sulogin: increase util-linux compatibility

Change to root's HOME. Set some envvars. Steal ctty if necessary and possible.

function                                             old     new   delta
sulogin_main                                         240     340    +100
setup_environment                                    225     233      +8
su_main                                              479     474      -5
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/1 up/down: 108/-5)            Total: 103 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 10 insertions, 8 deletions

diff --git a/include/libbb.h b/include/libbb.h
index daa310776..a0ffbef62 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -1726,15 +1726,16 @@ extern void selinux_or_die(void) FAST_FUNC;
 
 
 /* setup_environment:
- * if chdir pw->pw_dir: ok: else if to_tmp == 1: goto /tmp else: goto / or die
- * if clear_env = 1: cd(pw->pw_dir), clear environment, then set
+ * if !SETUP_ENV_NO_CHDIR:
+ *   if cd(pw->pw_dir): ok: else if SETUP_ENV_TO_TMP: cd(/tmp) else: cd(/) or die
+ * if SETUP_ENV_CLEARENV: cd(pw->pw_dir), clear environment, then set
  *   TERM=(old value)
  *   USER=pw->pw_name, LOGNAME=pw->pw_name
  *   PATH=bb_default_[root_]path
  *   HOME=pw->pw_dir
  *   SHELL=shell
- * else if change_env = 1:
- *   if not root (if pw->pw_uid != 0):
+ * else if SETUP_ENV_CHANGEENV:
+ *   if not root (if pw->pw_uid != 0) or if SETUP_ENV_CHANGEENV_LOGNAME:
  *     USER=pw->pw_name, LOGNAME=pw->pw_name
  *   HOME=pw->pw_dir
  *   SHELL=shell
@@ -1743,10 +1744,11 @@ extern void selinux_or_die(void) FAST_FUNC;
  * NB: CHANGEENV and CLEARENV use setenv() - this leaks memory!
  * If setup_environment() is used is vforked child, this leaks memory _in parent too_!
  */
-#define SETUP_ENV_CHANGEENV (1 << 0)
-#define SETUP_ENV_CLEARENV  (1 << 1)
-#define SETUP_ENV_TO_TMP    (1 << 2)
-#define SETUP_ENV_NO_CHDIR  (1 << 4)
+#define SETUP_ENV_CHANGEENV         (1 << 0)
+#define SETUP_ENV_CHANGEENV_LOGNAME (1 << 1)
+#define SETUP_ENV_CLEARENV          (1 << 2)
+#define SETUP_ENV_TO_TMP            (1 << 3)
+#define SETUP_ENV_NO_CHDIR          (1 << 4)
 void setup_environment(const char *shell, int flags, const struct passwd *pw) FAST_FUNC;
 void nuke_str(char *str) FAST_FUNC;
 #if ENABLE_FEATURE_SECURETTY && !ENABLE_PAM