From e032755888218cb332f6bcef2b1e56ab31a88813 Mon Sep 17 00:00:00 2001
From: weili <541602953@qq.com>
Date: Fri, 5 Jun 2026 05:27:16 +0000
Subject: [PATCH] touch: fix char-boundary panic on a multibyte char in a -t
 timestamp
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`touch -t '€123456789'` aborted with "byte index N is not a char
boundary". `parse_timestamp` routes timestamps whose char count is 10 or
13 through `prepend_century`, which byte-sliced `s[..2]` to read the YY
digits; a leading multibyte char (e.g. '€') made byte index 2 land
mid-UTF-8 and panic before the `parse::<u32>()` error could fire.

Take the first two chars instead of byte-slicing, so a multibyte/non-digit
prefix yields the invalid-date error (exit 1) like GNU instead of crashing.
---
 src/uu/touch/src/touch.rs   |  5 ++++-
 tests/by-util/test_touch.rs | 10 ++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/src/uu/touch/src/touch.rs b/src/uu/touch/src/touch.rs
index 4d1c9772c59..3fe1dcea91c 100644
--- a/src/uu/touch/src/touch.rs
+++ b/src/uu/touch/src/touch.rs
@@ -741,7 +741,10 @@ fn parse_date(ref_zoned: Zoned, s: &str) -> Result<FileTime, TouchError> {
 /// - 68 and before is interpreted as 20xx
 /// - 69 and after is interpreted as 19xx
 fn prepend_century(s: &str) -> UResult<String> {
-    let first_two_digits = s[..2].parse::<u32>().map_err(|_| {
+    // Take the first two chars rather than byte-slicing `s[..2]`: a leading
+    // multibyte char would otherwise split a UTF-8 boundary and panic.
+    let first_two: String = s.chars().take(2).collect();
+    let first_two_digits = first_two.parse::<u32>().map_err(|_| {
         USimpleError::new(
             1,
             translate!("touch-error-invalid-date-ts-format", "date" => s.quote()),
diff --git a/tests/by-util/test_touch.rs b/tests/by-util/test_touch.rs
index fbabdb75c65..0f3921b17f9 100644
--- a/tests/by-util/test_touch.rs
+++ b/tests/by-util/test_touch.rs
@@ -978,6 +978,16 @@ fn test_touch_invalid_date_format() {
         .stderr_contains("touch: invalid date format '+1000000000000 years'");
 }
 
+#[test]
+fn test_touch_invalid_timestamp_leading_multibyte_char() {
+    for ts in ["€123456789", "€23456789012"] {
+        new_ucmd!()
+            .args(&["-t", ts, "f"])
+            .fails_with_code(1)
+            .stderr_only(format!("touch: invalid date ts format '{ts}'\n"));
+    }
+}
+
 #[test]
 #[cfg(not(target_os = "freebsd"))]
 fn test_touch_symlink_with_no_deref() {