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Date: Sun, 02 May 2021 22:28:16 +0200
From: Sören Tempel <soeren@...ren-tempel.net>
To: musl@...ts.openwall.com
Subject: Re: Handling of non-location specific TZ values
Rich Felker <dalias@...c.org> wrote:
> Yes. I suspect we can get by with calling getname with a dummy output
> array, then checking if the next character is one of +, -, or a digit.
> If not (in particular, if it's a null character) then we can attempt
> loading it as a file.
Maybe something along the following? Not too familiar with the musl code
base so not sure if including ctype.h is allowed etc.
diff --git a/src/time/__tz.c b/src/time/__tz.c
index 09a6317e..6bc183d0 100644
--- a/src/time/__tz.c
+++ b/src/time/__tz.c
@@ -3,6 +3,7 @@
#include <limits.h>
#include <stdlib.h>
#include <string.h>
+#include <ctype.h>
#include <sys/mman.h>
#include "libc.h"
#include "lock.h"
@@ -125,13 +126,13 @@ static size_t zi_dotprod(const unsigned char *z, const unsigned char *v, size_t
static void do_tzset()
{
char buf[NAME_MAX+25], *pathname=buf+24;
- const char *try, *s, *p;
+ const char *try, *s, *orig;
const unsigned char *map = 0;
size_t i;
static const char search[] =
"/usr/share/zoneinfo/\0/share/zoneinfo/\0/etc/zoneinfo/\0";
- s = getenv("TZ");
+ s = orig = getenv("TZ");
if (!s) s = "/etc/localtime";
if (!*s) s = __utc;
@@ -154,11 +155,19 @@ static void do_tzset()
}
if (old_tz) memcpy(old_tz, s, i+1);
- /* Non-suid can use an absolute tzfile pathname or a relative
- * pathame beginning with "."; in secure mode, only the
- * standard path will be searched. */
- if (*s == ':' || ((p=strchr(s, '/')) && !memchr(s, ',', p-s))) {
+ /* The TZ format specified by POSIX consists of a mandatory
+ * time zone name and a mandatory offset. We determine the
+ * name using getname, if the next character cannot constitute
+ * a valid offset (or the TZ value starts with a colon) we
+ * interpret the TZ environment variable as a zoneinfo file name. */
+ getname(std_name, &s);
+ if (*s == ':' || (!isdigit(*s) && *s != '+' && *s != '-')) {
if (*s == ':') s++;
+ else if (orig) s = orig;
+
+ /* Non-suid can use an absolute tzfile pathname or a relative
+ * pathame beginning with "."; in secure mode, only the
+ * standard path will be searched. */
if (*s == '/' || *s == '.') {
if (!libc.secure || !strcmp(s, "/etc/localtime"))
map = __map_file(s, &map_size);
Patch can be tested using date(1). For instance, compare the output of
`TZ=CET date` on a patched and unpatched system with an installed
zoneinfo database.
> It might be worth adding a special exception for "UTC" and "GMT" so
> that they are always interpreted as "UTC0" and "GMT0" and can't be
> overridden by a bogus file in the zoneinfo path, for the sake of
> software that does "TZ=UTC cmd" to avoid any timezone shenanigans.
Maybe that can be done in a separate commit?
Greetings,
Sören
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