mls.c

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/*
 * Implementation of the multi-level security (MLS) policy.
 *
 * Author : Stephen Smalley, <[email protected]>
 */
/*
 * Updated: Trusted Computer Solutions, Inc. <[email protected]>
 *
 *  Support for enhanced MLS infrastructure.
 *
 * Copyright (C) 2004-2006 Trusted Computer Solutions, Inc.
 */
/*
 * Updated: Hewlett-Packard <[email protected]>
 *
 *      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 (!policydb.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(sym_name(&policydb, SYM_LEVELS, 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 = sym_name(&policydb, SYM_CATS, prev);
                    len += strlen(nm) + 1;
                }
                nm = sym_name(&policydb, SYM_CATS, i);
                len += strlen(nm) + 1;
                head = i;
            }
            prev = i;
        }
        if (prev != head) {
            nm = sym_name(&policydb, SYM_CATS, 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 (!policydb.mls_enabled)
        return;

    scontextp = *scontext;

    *scontextp = ':';
    scontextp++;

    for (l = 0; l < 2; l++) {
        strcpy(scontextp, sym_name(&policydb, SYM_LEVELS,
                       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 = sym_name(&policydb, SYM_CATS, prev);
                    strcpy(scontextp, nm);
                    scontextp += strlen(nm);
                }
                if (prev < 0)
                    *scontextp++ = ':';
                else
                    *scontextp++ = ',';
                nm = sym_name(&policydb, SYM_CATS, i);
                strcpy(scontextp, nm);
                scontextp += strlen(nm);
                head = i;
            }
            prev = i;
        }

        if (prev != head) {
            if (prev - head > 1)
                *scontextp++ = '.';
            else
                *scontextp++ = ',';
            nm = sym_name(&policydb, SYM_CATS, 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,
                  sym_name(p, SYM_LEVELS, 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 (!p->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(struct policydb *pol,
               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 (!pol->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(pol->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 */
                rngptr = strchr(scontextp, '.');
                if (rngptr != NULL) {
                    /* Remove '.' */
                    *rngptr++ = '\0';
                }

                catdatum = hashtab_search(pol->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(pol->p_cats.table, rngptr);
                    if (!rngdatum) {
                        rc = -EINVAL;
                        goto out;
                    }

                    if (catdatum->value >= rngdatum->value) {
                        rc = -EINVAL;
                        goto out;
                    }

                    for (i = catdatum->value; i < rngdatum->value; i++) {
                        rc = ebitmap_set_bit(&context->range.level[l].cat, i, 1);
                        if (rc)
                            goto out;
                    }
                }

                if (delim != ',')
                    break;
            }
        }
        if (delim == '-') {
            /* Extract high sensitivity. */
            scontextp = p;
            while (*p && *p != ':')
                p++;

            delim = *p;
            if (delim != '\0')
                *p++ = '\0';
        } else
            break;
    }

    if (l == 0) {
        context->range.level[1].sens = context->range.level[0].sens;
        rc = ebitmap_cpy(&context->range.level[1].cat,
                 &context->range.level[0].cat);
        if (rc)
            goto out;
    }
    *scontext = ++p;
    rc = 0;
out:
    return rc;
}

/*
 * Set the MLS fields in the security context structure
 * `context' based on the string representation in
 * the string `str'.  This function will allocate temporary memory with the
 * given constraints of gfp_mask.
 */
int mls_from_string(char *str, struct context *context, gfp_t gfp_mask)
{
    char *tmpstr, *freestr;
    int rc;

    if (!policydb.mls_enabled)
        return -EINVAL;

    /* we need freestr because mls_context_to_sid will change
       the value of tmpstr */
    tmpstr = freestr = kstrdup(str, gfp_mask);
    if (!tmpstr) {
        rc = -ENOMEM;
    } else {
        rc = mls_context_to_sid(&policydb, ':', &tmpstr, context,
                    NULL, SECSID_NULL);
        kfree(freestr);
    }

    return rc;
}

/*
 * Copies the MLS range `range' into `context'.
 */
int mls_range_set(struct context *context,
                struct mls_range *range)
{
    int l, rc = 0;

    /* Copy the MLS range into the  context */
    for (l = 0; l < 2; l++) {
        context->range.level[l].sens = range->level[l].sens;
        rc = ebitmap_cpy(&context->range.level[l].cat,
                 &range->level[l].cat);
        if (rc)
            break;
    }

    return rc;
}

int mls_setup_user_range(struct context *fromcon, struct user_datum *user,
             struct context *usercon)
{
    if (policydb.mls_enabled) {
        struct mls_level *fromcon_sen = &(fromcon->range.level[0]);
        struct mls_level *fromcon_clr = &(fromcon->range.level[1]);
        struct mls_level *user_low = &(user->range.level[0]);
        struct mls_level *user_clr = &(user->range.level[1]);
        struct mls_level *user_def = &(user->dfltlevel);
        struct mls_level *usercon_sen = &(usercon->range.level[0]);
        struct mls_level *usercon_clr = &(usercon->range.level[1]);

        /* Honor the user's default level if we can */
        if (mls_level_between(user_def, fromcon_sen, fromcon_clr))
            *usercon_sen = *user_def;
        else if (mls_level_between(fromcon_sen, user_def, user_clr))
            *usercon_sen = *fromcon_sen;
        else if (mls_level_between(fromcon_clr, user_low, user_def))
            *usercon_sen = *user_low;
        else
            return -EINVAL;

        /* Lower the clearance of available contexts
           if the clearance of "fromcon" is lower than
           that of the user's default clearance (but
           only if the "fromcon" clearance dominates
           the user's computed sensitivity level) */
        if (mls_level_dom(user_clr, fromcon_clr))
            *usercon_clr = *fromcon_clr;
        else if (mls_level_dom(fromcon_clr, user_clr))
            *usercon_clr = *user_clr;
        else
            return -EINVAL;
    }

    return 0;
}

/*
 * Convert the MLS fields in the security context
 * structure `c' from the values specified in the
 * policy `oldp' to the values specified in the policy `newp'.
 */
int mls_convert_context(struct policydb *oldp,
            struct policydb *newp,
            struct context *c)
{
    struct level_datum *levdatum;
    struct cat_datum *catdatum;
    struct ebitmap bitmap;
    struct ebitmap_node *node;
    int l, i;

    if (!policydb.mls_enabled)
        return 0;

    for (l = 0; l < 2; l++) {
        levdatum = hashtab_search(newp->p_levels.table,
                      sym_name(oldp, SYM_LEVELS,
                           c->range.level[l].sens - 1));

        if (!levdatum)
            return -EINVAL;
        c->range.level[l].sens = levdatum->level->sens;

        ebitmap_init(&bitmap);
        ebitmap_for_each_positive_bit(&c->range.level[l].cat, node, i) {
            int rc;

            catdatum = hashtab_search(newp->p_cats.table,
                          sym_name(oldp, SYM_CATS, i));
            if (!catdatum)
                return -EINVAL;
            rc = ebitmap_set_bit(&bitmap, catdatum->value - 1, 1);
            if (rc)
                return rc;
        }
        ebitmap_destroy(&c->range.level[l].cat);
        c->range.level[l].cat = bitmap;
    }

    return 0;
}

int mls_compute_sid(struct context *scontext,
            struct context *tcontext,
            u16 tclass,
            u32 specified,
            struct context *newcontext,
            bool sock)
{
    struct range_trans rtr;
    struct mls_range *r;
    struct class_datum *cladatum;
    int default_range = 0;

    if (!policydb.mls_enabled)
        return 0;

    switch (specified) {
    case AVTAB_TRANSITION:
        /* Look for a range transition rule. */
        rtr.source_type = scontext->type;
        rtr.target_type = tcontext->type;
        rtr.target_class = tclass;
        r = hashtab_search(policydb.range_tr, &rtr);
        if (r)
            return mls_range_set(newcontext, r);

        if (tclass && tclass <= policydb.p_classes.nprim) {
            cladatum = policydb.class_val_to_struct[tclass - 1];
            if (cladatum)
                default_range = cladatum->default_range;
        }

        switch (default_range) {
        case DEFAULT_SOURCE_LOW:
            return mls_context_cpy_low(newcontext, scontext);
        case DEFAULT_SOURCE_HIGH:
            return mls_context_cpy_high(newcontext, scontext);
        case DEFAULT_SOURCE_LOW_HIGH:
            return mls_context_cpy(newcontext, scontext);
        case DEFAULT_TARGET_LOW:
            return mls_context_cpy_low(newcontext, tcontext);
        case DEFAULT_TARGET_HIGH:
            return mls_context_cpy_high(newcontext, tcontext);
        case DEFAULT_TARGET_LOW_HIGH:
            return mls_context_cpy(newcontext, tcontext);
        }

        /* Fallthrough */
    case AVTAB_CHANGE:
        if ((tclass == policydb.process_class) || (sock == true))
            /* Use the process MLS attributes. */
            return mls_context_cpy(newcontext, scontext);
        else
            /* Use the process effective MLS attributes. */
            return mls_context_cpy_low(newcontext, scontext);
    case AVTAB_MEMBER:
        /* Use the process effective MLS attributes. */
        return mls_context_cpy_low(newcontext, scontext);

    /* fall through */
    }
    return -EINVAL;
}

#ifdef CONFIG_NETLABEL

void mls_export_netlbl_lvl(struct context *context,
               struct netlbl_lsm_secattr *secattr)
{
    if (!policydb.mls_enabled)
        return;

    secattr->attr.mls.lvl = context->range.level[0].sens - 1;
    secattr->flags |= NETLBL_SECATTR_MLS_LVL;
}

void mls_import_netlbl_lvl(struct context *context,
               struct netlbl_lsm_secattr *secattr)
{
    if (!policydb.mls_enabled)
        return;

    context->range.level[0].sens = secattr->attr.mls.lvl + 1;
    context->range.level[1].sens = context->range.level[0].sens;
}

int mls_export_netlbl_cat(struct context *context,
              struct netlbl_lsm_secattr *secattr)
{
    int rc;

    if (!policydb.mls_enabled)
        return 0;

    rc = ebitmap_netlbl_export(&context->range.level[0].cat,
                   &secattr->attr.mls.cat);
    if (rc == 0 && secattr->attr.mls.cat != NULL)
        secattr->flags |= NETLBL_SECATTR_MLS_CAT;

    return rc;
}

int mls_import_netlbl_cat(struct context *context,
              struct netlbl_lsm_secattr *secattr)
{
    int rc;

    if (!policydb.mls_enabled)
        return 0;

    rc = ebitmap_netlbl_import(&context->range.level[0].cat,
                   secattr->attr.mls.cat);
    if (rc != 0)
        goto import_netlbl_cat_failure;

    rc = ebitmap_cpy(&context->range.level[1].cat,
             &context->range.level[0].cat);
    if (rc != 0)
        goto import_netlbl_cat_failure;

    return 0;

import_netlbl_cat_failure:
    ebitmap_destroy(&context->range.level[0].cat);
    ebitmap_destroy(&context->range.level[1].cat);
    return rc;
}
#endif /* CONFIG_NETLABEL */