netdev - Re: [PATCH] LSM: Add security_socket_post_accept() and security_socket_post_recv

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Message-Id: <200904212126.AJD95821.HFMOFtQJOVFLOS@I-love.SAKURA.ne.jp>
Date:	Tue, 21 Apr 2009 21:26:36 +0900
From:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:	davem@...emloft.net
Cc:	paul.moore@...com, linux-security-module@...r.kernel.org,
	netdev@...r.kernel.org
Subject: Re: [PATCH] LSM: Add security_socket_post_accept() and security_socket_post_recv_datagram().

David Miller wrote:
> I am saying that you shouldn't be dropping connections like
> this.
Please don't assume that we are talking about labeled networking.
I want to implement TCPwrapper-like filtering (which is automatically linked to
all processes).

> You've already accepted the packet, you cannot reneg on this.
TCPwrapper accepts the packet before it decides to drop the connection.

> You must either allow the socket to have the connection with
> current labels or give it a label appropriate for the socket.
The socket_post_accept() hook is not designed for modifying labels of a socket.
It is too late to modify because we have already accepted the packet.

+ * @socket_post_accept:
+ *	This hook allows a security module to filter connections from unwanted
+ *	peers based on the process accepting this connection.
+ *	The connection will be aborted if this hook returns nonzero.
+ *	This hook is not designed for updating security attributes of
+ *	an accept()ed socket, for the accept()ed socket has already sent
+ *	several packets (e.g. TCP's SYN/ACK packet and some ACK packets for
+ *	incoming data) before this hook is called.
+ *	@sock contains the listening socket structure.
+ *	@newsock contains the newly created server socket for connection.
+ *	Return 0 if permission is granted.
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