Fix uninitialized okeybuf

core/src/fpdfapi/fpdf_parser/fpdf_parser_encrypt.cpp

Index: core/src/fpdfapi/fpdf_parser/fpdf_parser_encrypt.cpp
diff --git a/core/src/fpdfapi/fpdf_parser/fpdf_parser_encrypt.cpp b/core/src/fpdfapi/fpdf_parser/fpdf_parser_encrypt.cpp
index e09bbbbb2e9a3ade9566d74db700d43f96447536..4713bacfce35babd6b22c440baa5f9657da88f7e 100644
--- a/core/src/fpdfapi/fpdf_parser/fpdf_parser_encrypt.cpp
+++ b/core/src/fpdfapi/fpdf_parser/fpdf_parser_encrypt.cpp
@@ -460,6 +460,7 @@ CFX_ByteString CPDF_StandardSecurityHandler::GetUserPassword(FX_LPCBYTE owner_pa
         okeylen = 32;
     }
     FX_BYTE okeybuf[64];
+    FXSYS_memset32(okeybuf, 0, sizeof(okeybuf));
     FXSYS_memcpy32(okeybuf, (FX_LPCSTR)okey, okeylen);
     if (m_Revision == 2) {
         CRYPT_ArcFourCryptBlock(okeybuf, okeylen, enckey, key_len);