• Trent Jaeger's avatar
    [LSM-IPSec]: Security association restriction. · df71837d
    Trent Jaeger authored
    This patch series implements per packet access control via the
    extension of the Linux Security Modules (LSM) interface by hooks in
    the XFRM and pfkey subsystems that leverage IPSec security
    associations to label packets.  Extensions to the SELinux LSM are
    included that leverage the patch for this purpose.
    
    This patch implements the changes necessary to the XFRM subsystem,
    pfkey interface, ipv4/ipv6, and xfrm_user interface to restrict a
    socket to use only authorized security associations (or no security
    association) to send/receive network packets.
    
    Patch purpose:
    
    The patch is designed to enable access control per packets based on
    the strongly authenticated IPSec security association.  Such access
    controls augment the existing ones based on network interface and IP
    address.  The former are very coarse-grained, and the latter can be
    spoofed.  By using IPSec, the system can control access to remote
    hosts based on cryptographic keys generated using the IPSec mechanism.
    This enables access control on a per-machine basis or per-application
    if the remote machine is running the same mechanism and trusted to
    enforce the access control policy.
    
    Patch design approach:
    
    The overall approach is that policy (xfrm_policy) entries set by
    user-level programs (e.g., setkey for ipsec-tools) are extended with a
    security context that is used at policy selection time in the XFRM
    subsystem to restrict the sockets that can send/receive packets via
    security associations (xfrm_states) that are built from those
    policies.
    
    A presentation available at
    www.selinux-symposium.org/2005/presentations/session2/2-3-jaeger.pdf
    from the SELinux symposium describes the overall approach.
    
    Patch implementation details:
    
    On output, the policy retrieved (via xfrm_policy_lookup or
    xfrm_sk_policy_lookup) must be authorized for the security context of
    the socket and the same security context is required for resultant
    security association (retrieved or negotiated via racoon in
    ipsec-tools).  This is enforced in xfrm_state_find.
    
    On input, the policy retrieved must also be authorized for the socket
    (at __xfrm_policy_check), and the security context of the policy must
    also match the security association being used.
    
    The patch has virtually no impact on packets that do not use IPSec.
    The existing Netfilter (outgoing) and LSM rcv_skb hooks are used as
    before.
    
    Also, if IPSec is used without security contexts, the impact is
    minimal.  The LSM must allow such policies to be selected for the
    combination of socket and remote machine, but subsequent IPSec
    processing proceeds as in the original case.
    
    Testing:
    
    The pfkey interface is tested using the ipsec-tools.  ipsec-tools have
    been modified (a separate ipsec-tools patch is available for version
    0.5) that supports assignment of xfrm_policy entries and security
    associations with security contexts via setkey and the negotiation
    using the security contexts via racoon.
    
    The xfrm_user interface is tested via ad hoc programs that set
    security contexts.  These programs are also available from me, and
    contain programs for setting, getting, and deleting policy for testing
    this interface.  Testing of sa functions was done by tracing kernel
    behavior.
    Signed-off-by: default avatarTrent Jaeger <tjaeger@cse.psu.edu>
    Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    df71837d
xfrm.h 26 KB