[RFC PATCH v4 12/12] KEYS: exec request-key within the requesting task's init namespace

Ian Kent
2015-03-17T02:46:32Z

Containerized request key helper callbacks need the ability to execute
a binary in a container's context. To do this calling an in kernel
equivalent of setns(2) should be sufficient since the user mode helper
execution kernel thread ultimately calls do_execve().

Signed-off-by: Ian Kent <ikent@redhat.com>
Cc: Benjamin Coddington <bcodding@redhat.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: J. Bruce Fields <bfields@fieldses.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Trond Myklebust <trond.myklebust@primarydata.com>
Cc: Oleg Nesterov <onestero@redhat.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Jeff Layton <jeff.layton@primarydata.com>
---
include/linux/key.h | 3 +++
security/keys/gc.c | 2 ++
security/keys/key.c | 4 ++++
security/keys/request_key.c | 35 +++++++++++++++++++++++++++++++++--
4 files changed, 42 insertions(+), 2 deletions(-)

diff --git a/include/linux/key.h b/include/linux/key.h
index e1d4715..89dc2d7 100644
--- a/include/linux/key.h
+++ b/include/linux/key.h
@@ -209,6 +209,9 @@ struct key {
} payload;
struct assoc_array keys;
};
+
+ /* Namespace token */
+ long umh_token;
};

extern struct key *key_alloc(struct key_type *type,
diff --git a/security/keys/gc.c b/security/keys/gc.c
index c795237..57a0730 100644
--- a/security/keys/gc.c
+++ b/security/keys/gc.c
@@ -156,6 +156,8 @@ static noinline void key_gc_unused_keys(struct list_head *keys)

kfree(key->description);

+ umh_ns_put_token(key->umh_token);
+
#ifdef KEY_DEBUGGING
key->magic = KEY_DEBUG_MAGIC_X;
#endif
diff --git a/security/keys/key.c b/security/keys/key.c
index aee2ec5..e7ab89d 100644
--- a/security/keys/key.c
+++ b/security/keys/key.c
@@ -18,6 +18,7 @@
#include <linux/workqueue.h>
#include <linux/random.h>
#include <linux/err.h>
+#include <net/net_namespace.h>
#include "internal.h"

struct kmem_cache *key_jar;
@@ -309,6 +310,9 @@ struct key *key_alloc(struct key_type *type, const char *desc,
/* publish the key by giving it a serial number */
atomic_inc(&user->nkeys);
key_alloc_serial(key);
+ /* If running within a container use the container namespace */
+ if (current->nsproxy->net_ns != &init_net)
+ key->umh_token = umh_ns_get_token(0);

error:
return key;
diff --git a/security/keys/request_key.c b/security/keys/request_key.c
index e865f9f..16ac3b0 100644
--- a/security/keys/request_key.c
+++ b/security/keys/request_key.c
@@ -90,6 +90,31 @@ static int call_usermodehelper_keys(char *path, char **argv, char **envp,
}

/*
+ * Call a usermode helper with a specific session keyring and execute
+ * within a namespace.
+ */
+static int call_usermodehelper_keys_ns(char *path, char **argv, char **envp,
+ struct key *session_keyring,
+ unsigned int wait, long token)
+{
+ struct subprocess_info *info;
+ unsigned int gfp_mask = (wait & UMH_NO_WAIT) ?
+ GFP_ATOMIC : GFP_KERNEL;
+
+ if (token <= 0)
+ return -EINVAL;
+
+ info = call_usermodehelper_setup_ns(path, argv, envp, gfp_mask,
+ umh_keys_init, umh_keys_cleanup,
+ session_keyring, token);
+ if (!info)
+ return -ENOMEM;
+
+ key_get(session_keyring);
+ return call_usermodehelper_exec(info, wait|UMH_USE_NS);
+}
+
+/*
* Request userspace finish the construction of a key
* - execute "/sbin/request-key <op> <key> <uid> <gid> <keyring> <keyring> <keyring>"
*/
@@ -104,6 +129,7 @@ static int call_sbin_request_key(struct key_construction *cons,
char *argv[9], *envp[3], uid_str[12], gid_str[12];
char key_str[12], keyring_str[3][12];
char desc[20];
+ unsigned int wait = UMH_WAIT_PROC;
int ret, i;

kenter("{%d},{%d},%s", key->serial, authkey->serial, op);
@@ -174,8 +200,13 @@ static int call_sbin_request_key(struct key_construction *cons,
argv[i] = NULL;

/* do it */
- ret = call_usermodehelper_keys(argv[0], argv, envp, keyring,
- UMH_WAIT_PROC);
+ /* If running within a container use the container namespace */
+ if (key->umh_token)
+ ret = call_usermodehelper_keys_ns(argv[0], argv, envp,
+ keyring, wait, key->umh_token);
+ else
+ ret = call_usermodehelper_keys(argv[0],
+ argv, envp, keyring, wait);
kdebug("usermode -> 0x%x", ret);
if (ret >= 0) {
/* ret is the exit/wait code */