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Message-ID: <20260805075751.3521363-1-matthias.goergens@gmail.com>
Date: Wed, 5 Aug 2026 15:57:51 +0800
From: Matthias Goergens <matthias.goergens@...il.com>
To: musl@...ts.openwall.com
Cc: Matthias Goergens <matthias.goergens@...il.com>
Subject: [PATCH] time: fix TZif version and footer parsing
TZif v1 encodes its version as NUL, but do_tzset treats only the byte
'1' as v1. It consequently reads a valid v1 file as if it contained a
second header.
Footer detection also scans backwards from any terminal newline. It can
run before the mapping or mistake a newline in binary data for the
footer delimiter.
Use zero and nonzero version bytes to distinguish v1 from later files.
Compute the selected data block's end and accept a footer only there.
---
src/time/__tz.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/src/time/__tz.c b/src/time/__tz.c
index cfce268e..69ef0712 100644
--- a/src/time/__tz.c
+++ b/src/time/__tz.c
@@ -196,7 +196,7 @@ static void do_tzset()
zi = map;
if (map) {
int scale = 2;
- if (map[4]!='1') {
+ if (map[4]) {
size_t skip = zi_dotprod(zi+20, VEC(1,1,8,5,6,1), 6);
trans = zi+skip+44+44;
scale++;
@@ -207,9 +207,11 @@ static void do_tzset()
types = index + zi_read32(trans-12);
abbrevs = types + 6*zi_read32(trans-8);
abbrevs_end = abbrevs + zi_read32(trans-4);
- if (zi[map_size-1] == '\n') {
- for (s = (const char *)zi+map_size-2; *s!='\n'; s--);
- s++;
+ size_t footer = trans-zi + zi_dotprod(trans-24,
+ VEC(1,1,(1<<scale)+4,(1<<scale)+1,6,1), 6);
+ if (map[4] && footer < map_size-1 && zi[footer] == '\n'
+ && zi[map_size-1] == '\n') {
+ s = (const char *)zi + footer + 1;
} else {
const unsigned char *p;
__tzname[0] = __tzname[1] = 0;
--
2.55.0
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