545 lines
11 KiB
C
545 lines
11 KiB
C
/*
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* NSA Security-Enhanced Linux (SELinux) security module
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*
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* This file contains the SELinux XFRM hook function implementations.
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*
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* Authors: Serge Hallyn <sergeh@us.ibm.com>
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* Trent Jaeger <jaegert@us.ibm.com>
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*
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* Updated: Venkat Yekkirala <vyekkirala@TrustedCS.com>
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*
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* Granular IPSec Associations for use in MLS environments.
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*
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* Copyright (C) 2005 International Business Machines Corporation
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* Copyright (C) 2006 Trusted Computer Solutions, Inc.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2,
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* as published by the Free Software Foundation.
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*/
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/*
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* USAGE:
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* NOTES:
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* 1. Make sure to enable the following options in your kernel config:
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* CONFIG_SECURITY=y
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* CONFIG_SECURITY_NETWORK=y
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* CONFIG_SECURITY_NETWORK_XFRM=y
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* CONFIG_SECURITY_SELINUX=m/y
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* ISSUES:
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* 1. Caching packets, so they are not dropped during negotiation
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* 2. Emulating a reasonable SO_PEERSEC across machines
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* 3. Testing addition of sk_policy's with security context via setsockopt
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*/
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#include <linux/module.h>
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#include <linux/kernel.h>
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#include <linux/init.h>
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#include <linux/security.h>
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#include <linux/types.h>
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#include <linux/netfilter.h>
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#include <linux/netfilter_ipv4.h>
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#include <linux/netfilter_ipv6.h>
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#include <linux/ip.h>
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#include <linux/tcp.h>
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#include <linux/skbuff.h>
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#include <linux/xfrm.h>
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#include <net/xfrm.h>
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#include <net/checksum.h>
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#include <net/udp.h>
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#include <asm/semaphore.h>
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#include "avc.h"
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#include "objsec.h"
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#include "xfrm.h"
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/*
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* Returns true if an LSM/SELinux context
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*/
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static inline int selinux_authorizable_ctx(struct xfrm_sec_ctx *ctx)
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{
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return (ctx &&
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(ctx->ctx_doi == XFRM_SC_DOI_LSM) &&
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(ctx->ctx_alg == XFRM_SC_ALG_SELINUX));
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}
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/*
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* Returns true if the xfrm contains a security blob for SELinux
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*/
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static inline int selinux_authorizable_xfrm(struct xfrm_state *x)
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{
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return selinux_authorizable_ctx(x->security);
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}
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/*
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* LSM hook implementation that authorizes that a flow can use
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* a xfrm policy rule.
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*/
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int selinux_xfrm_policy_lookup(struct xfrm_policy *xp, u32 fl_secid, u8 dir)
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{
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int rc = 0;
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u32 sel_sid = SECINITSID_UNLABELED;
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struct xfrm_sec_ctx *ctx;
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/* Context sid is either set to label or ANY_ASSOC */
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if ((ctx = xp->security)) {
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if (!selinux_authorizable_ctx(ctx))
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return -EINVAL;
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sel_sid = ctx->ctx_sid;
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}
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rc = avc_has_perm(fl_secid, sel_sid, SECCLASS_ASSOCIATION,
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ASSOCIATION__POLMATCH,
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NULL);
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return rc;
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}
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/*
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* LSM hook implementation that authorizes that a state matches
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* the given policy, flow combo.
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*/
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int selinux_xfrm_state_pol_flow_match(struct xfrm_state *x, struct xfrm_policy *xp,
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struct flowi *fl)
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{
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u32 state_sid;
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u32 pol_sid;
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int err;
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if (x->security)
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state_sid = x->security->ctx_sid;
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else
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state_sid = SECINITSID_UNLABELED;
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if (xp->security)
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pol_sid = xp->security->ctx_sid;
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else
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pol_sid = SECINITSID_UNLABELED;
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err = avc_has_perm(state_sid, pol_sid, SECCLASS_ASSOCIATION,
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ASSOCIATION__POLMATCH,
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NULL);
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if (err)
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return 0;
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return selinux_xfrm_flow_state_match(fl, x);
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}
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/*
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* LSM hook implementation that authorizes that a particular outgoing flow
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* can use a given security association.
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*/
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int selinux_xfrm_flow_state_match(struct flowi *fl, struct xfrm_state *xfrm)
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{
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int rc = 0;
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u32 sel_sid = SECINITSID_UNLABELED;
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struct xfrm_sec_ctx *ctx;
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/* Context sid is either set to label or ANY_ASSOC */
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if ((ctx = xfrm->security)) {
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if (!selinux_authorizable_ctx(ctx))
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return 0;
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sel_sid = ctx->ctx_sid;
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}
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rc = avc_has_perm(fl->secid, sel_sid, SECCLASS_ASSOCIATION,
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ASSOCIATION__SENDTO,
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NULL)? 0:1;
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return rc;
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}
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/*
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* LSM hook implementation that determines the sid for the session.
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*/
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int selinux_xfrm_decode_session(struct sk_buff *skb, u32 *sid, int ckall)
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{
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struct sec_path *sp;
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*sid = SECSID_NULL;
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if (skb == NULL)
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return 0;
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sp = skb->sp;
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if (sp) {
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int i, sid_set = 0;
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for (i = sp->len-1; i >= 0; i--) {
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struct xfrm_state *x = sp->xvec[i];
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if (selinux_authorizable_xfrm(x)) {
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struct xfrm_sec_ctx *ctx = x->security;
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if (!sid_set) {
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*sid = ctx->ctx_sid;
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sid_set = 1;
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if (!ckall)
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break;
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}
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else if (*sid != ctx->ctx_sid)
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return -EINVAL;
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}
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}
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}
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return 0;
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}
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/*
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* Security blob allocation for xfrm_policy and xfrm_state
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* CTX does not have a meaningful value on input
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*/
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static int selinux_xfrm_sec_ctx_alloc(struct xfrm_sec_ctx **ctxp,
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struct xfrm_user_sec_ctx *uctx, struct xfrm_sec_ctx *pol, u32 sid)
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{
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int rc = 0;
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struct task_security_struct *tsec = current->security;
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struct xfrm_sec_ctx *ctx = NULL;
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char *ctx_str = NULL;
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u32 str_len;
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u32 ctx_sid;
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BUG_ON(uctx && pol);
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if (!uctx)
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goto not_from_user;
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if (uctx->ctx_doi != XFRM_SC_ALG_SELINUX)
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return -EINVAL;
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if (uctx->ctx_len >= PAGE_SIZE)
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return -ENOMEM;
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*ctxp = ctx = kmalloc(sizeof(*ctx) +
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uctx->ctx_len,
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GFP_KERNEL);
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if (!ctx)
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return -ENOMEM;
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ctx->ctx_doi = uctx->ctx_doi;
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ctx->ctx_len = uctx->ctx_len;
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ctx->ctx_alg = uctx->ctx_alg;
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memcpy(ctx->ctx_str,
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uctx+1,
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ctx->ctx_len);
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rc = security_context_to_sid(ctx->ctx_str,
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ctx->ctx_len,
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&ctx->ctx_sid);
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if (rc)
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goto out;
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/*
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* Does the subject have permission to set security context?
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*/
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rc = avc_has_perm(tsec->sid, ctx->ctx_sid,
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SECCLASS_ASSOCIATION,
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ASSOCIATION__SETCONTEXT, NULL);
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if (rc)
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goto out;
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return rc;
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not_from_user:
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if (pol) {
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rc = security_sid_mls_copy(pol->ctx_sid, sid, &ctx_sid);
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if (rc)
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goto out;
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}
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else
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ctx_sid = sid;
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rc = security_sid_to_context(ctx_sid, &ctx_str, &str_len);
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if (rc)
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goto out;
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*ctxp = ctx = kmalloc(sizeof(*ctx) +
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str_len,
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GFP_ATOMIC);
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if (!ctx) {
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rc = -ENOMEM;
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goto out;
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}
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ctx->ctx_doi = XFRM_SC_DOI_LSM;
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ctx->ctx_alg = XFRM_SC_ALG_SELINUX;
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ctx->ctx_sid = ctx_sid;
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ctx->ctx_len = str_len;
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memcpy(ctx->ctx_str,
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ctx_str,
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str_len);
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goto out2;
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out:
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*ctxp = NULL;
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kfree(ctx);
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out2:
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kfree(ctx_str);
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return rc;
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}
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/*
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* LSM hook implementation that allocs and transfers uctx spec to
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* xfrm_policy.
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*/
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int selinux_xfrm_policy_alloc(struct xfrm_policy *xp,
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struct xfrm_user_sec_ctx *uctx, struct sock *sk)
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{
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int err;
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u32 sid;
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BUG_ON(!xp);
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BUG_ON(uctx && sk);
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if (sk) {
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struct sk_security_struct *ssec = sk->sk_security;
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sid = ssec->sid;
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}
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else
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sid = SECSID_NULL;
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err = selinux_xfrm_sec_ctx_alloc(&xp->security, uctx, NULL, sid);
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return err;
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}
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/*
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* LSM hook implementation that copies security data structure from old to
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* new for policy cloning.
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*/
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int selinux_xfrm_policy_clone(struct xfrm_policy *old, struct xfrm_policy *new)
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{
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struct xfrm_sec_ctx *old_ctx, *new_ctx;
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old_ctx = old->security;
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if (old_ctx) {
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new_ctx = new->security = kmalloc(sizeof(*new_ctx) +
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old_ctx->ctx_len,
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GFP_KERNEL);
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if (!new_ctx)
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return -ENOMEM;
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memcpy(new_ctx, old_ctx, sizeof(*new_ctx));
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memcpy(new_ctx->ctx_str, old_ctx->ctx_str, new_ctx->ctx_len);
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}
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return 0;
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}
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/*
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* LSM hook implementation that frees xfrm_policy security information.
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*/
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void selinux_xfrm_policy_free(struct xfrm_policy *xp)
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{
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struct xfrm_sec_ctx *ctx = xp->security;
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if (ctx)
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kfree(ctx);
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}
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/*
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* LSM hook implementation that authorizes deletion of labeled policies.
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*/
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int selinux_xfrm_policy_delete(struct xfrm_policy *xp)
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{
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struct task_security_struct *tsec = current->security;
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struct xfrm_sec_ctx *ctx = xp->security;
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int rc = 0;
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if (ctx)
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rc = avc_has_perm(tsec->sid, ctx->ctx_sid,
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SECCLASS_ASSOCIATION,
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ASSOCIATION__SETCONTEXT, NULL);
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return rc;
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}
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/*
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* LSM hook implementation that allocs and transfers sec_ctx spec to
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* xfrm_state.
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*/
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int selinux_xfrm_state_alloc(struct xfrm_state *x, struct xfrm_user_sec_ctx *uctx,
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struct xfrm_sec_ctx *pol, u32 secid)
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{
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int err;
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BUG_ON(!x);
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err = selinux_xfrm_sec_ctx_alloc(&x->security, uctx, pol, secid);
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return err;
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}
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/*
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* LSM hook implementation that frees xfrm_state security information.
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*/
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void selinux_xfrm_state_free(struct xfrm_state *x)
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{
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struct xfrm_sec_ctx *ctx = x->security;
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if (ctx)
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kfree(ctx);
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}
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/*
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* SELinux internal function to retrieve the context of a connected
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* (sk->sk_state == TCP_ESTABLISHED) TCP socket based on its security
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* association used to connect to the remote socket.
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*
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* Retrieve via getsockopt SO_PEERSEC.
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*/
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u32 selinux_socket_getpeer_stream(struct sock *sk)
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{
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struct dst_entry *dst, *dst_test;
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u32 peer_sid = SECSID_NULL;
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if (sk->sk_state != TCP_ESTABLISHED)
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goto out;
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dst = sk_dst_get(sk);
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if (!dst)
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goto out;
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for (dst_test = dst; dst_test != 0;
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dst_test = dst_test->child) {
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struct xfrm_state *x = dst_test->xfrm;
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if (x && selinux_authorizable_xfrm(x)) {
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struct xfrm_sec_ctx *ctx = x->security;
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peer_sid = ctx->ctx_sid;
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break;
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}
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}
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dst_release(dst);
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out:
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return peer_sid;
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}
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/*
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* SELinux internal function to retrieve the context of a UDP packet
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* based on its security association used to connect to the remote socket.
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*
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* Retrieve via setsockopt IP_PASSSEC and recvmsg with control message
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* type SCM_SECURITY.
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*/
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u32 selinux_socket_getpeer_dgram(struct sk_buff *skb)
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{
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struct sec_path *sp;
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if (skb == NULL)
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return SECSID_NULL;
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if (skb->sk->sk_protocol != IPPROTO_UDP)
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return SECSID_NULL;
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sp = skb->sp;
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if (sp) {
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int i;
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for (i = sp->len-1; i >= 0; i--) {
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struct xfrm_state *x = sp->xvec[i];
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if (selinux_authorizable_xfrm(x)) {
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struct xfrm_sec_ctx *ctx = x->security;
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return ctx->ctx_sid;
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}
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}
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}
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return SECSID_NULL;
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}
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/*
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* LSM hook implementation that authorizes deletion of labeled SAs.
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*/
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int selinux_xfrm_state_delete(struct xfrm_state *x)
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{
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struct task_security_struct *tsec = current->security;
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struct xfrm_sec_ctx *ctx = x->security;
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int rc = 0;
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if (ctx)
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rc = avc_has_perm(tsec->sid, ctx->ctx_sid,
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SECCLASS_ASSOCIATION,
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ASSOCIATION__SETCONTEXT, NULL);
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return rc;
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}
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/*
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* LSM hook that controls access to unlabelled packets. If
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* a xfrm_state is authorizable (defined by macro) then it was
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* already authorized by the IPSec process. If not, then
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* we need to check for unlabelled access since this may not have
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* gone thru the IPSec process.
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*/
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int selinux_xfrm_sock_rcv_skb(u32 isec_sid, struct sk_buff *skb,
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struct avc_audit_data *ad)
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{
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int i, rc = 0;
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struct sec_path *sp;
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u32 sel_sid = SECINITSID_UNLABELED;
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sp = skb->sp;
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if (sp) {
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for (i = 0; i < sp->len; i++) {
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struct xfrm_state *x = sp->xvec[i];
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if (x && selinux_authorizable_xfrm(x)) {
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struct xfrm_sec_ctx *ctx = x->security;
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sel_sid = ctx->ctx_sid;
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break;
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}
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}
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}
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rc = avc_has_perm(isec_sid, sel_sid, SECCLASS_ASSOCIATION,
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ASSOCIATION__RECVFROM, ad);
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return rc;
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}
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/*
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* POSTROUTE_LAST hook's XFRM processing:
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* If we have no security association, then we need to determine
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* whether the socket is allowed to send to an unlabelled destination.
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* If we do have a authorizable security association, then it has already been
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* checked in xfrm_policy_lookup hook.
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*/
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int selinux_xfrm_postroute_last(u32 isec_sid, struct sk_buff *skb,
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struct avc_audit_data *ad)
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{
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struct dst_entry *dst;
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int rc = 0;
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dst = skb->dst;
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if (dst) {
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struct dst_entry *dst_test;
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for (dst_test = dst; dst_test != 0;
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dst_test = dst_test->child) {
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struct xfrm_state *x = dst_test->xfrm;
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if (x && selinux_authorizable_xfrm(x))
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goto out;
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}
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}
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rc = avc_has_perm(isec_sid, SECINITSID_UNLABELED, SECCLASS_ASSOCIATION,
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ASSOCIATION__SENDTO, ad);
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out:
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return rc;
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}
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