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Message-ID: <20260805075726.3520396-1-matthias.goergens@gmail.com>
Date: Wed, 5 Aug 2026 15:57:26 +0800
From: Matthias Goergens <matthias.goergens@...il.com>
To: musl@...ts.openwall.com
Cc: Matthias Goergens <matthias.goergens@...il.com>
Subject: [PATCH] time: reject overflowing strptime years
The numeric-field loop accumulates directly into int. POSIX.1-2024 gives
the year inside %F unlimited width, so long input can overflow before
the result is adjusted to tm_year. Combining %C and %y can overflow too.
Accumulate a checked unsigned magnitude. Perform sign and year
adjustments in long long, and reject results that cannot fit in the int
fields of struct tm. Use the same intermediate for century composition.
---
src/time/strptime.c | 24 +++++++++++++++++-------
1 file changed, 17 insertions(+), 7 deletions(-)
diff --git a/src/time/strptime.c b/src/time/strptime.c
index 40bb37af..d4440229 100644
--- a/src/time/strptime.c
+++ b/src/time/strptime.c
@@ -2,6 +2,7 @@
#include <langinfo.h>
#include <time.h>
#include <ctype.h>
+#include <limits.h>
#include <stddef.h>
#include <string.h>
#include <strings.h>
@@ -10,6 +11,8 @@
char *strptime(const char *restrict s, const char *restrict f, struct tm *restrict tm)
{
int i, w, neg, adj, min, range, *dest, dummy;
+ unsigned x, digit;
+ long long v;
const char *ex;
size_t len;
int want_century = 0, century = 0, relyear = 0;
@@ -233,10 +236,15 @@ char *strptime(const char *restrict s, const char *restrict f, struct tm *restri
if (*s == '+') s++;
else if (*s == '-') neg=1, s++;
if (!isdigit(*s)) return 0;
- for (*dest=i=0; i<w && isdigit(*s); i++)
- *dest = *dest * 10 + *s++ - '0';
- if (neg) *dest = -*dest;
- *dest -= adj;
+ for (x=i=0; i<w && isdigit(*s); i++) {
+ digit = *s++ - '0';
+ if (x > (UINT_MAX-digit)/10) return 0;
+ x = x * 10 + digit;
+ }
+ v = neg ? -(long long)x : x;
+ v -= adj;
+ if (v < INT_MIN || v > INT_MAX) return 0;
+ *dest = v;
goto update;
symbolic_range:
for (i=2*range-1; i>=0; i--) {
@@ -255,9 +263,11 @@ char *strptime(const char *restrict s, const char *restrict f, struct tm *restri
}
}
if (want_century) {
- tm->tm_year = relyear;
- if (want_century & 2) tm->tm_year += century * 100 - 1900;
- else if (tm->tm_year <= 68) tm->tm_year += 100;
+ v = relyear;
+ if (want_century & 2) v += 100LL * century - 1900;
+ else if (v <= 68) v += 100;
+ if (v < INT_MIN || v > INT_MAX) return 0;
+ tm->tm_year = v;
}
return (char *)s;
}
--
2.55.0
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