1 /* In-software asymmetric public-key crypto subtype
2 *
3 * See Documentation/crypto/asymmetric-keys.txt
4 *
5 * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
6 * Written by David Howells (dhowells@redhat.com)
7 *
8 * This program is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU General Public Licence
10 * as published by the Free Software Foundation; either version
11 * 2 of the Licence, or (at your option) any later version.
12 */
13
14 #define pr_fmt(fmt) "PKEY: "fmt
15 #include <linux/module.h>
16 #include <linux/export.h>
17 #include <linux/kernel.h>
18 #include <linux/slab.h>
19 #include <linux/seq_file.h>
20 #include <linux/scatterlist.h>
21 #include <keys/asymmetric-subtype.h>
22 #include <crypto/public_key.h>
23 #include <crypto/akcipher.h>
24
25 MODULE_LICENSE("GPL");
26
27 /*
28 * Provide a part of a description of the key for /proc/keys.
29 */
public_key_describe(const struct key * asymmetric_key,struct seq_file * m)30 static void public_key_describe(const struct key *asymmetric_key,
31 struct seq_file *m)
32 {
33 struct public_key *key = asymmetric_key->payload.data[asym_crypto];
34
35 if (key)
36 seq_printf(m, "%s.%s", key->id_type, key->pkey_algo);
37 }
38
39 /*
40 * Destroy a public key algorithm key.
41 */
public_key_free(struct public_key * key)42 void public_key_free(struct public_key *key)
43 {
44 if (key) {
45 kfree(key->key);
46 kfree(key);
47 }
48 }
49 EXPORT_SYMBOL_GPL(public_key_free);
50
51 /*
52 * Destroy a public key algorithm key.
53 */
public_key_destroy(void * payload0,void * payload3)54 static void public_key_destroy(void *payload0, void *payload3)
55 {
56 public_key_free(payload0);
57 public_key_signature_free(payload3);
58 }
59
60 struct public_key_completion {
61 struct completion completion;
62 int err;
63 };
64
public_key_verify_done(struct crypto_async_request * req,int err)65 static void public_key_verify_done(struct crypto_async_request *req, int err)
66 {
67 struct public_key_completion *compl = req->data;
68
69 if (err == -EINPROGRESS)
70 return;
71
72 compl->err = err;
73 complete(&compl->completion);
74 }
75
76 /*
77 * Verify a signature using a public key.
78 */
public_key_verify_signature(const struct public_key * pkey,const struct public_key_signature * sig)79 int public_key_verify_signature(const struct public_key *pkey,
80 const struct public_key_signature *sig)
81 {
82 struct public_key_completion compl;
83 struct crypto_akcipher *tfm;
84 struct akcipher_request *req;
85 struct scatterlist sig_sg, digest_sg;
86 const char *alg_name;
87 char alg_name_buf[CRYPTO_MAX_ALG_NAME];
88 void *output;
89 unsigned int outlen;
90 int ret = -ENOMEM;
91
92 pr_devel("==>%s()\n", __func__);
93
94 BUG_ON(!pkey);
95 BUG_ON(!sig);
96 BUG_ON(!sig->s);
97
98 if (!sig->digest)
99 return -ENOPKG;
100
101 alg_name = sig->pkey_algo;
102 if (strcmp(sig->pkey_algo, "rsa") == 0) {
103 /* The data wangled by the RSA algorithm is typically padded
104 * and encoded in some manner, such as EMSA-PKCS1-1_5 [RFC3447
105 * sec 8.2].
106 */
107 if (snprintf(alg_name_buf, CRYPTO_MAX_ALG_NAME,
108 "pkcs1pad(rsa,%s)", sig->hash_algo
109 ) >= CRYPTO_MAX_ALG_NAME)
110 return -EINVAL;
111 alg_name = alg_name_buf;
112 }
113
114 tfm = crypto_alloc_akcipher(alg_name, 0, 0);
115 if (IS_ERR(tfm))
116 return PTR_ERR(tfm);
117
118 req = akcipher_request_alloc(tfm, GFP_KERNEL);
119 if (!req)
120 goto error_free_tfm;
121
122 ret = crypto_akcipher_set_pub_key(tfm, pkey->key, pkey->keylen);
123 if (ret)
124 goto error_free_req;
125
126 ret = -ENOMEM;
127 outlen = crypto_akcipher_maxsize(tfm);
128 output = kmalloc(outlen, GFP_KERNEL);
129 if (!output)
130 goto error_free_req;
131
132 sg_init_one(&sig_sg, sig->s, sig->s_size);
133 sg_init_one(&digest_sg, output, outlen);
134 akcipher_request_set_crypt(req, &sig_sg, &digest_sg, sig->s_size,
135 outlen);
136 init_completion(&compl.completion);
137 akcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
138 CRYPTO_TFM_REQ_MAY_SLEEP,
139 public_key_verify_done, &compl);
140
141 /* Perform the verification calculation. This doesn't actually do the
142 * verification, but rather calculates the hash expected by the
143 * signature and returns that to us.
144 */
145 ret = crypto_akcipher_verify(req);
146 if ((ret == -EINPROGRESS) || (ret == -EBUSY)) {
147 wait_for_completion(&compl.completion);
148 ret = compl.err;
149 }
150 if (ret < 0)
151 goto out_free_output;
152
153 /* Do the actual verification step. */
154 if (req->dst_len != sig->digest_size ||
155 memcmp(sig->digest, output, sig->digest_size) != 0)
156 ret = -EKEYREJECTED;
157
158 out_free_output:
159 kfree(output);
160 error_free_req:
161 akcipher_request_free(req);
162 error_free_tfm:
163 crypto_free_akcipher(tfm);
164 pr_devel("<==%s() = %d\n", __func__, ret);
165 return ret;
166 }
167 EXPORT_SYMBOL_GPL(public_key_verify_signature);
168
public_key_verify_signature_2(const struct key * key,const struct public_key_signature * sig)169 static int public_key_verify_signature_2(const struct key *key,
170 const struct public_key_signature *sig)
171 {
172 const struct public_key *pk = key->payload.data[asym_crypto];
173 return public_key_verify_signature(pk, sig);
174 }
175
176 /*
177 * Public key algorithm asymmetric key subtype
178 */
179 struct asymmetric_key_subtype public_key_subtype = {
180 .owner = THIS_MODULE,
181 .name = "public_key",
182 .name_len = sizeof("public_key") - 1,
183 .describe = public_key_describe,
184 .destroy = public_key_destroy,
185 .verify_signature = public_key_verify_signature_2,
186 };
187 EXPORT_SYMBOL_GPL(public_key_subtype);
188