check length of garlic message

Garlic.cpp

@@ -365,23 +365,34 @@ namespace garlic
 	{
 		uint8_t * buf = msg->GetPayload ();
 		uint32_t length = bufbe32toh (buf);
+		if (length > msg->GetLength ())
+		{
+			LogPrint (eLogError, "Garlic message length ", length, " exceeds I2NP message length ", msg->GetLength ());
+			DeleteI2NPMessage (msg);
+			return;
+		}	
 		buf += 4; // length
 		auto it = m_Tags.find (SessionTag(buf));
 		if (it != m_Tags.end ())
 		{
 			// tag found. Use AES
-			uint8_t iv[32]; // IV is first 16 bytes
-			CryptoPP::SHA256().CalculateDigest(iv, buf, 32);
-			it->second->SetIV (iv);
-			it->second->Decrypt (buf + 32, length - 32, buf + 32);
-			HandleAESBlock (buf + 32, length - 32, it->second, msg->from);
-			m_Tags.erase (it); // tag might be used only once
+			if (length >= 32)
+			{	
+				uint8_t iv[32]; // IV is first 16 bytes
+				CryptoPP::SHA256().CalculateDigest(iv, buf, 32);
+				it->second->SetIV (iv);
+				it->second->Decrypt (buf + 32, length - 32, buf + 32);
+				HandleAESBlock (buf + 32, length - 32, it->second, msg->from);
+			}	
+			else
+				LogPrint (eLogError, "Garlic message length ", length, " is less than 32 bytes");
+			m_Tags.erase (it); // tag might be used only once	
 		}
 		else
 		{
 			// tag not found. Use ElGamal
 			ElGamalBlock elGamal;
-			if (i2p::crypto::ElGamalDecrypt (GetEncryptionPrivateKey (), buf, (uint8_t *)&elGamal, true))
+			if (length >= 514 && i2p::crypto::ElGamalDecrypt (GetEncryptionPrivateKey (), buf, (uint8_t *)&elGamal, true))
 			{	
 				auto decryption = std::make_shared<i2p::crypto::CBCDecryption>();
 				decryption->SetKey (elGamal.sessionKey);
@@ -392,7 +403,7 @@ namespace garlic
 				HandleAESBlock (buf + 514, length - 514, decryption, msg->from);
 			}	
 			else
-				LogPrint ("Failed to decrypt garlic");
+				LogPrint (eLogError, "Failed to decrypt garlic");
 		}
 		DeleteI2NPMessage (msg);