Fix copyfile() not preserving source mode with restrictive umask

copyfile() passes the source mode to open(2), which applies the umask,
so a 0644 file copied with umask 0027 ends up 0640.

Apply the source mode with fchmod() after creating the destination.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

ChangeLog.md

@@ -4,6 +4,16 @@ Change Log
 All notable changes to the project are documented in this file.
 
 
+[UNRELEASED][]
+--------------
+
+### Fixes
+- Fix `copyfile()` not preserving the source file mode when the process
+  umask is more restrictive
+- Fix `mkpath()`, and `fmkpath()`, not applying the given mode when the
+  process umask is more restrictive, e.g., requesting 0755 with umask
+  0027 silently created a 0750 directory
+
 [v2.6.2][] - 2025-11-22
 -----------------------
 

src/copyfile.c

@@ -208,12 +208,20 @@ ssize_t copyfile(const char *src, const char *dst, int len, int opt)
 		goto exit;
 	}
 
+	/* open(2) applies umask, we want the source file mode */
+	if (fchmod(out, st.st_mode & 07777)) {
+		saved_errno = errno;
+		size = -1;
+		goto close_exit;
+	}
+
 	size = do_copy(in, out, num, buffer, BUFSIZ);
 	if (size < 0)
 		saved_errno = errno;
 	else if (keep_mtim)
 		set_mtime(in, out);
 
+close_exit:
 	close(out);
 	close(in);
 

src/makepath.c

@@ -35,6 +35,9 @@
  * @param dir   Directory to created, relative or absolute
  * @param mode  A &mode_t mode to create @a dir with
  *
+ * Directories are created with exactly @a mode, the process umask is
+ * not applied like it is for mkdir(2).
+ *
  * @returns POSIX OK(0) on success, otherwise -1 with @a errno set.
  */
 int mkpath(const char *dir, mode_t mode)
@@ -51,7 +54,10 @@ int mkpath(const char *dir, mode_t mode)
 
 	mkpath(dirname(strdupa(dir)), mode);
 
-	return mkdir(dir, mode);
+	if (mkdir(dir, mode))
+		return -1;
+
+	return chmod(dir, mode);
 }
 
 /**

test/copyfile.c

@@ -123,9 +123,32 @@ static int _copyfile()
 	return rc;
 }
 
+/* copyfile() must preserve source mode, even with a restrictive umask */
+static int _mode(void)
+{
+	const char *src = "/tmp/libite-mode-src", *dst = "/tmp/libite-mode-dst";
+	struct stat st;
+	mode_t old;
+	int rc = 1;
+
+	if (touch(src) || chmod(src, 0644))
+		return test(1, "copyfile() mode, prepare %s", src);
+
+	old = umask(0077);
+	if (copyfile(src, dst, 0, 0) >= 0 && !stat(dst, &st))
+		rc = (st.st_mode & 07777) != 0644;
+	umask(old);
+
+	erase(src);
+	erase(dst);
+
+	return test(rc, "copyfile() preserves mode 0644 with umask 0077");
+}
+
 int main(void)
 {
 	return	_fcopyfile() ||
 		_copyfile()  ||
-		_sz();
+		_sz()        ||
+		_mode();
 }

test/makepath.c

@@ -50,6 +50,34 @@ int test_fmkpath(const char *subdir)
 	return ret;
 }
 
+/* mkpath() must apply mode as given, not mode & ~umask */
+int test_umask(void)
+{
+	const char *dirs[] = { BASEDIR "/um", BASEDIR "/um/sub", NULL };
+	mode_t old = umask(0077);
+	struct stat sb;
+	int i, ret;
+
+	ret = mkpath(dirs[1], 0755);
+	umask(old);
+	if (ret) {
+		perror("Failed");
+		return ret;
+	}
+
+	for (i = 0; dirs[i]; i++) {
+		if (checkpath(dirs[i]) || stat(dirs[i], &sb))
+			return 1;
+		if ((sb.st_mode & 07777) != 0755) {
+			fprintf(stderr, "Failed: %s mode %04o, expected 0755\n",
+				dirs[i], sb.st_mode & 07777);
+			return 1;
+		}
+	}
+
+	return 0;
+}
+
 int main(void)
 {
 	int i, ret = 0;
@@ -66,14 +94,18 @@ int main(void)
 
 	mkdir(BASEDIR, 0755);
 
-	printf("Pass 1/2: makepath() =========================\n");
+	printf("Pass 1/3: makepath() =========================\n");
 	for (i = 0; list[i] && !ret; i++)
 		ret |= test_makepath(list[i]);
 
-	printf("Pass 2/2: fmkpath() ==========================\n");
+	printf("Pass 2/3: fmkpath() ==========================\n");
 	for (i = 0; list[i] && !ret; i++)
 		ret |= test_fmkpath(list[i] + strlen(BASEDIR) + 1);
 
+	printf("Pass 3/3: mkpath() with umask ================\n");
+	if (!ret)
+		ret |= test_umask();
+
 	printf("Done: Cleaning up ============================\n");
 	system("rm -rf " BASEDIR);