uucore: report unreadable files under --ignore-missing

src/uucore/src/lib/features/checksum/validate.rs

@@ -613,7 +613,7 @@ fn get_file_to_check(
                     Ok(Box::new(f))
                 }
             }
-            Err(err) => {
+            Err(err) if err.kind() == io::ErrorKind::NotFound => {
                 if !opts.ignore_missing {
                     // yes, we have both stderr and stdout here
                     print_error(err);
@@ -622,6 +622,13 @@ fn get_file_to_check(
                 // we could not open the file but we want to continue
                 Err(LineCheckError::FileNotFound)
             }
+            Err(err) => {
+                // The file exists but cannot be opened. `--ignore-missing` does
+                // not cover this, so report it whether or not it is set.
+                print_error(err);
+                failed_open();
+                Err(LineCheckError::CantOpenFile)
+            }
         }
     }
 }
@@ -1001,8 +1008,9 @@ fn process_checksum_file(
         return Err(FileCheckError::Failed);
     }
 
-    // If a file was missing, return an error unless we explicitly ignore it.
-    if res.failed_open_file > 0 && !opts.ignore_missing {
+    // Files we could not read are a failure. Missing files are only counted
+    // when they are not ignored, so this needs no further guard.
+    if res.failed_open_file > 0 {
         return Err(FileCheckError::Failed);
     }
 

tests/by-util/test_cksum.rs

@@ -2155,6 +2155,36 @@ fn test_check_failed_to_read() {
         .stderr_contains("cksum: WARNING: 1 listed file could not be read");
 }
 
+#[test]
+#[cfg(not(windows))]
+fn test_check_ignore_missing_unopenable_file() {
+    // `--ignore-missing` excuses a file that is absent, not one that is
+    // present but cannot be opened. The latter is still a failed read.
+
+    let scene = TestScenario::new(util_name!());
+    let at = &scene.fixtures;
+
+    at.write("f", "data\n");
+    at.write(
+        "CHECKSUM",
+        "SHA1 (f) = c5d84736ba451747dd5f0eb9d17e104f3697ef47\n\
+        SHA1 (f/sub) = ffffffffffffffffffffffffffffffffffffffff\n\
+        SHA1 (not-file) = ffffffffffffffffffffffffffffffffffffffff\n",
+    );
+
+    scene
+        .ucmd()
+        .arg("--check")
+        .arg("--ignore-missing")
+        .arg("CHECKSUM")
+        .fails()
+        .stdout_is(
+            "f: OK\n\
+            f/sub: FAILED open or read\n",
+        )
+        .stderr_contains("cksum: WARNING: 1 listed file could not be read");
+}
+
 #[test]
 fn test_zero_multiple_file() {
     new_ucmd!()