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Date: Sat, 21 Jul 2007 00:11:04 +0900
From: Tetsuo Handa <from-netdev@...ove.SAKURA.ne.jp>
To: jmorris@...ei.org, shemminger@...ux-foundation.org
Cc: netdev@...r.kernel.org, linux-security-module@...r.kernel.org
Subject: [PATCH 1/1] Allow LSM to use IP address/port number.
Hello.
> > Isn't it better to hook into existing netfilter infrastructure somehow?
> Yes, it has been suggested several times.
I want to use a process's context who issued
accept()/recv()/recvfrom()/recvmsg()/read() requests.
But Stephen Smalley said at http://marc.info/?l=linux-security-module&m=118459899017487&w=2 that
> The socket can be inherited by a child task or passed via local IPC to
> an unrelated task, and then used by those other tasks. It isn't tied to
> the original allocating task's lifecycle in any way, nor is it
> guaranteed to only be used by that original allocating task. It can
> exist in zero, one or many tasks' file tables and still be receiving
> data, and can go from completely disassociated (i.e. not present in any
> tasks' file tables) to being associated.
I can't use netfilter infrastructure because
it is too early to know who the recipant process of the packet is.
The only chance to perform ip/port based filtering
using ACLs associated with the recipant process of the packet
is post-accept() and post-recvmsg().
Therefore, I re-post my patch again.
Regards.
Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
---
include/linux/security.h | 44 +++++++++++++++++++++++++++++++++++++-------
net/socket.c | 42 ++++++++++++++++++++++++++++++++++++------
security/dummy.c | 13 ++++++++++---
3 files changed, 83 insertions(+), 16 deletions(-)
diff -upr a/include/linux/security.h b/include/linux/security.h
--- a/include/linux/security.h 2007-07-20 22:55:38.000000000 +0900
+++ b/include/linux/security.h 2007-07-20 23:15:58.000000000 +0900
@@ -749,8 +749,12 @@ struct request_sock;
* @socket_post_accept:
* This hook allows a security module to copy security
* information into the newly created socket's inode.
+ * This hook also allows a security module to filter connections
+ * from unwanted peers.
+ * The connection will be aborted if this hook returns nonzero.
* @sock contains the listening socket structure.
* @newsock contains the newly created server socket for connection.
+ * Return 0 if permission is granted.
* @socket_sendmsg:
* Check permission before transmitting a message to another socket.
* @sock contains the socket structure.
@@ -764,6 +768,15 @@ struct request_sock;
* @size contains the size of message structure.
* @flags contains the operational flags.
* Return 0 if permission is granted.
+ * @socket_post_recvmsg:
+ * Check peer's address after receiving a message from a socket.
+ * This hook allows a security module to filter messages
+ * from unwanted peers.
+ * @sock contains the socket structure.
+ * @msg contains the message structure.
+ * @size contains the size of message structure.
+ * @flags contains the operational flags.
+ * Return 0 if permission is granted.
* @socket_getsockname:
* Check permission before the local address (name) of the socket object
* @sock is retrieved.
@@ -1345,12 +1358,14 @@ struct security_operations {
struct sockaddr * address, int addrlen);
int (*socket_listen) (struct socket * sock, int backlog);
int (*socket_accept) (struct socket * sock, struct socket * newsock);
- void (*socket_post_accept) (struct socket * sock,
- struct socket * newsock);
+ int (*socket_post_accept) (struct socket *sock,
+ struct socket *newsock);
int (*socket_sendmsg) (struct socket * sock,
struct msghdr * msg, int size);
int (*socket_recvmsg) (struct socket * sock,
struct msghdr * msg, int size, int flags);
+ int (*socket_post_recvmsg) (struct socket *sock, struct msghdr *msg,
+ int size, int flags);
int (*socket_getsockname) (struct socket * sock);
int (*socket_getpeername) (struct socket * sock);
int (*socket_getsockopt) (struct socket * sock, int level, int optname);
@@ -2860,10 +2875,10 @@ static inline int security_socket_accept
return security_ops->socket_accept(sock, newsock);
}
-static inline void security_socket_post_accept(struct socket * sock,
- struct socket * newsock)
+static inline int security_socket_post_accept(struct socket *sock,
+ struct socket *newsock)
{
- security_ops->socket_post_accept(sock, newsock);
+ return security_ops->socket_post_accept(sock, newsock);
}
static inline int security_socket_sendmsg(struct socket * sock,
@@ -2879,6 +2894,13 @@ static inline int security_socket_recvms
return security_ops->socket_recvmsg(sock, msg, size, flags);
}
+static inline int security_socket_post_recvmsg(struct socket *sock,
+ struct msghdr *msg,
+ int size, int flags)
+{
+ return security_ops->socket_post_recvmsg(sock, msg, size, flags);
+}
+
static inline int security_socket_getsockname(struct socket * sock)
{
return security_ops->socket_getsockname(sock);
@@ -3023,9 +3045,10 @@ static inline int security_socket_accept
return 0;
}
-static inline void security_socket_post_accept(struct socket * sock,
- struct socket * newsock)
+static inline int security_socket_post_accept(struct socket *sock,
+ struct socket *newsock)
{
+ return 0;
}
static inline int security_socket_sendmsg(struct socket * sock,
@@ -3041,6 +3064,13 @@ static inline int security_socket_recvms
return 0;
}
+static inline int security_socket_post_recvmsg(struct socket *sock,
+ struct msghdr *msg,
+ int size, int flags)
+{
+ return 0;
+}
+
static inline int security_socket_getsockname(struct socket * sock)
{
return 0;
diff -upr a/net/socket.c b/net/socket.c
--- a/net/socket.c 2007-07-20 22:55:53.000000000 +0900
+++ b/net/socket.c 2007-07-21 00:05:18.000000000 +0900
@@ -635,7 +635,19 @@ static inline int __sock_recvmsg(struct
if (err)
return err;
- return sock->ops->recvmsg(iocb, sock, msg, size, flags);
+ err = sock->ops->recvmsg(iocb, sock, msg, size, flags);
+ /*
+ * Filter messages from unwanted peers.
+ * To be exact, this hook can't filter messages,
+ * this hook just returns an error code.
+ */
+ if (err >= 0) {
+ int ret;
+ ret = security_socket_post_recvmsg(sock, msg, size, flags);
+ if (ret)
+ err = ret;
+ }
+ return err;
}
int sock_recvmsg(struct socket *sock, struct msghdr *msg,
@@ -648,8 +660,17 @@ int sock_recvmsg(struct socket *sock, st
init_sync_kiocb(&iocb, NULL);
iocb.private = &siocb;
ret = __sock_recvmsg(&iocb, sock, msg, size, flags);
- if (-EIOCBQUEUED == ret)
+ if (-EIOCBQUEUED == ret) {
ret = wait_on_sync_kiocb(&iocb);
+ /* I can now check security_socket_post_recvmsg(). */
+ if (ret >= 0) {
+ int err;
+ err = security_socket_post_recvmsg(sock, msg, size,
+ flags);
+ if (err)
+ ret = err;
+ }
+ }
return ret;
}
@@ -712,12 +733,14 @@ static ssize_t do_sock_read(struct msghd
struct socket *sock = file->private_data;
size_t size = 0;
int i;
+ /* only for security_socket_post_recvmsg() */
+ char address[MAX_SOCK_ADDR];
for (i = 0; i < nr_segs; i++)
size += iov[i].iov_len;
- msg->msg_name = NULL;
- msg->msg_namelen = 0;
+ msg->msg_name = address;
+ msg->msg_namelen = sizeof(address);
msg->msg_control = NULL;
msg->msg_controllen = 0;
msg->msg_iov = (struct iovec *)iov;
@@ -1437,13 +1460,16 @@ asmlinkage long sys_accept(int fd, struc
goto out_fd;
}
+ /* Filter connections from unwanted peers like TCP Wrapper. */
+ err = security_socket_post_accept(sock, newsock);
+ if (err)
+ goto out_fd;
+
/* File flags are not inherited via accept() unlike another OSes. */
fd_install(newfd, newfile);
err = newfd;
- security_socket_post_accept(sock, newsock);
-
out_put:
fput_light(sock->file, fput_needed);
out:
@@ -1937,6 +1963,10 @@ asmlinkage long sys_recvmsg(int fd, stru
goto out_freeiov;
total_len = err;
+ /* only for security_socket_post_recvmsg() */
+ msg_sys.msg_name = addr;
+ msg_sys.msg_namelen = sizeof(addr);
+
cmsg_ptr = (unsigned long)msg_sys.msg_control;
msg_sys.msg_flags = flags & (MSG_CMSG_CLOEXEC|MSG_CMSG_COMPAT);
diff -upr a/security/dummy.c b/security/dummy.c
--- a/security/dummy.c 2007-07-20 22:55:54.000000000 +0900
+++ b/security/dummy.c 2007-07-20 23:15:22.000000000 +0900
@@ -741,10 +741,10 @@ static int dummy_socket_accept (struct s
return 0;
}
-static void dummy_socket_post_accept (struct socket *sock,
- struct socket *newsock)
+static int dummy_socket_post_accept(struct socket *sock,
+ struct socket *newsock)
{
- return;
+ return 0;
}
static int dummy_socket_sendmsg (struct socket *sock, struct msghdr *msg,
@@ -759,6 +759,12 @@ static int dummy_socket_recvmsg (struct
return 0;
}
+static int dummy_socket_post_recvmsg(struct socket *sock, struct msghdr *msg,
+ int size, int flags)
+{
+ return 0;
+}
+
static int dummy_socket_getsockname (struct socket *sock)
{
return 0;
@@ -1096,6 +1102,7 @@ void security_fixup_ops (struct security
set_to_dummy_if_null(ops, socket_post_accept);
set_to_dummy_if_null(ops, socket_sendmsg);
set_to_dummy_if_null(ops, socket_recvmsg);
+ set_to_dummy_if_null(ops, socket_post_recvmsg);
set_to_dummy_if_null(ops, socket_getsockname);
set_to_dummy_if_null(ops, socket_getpeername);
set_to_dummy_if_null(ops, socket_setsockopt);
-
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