cryptonote: sort tx_extra fields

This removes some small amount of fingerprinting entropy.
There is no consensus rule to require this since this field
is technically free form, and a transaction is free to have
custom data in it.

src/cryptonote_basic/cryptonote_basic.h

@@ -47,7 +47,6 @@
 #include "crypto/crypto.h"
 #include "crypto/hash.h"
 #include "misc_language.h"
-#include "tx_extra.h"
 #include "ringct/rctTypes.h"
 #include "device/device.hpp"
 

src/cryptonote_basic/cryptonote_format_utils.cpp

@@ -376,6 +376,91 @@ namespace cryptonote
     return true;
   }
   //---------------------------------------------------------------
+  template<typename T>
+  static bool pick(binary_archive<true> &ar, std::vector<tx_extra_field> &fields, uint8_t tag)
+  {
+    std::vector<tx_extra_field>::iterator it;
+    while ((it = std::find_if(fields.begin(), fields.end(), [](const tx_extra_field &f) { return f.type() == typeid(T); })) != fields.end())
+    {
+      bool r = ::do_serialize(ar, tag);
+      CHECK_AND_NO_ASSERT_MES_L1(r, false, "failed to serialize tx extra field");
+      r = ::do_serialize(ar, boost::get<T>(*it));
+      CHECK_AND_NO_ASSERT_MES_L1(r, false, "failed to serialize tx extra field");
+      fields.erase(it);
+    }
+    return true;
+  }
+  //---------------------------------------------------------------
+  bool sort_tx_extra(const std::vector<uint8_t>& tx_extra, std::vector<uint8_t> &sorted_tx_extra, bool allow_partial)
+  {
+    std::vector<tx_extra_field> tx_extra_fields;
+
+    if(tx_extra.empty())
+    {
+      sorted_tx_extra.clear();
+      return true;
+    }
+
+    std::string extra_str(reinterpret_cast<const char*>(tx_extra.data()), tx_extra.size());
+    std::istringstream iss(extra_str);
+    binary_archive<false> ar(iss);
+
+    bool eof = false;
+    size_t processed = 0;
+    while (!eof)
+    {
+      tx_extra_field field;
+      bool r = ::do_serialize(ar, field);
+      if (!r)
+      {
+        MWARNING("failed to deserialize extra field. extra = " << string_tools::buff_to_hex_nodelimer(std::string(reinterpret_cast<const char*>(tx_extra.data()), tx_extra.size())));
+        if (!allow_partial)
+          return false;
+        break;
+      }
+      tx_extra_fields.push_back(field);
+      processed = iss.tellg();
+
+      std::ios_base::iostate state = iss.rdstate();
+      eof = (EOF == iss.peek());
+      iss.clear(state);
+    }
+    if (!::serialization::check_stream_state(ar))
+    {
+      MWARNING("failed to deserialize extra field. extra = " << string_tools::buff_to_hex_nodelimer(std::string(reinterpret_cast<const char*>(tx_extra.data()), tx_extra.size())));
+      if (!allow_partial)
+        return false;
+    }
+    MTRACE("Sorted " << processed << "/" << tx_extra.size());
+
+    std::ostringstream oss;
+    binary_archive<true> nar(oss);
+
+    // sort by:
+    if (!pick<tx_extra_pub_key>(nar, tx_extra_fields, TX_EXTRA_TAG_PUBKEY)) return false;
+    if (!pick<tx_extra_additional_pub_keys>(nar, tx_extra_fields, TX_EXTRA_TAG_ADDITIONAL_PUBKEYS)) return false;
+    if (!pick<tx_extra_nonce>(nar, tx_extra_fields, TX_EXTRA_NONCE)) return false;
+    if (!pick<tx_extra_merge_mining_tag>(nar, tx_extra_fields, TX_EXTRA_MERGE_MINING_TAG)) return false;
+    if (!pick<tx_extra_mysterious_minergate>(nar, tx_extra_fields, TX_EXTRA_MYSTERIOUS_MINERGATE_TAG)) return false;
+    if (!pick<tx_extra_padding>(nar, tx_extra_fields, TX_EXTRA_TAG_PADDING)) return false;
+
+    // if not empty, someone added a new type and did not add a case above
+    if (!tx_extra_fields.empty())
+    {
+      MERROR("tx_extra_fields not empty after sorting, someone forgot to add a case above");
+      return false;
+    }
+
+    std::string oss_str = oss.str();
+    if (allow_partial && processed < tx_extra.size())
+    {
+      MDEBUG("Appending unparsed data");
+      oss_str += std::string((const char*)tx_extra.data() + processed, tx_extra.size() - processed);
+    }
+    sorted_tx_extra = std::vector<uint8_t>(oss_str.begin(), oss_str.end());
+    return true;
+  }
+  //---------------------------------------------------------------
   crypto::public_key get_tx_pub_key_from_extra(const std::vector<uint8_t>& tx_extra, size_t pk_index)
   {
     std::vector<tx_extra_field> tx_extra_fields;

src/cryptonote_basic/cryptonote_format_utils.h

@@ -31,6 +31,7 @@
 #pragma once
 #include "blobdatatype.h"
 #include "cryptonote_basic_impl.h"
+#include "tx_extra.h"
 #include "account.h"
 #include "subaddress_index.h"
 #include "include_base_utils.h"
@@ -64,6 +65,7 @@ namespace cryptonote
   }
 
   bool parse_tx_extra(const std::vector<uint8_t>& tx_extra, std::vector<tx_extra_field>& tx_extra_fields);
+  bool sort_tx_extra(const std::vector<uint8_t>& tx_extra, std::vector<uint8_t> &sorted_tx_extra, bool allow_partial = false);
   crypto::public_key get_tx_pub_key_from_extra(const std::vector<uint8_t>& tx_extra, size_t pk_index = 0);
   crypto::public_key get_tx_pub_key_from_extra(const transaction_prefix& tx, size_t pk_index = 0);
   crypto::public_key get_tx_pub_key_from_extra(const transaction& tx, size_t pk_index = 0);