added help message

us.c

@@ -41,6 +41,7 @@
 #include <signal.h>
 #include <time.h>
 #include <fcntl.h>
+#include <syslog.h>
 
 #if !defined(_XOPEN_CRYPT) || _XOPEN_CRYPT == -1
 #include <crypt.h>
@@ -51,6 +52,7 @@
 #endif
 
 #define MAX_HASH 1024
+#define PASS_MAX 1024
 #define CONF_LINE_MAX 1024
 #define GROUPS_MAX 256
 #define STR_MAX 1024
@@ -85,7 +87,7 @@ struct user_info {
 static void *emalloc(size_t);
 static char *estrdup(const char *);
 void *erealloc(void *, size_t);
-static void usage(void);
+static void usage(int);
 static void die(const char *, ...);
 static int perm_set(struct passwd *, struct group *);
 static int authenticate(uid_t, int, int);
@@ -104,7 +106,7 @@ int main(int argc, char *argv[])
 	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) {
+	while ((opt = getopt(argc, argv, "Au:g:C:seh")) != -1) {
 		switch (opt) {
 		case 'A':
 			askpass = 1;
@@ -124,8 +126,12 @@ int main(int argc, char *argv[])
 		case 'e':
 			envflag = 1;
 			break;
+		case 'h':
+			usage(1);
+			exit(EXIT_SUCCESS);
+			break;
 		case '?':
-			usage();
+			usage(0);
 			exit(EINVAL);
 			break;
 		}
@@ -242,8 +248,18 @@ int main(int argc, char *argv[])
 
 	/* Authenticate, we will be root from now on */
 	if (!(conf_flags & FLAG_NOPASS))
-		if (authenticate(my_pw->pw_uid, askpass, conf_flags & FLAG_PERSIST))
+		if (authenticate(my_pw->pw_uid, askpass, conf_flags & FLAG_PERSIST)) {
+			if (!(conf_flags & FLAG_NOLOG))
+				exit(EXIT_FAILURE);
+			char cmd[1024] = {0};
+			for (int i = optind, x = 0; argv[i] && x < 1024; i++)
+				x += snprintf(cmd, 1024-x, "%s ", argv[i]);
+			openlog("us", LOG_NOWAIT, LOG_AUTH);
+			syslog(LOG_NOTICE, "user %s tried to run %s as %s"
+			       "but failed", my_name, cmd, t_pw->pw_name);
+			closelog();
 			exit(EXIT_FAILURE);
+		}
 
 	/* Get target user's shell */
 	if (!shellflag)
@@ -333,6 +349,15 @@ int main(int argc, char *argv[])
 		goto fail_end;
 	}
 
+	if (!(conf_flags & FLAG_NOLOG)) {
+		char cmd[1024] = {0};
+		for (int i = 0, x = 0; c_argv[i] && x < 1024; i++)
+			x += snprintf(cmd, 1024-x, "%s ", c_argv[i]);
+		openlog("us", LOG_NOWAIT, LOG_AUTH);
+		syslog(LOG_INFO, "user %s ran %s as %s", my_name, cmd, t_pw->pw_name);
+		closelog();
+	}
+
 	/* Execute the command */
 	err = execvp(c_argv[0], c_argv);
 	if (err == -1)
@@ -347,17 +372,18 @@ int main(int argc, char *argv[])
 	return errno;
 }
 
-static inline void usage(void)
+static inline void usage(int complete)
 {
-	// TODO: planned options
-	// -a [program]: like sudo's askpass
-	// -u [user]: change the default user from root to user
-	// -g [group]: change the primary group to [gorup]
-	// 	both -a and -g will accept numbers with #[num] like sudo
-	// -c [file]: manually select config file
-	// something about environment
-	// something about non interactiveness
-	printf("usage: us [-seA] [-u user] [-g group] [-C config] command [args]\n");
+	printf("usage: us [-hseA] [-u user] [-g group] [-C config] command [args]\n");
+	if (!complete)
+		return;
+	printf("-h        print this message\n"
+	       "-s        use the user's shell instead of /bin/sh\n"
+	       "-e        keep the user's entire environment\n"
+	       "-A        use the command in US_ASKPASS as askpass helper\n"
+	       "-u user   set new user to 'user' instead of root\n"
+	       "-s group  set new group to 'group'\n"
+	       "-C config use specifi config file\n");
 }
 
 static int perm_set(struct passwd *pw, struct group *gr)
@@ -486,7 +512,7 @@ static int authenticate(uid_t uid, int ask, int persist)
 
 	int fd = STDIN_FILENO;
 	char *askpass = getenv("US_ASKPASS");
-	char pass[1024] = {0};
+	char pass[PASS_MAX] = {0};
 	struct termios tio_before, tio_pass;
 	if (ask && askpass) {
 		pid_t pid, parent = getpid();
@@ -532,7 +558,7 @@ static int authenticate(uid_t uid, int ask, int persist)
 		if (tcsetattr(tty_fd, TCSANOW, &tio_pass) == -1)
 			die("tcsetattr:");
 	}
-	int r = read(fd, pass, 1023);
+	int r = read(fd, pass, PASS_MAX-1);
 	if (!r || r == -1) {
 		if (errno)
 			fprintf(stderr, "read: %s\n", strerror(errno));
@@ -543,7 +569,7 @@ static int authenticate(uid_t uid, int ask, int persist)
 		waitpid(-1, NULL, 0);
 		exit(EXIT_FAILURE);
 	}
-	pass[1023] = '\0';
+	pass[PASS_MAX-1] = '\0';
 	/* Remove the terminating (if there is) \n in password */
 	int l = strlen(pass);
 	if (pass[l-1] == '\n')
@@ -558,8 +584,8 @@ static int authenticate(uid_t uid, int ask, int persist)
 
 	char *enc = crypt(pass, hash);
 	/* Remove password from memory, just to be sure */
-	memset(pass, 0, 1024);
-	if (strncmp(hash, enc, 1024)) {
+	memset(pass, 0, PASS_MAX);
+	if (strncmp(hash, enc, PASS_MAX)) {
 		printf("Authentication failure\n");
 		setuid(uid);
 		return -1;