From 883cea7dea3cedc9b45b6191f7d4e7be2d9a11ca Mon Sep 17 00:00:00 2001
From: Pieter Wuille <pieter@wuille.net>
Date: Mon, 12 Oct 2020 14:20:28 -0700
Subject: [PATCH 1/2] Restore compatibility with old CSubNet serialization

---
 src/netaddress.h | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/src/netaddress.h b/src/netaddress.h
index 3bcf6d35ca..aea0875511 100644
--- a/src/netaddress.h
+++ b/src/netaddress.h
@@ -468,7 +468,21 @@ class CSubNet
         friend bool operator!=(const CSubNet& a, const CSubNet& b) { return !(a == b); }
         friend bool operator<(const CSubNet& a, const CSubNet& b);
 
-        SERIALIZE_METHODS(CSubNet, obj) { READWRITE(obj.network, obj.netmask, obj.valid); }
+        SERIALIZE_METHODS(CSubNet, obj)
+        {
+            READWRITE(obj.network);
+            if (obj.network.IsIPv4()) {
+                // Before commit 102867c587f5f7954232fb8ed8e85cda78bb4d32, CSubNet used the last 4 bytes of netmask
+                // to store the relevant bytes for an IPv4 mask. For compatiblity reasons, keep doing so in
+                // serialized form.
+                unsigned char dummy[12] = {0};
+                READWRITE(dummy);
+                READWRITE(MakeSpan(obj.netmask).first(4));
+            } else {
+                READWRITE(obj.netmask);
+            }
+            READWRITE(obj.valid);
+        }
 };
 
 /** A combination of a network address (CNetAddr) and a (TCP) port */

From 886be97af5d4aba338b23a7b20b8560be8156231 Mon Sep 17 00:00:00 2001
From: Pieter Wuille <pieter@wuille.net>
Date: Mon, 12 Oct 2020 15:35:08 -0700
Subject: [PATCH 2/2] Ignore incorrectly-serialized banlist.dat entries

---
 src/banman.cpp     |  2 +-
 src/netaddress.cpp | 11 +++++++++++
 src/netaddress.h   |  4 ++++
 3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/src/banman.cpp b/src/banman.cpp
index 8752185a60..995fef3d07 100644
--- a/src/banman.cpp
+++ b/src/banman.cpp
@@ -184,7 +184,7 @@ void BanMan::SweepBanned()
         while (it != m_banned.end()) {
             CSubNet sub_net = (*it).first;
             CBanEntry ban_entry = (*it).second;
-            if (now > ban_entry.nBanUntil) {
+            if (!sub_net.IsValid() || now > ban_entry.nBanUntil) {
                 m_banned.erase(it++);
                 m_is_dirty = true;
                 notify_ui = true;
diff --git a/src/netaddress.cpp b/src/netaddress.cpp
index 147c775e61..4e100ff9ca 100644
--- a/src/netaddress.cpp
+++ b/src/netaddress.cpp
@@ -1109,6 +1109,17 @@ bool CSubNet::IsValid() const
     return valid;
 }
 
+bool CSubNet::SanityCheck() const
+{
+    if (!(network.IsIPv4() || network.IsIPv6())) return false;
+
+    for (size_t x = 0; x < network.m_addr.size(); ++x) {
+        if (network.m_addr[x] & ~netmask[x]) return false;
+    }
+
+    return true;
+}
+
 bool operator==(const CSubNet& a, const CSubNet& b)
 {
     return a.valid == b.valid && a.network == b.network && !memcmp(a.netmask, b.netmask, 16);
diff --git a/src/netaddress.h b/src/netaddress.h
index aea0875511..803b00481e 100644
--- a/src/netaddress.h
+++ b/src/netaddress.h
@@ -451,6 +451,8 @@ class CSubNet
         /// Is this value valid? (only used to signal parse errors)
         bool valid;
 
+        bool SanityCheck() const;
+
     public:
         CSubNet();
         CSubNet(const CNetAddr& addr, uint8_t mask);
@@ -482,6 +484,8 @@ class CSubNet
                 READWRITE(obj.netmask);
             }
             READWRITE(obj.valid);
+            // Mark invalid if the result doesn't pass sanity checking.
+            SER_READ(obj, if (obj.valid) obj.valid = obj.SanityCheck());
         }
 };