![Stephen Smalley](/assets/img/avatar_default.png)
Wrap the AVC state within the selinux_state structure and pass it explicitly to all AVC functions. The AVC private state is encapsulated in a selinux_avc structure that is referenced from the selinux_state. This change should have no effect on SELinux behavior or APIs (userspace or LSM). Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov> Reviewed-by: James Morris <james.morris@microsoft.com> Signed-off-by: Paul Moore <paul@paul-moore.com>
476 lines
11 KiB
C
476 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/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/slab.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 <linux/atomic.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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/* Labeled XFRM instance counter */
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atomic_t selinux_xfrm_refcount = ATOMIC_INIT(0);
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/*
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* Returns true if the context is 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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* Allocates a xfrm_sec_state and populates it using the supplied security
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* xfrm_user_sec_ctx context.
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*/
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static int selinux_xfrm_alloc_user(struct xfrm_sec_ctx **ctxp,
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struct xfrm_user_sec_ctx *uctx,
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gfp_t gfp)
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{
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int rc;
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const struct task_security_struct *tsec = current_security();
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struct xfrm_sec_ctx *ctx = NULL;
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u32 str_len;
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if (ctxp == NULL || uctx == NULL ||
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uctx->ctx_doi != XFRM_SC_DOI_LSM ||
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uctx->ctx_alg != XFRM_SC_ALG_SELINUX)
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return -EINVAL;
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str_len = uctx->ctx_len;
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if (str_len >= PAGE_SIZE)
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return -ENOMEM;
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ctx = kmalloc(sizeof(*ctx) + str_len + 1, gfp);
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if (!ctx)
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return -ENOMEM;
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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_len = str_len;
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memcpy(ctx->ctx_str, &uctx[1], str_len);
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ctx->ctx_str[str_len] = '\0';
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rc = security_context_to_sid(&selinux_state, ctx->ctx_str, str_len,
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&ctx->ctx_sid, gfp);
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if (rc)
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goto err;
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rc = avc_has_perm(&selinux_state,
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tsec->sid, ctx->ctx_sid,
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SECCLASS_ASSOCIATION, ASSOCIATION__SETCONTEXT, NULL);
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if (rc)
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goto err;
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*ctxp = ctx;
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atomic_inc(&selinux_xfrm_refcount);
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return 0;
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err:
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kfree(ctx);
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return rc;
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}
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/*
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* Free the xfrm_sec_ctx structure.
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*/
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static void selinux_xfrm_free(struct xfrm_sec_ctx *ctx)
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{
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if (!ctx)
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return;
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atomic_dec(&selinux_xfrm_refcount);
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kfree(ctx);
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}
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/*
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* Authorize the deletion of a labeled SA or policy rule.
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*/
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static int selinux_xfrm_delete(struct xfrm_sec_ctx *ctx)
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{
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const struct task_security_struct *tsec = current_security();
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if (!ctx)
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return 0;
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return avc_has_perm(&selinux_state,
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tsec->sid, ctx->ctx_sid,
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SECCLASS_ASSOCIATION, ASSOCIATION__SETCONTEXT,
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NULL);
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}
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/*
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* LSM hook implementation that authorizes that a flow can use a xfrm policy
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* rule.
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*/
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int selinux_xfrm_policy_lookup(struct xfrm_sec_ctx *ctx, u32 fl_secid, u8 dir)
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{
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int rc;
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/* All flows should be treated as polmatch'ing an otherwise applicable
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* "non-labeled" policy. This would prevent inadvertent "leaks". */
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if (!ctx)
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return 0;
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/* Context sid is either set to label or ANY_ASSOC */
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if (!selinux_authorizable_ctx(ctx))
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return -EINVAL;
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rc = avc_has_perm(&selinux_state,
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fl_secid, ctx->ctx_sid,
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SECCLASS_ASSOCIATION, ASSOCIATION__POLMATCH, NULL);
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return (rc == -EACCES ? -ESRCH : 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,
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struct xfrm_policy *xp,
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const struct flowi *fl)
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{
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u32 state_sid;
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if (!xp->security)
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if (x->security)
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/* unlabeled policy and labeled SA can't match */
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return 0;
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else
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/* unlabeled policy and unlabeled SA match all flows */
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return 1;
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else
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if (!x->security)
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/* unlabeled SA and labeled policy can't match */
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return 0;
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else
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if (!selinux_authorizable_xfrm(x))
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/* Not a SELinux-labeled SA */
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return 0;
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state_sid = x->security->ctx_sid;
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if (fl->flowi_secid != state_sid)
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return 0;
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/* We don't need a separate SA Vs. policy polmatch check since the SA
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* is now of the same label as the flow and a flow Vs. policy polmatch
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* check had already happened in selinux_xfrm_policy_lookup() above. */
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return (avc_has_perm(&selinux_state,
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fl->flowi_secid, state_sid,
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SECCLASS_ASSOCIATION, ASSOCIATION__SENDTO,
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NULL) ? 0 : 1);
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}
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static u32 selinux_xfrm_skb_sid_egress(struct sk_buff *skb)
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{
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struct dst_entry *dst = skb_dst(skb);
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struct xfrm_state *x;
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if (dst == NULL)
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return SECSID_NULL;
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x = dst->xfrm;
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if (x == NULL || !selinux_authorizable_xfrm(x))
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return SECSID_NULL;
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return x->security->ctx_sid;
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}
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static int selinux_xfrm_skb_sid_ingress(struct sk_buff *skb,
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u32 *sid, int ckall)
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{
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u32 sid_session = SECSID_NULL;
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struct sec_path *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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if (sid_session == SECSID_NULL) {
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sid_session = ctx->ctx_sid;
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if (!ckall)
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goto out;
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} else if (sid_session != ctx->ctx_sid) {
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*sid = SECSID_NULL;
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return -EINVAL;
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}
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}
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}
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}
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out:
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*sid = sid_session;
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return 0;
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}
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/*
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* LSM hook implementation that checks and/or returns the xfrm sid for the
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* incoming packet.
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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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if (skb == NULL) {
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*sid = SECSID_NULL;
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return 0;
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}
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return selinux_xfrm_skb_sid_ingress(skb, sid, ckall);
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}
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int selinux_xfrm_skb_sid(struct sk_buff *skb, u32 *sid)
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{
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int rc;
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rc = selinux_xfrm_skb_sid_ingress(skb, sid, 0);
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if (rc == 0 && *sid == SECSID_NULL)
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*sid = selinux_xfrm_skb_sid_egress(skb);
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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 xfrm_policy.
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*/
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int selinux_xfrm_policy_alloc(struct xfrm_sec_ctx **ctxp,
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struct xfrm_user_sec_ctx *uctx,
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gfp_t gfp)
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{
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return selinux_xfrm_alloc_user(ctxp, uctx, gfp);
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}
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/*
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* LSM hook implementation that copies security data structure from old to new
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* for policy cloning.
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*/
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int selinux_xfrm_policy_clone(struct xfrm_sec_ctx *old_ctx,
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struct xfrm_sec_ctx **new_ctxp)
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{
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struct xfrm_sec_ctx *new_ctx;
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if (!old_ctx)
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return 0;
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new_ctx = kmemdup(old_ctx, sizeof(*old_ctx) + old_ctx->ctx_len,
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GFP_ATOMIC);
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if (!new_ctx)
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return -ENOMEM;
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atomic_inc(&selinux_xfrm_refcount);
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*new_ctxp = new_ctx;
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return 0;
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}
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/*
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* LSM hook implementation that frees xfrm_sec_ctx security information.
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*/
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void selinux_xfrm_policy_free(struct xfrm_sec_ctx *ctx)
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{
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selinux_xfrm_free(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_sec_ctx *ctx)
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{
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return selinux_xfrm_delete(ctx);
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}
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/*
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* LSM hook implementation that allocates a xfrm_sec_state, populates it using
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* the supplied security context, and assigns it to the xfrm_state.
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*/
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int selinux_xfrm_state_alloc(struct xfrm_state *x,
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struct xfrm_user_sec_ctx *uctx)
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{
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return selinux_xfrm_alloc_user(&x->security, uctx, GFP_KERNEL);
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}
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/*
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* LSM hook implementation that allocates a xfrm_sec_state and populates based
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* on a secid.
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*/
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int selinux_xfrm_state_alloc_acquire(struct xfrm_state *x,
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struct xfrm_sec_ctx *polsec, u32 secid)
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{
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int rc;
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struct xfrm_sec_ctx *ctx;
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char *ctx_str = NULL;
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int str_len;
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if (!polsec)
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return 0;
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if (secid == 0)
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return -EINVAL;
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rc = security_sid_to_context(&selinux_state, secid, &ctx_str,
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&str_len);
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if (rc)
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return rc;
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ctx = kmalloc(sizeof(*ctx) + str_len, 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 = secid;
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ctx->ctx_len = str_len;
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memcpy(ctx->ctx_str, ctx_str, str_len);
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x->security = ctx;
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atomic_inc(&selinux_xfrm_refcount);
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out:
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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 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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selinux_xfrm_free(x->security);
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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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return selinux_xfrm_delete(x->security);
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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 sk_sid, struct sk_buff *skb,
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struct common_audit_data *ad)
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{
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int i;
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struct sec_path *sp = skb->sp;
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u32 peer_sid = SECINITSID_UNLABELED;
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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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peer_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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/* This check even when there's no association involved is intended,
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* according to Trent Jaeger, to make sure a process can't engage in
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* non-IPsec communication unless explicitly allowed by policy. */
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return avc_has_perm(&selinux_state,
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sk_sid, peer_sid,
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SECCLASS_ASSOCIATION, ASSOCIATION__RECVFROM, ad);
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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 the selinux_xfrm_state_pol_flow_match hook above.
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*/
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int selinux_xfrm_postroute_last(u32 sk_sid, struct sk_buff *skb,
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struct common_audit_data *ad, u8 proto)
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{
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struct dst_entry *dst;
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switch (proto) {
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case IPPROTO_AH:
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case IPPROTO_ESP:
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case IPPROTO_COMP:
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/* We should have already seen this packet once before it
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* underwent xfrm(s). No need to subject it to the unlabeled
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* check. */
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return 0;
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default:
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break;
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}
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dst = skb_dst(skb);
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if (dst) {
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struct dst_entry *iter;
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for (iter = dst; iter != NULL; iter = xfrm_dst_child(iter)) {
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struct xfrm_state *x = iter->xfrm;
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if (x && selinux_authorizable_xfrm(x))
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return 0;
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}
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}
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/* This check even when there's no association involved is intended,
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* according to Trent Jaeger, to make sure a process can't engage in
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* non-IPsec communication unless explicitly allowed by policy. */
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return avc_has_perm(&selinux_state, sk_sid, SECINITSID_UNLABELED,
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SECCLASS_ASSOCIATION, ASSOCIATION__SENDTO, ad);
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}
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