services.c

linux-2.6.15.6

/*
 * Implementation of the security services.
 *
 * Authors : Stephen Smalley, <[e-mail]>
 *           James Morris <[e-mail]>
 *
 * Updated: Trusted Computer Solutions, Inc. <[e-mail]>
 *
 *	Support for enhanced MLS infrastructure.
 *
 * Updated: Frank Mayer <[e-mail]> and Karl MacMillan <[e-mail]>
 *
 * 	Added conditional policy language extensions
 *
 * Copyright (C) 2004-2005 Trusted Computer Solutions, Inc.
 * Copyright (C) 2003 - 2004 Tresys Technology, LLC
 * Copyright (C) 2003 Red Hat, Inc., James Morris <[e-mail]>
 *	This program is free software; you can redistribute it and/or modify
 *  	it under the terms of the GNU General Public License as published by
 *	the Free Software Foundation, version 2.
 */
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/spinlock.h>
#include <linux/errno.h>
#include <linux/in.h>
#include <linux/sched.h>
#include <linux/audit.h>
#include <asm/semaphore.h>
#include "flask.h"
#include "avc.h"
#include "avc_ss.h"
#include "security.h"
#include "context.h"
#include "policydb.h"
#include "sidtab.h"
#include "services.h"
#include "conditional.h"
#include "mls.h"

extern void selnl_notify_policyload(u32 seqno);
unsigned int policydb_loaded_version;

static DEFINE_RWLOCK(policy_rwlock);
#define POLICY_RDLOCK read_lock(&policy_rwlock)
#define POLICY_WRLOCK write_lock_irq(&policy_rwlock)
#define POLICY_RDUNLOCK read_unlock(&policy_rwlock)
#define POLICY_WRUNLOCK write_unlock_irq(&policy_rwlock)

static DECLARE_MUTEX(load_sem);
#define LOAD_LOCK down(&load_sem)
#define LOAD_UNLOCK up(&load_sem)

static struct sidtab sidtab;
struct policydb policydb;
int ss_initialized = 0;

/*
 * The largest sequence number that has been used when
 * providing an access decision to the access vector cache.
 * The sequence number only changes when a policy change
 * occurs.
 */
static u32 latest_granting = 0;

/* Forward declaration. */
static int context_struct_to_string(struct context *context, char **scontext,
				    u32 *scontext_len);

/*
 * Return the boolean value of a constraint expression
 * when it is applied to the specified source and target
 * security contexts.
 *
 * xcontext is a special beast...  It is used by the validatetrans rules
 * only.  For these rules, scontext is the context before the transition,
 * tcontext is the context after the transition, and xcontext is the context
 * of the process performing the transition.  All other callers of
 * constraint_expr_eval should pass in NULL for xcontext.
 */
static int constraint_expr_eval(struct context *scontext,
				struct context *tcontext,
				struct context *xcontext,
				struct constraint_expr *cexpr)
{
	u32 val1, val2;
	struct context *c;
	struct role_datum *r1, *r2;
	struct mls_level *l1, *l2;
	struct constraint_expr *e;
	int s[CEXPR_MAXDEPTH];
	int sp = -1;

	for (e = cexpr; e; e = e->next) {
		switch (e->expr_type) {
		case CEXPR_NOT:
			BUG_ON(sp < 0);
			s[sp] = !s[sp];
			break;
		case CEXPR_AND:
			BUG_ON(sp < 1);
			sp--;
			s[sp] &= s[sp+1];
			break;
		case CEXPR_OR:
			BUG_ON(sp < 1);
			sp--;
			s[sp] |= s[sp+1];
			break;
		case CEXPR_ATTR:
			if (sp == (CEXPR_MAXDEPTH-1))
				return 0;
			switch (e->attr) {
			case CEXPR_USER:
				val1 = scontext->user;
				val2 = tcontext->user;
				break;
			case CEXPR_TYPE:
				val1 = scontext->type;
				val2 = tcontext->type;
				break;
			case CEXPR_ROLE:
				val1 = scontext->role;
				val2 = tcontext->role;
				r1 = policydb.role_val_to_struct[val1 - 1];
				r2 = policydb.role_val_to_struct[val2 - 1];
				switch (e->op) {
				case CEXPR_DOM:
					s[++sp] = ebitmap_get_bit(&r1->dominates,
								  val2 - 1);
					continue;
				case CEXPR_DOMBY:
					s[++sp] = ebitmap_get_bit(&r2->dominates,
								  val1 - 1);
					continue;
				case CEXPR_INCOMP:
					s[++sp] = ( !ebitmap_get_bit(&r1->dominates,
								     val2 - 1) &&
						    !ebitmap_get_bit(&r2->dominates,
								     val1 - 1) );
					continue;
				default:
					break;
				}
				break;
			case CEXPR_L1L2:
				l1 = &(scontext->range.level[0]);
				l2 = &(tcontext->range.level[0]);
				goto mls_ops;
			case CEXPR_L1H2:
				l1 = &(scontext->range.level[0]);
				l2 = &(tcontext->range.level[1]);
				goto mls_ops;
			case CEXPR_H1L2:
				l1 = &(scontext->range.level[1]);
				l2 = &(tcontext->range.level[0]);
				goto mls_ops;
			case CEXPR_H1H2:
				l1 = &(scontext->range.level[1]);
				l2 = &(tcontext->range.level[1]);
				goto mls_ops;
			case CEXPR_L1H1:
				l1 = &(scontext->range.level[0]);
				l2 = &(scontext->range.level[1]);
				goto mls_ops;
			case CEXPR_L2H2:
				l1 = &(tcontext->range.level[0]);
				l2 = &(tcontext->range.level[1]);
				goto mls_ops;
mls_ops:
			switch (e->op) {
			case CEXPR_EQ:
				s[++sp] = mls_level_eq(l1, l2);
				continue;
			case CEXPR_NEQ:
				s[++sp] = !mls_level_eq(l1, l2);
				continue;
			case CEXPR_DOM:
				s[++sp] = mls_level_dom(l1, l2);
				continue;
			case CEXPR_DOMBY:
				s[++sp] = mls_level_dom(l2, l1);
				continue;
			case CEXPR_INCOMP:
				s[++sp] = mls_level_incomp(l2, l1);
				continue;
			default:
				BUG();
				return 0;
			}
			break;
			default:
				BUG();
				return 0;
			}

			switch (e->op) {
			case CEXPR_EQ:
				s[++sp] = (val1 == val2);
				break;
			case CEXPR_NEQ:
				s[++sp] = (val1 != val2);
				break;
			default:
				BUG();
				return 0;
			}
			break;
		case CEXPR_NAMES:
			if (sp == (CEXPR_MAXDEPTH-1))
				return 0;
			c = scontext;
			if (e->attr & CEXPR_TARGET)
				c = tcontext;
			else if (e->attr & CEXPR_XTARGET) {
				c = xcontext;
				if (!c) {
					BUG();
					return 0;
				}
			}
			if (e->attr & CEXPR_USER)
				val1 = c->user;
			else if (e->attr & CEXPR_ROLE)
				val1 = c->role;
			else if (e->attr & CEXPR_TYPE)
				val1 = c->type;
			else {
				BUG();
				return 0;
			}

			switch (e->op) {
			case CEXPR_EQ:
				s[++sp] = ebitmap_get_bit(&e->names, val1 - 1);
				break;
			case CEXPR_NEQ:
				s[++sp] = !ebitmap_get_bit(&e->names, val1 - 1);
				break;
			default:
				BUG();
				return 0;
			}
			break;
		default:
			BUG();
			return 0;
		}
	}

	BUG_ON(sp != 0);
	return s[0];
}

/*
 * Compute access vectors based on a context structure pair for
 * the permissions in a particular class.
 */
static int context_struct_compute_av(struct context *scontext,
				     struct context *tcontext,
				     u16 tclass,
				     u32 requested,
				     struct av_decision *avd)
{
	struct constraint_node *constraint;
	struct role_allow *ra;
	struct avtab_key avkey;
	struct avtab_node *node;
	struct class_datum *tclass_datum;
	struct ebitmap *sattr, *tattr;
	struct ebitmap_node *snode, *tnode;
	unsigned int i, j;

	/*
	 * Remap extended Netlink classes for old policy versions.
	 * Do this here rather than socket_type_to_security_class()
	 * in case a newer policy version is loaded, allowing sockets
	 * to remain in the correct class.
	 */
	if (policydb_loaded_version < POLICYDB_VERSION_NLCLASS)
		if (tclass >= SECCLASS_NETLINK_ROUTE_SOCKET &&
		    tclass <= SECCLASS_NETLINK_DNRT_SOCKET)
			tclass = SECCLASS_NETLINK_SOCKET;

	if (!tclass || tclass > policydb.p_classes.nprim) {
		printk(KERN_ERR "security_compute_av:  unrecognized class %d\n",
		       tclass);
		return -EINVAL;
	}
	tclass_datum = policydb.class_val_to_struct[tclass - 1];

	/*
	 * Initialize the access vectors to the default values.
	 */
	avd->allowed = 0;
	avd->decided = 0xffffffff;
	avd->auditallow = 0;
	avd->auditdeny = 0xffffffff;
	avd->seqno = latest_granting;

	/*
	 * If a specific type enforcement rule was defined for
	 * this permission check, then use it.
	 */
	avkey.target_class = tclass;
	avkey.specified = AVTAB_AV;
	sattr = &policydb.type_attr_map[scontext->type - 1];
	tattr = &policydb.type_attr_map[tcontext->type - 1];
	ebitmap_for_each_bit(sattr, snode, i) {
		if (!ebitmap_node_get_bit(snode, i))
			continue;
		ebitmap_for_each_bit(tattr, tnode, j) {
			if (!ebitmap_node_get_bit(tnode, j))
				continue;
			avkey.source_type = i + 1;
			avkey.target_type = j + 1;
			for (node = avtab_search_node(&policydb.te_avtab, &avkey);
			     node != NULL;
			     node = avtab_search_node_next(node, avkey.specified)) {
				if (node->key.specified == AVTAB_ALLOWED)
					avd->allowed |= node->datum.data;
				else if (node->key.specified == AVTAB_AUDITALLOW)
					avd->auditallow |= node->datum.data;
				else if (node->key.specified == AVTAB_AUDITDENY)
					avd->auditdeny &= node->datum.data;
			}

			/* Check conditional av table for additional permissions */
			cond_compute_av(&policydb.te_cond_avtab, &avkey, avd);

		}
	}

	/*
	 * Remove any permissions prohibited by a constraint (this includes
	 * the MLS policy).
	 */
	constraint = tclass_datum->constraints;
	while (constraint) {
		if ((constraint->permissions & (avd->allowed)) &&
		    !constraint_expr_eval(scontext, tcontext, NULL,
					  constraint->expr)) {
			avd->allowed = (avd->allowed) & ~(constraint->permissions);
		}
		constraint = constraint->next;
	}

	/*
	 * If checking process transition permission and the
	 * role is changing, then check the (current_role, new_role)
	 * pair.
	 */
	if (tclass == SECCLASS_PROCESS &&
	    (avd->allowed & (PROCESS__TRANSITION | PROCESS__DYNTRANSITION)) &&
	    scontext->role != tcontext->role) {
		for (ra = policydb.role_allow; ra; ra = ra->next) {
			if (scontext->role == ra->role &&
			    tcontext->role == ra->new_role)
				break;
		}
		if (!ra)
			avd->allowed = (avd->allowed) & ~(PROCESS__TRANSITION |
			                                PROCESS__DYNTRANSITION);
	}

	return 0;
}

static int security_validtrans_handle_fail(struct context *ocontext,
                                           struct context *ncontext,
                                           struct context *tcontext,
                                           u16 tclass)
{
	char *o = NULL, *n = NULL, *t = NULL;
	u32 olen, nlen, tlen;

	if (context_struct_to_string(ocontext, &o, &olen) < 0)
		goto out;
	if (context_struct_to_string(ncontext, &n, &nlen) < 0)
		goto out;
	if (context_struct_to_string(tcontext, &t, &tlen) < 0)
		goto out;
	audit_log(current->audit_context, GFP_ATOMIC, AUDIT_SELINUX_ERR,
	          "security_validate_transition:  denied for"
	          " oldcontext=%s newcontext=%s taskcontext=%s tclass=%s",
	          o, n, t, policydb.p_class_val_to_name[tclass-1]);
out:
	kfree(o);
	kfree(n);
	kfree(t);

	if (!selinux_enforcing)
		return 0;
	return -EPERM;
}

int security_validate_transition(u32 oldsid, u32 newsid, u32 tasksid,
                                 u16 tclass)
{
	struct context *ocontext;
	struct context *ncontext;
	struct context *tcontext;
	struct class_datum *tclass_datum;
	struct constraint_node *constraint;
	int rc = 0;

	if (!ss_initialized)
		return 0;

	POLICY_RDLOCK;

	/*
	 * Remap extended Netlink classes for old policy versions.
	 * Do this here rather than socket_type_to_security_class()
	 * in case a newer policy version is loaded, allowing sockets
	 * to remain in the correct class.
	 */
	if (policydb_loaded_version < POLICYDB_VERSION_NLCLASS)
		if (tclass >= SECCLASS_NETLINK_ROUTE_SOCKET &&
		    tclass <= SECCLASS_NETLINK_DNRT_SOCKET)
			tclass = SECCLASS_NETLINK_SOCKET;

	if (!tclass || tclass > policydb.p_classes.nprim) {
		printk(KERN_ERR "security_validate_transition:  "
		       "unrecognized class %d\n", tclass);
		rc = -EINVAL;
		goto out;
	}
	tclass_datum = policydb.class_val_to_struct[tclass - 1];

	ocontext = sidtab_search(&sidtab, oldsid);
	if (!ocontext) {
		printk(KERN_ERR "security_validate_transition: "
		       " unrecognized SID %d\n", oldsid);
		rc = -EINVAL;
		goto out;
	}

	ncontext = sidtab_search(&sidtab, newsid);
	if (!ncontext) {
		printk(KERN_ERR "security_validate_transition: "
		       " unrecognized SID %d\n", newsid);
		rc = -EINVAL;
		goto out;
	}

	tcontext = sidtab_search(&sidtab, tasksid);
	if (!tcontext) {
		printk(KERN_ERR "security_validate_transition: "
		       " unrecognized SID %d\n", tasksid);
		rc = -EINVAL;
		goto out;
	}

	constraint = tclass_datum->validatetrans;
	while (constraint) {
		if (!constraint_expr_eval(ocontext, ncontext, tcontext,
		                          constraint->expr)) {
			rc = security_validtrans_handle_fail(ocontext, ncontext,
			                                     tcontext, tclass);
			goto out;
		}
		constraint = constraint->next;
	}

out:
	POLICY_RDUNLOCK;
	return rc;
}

/**
 * security_compute_av - Compute access vector decisions.
 * @ssid: source security identifier
 * @tsid: target security identifier
 * @tclass: target security class
 * @requested: requested permissions
 * @avd: access vector decisions
 *
 * Compute a set of access vector decisions based on the
 * SID pair (@ssid, @tsid) for the permissions in @tclass.
 * Return -%EINVAL if any of the parameters are invalid or %0
 * if the access vector decisions were computed successfully.
 */
int security_compute_av(u32 ssid,
			u32 tsid,
			u16 tclass,
			u32 requested,
			struct av_decision *avd)
{
	struct context *scontext = NULL, *tcontext = NULL;
	int rc = 0;

	if (!ss_initialized) {
		avd->allowed = 0xffffffff;
		avd->decided = 0xffffffff;
		avd->auditallow = 0;
		avd->auditdeny = 0xffffffff;
		avd->seqno = latest_granting;
		return 0;
	}

	POLICY_RDLOCK;

	scontext = sidtab_search(&sidtab, ssid);
	if (!scontext) {
		printk(KERN_ERR "security_compute_av:  unrecognized SID %d\n",
		       ssid);
		rc = -EINVAL;
		goto out;
	}
	tcontext = sidtab_search(&sidtab, tsid);
	if (!tcontext) {
		printk(KERN_ERR "security_compute_av:  unrecognized SID %d\n",
		       tsid);
		rc = -EINVAL;
		goto out;
	}

	rc = context_struct_compute_av(scontext, tcontext, tclass,
				       requested, avd);
out:
	POLICY_RDUNLOCK;
	return rc;
}

/*
 * Write the security context string representation of
 * the context structure `context' into a dynamically
 * allocated string of the correct size.  Set `*scontext'
 * to point to this string and set `*scontext_len' to
 * the length of the string.
 */
static int context_struct_to_string(struct context *context, char **scontext, u32 *scontext_len)
{
	char *scontextp;

	*scontext = NULL;
	*scontext_len = 0;

	/* Compute the size of the context. */
	*scontext_len += strlen(policydb.p_user_val_to_name[context->user - 1]) + 1;
	*scontext_len += strlen(policydb.p_role_val_to_name[context->role - 1]) + 1;
	*scontext_len += strlen(policydb.p_type_val_to_name[context->type - 1]) + 1;
	*scontext_len += mls_compute_context_len(context);

	/* Allocate space for the context; caller must free this space. */
	scontextp = kmalloc(*scontext_len, GFP_ATOMIC);
	if (!scontextp) {
		return -ENOMEM;
	}
	*scontext = scontextp;

	/*
	 * Copy the user name, role name and type name into the context.
	 */
	sprintf(scontextp, "%s:%s:%s",
		policydb.p_user_val_to_name[context->user - 1],
		policydb.p_role_val_to_name[context->role - 1],
		policydb.p_type_val_to_name[context->type - 1]);
	scontextp += strlen(policydb.p_user_val_to_name[context->user - 1]) +
	             1 + strlen(policydb.p_role_val_to_name[context->role - 1]) +
	             1 + strlen(policydb.p_type_val_to_name[context->type - 1]);

	mls_sid_to_context(context, &scontextp);

	*scontextp = 0;

	return 0;
}

#include "initial_sid_to_string.h"

/**
 * security_sid_to_context - Obtain a context for a given SID.
 * @sid: security identifier, SID
 * @scontext: security context
 * @scontext_len: length in bytes
 *
 * Write the string representation of the context associated with @sid
 * into a dynamically allocated string of the correct size.  Set @scontext
 * to point to this string and set @scontext_len to the length of the string.
 */
int security_sid_to_context(u32 sid, char **scontext, u32 *scontext_len)
{
	struct context *context;
	int rc = 0;

	if (!ss_initialized) {
		if (sid <= SECINITSID_NUM) {
			char *scontextp;

			*scontext_len = strlen(initial_sid_to_string[sid]) + 1;
			scontextp = kmalloc(*scontext_len,GFP_ATOMIC);
			strcpy(scontextp, initial_sid_to_string[sid]);
			*scontext = scontextp;
			goto out;
		}
		printk(KERN_ERR "security_sid_to_context:  called before initial "
		       "load_policy on unknown SID %d\n", sid);
		rc = -EINVAL;
		goto out;
	}
	POLICY_RDLOCK;