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