From a59b85192f61c4002cf2076e3dfec39e1b588830 Mon Sep 17 00:00:00 2001
From: moneroexamples <moneroexamples@tuta.io>
Date: Thu, 17 Nov 2016 16:01:41 +0800
Subject: [PATCH] decryption of key image file added using private view key

---
 src/page.h    | 29 ++++++++++++++++++++++-------
 src/tools.cpp | 45 +++++++++++++++++++++++++++++++++++++++++++++
 src/tools.h   |  7 +++++++
 3 files changed, 74 insertions(+), 7 deletions(-)

diff --git a/src/page.h b/src/page.h
index aeaf856..d2fe163 100644
--- a/src/page.h
+++ b/src/page.h
@@ -2020,18 +2020,33 @@ namespace xmreg {
 
             const size_t magiclen = strlen(KEY_IMAGE_EXPORT_FILE_MAGIC);
 
-//            if (!strncmp(decoded_raw_data.c_str(), KEY_IMAGE_EXPORT_FILE_MAGIC, magiclen) == 0)
-//            {
-//                cout << "This does not seem to be key image export data" << endl;
-//                return string {"This does not seem to be key image export data"};
-//            }
+            if (!strncmp(decoded_raw_data.c_str(), KEY_IMAGE_EXPORT_FILE_MAGIC, magiclen) == 0)
+            {
+                cout << "This does not seem to be key image export data" << endl;
+                return string {"This does not seem to be key image export data"};
+            }
+
+            // decrypt key images data using private view key
+            // dont use authentication (i.e., false), as we are
+            // not interested if this key image data is properly signed
+            decoded_raw_data = xmreg::decrypt(
+                    std::string(decoded_raw_data, magiclen),
+                    prv_view_key, false);
 
             // header is public spend and keys
             const size_t header_lenght = 2 * sizeof(crypto::public_key);
             const size_t key_img_size  = sizeof(crypto::key_image);
             const size_t record_lenght = key_img_size + sizeof(crypto::signature);
+            const size_t chacha_length = sizeof(crypto::chacha8_key);
+
+
+            cout << header_lenght << endl;
+            cout << key_img_size << endl;
+            cout << record_lenght << endl;
+            cout << decoded_raw_data.size() - header_lenght << endl;
+            cout << (decoded_raw_data.size() - header_lenght) % record_lenght << endl;
 
-            if ((decoded_raw_data.size() - header_lenght) % record_lenght)
+            if (decoded_raw_data.size() < header_lenght)
             {
                 cerr << "Bad data size from submitted key images raw data" << endl;
                 return string {"Bad data size from submitted key images raw data"};
@@ -2040,7 +2055,7 @@ namespace xmreg {
             // get xmr address stored in this key image file
              const account_public_address* xmr_address =
                     reinterpret_cast<const account_public_address*>(
-                            decoded_raw_data.data() + magiclen);
+                            decoded_raw_data.data());
 
             // initalize page template context map
             mstch::map context {
diff --git a/src/tools.cpp b/src/tools.cpp
index c210b49..bf1ff16 100644
--- a/src/tools.cpp
+++ b/src/tools.cpp
@@ -785,5 +785,50 @@ namespace xmreg
         return true;
     }
 
+
+
+    // from wallet2::decrypt
+    string
+    decrypt(const std::string &ciphertext,
+            const crypto::secret_key &skey,
+            bool authenticated)
+    {
+        crypto::chacha8_key key;
+
+        crypto::generate_chacha8_key(&skey, sizeof(skey), key);
+
+        const crypto::chacha8_iv &iv = *(const crypto::chacha8_iv*)&ciphertext[0];
+
+        std::string plaintext;
+
+        plaintext.resize(ciphertext.size() - sizeof(iv) -
+                                 (authenticated ? sizeof(crypto::signature) : 0));
+
+        if (authenticated)
+        {
+            crypto::hash hash;
+            crypto::cn_fast_hash(ciphertext.data(), ciphertext.size() - sizeof(signature), hash);
+            crypto::public_key pkey;
+            crypto::secret_key_to_public_key(skey, pkey);
+
+            const crypto::signature &signature
+                    = *(const crypto::signature*)&ciphertext[ciphertext.size() - sizeof(crypto::signature)];
+
+            if (!crypto::check_signature(hash, pkey, signature))
+            {
+                cerr << "Failed to authenticate criphertext" << endl;
+                return {};
+            }
+
+        }
+
+        crypto::chacha8(
+                ciphertext.data() + sizeof(iv),
+                ciphertext.size() - sizeof(iv),
+                key, iv, &plaintext[0]);
+
+        return plaintext;
+    }
+
 }
 
diff --git a/src/tools.h b/src/tools.h
index 1dfc92e..1de0b8a 100644
--- a/src/tools.h
+++ b/src/tools.h
@@ -237,6 +237,13 @@ namespace xmreg
     bool
     get_dummy_account_keys(account_keys& dummy_keys, bool testnet = false);
 
+
+    // from wallet2::decrypt
+    string
+    decrypt(const std::string &ciphertext,
+            const crypto::secret_key &skey,
+            bool authenticated = true);
+
 }
 
 #endif //XMREG01_TOOLS_H