Merge branch 'jk/commit-dates-parsing-fix'

Tighten codepaths that parse timestamps in commit objects.

* jk/commit-dates-parsing-fix:
  show_ident_date: fix tz range check
  log: do not segfault on gmtime errors
  log: handle integer overflow in timestamps
  date: check date overflow against time_t
  fsck: report integer overflow in author timestamps
  t4212: test bogus timestamps with git-log

6 files changed, 96 insertions, 11 deletions

diff --git a/cache.h b/cache.h
index bb0097e929..5ce6dfeddb 100644
--- a/cache.h
+++ b/cache.h
@@ -961,6 +961,7 @@ void datestamp(char *buf, int bufsize);
 unsigned long approxidate_careful(const char *, int *);
 unsigned long approxidate_relative(const char *date, const struct timeval *now);
 enum date_mode parse_date_format(const char *format);
+int date_overflows(unsigned long date);
 
 #define IDENT_STRICT	       1
 #define IDENT_NO_DATE	       2
diff --git a/date.c b/date.c
index 83b4166344..e1a2cee568 100644
--- a/date.c
+++ b/date.c
@@ -184,8 +184,10 @@ const char *show_date(unsigned long time, int tz, enum date_mode mode)
 		tz = local_tzoffset(time);
 
 	tm = time_to_tm(time, tz);
-	if (!tm)
-		return NULL;
+	if (!tm) {
+		tm = time_to_tm(0, 0);
+		tz = 0;
+	}
 
 	strbuf_reset(&timebuf);
 	if (mode == DATE_SHORT)
@@ -1113,3 +1115,20 @@ unsigned long approxidate_careful(const char *date, int *error_ret)
 	gettimeofday(&tv, NULL);
 	return approxidate_str(date, &tv, error_ret);
 }
+
+int date_overflows(unsigned long t)
+{
+	time_t sys;
+
+	/* If we overflowed our unsigned long, that's bad... */
+	if (t == ULONG_MAX)
+		return 1;
+
+	/*
+	 * ...but we also are going to feed the result to system
+	 * functions that expect time_t, which is often "signed long".
+	 * Make sure that we fit into time_t, as well.
+	 */
+	sys = t;
+	return t != sys || (t < 1) != (sys < 1);
+}
diff --git a/fsck.c b/fsck.c
index 99c0497674..64bf279fd7 100644
--- a/fsck.c
+++ b/fsck.c
@@ -245,6 +245,8 @@ static int fsck_tree(struct tree *item, int strict, fsck_error error_func)
 
 static int fsck_ident(char **ident, struct object *obj, fsck_error error_func)
 {
+	char *end;
+
 	if (**ident == '<')
 		return error_func(obj, FSCK_ERROR, "invalid author/committer line - missing space before email");
 	*ident += strcspn(*ident, "<>\n");
@@ -264,10 +266,11 @@ static int fsck_ident(char **ident, struct object *obj, fsck_error error_func)
 	(*ident)++;
 	if (**ident == '0' && (*ident)[1] != ' ')
 		return error_func(obj, FSCK_ERROR, "invalid author/committer line - zero-padded date");
-	*ident += strspn(*ident, "0123456789");
-	if (**ident != ' ')
+	if (date_overflows(strtoul(*ident, &end, 10)))
+		return error_func(obj, FSCK_ERROR, "invalid author/committer line - date causes integer overflow");
+	if (end == *ident || *end != ' ')
 		return error_func(obj, FSCK_ERROR, "invalid author/committer line - bad date");
-	(*ident)++;
+	*ident = end + 1;
 	if ((**ident != '+' && **ident != '-') ||
 	    !isdigit((*ident)[1]) ||
 	    !isdigit((*ident)[2]) ||
@@ -287,9 +290,6 @@ static int fsck_commit(struct commit *commit, fsck_error error_func)
 	int parents = 0;
 	int err;
 
-	if (commit->date == ULONG_MAX)
-		return error_func(&commit->object, FSCK_ERROR, "invalid author/committer line");
-
 	if (memcmp(buffer, "tree ", 5))
 		return error_func(&commit->object, FSCK_ERROR, "invalid format - expected 'tree' line");
 	if (get_sha1_hex(buffer+5, tree_sha1) || buffer[45] != '\n')
diff --git a/pretty.c b/pretty.c
index 87db08bd74..6e266ddf27 100644
--- a/pretty.c
+++ b/pretty.c
@@ -397,12 +397,18 @@ static const char *show_ident_date(const struct ident_split *ident,
 				   enum date_mode mode)
 {
 	unsigned long date = 0;
-	int tz = 0;
+	long tz = 0;
 
 	if (ident->date_begin && ident->date_end)
 		date = strtoul(ident->date_begin, NULL, 10);
-	if (ident->tz_begin && ident->tz_end)
-		tz = strtol(ident->tz_begin, NULL, 10);
+	if (date_overflows(date))
+		date = 0;
+	else {
+		if (ident->tz_begin && ident->tz_end)
+			tz = strtol(ident->tz_begin, NULL, 10);
+		if (tz >= INT_MAX || tz <= INT_MIN)
+			tz = 0;
+	}
 	return show_date(date, tz, mode);
 }
 
diff --git a/t/t1450-fsck.sh b/t/t1450-fsck.sh
index d730734fde..8c739c9613 100755
--- a/t/t1450-fsck.sh
+++ b/t/t1450-fsck.sh
@@ -142,6 +142,20 @@ test_expect_success '> in name is reported' '
 	grep "error in commit $new" out
 '
 
+# date is 2^64 + 1
+test_expect_success 'integer overflow in timestamps is reported' '
+	git cat-file commit HEAD >basis &&
+	sed "s/^\\(author .*>\\) [0-9]*/\\1 18446744073709551617/" \
+		<basis >bad-timestamp &&
+	new=$(git hash-object -t commit -w --stdin <bad-timestamp) &&
+	test_when_finished "remove_object $new" &&
+	git update-ref refs/heads/bogus "$new" &&
+	test_when_finished "git update-ref -d refs/heads/bogus" &&
+	git fsck 2>out &&
+	cat out &&
+	grep "error in commit $new.*integer overflow" out
+'
+
 test_expect_success 'tag pointing to nonexistent' '
 	cat >invalid-tag <<-\EOF &&
 	object ffffffffffffffffffffffffffffffffffffffff
diff --git a/t/t4212-log-corrupt.sh b/t/t4212-log-corrupt.sh
index 93c7c366cf..3fa171541a 100755
--- a/t/t4212-log-corrupt.sh
+++ b/t/t4212-log-corrupt.sh
@@ -44,4 +44,49 @@ test_expect_success 'git log --format with broken author email' '
 	test_cmp expect.err actual.err
 '
 
+munge_author_date () {
+	git cat-file commit "$1" >commit.orig &&
+	sed "s/^\(author .*>\) [0-9]*/\1 $2/" <commit.orig >commit.munge &&
+	git hash-object -w -t commit commit.munge
+}
+
+test_expect_success 'unparsable dates produce sentinel value' '
+	commit=$(munge_author_date HEAD totally_bogus) &&
+	echo "Date:   Thu Jan 1 00:00:00 1970 +0000" >expect &&
+	git log -1 $commit >actual.full &&
+	grep Date <actual.full >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'unparsable dates produce sentinel value (%ad)' '
+	commit=$(munge_author_date HEAD totally_bogus) &&
+	echo >expect &&
+	git log -1 --format=%ad $commit >actual
+	test_cmp expect actual
+'
+
+# date is 2^64 + 1
+test_expect_success 'date parser recognizes integer overflow' '
+	commit=$(munge_author_date HEAD 18446744073709551617) &&
+	echo "Thu Jan 1 00:00:00 1970 +0000" >expect &&
+	git log -1 --format=%ad $commit >actual &&
+	test_cmp expect actual
+'
+
+# date is 2^64 - 2
+test_expect_success 'date parser recognizes time_t overflow' '
+	commit=$(munge_author_date HEAD 18446744073709551614) &&
+	echo "Thu Jan 1 00:00:00 1970 +0000" >expect &&
+	git log -1 --format=%ad $commit >actual &&
+	test_cmp expect actual
+'
+
+# date is within 2^63-1, but enough to choke glibc's gmtime
+test_expect_success 'absurdly far-in-future dates produce sentinel' '
+	commit=$(munge_author_date HEAD 999999999999999999) &&
+	echo "Thu Jan 1 00:00:00 1970 +0000" >expect &&
+	git log -1 --format=%ad $commit >actual &&
+	test_cmp expect actual
+'
+
 test_done