Use more size_t in CPDF_CryptoHandler.

The key length should not be negative.

Change-Id: Ifbc9742d149361de003fc9a509377af0ca0a0715
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/63210
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>

core/fpdfapi/parser/cpdf_crypto_handler.cpp

diff --git a/core/fpdfapi/parser/cpdf_crypto_handler.cpp b/core/fpdfapi/parser/cpdf_crypto_handler.cpp
index 60c8a65..3b3e71c 100644
--- a/core/fpdfapi/parser/cpdf_crypto_handler.cpp
+++ b/core/fpdfapi/parser/cpdf_crypto_handler.cpp
@@ -63,7 +63,7 @@
     }
     CRYPT_MD5Generate(
         key1, m_Cipher == FXCIPHER_AES ? m_KeyLen + 9 : m_KeyLen + 5, realkey);
-    realkeylen = std::min<size_t>(m_KeyLen + 5, sizeof(realkey));
+    realkeylen = std::min(m_KeyLen + 5, sizeof(realkey));
   }
   if (m_Cipher == FXCIPHER_AES) {
     CRYPT_AESSetKey(m_pAESContext.get(),
@@ -130,16 +130,14 @@
   uint8_t key1[48];
   PopulateKey(objnum, gennum, key1);
 
-  if (m_Cipher == FXCIPHER_AES) {
+  if (m_Cipher == FXCIPHER_AES)
     memcpy(key1 + m_KeyLen + 5, "sAlT", 4);
-  }
+
   uint8_t realkey[16];
   CRYPT_MD5Generate(
       key1, m_Cipher == FXCIPHER_AES ? m_KeyLen + 9 : m_KeyLen + 5, realkey);
-  int realkeylen = m_KeyLen + 5;
-  if (realkeylen > 16) {
-    realkeylen = 16;
-  }
+  size_t realkeylen = std::min(m_KeyLen + 5, sizeof(realkey));
+
   if (m_Cipher == FXCIPHER_AES) {
     AESCryptContext* pContext = FX_Alloc(AESCryptContext, 1);
     pContext->m_bIV = true;
@@ -382,8 +380,8 @@
 
 CPDF_CryptoHandler::CPDF_CryptoHandler(int cipher,
                                        const uint8_t* key,
-                                       int keylen)
-    : m_KeyLen(std::min(keylen, 32)), m_Cipher(cipher) {
+                                       size_t keylen)
+    : m_KeyLen(std::min<size_t>(keylen, 32)), m_Cipher(cipher) {
   ASSERT(cipher != FXCIPHER_AES || keylen == 16 || keylen == 24 ||
          keylen == 32);
   ASSERT(cipher != FXCIPHER_AES2 || keylen == 32);
@@ -396,7 +394,7 @@
     m_pAESContext.reset(FX_Alloc(CRYPT_aes_context, 1));
 }
 
-CPDF_CryptoHandler::~CPDF_CryptoHandler() {}
+CPDF_CryptoHandler::~CPDF_CryptoHandler() = default;
 
 void CPDF_CryptoHandler::PopulateKey(uint32_t objnum,
                                      uint32_t gennum,

core/fpdfapi/parser/cpdf_crypto_handler.h

diff --git a/core/fpdfapi/parser/cpdf_crypto_handler.h b/core/fpdfapi/parser/cpdf_crypto_handler.h
index 74fba4d..edfba97 100644
--- a/core/fpdfapi/parser/cpdf_crypto_handler.h
+++ b/core/fpdfapi/parser/cpdf_crypto_handler.h
@@ -22,7 +22,7 @@
 
 class CPDF_CryptoHandler {
  public:
-  CPDF_CryptoHandler(int cipher, const uint8_t* key, int keylen);
+  CPDF_CryptoHandler(int cipher, const uint8_t* key, size_t keylen);
   ~CPDF_CryptoHandler();
 
   static bool IsSignatureDictionary(const CPDF_Dictionary* dictionary);
@@ -60,8 +60,8 @@
                    bool bEncrypt);
   bool CryptFinish(void* context, CFX_BinaryBuf& dest_buf, bool bEncrypt);
 
-  int m_KeyLen;
-  int m_Cipher;
+  const size_t m_KeyLen;
+  const int m_Cipher;
   std::unique_ptr<CRYPT_aes_context, FxFreeDeleter> m_pAESContext;
   uint8_t m_EncryptKey[32];
 };