Merge pull request #121 from fluffypony/master

Fix tree_hash, patch for bad block 202612

src/crypto/tree-hash.c

@@ -35,7 +35,43 @@
 
 #include "hash-ops.h"
 
+/// Quick check if this is power of two (use on unsigned types; in this case for size_t only)
+bool ispowerof2_size_t(size_t x) {
+	return x && !(x & (x - 1));
+}
+
+/*** 
+* Round to power of two, for count>=3 and for count being not too large (as reasonable for tree hash calculations)
+*/
+size_t tree_hash_cnt(size_t count) {
+	assert( count >= 3); // cases for 0,1,2 are handled elsewhere
+	// Round down the count size: fun(2**n)= 2**(n-1) to round down to power of two
+	size_t tmp = count - 1;
+	size_t jj = 1;
+	for (jj=1 ; tmp != 0 ; ++jj) {
+		tmp /= 2; // dividing by 2 until to get how many powers of 2 fits size_to tmp
+	}
+	size_t cnt = 1 << (jj-2); // cnt is the count, but rounded down to power of two
+	// printf("count=%zu cnt=%zu jj=%zu tmp=%zu \n" , count,cnt,jj,tmp);
+	assert( cnt > 0 );	assert( cnt >= count/2 ); 	assert( cnt <= count );
+	assert( ispowerof2_size_t( cnt ));
+	return cnt;
+}
+
 void tree_hash(const char (*hashes)[HASH_SIZE], size_t count, char *root_hash) {
+// The blockchain block at height 202612 http://monerochain.info/block/bbd604d2ba11ba27935e006ed39c9bfdd99b76bf4a50654bc1e1e61217962698
+// contained 514 transactions, that triggered bad calculation of variable "cnt" in the original version of this function
+// as from CryptoNote code.
+//
+// This bug applies to all CN altcoins.
+//
+// Mathematical bug here was first published on 14:45:34 (GMT+2) 2014-09-04 by Rafal Freeman <rfree>
+// https://github.com/rfree2monero/bitmonero/commit/b417abfb7a297d09f1bbb6de29030f8de9952ac8
+// and soon also applied to CryptoNote (15:10 GMT+2), and BoolBerry used not fully correct work around:
+// the work around of sizeof(size_t)*8 or <<3 as used before in 2 coins and in BBL later was blocking
+// exploitation on normal platforms, how ever we strongly recommend the following fix because it removes
+// mistake in mathematical formula.
+
   assert(count > 0);
   if (count == 1) {
     memcpy(root_hash, hashes, HASH_SIZE);
@@ -43,24 +79,30 @@ void tree_hash(const char (*hashes)[HASH_SIZE], size_t count, char *root_hash) {
     cn_fast_hash(hashes, 2 * HASH_SIZE, root_hash);
   } else {
     size_t i, j;
-    size_t cnt = count - 1;
+
+    size_t cnt = tree_hash_cnt( count );
+    size_t max_size_t = (size_t) -1; // max allowed value of size_t 
+    assert( cnt < max_size_t/2 ); // reasonable size to avoid any overflows. /2 is extra; Anyway should be limited much stronger by logical code 
+    // as we have sane limits on transactions counts in blockchain rules
+
     char (*ints)[HASH_SIZE];
-    for (i = 1; i < sizeof(size_t); i <<= 1) {
-      cnt |= cnt >> i;
-    }
-    cnt &= ~(cnt >> 1);
-    ints = alloca(cnt * HASH_SIZE);
+    size_t ints_size = cnt * HASH_SIZE;
+    ints = alloca(ints_size); 	memset( ints , 0 , ints_size);  // allocate, and zero out as extra protection for using uninitialized mem
+
     memcpy(ints, hashes, (2 * cnt - count) * HASH_SIZE);
+
     for (i = 2 * cnt - count, j = 2 * cnt - count; j < cnt; i += 2, ++j) {
       cn_fast_hash(hashes[i], 64, ints[j]);
     }
     assert(i == count);
+
     while (cnt > 2) {
       cnt >>= 1;
       for (i = 0, j = 0; j < cnt; i += 2, ++j) {
         cn_fast_hash(ints[i], 64, ints[j]);
       }
     }
+
     cn_fast_hash(ints[0], 64, root_hash);
   }
 }

src/cryptonote_core/blockchain_storage.cpp

@@ -88,7 +88,28 @@ bool blockchain_storage::init(const std::string& config_folder)
   m_config_folder = config_folder;
   LOG_PRINT_L0("Loading blockchain...");
   const std::string filename = m_config_folder + "/" CRYPTONOTE_BLOCKCHAINDATA_FILENAME;
-  if(!tools::unserialize_obj_from_file(*this, filename))
+  if(tools::unserialize_obj_from_file(*this, filename))
+  {
+
+      // checkpoints
+      
+      // mainchain
+      for (size_t height=0; height < m_blocks.size(); ++height) 
+      {
+	CHECK_AND_ASSERT_MES((!m_checkpoints.is_in_checkpoint_zone(height)) || m_checkpoints.check_block(height,get_block_hash(m_blocks[height].bl)),false,"checkpoint fail, blockchain.bin invalid");
+      }
+
+      // check alt chains
+      #if 0
+      // doesn't work when a checkpoint is added and there are already alt chains. However, the rest of the blockchain code suffers from the same issue, so ignore for now
+      // see issue #118
+      BOOST_FOREACH(blocks_ext_by_hash::value_type& alt_block, m_alternative_chains)
+      {
+	CHECK_AND_ASSERT_MES(m_checkpoints.is_alternative_block_allowed(m_blocks.size()-1,alt_block.second.height),false,"stored alternative block not allowed, blockchain.bin invalid");
+      }
+      #endif
+  }
+  else
   {
       LOG_PRINT_L0("Can't load blockchain storage from file, generating genesis block.");
       block bl = boost::value_initialized<block>();
@@ -743,7 +764,7 @@ bool blockchain_storage::handle_alternative_block(const block& b, const crypto::
     return false;
   }
 
-  //block is not related with head of main chain
+  //Block is not related with head of main chain
   //first of all - look in alternative chains container
   auto it_main_prev = m_blocks_index.find(b.prev_id);
   auto it_prev = m_alternative_chains.find(b.prev_id);

src/cryptonote_core/checkpoints_create.h

@@ -42,6 +42,10 @@ namespace cryptonote {
     ADD_CHECKPOINT(29556, "53c484a8ed91e4da621bb2fa88106dbde426fe90d7ef07b9c1e5127fb6f3a7f6");
     ADD_CHECKPOINT(50000, "0fe8758ab06a8b9cb35b7328fd4f757af530a5d37759f9d3e421023231f7b31c");
     ADD_CHECKPOINT(80000, "a62dcd7b536f22e003ebae8726e9e7276f63d594e264b6f0cd7aab27b66e75e3");
+    ADD_CHECKPOINT(202612, "bbd604d2ba11ba27935e006ed39c9bfdd99b76bf4a50654bc1e1e61217962698");
+    ADD_CHECKPOINT(202613, "e2aa337e78df1f98f462b3b1e560c6b914dec47b610698b7b7d1e3e86b6197c2"); // from chainradar; verify this
+    ADD_CHECKPOINT(202614, "c29e3dc37d8da3e72e506e31a213a58771b24450144305bcba9e70fa4d6ea6fb"); // from chainradar; verify this
+    ADD_CHECKPOINT(205000, "5d3d7a26e6dc7535e34f03def711daa8c263785f73ec1fadef8a45880fde8063"); // from chainradar; verify this
     return true;
   }
 }

src/cryptonote_core/cryptonote_format_utils.cpp

@@ -635,10 +635,22 @@ namespace cryptonote
 
     if (string_tools::pod_to_hex(block_blob_hash) == correct_blob_hash_202612)
     {
-      res = string_tools::hex_to_pod(existing_block_id_202612);
+      string_tools::hex_to_pod(existing_block_id_202612, res);
       return true;
     }
-    return get_object_hash(get_block_hashing_blob(b), res);
+    bool hash_result = get_object_hash(get_block_hashing_blob(b), res);
+
+    if (hash_result)
+    {
+      // make sure that we aren't looking at a block with the 202612 block id but not the correct blobdata
+      if (string_tools::pod_to_hex(res) == existing_block_id_202612)
+      {
+        LOG_ERROR("Block with block id for 202612 but incorrect block blob hash found!");
+        res = null_hash;
+        return false;
+      }
+    }
+    return hash_result;
   }
   //---------------------------------------------------------------
   crypto::hash get_block_hash(const block& b)
@@ -677,6 +689,13 @@ namespace cryptonote
   //---------------------------------------------------------------
   bool get_block_longhash(const block& b, crypto::hash& res, uint64_t height)
   {
+    // block 202612 bug workaround
+    const std::string longhash_202612 = "84f64766475d51837ac9efbef1926486e58563c95a19fef4aec3254f03000000";
+    if (height == 202612)
+    {
+      string_tools::hex_to_pod(longhash_202612, res);
+      return true;
+    }
     block b_local = b; //workaround to avoid const errors with do_serialize
     blobdata bd = get_block_hashing_blob(b);
     crypto::cn_slow_hash(bd.data(), bd.size(), res);