI2.7 clarified certificate management rule for private time-based
AuthVariable.Trusted cert rule changed from whole signer's certificate stack to
top-level issuer cert tbscertificate + SignerCert CN for better management compatibility.
Hash is used to reduce storage overhead.

Cc: Long Qin <qin.long@intel.com>
Cc: Chen Chen <chen.a.chen@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Chao Zhang <chao.b.zhang@intel.com>'
Reviewed-by: Long Qin <qin.long@intel.com>
Reviewed-by: Chen Chen <chen.a.chen@intel.com>

1 files changed, 171 insertions, 37 deletions

diff --git a/SecurityPkg/Library/AuthVariableLib/AuthService.c b/SecurityPkg/Library/AuthVariableLib/AuthService.c
index a37ec0bd0f..7188ff6008 100644
--- a/SecurityPkg/Library/AuthVariableLib/AuthService.c
+++ b/SecurityPkg/Library/AuthVariableLib/AuthService.c
@@ -1530,6 +1530,85 @@ AuthServiceInternalCompareTimeStamp (
 }

 

 /**

+  Calculate SHA256 digest of SignerCert CommonName + ToplevelCert tbsCertificate

+  SignerCert and ToplevelCert are inside the signer certificate chain.

+

+  @param[in]  SignerCert          A pointer to SignerCert data.

+  @param[in]  SignerCertSize      Length of SignerCert data.

+  @param[in]  TopLevelCert        A pointer to TopLevelCert data.

+  @param[in]  TopLevelCertSize    Length of TopLevelCert data.

+  @param[out] Sha256Digest       Sha256 digest calculated.

+

+  @return EFI_ABORTED          Digest process failed.

+  @return EFI_SUCCESS          SHA256 Digest is succesfully calculated.

+

+**/

+EFI_STATUS

+CalculatePrivAuthVarSignChainSHA256Digest(

+  IN     UINT8            *SignerCert,

+  IN     UINTN            SignerCertSize,

+  IN     UINT8            *TopLevelCert,

+  IN     UINTN            TopLevelCertSize,

+  OUT    UINT8            *Sha256Digest

+  )

+{

+  UINT8                   *TbsCert;

+  UINTN                   TbsCertSize;

+  UINT8                   CertCommonName[128];

+  UINTN                   CertCommonNameSize;

+  BOOLEAN                 CryptoStatus;

+  EFI_STATUS              Status;

+

+  CertCommonNameSize = sizeof(CertCommonName);

+

+  //

+  // Get SignerCert CommonName

+  //

+  Status = X509GetCommonName(SignerCert, SignerCertSize, CertCommonName, &CertCommonNameSize);

+  if (EFI_ERROR(Status)) {

+    DEBUG((DEBUG_INFO, "%a Get SignerCert CommonName failed with status %x\n", __FUNCTION__, Status));

+    return EFI_ABORTED;

+  }

+

+  //

+  // Get TopLevelCert tbsCertificate

+  //

+  if (!X509GetTBSCert(TopLevelCert, TopLevelCertSize, &TbsCert, &TbsCertSize)) {

+    DEBUG((DEBUG_INFO, "%a Get Top-level Cert tbsCertificate failed!\n", __FUNCTION__));

+    return EFI_ABORTED;

+  }

+

+  //

+  // Digest SignerCert CN + TopLevelCert tbsCertificate

+  //

+  ZeroMem (Sha256Digest, SHA256_DIGEST_SIZE);

+  CryptoStatus = Sha256Init (mHashCtx);

+  if (!CryptoStatus) {

+    return EFI_ABORTED;

+  }

+

+  //

+  // '\0' is forced in CertCommonName. No overflow issue

+  //

+  CryptoStatus = Sha256Update (mHashCtx, CertCommonName, AsciiStrLen((CHAR8 *)CertCommonName));

+  if (!CryptoStatus) {

+    return EFI_ABORTED;

+  }

+

+  CryptoStatus = Sha256Update (mHashCtx, TbsCert, TbsCertSize);

+  if (!CryptoStatus) {

+    return EFI_ABORTED;

+  }

+

+  CryptoStatus  = Sha256Final (mHashCtx, Sha256Digest);

+  if (!CryptoStatus) {

+    return EFI_ABORTED;

+  }

+

+  return EFI_SUCCESS;

+}

+

+/**

   Find matching signer's certificates for common authenticated variable

   by corresponding VariableName and VendorGuid from "certdb" or "certdbv".

 

@@ -1872,13 +1951,16 @@ DeleteCertsFromDb (
 /**

   Insert signer's certificates for common authenticated variable with VariableName

   and VendorGuid in AUTH_CERT_DB_DATA to "certdb" or "certdbv" according to

-  time based authenticated variable attributes.

+  time based authenticated variable attributes. CertData is the SHA256 digest of

+  SignerCert CommonName + TopLevelCert tbsCertificate.

 

-  @param[in]  VariableName   Name of authenticated Variable.

-  @param[in]  VendorGuid     Vendor GUID of authenticated Variable.

-  @param[in]  Attributes     Attributes of authenticated variable.

-  @param[in]  CertData       Pointer to signer's certificates.

-  @param[in]  CertDataSize   Length of CertData in bytes.

+  @param[in]  VariableName      Name of authenticated Variable.

+  @param[in]  VendorGuid        Vendor GUID of authenticated Variable.

+  @param[in]  Attributes        Attributes of authenticated variable.

+  @param[in]  SignerCert        Signer certificate data.

+  @param[in]  SignerCertSize    Length of signer certificate.

+  @param[in]  TopLevelCert      Top-level certificate data.

+  @param[in]  TopLevelCertSize  Length of top-level certificate.

 

   @retval  EFI_INVALID_PARAMETER Any input parameter is invalid.

   @retval  EFI_ACCESS_DENIED     An AUTH_CERT_DB_DATA entry with same VariableName

@@ -1892,8 +1974,10 @@ InsertCertsToDb (
   IN     CHAR16           *VariableName,

   IN     EFI_GUID         *VendorGuid,

   IN     UINT32           Attributes,

-  IN     UINT8            *CertData,

-  IN     UINTN            CertDataSize

+  IN     UINT8            *SignerCert,

+  IN     UINTN            SignerCertSize,

+  IN     UINT8            *TopLevelCert,

+  IN     UINTN            TopLevelCertSize

   )

 {

   EFI_STATUS              Status;

@@ -1904,10 +1988,12 @@ InsertCertsToDb (
   UINT32                  NewCertDbSize;

   UINT32                  CertNodeSize;

   UINT32                  NameSize;

+  UINT32                  CertDataSize;

   AUTH_CERT_DB_DATA       *Ptr;

   CHAR16                  *DbName;

+  UINT8                   Sha256Digest[SHA256_DIGEST_SIZE];

 

-  if ((VariableName == NULL) || (VendorGuid == NULL) || (CertData == NULL)) {

+  if ((VariableName == NULL) || (VendorGuid == NULL) || (SignerCert == NULL) ||(TopLevelCert == NULL)) {

     return EFI_INVALID_PARAMETER;

   }

 

@@ -1967,11 +2053,24 @@ InsertCertsToDb (
   // Construct new data content of variable "certdb" or "certdbv".

   //

   NameSize      = (UINT32) StrLen (VariableName);

+  CertDataSize  = sizeof(Sha256Digest);

   CertNodeSize  = sizeof (AUTH_CERT_DB_DATA) + (UINT32) CertDataSize + NameSize * sizeof (CHAR16);

   NewCertDbSize = (UINT32) DataSize + CertNodeSize;

   if (NewCertDbSize > mMaxCertDbSize) {

     return EFI_OUT_OF_RESOURCES;

   }

+

+  Status = CalculatePrivAuthVarSignChainSHA256Digest(

+             SignerCert,

+             SignerCertSize,

+             TopLevelCert,

+             TopLevelCertSize,

+             Sha256Digest

+             );

+  if (EFI_ERROR (Status)) {

+    return Status;

+  }

+

   NewCertDb     = (UINT8*) mCertDbStore;

 

   //

@@ -1999,7 +2098,7 @@ InsertCertsToDb (
 

   CopyMem (

     (UINT8 *) Ptr +  sizeof (AUTH_CERT_DB_DATA) + NameSize * sizeof (CHAR16),

-    CertData,

+    Sha256Digest,

     CertDataSize

     );

 

@@ -2181,19 +2280,27 @@ VerifyTimeBasedPayload (
   UINTN                            NewDataSize;

   UINT8                            *Buffer;

   UINTN                            Length;

-  UINT8                            *RootCert;

-  UINTN                            RootCertSize;

+  UINT8                            *TopLevelCert;

+  UINTN                            TopLevelCertSize;

+  UINT8                            *TrustedCert;

+  UINTN                            TrustedCertSize;

   UINT8                            *SignerCerts;

   UINTN                            CertStackSize;

   UINT8                            *CertsInCertDb;

   UINT32                           CertsSizeinDb;

+  UINT8                            Sha256Digest[SHA256_DIGEST_SIZE];

 

+  //

+  // 1. TopLevelCert is the top-level issuer certificate in signature Signer Cert Chain

+  // 2. TrustedCert is the certificate which firmware trusts. It could be saved in protected

+  //     storage or PK payload on PK init

+  //

   VerifyStatus           = FALSE;

   CertData               = NULL;

   NewData                = NULL;

   Attr                   = Attributes;

   SignerCerts            = NULL;

-  RootCert               = NULL;

+  TopLevelCert           = NULL;

   CertsInCertDb          = NULL;

 

   //

@@ -2325,8 +2432,8 @@ VerifyTimeBasedPayload (
                      SigDataSize,

                      &SignerCerts,

                      &CertStackSize,

-                     &RootCert,

-                     &RootCertSize

+                     &TopLevelCert,

+                     &TopLevelCertSize

                      );

     if (!VerifyStatus) {

       goto Exit;

@@ -2348,8 +2455,8 @@ VerifyTimeBasedPayload (
     }

     CertList = (EFI_SIGNATURE_LIST *) Data;

     Cert     = (EFI_SIGNATURE_DATA *) ((UINT8 *) CertList + sizeof (EFI_SIGNATURE_LIST) + CertList->SignatureHeaderSize);

-    if ((RootCertSize != (CertList->SignatureSize - (sizeof (EFI_SIGNATURE_DATA) - 1))) ||

-        (CompareMem (Cert->SignatureData, RootCert, RootCertSize) != 0)) {

+    if ((TopLevelCertSize != (CertList->SignatureSize - (sizeof (EFI_SIGNATURE_DATA) - 1))) ||

+        (CompareMem (Cert->SignatureData, TopLevelCert, TopLevelCertSize) != 0)) {

       VerifyStatus = FALSE;

       goto Exit;

     }

@@ -2360,8 +2467,8 @@ VerifyTimeBasedPayload (
     VerifyStatus = Pkcs7Verify (

                      SigData,

                      SigDataSize,

-                     RootCert,

-                     RootCertSize,

+                     TopLevelCert,

+                     TopLevelCertSize,

                      NewData,

                      NewDataSize

                      );

@@ -2394,8 +2501,8 @@ VerifyTimeBasedPayload (
           //

           // Iterate each Signature Data Node within this CertList for a verify

           //

-          RootCert      = Cert->SignatureData;

-          RootCertSize  = CertList->SignatureSize - (sizeof (EFI_SIGNATURE_DATA) - 1);

+          TrustedCert      = Cert->SignatureData;

+          TrustedCertSize  = CertList->SignatureSize - (sizeof (EFI_SIGNATURE_DATA) - 1);

 

           //

           // Verify Pkcs7 SignedData via Pkcs7Verify library.

@@ -2403,8 +2510,8 @@ VerifyTimeBasedPayload (
           VerifyStatus = Pkcs7Verify (

                            SigData,

                            SigDataSize,

-                           RootCert,

-                           RootCertSize,

+                           TrustedCert,

+                           TrustedCertSize,

                            NewData,

                            NewDataSize

                            );

@@ -2428,8 +2535,8 @@ VerifyTimeBasedPayload (
                      SigDataSize,

                      &SignerCerts,

                      &CertStackSize,

-                     &RootCert,

-                     &RootCertSize

+                     &TopLevelCert,

+                     &TopLevelCertSize

                      );

     if (!VerifyStatus) {

       goto Exit;

@@ -2448,17 +2555,36 @@ VerifyTimeBasedPayload (
         goto Exit;

       }

 

-      if ((CertStackSize != CertsSizeinDb) ||

-          (CompareMem (SignerCerts, CertsInCertDb, CertsSizeinDb) != 0)) {

-        goto Exit;

+      if (CertsSizeinDb == SHA256_DIGEST_SIZE) {

+        //

+        // Check hash of signer cert CommonName + Top-level issuer tbsCertificate against data in CertDb

+        //

+        Status = CalculatePrivAuthVarSignChainSHA256Digest(

+                   SignerCerts + sizeof(UINT8) + sizeof(UINT32),

+                   ReadUnaligned32 ((UINT32 *)(SignerCerts + sizeof(UINT8))),

+                   TopLevelCert,

+                   TopLevelCertSize,

+                   Sha256Digest

+                   );

+        if (EFI_ERROR(Status) || CompareMem (Sha256Digest, CertsInCertDb, CertsSizeinDb) != 0){

+          goto Exit;

+        }

+      } else {

+         //

+         // Keep backward compatible with previous solution which saves whole signer certs stack in CertDb

+         //

+         if ((CertStackSize != CertsSizeinDb) ||

+             (CompareMem (SignerCerts, CertsInCertDb, CertsSizeinDb) != 0)) {

+              goto Exit;

+         }

       }

     }

 

     VerifyStatus = Pkcs7Verify (

                      SigData,

                      SigDataSize,

-                     RootCert,

-                     RootCertSize,

+                     TopLevelCert,

+                     TopLevelCertSize,

                      NewData,

                      NewDataSize

                      );

@@ -2468,9 +2594,17 @@ VerifyTimeBasedPayload (
 

     if ((OrgTimeStamp == NULL) && (PayloadSize != 0)) {

       //

-      // Insert signer's certificates when adding a new common authenticated variable.

+      // When adding a new common authenticated variable, always save Hash of cn of signer cert + tbsCertificate of Top-level issuer

       //

-      Status = InsertCertsToDb (VariableName, VendorGuid, Attributes, SignerCerts, CertStackSize);

+      Status = InsertCertsToDb (

+                 VariableName,

+                 VendorGuid,

+                 Attributes,

+                 SignerCerts + sizeof(UINT8) + sizeof(UINT32),

+                 ReadUnaligned32 ((UINT32 *)(SignerCerts + sizeof(UINT8))),

+                 TopLevelCert,

+                 TopLevelCertSize

+                 );

       if (EFI_ERROR (Status)) {

         VerifyStatus = FALSE;

         goto Exit;

@@ -2479,16 +2613,16 @@ VerifyTimeBasedPayload (
   } else if (AuthVarType == AuthVarTypePayload) {

     CertList = (EFI_SIGNATURE_LIST *) PayloadPtr;

     Cert     = (EFI_SIGNATURE_DATA *) ((UINT8 *) CertList + sizeof (EFI_SIGNATURE_LIST) + CertList->SignatureHeaderSize);

-    RootCert      = Cert->SignatureData;

-    RootCertSize  = CertList->SignatureSize - (sizeof (EFI_SIGNATURE_DATA) - 1);

+    TrustedCert     = Cert->SignatureData;

+    TrustedCertSize = CertList->SignatureSize - (sizeof (EFI_SIGNATURE_DATA) - 1);

     //

     // Verify Pkcs7 SignedData via Pkcs7Verify library.

     //

     VerifyStatus = Pkcs7Verify (

                      SigData,

                      SigDataSize,

-                     RootCert,

-                     RootCertSize,

+                     TrustedCert,

+                     TrustedCertSize,

                      NewData,

                      NewDataSize

                      );

@@ -2499,7 +2633,7 @@ VerifyTimeBasedPayload (
 Exit:

 

   if (AuthVarType == AuthVarTypePk || AuthVarType == AuthVarTypePriv) {

-    Pkcs7FreeSigners (RootCert);

+    Pkcs7FreeSigners (TopLevelCert);

     Pkcs7FreeSigners (SignerCerts);

   }