[PATCH 3/5] date: check date overflow against time_t
- From
Jeff King <peff@peff.net>
- Date
- Feb 24, 2014, 07:39 UTC
- Message-ID
- <20140224073945.GC9969@sigill.intra.peff.net>
- In-Reply-To
- <20140224073348.GA20221@sigill.intra.peff.net>
When we check whether a timestamp has overflowed, we check only against ULONG_MAX, meaning that strtoul has overflowed. However, we also feed these timestamps to system functions like gmtime, which expect a time_t. On many systems, time_t is actually smaller than "unsigned long" (e.g., because it is signed), and we would overflow when using these functions. We don't know the actual size or signedness of time_t, but we can easily check for truncation with a simple assignment.
Signed-off-by: Jeff King <peff@peff.net> --- cache.h | 1 + date.c | 17 +++++++++++++++++ fsck.c | 2 +- 3 files changed, 19 insertions(+), 1 deletion(-)
diff --git a/cache.h b/cache.h index dc040fb..e405598 100644 --- a/cache.h +++ b/cache.h @@ -959,6 +959,7 @@ 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 83b4166..90b28f7 100644 --- a/date.c +++ b/date.c @@ -1113,3 +1113,20 @@ 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 760e072..64bf279 100644 --- a/fsck.c +++ b/fsck.c @@ -266,7 +266,7 @@ 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"); - if (strtoul(*ident, &end, 10) == ULONG_MAX) + 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");
-- 1.8.5.2.500.g8060133