Implement setgid script support.

TXR now notices that it's running setgid, and
implements setgid logic for scripts.

* sysif.c (orig_egid, real_gid, is_setgid): New static
variables.
(repress_privilege): Treat real and effective
group ID similarly to user ID. Save them in global
variables, and set the is_setgid flag.
(drop_privilege): Drop setgid privilege similarly
to setuid. Operate selectively: if neither setuid
nor setgid is in effect, do nothing, but if just
one is in effect, don't do anything for the other.
(simulate_setuid): Function renamed to simulate_setuid_setgid.
A small change is made here: if the fstat fails, just drop
privilege, don't abort. Implement setgid operation
independently of setuid. The is_setgid and is_setuid
flags are manipulated here now to get the drop_privileges
function to selectively drop setuid if we are running
a script which is only segid, or drop setgid if we are running
a setuid only script.

* sysif.h (simulate_setuid): Declaration name change to
simulate_setuid_setgid.

* txr.c (txr_main): Follow rename of simulate_setuid.

* txr.1: SETUID OPERATION section changed to SETUID/SETGID
operation, and setgid description worked into the text.

1 files changed, 2 insertions, 2 deletions

diff --git a/sysif.h b/sysif.h
index 99cb3ac0..093e4152 100644
--- a/sysif.h
+++ b/sysif.h
@@ -56,10 +56,10 @@ val stdio_fseek(FILE *, val, int whence);
 #if HAVE_GETEUID
 void repress_privilege(void);
 void drop_privilege(void);
-void simulate_setuid(val open_script);
+void simulate_setuid_setgid(val open_script);
 #else
 INLINE void repress_privilege(void) { }
 INLINE void drop_privilege(void) { }
-INLINE void simulate_setuid(val open_script) { }
+INLINE void simulate_setuid_setgid(val open_script) { }
 #endif
 void sysif_init(void);