Support setuid operation.

* sysif.c (orig_euid, real_uid, repress_called, is_setuid):
New static variables.
(repress_privilege, drop_privilage, simulate_setuid):
New functions.
(RC_MAGIC): New preprocessor symbol.

* sysif.c (repress_privilege, drop_privilage,
simulate_setuid): Declared.

* txr.c (txr_main): Call repress_privilege to check
and remember whether we are in setuid mode, and temporarily
drop the effective uid to the real one.
(txr_main): Permanently drop privileges in all cases except
script execution. In script execution cases, go through
simulate_setuid to either set or preserve the effective
user ID, or else drop privs.

* txr.1: Documented setuid operation in new section.

1 files changed, 9 insertions, 0 deletions

diff --git a/sysif.h b/sysif.h
index 051f1d6d..22431823 100644
--- a/sysif.h
+++ b/sysif.h
@@ -49,4 +49,13 @@ off_t off_t_num(val num);
 val num_off_t(off_t offnum);
 val stdio_ftell(FILE *);
 val stdio_fseek(FILE *, val, int whence);
+#if HAVE_GETEUID
+void repress_privilege(void);
+void drop_privilege(void);
+void simulate_setuid(val open_script);
+#else
+INLINE repress_privilege(void) { }
+INLINE drop_privilege(void) { }
+INLINE void simulate_setuid(val open_script) { }
+#endif
 void sysif_init(void);