mls.c

linux 内核源代码

/*
 * Implementation of the multi-level security (MLS) policy.
 *
 * Author : Stephen Smalley, <[e-mail]>
 */
/*
 * Updated: Trusted Computer Solutions, Inc. <[e-mail]>
 *
 *	Support for enhanced MLS infrastructure.
 *
 * Copyright (C) 2004-2006 Trusted Computer Solutions, Inc.
 */
/*
 * Updated: Hewlett-Packard <[e-mail]>
 *
 *      Added support to import/export the MLS label from NetLabel
 *
 * (c) Copyright Hewlett-Packard Development Company, L.P., 2006
 */

#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <net/netlabel.h>
#include "sidtab.h"
#include "mls.h"
#include "policydb.h"
#include "services.h"

/*
 * Return the length in bytes for the MLS fields of the
 * security context string representation of `context'.
 */
int mls_compute_context_len(struct context * context)
{
	int i, l, len, head, prev;
	char *nm;
	struct ebitmap *e;
	struct ebitmap_node *node;

	if (!selinux_mls_enabled)
		return 0;

	len = 1; /* for the beginning ":" */
	for (l = 0; l < 2; l++) {
		int index_sens = context->range.level[l].sens;
		len += strlen(policydb.p_sens_val_to_name[index_sens - 1]);

		/* categories */
		head = -2;
		prev = -2;
		e = &context->range.level[l].cat;
		ebitmap_for_each_positive_bit(e, node, i) {
			if (i - prev > 1) {
				/* one or more negative bits are skipped */
				if (head != prev) {
					nm = policydb.p_cat_val_to_name[prev];
					len += strlen(nm) + 1;
				}
				nm = policydb.p_cat_val_to_name[i];
				len += strlen(nm) + 1;
				head = i;
			}
			prev = i;
		}
		if (prev != head) {
			nm = policydb.p_cat_val_to_name[prev];
			len += strlen(nm) + 1;
		}
		if (l == 0) {
			if (mls_level_eq(&context->range.level[0],
					 &context->range.level[1]))
				break;
			else
				len++;
		}
	}

	return len;
}

/*
 * Write the security context string representation of
 * the MLS fields of `context' into the string `*scontext'.
 * Update `*scontext' to point to the end of the MLS fields.
 */
void mls_sid_to_context(struct context *context,
                        char **scontext)
{
	char *scontextp, *nm;
	int i, l, head, prev;
	struct ebitmap *e;
	struct ebitmap_node *node;

	if (!selinux_mls_enabled)
		return;

	scontextp = *scontext;

	*scontextp = ':';
	scontextp++;

	for (l = 0; l < 2; l++) {
		strcpy(scontextp,
		       policydb.p_sens_val_to_name[context->range.level[l].sens - 1]);
		scontextp += strlen(scontextp);

		/* categories */
		head = -2;
		prev = -2;
		e = &context->range.level[l].cat;
		ebitmap_for_each_positive_bit(e, node, i) {
			if (i - prev > 1) {
				/* one or more negative bits are skipped */
				if (prev != head) {
					if (prev - head > 1)
						*scontextp++ = '.';
					else
						*scontextp++ = ',';
					nm = policydb.p_cat_val_to_name[prev];
					strcpy(scontextp, nm);
					scontextp += strlen(nm);
				}
				if (prev < 0)
					*scontextp++ = ':';
				else
					*scontextp++ = ',';
				nm = policydb.p_cat_val_to_name[i];
				strcpy(scontextp, nm);
				scontextp += strlen(nm);
				head = i;
			}
			prev = i;
		}

		if (prev != head) {
			if (prev - head > 1)
				*scontextp++ = '.';
			else
				*scontextp++ = ',';
			nm = policydb.p_cat_val_to_name[prev];
			strcpy(scontextp, nm);
			scontextp += strlen(nm);
		}

		if (l == 0) {
			if (mls_level_eq(&context->range.level[0],
			                 &context->range.level[1]))
				break;
			else
				*scontextp++ = '-';
		}
	}

	*scontext = scontextp;
	return;
}

int mls_level_isvalid(struct policydb *p, struct mls_level *l)
{
	struct level_datum *levdatum;
	struct ebitmap_node *node;
	int i;

	if (!l->sens || l->sens > p->p_levels.nprim)
		return 0;
	levdatum = hashtab_search(p->p_levels.table,
				  p->p_sens_val_to_name[l->sens - 1]);
	if (!levdatum)
		return 0;

	ebitmap_for_each_positive_bit(&l->cat, node, i) {
		if (i > p->p_cats.nprim)
			return 0;
		if (!ebitmap_get_bit(&levdatum->level->cat, i)) {
			/*
			 * Category may not be associated with
			 * sensitivity.
			 */
			return 0;
		}
	}

	return 1;
}

int mls_range_isvalid(struct policydb *p, struct mls_range *r)
{
	return (mls_level_isvalid(p, &r->level[0]) &&
		mls_level_isvalid(p, &r->level[1]) &&
		mls_level_dom(&r->level[1], &r->level[0]));
}

/*
 * Return 1 if the MLS fields in the security context
 * structure `c' are valid.  Return 0 otherwise.
 */
int mls_context_isvalid(struct policydb *p, struct context *c)
{
	struct user_datum *usrdatum;

	if (!selinux_mls_enabled)
		return 1;

	if (!mls_range_isvalid(p, &c->range))
		return 0;

	if (c->role == OBJECT_R_VAL)
		return 1;

	/*
	 * User must be authorized for the MLS range.
	 */
	if (!c->user || c->user > p->p_users.nprim)
		return 0;
	usrdatum = p->user_val_to_struct[c->user - 1];
	if (!mls_range_contains(usrdatum->range, c->range))
		return 0; /* user may not be associated with range */

	return 1;
}

/*
 * Set the MLS fields in the security context structure
 * `context' based on the string representation in
 * the string `*scontext'.  Update `*scontext' to
 * point to the end of the string representation of
 * the MLS fields.
 *
 * This function modifies the string in place, inserting
 * NULL characters to terminate the MLS fields.
 *
 * If a def_sid is provided and no MLS field is present,
 * copy the MLS field of the associated default context.
 * Used for upgraded to MLS systems where objects may lack
 * MLS fields.
 *
 * Policy read-lock must be held for sidtab lookup.
 *
 */
int mls_context_to_sid(char oldc,
		       char **scontext,
		       struct context *context,
		       struct sidtab *s,
		       u32 def_sid)
{

	char delim;
	char *scontextp, *p, *rngptr;
	struct level_datum *levdatum;
	struct cat_datum *catdatum, *rngdatum;
	int l, rc = -EINVAL;

	if (!selinux_mls_enabled) {
		if (def_sid != SECSID_NULL && oldc)
			*scontext += strlen(*scontext)+1;
		return 0;
	}

	/*
	 * No MLS component to the security context, try and map to
	 * default if provided.
	 */
	if (!oldc) {
		struct context *defcon;

		if (def_sid == SECSID_NULL)
			goto out;

		defcon = sidtab_search(s, def_sid);
		if (!defcon)
			goto out;

		rc = mls_context_cpy(context, defcon);
		goto out;
	}

	/* Extract low sensitivity. */
	scontextp = p = *scontext;
	while (*p && *p != ':' && *p != '-')
		p++;

	delim = *p;
	if (delim != 0)
		*p++ = 0;

	for (l = 0; l < 2; l++) {
		levdatum = hashtab_search(policydb.p_levels.table, scontextp);
		if (!levdatum) {
			rc = -EINVAL;
			goto out;
		}

		context->range.level[l].sens = levdatum->level->sens;

		if (delim == ':') {
			/* Extract category set. */
			while (1) {
				scontextp = p;
				while (*p && *p != ',' && *p != '-')
					p++;
				delim = *p;
				if (delim != 0)
					*p++ = 0;

				/* Separate into range if exists */
				if ((rngptr = strchr(scontextp, '.')) != NULL) {
					/* Remove '.' */
					*rngptr++ = 0;
				}

				catdatum = hashtab_search(policydb.p_cats.table,
				                          scontextp);
				if (!catdatum) {
					rc = -EINVAL;
					goto out;
				}

				rc = ebitmap_set_bit(&context->range.level[l].cat,
				                     catdatum->value - 1, 1);
				if (rc)
					goto out;

				/* If range, set all categories in range */
				if (rngptr) {
					int i;

					rngdatum = hashtab_search(policydb.p_cats.table, rngptr);
					if (!rngdatum) {