1 /* Instantiate a public key crypto key from an X.509 Certificate 2 * 3 * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved. 4 * Written by David Howells (dhowells@redhat.com) 5 * 6 * This program is free software; you can redistribute it and/or 7 * modify it under the terms of the GNU General Public Licence 8 * as published by the Free Software Foundation; either version 9 * 2 of the Licence, or (at your option) any later version. 10 */ 11 12 #define pr_fmt(fmt) "X.509: "fmt 13 #include <linux/module.h> 14 #include <linux/kernel.h> 15 #include <linux/slab.h> 16 #include <keys/asymmetric-subtype.h> 17 #include <keys/asymmetric-parser.h> 18 #include <keys/system_keyring.h> 19 #include <crypto/hash.h> 20 #include "asymmetric_keys.h" 21 #include "x509_parser.h" 22 23 /* 24 * Set up the signature parameters in an X.509 certificate. This involves 25 * digesting the signed data and extracting the signature. 26 */ 27 int x509_get_sig_params(struct x509_certificate *cert) 28 { 29 struct public_key_signature *sig = cert->sig; 30 struct crypto_shash *tfm; 31 struct shash_desc *desc; 32 size_t desc_size; 33 int ret; 34 35 pr_devel("==>%s()\n", __func__); 36 37 if (!cert->pub->pkey_algo) 38 cert->unsupported_key = true; 39 40 if (!sig->pkey_algo) 41 cert->unsupported_sig = true; 42 43 /* We check the hash if we can - even if we can't then verify it */ 44 if (!sig->hash_algo) { 45 cert->unsupported_sig = true; 46 return 0; 47 } 48 49 sig->s = kmemdup(cert->raw_sig, cert->raw_sig_size, GFP_KERNEL); 50 if (!sig->s) 51 return -ENOMEM; 52 53 sig->s_size = cert->raw_sig_size; 54 55 /* Allocate the hashing algorithm we're going to need and find out how 56 * big the hash operational data will be. 57 */ 58 tfm = crypto_alloc_shash(sig->hash_algo, 0, 0); 59 if (IS_ERR(tfm)) { 60 if (PTR_ERR(tfm) == -ENOENT) { 61 cert->unsupported_sig = true; 62 return 0; 63 } 64 return PTR_ERR(tfm); 65 } 66 67 desc_size = crypto_shash_descsize(tfm) + sizeof(*desc); 68 sig->digest_size = crypto_shash_digestsize(tfm); 69 70 ret = -ENOMEM; 71 sig->digest = kmalloc(sig->digest_size, GFP_KERNEL); 72 if (!sig->digest) 73 goto error; 74 75 desc = kzalloc(desc_size, GFP_KERNEL); 76 if (!desc) 77 goto error; 78 79 desc->tfm = tfm; 80 desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP; 81 82 ret = crypto_shash_init(desc); 83 if (ret < 0) 84 goto error_2; 85 might_sleep(); 86 ret = crypto_shash_finup(desc, cert->tbs, cert->tbs_size, sig->digest); 87 if (ret < 0) 88 goto error_2; 89 90 ret = is_hash_blacklisted(sig->digest, sig->digest_size, "tbs"); 91 if (ret == -EKEYREJECTED) { 92 pr_err("Cert %*phN is blacklisted\n", 93 sig->digest_size, sig->digest); 94 cert->blacklisted = true; 95 ret = 0; 96 } 97 98 error_2: 99 kfree(desc); 100 error: 101 crypto_free_shash(tfm); 102 pr_devel("<==%s() = %d\n", __func__, ret); 103 return ret; 104 } 105 106 /* 107 * Check for self-signedness in an X.509 cert and if found, check the signature 108 * immediately if we can. 109 */ 110 int x509_check_for_self_signed(struct x509_certificate *cert) 111 { 112 int ret = 0; 113 114 pr_devel("==>%s()\n", __func__); 115 116 if (cert->raw_subject_size != cert->raw_issuer_size || 117 memcmp(cert->raw_subject, cert->raw_issuer, 118 cert->raw_issuer_size) != 0) 119 goto not_self_signed; 120 121 if (cert->sig->auth_ids[0] || cert->sig->auth_ids[1]) { 122 /* If the AKID is present it may have one or two parts. If 123 * both are supplied, both must match. 124 */ 125 bool a = asymmetric_key_id_same(cert->skid, cert->sig->auth_ids[1]); 126 bool b = asymmetric_key_id_same(cert->id, cert->sig->auth_ids[0]); 127 128 if (!a && !b) 129 goto not_self_signed; 130 131 ret = -EKEYREJECTED; 132 if (((a && !b) || (b && !a)) && 133 cert->sig->auth_ids[0] && cert->sig->auth_ids[1]) 134 goto out; 135 } 136 137 ret = -EKEYREJECTED; 138 if (cert->pub->pkey_algo != cert->sig->pkey_algo) 139 goto out; 140 141 ret = public_key_verify_signature(cert->pub, cert->sig); 142 if (ret < 0) { 143 if (ret == -ENOPKG) { 144 cert->unsupported_sig = true; 145 ret = 0; 146 } 147 goto out; 148 } 149 150 pr_devel("Cert Self-signature verified"); 151 cert->self_signed = true; 152 153 out: 154 pr_devel("<==%s() = %d\n", __func__, ret); 155 return ret; 156 157 not_self_signed: 158 pr_devel("<==%s() = 0 [not]\n", __func__); 159 return 0; 160 } 161 162 /* 163 * Attempt to parse a data blob for a key as an X509 certificate. 164 */ 165 static int x509_key_preparse(struct key_preparsed_payload *prep) 166 { 167 struct asymmetric_key_ids *kids; 168 struct x509_certificate *cert; 169 const char *q; 170 size_t srlen, sulen; 171 char *desc = NULL, *p; 172 int ret; 173 174 cert = x509_cert_parse(prep->data, prep->datalen); 175 if (IS_ERR(cert)) 176 return PTR_ERR(cert); 177 178 pr_devel("Cert Issuer: %s\n", cert->issuer); 179 pr_devel("Cert Subject: %s\n", cert->subject); 180 181 if (cert->unsupported_key) { 182 ret = -ENOPKG; 183 goto error_free_cert; 184 } 185 186 pr_devel("Cert Key Algo: %s\n", cert->pub->pkey_algo); 187 pr_devel("Cert Valid period: %lld-%lld\n", cert->valid_from, cert->valid_to); 188 189 cert->pub->id_type = "X509"; 190 191 if (cert->unsupported_sig) { 192 public_key_signature_free(cert->sig); 193 cert->sig = NULL; 194 } else { 195 pr_devel("Cert Signature: %s + %s\n", 196 cert->sig->pkey_algo, cert->sig->hash_algo); 197 } 198 199 /* Don't permit addition of blacklisted keys */ 200 ret = -EKEYREJECTED; 201 if (cert->blacklisted) 202 goto error_free_cert; 203 204 /* Propose a description */ 205 sulen = strlen(cert->subject); 206 if (cert->raw_skid) { 207 srlen = cert->raw_skid_size; 208 q = cert->raw_skid; 209 } else { 210 srlen = cert->raw_serial_size; 211 q = cert->raw_serial; 212 } 213 214 ret = -ENOMEM; 215 desc = kmalloc(sulen + 2 + srlen * 2 + 1, GFP_KERNEL); 216 if (!desc) 217 goto error_free_cert; 218 p = memcpy(desc, cert->subject, sulen); 219 p += sulen; 220 *p++ = ':'; 221 *p++ = ' '; 222 p = bin2hex(p, q, srlen); 223 *p = 0; 224 225 kids = kmalloc(sizeof(struct asymmetric_key_ids), GFP_KERNEL); 226 if (!kids) 227 goto error_free_desc; 228 kids->id[0] = cert->id; 229 kids->id[1] = cert->skid; 230 231 /* We're pinning the module by being linked against it */ 232 __module_get(public_key_subtype.owner); 233 prep->payload.data[asym_subtype] = &public_key_subtype; 234 prep->payload.data[asym_key_ids] = kids; 235 prep->payload.data[asym_crypto] = cert->pub; 236 prep->payload.data[asym_auth] = cert->sig; 237 prep->description = desc; 238 prep->quotalen = 100; 239 240 /* We've finished with the certificate */ 241 cert->pub = NULL; 242 cert->id = NULL; 243 cert->skid = NULL; 244 cert->sig = NULL; 245 desc = NULL; 246 ret = 0; 247 248 error_free_desc: 249 kfree(desc); 250 error_free_cert: 251 x509_free_certificate(cert); 252 return ret; 253 } 254 255 static struct asymmetric_key_parser x509_key_parser = { 256 .owner = THIS_MODULE, 257 .name = "x509", 258 .parse = x509_key_preparse, 259 }; 260 261 /* 262 * Module stuff 263 */ 264 static int __init x509_key_init(void) 265 { 266 return register_asymmetric_key_parser(&x509_key_parser); 267 } 268 269 static void __exit x509_key_exit(void) 270 { 271 unregister_asymmetric_key_parser(&x509_key_parser); 272 } 273 274 module_init(x509_key_init); 275 module_exit(x509_key_exit); 276 277 MODULE_DESCRIPTION("X.509 certificate parser"); 278 MODULE_AUTHOR("Red Hat, Inc."); 279 MODULE_LICENSE("GPL"); 280