linux-kernel - [PATCH 2/3] p9auth: add CAP_GRANT_ID to authorize use of /dev/caphash

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Message-ID: <20100421012815.GA24251@us.ibm.com>
Date:	Tue, 20 Apr 2010 20:28:15 -0500
From:	"Serge E. Hallyn" <serue@...ibm.com>
To:	lkml <linux-kernel@...r.kernel.org>
Cc:	David Howells <dhowells@...hat.com>,
	Ashwin Ganti <ashwin.ganti@...il.com>,
	Greg KH <greg@...ah.com>, rsc@...ch.com, ericvh@...il.com,
	linux-security-module@...r.kernel.org,
	Ron Minnich <rminnich@...il.com>, jt.beard@...il.com,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andrew Morgan <morgan@...nel.org>, oleg@...ibm.com,
	Eric Paris <eparis@...hat.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: [PATCH 2/3] p9auth: add CAP_GRANT_ID to authorize use of
 /dev/caphash


Granting userid capabilities to another task is a dangerous
privilege.  Don't just let file permissions authorize it.
Define CAP_GRANT_ID as a new capability needed to write to
/dev/caphash.

For one thing this lets us start a factotum server early on
in init, then have init drop CAP_GRANT_ID from its bounding
set so the rest of the system cannot regain it.

Signed-off-by: Serge E. Hallyn <serue@...ibm.com>
---
 include/linux/capability.h          |    6 +++++-
 security/selinux/include/classmap.h |    2 +-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/include/linux/capability.h b/include/linux/capability.h
index 39e5ff5..ba2cbfe 100644
--- a/include/linux/capability.h
+++ b/include/linux/capability.h
@@ -355,7 +355,11 @@ struct cpu_vfs_cap_data {
 
 #define CAP_MAC_ADMIN        33
 
-#define CAP_LAST_CAP         CAP_MAC_ADMIN
+/* Allow granting setuid capabilities through p9auth /dev/caphash */
+
+#define CAP_GRANT_ID         34
+
+#define CAP_LAST_CAP         CAP_GRANT_ID
 
 #define cap_valid(x) ((x) >= 0 && (x) <= CAP_LAST_CAP)
 
diff --git a/security/selinux/include/classmap.h b/security/selinux/include/classmap.h
index 8b32e95..f0ec53a 100644
--- a/security/selinux/include/classmap.h
+++ b/security/selinux/include/classmap.h
@@ -142,7 +142,7 @@ struct security_class_mapping secclass_map[] = {
 	    "node_bind", "name_connect", NULL } },
 	{ "memprotect", { "mmap_zero", NULL } },
 	{ "peer", { "recv", NULL } },
-	{ "capability2", { "mac_override", "mac_admin", NULL } },
+	{ "capability2", { "mac_override", "mac_admin", "grant_id", NULL } },
 	{ "kernel_service", { "use_as_override", "create_files_as", NULL } },
 	{ "tun_socket",
 	  { COMMON_SOCK_PERMS, NULL } },
-- 
1.7.0.4

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