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_DESCRIPTION("In-software asymmetric public-key subtype"); 26 MODULE_AUTHOR("Red Hat, Inc."); 27 MODULE_LICENSE("GPL"); 28 29 /* 30 * Provide a part of a description of the key for /proc/keys. 31 */ 32 static void public_key_describe(const struct key *asymmetric_key, 33 struct seq_file *m) 34 { 35 struct public_key *key = asymmetric_key->payload.data[asym_crypto]; 36 37 if (key) 38 seq_printf(m, "%s.%s", key->id_type, key->pkey_algo); 39 } 40 41 /* 42 * Destroy a public key algorithm key. 43 */ 44 void public_key_free(struct public_key *key) 45 { 46 if (key) { 47 kfree(key->key); 48 kfree(key); 49 } 50 } 51 EXPORT_SYMBOL_GPL(public_key_free); 52 53 /* 54 * Destroy a public key algorithm key. 55 */ 56 static void public_key_destroy(void *payload0, void *payload3) 57 { 58 public_key_free(payload0); 59 public_key_signature_free(payload3); 60 } 61 62 /* 63 * Verify a signature using a public key. 64 */ 65 int public_key_verify_signature(const struct public_key *pkey, 66 const struct public_key_signature *sig) 67 { 68 struct crypto_wait cwait; 69 struct crypto_akcipher *tfm; 70 struct akcipher_request *req; 71 struct scatterlist sig_sg, digest_sg; 72 const char *alg_name; 73 char alg_name_buf[CRYPTO_MAX_ALG_NAME]; 74 void *output; 75 unsigned int outlen; 76 int ret = -ENOMEM; 77 78 pr_devel("==>%s()\n", __func__); 79 80 BUG_ON(!pkey); 81 BUG_ON(!sig); 82 BUG_ON(!sig->digest); 83 BUG_ON(!sig->s); 84 85 alg_name = sig->pkey_algo; 86 if (strcmp(sig->pkey_algo, "rsa") == 0) { 87 /* The data wangled by the RSA algorithm is typically padded 88 * and encoded in some manner, such as EMSA-PKCS1-1_5 [RFC3447 89 * sec 8.2]. 90 */ 91 if (snprintf(alg_name_buf, CRYPTO_MAX_ALG_NAME, 92 "pkcs1pad(rsa,%s)", sig->hash_algo 93 ) >= CRYPTO_MAX_ALG_NAME) 94 return -EINVAL; 95 alg_name = alg_name_buf; 96 } 97 98 tfm = crypto_alloc_akcipher(alg_name, 0, 0); 99 if (IS_ERR(tfm)) 100 return PTR_ERR(tfm); 101 102 req = akcipher_request_alloc(tfm, GFP_KERNEL); 103 if (!req) 104 goto error_free_tfm; 105 106 ret = crypto_akcipher_set_pub_key(tfm, pkey->key, pkey->keylen); 107 if (ret) 108 goto error_free_req; 109 110 ret = -ENOMEM; 111 outlen = crypto_akcipher_maxsize(tfm); 112 output = kmalloc(outlen, GFP_KERNEL); 113 if (!output) 114 goto error_free_req; 115 116 sg_init_one(&sig_sg, sig->s, sig->s_size); 117 sg_init_one(&digest_sg, output, outlen); 118 akcipher_request_set_crypt(req, &sig_sg, &digest_sg, sig->s_size, 119 outlen); 120 crypto_init_wait(&cwait); 121 akcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG | 122 CRYPTO_TFM_REQ_MAY_SLEEP, 123 crypto_req_done, &cwait); 124 125 /* Perform the verification calculation. This doesn't actually do the 126 * verification, but rather calculates the hash expected by the 127 * signature and returns that to us. 128 */ 129 ret = crypto_wait_req(crypto_akcipher_verify(req), &cwait); 130 if (ret < 0) 131 goto out_free_output; 132 133 /* Do the actual verification step. */ 134 if (req->dst_len != sig->digest_size || 135 memcmp(sig->digest, output, sig->digest_size) != 0) 136 ret = -EKEYREJECTED; 137 138 out_free_output: 139 kfree(output); 140 error_free_req: 141 akcipher_request_free(req); 142 error_free_tfm: 143 crypto_free_akcipher(tfm); 144 pr_devel("<==%s() = %d\n", __func__, ret); 145 return ret; 146 } 147 EXPORT_SYMBOL_GPL(public_key_verify_signature); 148 149 static int public_key_verify_signature_2(const struct key *key, 150 const struct public_key_signature *sig) 151 { 152 const struct public_key *pk = key->payload.data[asym_crypto]; 153 return public_key_verify_signature(pk, sig); 154 } 155 156 /* 157 * Public key algorithm asymmetric key subtype 158 */ 159 struct asymmetric_key_subtype public_key_subtype = { 160 .owner = THIS_MODULE, 161 .name = "public_key", 162 .name_len = sizeof("public_key") - 1, 163 .describe = public_key_describe, 164 .destroy = public_key_destroy, 165 .verify_signature = public_key_verify_signature_2, 166 }; 167 EXPORT_SYMBOL_GPL(public_key_subtype); 168