grep: handle malformed color environment values

src/lib.rs

@@ -140,7 +140,11 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     let args = expand_num_shorthand(args);
     let matches = uucore::clap_localization::handle_clap_result_with_exit_code(uu_app(), args, 2)?;
 
-    let grep_color = std::env::var("GREP_COLOR").unwrap_or_default();
+    // GNU grep ignores a malformed legacy match color without a warning.
+    let grep_color = std::env::var("GREP_COLOR")
+        .ok()
+        .filter(|value| is_color_value(value))
+        .unwrap_or_default();
     let grep_colors = std::env::var("GREP_COLORS").unwrap_or_default();
 
     let patterns_or_files: Vec<_> = matches
@@ -996,6 +1000,10 @@ impl GlobSet {
     }
 }
 
+fn is_color_value(value: &str) -> bool {
+    value.bytes().all(|b| b.is_ascii_digit() || b == b';')
+}
+
 impl<'a> ColorConfig<'a> {
     fn from_env(grep_color: &'a str, grep_colors: &'a str) -> Self {
         let mut config = Self {
@@ -1016,8 +1024,13 @@ impl<'a> ColorConfig<'a> {
             config.matched_context = grep_color;
         }
 
+        // GNU grep retains prior settings and stops at an empty assignment key
+        // or invalid value.
         for item in grep_colors.split(':') {
             if let Some((key, value)) = item.split_once('=') {
+                if key.is_empty() || !is_color_value(value) {
+                    break;
+                }
                 match key {
                     // `mt` sets matched text in any line; equivalent to ms + mc.
                     "mt" => {

tests/test_grep.rs

@@ -1327,6 +1327,16 @@ fn grep_color_env_no_warning_without_color() {
         .stdout_only("foo\n");
 }
 
+#[test]
+fn grep_color_env_malformed_value_is_ignored() {
+    let (_s, mut c) = ucmd();
+    c.env("GREP_COLOR", "4x2")
+        .args(&["--color=always", "foo"])
+        .pipe_in("foo\n")
+        .succeeds()
+        .stdout_only("\x1b[01;31m\x1b[Kfoo\x1b[m\x1b[K\n");
+}
+
 #[test]
 fn color_line_number_uses_green() {
     let (_s, mut c) = ucmd();
@@ -1387,6 +1397,17 @@ fn grep_colors_env_overrides() {
         .stdout_contains("\x1b[34m\x1b[K1\x1b[m\x1b[K");
 }
 
+#[test]
+fn grep_colors_env_stops_at_malformed_value() {
+    let (_s, mut c) = ucmd();
+    c.env("GREP_COLORS", "fn=4x2:ms=33")
+        .args(&["--color=always", "-H", "foo"])
+        .pipe_in("foo\n")
+        .succeeds()
+        .stdout_contains("\x1b[35m\x1b[K(standard input)\x1b[m\x1b[K")
+        .stdout_contains("\x1b[01;31m\x1b[Kfoo\x1b[m\x1b[K");
+}
+
 #[test]
 fn legacy_grep_color_env() {
     // uutests clears the environment by default,