[src/trunk]: src/sys/sys Fix crgetgroups shim.

[riastradh <riastradh%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/b18f24bcda83
branches:  trunk
changeset: 1009631:b18f24bcda83
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Wed Apr 29 05:54:37 2020 +0000

description:
Fix crgetgroups shim.

- Don't use a static buffer for the result.

- kauth_cred_getgroups refuses to return more than the actual number
  of groups, so passing NGROUPS_MAX generally doesn't work.

To avoid patching zfs, just expose struct kauth_cred::cr_groups
directly, with __KAUTH_PRIVATE.  Unclear why the official API only
exposes it via memcpy or copyout anyway.

This makes unprivileged zfs operations work, by anyone with access to
/dev/zfs (which is conventionally mode 777, and which we should maybe
set it to by default; zfs has its own ACL system, zfs allow).

diffstat:

 external/cddl/osnet/sys/sys/cred.h |  20 +++++++-------------
 sys/sys/kauth.h                    |   9 +++++++--
 2 files changed, 14 insertions(+), 15 deletions(-)

diffs (75 lines):

diff -r 20924d478b28 -r b18f24bcda83 external/cddl/osnet/sys/sys/cred.h
--- a/external/cddl/osnet/sys/sys/cred.h        Wed Apr 29 04:30:40 2020 +0000
+++ b/external/cddl/osnet/sys/sys/cred.h        Wed Apr 29 05:54:37 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: cred.h,v 1.6 2019/02/06 17:56:57 christos Exp $        */
+/*     $NetBSD: cred.h,v 1.7 2020/04/29 05:54:37 riastradh Exp $       */
 
 /*-
  * Copyright (c) 2007 Pawel Jakub Dawidek <pjd%FreeBSD.org@localhost>
@@ -31,6 +31,11 @@
 #ifndef _OPENSOLARIS_SYS_CRED_H_
 #define        _OPENSOLARIS_SYS_CRED_H_
 
+#ifdef _KERNEL
+/* Needed for access to cr_groups.  */
+#define        __KAUTH_PRIVATE
+#endif
+
 #include <sys/param.h>
 #include <sys/types.h>
 
@@ -57,22 +62,11 @@
        kauth_cred_setegid(cr, g), \
        kauth_cred_setsvuid(cr, u), \
        kauth_cred_setsvgid(cr, g), 0)
+#define crgetgroups(cr)                ((cr)->cr_groups)
 #define        crsetgroups(cr, gc, ga) \
     kauth_cred_setgroups(cr, ga, gc, 0, UIO_SYSSPACE)
 #define crgetsid(cr, i) (NULL)
 
-static __inline gid_t *
-crgetgroups(cred_t *cr)
-{
-       static gid_t gids[NGROUPS_MAX];
-
-       memset(gids, 0, sizeof(gids));
-       if (kauth_cred_getgroups(cr, gids, NGROUPS_MAX, UIO_SYSSPACE) != 0) 
-               return NULL;
-       
-       return gids;
-}
-
 static __inline int
 groupmember(gid_t gid, cred_t *cr) 
 {
diff -r 20924d478b28 -r b18f24bcda83 sys/sys/kauth.h
--- a/sys/sys/kauth.h   Wed Apr 29 04:30:40 2020 +0000
+++ b/sys/sys/kauth.h   Wed Apr 29 05:54:37 2020 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: kauth.h,v 1.83 2020/02/14 04:36:33 riastradh Exp $ */
+/* $NetBSD: kauth.h,v 1.84 2020/04/29 05:54:37 riastradh Exp $ */
 
 /*-
  * Copyright (c) 2005, 2006 Elad Efrat <elad%NetBSD.org@localhost>  
@@ -57,7 +57,11 @@
 typedef        struct kauth_key       *kauth_key_t;
 
 #ifdef __KAUTH_PRIVATE /* For the debugger */
-/* 
+
+#include <sys/types.h>
+#include <sys/specificdata.h>
+
+/*
  * Credentials.
  *
  * A subset of this structure is used in kvm(3) (src/lib/libkvm/kvm_proc.c)
@@ -86,6 +90,7 @@
        gid_t cr_groups[NGROUPS];       /* group memberships */
        specificdata_reference cr_sd;   /* specific data */
 };
+
 #endif
 
 /*