1 files changed, 72 insertions, 0 deletions
diff --git a/src/tc-switchuser.c b/src/tc-switchuser.c
new file mode 100644
index 0000000..1763527
--- /dev/null
+++ b/src/tc-switchuser.c
@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: MIT
+#ifdef HAVE_CONFIG_H
+#	include "config.h"
+#endif
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <libHX/defs.h>
+#include <libHX/option.h>
+#include <libHX/proc.h>
+#if defined(HAVE_INITGROUPS)
+
+static char *user_name, *group_name;
+static const struct HXoption options_table[] = {
+	{.sh = 'u', .type = HXTYPE_STRING, .ptr = &user_name},
+	{.sh = 'g', .type = HXTYPE_STRING, .ptr=  &group_name},
+	HXOPT_TABLEEND,
+};
+
+int main(int argc, const char **argv)
+{
+	HX_getopt(options_table, &argc, &argv, HXOPT_USAGEONERR);
+	const char *user = user_name != NULL ? user_name : "-";
+	const char *group = group_name != NULL ? group_name : "-";
+	switch (HXproc_switch_user(user_name, group_name)) {
+	case HXPROC_USER_NOT_FOUND:
+		if (user_name == NULL)
+			abort(); /* impossible outcomes */
+		printf("No such user \"%s\": %s\n", user_name, strerror(errno));
+		break;
+	case HXPROC_GROUP_NOT_FOUND:
+		if (group_name == NULL || *group_name == '\0')
+			abort(); /* impossible outcome */
+		printf("No such group \"%s\": %s\n", group_name, strerror(errno));
+		break;
+	case HXPROC_SETUID_FAILED:
+		printf("setuid %s: %s\n", user, strerror(errno));
+		break;
+	case HXPROC_SETGID_FAILED:
+		printf("setgid %s: %s\n", group, strerror(errno));
+		break;
+	case HXPROC_INITGROUPS_FAILED:
+		printf("initgroups for %s: %s\n", user, strerror(errno));
+		break;
+	case HXPROC_SU_NOOP:
+		printf("No action was performed./User identity already reached.\n");
+		/* fallthrough */
+	case HXPROC_SU_SUCCESS: {
+		gid_t list[64] = {-1};
+		int numgroups = getgroups(ARRAY_SIZE(list), list);
+		printf("Identity now: uid %lu euid %lu gid %lu egid %lu\n",
+		       static_cast(unsigned long, getuid()),
+		       static_cast(unsigned long, geteuid()),
+		       static_cast(unsigned long, getgid()),
+		       static_cast(unsigned long, getegid()));
+		printf("Secondary groups:");
+		for (int i = 0; i < numgroups; ++i)
+			printf(" %lu", static_cast(unsigned long, list[i]));
+		printf("\n");
+		break;
+	}
+	}
+	return EXIT_SUCCESS;
+}
+#else
+int main(void)
+{
+	return EXIT_SUCCESS;
+}
+#endif