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From: Serge E. Hallyn on 27 Apr 2010 16:50
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.

(This patch is only useful if the next patch, introducing p9auth fs, is
upstreamed)

TODO - patch for capabilities.7 manpage

Signed-off-by: Serge E. Hallyn <serue(a)us.ibm.com>
Cc: Michael Kerrisk <mtk.manpages(a)gmail.com>
Cc: Andrew Morgan <morgan(a)kernel.org>
Cc: James Morris <jmorris(a)namei.org>
Cc: linux-security-module(a)vger.kernel.org
---
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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