[PATCH] CryptoPkg/BaseCryptLib: Add NULL pointer checks in DH and P7Verify

[Long Qin <qin.long@intel.com>]

Add more NULL pointer checks before using them in DhGenerateKey and
Pkcs7GetCertificatesList functions to eliminate possible dereferenced
pointer issue.

Cc: Ting Ye <ting.ye@intel.com>
Cc: Hao Wu <hao.a.wu@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Qin Long <qin.long@intel.com>
---
 CryptoPkg/Library/BaseCryptLib/Pk/CryptDh.c          |  4 +++-
 CryptoPkg/Library/BaseCryptLib/Pk/CryptPkcs7Verify.c | 10 +++++++---
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/CryptoPkg/Library/BaseCryptLib/Pk/CryptDh.c b/CryptoPkg/Library/BaseCryptLib/Pk/CryptDh.c
index f44684f907..391efd5c14 100644
--- a/CryptoPkg/Library/BaseCryptLib/Pk/CryptDh.c
+++ b/CryptoPkg/Library/BaseCryptLib/Pk/CryptDh.c
@@ -232,7 +232,9 @@ DhGenerateKey (
       return FALSE;
     }
 
-    BN_bn2bin (DhPubKey, PublicKey);
+    if (PublicKey != NULL) {
+      BN_bn2bin (DhPubKey, PublicKey);
+    }
     *PublicKeySize = Size;
   }
 
diff --git a/CryptoPkg/Library/BaseCryptLib/Pk/CryptPkcs7Verify.c b/CryptoPkg/Library/BaseCryptLib/Pk/CryptPkcs7Verify.c
index 45d5df5e11..d564591cb7 100644
--- a/CryptoPkg/Library/BaseCryptLib/Pk/CryptPkcs7Verify.c
+++ b/CryptoPkg/Library/BaseCryptLib/Pk/CryptPkcs7Verify.c
@@ -558,7 +558,9 @@ Pkcs7GetCertificatesList (
     }
   }
   CtxUntrusted = X509_STORE_CTX_get0_untrusted (CertCtx);
-  (VOID)sk_X509_delete_ptr (CtxUntrusted, Signer);
+  if (CtxUntrusted != NULL) {
+    (VOID)sk_X509_delete_ptr (CtxUntrusted, Signer);
+  }
 
   //
   // Build certificates stack chained from Signer's certificate.
@@ -711,8 +713,10 @@ _Error:
   }
   sk_X509_free (Signers);
 
-  X509_STORE_CTX_cleanup (CertCtx);
-  X509_STORE_CTX_free (CertCtx);
+  if (CertCtx != NULL) {
+    X509_STORE_CTX_cleanup (CertCtx);
+    X509_STORE_CTX_free (CertCtx);
+  }
 
   if (SingleCert != NULL) {
     free (SingleCert);
-- 
2.12.2.windows.2