time.h: fix integer overflow in MsToAbsoluteTimespec() on 32-bit architectures (#1042)

Author: dconeybe

app/src/time.h

@@ -89,8 +89,13 @@ inline timespec MsToTimespec(int milliseconds) {
 inline timespec MsToAbsoluteTimespec(int milliseconds) {
   timespec t;
   clock_gettime(CLOCK_REALTIME, &t);
-  t.tv_nsec += milliseconds * internal::kNanosecondsPerMillisecond;
-  NormalizeTimespec(&t);
+
+  const int64_t nanoseconds =
+      t.tv_nsec + (t.tv_sec * internal::kNanosecondsPerSecond) +
+      (milliseconds * internal::kNanosecondsPerMillisecond);
+
+  t.tv_sec = nanoseconds / internal::kNanosecondsPerSecond;
+  t.tv_nsec = nanoseconds % internal::kNanosecondsPerSecond;
   return t;
 }
 

app/tests/time_test.cc

@@ -62,6 +62,16 @@ TEST(TimeTests, ComparisonTests) {
   EXPECT_EQ(firebase::internal::TimespecCmp(t1, t1), 0);
   EXPECT_EQ(firebase::internal::TimespecCmp(t2, t2), 0);
 }
+
+// This test verifies the fix for the old integer overflow bug on 32-bit
+// architectures: https://github.com/firebase/firebase-cpp-sdk/pull/1042.
+TEST(TimeTests, MsToAbsoluteTimespecTest) {
+  const timespec t1 = firebase::internal::MsToAbsoluteTimespec(0);
+  const timespec t2 = firebase::internal::MsToAbsoluteTimespec(10000);
+  const int64_t ms1 = firebase::internal::TimespecToMs(t1);
+  const int64_t ms2 = firebase::internal::TimespecToMs(t2);
+  ASSERT_NEAR(ms1, ms2 - 10000, 300);
+}
 #endif
 
 // Test GetTimestamp function

release_build_files/readme.md

@@ -640,6 +640,10 @@ code.
       cause duplicate symbol linker errors in conjunction with other libraries
       ([#989](https://github.com/firebase/firebase-cpp-sdk/issues/989)).
     - GMA (iOS): Updated iOS dependency to Google Mobile Ads SDK version 9.7.0.
+    - General (Android,iOS,Linux,macOS 32-bit): Fixed an integer overflow which
+      could result in a crash or premature return when waiting for a `Future`
+      with a timeout
+      ([#1042](https://github.com/firebase/firebase-cpp-sdk/pull/1042)).
 
 ### 9.3.0
 -   Changes