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 = -EKEYREJECTED; 120 if (strcmp(cert->pub->pkey_algo, cert->sig->pkey_algo) != 0 && 121 (strncmp(cert->pub->pkey_algo, "ecdsa-", 6) != 0 || 122 strcmp(cert->sig->pkey_algo, "ecdsa") != 0)) 123 goto out; 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 asymmetric_key_ids *kids; 152 struct x509_certificate *cert; 153 const char *q; 154 size_t srlen, sulen; 155 char *desc = NULL, *p; 156 int ret; 157 158 cert = x509_cert_parse(prep->data, prep->datalen); 159 if (IS_ERR(cert)) 160 return PTR_ERR(cert); 161 162 pr_devel("Cert Issuer: %s\n", cert->issuer); 163 pr_devel("Cert Subject: %s\n", cert->subject); 164 pr_devel("Cert Key Algo: %s\n", cert->pub->pkey_algo); 165 pr_devel("Cert Valid period: %lld-%lld\n", cert->valid_from, cert->valid_to); 166 167 cert->pub->id_type = "X509"; 168 169 if (cert->unsupported_sig) { 170 public_key_signature_free(cert->sig); 171 cert->sig = NULL; 172 } else { 173 pr_devel("Cert Signature: %s + %s\n", 174 cert->sig->pkey_algo, cert->sig->hash_algo); 175 } 176 177 /* Don't permit addition of blacklisted keys */ 178 ret = -EKEYREJECTED; 179 if (cert->blacklisted) 180 goto error_free_cert; 181 182 /* Propose a description */ 183 sulen = strlen(cert->subject); 184 if (cert->raw_skid) { 185 srlen = cert->raw_skid_size; 186 q = cert->raw_skid; 187 } else { 188 srlen = cert->raw_serial_size; 189 q = cert->raw_serial; 190 } 191 192 ret = -ENOMEM; 193 desc = kmalloc(sulen + 2 + srlen * 2 + 1, GFP_KERNEL); 194 if (!desc) 195 goto error_free_cert; 196 p = memcpy(desc, cert->subject, sulen); 197 p += sulen; 198 *p++ = ':'; 199 *p++ = ' '; 200 p = bin2hex(p, q, srlen); 201 *p = 0; 202 203 kids = kmalloc(sizeof(struct asymmetric_key_ids), GFP_KERNEL); 204 if (!kids) 205 goto error_free_desc; 206 kids->id[0] = cert->id; 207 kids->id[1] = cert->skid; 208 kids->id[2] = asymmetric_key_generate_id(cert->raw_subject, 209 cert->raw_subject_size, 210 "", 0); 211 if (IS_ERR(kids->id[2])) { 212 ret = PTR_ERR(kids->id[2]); 213 goto error_free_kids; 214 } 215 216 /* We're pinning the module by being linked against it */ 217 __module_get(public_key_subtype.owner); 218 prep->payload.data[asym_subtype] = &public_key_subtype; 219 prep->payload.data[asym_key_ids] = kids; 220 prep->payload.data[asym_crypto] = cert->pub; 221 prep->payload.data[asym_auth] = cert->sig; 222 prep->description = desc; 223 prep->quotalen = 100; 224 225 /* We've finished with the certificate */ 226 cert->pub = NULL; 227 cert->id = NULL; 228 cert->skid = NULL; 229 cert->sig = NULL; 230 desc = NULL; 231 kids = NULL; 232 ret = 0; 233 234 error_free_kids: 235 kfree(kids); 236 error_free_desc: 237 kfree(desc); 238 error_free_cert: 239 x509_free_certificate(cert); 240 return ret; 241 } 242 243 static struct asymmetric_key_parser x509_key_parser = { 244 .owner = THIS_MODULE, 245 .name = "x509", 246 .parse = x509_key_preparse, 247 }; 248 249 /* 250 * Module stuff 251 */ 252 static int __init x509_key_init(void) 253 { 254 return register_asymmetric_key_parser(&x509_key_parser); 255 } 256 257 static void __exit x509_key_exit(void) 258 { 259 unregister_asymmetric_key_parser(&x509_key_parser); 260 } 261 262 module_init(x509_key_init); 263 module_exit(x509_key_exit); 264 265 MODULE_DESCRIPTION("X.509 certificate parser"); 266 MODULE_AUTHOR("Red Hat, Inc."); 267 MODULE_LICENSE("GPL"); 268