less free()s

allocate user info in a structure on the stack, this way memory is managed for
us and we don't have to free most things that would be difficult to free.

us.c

@@ -51,6 +51,7 @@
 #define MAX_HASH 1024
 #define CONF_LINE_MAX 1024
 #define GROUPS_MAX 256
+#define STR_MAX 1024
 #define FLAG_PERSIST 0x1
 #define FLAG_NOPASS 0x2
 #define FLAG_NOLOG 0x4
@@ -69,6 +70,14 @@ struct config {
 	int env_n;
 };
 
+struct user_info {
+	union {
+		struct passwd pw;
+		struct group gr;
+	} d;
+	char str[STR_MAX];
+};
+
 static void *emalloc(size_t);
 static char *estrdup(const char *);
 void *erealloc(void *, size_t);
@@ -76,8 +85,8 @@ static void usage(void);
 static void die(const char *, ...);
 static int perm_set(struct passwd *, struct group *);
 static int authenticate(uid_t, char);
-static struct passwd* user_to_passwd(const char *);
-static struct group* group_to_grp(const char *);
+static struct passwd* user_to_passwd(const char *, struct user_info *);
+static struct group* group_to_grp(const char *, struct user_info *);
 static int get_config(struct config **, int *);
 
 extern char **environ;
@@ -88,6 +97,7 @@ int main(int argc, char *argv[])
 	char *t_usr = "root", *t_grp = NULL;
 	struct passwd *t_pw;
 	struct group *t_gr;
+	struct user_info t_gr_info = {0}, t_pw_info = {0};
 	int opt, err;
 	int shellflag = 0, envflag = 0, askpass = 0;
 	while ((opt = getopt(argc, argv, "Au:g:C:se")) != -1) {
@@ -120,7 +130,9 @@ int main(int argc, char *argv[])
 	/* Get user info */
 	char *shell;
 	uid_t ruid = getuid();
-	struct passwd *my_pw = getpwuid(ruid);
+	struct passwd *my_pw = NULL;
+	struct user_info my_info = {0};
+	getpwuid_r(ruid, &my_info.d.pw, my_info.str, STR_MAX, &my_pw);
 	if (!my_pw) {
 		fprintf(stderr, "getpwid: %s\n", strerror(errno));
 		return errno;
@@ -132,10 +144,10 @@ int main(int argc, char *argv[])
 		die("getgroups:");
 
 	/* Get target user and group info */
-	t_pw = user_to_passwd(t_usr);
+	t_pw = user_to_passwd(t_usr, &t_pw_info);
 	if (!t_pw)
 		die("user_to_passwd:");
-	t_gr = group_to_grp(t_grp);
+	t_gr = group_to_grp(t_grp, &t_gr_info);
 
 	/* Don't have to wait for children */
 	struct sigaction sa = {0};
@@ -153,45 +165,44 @@ int main(int argc, char *argv[])
 	struct env_elem *env_extra = NULL;
 	struct config *conf = NULL;
 	int conf_num, conf_flags = 0, env_extra_n = 0;
-	if (get_config(&conf, &conf_num) == -1)
-		die("get_config: invalid arguments");
+	if (get_config(&conf, &conf_num) <= 0)
+		die("get_config: invalid config");
 	int here = 0;
 	for (int i = 0; i < conf_num; i++) {
 		struct passwd *who_pw, *as_pw;
 		struct group *who_gr, *as_gr;
+		struct user_info who_info = {0}, as_info = {0};
 		int who_usr = conf[i].who[0] == ':' ? 0 : 1;
 		int as_usr = conf[i].as[0] == ':' ? 0 : 1;
 		if (who_usr) {
-			who_pw = user_to_passwd(conf[i].who);
-			if (my_pw->pw_uid != who_pw->pw_uid) {
-				free(who_pw);
+			who_pw = user_to_passwd(conf[i].who, &who_info);
+			if (!who_pw)
+				die("%s not a valid user", conf[i].who);
+			if (my_pw->pw_uid != who_pw->pw_uid)
 				continue;
-			}
 		} else {
-			who_gr = group_to_grp(conf[i].who);
+			who_gr = group_to_grp(conf[i].who, &who_info);
+			if (!who_gr)
+				die("%s not a valid group", conf[i].who);
 			gid_t w_gid = who_gr->gr_gid;
 			int x = 0;
 			for (; x < n_groups && w_gid != my_groups[x]; x++);
-			if (w_gid != my_groups[x]) {
-				free(who_gr);
+			if (w_gid != my_groups[x])
 				continue;
 		}
-		}
 
 		if (as_usr) {
-			as_pw = user_to_passwd(conf[i].as);
+			as_pw = user_to_passwd(conf[i].as, &as_info);
 			if (!as_pw)
 				die("%s not a valid user", conf[i].as);
-			if (t_pw->pw_uid != as_pw->pw_uid) {
-				free(as_pw);
+			if (t_pw->pw_uid != as_pw->pw_uid)
 				continue;
-			}
 		} else if (t_gr) {
-			as_gr = group_to_grp(conf[i].as);
-			if (t_gr->gr_gid != as_gr->gr_gid) {
-				free(as_gr);
+			as_gr = group_to_grp(conf[i].as, &as_info);
+			if (!as_gr)
+				die("%s not a valid group", conf[i].as);
+			if (t_gr->gr_gid != as_gr->gr_gid)
 				continue;
-			}
 		} else {
 			continue;
 		}
@@ -210,6 +221,16 @@ int main(int argc, char *argv[])
 		}
 
 	}
+	/* We don't need conf anymore */
+	for (int i = 0; i < conf_num; i++) {
+		free(conf[i].who);
+		free(conf[i].as);
+		if (conf[i].env && conf[i].env_n)
+			free(conf[i].env);
+	}
+	free(conf);
+
+	/* No configuration was fount, can't proceed */
 	if (!here)
 		die("no rule found for user %s", my_name);
 
@@ -228,7 +249,7 @@ int main(int argc, char *argv[])
 
 	/* Set argc and argv */
 	int c_argc = argc - optind;
-	char **c_argv;
+	char **c_argv = NULL;
 	if (c_argc) {
 		c_argv = emalloc(sizeof(char *) * (c_argc + 1));
 		for (int i = 0; optind < argc; optind++, i++)
@@ -487,66 +508,56 @@ static int authenticate(uid_t uid, char ask)
 	return 0;
 }
 
-static struct passwd* user_to_passwd(const char *user)
+static struct passwd* user_to_passwd(const char *user, struct user_info *info)
 {
 	if (!user) {
 		errno = EINVAL;
 		return NULL;
 	}
 
-	struct passwd *pw, *pr;
+	struct passwd *pw;
 	long uid_l;
 	errno = 0;
 	if (user[0] != '#') {
-		pw = getpwnam(user);
+		getpwnam_r(user, &(info->d.pw), info->str, STR_MAX, &pw);
 	} else {
 		uid_l = strtol(&user[1], NULL, 10);
 		if (uid_l < 0 || errno) {
 			errno = errno ? errno : EINVAL;
 			return NULL;
 		}
-		pw = getpwuid((uid_t)uid_l);
+		getpwuid_r((uid_t)uid_l, &(info->d.pw), info->str, STR_MAX, &pw);
 	}
 
-	if (!pw) {
-		if (!errno)
+	if (!pw && !errno)
 		errno = EINVAL;
-		return NULL;
-	}
-	pr = emalloc(sizeof(struct passwd));
-	memcpy(pr, pw, sizeof(struct passwd));
-	return pr;
+	return pw;
 }
 
-static struct group* group_to_grp(const char *group)
+static struct group* group_to_grp(const char *group, struct user_info *info)
 {
 	if (!group) {
 		errno = EINVAL;
 		return NULL;
 	}
 
-	struct group *gr, *rr;
+	struct group *gr;
 	long gid_l;
 	errno = 0;
 	if (group[0] != '#') {
-		gr = getgrnam(group);
+		getgrnam_r(group, &(info->d.gr), info->str, STR_MAX, &gr);
 	} else {
 		gid_l = strtol(&group[1], NULL, 10);
 		if (gid_l < 0 || errno) {
 			errno = errno ? errno : EINVAL;
 			return NULL;
 		}
-		gr = getgrgid((gid_t)gid_l);
+		getgrgid_r((gid_t)gid_l, &(info->d.gr), info->str, STR_MAX, &gr);
 	}
 
-	if (!gr) {
-		if (!errno)
+	if (!gr && !errno)
 		errno = EINVAL;
-		return NULL;
-	}
-	rr = emalloc(sizeof(struct group));
-	memcpy(rr, gr, sizeof(struct group));
-	return rr;
+	return gr;
 }
 
 void die(const char *fmt, ...)
@@ -690,5 +701,5 @@ static int get_config(struct config **conf, int *num)
 		*num += 1;
 	}
 	fclose(fp);
-	return 0;
+	return *num;
 }