1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* Instantiate a public key crypto key from an X.509 Certificate 3 * 4 * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved. 5 * Written by David Howells (dhowells@redhat.com) 6 */ 7 8 #define pr_fmt(fmt) "X.509: "fmt 9 #include <linux/module.h> 10 #include <linux/kernel.h> 11 #include <linux/slab.h> 12 #include <keys/asymmetric-subtype.h> 13 #include <keys/asymmetric-parser.h> 14 #include <keys/system_keyring.h> 15 #include <crypto/hash.h> 16 #include "asymmetric_keys.h" 17 #include "x509_parser.h" 18 19 /* 20 * Set up the signature parameters in an X.509 certificate. This involves 21 * digesting the signed data and extracting the signature. 22 */ 23 int x509_get_sig_params(struct x509_certificate *cert) 24 { 25 struct public_key_signature *sig = cert->sig; 26 struct crypto_shash *tfm; 27 struct shash_desc *desc; 28 size_t desc_size; 29 int ret; 30 31 pr_devel("==>%s()\n", __func__); 32 33 sig->data = cert->tbs; 34 sig->data_size = cert->tbs_size; 35 36 if (!cert->pub->pkey_algo) 37 cert->unsupported_key = true; 38 39 if (!sig->pkey_algo) 40 cert->unsupported_sig = true; 41 42 /* We check the hash if we can - even if we can't then verify it */ 43 if (!sig->hash_algo) { 44 cert->unsupported_sig = true; 45 return 0; 46 } 47 48 sig->s = kmemdup(cert->raw_sig, cert->raw_sig_size, GFP_KERNEL); 49 if (!sig->s) 50 return -ENOMEM; 51 52 sig->s_size = cert->raw_sig_size; 53 54 /* Allocate the hashing algorithm we're going to need and find out how 55 * big the hash operational data will be. 56 */ 57 tfm = crypto_alloc_shash(sig->hash_algo, 0, 0); 58 if (IS_ERR(tfm)) { 59 if (PTR_ERR(tfm) == -ENOENT) { 60 cert->unsupported_sig = true; 61 return 0; 62 } 63 return PTR_ERR(tfm); 64 } 65 66 desc_size = crypto_shash_descsize(tfm) + sizeof(*desc); 67 sig->digest_size = crypto_shash_digestsize(tfm); 68 69 ret = -ENOMEM; 70 sig->digest = kmalloc(sig->digest_size, GFP_KERNEL); 71 if (!sig->digest) 72 goto error; 73 74 desc = kzalloc(desc_size, GFP_KERNEL); 75 if (!desc) 76 goto error; 77 78 desc->tfm = tfm; 79 80 ret = crypto_shash_digest(desc, cert->tbs, cert->tbs_size, sig->digest); 81 if (ret < 0) 82 goto error_2; 83 84 ret = is_hash_blacklisted(sig->digest, sig->digest_size, "tbs"); 85 if (ret == -EKEYREJECTED) { 86 pr_err("Cert %*phN is blacklisted\n", 87 sig->digest_size, sig->digest); 88 cert->blacklisted = true; 89 ret = 0; 90 } 91 92 error_2: 93 kfree(desc); 94 error: 95 crypto_free_shash(tfm); 96 pr_devel("<==%s() = %d\n", __func__, ret); 97 return ret; 98 } 99 100 /* 101 * Check for self-signedness in an X.509 cert and if found, check the signature 102 * immediately if we can. 103 */ 104 int x509_check_for_self_signed(struct x509_certificate *cert) 105 { 106 int ret = 0; 107 108 pr_devel("==>%s()\n", __func__); 109 110 if (cert->raw_subject_size != cert->raw_issuer_size || 111 memcmp(cert->raw_subject, cert->raw_issuer, 112 cert->raw_issuer_size) != 0) 113 goto not_self_signed; 114 115 if (cert->sig->auth_ids[0] || cert->sig->auth_ids[1]) { 116 /* If the AKID is present it may have one or two parts. If 117 * both are supplied, both must match. 118 */ 119 bool a = asymmetric_key_id_same(cert->skid, cert->sig->auth_ids[1]); 120 bool b = asymmetric_key_id_same(cert->id, cert->sig->auth_ids[0]); 121 122 if (!a && !b) 123 goto not_self_signed; 124 125 ret = -EKEYREJECTED; 126 if (((a && !b) || (b && !a)) && 127 cert->sig->auth_ids[0] && cert->sig->auth_ids[1]) 128 goto out; 129 } 130 131 ret = -EKEYREJECTED; 132 if (strcmp(cert->pub->pkey_algo, cert->sig->pkey_algo) != 0) 133 goto out; 134 135 ret = public_key_verify_signature(cert->pub, cert->sig); 136 if (ret < 0) { 137 if (ret == -ENOPKG) { 138 cert->unsupported_sig = true; 139 ret = 0; 140 } 141 goto out; 142 } 143 144 pr_devel("Cert Self-signature verified"); 145 cert->self_signed = true; 146 147 out: 148 pr_devel("<==%s() = %d\n", __func__, ret); 149 return ret; 150 151 not_self_signed: 152 pr_devel("<==%s() = 0 [not]\n", __func__); 153 return 0; 154 } 155 156 /* 157 * Attempt to parse a data blob for a key as an X509 certificate. 158 */ 159 static int x509_key_preparse(struct key_preparsed_payload *prep) 160 { 161 struct asymmetric_key_ids *kids; 162 struct x509_certificate *cert; 163 const char *q; 164 size_t srlen, sulen; 165 char *desc = NULL, *p; 166 int ret; 167 168 cert = x509_cert_parse(prep->data, prep->datalen); 169 if (IS_ERR(cert)) 170 return PTR_ERR(cert); 171 172 pr_devel("Cert Issuer: %s\n", cert->issuer); 173 pr_devel("Cert Subject: %s\n", cert->subject); 174 175 if (cert->unsupported_key) { 176 ret = -ENOPKG; 177 goto error_free_cert; 178 } 179 180 pr_devel("Cert Key Algo: %s\n", cert->pub->pkey_algo); 181 pr_devel("Cert Valid period: %lld-%lld\n", cert->valid_from, cert->valid_to); 182 183 cert->pub->id_type = "X509"; 184 185 if (cert->unsupported_sig) { 186 public_key_signature_free(cert->sig); 187 cert->sig = NULL; 188 } else { 189 pr_devel("Cert Signature: %s + %s\n", 190 cert->sig->pkey_algo, cert->sig->hash_algo); 191 } 192 193 /* Don't permit addition of blacklisted keys */ 194 ret = -EKEYREJECTED; 195 if (cert->blacklisted) 196 goto error_free_cert; 197 198 /* Propose a description */ 199 sulen = strlen(cert->subject); 200 if (cert->raw_skid) { 201 srlen = cert->raw_skid_size; 202 q = cert->raw_skid; 203 } else { 204 srlen = cert->raw_serial_size; 205 q = cert->raw_serial; 206 } 207 208 ret = -ENOMEM; 209 desc = kmalloc(sulen + 2 + srlen * 2 + 1, GFP_KERNEL); 210 if (!desc) 211 goto error_free_cert; 212 p = memcpy(desc, cert->subject, sulen); 213 p += sulen; 214 *p++ = ':'; 215 *p++ = ' '; 216 p = bin2hex(p, q, srlen); 217 *p = 0; 218 219 kids = kmalloc(sizeof(struct asymmetric_key_ids), GFP_KERNEL); 220 if (!kids) 221 goto error_free_desc; 222 kids->id[0] = cert->id; 223 kids->id[1] = cert->skid; 224 225 /* We're pinning the module by being linked against it */ 226 __module_get(public_key_subtype.owner); 227 prep->payload.data[asym_subtype] = &public_key_subtype; 228 prep->payload.data[asym_key_ids] = kids; 229 prep->payload.data[asym_crypto] = cert->pub; 230 prep->payload.data[asym_auth] = cert->sig; 231 prep->description = desc; 232 prep->quotalen = 100; 233 234 /* We've finished with the certificate */ 235 cert->pub = NULL; 236 cert->id = NULL; 237 cert->skid = NULL; 238 cert->sig = NULL; 239 desc = NULL; 240 ret = 0; 241 242 error_free_desc: 243 kfree(desc); 244 error_free_cert: 245 x509_free_certificate(cert); 246 return ret; 247 } 248 249 static struct asymmetric_key_parser x509_key_parser = { 250 .owner = THIS_MODULE, 251 .name = "x509", 252 .parse = x509_key_preparse, 253 }; 254 255 /* 256 * Module stuff 257 */ 258 static int __init x509_key_init(void) 259 { 260 return register_asymmetric_key_parser(&x509_key_parser); 261 } 262 263 static void __exit x509_key_exit(void) 264 { 265 unregister_asymmetric_key_parser(&x509_key_parser); 266 } 267 268 module_init(x509_key_init); 269 module_exit(x509_key_exit); 270 271 MODULE_DESCRIPTION("X.509 certificate parser"); 272 MODULE_AUTHOR("Red Hat, Inc."); 273 MODULE_LICENSE("GPL"); 274