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_digest(desc, cert->tbs, cert->tbs_size, sig->digest); 83 if (ret < 0) 84 goto error_2; 85 86 ret = is_hash_blacklisted(sig->digest, sig->digest_size, "tbs"); 87 if (ret == -EKEYREJECTED) { 88 pr_err("Cert %*phN is blacklisted\n", 89 sig->digest_size, sig->digest); 90 cert->blacklisted = true; 91 ret = 0; 92 } 93 94 error_2: 95 kfree(desc); 96 error: 97 crypto_free_shash(tfm); 98 pr_devel("<==%s() = %d\n", __func__, ret); 99 return ret; 100 } 101 102 /* 103 * Check for self-signedness in an X.509 cert and if found, check the signature 104 * immediately if we can. 105 */ 106 int x509_check_for_self_signed(struct x509_certificate *cert) 107 { 108 int ret = 0; 109 110 pr_devel("==>%s()\n", __func__); 111 112 if (cert->raw_subject_size != cert->raw_issuer_size || 113 memcmp(cert->raw_subject, cert->raw_issuer, 114 cert->raw_issuer_size) != 0) 115 goto not_self_signed; 116 117 if (cert->sig->auth_ids[0] || cert->sig->auth_ids[1]) { 118 /* If the AKID is present it may have one or two parts. If 119 * both are supplied, both must match. 120 */ 121 bool a = asymmetric_key_id_same(cert->skid, cert->sig->auth_ids[1]); 122 bool b = asymmetric_key_id_same(cert->id, cert->sig->auth_ids[0]); 123 124 if (!a && !b) 125 goto not_self_signed; 126 127 ret = -EKEYREJECTED; 128 if (((a && !b) || (b && !a)) && 129 cert->sig->auth_ids[0] && cert->sig->auth_ids[1]) 130 goto out; 131 } 132 133 ret = -EKEYREJECTED; 134 if (strcmp(cert->pub->pkey_algo, cert->sig->pkey_algo) != 0) 135 goto out; 136 137 ret = public_key_verify_signature(cert->pub, cert->sig); 138 if (ret < 0) { 139 if (ret == -ENOPKG) { 140 cert->unsupported_sig = true; 141 ret = 0; 142 } 143 goto out; 144 } 145 146 pr_devel("Cert Self-signature verified"); 147 cert->self_signed = true; 148 149 out: 150 pr_devel("<==%s() = %d\n", __func__, ret); 151 return ret; 152 153 not_self_signed: 154 pr_devel("<==%s() = 0 [not]\n", __func__); 155 return 0; 156 } 157 158 /* 159 * Attempt to parse a data blob for a key as an X509 certificate. 160 */ 161 static int x509_key_preparse(struct key_preparsed_payload *prep) 162 { 163 struct asymmetric_key_ids *kids; 164 struct x509_certificate *cert; 165 const char *q; 166 size_t srlen, sulen; 167 char *desc = NULL, *p; 168 int ret; 169 170 cert = x509_cert_parse(prep->data, prep->datalen); 171 if (IS_ERR(cert)) 172 return PTR_ERR(cert); 173 174 pr_devel("Cert Issuer: %s\n", cert->issuer); 175 pr_devel("Cert Subject: %s\n", cert->subject); 176 177 if (cert->unsupported_key) { 178 ret = -ENOPKG; 179 goto error_free_cert; 180 } 181 182 pr_devel("Cert Key Algo: %s\n", cert->pub->pkey_algo); 183 pr_devel("Cert Valid period: %lld-%lld\n", cert->valid_from, cert->valid_to); 184 185 cert->pub->id_type = "X509"; 186 187 if (cert->unsupported_sig) { 188 public_key_signature_free(cert->sig); 189 cert->sig = NULL; 190 } else { 191 pr_devel("Cert Signature: %s + %s\n", 192 cert->sig->pkey_algo, cert->sig->hash_algo); 193 } 194 195 /* Don't permit addition of blacklisted keys */ 196 ret = -EKEYREJECTED; 197 if (cert->blacklisted) 198 goto error_free_cert; 199 200 /* Propose a description */ 201 sulen = strlen(cert->subject); 202 if (cert->raw_skid) { 203 srlen = cert->raw_skid_size; 204 q = cert->raw_skid; 205 } else { 206 srlen = cert->raw_serial_size; 207 q = cert->raw_serial; 208 } 209 210 ret = -ENOMEM; 211 desc = kmalloc(sulen + 2 + srlen * 2 + 1, GFP_KERNEL); 212 if (!desc) 213 goto error_free_cert; 214 p = memcpy(desc, cert->subject, sulen); 215 p += sulen; 216 *p++ = ':'; 217 *p++ = ' '; 218 p = bin2hex(p, q, srlen); 219 *p = 0; 220 221 kids = kmalloc(sizeof(struct asymmetric_key_ids), GFP_KERNEL); 222 if (!kids) 223 goto error_free_desc; 224 kids->id[0] = cert->id; 225 kids->id[1] = cert->skid; 226 227 /* We're pinning the module by being linked against it */ 228 __module_get(public_key_subtype.owner); 229 prep->payload.data[asym_subtype] = &public_key_subtype; 230 prep->payload.data[asym_key_ids] = kids; 231 prep->payload.data[asym_crypto] = cert->pub; 232 prep->payload.data[asym_auth] = cert->sig; 233 prep->description = desc; 234 prep->quotalen = 100; 235 236 /* We've finished with the certificate */ 237 cert->pub = NULL; 238 cert->id = NULL; 239 cert->skid = NULL; 240 cert->sig = NULL; 241 desc = NULL; 242 ret = 0; 243 244 error_free_desc: 245 kfree(desc); 246 error_free_cert: 247 x509_free_certificate(cert); 248 return ret; 249 } 250 251 static struct asymmetric_key_parser x509_key_parser = { 252 .owner = THIS_MODULE, 253 .name = "x509", 254 .parse = x509_key_preparse, 255 }; 256 257 /* 258 * Module stuff 259 */ 260 static int __init x509_key_init(void) 261 { 262 return register_asymmetric_key_parser(&x509_key_parser); 263 } 264 265 static void __exit x509_key_exit(void) 266 { 267 unregister_asymmetric_key_parser(&x509_key_parser); 268 } 269 270 module_init(x509_key_init); 271 module_exit(x509_key_exit); 272 273 MODULE_DESCRIPTION("X.509 certificate parser"); 274 MODULE_AUTHOR("Red Hat, Inc."); 275 MODULE_LICENSE("GPL"); 276