Re: [PATCH] Add audit uid to netlink credentials
* Chris Wright (chrisw(a)osdl.org) wrote:
Hmm, perhaps we could eliminate the whole asynchronous issue by
allowing
registration of a netlink link specific security handler. Something like:
netlink_kernel_create_sec(unit, rx, sec_handler)
Then the check would be done before the packet was ever queued. This
would eliminate the if (NETLINK_CREDS(skb)->$cred == bad) on receipt
side, and push it to sender side. It would also be link specific so
audit could do it's audit payload loginuid check here. I think it would
also eliminate SELinux's need to tag the packet for later checking on
receipt. Thoughts?
Here's an example of what I mean. It's quite rough, doesn't yet eliminate
any of the code that it eventually could, and doesn't deal with broadcast.
I gave it a quick test with audit netlink, and it does what I expect.
thanks,
-chris
--
Linux Security Modules http://lsm.immunix.org http://lsm.bkbits.net
===== kernel/audit.c 1.9 vs edited =====
--- 1.9/kernel/audit.c 2005-01-30 22:33:47 -08:00
+++ edited/kernel/audit.c 2005-02-09 17:07:22 -08:00
@@ -333,6 +333,15 @@ static int audit_netlink_ok(kernel_cap_t
return err;
}
+static int audit_check_sender(struct sk_buff *skb)
+{
+ struct nlmsghdr *nlh = (struct nlmsghdr *)skb->data;
+ u16 msg_type = nlh->nlmsg_type;
+
+ return audit_netlink_ok(NETLINK_CB(skb).eff_cap, msg_type);
+
+}
+
static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
{
u32 uid, pid, seq;
@@ -551,7 +560,7 @@ int __init audit_init(void)
{
printk(KERN_INFO "audit: initializing netlink socket (%s)\n",
audit_default ? "enabled" : "disabled");
- audit_sock = netlink_kernel_create(NETLINK_AUDIT, audit_receive);
+ audit_sock = netlink_kernel_create_check(NETLINK_AUDIT, audit_receive,
audit_check_sender);
if (!audit_sock)
audit_panic("cannot initialize netlink socket");
===== net/netlink/af_netlink.c 1.69 vs edited =====
--- 1.69/net/netlink/af_netlink.c 2005-01-21 12:25:32 -08:00
+++ edited/net/netlink/af_netlink.c 2005-02-09 16:39:15 -08:00
@@ -71,6 +71,7 @@ struct netlink_opt
struct netlink_callback *cb;
spinlock_t cb_lock;
void (*data_ready)(struct sock *sk, int bytes);
+ int (*send_check)(struct sk_buff *skb);
};
#define nlk_sk(__sk) ((struct netlink_opt *)(__sk)->sk_protinfo)
@@ -639,6 +640,14 @@ int netlink_sendskb(struct sock *sk, str
int len = skb->len;
nlk = nlk_sk(sk);
+
+ if (nlk->send_check)
+ if (nlk->send_check(skb)) {
+ kfree_skb(skb);
+ sock_put(sk);
+ return -EPERM;
+ }
+
#ifdef NL_EMULATE_DEV
if (nlk->handler) {
skb_orphan(skb);
@@ -1033,7 +1042,8 @@ static void netlink_data_ready(struct so
*/
struct sock *
-netlink_kernel_create(int unit, void (*input)(struct sock *sk, int len))
+netlink_kernel_create_check(int unit, void (*input)(struct sock *sk, int len),
+ int (*check)(struct sk_buff *skb))
{
struct socket *sock;
struct sock *sk;
@@ -1053,8 +1063,10 @@ netlink_kernel_create(int unit, void (*i
}
sk = sock->sk;
sk->sk_data_ready = netlink_data_ready;
- if (input)
+ if (input) {
nlk_sk(sk)->data_ready = input;
+ nlk_sk(sk)->send_check = check;
+ }
if (netlink_insert(sk, 0)) {
sock_release(sock);
@@ -1459,7 +1471,7 @@ MODULE_ALIAS_NETPROTO(PF_NETLINK);
EXPORT_SYMBOL(netlink_ack);
EXPORT_SYMBOL(netlink_broadcast);
EXPORT_SYMBOL(netlink_dump_start);
-EXPORT_SYMBOL(netlink_kernel_create);
+EXPORT_SYMBOL(netlink_kernel_create_check);
EXPORT_SYMBOL(netlink_register_notifier);
EXPORT_SYMBOL(netlink_set_err);
EXPORT_SYMBOL(netlink_set_nonroot);
===== include/linux/netlink.h 1.23 vs edited =====
--- 1.23/include/linux/netlink.h 2005-02-06 21:59:39 -08:00
+++ edited/include/linux/netlink.h 2005-02-09 16:36:45 -08:00
@@ -116,7 +116,11 @@ struct netlink_skb_parms
#define NETLINK_CREDS(skb) (&NETLINK_CB((skb)).creds)
-extern struct sock *netlink_kernel_create(int unit, void (*input)(struct sock *sk, int
len));
+extern struct sock *netlink_kernel_create_check(int unit, void (*input)(struct sock *sk,
int len), int (*check)(struct sk_buff *skb));
+static inline struct sock *netlink_kernel_create(int unit, void (*input)(struct sock *sk,
int len))
+{
+ return netlink_kernel_create_check(unit, input, NULL);
+}
extern void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err);
extern int netlink_unicast(struct sock *ssk, struct sk_buff *skb, __u32 pid, int
nonblock);
extern int netlink_broadcast(struct sock *ssk, struct sk_buff *skb, __u32 pid,