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 <crypto/hash.h> 10 #include <keys/asymmetric-parser.h> 11 #include <keys/asymmetric-subtype.h> 12 #include <keys/system_keyring.h> 13 #include <linux/module.h> 14 #include <linux/kernel.h> 15 #include <linux/slab.h> 16 #include <linux/string.h> 17 #include "asymmetric_keys.h" 18 #include "x509_parser.h" 19 20 /* 21 * Set up the signature parameters in an X.509 certificate. This involves 22 * digesting the signed data and extracting the signature. 23 */ 24 int x509_get_sig_params(struct x509_certificate *cert) 25 { 26 struct public_key_signature *sig = cert->sig; 27 struct crypto_shash *tfm; 28 struct shash_desc *desc; 29 size_t desc_size; 30 int ret; 31 32 pr_devel("==>%s()\n", __func__); 33 34 /* Calculate a SHA256 hash of the TBS and check it against the 35 * blacklist. 36 */ 37 sha256(cert->tbs, cert->tbs_size, cert->sha256); 38 ret = is_hash_blacklisted(cert->sha256, sizeof(cert->sha256), 39 BLACKLIST_HASH_X509_TBS); 40 if (ret == -EKEYREJECTED) { 41 pr_err("Cert %*phN is blacklisted\n", 42 (int)sizeof(cert->sha256), cert->sha256); 43 cert->blacklisted = true; 44 ret = 0; 45 } 46 47 sig->s = kmemdup(cert->raw_sig, cert->raw_sig_size, GFP_KERNEL); 48 if (!sig->s) 49 return -ENOMEM; 50 51 sig->s_size = cert->raw_sig_size; 52 53 if (sig->algo_takes_data) { 54 /* The signature algorithm does whatever passes for hashing. */ 55 sig->m = (u8 *)cert->tbs; 56 sig->m_size = cert->tbs_size; 57 sig->m_free = false; 58 goto out; 59 } 60 61 /* Allocate the hashing algorithm we're going to need and find out how 62 * big the hash operational data will be. 63 */ 64 tfm = crypto_alloc_shash(sig->hash_algo, 0, 0); 65 if (IS_ERR(tfm)) { 66 if (PTR_ERR(tfm) == -ENOENT) { 67 cert->unsupported_sig = true; 68 return 0; 69 } 70 return PTR_ERR(tfm); 71 } 72 73 desc_size = crypto_shash_descsize(tfm) + sizeof(*desc); 74 sig->m_size = crypto_shash_digestsize(tfm); 75 76 ret = -ENOMEM; 77 sig->m = kmalloc(sig->m_size, GFP_KERNEL); 78 if (!sig->m) 79 goto error; 80 sig->m_free = true; 81 82 desc = kzalloc(desc_size, GFP_KERNEL); 83 if (!desc) 84 goto error; 85 86 desc->tfm = tfm; 87 88 ret = crypto_shash_digest(desc, cert->tbs, cert->tbs_size, sig->m); 89 if (ret < 0) 90 goto error_2; 91 92 error_2: 93 kfree(desc); 94 error: 95 crypto_free_shash(tfm); 96 out: 97 pr_devel("<==%s() = %d\n", __func__, ret); 98 return ret; 99 } 100 101 /* 102 * Check for self-signedness in an X.509 cert and if found, check the signature 103 * immediately if we can. 104 */ 105 int x509_check_for_self_signed(struct x509_certificate *cert) 106 { 107 int ret = 0; 108 109 pr_devel("==>%s()\n", __func__); 110 111 if (cert->raw_subject_size != cert->raw_issuer_size || 112 memcmp(cert->raw_subject, cert->raw_issuer, 113 cert->raw_issuer_size) != 0) 114 goto not_self_signed; 115 116 if (cert->sig->auth_ids[0] || cert->sig->auth_ids[1]) { 117 /* If the AKID is present it may have one or two parts. If 118 * both are supplied, both must match. 119 */ 120 bool a = asymmetric_key_id_same(cert->skid, cert->sig->auth_ids[1]); 121 bool b = asymmetric_key_id_same(cert->id, cert->sig->auth_ids[0]); 122 123 if (!a && !b) 124 goto not_self_signed; 125 126 ret = -EKEYREJECTED; 127 if (((a && !b) || (b && !a)) && 128 cert->sig->auth_ids[0] && cert->sig->auth_ids[1]) 129 goto out; 130 } 131 132 if (cert->unsupported_sig) { 133 ret = 0; 134 goto out; 135 } 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 x509_certificate *cert __free(x509_free_certificate) = NULL; 164 struct asymmetric_key_ids *kids __free(kfree) = NULL; 165 char *p, *desc __free(kfree) = NULL; 166 const char *q; 167 size_t srlen, sulen; 168 169 cert = x509_cert_parse(prep->data, prep->datalen); 170 if (IS_ERR(cert)) 171 return PTR_ERR(cert); 172 173 pr_devel("Cert Issuer: %s\n", cert->issuer); 174 pr_devel("Cert Subject: %s\n", cert->subject); 175 pr_devel("Cert Key Algo: %s\n", cert->pub->pkey_algo); 176 pr_devel("Cert Valid period: %lld-%lld\n", cert->valid_from, cert->valid_to); 177 178 cert->pub->id_type = "X509"; 179 180 if (cert->unsupported_sig) { 181 public_key_signature_free(cert->sig); 182 cert->sig = NULL; 183 } else { 184 pr_devel("Cert Signature: %s + %s\n", 185 cert->sig->pkey_algo, cert->sig->hash_algo); 186 } 187 188 /* Don't permit addition of blacklisted keys */ 189 if (cert->blacklisted) 190 return -EKEYREJECTED; 191 192 /* Propose a description */ 193 sulen = strlen(cert->subject); 194 if (cert->raw_skid) { 195 srlen = cert->raw_skid_size; 196 q = cert->raw_skid; 197 } else { 198 srlen = cert->raw_serial_size; 199 q = cert->raw_serial; 200 } 201 202 desc = kmalloc(sulen + 2 + srlen * 2 + 1, GFP_KERNEL); 203 if (!desc) 204 return -ENOMEM; 205 p = memcpy(desc, cert->subject, sulen); 206 p += sulen; 207 *p++ = ':'; 208 *p++ = ' '; 209 p = bin2hex(p, q, srlen); 210 *p = 0; 211 212 kids = kmalloc(sizeof(struct asymmetric_key_ids), GFP_KERNEL); 213 if (!kids) 214 return -ENOMEM; 215 kids->id[0] = cert->id; 216 kids->id[1] = cert->skid; 217 kids->id[2] = asymmetric_key_generate_id(cert->raw_subject, 218 cert->raw_subject_size, 219 "", 0); 220 if (IS_ERR(kids->id[2])) 221 return PTR_ERR(kids->id[2]); 222 223 /* We're pinning the module by being linked against it */ 224 __module_get(public_key_subtype.owner); 225 prep->payload.data[asym_subtype] = &public_key_subtype; 226 prep->payload.data[asym_key_ids] = kids; 227 prep->payload.data[asym_crypto] = cert->pub; 228 prep->payload.data[asym_auth] = cert->sig; 229 prep->description = desc; 230 prep->quotalen = 100; 231 232 /* We've finished with the certificate */ 233 cert->pub = NULL; 234 cert->id = NULL; 235 cert->skid = NULL; 236 cert->sig = NULL; 237 desc = NULL; 238 kids = NULL; 239 return 0; 240 } 241 242 static struct asymmetric_key_parser x509_key_parser = { 243 .owner = THIS_MODULE, 244 .name = "x509", 245 .parse = x509_key_preparse, 246 }; 247 248 /* 249 * Module stuff 250 */ 251 static int __init x509_key_init(void) 252 { 253 return register_asymmetric_key_parser(&x509_key_parser); 254 } 255 256 static void __exit x509_key_exit(void) 257 { 258 unregister_asymmetric_key_parser(&x509_key_parser); 259 } 260 261 module_init(x509_key_init); 262 module_exit(x509_key_exit); 263 264 MODULE_DESCRIPTION("X.509 certificate parser"); 265 MODULE_AUTHOR("Red Hat, Inc."); 266 MODULE_LICENSE("GPL"); 267