[LTP] [PATCH v2 1/4] shell: Add tst_sudo.c helper

[Petr Vorel]

It will be used in LTP IMA tests. Not only it removes external
dependency, but also fixes problem when 'nobody' user is not possible to
use due using /usr/sbin/nologin shell.

Suggested-by: Jan Stancek <jstancek@redhat.com>
Signed-off-by: Petr Vorel <pvorel@suse.cz>
---
New in v2, suggested by Jan Stancek.
https://lore.kernel.org/ltp/CAASaF6yjdrLLVnehESx1TjsrB_z48nmN_2i585GPfkG3Vvg15Q@mail.gmail.com/

 doc/users/setup_tests.rst |  4 ++++
 testcases/lib/.gitignore  |  1 +
 testcases/lib/Makefile    |  2 +-
 testcases/lib/tst_sudo.c  | 50 +++++++++++++++++++++++++++++++++++++++
 4 files changed, 56 insertions(+), 1 deletion(-)
 create mode 100644 testcases/lib/tst_sudo.c

diff --git a/doc/users/setup_tests.rst b/doc/users/setup_tests.rst
index 38976f3b0a..9c49852830 100644
--- a/doc/users/setup_tests.rst
+++ b/doc/users/setup_tests.rst
@@ -71,6 +71,10 @@ users.
    * - LTP_IMA_LOAD_POLICY
      - Load IMA example policy, see :master:`testcases/kernel/security/integrity/ima/README.md`.
 
+   * - LTP_USR_UID, LTP_USR_GID
+     - Set UID and GID of ``nobody`` user for :doc:`../developers/api_shell_tests`,
+       see :master:`testcases/lib/tst_sudo.c`.
+
    * - LTP_VIRT_OVERRIDE
      - Overrides virtual machine detection in the test library. Setting it to
        empty string, tells the library that system is not a virtual machine.
diff --git a/testcases/lib/.gitignore b/testcases/lib/.gitignore
index 385f3c3ca6..602abdee1f 100644
--- a/testcases/lib/.gitignore
+++ b/testcases/lib/.gitignore
@@ -25,3 +25,4 @@
 /tst_timeout_kill
 /tst_res_
 /tst_run_shell
+/tst_sudo
diff --git a/testcases/lib/Makefile b/testcases/lib/Makefile
index b3a9181c11..9973090cfc 100644
--- a/testcases/lib/Makefile
+++ b/testcases/lib/Makefile
@@ -17,6 +17,6 @@ MAKE_TARGETS		:= tst_sleep tst_random tst_checkpoint tst_rod tst_kvcmp\
 			   tst_get_median tst_hexdump tst_get_free_pids tst_timeout_kill\
 			   tst_check_kconfigs tst_cgctl tst_fsfreeze tst_ns_create tst_ns_exec\
 			   tst_ns_ifmove tst_lockdown_enabled tst_secureboot_enabled tst_res_\
-			   tst_run_shell
+			   tst_run_shell tst_sudo
 
 include $(top_srcdir)/include/mk/generic_trunk_target.mk
diff --git a/testcases/lib/tst_sudo.c b/testcases/lib/tst_sudo.c
new file mode 100644
index 0000000000..e8d5d8dd9d
--- /dev/null
+++ b/testcases/lib/tst_sudo.c
@@ -0,0 +1,50 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2025 Petr Vorel <pvorel@suse.cz>
+ */
+
+#define LTP_USR_UID 65534
+#define LTP_USR_GID 65534
+
+#define TST_NO_DEFAULT_MAIN
+#include "tst_test.h"
+
+static void print_help(void)
+{
+	fprintf(stderr, "Usage: %s cmd [args] ...\n", __FILE__);
+	fprintf(stderr, "Usage: %s cmd [-h] print help\n\n", __FILE__);
+
+	fprintf(stderr, "Environment Variables\n");
+	fprintf(stderr, "LTP_USR_UID: UID of 'nobody' user, defaults %d\n",
+			LTP_USR_UID);
+	fprintf(stderr, "LTP_USR_GID: GID of 'nobody' user, defaults %d\n",
+			LTP_USR_GID);
+}
+
+int main(int argc, char *argv[])
+{
+	if (argc < 2 || !strcmp(argv[1], "-h")) {
+		print_help();
+		return 1;
+	}
+
+	unsigned uid = LTP_USR_UID, gid = LTP_USR_GID;
+
+	char *uid_env = getenv(TST_TO_STR_(LTP_USR_UID));
+	char *gid_env = getenv(TST_TO_STR_(LTP_USR_GID));
+
+	if (uid_env)
+		uid = SAFE_STRTOL(uid_env, 1, INT_MAX);
+
+	if (gid_env)
+		gid = SAFE_STRTOL(gid_env, 1, INT_MAX);
+
+	tst_res(TINFO, "UID: %d, GID: %d", uid, gid);
+	SAFE_SETGROUPS(0, NULL);
+	SAFE_SETRESGID(gid, gid, gid);
+	SAFE_SETRESUID(uid, uid, uid);
+
+	SAFE_CMD((const char * const *)&argv[1], NULL, NULL);
+
+	return 0;
+}
-- 
2.51.0