linux/security
Catherine Zhang 877ce7c1b3 [AF_UNIX]: Datagram getpeersec
This patch implements an API whereby an application can determine the
label of its peer's Unix datagram sockets via the auxiliary data mechanism of
recvmsg.

Patch purpose:

This patch enables a security-aware application to retrieve the
security context of the peer of a Unix datagram socket.  The application
can then use this security context to determine the security context for
processing on behalf of the peer who sent the packet.

Patch design and implementation:

The design and implementation is very similar to the UDP case for INET
sockets.  Basically we build upon the existing Unix domain socket API for
retrieving user credentials.  Linux offers the API for obtaining user
credentials via ancillary messages (i.e., out of band/control messages
that are bundled together with a normal message).  To retrieve the security
context, the application first indicates to the kernel such desire by
setting the SO_PASSSEC option via getsockopt.  Then the application
retrieves the security context using the auxiliary data mechanism.

An example server application for Unix datagram socket should look like this:

toggle = 1;
toggle_len = sizeof(toggle);

setsockopt(sockfd, SOL_SOCKET, SO_PASSSEC, &toggle, &toggle_len);
recvmsg(sockfd, &msg_hdr, 0);
if (msg_hdr.msg_controllen > sizeof(struct cmsghdr)) {
    cmsg_hdr = CMSG_FIRSTHDR(&msg_hdr);
    if (cmsg_hdr->cmsg_len <= CMSG_LEN(sizeof(scontext)) &&
        cmsg_hdr->cmsg_level == SOL_SOCKET &&
        cmsg_hdr->cmsg_type == SCM_SECURITY) {
        memcpy(&scontext, CMSG_DATA(cmsg_hdr), sizeof(scontext));
    }
}

sock_setsockopt is enhanced with a new socket option SOCK_PASSSEC to allow
a server socket to receive security context of the peer.

Testing:

We have tested the patch by setting up Unix datagram client and server
applications.  We verified that the server can retrieve the security context
using the auxiliary data mechanism of recvmsg.

Signed-off-by: Catherine Zhang <cxzhang@watson.ibm.com>
Acked-by: Acked-by: James Morris <jmorris@namei.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2006-06-29 16:58:06 -07:00
..
keys [PATCH] Keys: Allow in-kernel key requestor to pass auxiliary data to upcaller 2006-06-29 10:26:20 -07:00
selinux [AF_UNIX]: Datagram getpeersec 2006-06-29 16:58:06 -07:00
capability.c kbuild: un-stringnify KBUILD_MODNAME 2006-01-06 21:17:50 +01:00
commoncap.c [NETLINK]: Encapsulate eff_cap usage within security framework. 2006-06-29 16:57:55 -07:00
dummy.c [NETLINK]: Encapsulate eff_cap usage within security framework. 2006-06-29 16:57:55 -07:00
inode.c Merge branch 'master' of /home/trondmy/kernel/linux-2.6/ 2006-06-24 13:07:53 -04:00
Kconfig [PATCH] keys: restrict contents of /proc/keys to Viewable keys 2006-06-26 09:58:18 -07:00
Makefile [PATCH] add securityfs for all LSMs to use 2005-07-08 18:48:41 -07:00
root_plug.c Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
seclvl.c [PATCH] Bug fixes and cleanup for the BSD Secure Levels LSM 2006-03-23 07:38:03 -08:00
security.c [PATCH] refactor capable() to one implementation, add __capable() helper 2006-03-25 08:22:56 -08:00