--- /dev/null
+/*
+ * NSA Security-Enhanced Linux (SELinux) security module
+ *
+ * This file contains the SELinux XFRM hook function implementations.
+ *
+ * Authors: Serge Hallyn <sergeh@us.ibm.com>
+ * Trent Jaeger <jaegert@us.ibm.com>
+ *
+ * Updated: Venkat Yekkirala <vyekkirala@TrustedCS.com>
+ *
+ * Granular IPSec Associations for use in MLS environments.
+ *
+ * Copyright (C) 2005 International Business Machines Corporation
+ * Copyright (C) 2006 Trusted Computer Solutions, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2,
+ * as published by the Free Software Foundation.
+ */
+
+/*
+ * USAGE:
+ * NOTES:
+ * 1. Make sure to enable the following options in your kernel config:
+ * CONFIG_SECURITY=y
+ * CONFIG_SECURITY_NETWORK=y
+ * CONFIG_SECURITY_NETWORK_XFRM=y
+ * CONFIG_SECURITY_SELINUX=m/y
+ * ISSUES:
+ * 1. Caching packets, so they are not dropped during negotiation
+ * 2. Emulating a reasonable SO_PEERSEC across machines
+ * 3. Testing addition of sk_policy's with security context via setsockopt
+ */
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/security.h>
+#include <linux/types.h>
+#include <linux/netfilter.h>
+#include <linux/netfilter_ipv4.h>
+#include <linux/netfilter_ipv6.h>
+#include <linux/slab.h>
+#include <linux/ip.h>
+#include <linux/tcp.h>
+#include <linux/skbuff.h>
+#include <linux/xfrm.h>
+#include <net/xfrm.h>
+#include <net/checksum.h>
+#include <net/udp.h>
+#include <linux/atomic.h>
+
+#include "avc.h"
+#include "objsec.h"
+#include "xfrm.h"
+
+/* Labeled XFRM instance counter */
+atomic_t selinux_xfrm_refcount = ATOMIC_INIT(0);
+
+/*
+ * Returns true if the context is an LSM/SELinux context.
+ */
+static inline int selinux_authorizable_ctx(struct xfrm_sec_ctx *ctx)
+{
+ return (ctx &&
+ (ctx->ctx_doi == XFRM_SC_DOI_LSM) &&
+ (ctx->ctx_alg == XFRM_SC_ALG_SELINUX));
+}
+
+/*
+ * Returns true if the xfrm contains a security blob for SELinux.
+ */
+static inline int selinux_authorizable_xfrm(struct xfrm_state *x)
+{
+ return selinux_authorizable_ctx(x->security);
+}
+
+/*
+ * Allocates a xfrm_sec_state and populates it using the supplied security
+ * xfrm_user_sec_ctx context.
+ */
+static int selinux_xfrm_alloc_user(struct xfrm_sec_ctx **ctxp,
+ struct xfrm_user_sec_ctx *uctx,
+ gfp_t gfp)
+{
+ int rc;
+ const struct task_security_struct *tsec = current_security();
+ struct xfrm_sec_ctx *ctx = NULL;
+ u32 str_len;
+
+ if (ctxp == NULL || uctx == NULL ||
+ uctx->ctx_doi != XFRM_SC_DOI_LSM ||
+ uctx->ctx_alg != XFRM_SC_ALG_SELINUX)
+ return -EINVAL;
+
+ str_len = uctx->ctx_len;
+ if (str_len >= PAGE_SIZE)
+ return -ENOMEM;
+
+ ctx = kmalloc(sizeof(*ctx) + str_len + 1, gfp);
+ if (!ctx)
+ return -ENOMEM;
+
+ ctx->ctx_doi = XFRM_SC_DOI_LSM;
+ ctx->ctx_alg = XFRM_SC_ALG_SELINUX;
+ ctx->ctx_len = str_len;
+ memcpy(ctx->ctx_str, &uctx[1], str_len);
+ ctx->ctx_str[str_len] = '\0';
+ rc = security_context_to_sid(ctx->ctx_str, str_len, &ctx->ctx_sid, gfp);
+ if (rc)
+ goto err;
+
+ rc = avc_has_perm(tsec->sid, ctx->ctx_sid,
+ SECCLASS_ASSOCIATION, ASSOCIATION__SETCONTEXT, NULL);
+ if (rc)
+ goto err;
+
+ *ctxp = ctx;
+ atomic_inc(&selinux_xfrm_refcount);
+ return 0;
+
+err:
+ kfree(ctx);
+ return rc;
+}
+
+/*
+ * Free the xfrm_sec_ctx structure.
+ */
+static void selinux_xfrm_free(struct xfrm_sec_ctx *ctx)
+{
+ if (!ctx)
+ return;
+
+ atomic_dec(&selinux_xfrm_refcount);
+ kfree(ctx);
+}
+
+/*
+ * Authorize the deletion of a labeled SA or policy rule.
+ */
+static int selinux_xfrm_delete(struct xfrm_sec_ctx *ctx)
+{
+ const struct task_security_struct *tsec = current_security();
+
+ if (!ctx)
+ return 0;
+
+ return avc_has_perm(tsec->sid, ctx->ctx_sid,
+ SECCLASS_ASSOCIATION, ASSOCIATION__SETCONTEXT,
+ NULL);
+}
+
+/*
+ * LSM hook implementation that authorizes that a flow can use a xfrm policy
+ * rule.
+ */
+int selinux_xfrm_policy_lookup(struct xfrm_sec_ctx *ctx, u32 fl_secid, u8 dir)
+{
+ int rc;
+
+ /* All flows should be treated as polmatch'ing an otherwise applicable
+ * "non-labeled" policy. This would prevent inadvertent "leaks". */
+ if (!ctx)
+ return 0;
+
+ /* Context sid is either set to label or ANY_ASSOC */
+ if (!selinux_authorizable_ctx(ctx))
+ return -EINVAL;
+
+ rc = avc_has_perm(fl_secid, ctx->ctx_sid,
+ SECCLASS_ASSOCIATION, ASSOCIATION__POLMATCH, NULL);
+ return (rc == -EACCES ? -ESRCH : rc);
+}
+
+/*
+ * LSM hook implementation that authorizes that a state matches
+ * the given policy, flow combo.
+ */
+int selinux_xfrm_state_pol_flow_match(struct xfrm_state *x,
+ struct xfrm_policy *xp,
+ const struct flowi *fl)
+{
+ u32 state_sid;
+
+ if (!xp->security)
+ if (x->security)
+ /* unlabeled policy and labeled SA can't match */
+ return 0;
+ else
+ /* unlabeled policy and unlabeled SA match all flows */
+ return 1;
+ else
+ if (!x->security)
+ /* unlabeled SA and labeled policy can't match */
+ return 0;
+ else
+ if (!selinux_authorizable_xfrm(x))
+ /* Not a SELinux-labeled SA */
+ return 0;
+
+ state_sid = x->security->ctx_sid;
+
+ if (fl->flowi_secid != state_sid)
+ return 0;
+
+ /* We don't need a separate SA Vs. policy polmatch check since the SA
+ * is now of the same label as the flow and a flow Vs. policy polmatch
+ * check had already happened in selinux_xfrm_policy_lookup() above. */
+ return (avc_has_perm(fl->flowi_secid, state_sid,
+ SECCLASS_ASSOCIATION, ASSOCIATION__SENDTO,
+ NULL) ? 0 : 1);
+}
+
+static u32 selinux_xfrm_skb_sid_egress(struct sk_buff *skb)
+{
+ struct dst_entry *dst = skb_dst(skb);
+ struct xfrm_state *x;
+
+ if (dst == NULL)
+ return SECSID_NULL;
+ x = dst->xfrm;
+ if (x == NULL || !selinux_authorizable_xfrm(x))
+ return SECSID_NULL;
+
+ return x->security->ctx_sid;
+}
+
+static int selinux_xfrm_skb_sid_ingress(struct sk_buff *skb,
+ u32 *sid, int ckall)
+{
+ u32 sid_session = SECSID_NULL;
+ struct sec_path *sp = skb->sp;
+
+ if (sp) {
+ int i;
+
+ for (i = sp->len - 1; i >= 0; i--) {
+ struct xfrm_state *x = sp->xvec[i];
+ if (selinux_authorizable_xfrm(x)) {
+ struct xfrm_sec_ctx *ctx = x->security;
+
+ if (sid_session == SECSID_NULL) {
+ sid_session = ctx->ctx_sid;
+ if (!ckall)
+ goto out;
+ } else if (sid_session != ctx->ctx_sid) {
+ *sid = SECSID_NULL;
+ return -EINVAL;
+ }
+ }
+ }
+ }
+
+out:
+ *sid = sid_session;
+ return 0;
+}
+
+/*
+ * LSM hook implementation that checks and/or returns the xfrm sid for the
+ * incoming packet.
+ */
+int selinux_xfrm_decode_session(struct sk_buff *skb, u32 *sid, int ckall)
+{
+ if (skb == NULL) {
+ *sid = SECSID_NULL;
+ return 0;
+ }
+ return selinux_xfrm_skb_sid_ingress(skb, sid, ckall);
+}
+
+int selinux_xfrm_skb_sid(struct sk_buff *skb, u32 *sid)
+{
+ int rc;
+
+ rc = selinux_xfrm_skb_sid_ingress(skb, sid, 0);
+ if (rc == 0 && *sid == SECSID_NULL)
+ *sid = selinux_xfrm_skb_sid_egress(skb);
+
+ return rc;
+}
+
+/*
+ * LSM hook implementation that allocs and transfers uctx spec to xfrm_policy.
+ */
+int selinux_xfrm_policy_alloc(struct xfrm_sec_ctx **ctxp,
+ struct xfrm_user_sec_ctx *uctx,
+ gfp_t gfp)
+{
+ return selinux_xfrm_alloc_user(ctxp, uctx, gfp);
+}
+
+/*
+ * LSM hook implementation that copies security data structure from old to new
+ * for policy cloning.
+ */
+int selinux_xfrm_policy_clone(struct xfrm_sec_ctx *old_ctx,
+ struct xfrm_sec_ctx **new_ctxp)
+{
+ struct xfrm_sec_ctx *new_ctx;
+
+ if (!old_ctx)
+ return 0;
+
+ new_ctx = kmemdup(old_ctx, sizeof(*old_ctx) + old_ctx->ctx_len,
+ GFP_ATOMIC);
+ if (!new_ctx)
+ return -ENOMEM;
+ atomic_inc(&selinux_xfrm_refcount);
+ *new_ctxp = new_ctx;
+
+ return 0;
+}
+
+/*
+ * LSM hook implementation that frees xfrm_sec_ctx security information.
+ */
+void selinux_xfrm_policy_free(struct xfrm_sec_ctx *ctx)
+{
+ selinux_xfrm_free(ctx);
+}
+
+/*
+ * LSM hook implementation that authorizes deletion of labeled policies.
+ */
+int selinux_xfrm_policy_delete(struct xfrm_sec_ctx *ctx)
+{
+ return selinux_xfrm_delete(ctx);
+}
+
+/*
+ * LSM hook implementation that allocates a xfrm_sec_state, populates it using
+ * the supplied security context, and assigns it to the xfrm_state.
+ */
+int selinux_xfrm_state_alloc(struct xfrm_state *x,
+ struct xfrm_user_sec_ctx *uctx)
+{
+ return selinux_xfrm_alloc_user(&x->security, uctx, GFP_KERNEL);
+}
+
+/*
+ * LSM hook implementation that allocates a xfrm_sec_state and populates based
+ * on a secid.
+ */
+int selinux_xfrm_state_alloc_acquire(struct xfrm_state *x,
+ struct xfrm_sec_ctx *polsec, u32 secid)
+{
+ int rc;
+ struct xfrm_sec_ctx *ctx;
+ char *ctx_str = NULL;
+ int str_len;
+
+ if (!polsec)
+ return 0;
+
+ if (secid == 0)
+ return -EINVAL;
+
+ rc = security_sid_to_context(secid, &ctx_str, &str_len);
+ if (rc)
+ return rc;
+
+ ctx = kmalloc(sizeof(*ctx) + str_len, GFP_ATOMIC);
+ if (!ctx) {
+ rc = -ENOMEM;
+ goto out;
+ }
+
+ ctx->ctx_doi = XFRM_SC_DOI_LSM;
+ ctx->ctx_alg = XFRM_SC_ALG_SELINUX;
+ ctx->ctx_sid = secid;
+ ctx->ctx_len = str_len;
+ memcpy(ctx->ctx_str, ctx_str, str_len);
+
+ x->security = ctx;
+ atomic_inc(&selinux_xfrm_refcount);
+out:
+ kfree(ctx_str);
+ return rc;
+}
+
+/*
+ * LSM hook implementation that frees xfrm_state security information.
+ */
+void selinux_xfrm_state_free(struct xfrm_state *x)
+{
+ selinux_xfrm_free(x->security);
+}
+
+/*
+ * LSM hook implementation that authorizes deletion of labeled SAs.
+ */
+int selinux_xfrm_state_delete(struct xfrm_state *x)
+{
+ return selinux_xfrm_delete(x->security);
+}
+
+/*
+ * LSM hook that controls access to unlabelled packets. If
+ * a xfrm_state is authorizable (defined by macro) then it was
+ * already authorized by the IPSec process. If not, then
+ * we need to check for unlabelled access since this may not have
+ * gone thru the IPSec process.
+ */
+int selinux_xfrm_sock_rcv_skb(u32 sk_sid, struct sk_buff *skb,
+ struct common_audit_data *ad)
+{
+ int i;
+ struct sec_path *sp = skb->sp;
+ u32 peer_sid = SECINITSID_UNLABELED;
+
+ if (sp) {
+ for (i = 0; i < sp->len; i++) {
+ struct xfrm_state *x = sp->xvec[i];
+
+ if (x && selinux_authorizable_xfrm(x)) {
+ struct xfrm_sec_ctx *ctx = x->security;
+ peer_sid = ctx->ctx_sid;
+ break;
+ }
+ }
+ }
+
+ /* This check even when there's no association involved is intended,
+ * according to Trent Jaeger, to make sure a process can't engage in
+ * non-IPsec communication unless explicitly allowed by policy. */
+ return avc_has_perm(sk_sid, peer_sid,
+ SECCLASS_ASSOCIATION, ASSOCIATION__RECVFROM, ad);
+}
+
+/*
+ * POSTROUTE_LAST hook's XFRM processing:
+ * If we have no security association, then we need to determine
+ * whether the socket is allowed to send to an unlabelled destination.
+ * If we do have a authorizable security association, then it has already been
+ * checked in the selinux_xfrm_state_pol_flow_match hook above.
+ */
+int selinux_xfrm_postroute_last(u32 sk_sid, struct sk_buff *skb,
+ struct common_audit_data *ad, u8 proto)
+{
+ struct dst_entry *dst;
+
+ switch (proto) {
+ case IPPROTO_AH:
+ case IPPROTO_ESP:
+ case IPPROTO_COMP:
+ /* We should have already seen this packet once before it
+ * underwent xfrm(s). No need to subject it to the unlabeled
+ * check. */
+ return 0;
+ default:
+ break;
+ }
+
+ dst = skb_dst(skb);
+ if (dst) {
+ struct dst_entry *iter;
+
+ for (iter = dst; iter != NULL; iter = iter->child) {
+ struct xfrm_state *x = iter->xfrm;
+
+ if (x && selinux_authorizable_xfrm(x))
+ return 0;
+ }
+ }
+
+ /* This check even when there's no association involved is intended,
+ * according to Trent Jaeger, to make sure a process can't engage in
+ * non-IPsec communication unless explicitly allowed by policy. */
+ return avc_has_perm(sk_sid, SECINITSID_UNLABELED,
+ SECCLASS_ASSOCIATION, ASSOCIATION__SENDTO, ad);
+}
Code Review / kvmfornfv.git / blobdiff