net: Avoid UBSan warning in ProcessMessage(...)

[practicalswift]

Avoid UBSan warning in ProcessMessage(...).

Context: #20380 (comment) (thanks Crypt-iQ!)

[maflcko]

review ACK 2a241c3

This assumes that time is negatable, which holds for system time, but not for mocktime?

I think we should disallow negative mocktime (either here or in a follow up).

[maflcko]

patch

commit eea2bf75949fd3b391711b9092e01a1843245db2
Author: MarcoFalke <falke.marco@gmail.com>
Date:   Mon Feb 1 08:03:24 2021 +0100

    util: Disallow negative mocktime

diff --git a/src/rpc/misc.cpp b/src/rpc/misc.cpp
index b75a7b8d26..38a0bddddb 100644
--- a/src/rpc/misc.cpp
+++ b/src/rpc/misc.cpp
@@ -365,13 +365,13 @@ static RPCHelpMan signmessagewithprivkey()
 static RPCHelpMan setmocktime()
 {
     return RPCHelpMan{"setmocktime",
-                "\nSet the local time to given timestamp (-regtest only)\n",
-                {
-                    {"timestamp", RPCArg::Type::NUM, RPCArg::Optional::NO, UNIX_EPOCH_TIME + "\n"
-            "   Pass 0 to go back to using the system time."},
-                },
-                RPCResult{RPCResult::Type::NONE, "", ""},
-                RPCExamples{""},
+        "\nSet the local time to given timestamp (-regtest only)\n",
+        {
+            {"timestamp", RPCArg::Type::NUM, RPCArg::Optional::NO, UNIX_EPOCH_TIME + "\n"
+             "Pass 0 to go back to using the system time."},
+        },
+        RPCResult{RPCResult::Type::NONE, "", ""},
+        RPCExamples{""},
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
 {
     if (!Params().IsMockableChain()) {
@@ -386,7 +386,10 @@ static RPCHelpMan setmocktime()
     LOCK(cs_main);
 
     RPCTypeCheck(request.params, {UniValue::VNUM});
-    int64_t time = request.params[0].get_int64();
+    const int64_t time{request.params[0].get_int64()};
+    if (time < 0) {
+        throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("Mocktime can not be negative: %s.", time));
+    }
     SetMockTime(time);
     if (request.context.Has<NodeContext>()) {
         for (const auto& chain_client : request.context.Get<NodeContext>().chain_clients) {
diff --git a/src/util/time.cpp b/src/util/time.cpp
index e96972fe12..d130e4e4d4 100644
--- a/src/util/time.cpp
+++ b/src/util/time.cpp
@@ -9,6 +9,8 @@
 
 #include <util/time.h>
 
+#include <util/check.h>
+
 #include <atomic>
 #include <boost/date_time/posix_time/posix_time.hpp>
 #include <ctime>
@@ -18,7 +20,7 @@
 
 void UninterruptibleSleep(const std::chrono::microseconds& n) { std::this_thread::sleep_for(n); }
 
-static std::atomic<int64_t> nMockTime(0); //!< For unit testing
+static std::atomic<int64_t> nMockTime(0); //!< For testing
 
 int64_t GetTime()
 {
@@ -46,6 +48,7 @@ template std::chrono::microseconds GetTime();
 
 void SetMockTime(int64_t nMockTimeIn)
 {
+    Assert(nMockTimeIn >= 0);
     nMockTime.store(nMockTimeIn, std::memory_order_relaxed);
 }
 
diff --git a/test/functional/rpc_uptime.py b/test/functional/rpc_uptime.py
index e86f91b1d0..6177970872 100755
--- a/test/functional/rpc_uptime.py
+++ b/test/functional/rpc_uptime.py
@@ -10,6 +10,7 @@ Test corresponds to code in rpc/server.cpp.
 import time
 
 from test_framework.test_framework import BitcoinTestFramework
+from test_framework.util import assert_raises_rpc_error
 
 
 class UptimeTest(BitcoinTestFramework):
@@ -18,8 +19,12 @@ class UptimeTest(BitcoinTestFramework):
         self.setup_clean_chain = True
 
     def run_test(self):
+        self._test_negative_time()
         self._test_uptime()
 
+    def _test_negative_time(self):
+        assert_raises_rpc_error(-8, "Mocktime can not be negative: -1.", self.nodes[0].setmocktime, -1)
+
     def _test_uptime(self):
         wait_time = 10
         self.nodes[0].setmocktime(int(time.time() + wait_time))

[practicalswift]

This assumes that time is negatable, which holds for system time, but not for mocktime?

I think we should disallow negative mocktime (either here or in a follow up).

Good point! I've now added your patch as a second commit. Thanks!

[maflcko]

re-ACK 3ddbf22 only change is adding patch written by me

[ajtowns]

ACK 3ddbf22 -- code review only

[maflcko]

Backported in #20901