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527 lines
12 KiB
527 lines
12 KiB
/*
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* Implementation of the multi-level security (MLS) policy.
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*
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* Author : Stephen Smalley, <sds@epoch.ncsc.mil>
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*/
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/*
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* Updated: Trusted Computer Solutions, Inc. <dgoeddel@trustedcs.com>
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*
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* Support for enhanced MLS infrastructure.
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*
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* Copyright (C) 2004-2005 Trusted Computer Solutions, Inc.
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*/
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#include <linux/kernel.h>
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#include <linux/slab.h>
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#include <linux/string.h>
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#include <linux/errno.h>
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#include "mls.h"
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#include "policydb.h"
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#include "services.h"
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/*
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* Return the length in bytes for the MLS fields of the
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* security context string representation of `context'.
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*/
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int mls_compute_context_len(struct context * context)
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{
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int i, l, len, range;
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if (!selinux_mls_enabled)
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return 0;
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len = 1; /* for the beginning ":" */
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for (l = 0; l < 2; l++) {
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range = 0;
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len += strlen(policydb.p_sens_val_to_name[context->range.level[l].sens - 1]);
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for (i = 1; i <= ebitmap_length(&context->range.level[l].cat); i++) {
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if (ebitmap_get_bit(&context->range.level[l].cat, i - 1)) {
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if (range) {
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range++;
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continue;
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}
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len += strlen(policydb.p_cat_val_to_name[i - 1]) + 1;
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range++;
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} else {
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if (range > 1)
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len += strlen(policydb.p_cat_val_to_name[i - 2]) + 1;
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range = 0;
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}
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}
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/* Handle case where last category is the end of range */
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if (range > 1)
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len += strlen(policydb.p_cat_val_to_name[i - 2]) + 1;
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if (l == 0) {
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if (mls_level_eq(&context->range.level[0],
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&context->range.level[1]))
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break;
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else
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len++;
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}
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}
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return len;
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}
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/*
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* Write the security context string representation of
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* the MLS fields of `context' into the string `*scontext'.
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* Update `*scontext' to point to the end of the MLS fields.
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*/
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void mls_sid_to_context(struct context *context,
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char **scontext)
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{
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char *scontextp;
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int i, l, range, wrote_sep;
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if (!selinux_mls_enabled)
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return;
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scontextp = *scontext;
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*scontextp = ':';
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scontextp++;
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for (l = 0; l < 2; l++) {
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range = 0;
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wrote_sep = 0;
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strcpy(scontextp,
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policydb.p_sens_val_to_name[context->range.level[l].sens - 1]);
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scontextp += strlen(policydb.p_sens_val_to_name[context->range.level[l].sens - 1]);
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/* categories */
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for (i = 1; i <= ebitmap_length(&context->range.level[l].cat); i++) {
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if (ebitmap_get_bit(&context->range.level[l].cat, i - 1)) {
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if (range) {
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range++;
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continue;
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}
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if (!wrote_sep) {
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*scontextp++ = ':';
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wrote_sep = 1;
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} else
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*scontextp++ = ',';
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strcpy(scontextp, policydb.p_cat_val_to_name[i - 1]);
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scontextp += strlen(policydb.p_cat_val_to_name[i - 1]);
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range++;
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} else {
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if (range > 1) {
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if (range > 2)
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*scontextp++ = '.';
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else
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*scontextp++ = ',';
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strcpy(scontextp, policydb.p_cat_val_to_name[i - 2]);
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scontextp += strlen(policydb.p_cat_val_to_name[i - 2]);
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}
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range = 0;
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}
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}
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/* Handle case where last category is the end of range */
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if (range > 1) {
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if (range > 2)
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*scontextp++ = '.';
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else
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*scontextp++ = ',';
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strcpy(scontextp, policydb.p_cat_val_to_name[i - 2]);
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scontextp += strlen(policydb.p_cat_val_to_name[i - 2]);
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}
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if (l == 0) {
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if (mls_level_eq(&context->range.level[0],
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&context->range.level[1]))
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break;
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else {
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*scontextp = '-';
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scontextp++;
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}
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}
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}
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*scontext = scontextp;
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return;
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}
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/*
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* Return 1 if the MLS fields in the security context
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* structure `c' are valid. Return 0 otherwise.
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*/
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int mls_context_isvalid(struct policydb *p, struct context *c)
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{
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struct level_datum *levdatum;
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struct user_datum *usrdatum;
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int i, l;
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if (!selinux_mls_enabled)
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return 1;
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/*
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* MLS range validity checks: high must dominate low, low level must
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* be valid (category set <-> sensitivity check), and high level must
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* be valid (category set <-> sensitivity check)
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*/
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if (!mls_level_dom(&c->range.level[1], &c->range.level[0]))
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/* High does not dominate low. */
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return 0;
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for (l = 0; l < 2; l++) {
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if (!c->range.level[l].sens || c->range.level[l].sens > p->p_levels.nprim)
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return 0;
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levdatum = hashtab_search(p->p_levels.table,
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p->p_sens_val_to_name[c->range.level[l].sens - 1]);
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if (!levdatum)
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return 0;
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for (i = 1; i <= ebitmap_length(&c->range.level[l].cat); i++) {
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if (ebitmap_get_bit(&c->range.level[l].cat, i - 1)) {
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if (i > p->p_cats.nprim)
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return 0;
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if (!ebitmap_get_bit(&levdatum->level->cat, i - 1))
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/*
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* Category may not be associated with
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* sensitivity in low level.
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*/
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return 0;
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}
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}
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}
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if (c->role == OBJECT_R_VAL)
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return 1;
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/*
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* User must be authorized for the MLS range.
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*/
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if (!c->user || c->user > p->p_users.nprim)
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return 0;
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usrdatum = p->user_val_to_struct[c->user - 1];
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if (!mls_range_contains(usrdatum->range, c->range))
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return 0; /* user may not be associated with range */
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return 1;
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}
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/*
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* Set the MLS fields in the security context structure
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* `context' based on the string representation in
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* the string `*scontext'. Update `*scontext' to
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* point to the end of the string representation of
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* the MLS fields.
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*
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* This function modifies the string in place, inserting
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* NULL characters to terminate the MLS fields.
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*/
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int mls_context_to_sid(char oldc,
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char **scontext,
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struct context *context)
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{
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char delim;
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char *scontextp, *p, *rngptr;
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struct level_datum *levdatum;
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struct cat_datum *catdatum, *rngdatum;
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int l, rc = -EINVAL;
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if (!selinux_mls_enabled)
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return 0;
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/* No MLS component to the security context. */
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if (!oldc)
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goto out;
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/* Extract low sensitivity. */
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scontextp = p = *scontext;
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while (*p && *p != ':' && *p != '-')
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p++;
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delim = *p;
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if (delim != 0)
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*p++ = 0;
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for (l = 0; l < 2; l++) {
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levdatum = hashtab_search(policydb.p_levels.table, scontextp);
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if (!levdatum) {
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rc = -EINVAL;
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goto out;
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}
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context->range.level[l].sens = levdatum->level->sens;
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if (delim == ':') {
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/* Extract category set. */
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while (1) {
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scontextp = p;
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while (*p && *p != ',' && *p != '-')
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p++;
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delim = *p;
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if (delim != 0)
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*p++ = 0;
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/* Separate into range if exists */
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if ((rngptr = strchr(scontextp, '.')) != NULL) {
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/* Remove '.' */
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*rngptr++ = 0;
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}
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catdatum = hashtab_search(policydb.p_cats.table,
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scontextp);
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if (!catdatum) {
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rc = -EINVAL;
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goto out;
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}
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rc = ebitmap_set_bit(&context->range.level[l].cat,
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catdatum->value - 1, 1);
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if (rc)
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goto out;
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/* If range, set all categories in range */
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if (rngptr) {
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int i;
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rngdatum = hashtab_search(policydb.p_cats.table, rngptr);
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if (!rngdatum) {
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rc = -EINVAL;
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goto out;
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}
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if (catdatum->value >= rngdatum->value) {
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rc = -EINVAL;
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goto out;
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}
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for (i = catdatum->value; i < rngdatum->value; i++) {
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rc = ebitmap_set_bit(&context->range.level[l].cat, i, 1);
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if (rc)
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goto out;
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}
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}
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if (delim != ',')
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break;
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}
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}
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if (delim == '-') {
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/* Extract high sensitivity. */
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scontextp = p;
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while (*p && *p != ':')
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p++;
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delim = *p;
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if (delim != 0)
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*p++ = 0;
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} else
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break;
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}
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if (l == 0) {
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context->range.level[1].sens = context->range.level[0].sens;
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rc = ebitmap_cpy(&context->range.level[1].cat,
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&context->range.level[0].cat);
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if (rc)
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goto out;
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}
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*scontext = ++p;
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rc = 0;
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out:
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return rc;
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}
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/*
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* Copies the MLS range from `src' into `dst'.
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*/
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static inline int mls_copy_context(struct context *dst,
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struct context *src)
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{
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int l, rc = 0;
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/* Copy the MLS range from the source context */
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for (l = 0; l < 2; l++) {
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dst->range.level[l].sens = src->range.level[l].sens;
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rc = ebitmap_cpy(&dst->range.level[l].cat,
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&src->range.level[l].cat);
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if (rc)
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break;
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}
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return rc;
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}
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/*
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* Copies the effective MLS range from `src' into `dst'.
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*/
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static inline int mls_scopy_context(struct context *dst,
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struct context *src)
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{
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int l, rc = 0;
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/* Copy the MLS range from the source context */
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for (l = 0; l < 2; l++) {
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dst->range.level[l].sens = src->range.level[0].sens;
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rc = ebitmap_cpy(&dst->range.level[l].cat,
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&src->range.level[0].cat);
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if (rc)
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break;
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}
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return rc;
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}
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/*
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* Copies the MLS range `range' into `context'.
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*/
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static inline int mls_range_set(struct context *context,
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struct mls_range *range)
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{
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int l, rc = 0;
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/* Copy the MLS range into the context */
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for (l = 0; l < 2; l++) {
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context->range.level[l].sens = range->level[l].sens;
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rc = ebitmap_cpy(&context->range.level[l].cat,
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&range->level[l].cat);
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if (rc)
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break;
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}
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return rc;
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}
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int mls_setup_user_range(struct context *fromcon, struct user_datum *user,
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struct context *usercon)
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{
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if (selinux_mls_enabled) {
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struct mls_level *fromcon_sen = &(fromcon->range.level[0]);
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struct mls_level *fromcon_clr = &(fromcon->range.level[1]);
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struct mls_level *user_low = &(user->range.level[0]);
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struct mls_level *user_clr = &(user->range.level[1]);
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struct mls_level *user_def = &(user->dfltlevel);
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struct mls_level *usercon_sen = &(usercon->range.level[0]);
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struct mls_level *usercon_clr = &(usercon->range.level[1]);
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/* Honor the user's default level if we can */
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if (mls_level_between(user_def, fromcon_sen, fromcon_clr)) {
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*usercon_sen = *user_def;
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} else if (mls_level_between(fromcon_sen, user_def, user_clr)) {
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*usercon_sen = *fromcon_sen;
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} else if (mls_level_between(fromcon_clr, user_low, user_def)) {
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*usercon_sen = *user_low;
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} else
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return -EINVAL;
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/* Lower the clearance of available contexts
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if the clearance of "fromcon" is lower than
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that of the user's default clearance (but
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only if the "fromcon" clearance dominates
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the user's computed sensitivity level) */
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if (mls_level_dom(user_clr, fromcon_clr)) {
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*usercon_clr = *fromcon_clr;
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} else if (mls_level_dom(fromcon_clr, user_clr)) {
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*usercon_clr = *user_clr;
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} else
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return -EINVAL;
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}
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return 0;
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}
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/*
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* Convert the MLS fields in the security context
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* structure `c' from the values specified in the
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* policy `oldp' to the values specified in the policy `newp'.
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*/
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int mls_convert_context(struct policydb *oldp,
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struct policydb *newp,
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struct context *c)
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{
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struct level_datum *levdatum;
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struct cat_datum *catdatum;
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struct ebitmap bitmap;
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int l, i;
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if (!selinux_mls_enabled)
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return 0;
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for (l = 0; l < 2; l++) {
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levdatum = hashtab_search(newp->p_levels.table,
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oldp->p_sens_val_to_name[c->range.level[l].sens - 1]);
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if (!levdatum)
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return -EINVAL;
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c->range.level[l].sens = levdatum->level->sens;
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ebitmap_init(&bitmap);
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for (i = 1; i <= ebitmap_length(&c->range.level[l].cat); i++) {
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if (ebitmap_get_bit(&c->range.level[l].cat, i - 1)) {
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int rc;
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catdatum = hashtab_search(newp->p_cats.table,
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oldp->p_cat_val_to_name[i - 1]);
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if (!catdatum)
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return -EINVAL;
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rc = ebitmap_set_bit(&bitmap, catdatum->value - 1, 1);
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if (rc)
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return rc;
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}
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}
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ebitmap_destroy(&c->range.level[l].cat);
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c->range.level[l].cat = bitmap;
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}
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return 0;
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}
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int mls_compute_sid(struct context *scontext,
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struct context *tcontext,
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u16 tclass,
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u32 specified,
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struct context *newcontext)
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{
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if (!selinux_mls_enabled)
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return 0;
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switch (specified) {
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case AVTAB_TRANSITION:
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if (tclass == SECCLASS_PROCESS) {
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struct range_trans *rangetr;
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/* Look for a range transition rule. */
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for (rangetr = policydb.range_tr; rangetr;
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rangetr = rangetr->next) {
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if (rangetr->dom == scontext->type &&
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rangetr->type == tcontext->type) {
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/* Set the range from the rule */
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return mls_range_set(newcontext,
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&rangetr->range);
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}
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}
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}
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/* Fallthrough */
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case AVTAB_CHANGE:
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if (tclass == SECCLASS_PROCESS)
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/* Use the process MLS attributes. */
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return mls_copy_context(newcontext, scontext);
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else
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/* Use the process effective MLS attributes. */
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return mls_scopy_context(newcontext, scontext);
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case AVTAB_MEMBER:
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/* Only polyinstantiate the MLS attributes if
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the type is being polyinstantiated */
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if (newcontext->type != tcontext->type) {
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/* Use the process effective MLS attributes. */
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return mls_scopy_context(newcontext, scontext);
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} else {
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/* Use the related object MLS attributes. */
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return mls_copy_context(newcontext, tcontext);
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}
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default:
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return -EINVAL;
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}
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return -EINVAL;
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}
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