/* * 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/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 <asm/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 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); } /* * 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; u32 sel_sid; /* Context sid is either set to label or ANY_ASSOC */ if (ctx) { if (!selinux_authorizable_ctx(ctx)) return -EINVAL; sel_sid = ctx->ctx_sid; } else /* * All flows should be treated as polmatch'ing an * otherwise applicable "non-labeled" policy. This * would prevent inadvertent "leaks". */ return 0; rc = avc_has_perm(fl_secid, sel_sid, SECCLASS_ASSOCIATION, ASSOCIATION__POLMATCH, NULL); if (rc == -EACCES) return -ESRCH; return 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, struct flowi *fl) { u32 state_sid; int rc; 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->secid != state_sid) return 0; rc = avc_has_perm(fl->secid, state_sid, SECCLASS_ASSOCIATION, ASSOCIATION__SENDTO, NULL)? 0:1; /* * 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 rc; } /* * 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) { struct sec_path *sp; *sid = SECSID_NULL; if (skb == NULL) return 0; sp = skb->sp; if (sp) { int i, sid_set = 0; 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_set) { *sid = ctx->ctx_sid; sid_set = 1; if (!ckall) break; } else if (*sid != ctx->ctx_sid) return -EINVAL; } } } return 0; } /* * Security blob allocation for xfrm_policy and xfrm_state * CTX does not have a meaningful value on input */ static int selinux_xfrm_sec_ctx_alloc(struct xfrm_sec_ctx **ctxp, struct xfrm_user_sec_ctx *uctx, u32 sid) { int rc = 0; const struct task_security_struct *tsec = current_security(); struct xfrm_sec_ctx *ctx = NULL; char *ctx_str = NULL; u32 str_len; BUG_ON(uctx && sid); if (!uctx) goto not_from_user; if (uctx->ctx_doi != XFRM_SC_ALG_SELINUX) return -EINVAL; str_len = uctx->ctx_len; if (str_len >= PAGE_SIZE) return -ENOMEM; *ctxp = ctx = kmalloc(sizeof(*ctx) + str_len + 1, GFP_KERNEL); if (!ctx) return -ENOMEM; ctx->ctx_doi = uctx->ctx_doi; ctx->ctx_len = str_len; ctx->ctx_alg = uctx->ctx_alg; 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); if (rc) goto out; /* * Does the subject have permission to set security context? */ rc = avc_has_perm(tsec->sid, ctx->ctx_sid, SECCLASS_ASSOCIATION, ASSOCIATION__SETCONTEXT, NULL); if (rc) goto out; return rc; not_from_user: rc = security_sid_to_context(sid, &ctx_str, &str_len); if (rc) goto out; *ctxp = 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 = sid; ctx->ctx_len = str_len; memcpy(ctx->ctx_str, ctx_str, str_len); goto out2; out: *ctxp = NULL; kfree(ctx); out2: kfree(ctx_str); 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) { int err; BUG_ON(!uctx); err = selinux_xfrm_sec_ctx_alloc(ctxp, uctx, 0); if (err == 0) atomic_inc(&selinux_xfrm_refcount); return err; } /* * 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) { new_ctx = kmalloc(sizeof(*old_ctx) + old_ctx->ctx_len, GFP_KERNEL); if (!new_ctx) return -ENOMEM; memcpy(new_ctx, old_ctx, sizeof(*new_ctx)); memcpy(new_ctx->ctx_str, old_ctx->ctx_str, new_ctx->ctx_len); *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) { kfree(ctx); } /* * LSM hook implementation that authorizes deletion of labeled policies. */ int selinux_xfrm_policy_delete(struct xfrm_sec_ctx *ctx) { const struct task_security_struct *tsec = current_security(); int rc = 0; if (ctx) { rc = avc_has_perm(tsec->sid, ctx->ctx_sid, SECCLASS_ASSOCIATION, ASSOCIATION__SETCONTEXT, NULL); if (rc == 0) atomic_dec(&selinux_xfrm_refcount); } return rc; } /* * LSM hook implementation that allocs and transfers sec_ctx spec to * xfrm_state. */ int selinux_xfrm_state_alloc(struct xfrm_state *x, struct xfrm_user_sec_ctx *uctx, u32 secid) { int err; BUG_ON(!x); err = selinux_xfrm_sec_ctx_alloc(&x->security, uctx, secid); if (err == 0) atomic_inc(&selinux_xfrm_refcount); return err; } /* * LSM hook implementation that frees xfrm_state security information. */ void selinux_xfrm_state_free(struct xfrm_state *x) { struct xfrm_sec_ctx *ctx = x->security; kfree(ctx); } /* * LSM hook implementation that authorizes deletion of labeled SAs. */ int selinux_xfrm_state_delete(struct xfrm_state *x) { const struct task_security_struct *tsec = current_security(); struct xfrm_sec_ctx *ctx = x->security; int rc = 0; if (ctx) { rc = avc_has_perm(tsec->sid, ctx->ctx_sid, SECCLASS_ASSOCIATION, ASSOCIATION__SETCONTEXT, NULL); if (rc == 0) atomic_dec(&selinux_xfrm_refcount); } return rc; } /* * 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 isec_sid, struct sk_buff *skb, struct avc_audit_data *ad) { int i, rc = 0; struct sec_path *sp; u32 sel_sid = SECINITSID_UNLABELED; sp = skb->sp; 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; sel_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. */ rc = avc_has_perm(isec_sid, sel_sid, SECCLASS_ASSOCIATION, ASSOCIATION__RECVFROM, ad); return rc; } /* * 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 isec_sid, struct sk_buff *skb, struct avc_audit_data *ad, u8 proto) { struct dst_entry *dst; int rc = 0; dst = skb->dst; if (dst) { struct dst_entry *dst_test; for (dst_test = dst; dst_test != NULL; dst_test = dst_test->child) { struct xfrm_state *x = dst_test->xfrm; if (x && selinux_authorizable_xfrm(x)) goto out; } } 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. */ goto out; default: 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. */ rc = avc_has_perm(isec_sid, SECINITSID_UNLABELED, SECCLASS_ASSOCIATION, ASSOCIATION__SENDTO, ad); out: return rc; }