Merge #18162: util: Avoid potential uninitialized read in FormatISO8601DateTime(int64_t) by checking gmtime_s/gmtime_r return value

12a2f377185a413b740460db36812de22ee2e041 util: Avoid potential uninitialized read in FormatISO8601DateTime(int64_t nTime) by checking gmtime_s/gmtime_r return value (practicalswift)

Pull request description:

  Avoid potential uninitialized read in `FormatISO8601DateTime(int64_t)` by checking `gmtime_s`/`gmtime_r` return value.

  Before this patch `FormatISO8601DateTime(67768036191676800)` resulted in:

  ```
  ==5930== Conditional jump or move depends on uninitialised value(s)
  ==5930==    at 0x4F44C0A: std::ostreambuf_iterator<char, std::char_traits<char> > std::num_put<char, std::ostreambuf_iterator<char, std::char_traits<char> > >::_M_insert_int<long>(std::ostreambuf_iterator<char, std::char_traits<char> >, std::ios_base&, char, long) const (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.25)
  ==5930==    by 0x4F511A4: std::ostream& std::ostream::_M_insert<long>(long) (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.25)
  ==5930==    by 0x4037C3: void tinyformat::formatValue<int>(std::ostream&, char const*, char const*, int, int const&) (tinyformat.h:358)
  ==5930==    by 0x403725: void tinyformat::detail::FormatArg::formatImpl<int>(std::ostream&, char const*, char const*, int, void const*) (tinyformat.h:543)
  ==5930==    by 0x402E02: tinyformat::detail::FormatArg::format(std::ostream&, char const*, char const*, int) const (tinyformat.h:528)
  ==5930==    by 0x401B16: tinyformat::detail::formatImpl(std::ostream&, char const*, tinyformat::detail::FormatArg const*, int) (tinyformat.h:907)
  ==5930==    by 0x4017AE: tinyformat::vformat(std::ostream&, char const*, tinyformat::FormatList const&) (tinyformat.h:1054)
  ==5930==    by 0x401765: void tinyformat::format<int, int, int, int, int, int>(std::ostream&, char const*, int const&, int const&, int const&, int const&, int const&, int const&) (tinyformat.h:1064)
  ==5930==    by 0x401656: std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > tinyformat::format<int, int, int, int, int, int>(char const*, int const&, int const&, int const&, int const&, int const&, int const&) (tinyformat.h:1073)
  ==5930==    by 0x4014CC: FormatISO8601DateTime[abi:cxx11](long) (…)
  ```

  The same goes for other very large positive and negative arguments.

  Fix by simply checking the `gmtime_s`/`gmtime_r` return value :)

ACKs for top commit:
  MarcoFalke:
    ACK 12a2f377185a413b740460db36812de22ee2e041
  theStack:
    re-ACK https://github.com/bitcoin/bitcoin/commit/12a2f377185a413b740460db36812de22ee2e041
  elichai:
    re ACK 12a2f377185a413b740460db36812de22ee2e041

Tree-SHA512: 066142670d9bf0944d41fa3f3c702b1a460b5471b93e76a619b1e818ff9bb9c09fe14c4c37e9536a04c99533f7f21d1b08ac141e1b829ff87ee54c80d0e61d48

2 files changed, 10 insertions, 6 deletions

diff --git a/ci/test/00_setup_env_native_fuzz_with_valgrind.sh b/ci/test/00_setup_env_native_fuzz_with_valgrind.sh
index 6e1c400d50..45b13a669d 100644
--- a/ci/test/00_setup_env_native_fuzz_with_valgrind.sh
+++ b/ci/test/00_setup_env_native_fuzz_with_valgrind.sh
@@ -12,7 +12,7 @@ export NO_DEPENDS=1
 export RUN_UNIT_TESTS=false
 export RUN_FUNCTIONAL_TESTS=false
 export RUN_FUZZ_TESTS=true
-export FUZZ_TESTS_CONFIG="--exclude integer,parse_iso8601 --valgrind"
+export FUZZ_TESTS_CONFIG="--valgrind"
 export GOAL="install"
 export BITCOIN_CONFIG="--enable-fuzz --with-sanitizers=fuzzer CC=clang-8 CXX=clang++-8"
 # Use clang-8, instead of default clang on bionic, which is clang-6 and does not come with libfuzzer on aarch64
diff --git a/src/util/time.cpp b/src/util/time.cpp
index 2afff2626b..f33966f149 100644
--- a/src/util/time.cpp
+++ b/src/util/time.cpp
@@ -94,10 +94,12 @@ std::string FormatISO8601DateTime(int64_t nTime) {
     struct tm ts;
     time_t time_val = nTime;
 #ifdef _MSC_VER
-    gmtime_s(&ts, &time_val);
+    if (gmtime_s(&ts, &time_val) != 0) {
 #else
-    gmtime_r(&time_val, &ts);
+    if (gmtime_r(&time_val, &ts) == nullptr) {
 #endif
+        return {};
+    }
     return strprintf("%04i-%02i-%02iT%02i:%02i:%02iZ", ts.tm_year + 1900, ts.tm_mon + 1, ts.tm_mday, ts.tm_hour, ts.tm_min, ts.tm_sec);
 }
 
@@ -105,10 +107,12 @@ std::string FormatISO8601Date(int64_t nTime) {
     struct tm ts;
     time_t time_val = nTime;
 #ifdef _MSC_VER
-    gmtime_s(&ts, &time_val);
+    if (gmtime_s(&ts, &time_val) != 0) {
 #else
-    gmtime_r(&time_val, &ts);
+    if (gmtime_r(&time_val, &ts) == nullptr) {
 #endif
+        return {};
+    }
     return strprintf("%04i-%02i-%02i", ts.tm_year + 1900, ts.tm_mon + 1, ts.tm_mday);
 }
 
@@ -124,4 +128,4 @@ int64_t ParseISO8601DateTime(const std::string& str)
     if (ptime.is_not_a_date_time() || epoch > ptime)
         return 0;
     return (ptime - epoch).total_seconds();
-}
\ No newline at end of file
+}