Improve execsh() and don't allow anonymous shells

This patch improves the shell selection on execsh and forbid
shell with users don't registered in the passwd file.

1 files changed, 17 insertions, 13 deletions

diff --git a/st.c b/st.c
index 1c998ec..009388c 100644
--- a/st.c
+++ b/st.c
@@ -1139,23 +1139,29 @@ die(const char *errstr, ...) {
 
 void
 execsh(void) {
-        char **args;
-        char *envshell = getenv("SHELL");
-        const struct passwd *pass = getpwuid(getuid());
+        char **args, *sh;
+        const struct passwd *pw;
         char buf[sizeof(long) * 8 + 1];
 
+        errno = 0;
+        if((pw = getpwuid(getuid())) == NULL) {
+                if(errno)
+                        die("getpwuid:%s\n", strerror(errno));
+                else
+                        die("who are you?\n");
+        }
         unsetenv("COLUMNS");
         unsetenv("LINES");
         unsetenv("TERMCAP");
 
-        if(pass) {
-                setenv("LOGNAME", pass->pw_name, 1);
-                setenv("USER", pass->pw_name, 1);
-                setenv("SHELL", pass->pw_shell, 0);
-                setenv("HOME", pass->pw_dir, 0);
-        }
-
+        sh = (pw->pw_shell[0]) ? pw->pw_shell : shell;
         snprintf(buf, sizeof(buf), "%lu", xw.win);
+
+        setenv("LOGNAME", pw->pw_name, 1);
+        setenv("USER", pw->pw_name, 1);
+        setenv("SHELL", sh, 1);
+        setenv("HOME", pw->pw_dir, 1);
+        setenv("TERM", termname, 1);
         setenv("WINDOWID", buf, 1);
 
         signal(SIGCHLD, SIG_DFL);
@@ -1165,9 +1171,7 @@ execsh(void) {
         signal(SIGTERM, SIG_DFL);
         signal(SIGALRM, SIG_DFL);
 
-        DEFAULT(envshell, shell);
-        setenv("TERM", termname, 1);
-        args = opt_cmd ? opt_cmd : (char *[]){envshell, "-i", NULL};
+        args = opt_cmd ? opt_cmd : (char *[]){sh, "-i", NULL};
         execvp(args[0], args);
         exit(EXIT_FAILURE);
 }