/* SPDX-License-Identifier: GPL-2.0 */
/*
 * A security context is a set of security attributes
 * associated with each subject and object controlled
 * by the security policy.  Security contexts are
  * externally represented as variable-length strings
 * that can be interpreted by a user or application
 * with an understanding of the security policy.
 * Internally, the security server uses a simple
 * structure.  This structure is private to the
 * security server and can be changed without affecting
 * clients of the security server.
 *
 * Author : Stephen Smalley, <sds@tycho.nsa.gov>
 */
#ifndef _SS_CONTEXT_H_
#define _SS_CONTEXT_H_

#include "ebitmap.h"
#include "mls_types.h"
#include "security.h"

/*
 * A security context consists of an authenticated user
 * identity, a role, a type and a MLS range.
 */
struct context {
        u32 user;
        u32 role;
        u32 type;
        u32 len;        /* length of string in bytes */
        struct mls_range range;
        char *str;      /* string representation if context cannot be mapped. */
};

static inline void mls_context_init(struct context *c)
{
        memset(&c->range, 0, sizeof(c->range));
}

static inline int mls_context_cpy(struct context *dst, struct context *src)
{
        int rc;

        dst->range.level[0].sens = src->range.level[0].sens;
        rc = ebitmap_cpy(&dst->range.level[0].cat, &src->range.level[0].cat);
        if (rc)
                goto out;

        dst->range.level[1].sens = src->range.level[1].sens;
        rc = ebitmap_cpy(&dst->range.level[1].cat, &src->range.level[1].cat);
        if (rc)
                ebitmap_destroy(&dst->range.level[0].cat);
out:
        return rc;
}

/*
 * Sets both levels in the MLS range of 'dst' to the low level of 'src'.
 */
static inline int mls_context_cpy_low(struct context *dst, struct context *src)
{
        int rc;

        dst->range.level[0].sens = src->range.level[0].sens;
        rc = ebitmap_cpy(&dst->range.level[0].cat, &src->range.level[0].cat);
        if (rc)
                goto out;

        dst->range.level[1].sens = src->range.level[0].sens;
        rc = ebitmap_cpy(&dst->range.level[1].cat, &src->range.level[0].cat);
        if (rc)
                ebitmap_destroy(&dst->range.level[0].cat);
out:
        return rc;
}

/*
 * Sets both levels in the MLS range of 'dst' to the high level of 'src'.
 */
static inline int mls_context_cpy_high(struct context *dst, struct context *src)
{
        int rc;

        dst->range.level[0].sens = src->range.level[1].sens;
        rc = ebitmap_cpy(&dst->range.level[0].cat, &src->range.level[1].cat);
        if (rc)
                goto out;

        dst->range.level[1].sens = src->range.level[1].sens;
        rc = ebitmap_cpy(&dst->range.level[1].cat, &src->range.level[1].cat);
        if (rc)
                ebitmap_destroy(&dst->range.level[0].cat);
out:
        return rc;
}


static inline int mls_context_glblub(struct context *dst,
                                     struct context *c1, struct context *c2)
{
        struct mls_range *dr = &dst->range, *r1 = &c1->range, *r2 = &c2->range;
        int rc = 0;

        if (r1->level[1].sens < r2->level[0].sens ||
            r2->level[1].sens < r1->level[0].sens)
                /* These ranges have no common sensitivities */
                return -EINVAL;

        /* Take the greatest of the low */
        dr->level[0].sens = max(r1->level[0].sens, r2->level[0].sens);

        /* Take the least of the high */
        dr->level[1].sens = min(r1->level[1].sens, r2->level[1].sens);

        rc = ebitmap_and(&dr->level[0].cat,
                         &r1->level[0].cat, &r2->level[0].cat);
        if (rc)
                goto out;

        rc = ebitmap_and(&dr->level[1].cat,
                         &r1->level[1].cat, &r2->level[1].cat);
        if (rc)
                goto out;

out:
        return rc;
}

static inline int mls_context_cmp(struct context *c1, struct context *c2)
{
        return ((c1->range.level[0].sens == c2->range.level[0].sens) &&
                ebitmap_cmp(&c1->range.level[0].cat, &c2->range.level[0].cat) &&
                (c1->range.level[1].sens == c2->range.level[1].sens) &&
                ebitmap_cmp(&c1->range.level[1].cat, &c2->range.level[1].cat));
}

static inline void mls_context_destroy(struct context *c)
{
        ebitmap_destroy(&c->range.level[0].cat);
        ebitmap_destroy(&c->range.level[1].cat);
        mls_context_init(c);
}

static inline void context_init(struct context *c)
{
        memset(c, 0, sizeof(*c));
}

static inline int context_cpy(struct context *dst, struct context *src)
{
        int rc;

        dst->user = src->user;
        dst->role = src->role;
        dst->type = src->type;
        if (src->str) {
                dst->str = kstrdup(src->str, GFP_ATOMIC);
                if (!dst->str)
                        return -ENOMEM;
                dst->len = src->len;
        } else {
                dst->str = NULL;
                dst->len = 0;
        }
        rc = mls_context_cpy(dst, src);
        if (rc) {
                kfree(dst->str);
                return rc;
        }
        return 0;
}

static inline void context_destroy(struct context *c)
{
        c->user = c->role = c->type = 0;
        kfree(c->str);
        c->str = NULL;
        c->len = 0;
        mls_context_destroy(c);
}

static inline int context_cmp(struct context *c1, struct context *c2)
{
        if (c1->len && c2->len)
                return (c1->len == c2->len && !strcmp(c1->str, c2->str));
        if (c1->len || c2->len)
                return 0;
        return ((c1->user == c2->user) &&
                (c1->role == c2->role) &&
                (c1->type == c2->type) &&
                mls_context_cmp(c1, c2));
}

u32 context_compute_hash(const struct context *c);

#endif  /* _SS_CONTEXT_H_ */