Add two new interfaces Pkcs7GetSigners and Pkcs7FreeSigners to BaseCryptLib.

Signed-off by: tye1
Reviewed-by: geekboy15a
Reviewed-by: sfu5
Reviewed-by: gdong1

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@13158 6f19259b-4bc3-4df7-8a09-765794883524

CryptoPkg/Library/BaseCryptLib/Pk/CryptX509.c

@@ -224,6 +224,91 @@ X509StackFree (
   sk_X509_pop_free ((STACK_OF(X509) *) X509Stack, X509_free);
 }
 
+/**
+  Pop single certificate from STACK_OF(X509).
+
+  If X509Stack, Cert, or CertSize is NULL, then return FALSE.
+
+  @param[in]  X509Stack       Pointer to a X509 stack object.
+  @param[out] Cert            Pointer to a X509 certificate.
+  @param[out] CertSize        Length of output X509 certificate in bytes.
+                                 
+  @retval     TRUE            The X509 stack pop succeeded.
+  @retval     FALSE           The pop operation failed.
+
+**/
+BOOLEAN
+X509PopCertificate (
+  IN  VOID  *X509Stack,
+  OUT UINT8 **Cert,
+  OUT UINTN *CertSize
+  )
+{
+  BIO             *CertBio;
+  X509            *X509Cert;
+  STACK_OF(X509)  *CertStack;
+  BOOLEAN         Status;
+  int             Result;
+  int             Length;
+  VOID            *Buffer;
+
+  Status = FALSE;
+
+  if ((X509Stack == NULL) || (Cert == NULL) || (CertSize == NULL)) {
+    return Status;
+  }
+
+  CertStack = (STACK_OF(X509) *) X509Stack;
+
+  X509Cert = sk_X509_pop (CertStack);
+
+  if (X509Cert == NULL) {
+    return Status;
+  }
+
+  Buffer = NULL;
+
+  CertBio = BIO_new (BIO_s_mem ());
+  if (CertBio == NULL) {
+    return Status;
+  }
+
+  Result = i2d_X509_bio (CertBio, X509Cert);
+  if (Result == 0) {
+    goto _Exit;
+  }
+
+  Length = ((BUF_MEM *) CertBio->ptr)->length;
+  if (Length <= 0) {
+    goto _Exit;
+  }
+
+  Buffer = malloc (Length);
+  if (Buffer == NULL) {
+    goto _Exit;
+  }
+
+  Result = BIO_read (CertBio, Buffer, Length);
+  if (Result != Length) {
+    goto _Exit;
+  }
+
+  *Cert     = Buffer;
+  *CertSize = Length;
+
+  Status = TRUE;
+
+_Exit:
+
+  BIO_free (CertBio);
+
+  if (!Status && (Buffer != NULL)) {
+    free (Buffer);
+  }
+
+  return Status;
+}
+
 /**
   Retrieve the subject bytes from one X.509 certificate.