linux/security/selinux
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
..
include [PATCH] SELinux: Add sockcreate node to procattr API 2006-06-26 09:58:26 -07:00
ss [PATCH] fix se_sen audit filter 2006-06-20 05:25:26 -04:00
avc.c [PATCH] support for context based audit filtering 2006-05-01 06:06:24 -04:00
exports.c [SECMARK]: Add SELinux exports 2006-06-17 21:29:55 -07:00
hooks.c [AF_UNIX]: Datagram getpeersec 2006-06-29 16:58:06 -07:00
Kconfig [SECMARK]: Add new packet controls to SELinux 2006-06-17 21:30:05 -07:00
Makefile [PATCH] support for context based audit filtering 2006-05-01 06:06:24 -04:00
netif.c [PATCH] SELinux: convert to kzalloc 2005-10-30 17:37:11 -08:00
netlink.c [NETLINK]: Add "groups" argument to netlink_kernel_create 2005-08-29 16:01:11 -07:00
nlmsgtab.c Merge branch 'audit.b3' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/audit-current 2006-03-25 09:24:53 -08:00
selinuxfs.c [PATCH] VFS: Permit filesystem to override root dentry on mount 2006-06-23 07:42:45 -07:00
xfrm.c [SECMARK]: Add new packet controls to SELinux 2006-06-17 21:30:05 -07:00