net: bound what a peer can make the node allocate (#73)

Three independent bounds on what an untrusted peer can make this node allocate:

- serialize.h: reject a compact size above MAX_SIZE before reading a string or a
  vector, instead of discovering it read by read. MAX_SIZE moves from main.h to
  serialize.h, where the checks live; headers_core.h includes serialize.h first,
  so every existing user still sees it.
- main.cpp: cap an orphan transaction at 10,000 inputs. Orphans are stored and
  never validated, so mapOrphanTransactionsByPrev grew with one entry per input
  of every orphan a peer cared to send.
- rpc.cpp: drop a Stratum line nested deeper than 20 before json::parse recurses
  into it. The scan tracks string state, so a worker name containing { or [ is
  no longer mistaken for nesting.

Verified: builds clean on UCRT64; the depth scanner passes a table of legitimate
Stratum lines and nesting attacks; a node built from this branch synced the chain
from genesis to 4462 with no deserialization failure and no rejected block.

1 files changed, 7 insertions, 1 deletions

diff --git a/src/serialize.h b/src/serialize.h
index ce72c60..fa77074 100644
--- a/src/serialize.h
+++ b/src/serialize.h
@@ -20,7 +20,7 @@ class CDataStream;
 class CAutoFile;
 
 static const int VERSION = 101;
-
+static const unsigned int MAX_SIZE = 0x02000000;
 
 
 
@@ -399,6 +399,8 @@ void Unserialize(Stream& is, basic_string<C>& str, int, int)
     // only string field on a serialized type and RelayMessage casts it away --
     // so this is a guard against the next one that does, not a live hole.
     unsigned int nSize = ReadCompactSize(is);
+    if (nSize > MAX_SIZE)
+        throw std::ios_base::failure("String size too large");
     str.clear();
     unsigned int nMid = 0;
     while (nMid < nSize)
@@ -472,6 +474,8 @@ void Unserialize_impl(Stream& is, std::vector<T, A>& v, int nType, int nVersion,
     // Limit size per read so bogus size value won't cause out of memory
     v.clear();
     unsigned int nSize = ReadCompactSize(is);
+    if (nSize > MAX_SIZE)
+        throw std::ios_base::failure("Vector size too large");
     unsigned int i = 0;
     while (i < nSize)
     {
@@ -492,6 +496,8 @@ void Unserialize_impl(Stream& is, std::vector<T, A>& v, int nType, int nVersion,
 
     v.clear();
     unsigned int nSize = ReadCompactSize(is);
+    if (nSize > MAX_SIZE)
+        throw std::ios_base::failure("Vector size too large");
     unsigned int i = 0;
     unsigned int nMid = 0;
     while (nMid < nSize)