Unify the error checking of crypto::Encryptor and add WARN_UNUSED_RESULT to prevent misuse.

crypto/encryptor_openssl.cc

Index: crypto/encryptor_openssl.cc
diff --git a/crypto/encryptor_openssl.cc b/crypto/encryptor_openssl.cc
index 65131818243edbf48733b84015e5c36d36cc2a35..5755a6386cef0018ee33b53fae6a6593871f5074 100644
--- a/crypto/encryptor_openssl.cc
+++ b/crypto/encryptor_openssl.cc
@@ -55,8 +55,8 @@ Encryptor::~Encryptor() {
 bool Encryptor::Init(SymmetricKey* key,
                      Mode mode,
                      const base::StringPiece& iv) {
-  DCHECK(key);
-  DCHECK_EQ(CBC, mode);
+  if (!key || mode != CBC)
+    return false;
 
   EnsureOpenSSLInit();
   if (iv.size() != AES_BLOCK_SIZE)
@@ -73,39 +73,49 @@ bool Encryptor::Init(SymmetricKey* key,
 
 bool Encryptor::Encrypt(const base::StringPiece& plaintext,
                         std::string* ciphertext) {
+  ciphertext->clear();
+  if (plaintext.empty() && mode_ != CBC)
+    return false;
   return Crypt(true, plaintext, ciphertext);
 }
 
 bool Encryptor::Decrypt(const base::StringPiece& ciphertext,
                         std::string* plaintext) {
+  plaintext->clear();
+  if (ciphertext.empty())
+    return false;
   return Crypt(false, ciphertext, plaintext);
 }
 
 bool Encryptor::Crypt(bool do_encrypt,
                       const base::StringPiece& input,
                       std::string* output) {
-  DCHECK(key_);  // Must call Init() before En/De-crypt.
-  // Work on the result in a local variable, and then only transfer it to
-  // |output| on success to ensure no partial data is returned.
-  std::string result;
-  output->swap(result);
+  if (!key_)
+    return false;  // Must call Init() first.
 
   const EVP_CIPHER* cipher = GetCipherForKey(key_);
   DCHECK(cipher);  // Already handled in Init();
 
   const std::string& key = key_->key();
-  DCHECK_EQ(EVP_CIPHER_iv_length(cipher), static_cast<int>(iv_.length()));
-  DCHECK_EQ(EVP_CIPHER_key_length(cipher), static_cast<int>(key.length()));
+  if (EVP_CIPHER_iv_length(cipher) != static_cast<int>(iv_.length()) ||
+      EVP_CIPHER_key_length(cipher) != static_cast<int>(key.length())) {
+    return false;
+  }
 
   ScopedCipherCTX ctx;
   if (!EVP_CipherInit_ex(ctx.get(), cipher, NULL,
                          reinterpret_cast<const uint8*>(key.data()),
                          reinterpret_cast<const uint8*>(iv_.data()),
-                         do_encrypt))
+                         do_encrypt)) {
     return false;
+  }
 
+  std::string result;
   // When encrypting, add another block size of space to allow for any padding.
   const size_t output_size = input.size() + (do_encrypt ? iv_.size() : 0);
+  if (output_size == 0 || output_size + 1 < input.size())
+    return false;
+
   uint8* out_ptr = reinterpret_cast<uint8*>(WriteInto(&result,
                                                       output_size + 1));
   int out_len;
@@ -121,9 +131,10 @@ bool Encryptor::Crypt(bool do_encrypt,
     return false;
 
   out_len += tail_len;
-  DCHECK_LE(out_len, static_cast<int>(output_size));
-  result.resize(out_len);
+  if (static_cast<int>(output_size) < out_len)
+    return false;

[wtc, 2011/11/15 02:33:58]

If we get here, we have overrun the buffer in 'result'.
So this check should really be an assertion.

 
+  result.resize(out_len);
   output->swap(result);
   return true;
 }