[hackers] [ubase] Simplify dologin() in su(1) || sin

[git]

commit b8dbf05ce7aee91e1cf646840f7cc7a8c7827ba9
Author: sin <s...@2f30.org>
Date:   Tue Jun 3 12:24:17 2014 +0100

    Simplify dologin() in su(1)
    
    Exec the user's shell with -l to fake a login.

diff --git a/su.c b/su.c
index f5ac7d9..2f7eace 100644
--- a/su.c
+++ b/su.c
@@ -16,7 +16,6 @@
 extern char **environ;
 
 static const char *randreply(void);
-static char *msetenv(const char *, const char *);
 static void dologin(struct passwd *);
 
 static void
@@ -161,39 +160,21 @@ randreply(void)
        return replies[rand() % LEN(replies)];
 }
 
-static char *
-msetenv(const char *name, const char *value)
-{
-       char *buf;
-       size_t sz;
-
-       sz = strlen(name) + strlen(value) + 2;
-       buf = emalloc(sz);
-       snprintf(buf, sz, "%s=%s", name, value);
-       return buf;
-}
-
 static void
 dologin(struct passwd *pw)
 {
-       char shbuf[strlen(pw->pw_shell) + 1];
-       char * const *newargv;
-       char * const *newenv;
-
-       strcpy(shbuf, pw->pw_shell);
-       newargv = (char *const[]){shbuf, NULL};
-       newenv = (char *const[]){
-               msetenv("HOME", pw->pw_dir),
-               msetenv("SHELL", pw->pw_shell),
-               msetenv("USER", pw->pw_name),
-               msetenv("LOGNAME", pw->pw_name),
-               msetenv("TERM", getenv("TERM")),
-               msetenv("PATH",
-                       strcmp(pw->pw_name, "root") == 0 ?
-                       ENV_SUPATH : ENV_PATH),
-               NULL
-       };
+       char *term = getenv("TERM");
+       clearenv();
+       setenv("HOME", pw->pw_dir, 1);
+       setenv("SHELL", pw->pw_shell, 1);
+       setenv("USER", pw->pw_name, 1);
+       setenv("LOGNAME", pw->pw_name, 1);
+       setenv("TERM", term ? term : "vt100", 1);
+       if (strcmp(pw->pw_name, "root") == 0)
+               setenv("PATH", ENV_SUPATH, 1);
+       else
+               setenv("PATH", ENV_PATH, 1);
        if (chdir(pw->pw_dir) < 0)
                eprintf("chdir %s:", pw->pw_dir);
-       execve(pw->pw_shell, newargv, newenv);
+       execlp(pw->pw_shell, pw->pw_shell, "-l", NULL);
 }