[hackers] [PATCH 7/8] touch: Use special UTIME_NOW and UTIME_OMIT values

From: Michael Forney <mforney_AT_mforney.org>
Date: Fri, 8 Jul 2016 10:24:13 -0700

This allows users to touch files they have write access to, but aren't the
owner.

Also, remove utime.h include (not necessary since
4132561c1729df9440a6ae2566a0cccadcccf860), and make sure to check the return
value of localtime (potentially preventing a NULL pointer derefence).

---
 touch.c | 24 ++++++++++++++----------
 1 file changed, 14 insertions(+), 10 deletions(-)
diff --git a/touch.c b/touch.c
index 0e8c413..a187241 100644
--- a/touch.c
+++ b/touch.c
_AT_@ -7,14 +7,13 @@
 #include <string.h>
 #include <time.h>
 #include <unistd.h>
-#include <utime.h>
 
 #include "util.h"
 
 static int aflag;
 static int cflag;
 static int mflag;
-static struct timespec times[2];
+static struct timespec times[2] = {{.tv_nsec = UTIME_NOW}};
 
 static void
 touch(const char *file)
_AT_@ -28,10 +27,6 @@ touch(const char *file)
 		if (cflag)
 			return;
 	} else {
-		if (!aflag)
-			times[0] = st.st_atim;
-		if (!mflag)
-			times[1] = st.st_mtim;
 		if (utimensat(AT_FDCWD, file, times, 0) < 0)
 			eprintf("utimensat %s:", file);
 		return;
_AT_@ -45,14 +40,18 @@ touch(const char *file)
 }
 
 static time_t
-parsetime(char *str, time_t current)
+parsetime(char *str)
 {
+	time_t now;
 	struct tm *cur, t = { 0 };
 	int zulu = 0;
 	char *format;
 	size_t len = strlen(str);
 
-	cur = localtime(&current);
+	if ((now = time(NULL)) == -1)
+		eprintf("time:");
+	if (!(cur = localtime(&now)))
+		eprintf("localtime:");
 	t.tm_isdst = -1;
 
 	switch (len) {
_AT_@ -116,7 +115,6 @@ main(int argc, char *argv[])
 {
 	struct stat st;
 	char *ref = NULL;
-	clock_gettime(CLOCK_REALTIME, &times[0]);
 
 	ARGBEGIN {
 	case 'a':
_AT_@ -127,7 +125,8 @@ main(int argc, char *argv[])
 		break;
 	case 'd':
 	case 't':
-		times[0].tv_sec = parsetime(EARGF(usage()), times[0].tv_sec);
+		times[0].tv_sec = parsetime(EARGF(usage()));
+		times[0].tv_nsec = 0;
 		break;
 	case 'm':
 		mflag = 1;
_AT_@ -141,6 +140,7 @@ main(int argc, char *argv[])
 		break;
 	case 'T':
 		times[0].tv_sec = estrtonum(EARGF(usage()), 0, LLONG_MAX);
+		times[0].tv_nsec = 0;
 		break;
 	default:
 		usage();
_AT_@ -152,6 +152,10 @@ main(int argc, char *argv[])
 		aflag = mflag = 1;
 	if (!ref)
 		times[1] = times[0];
+	if (!aflag)
+		times[0].tv_nsec = UTIME_OMIT;
+	if (!mflag)
+		times[1].tv_nsec = UTIME_OMIT;
 
 	for (; *argv; argc--, argv++)
 		touch(*argv);
-- 
2.6.2

Received on Fri Jul 08 2016 - 19:24:13 CEST