diff options
Diffstat (limited to 'security/selinux/xfrm.c')
| -rw-r--r-- | security/selinux/xfrm.c | 473 |
1 files changed, 473 insertions, 0 deletions
diff --git a/security/selinux/xfrm.c b/security/selinux/xfrm.c new file mode 100644 index 000000000..c576832fe --- /dev/null +++ b/security/selinux/xfrm.c @@ -0,0 +1,473 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * 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. + */ + +/* + * 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/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 __read_mostly = 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 = selinux_cred(current_cred()); + 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(struct_size(ctx, ctx_str, 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(&selinux_state, ctx->ctx_str, str_len, + &ctx->ctx_sid, gfp); + if (rc) + goto err; + + rc = avc_has_perm(&selinux_state, + 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 = selinux_cred(current_cred()); + + if (!ctx) + return 0; + + return avc_has_perm(&selinux_state, + 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) +{ + 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(&selinux_state, + 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_common *flic) +{ + u32 state_sid; + u32 flic_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; + flic_sid = flic->flowic_secid; + + if (flic_sid != 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(&selinux_state, flic_sid, 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_sec_path(skb); + + 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; + u32 str_len; + + if (!polsec) + return 0; + + if (secid == 0) + return -EINVAL; + + rc = security_sid_to_context(&selinux_state, secid, &ctx_str, + &str_len); + if (rc) + return rc; + + ctx = kmalloc(struct_size(ctx, ctx_str, 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_sec_path(skb); + 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(&selinux_state, + 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 = xfrm_dst_child(iter)) { + 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(&selinux_state, sk_sid, SECINITSID_UNLABELED, + SECCLASS_ASSOCIATION, ASSOCIATION__SENDTO, ad); +} |