[PATCH v2] libuuid: Fix pre-1970 UUID v1 timestamp wraparound

[Kiran Rangoon <kiranrangoon0@gmail.com>]

gregorian_to_unix now returns -1 and sets errno=EOVERFLOW
for timestamps before the Unix epoch. uuid_time_v1 and uuid_time_v6
now use signed arithmetic to prevent unsigned wraparound.

This fixes uuidparse displaying far-future dates for historical UUIDs.

The regression test has been updated to show actual result instead of hardcoded wrong
date.

Example output:
    $ ./build/uuidparse bf2eb110-d788-1003-aa59-ce1e9e293641
Before:
    60041-08-13 16:41:36,271592-04:00
After:
    1969-12-31 19:00:00,000000-05:00

Handling negative timestamps gracefully would require broader changes, so I’ve kept this patch focused on preventing pre-1970 wraparound.

Signed-off-by: Kiran Rangoon <kiranrangoon0@gmail.com>
---
 libuuid/src/uuid_time.c       | 15 +++++++++++----
 tests/expected/uuid/uuidparse |  2 +-
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/libuuid/src/uuid_time.c b/libuuid/src/uuid_time.c
index c7516152b..f0d2c8f36 100644
--- a/libuuid/src/uuid_time.c
+++ b/libuuid/src/uuid_time.c
@@ -60,15 +60,22 @@
 /* prototype to make compiler happy */
 time_t __uuid_time(const uuid_t uu, struct timeval *ret_tv);
 
-static uint64_t gregorian_to_unix(uint64_t ts)
+static int64_t gregorian_to_unix(uint64_t ts)
 {
-	return ts - ((((uint64_t) 0x01B21DD2) << 32) + 0x13814000);
+    const uint64_t offset = 0x01B21DD213814000ULL;
+
+    if (ts < offset) {
+        errno = EOVERFLOW;
+        return -1;
+    }
+
+    return ts - offset;
 }
 
 static void uuid_time_v1(const struct uuid *uuid, struct timeval *tv)
 {
 	uint32_t high;
-	uint64_t clock_reg;
+	int64_t clock_reg;
 
 	high = uuid->time_mid | ((uuid->time_hi_and_version & 0xFFF) << 16);
 	clock_reg = uuid->time_low | ((uint64_t) high << 32);
@@ -80,7 +87,7 @@ static void uuid_time_v1(const struct uuid *uuid, struct timeval *tv)
 
 static void uuid_time_v6(const struct uuid *uuid, struct timeval *tv)
 {
-	uint64_t clock_reg;
+	int64_t clock_reg;
 
 	clock_reg = uuid->time_low;
 	clock_reg <<= 16;
diff --git a/tests/expected/uuid/uuidparse b/tests/expected/uuid/uuidparse
index 9edb05e4e..0f521a760 100644
--- a/tests/expected/uuid/uuidparse
+++ b/tests/expected/uuid/uuidparse
@@ -11,7 +11,7 @@ UUID                                  VARIANT   TYPE       TIME
 00000000-0000-3000-8000-000000000000  DCE       name-based 
 00000000-0000-4000-8000-000000000000  DCE       random     
 00000000-0000-5000-8000-000000000000  DCE       sha1-based 
-00000000-0000-6000-8000-000000000000  DCE       time-v6    60038-03-11 05:36:10,955161+00:00
+00000000-0000-6000-8000-000000000000  DCE       time-v6    1970-01-01 00:00:00,000000+00:00
 00000000-0000-0000-d000-000000000000  Microsoft            
 00000000-0000-1000-d000-000000000000  Microsoft            
 00000000-0000-2000-d000-000000000000  Microsoft            
-- 
2.47.3