1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Copyright (C) 2020-2024 Microsoft Corporation. All rights reserved.
4 */
5
6 #include <linux/errno.h>
7 #include <linux/verification.h>
8
9 #include "ipe.h"
10 #include "eval.h"
11 #include "fs.h"
12 #include "policy.h"
13 #include "policy_parser.h"
14 #include "audit.h"
15
16 /* lock for synchronizing writers across ipe policy */
17 DEFINE_MUTEX(ipe_policy_lock);
18
19 /**
20 * ver_to_u64() - Convert an internal ipe_policy_version to a u64.
21 * @p: Policy to extract the version from.
22 *
23 * Bits (LSB is index 0):
24 * [48,32] -> Major
25 * [32,16] -> Minor
26 * [16, 0] -> Revision
27 *
28 * Return: u64 version of the embedded version structure.
29 */
ver_to_u64(const struct ipe_policy * const p)30 static inline u64 ver_to_u64(const struct ipe_policy *const p)
31 {
32 u64 r;
33
34 r = (((u64)p->parsed->version.major) << 32)
35 | (((u64)p->parsed->version.minor) << 16)
36 | ((u64)(p->parsed->version.rev));
37
38 return r;
39 }
40
41 /**
42 * ipe_free_policy() - Deallocate a given IPE policy.
43 * @p: Supplies the policy to free.
44 *
45 * Safe to call on IS_ERR/NULL.
46 */
ipe_free_policy(struct ipe_policy * p)47 void ipe_free_policy(struct ipe_policy *p)
48 {
49 if (IS_ERR_OR_NULL(p))
50 return;
51
52 ipe_del_policyfs_node(p);
53 ipe_free_parsed_policy(p->parsed);
54 /*
55 * p->text is allocated only when p->pkcs7 is not NULL
56 * otherwise it points to the plaintext data inside the pkcs7
57 */
58 if (!p->pkcs7)
59 kfree(p->text);
60 kfree(p->pkcs7);
61 kfree(p);
62 }
63
set_pkcs7_data(void * ctx,const void * data,size_t len,size_t asn1hdrlen __always_unused)64 static int set_pkcs7_data(void *ctx, const void *data, size_t len,
65 size_t asn1hdrlen __always_unused)
66 {
67 struct ipe_policy *p = ctx;
68
69 p->text = (const char *)data;
70 p->textlen = len;
71
72 return 0;
73 }
74
75 /**
76 * ipe_update_policy() - parse a new policy and replace old with it.
77 * @root: Supplies a pointer to the securityfs inode saved the policy.
78 * @text: Supplies a pointer to the plain text policy.
79 * @textlen: Supplies the length of @text.
80 * @pkcs7: Supplies a pointer to a buffer containing a pkcs7 message.
81 * @pkcs7len: Supplies the length of @pkcs7len.
82 *
83 * @text/@textlen is mutually exclusive with @pkcs7/@pkcs7len - see
84 * ipe_new_policy.
85 *
86 * Context: Requires root->i_rwsem to be held.
87 * Return: %0 on success. If an error occurs, the function will return
88 * the -errno.
89 */
ipe_update_policy(struct inode * root,const char * text,size_t textlen,const char * pkcs7,size_t pkcs7len)90 int ipe_update_policy(struct inode *root, const char *text, size_t textlen,
91 const char *pkcs7, size_t pkcs7len)
92 {
93 struct ipe_policy *old, *ap, *new = NULL;
94 int rc = 0;
95
96 old = (struct ipe_policy *)root->i_private;
97 if (!old)
98 return -ENOENT;
99
100 new = ipe_new_policy(text, textlen, pkcs7, pkcs7len);
101 if (IS_ERR(new))
102 return PTR_ERR(new);
103
104 if (strcmp(new->parsed->name, old->parsed->name)) {
105 rc = -EINVAL;
106 goto err;
107 }
108
109 if (ver_to_u64(old) > ver_to_u64(new)) {
110 rc = -EINVAL;
111 goto err;
112 }
113
114 root->i_private = new;
115 swap(new->policyfs, old->policyfs);
116 ipe_audit_policy_load(new);
117
118 mutex_lock(&ipe_policy_lock);
119 ap = rcu_dereference_protected(ipe_active_policy,
120 lockdep_is_held(&ipe_policy_lock));
121 if (old == ap) {
122 rcu_assign_pointer(ipe_active_policy, new);
123 mutex_unlock(&ipe_policy_lock);
124 ipe_audit_policy_activation(old, new);
125 } else {
126 mutex_unlock(&ipe_policy_lock);
127 }
128 synchronize_rcu();
129 ipe_free_policy(old);
130
131 return 0;
132 err:
133 ipe_free_policy(new);
134 return rc;
135 }
136
137 /**
138 * ipe_new_policy() - Allocate and parse an ipe_policy structure.
139 *
140 * @text: Supplies a pointer to the plain-text policy to parse.
141 * @textlen: Supplies the length of @text.
142 * @pkcs7: Supplies a pointer to a pkcs7-signed IPE policy.
143 * @pkcs7len: Supplies the length of @pkcs7.
144 *
145 * @text/@textlen Should be NULL/0 if @pkcs7/@pkcs7len is set.
146 *
147 * Return:
148 * * a pointer to the ipe_policy structure - Success
149 * * %-EBADMSG - Policy is invalid
150 * * %-ENOMEM - Out of memory (OOM)
151 * * %-ERANGE - Policy version number overflow
152 * * %-EINVAL - Policy version parsing error
153 */
ipe_new_policy(const char * text,size_t textlen,const char * pkcs7,size_t pkcs7len)154 struct ipe_policy *ipe_new_policy(const char *text, size_t textlen,
155 const char *pkcs7, size_t pkcs7len)
156 {
157 struct ipe_policy *new = NULL;
158 int rc = 0;
159
160 new = kzalloc(sizeof(*new), GFP_KERNEL);
161 if (!new)
162 return ERR_PTR(-ENOMEM);
163
164 if (!text) {
165 new->pkcs7len = pkcs7len;
166 new->pkcs7 = kmemdup(pkcs7, pkcs7len, GFP_KERNEL);
167 if (!new->pkcs7) {
168 rc = -ENOMEM;
169 goto err;
170 }
171
172 rc = verify_pkcs7_signature(NULL, 0, new->pkcs7, pkcs7len, NULL,
173 VERIFYING_UNSPECIFIED_SIGNATURE,
174 set_pkcs7_data, new);
175 if (rc)
176 goto err;
177 } else {
178 new->textlen = textlen;
179 new->text = kstrdup(text, GFP_KERNEL);
180 if (!new->text) {
181 rc = -ENOMEM;
182 goto err;
183 }
184 }
185
186 rc = ipe_parse_policy(new);
187 if (rc)
188 goto err;
189
190 return new;
191 err:
192 ipe_free_policy(new);
193 return ERR_PTR(rc);
194 }
195
196 /**
197 * ipe_set_active_pol() - Make @p the active policy.
198 * @p: Supplies a pointer to the policy to make active.
199 *
200 * Context: Requires root->i_rwsem, which i_private has the policy, to be held.
201 * Return:
202 * * %0 - Success
203 * * %-EINVAL - New active policy version is invalid
204 */
ipe_set_active_pol(const struct ipe_policy * p)205 int ipe_set_active_pol(const struct ipe_policy *p)
206 {
207 struct ipe_policy *ap = NULL;
208
209 mutex_lock(&ipe_policy_lock);
210
211 ap = rcu_dereference_protected(ipe_active_policy,
212 lockdep_is_held(&ipe_policy_lock));
213 if (ap == p) {
214 mutex_unlock(&ipe_policy_lock);
215 return 0;
216 }
217 if (ap && ver_to_u64(ap) > ver_to_u64(p)) {
218 mutex_unlock(&ipe_policy_lock);
219 return -EINVAL;
220 }
221
222 rcu_assign_pointer(ipe_active_policy, p);
223 ipe_audit_policy_activation(ap, p);
224 mutex_unlock(&ipe_policy_lock);
225
226 return 0;
227 }
228