fix: #8034 chown parse trailing colon as implicit group-is-user

src/uu/chown/src/chown.rs

@@ -203,7 +203,16 @@ fn parse_spec(spec: &str, sep: char) -> UResult<(Option<u32>, Option<u32>)> {
     assert!(['.', ':'].contains(&sep));
     let mut args = spec.splitn(2, sep);
     let user = args.next().unwrap_or("");
-    let group = args.next().unwrap_or("");
+    let mut implicit_group_is_user = false;
+    let group = args.next().map_or("", |g| {
+        if g.is_empty() && sep == ':' {
+            // argument ended with a colon, implicit group == user
+            implicit_group_is_user = true;
+            user
+        } else {
+            g
+        }
+    });
 
     // dot separator: try as username first, fall back to owner.group (like GNU)
     if sep == ':' && !spec.contains(':') && spec.contains('.') {
@@ -221,7 +230,10 @@ fn parse_spec(spec: &str, sep: char) -> UResult<(Option<u32>, Option<u32>)> {
     let uid = parse_uid(user, spec)?;
     let gid = parse_gid(group, spec)?;
 
-    if user.chars().next().is_some_and(char::is_numeric) && group.is_empty() && spec != user {
+    if user.chars().next().is_some_and(char::is_numeric)
+        && (group.is_empty() || implicit_group_is_user)
+        && spec != user
+    {
         // if the arg starts with an id numeric value, the group isn't set but the separator is provided,
         // we should fail with an error
         return Err(USimpleError::new(
@@ -263,5 +275,17 @@ mod test {
             parse_spec("12345:54321", ':'),
             Ok((Some(12345), Some(54321)))
         ));
+        // Implicit group-is-user does not work with IDs
+        assert_eq!(
+            "chown-error-invalid-spec",
+            format!("{}", parse_spec("0:", ':').err().unwrap()),
+        );
+    }
+
+    /// root user uid/gid unresolvable in some environments
+    #[test]
+    #[cfg(target_os = "linux")]
+    fn test_parse_spec_named() {
+        assert!(matches!(parse_spec("root:", ':'), Ok((Some(0), Some(0)))));
     }
 }

tests/by-util/test_chown.rs

@@ -133,13 +133,46 @@ fn test_chown_only_owner_colon() {
     let file1 = "test_chown_file1";
     at.touch(file1);
 
-    scene
-        .ucmd()
-        .arg(format!("{user_name}:"))
-        .arg("--verbose")
-        .arg(file1)
-        .succeeds()
-        .stderr_contains("retained as");
+    let result = scene.cmd("id").arg("-gn").run();
+    if skipping_test_is_okay(&result, "id: cannot find name for group ID") {
+        return;
+    }
+    let group_name = String::from(result.stdout_str().trim());
+    assert!(!group_name.is_empty());
+
+    // In some test environments user and group are different, and the user
+    // is not allowed the file to its current group, in those cases, it should fail.
+    if group_name == user_name {
+        let success = scene
+            .ucmd()
+            .arg(format!("{user_name}:"))
+            .arg("--verbose")
+            .arg(file1)
+            .succeeds();
+        let stderr = success.stderr_str();
+        #[cfg(target_os = "openbsd")]
+        {
+            // Ugly hack because the openbsd runner has sticky file creation set to wheel for
+            // our directory, which make the group change when invoked
+            assert!(stderr.contains("retained as") || stderr.contains("changed ownership"));
+        }
+        #[cfg(not(target_os = "openbsd"))]
+        {
+            assert!(stderr.contains("retained as"));
+        }
+    } else {
+        let failure = scene
+            .ucmd()
+            .arg(format!("{user_name}:"))
+            .arg("--verbose")
+            .arg(file1)
+            .fails();
+        // Depending on the environment, it may be a forbidden group (failed to change) or group not existing (invalid group)
+        assert!(
+            failure.stderr_str().contains("failed to change")
+                || failure.stderr_str().contains("invalid group")
+        );
+    }
 
     scene
         .ucmd()
@@ -150,13 +183,17 @@ fn test_chown_only_owner_colon() {
         .stderr_contains("retained as")
         .stderr_contains("warning: '.' should be ':'");
 
-    scene
+    let failure = scene
         .ucmd()
         .arg("root:")
         .arg("--verbose")
         .arg(file1)
-        .fails()
-        .stderr_contains("failed to change");
+        .fails();
+    // Depending on the environment, it may be a forbidden group (failed to change) or group not existing (invalid group)
+    assert!(
+        failure.stderr_str().contains("failed to change")
+            || failure.stderr_str().contains("invalid group")
+    );
 }
 
 #[test]
@@ -210,6 +247,11 @@ fn test_chown_dot_separator_warning() {
         result.stderr_str()
     );
 
+    let result = scene.cmd("id").arg("-gn").run();
+    if skipping_test_is_okay(&result, "id: cannot find name for group ID") {
+        return;
+    }
+
     // chown user: file should not warn
     scene
         .ucmd()