From 5ef9bd42005485b5c392e10f123eb4c5a18c3d79 Mon Sep 17 00:00:00 2001
From: Alessandro Mauri <alemauri001@gmail.com>
Date: Sun, 28 Mar 2021 16:58:28 +0200
Subject: [PATCH] command line options

added command line options, for now only -u and -g are listed and implemented,
they allow to change user and group target (default is root)
---
 us.c | 75 +++++++++++++++++++++++++++++++++++++-----------------------
 1 file changed, 46 insertions(+), 29 deletions(-)

diff --git a/us.c b/us.c
index d74bf66..fbae2ab 100644
--- a/us.c
+++ b/us.c
@@ -39,14 +39,55 @@ static struct pam_conv conv = {misc_conv, NULL};
 
 int main (int argc, char *argv[])
 {
+	// TODO: Add arguments
 	// FIXME: change the default program to execute SHELL
-	if (argc < 2) {
+	char *t_usr = NULL, *t_grp = NULL;
+	int opt;
+	while ((opt = getopt(argc, argv, "A:u:g:C:")) != -1) {
+		switch (opt) {
+		case 'A':
+			printf("-A is not yet implemented\n");
+			exit(EXIT_FAILURE);
+			break;
+		case 'u':
+			t_usr = optarg;
+			break;
+		case 'g':
+			t_grp = optarg;
+			break;
+		case 'C':
+			printf("-C is not yet implemented\n");
+			exit(EXIT_FAILURE);
+			break;
+		case '?':
+			usage();
+			exit(EINVAL);
+			break;
+		}
+	}
+
+	// Copy argv and argc
+	int c_argc = argc - optind;
+	char **c_argv = malloc((c_argc + 1) * sizeof(char *));
+	if (!c_argv) {
+		fprintf(stderr, "malloc: %s\n", strerror(errno));
+		goto fail_end;
+	}
+	for (int i = 0; optind < argc; i++, optind++) {
+		c_argv[i] = strdup(argv[optind]);
+		if (!c_argv[i]) {
+			fprintf(stderr, "getpwid: %s\n", strerror(errno));
+			exit(errno);
+		}
+	}
+	c_argc[c_argv] = NULL;
+
+	if (c_argc == 0) {
 		usage();
-		exit(1);
+		exit(EINVAL);
 	}
 
 	uid_t ruid = getuid();
-//	gid_t rgid = getgid();
 	struct passwd *pw = getpwuid(ruid);
 	if (!pw) {
 		fprintf(stderr, "getpwid: %s\n", strerror(errno));
@@ -56,10 +97,6 @@ int main (int argc, char *argv[])
 
 	pam_handle_t *pamh;
 	int pam_err, count = 0;
-
-	// TODO: Add arguments
-
-	// TODO: add PAM authentication
 	pam_err = pam_start("User Switcher", uname, &conv, &pamh);
 	if (pam_err != PAM_SUCCESS) {
 		fprintf(stderr, "pam_start: %s\n", pam_strerror(pamh, pam_err));
@@ -85,20 +122,9 @@ int main (int argc, char *argv[])
 	pam_end(pamh, pam_err);
 	// TODO: clean up env
 
-	// Copy argv and argc
-	int c_argc = argc - 1;
-	char **c_argv = malloc((c_argc + 1) * sizeof(char *));
-	if (!c_argv) {
-		fprintf(stderr, "malloc: %s\n", strerror(errno));
-		goto fail_end;
-	}
-	for (int i = 0; i < c_argc; i++)
-		c_argv[i] = strdup(argv[i+1]);
-	c_argc[c_argv] = NULL;
-
 	errno = 0;
 	/* Set permissions */
-	if (perm_set(NULL, NULL) == -1) { // 0 = root
+	if (perm_set(t_usr, t_grp) == -1) { // 0 = root
 		fprintf(stderr, "perm_set: %s\n", strerror(errno));
 		goto fail_end;
 	}
@@ -107,17 +133,8 @@ int main (int argc, char *argv[])
 	if (execvp(*c_argv, c_argv) == -1) // execvp searches in path
 		fprintf(stderr, "execv: %s\n", strerror(errno));
 
-
-	/* We may no longer have permission to reset the permissions
-	// If exec fails reset the permissions
-	if (perm_set(pw->pw_name, NULL) == -1) { // 0 = root
-		fprintf(stderr, "perm_set: %s\n", strerror(errno));
-		goto fail_end;
-	} */
-
 	/* Cleanup and return */
 	fail_end:
-
 	/* Free up the copied argv */
 	for (int i = 0; i < c_argc; i++)
 		free(c_argv[i]);
@@ -135,7 +152,7 @@ static inline void usage (void)
 	// -c [file]: manually select config file
 	// something about environment
 	// something about non interactiveness
-	printf("usage: us [command]\n");
+	printf("usage: us [-u user] [-g group] command [args]\n");
 }
 
 static int perm_set (const char	*user, const char *group)