context.h

  1/* SPDX-License-Identifier: GPL-2.0 */
  2/*
  3 * A security context is a set of security attributes
  4 * associated with each subject and object controlled
  5 * by the security policy.  Security contexts are
  6  * externally represented as variable-length strings
  7 * that can be interpreted by a user or application
  8 * with an understanding of the security policy.
  9 * Internally, the security server uses a simple
 10 * structure.  This structure is private to the
 11 * security server and can be changed without affecting
 12 * clients of the security server.
 13 *
 14 * Author : Stephen Smalley, <stephen.smalley.work@gmail.com>
 15 */
 16
 17#ifndef _SS_CONTEXT_H_
 18#define _SS_CONTEXT_H_
 19
 20#include "ebitmap.h"
 21#include "mls_types.h"
 22#include "security.h"
 23
 24/*
 25 * A security context consists of an authenticated user
 26 * identity, a role, a type and a MLS range.
 27 */
 28struct context {
 29	u32 user;
 30	u32 role;
 31	u32 type;
 32	u32 len; /* length of string in bytes */
 33	struct mls_range range;
 34	char *str; /* string representation if context cannot be mapped. */
 35};
 36
 37static inline void mls_context_init(struct context *c)
 38{
 39	memset(&c->range, 0, sizeof(c->range));
 40}
 41
 42static inline int mls_context_cpy(struct context *dst,
 43				  const struct context *src)
 44{
 45	int rc;
 46
 47	dst->range.level[0].sens = src->range.level[0].sens;
 48	rc = ebitmap_cpy(&dst->range.level[0].cat, &src->range.level[0].cat);
 49	if (rc)
 50		goto out;
 51
 52	dst->range.level[1].sens = src->range.level[1].sens;
 53	rc = ebitmap_cpy(&dst->range.level[1].cat, &src->range.level[1].cat);
 54	if (rc)
 55		ebitmap_destroy(&dst->range.level[0].cat);
 56out:
 57	return rc;
 58}
 59
 60/*
 61 * Sets both levels in the MLS range of 'dst' to the low level of 'src'.
 62 */
 63static inline int mls_context_cpy_low(struct context *dst,
 64				      const struct context *src)
 65{
 66	int rc;
 67
 68	dst->range.level[0].sens = src->range.level[0].sens;
 69	rc = ebitmap_cpy(&dst->range.level[0].cat, &src->range.level[0].cat);
 70	if (rc)
 71		goto out;
 72
 73	dst->range.level[1].sens = src->range.level[0].sens;
 74	rc = ebitmap_cpy(&dst->range.level[1].cat, &src->range.level[0].cat);
 75	if (rc)
 76		ebitmap_destroy(&dst->range.level[0].cat);
 77out:
 78	return rc;
 79}
 80
 81/*
 82 * Sets both levels in the MLS range of 'dst' to the high level of 'src'.
 83 */
 84static inline int mls_context_cpy_high(struct context *dst,
 85				       const struct context *src)
 86{
 87	int rc;
 88
 89	dst->range.level[0].sens = src->range.level[1].sens;
 90	rc = ebitmap_cpy(&dst->range.level[0].cat, &src->range.level[1].cat);
 91	if (rc)
 92		goto out;
 93
 94	dst->range.level[1].sens = src->range.level[1].sens;
 95	rc = ebitmap_cpy(&dst->range.level[1].cat, &src->range.level[1].cat);
 96	if (rc)
 97		ebitmap_destroy(&dst->range.level[0].cat);
 98out:
 99	return rc;
100}
101
102static inline int mls_context_glblub(struct context *dst,
103				     const struct context *c1,
104				     const struct context *c2)
105{
106	struct mls_range *dr = &dst->range;
107	const struct mls_range *r1 = &c1->range, *r2 = &c2->range;
108	int rc = 0;
109
110	if (r1->level[1].sens < r2->level[0].sens ||
111	    r2->level[1].sens < r1->level[0].sens)
112		/* These ranges have no common sensitivities */
113		return -EINVAL;
114
115	/* Take the greatest of the low */
116	dr->level[0].sens = max(r1->level[0].sens, r2->level[0].sens);
117
118	/* Take the least of the high */
119	dr->level[1].sens = min(r1->level[1].sens, r2->level[1].sens);
120
121	rc = ebitmap_and(&dr->level[0].cat, &r1->level[0].cat,
122			 &r2->level[0].cat);
123	if (rc)
124		goto out;
125
126	rc = ebitmap_and(&dr->level[1].cat, &r1->level[1].cat,
127			 &r2->level[1].cat);
128	if (rc)
129		goto out;
130
131out:
132	return rc;
133}
134
135static inline bool mls_context_equal(const struct context *c1,
136				     const struct context *c2)
137{
138	return ((c1->range.level[0].sens == c2->range.level[0].sens) &&
139		ebitmap_equal(&c1->range.level[0].cat, &c2->range.level[0].cat) &&
140		(c1->range.level[1].sens == c2->range.level[1].sens) &&
141		ebitmap_equal(&c1->range.level[1].cat, &c2->range.level[1].cat));
142}
143
144static inline void mls_context_destroy(struct context *c)
145{
146	ebitmap_destroy(&c->range.level[0].cat);
147	ebitmap_destroy(&c->range.level[1].cat);
148	mls_context_init(c);
149}
150
151static inline void context_init(struct context *c)
152{
153	memset(c, 0, sizeof(*c));
154}
155
156static inline int context_cpy(struct context *dst, const struct context *src)
157{
158	int rc;
159
160	dst->user = src->user;
161	dst->role = src->role;
162	dst->type = src->type;
163	if (src->str) {
164		dst->str = kstrdup(src->str, GFP_ATOMIC);
165		if (!dst->str)
166			return -ENOMEM;
167		dst->len = src->len;
168	} else {
169		dst->str = NULL;
170		dst->len = 0;
171	}
172	rc = mls_context_cpy(dst, src);
173	if (rc) {
174		kfree(dst->str);
175		dst->str = NULL;
176		dst->len = 0;
177		return rc;
178	}
179	return 0;
180}
181
182static inline void context_destroy(struct context *c)
183{
184	c->user = c->role = c->type = 0;
185	kfree(c->str);
186	c->str = NULL;
187	c->len = 0;
188	mls_context_destroy(c);
189}
190
191static inline bool context_equal(const struct context *c1,
192				 const struct context *c2)
193{
194	if (c1->len && c2->len)
195		return (c1->len == c2->len && !strcmp(c1->str, c2->str));
196	if (c1->len || c2->len)
197		return 0;
198	return ((c1->user == c2->user) && (c1->role == c2->role) &&
199		(c1->type == c2->type) && mls_context_equal(c1, c2));
200}
201
202u32 context_compute_hash(const struct context *c);
203
204#endif /* _SS_CONTEXT_H_ */