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bug#15672: Sequence of chmod and chown - patch
From: |
Paul Eggert |
Subject: |
bug#15672: Sequence of chmod and chown - patch |
Date: |
Thu, 24 Oct 2013 00:23:09 -0700 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.0 |
Thanks for the suggestion. Does the following patch work for you?
I've pushed this to the savannah master for gzip.
>From 0f167be4f843ac5fcd8f0bc120202782d09a453f Mon Sep 17 00:00:00 2001
From: Paul Eggert <address@hidden>
Date: Thu, 24 Oct 2013 00:19:56 -0700
Subject: [PATCH] gzip: fix permissions issue on Solaris-like systems
I.e., on systems that let users give files away.
* gzip.c (do_chown): New function.
(copy_stat): Use it, to change the group, then the permissions,
then the owner. Idea suggested by Vladimir Marek in
<http://bugs.gnu.org/15672#11>
---
gzip.c | 33 ++++++++++++++++++++++++---------
1 file changed, 24 insertions(+), 9 deletions(-)
diff --git a/gzip.c b/gzip.c
index 93cc738..f40cd21 100644
--- a/gzip.c
+++ b/gzip.c
@@ -1696,6 +1696,21 @@ local int check_ofname()
return OK;
}
+/* Change the owner and group of a file. FD is a file descriptor for
+ the file and NAME its name. Change it to user UID and to group GID.
+ If UID or GID is -1, though, do not change the corresponding user
+ or group. */
+static void
+do_chown (int fd, char const *name, uid_t uid, gid_t gid)
+{
+#ifndef NO_CHOWN
+# if HAVE_FCHOWN
+ ignore_value (fchown (fd, uid, gid));
+# else
+ ignore_value (chown (name, uid, gid));
+# endif
+#endif
+}
/* ========================================================================
* Copy modes, times, ownership from input file to output file.
@@ -1734,16 +1749,14 @@ local void copy_stat(ifstat)
}
#endif
-#ifndef NO_CHOWN
- /* Copy ownership */
-# if HAVE_FCHOWN
- ignore_value (fchown (ofd, ifstat->st_uid, ifstat->st_gid));
-# elif HAVE_CHOWN
- ignore_value (chown (ofname, ifstat->st_uid, ifstat->st_gid));
-# endif
-#endif
+ /* Change the group first, then the permissions, then the owner.
+ That way, the permissions will be correct on systems that allow
+ users to give away files, without introducing a security hole.
+ Security depends on permissions not containing the setuid or
+ setgid bits. */
+
+ do_chown (ofd, ofname, -1, ifstat->st_gid);
- /* Copy the protection modes */
#if HAVE_FCHMOD
r = fchmod (ofd, mode);
#else
@@ -1757,6 +1770,8 @@ local void copy_stat(ifstat)
perror(ofname);
}
}
+
+ do_chown (ofd, ofname, ifstat->st_uid, -1);
}
#if ! NO_DIR
--
1.8.3.1