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 sig->s = kmemdup(cert->raw_sig, cert->raw_sig_size, GFP_KERNEL); 35 if (!sig->s) 36 return -ENOMEM; 37 38 sig->s_size = cert->raw_sig_size; 39 40 /* Allocate the hashing algorithm we're going to need and find out how 41 * big the hash operational data will be. 42 */ 43 tfm = crypto_alloc_shash(sig->hash_algo, 0, 0); 44 if (IS_ERR(tfm)) { 45 if (PTR_ERR(tfm) == -ENOENT) { 46 cert->unsupported_sig = true; 47 return 0; 48 } 49 return PTR_ERR(tfm); 50 } 51 52 desc_size = crypto_shash_descsize(tfm) + sizeof(*desc); 53 sig->digest_size = crypto_shash_digestsize(tfm); 54 55 ret = -ENOMEM; 56 sig->digest = kmalloc(sig->digest_size, GFP_KERNEL); 57 if (!sig->digest) 58 goto error; 59 60 desc = kzalloc(desc_size, GFP_KERNEL); 61 if (!desc) 62 goto error; 63 64 desc->tfm = tfm; 65 66 ret = crypto_shash_digest(desc, cert->tbs, cert->tbs_size, 67 sig->digest); 68 69 if (ret < 0) 70 goto error_2; 71 72 ret = is_hash_blacklisted(sig->digest, sig->digest_size, 73 BLACKLIST_HASH_X509_TBS); 74 if (ret == -EKEYREJECTED) { 75 pr_err("Cert %*phN is blacklisted\n", 76 sig->digest_size, sig->digest); 77 cert->blacklisted = true; 78 ret = 0; 79 } 80 81 error_2: 82 kfree(desc); 83 error: 84 crypto_free_shash(tfm); 85 pr_devel("<==%s() = %d\n", __func__, ret); 86 return ret; 87 } 88 89 /* 90 * Check for self-signedness in an X.509 cert and if found, check the signature 91 * immediately if we can. 92 */ 93 int x509_check_for_self_signed(struct x509_certificate *cert) 94 { 95 int ret = 0; 96 97 pr_devel("==>%s()\n", __func__); 98 99 if (cert->raw_subject_size != cert->raw_issuer_size || 100 memcmp(cert->raw_subject, cert->raw_issuer, 101 cert->raw_issuer_size) != 0) 102 goto not_self_signed; 103 104 if (cert->sig->auth_ids[0] || cert->sig->auth_ids[1]) { 105 /* If the AKID is present it may have one or two parts. If 106 * both are supplied, both must match. 107 */ 108 bool a = asymmetric_key_id_same(cert->skid, cert->sig->auth_ids[1]); 109 bool b = asymmetric_key_id_same(cert->id, cert->sig->auth_ids[0]); 110 111 if (!a && !b) 112 goto not_self_signed; 113 114 ret = -EKEYREJECTED; 115 if (((a && !b) || (b && !a)) && 116 cert->sig->auth_ids[0] && cert->sig->auth_ids[1]) 117 goto out; 118 } 119 120 if (cert->unsupported_sig) { 121 ret = 0; 122 goto out; 123 } 124 125 ret = public_key_verify_signature(cert->pub, cert->sig); 126 if (ret < 0) { 127 if (ret == -ENOPKG) { 128 cert->unsupported_sig = true; 129 ret = 0; 130 } 131 goto out; 132 } 133 134 pr_devel("Cert Self-signature verified"); 135 cert->self_signed = true; 136 137 out: 138 pr_devel("<==%s() = %d\n", __func__, ret); 139 return ret; 140 141 not_self_signed: 142 pr_devel("<==%s() = 0 [not]\n", __func__); 143 return 0; 144 } 145 146 /* 147 * Attempt to parse a data blob for a key as an X509 certificate. 148 */ 149 static int x509_key_preparse(struct key_preparsed_payload *prep) 150 { 151 struct x509_certificate *cert __free(x509_free_certificate); 152 struct asymmetric_key_ids *kids __free(kfree) = NULL; 153 char *p, *desc __free(kfree) = NULL; 154 const char *q; 155 size_t srlen, sulen; 156 157 cert = x509_cert_parse(prep->data, prep->datalen); 158 if (IS_ERR(cert)) 159 return PTR_ERR(cert); 160 161 pr_devel("Cert Issuer: %s\n", cert->issuer); 162 pr_devel("Cert Subject: %s\n", cert->subject); 163 pr_devel("Cert Key Algo: %s\n", cert->pub->pkey_algo); 164 pr_devel("Cert Valid period: %lld-%lld\n", cert->valid_from, cert->valid_to); 165 166 cert->pub->id_type = "X509"; 167 168 if (cert->unsupported_sig) { 169 public_key_signature_free(cert->sig); 170 cert->sig = NULL; 171 } else { 172 pr_devel("Cert Signature: %s + %s\n", 173 cert->sig->pkey_algo, cert->sig->hash_algo); 174 } 175 176 /* Don't permit addition of blacklisted keys */ 177 if (cert->blacklisted) 178 return -EKEYREJECTED; 179 180 /* Propose a description */ 181 sulen = strlen(cert->subject); 182 if (cert->raw_skid) { 183 srlen = cert->raw_skid_size; 184 q = cert->raw_skid; 185 } else { 186 srlen = cert->raw_serial_size; 187 q = cert->raw_serial; 188 } 189 190 desc = kmalloc(sulen + 2 + srlen * 2 + 1, GFP_KERNEL); 191 if (!desc) 192 return -ENOMEM; 193 p = memcpy(desc, cert->subject, sulen); 194 p += sulen; 195 *p++ = ':'; 196 *p++ = ' '; 197 p = bin2hex(p, q, srlen); 198 *p = 0; 199 200 kids = kmalloc(sizeof(struct asymmetric_key_ids), GFP_KERNEL); 201 if (!kids) 202 return -ENOMEM; 203 kids->id[0] = cert->id; 204 kids->id[1] = cert->skid; 205 kids->id[2] = asymmetric_key_generate_id(cert->raw_subject, 206 cert->raw_subject_size, 207 "", 0); 208 if (IS_ERR(kids->id[2])) 209 return PTR_ERR(kids->id[2]); 210 211 /* We're pinning the module by being linked against it */ 212 __module_get(public_key_subtype.owner); 213 prep->payload.data[asym_subtype] = &public_key_subtype; 214 prep->payload.data[asym_key_ids] = kids; 215 prep->payload.data[asym_crypto] = cert->pub; 216 prep->payload.data[asym_auth] = cert->sig; 217 prep->description = desc; 218 prep->quotalen = 100; 219 220 /* We've finished with the certificate */ 221 cert->pub = NULL; 222 cert->id = NULL; 223 cert->skid = NULL; 224 cert->sig = NULL; 225 desc = NULL; 226 kids = NULL; 227 return 0; 228 } 229 230 static struct asymmetric_key_parser x509_key_parser = { 231 .owner = THIS_MODULE, 232 .name = "x509", 233 .parse = x509_key_preparse, 234 }; 235 236 /* 237 * Module stuff 238 */ 239 static int __init x509_key_init(void) 240 { 241 return register_asymmetric_key_parser(&x509_key_parser); 242 } 243 244 static void __exit x509_key_exit(void) 245 { 246 unregister_asymmetric_key_parser(&x509_key_parser); 247 } 248 249 module_init(x509_key_init); 250 module_exit(x509_key_exit); 251 252 MODULE_DESCRIPTION("X.509 certificate parser"); 253 MODULE_AUTHOR("Red Hat, Inc."); 254 MODULE_LICENSE("GPL"); 255