id: Test -p with root-owned suid binary

Author: frendsick

tests/by-util/test_id.rs

@@ -5,9 +5,17 @@
 
 // spell-checker:ignore (ToDO) coreutil
 
+use std::fs::read;
+use std::io::Write;
+use tempfile::NamedTempFile;
+use tempfile::TempPath;
+use uucore::process::{getgid, getuid};
 use uutests::new_ucmd;
 use uutests::unwrap_or_return;
-use uutests::util::{TestScenario, check_coreutil_version, expected_result, is_ci, whoami};
+use uutests::util::{
+    TestScenario, check_coreutil_version, expected_result, get_tests_binary, is_ci,
+    run_ucmd_as_root, whoami,
+};
 use uutests::util_name;
 
 const VERSION_MIN_MULTIPLE_USERS: &str = "8.31"; // this feature was introduced in GNU's coreutils 8.31
@@ -470,3 +478,43 @@ fn test_id_pretty_print_password_record() {
         .fails()
         .stderr_contains("the argument '-p' cannot be used with '-P'");
 }
+
+#[test]
+fn test_id_pretty_print_suid_binary() {
+    if let Some(suid_coreutils_path) = create_root_owned_suid_coreutils_binary() {
+        let result = TestScenario::new(util_name!())
+            .cmd(suid_coreutils_path.to_str().unwrap())
+            .args(&[util_name!(), "-p"])
+            .succeeds();
+
+        // The `euid` line should be present only if the real UID does not belong to `root`
+        if getuid() == 0 {
+            result.stdout_does_not_contain("euid\t");
+        } else {
+            result.stdout_contains_line("euid\troot");
+        }
+
+        // The `rgid` line should be present only if the real GID does not belong to `root`
+        if getgid() == 0 {
+            result.stdout_does_not_contain("rgid\t");
+        } else {
+            result.stdout_contains("rgid\t");
+        }
+    } else {
+        print!("Test skipped; requires root user");
+    }
+}
+
+/// Create SUID temp file owned by `root:root` with the contents of the `coreutils` binary
+fn create_root_owned_suid_coreutils_binary() -> Option<TempPath> {
+    let mut temp_file = NamedTempFile::new().unwrap();
+    let coreutils_binary = read(get_tests_binary()).unwrap();
+    temp_file.write_all(&coreutils_binary).unwrap();
+    let temp_path = temp_file.into_temp_path();
+    let temp_path_str = temp_path.to_str().unwrap();
+
+    run_ucmd_as_root(&TestScenario::new("chown"), &["root:root", temp_path_str]).ok()?;
+    run_ucmd_as_root(&TestScenario::new("chmod"), &["+xs", temp_path_str]).ok()?;
+
+    Some(temp_path)
+}