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

[Ian Kent]

From: Ian Kent <ikent@xxxxxxxxxx>

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@xxxxxxxxxx>
Cc: Benjamin Coddington <bcodding@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: J. Bruce Fields <bfields@xxxxxxxxxxxx>
Cc: David Howells <dhowells@xxxxxxxxxx>
Cc: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
Cc: Oleg Nesterov <onestero@xxxxxxxxxx>
Cc: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
Cc: Jeff Layton <jeff.layton@xxxxxxxxxxxxxxx>
---
 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 */

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