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 */ 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 */ 42 void public_key_destroy(void *payload) 43 { 44 struct public_key *key = payload; 45 46 if (key) 47 kfree(key->key); 48 kfree(key); 49 } 50 EXPORT_SYMBOL_GPL(public_key_destroy); 51 52 struct public_key_completion { 53 struct completion completion; 54 int err; 55 }; 56 57 static void public_key_verify_done(struct crypto_async_request *req, int err) 58 { 59 struct public_key_completion *compl = req->data; 60 61 if (err == -EINPROGRESS) 62 return; 63 64 compl->err = err; 65 complete(&compl->completion); 66 } 67 68 /* 69 * Verify a signature using a public key. 70 */ 71 int public_key_verify_signature(const struct public_key *pkey, 72 const struct public_key_signature *sig) 73 { 74 struct public_key_completion compl; 75 struct crypto_akcipher *tfm; 76 struct akcipher_request *req; 77 struct scatterlist sig_sg, digest_sg; 78 const char *alg_name; 79 char alg_name_buf[CRYPTO_MAX_ALG_NAME]; 80 void *output; 81 unsigned int outlen; 82 int ret = -ENOMEM; 83 84 pr_devel("==>%s()\n", __func__); 85 86 BUG_ON(!pkey); 87 BUG_ON(!sig); 88 BUG_ON(!sig->digest); 89 BUG_ON(!sig->s); 90 91 alg_name = sig->pkey_algo; 92 if (strcmp(sig->pkey_algo, "rsa") == 0) { 93 /* The data wangled by the RSA algorithm is typically padded 94 * and encoded in some manner, such as EMSA-PKCS1-1_5 [RFC3447 95 * sec 8.2]. 96 */ 97 if (snprintf(alg_name_buf, CRYPTO_MAX_ALG_NAME, 98 "pkcs1pad(rsa,%s)", sig->hash_algo 99 ) >= CRYPTO_MAX_ALG_NAME) 100 return -EINVAL; 101 alg_name = alg_name_buf; 102 } 103 104 tfm = crypto_alloc_akcipher(alg_name, 0, 0); 105 if (IS_ERR(tfm)) 106 return PTR_ERR(tfm); 107 108 req = akcipher_request_alloc(tfm, GFP_KERNEL); 109 if (!req) 110 goto error_free_tfm; 111 112 ret = crypto_akcipher_set_pub_key(tfm, pkey->key, pkey->keylen); 113 if (ret) 114 goto error_free_req; 115 116 outlen = crypto_akcipher_maxsize(tfm); 117 output = kmalloc(outlen, GFP_KERNEL); 118 if (!output) 119 goto error_free_req; 120 121 sg_init_one(&sig_sg, sig->s, sig->s_size); 122 sg_init_one(&digest_sg, output, outlen); 123 akcipher_request_set_crypt(req, &sig_sg, &digest_sg, sig->s_size, 124 outlen); 125 init_completion(&compl.completion); 126 akcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG | 127 CRYPTO_TFM_REQ_MAY_SLEEP, 128 public_key_verify_done, &compl); 129 130 /* Perform the verification calculation. This doesn't actually do the 131 * verification, but rather calculates the hash expected by the 132 * signature and returns that to us. 133 */ 134 ret = crypto_akcipher_verify(req); 135 if (ret == -EINPROGRESS) { 136 wait_for_completion(&compl.completion); 137 ret = compl.err; 138 } 139 if (ret < 0) 140 goto out_free_output; 141 142 /* Do the actual verification step. */ 143 if (req->dst_len != sig->digest_size || 144 memcmp(sig->digest, output, sig->digest_size) != 0) 145 ret = -EKEYREJECTED; 146 147 out_free_output: 148 kfree(output); 149 error_free_req: 150 akcipher_request_free(req); 151 error_free_tfm: 152 crypto_free_akcipher(tfm); 153 pr_devel("<==%s() = %d\n", __func__, ret); 154 return ret; 155 } 156 EXPORT_SYMBOL_GPL(public_key_verify_signature); 157 158 static int public_key_verify_signature_2(const struct key *key, 159 const struct public_key_signature *sig) 160 { 161 const struct public_key *pk = key->payload.data[asym_crypto]; 162 return public_key_verify_signature(pk, sig); 163 } 164 165 /* 166 * Public key algorithm asymmetric key subtype 167 */ 168 struct asymmetric_key_subtype public_key_subtype = { 169 .owner = THIS_MODULE, 170 .name = "public_key", 171 .name_len = sizeof("public_key") - 1, 172 .describe = public_key_describe, 173 .destroy = public_key_destroy, 174 .verify_signature = public_key_verify_signature_2, 175 }; 176 EXPORT_SYMBOL_GPL(public_key_subtype); 177