crypto/asymmetric_keys/x509_public_key.c

   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 <crypto/sm2.h>
  11 #include <keys/asymmetric-parser.h>
  12 #include <keys/asymmetric-subtype.h>
  13 #include <keys/system_keyring.h>
  14 #include <linux/module.h>
  15 #include <linux/kernel.h>
  16 #include <linux/slab.h>
  17 #include <linux/string.h>
  18 #include "asymmetric_keys.h"
  19 #include "x509_parser.h"
  20
  21 /*
  22  * Set up the signature parameters in an X.509 certificate.  This involves
  23  * digesting the signed data and extracting the signature.
  24  */
  25 int x509_get_sig_params(struct x509_certificate *cert)
  26 {
  27         struct public_key_signature *sig = cert->sig;
  28         struct crypto_shash *tfm;
  29         struct shash_desc *desc;
  30         size_t desc_size;
  31         int ret;
  32
  33         pr_devel("==>%s()\n", __func__);
  34
  35         sig->s = kmemdup(cert->raw_sig, cert->raw_sig_size, GFP_KERNEL);
  36         if (!sig->s)
  37                 return -ENOMEM;
  38
  39         sig->s_size = cert->raw_sig_size;
  40
  41         /* Allocate the hashing algorithm we're going to need and find out how
  42          * big the hash operational data will be.
  43          */
  44         tfm = crypto_alloc_shash(sig->hash_algo, 0, 0);
  45         if (IS_ERR(tfm)) {
  46                 if (PTR_ERR(tfm) == -ENOENT) {
  47                         cert->unsupported_sig = true;
  48                         return 0;
  49                 }
  50                 return PTR_ERR(tfm);
  51         }
  52
  53         desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
  54         sig->digest_size = crypto_shash_digestsize(tfm);
  55
  56         ret = -ENOMEM;
  57         sig->digest = kmalloc(sig->digest_size, GFP_KERNEL);
  58         if (!sig->digest)
  59                 goto error;
  60
  61         desc = kzalloc(desc_size, GFP_KERNEL);
  62         if (!desc)
  63                 goto error;
  64
  65         desc->tfm = tfm;
  66
  67         if (strcmp(cert->pub->pkey_algo, "sm2") == 0) {
  68                 ret = strcmp(sig->hash_algo, "sm3") != 0 ? -EINVAL :
  69                       crypto_shash_init(desc) ?:
  70                       sm2_compute_z_digest(desc, cert->pub->key,
  71                                            cert->pub->keylen, sig->digest) ?:
  72                       crypto_shash_init(desc) ?:
  73                       crypto_shash_update(desc, sig->digest,
  74                                           sig->digest_size) ?:
  75                       crypto_shash_finup(desc, cert->tbs, cert->tbs_size,
  76                                          sig->digest);
  77         } else {
  78                 ret = crypto_shash_digest(desc, cert->tbs, cert->tbs_size,
  79                                           sig->digest);
  80         }
  81
  82         if (ret < 0)
  83                 goto error_2;
  84
  85         ret = is_hash_blacklisted(sig->digest, sig->digest_size,
  86                                   BLACKLIST_HASH_X509_TBS);
  87         if (ret == -EKEYREJECTED) {
  88                 pr_err("Cert %*phN is blacklisted\n",
  89                        sig->digest_size, sig->digest);
  90                 cert->blacklisted = true;
  91                 ret = 0;
  92         }
  93
  94 error_2:
  95         kfree(desc);
  96 error:
  97         crypto_free_shash(tfm);
  98         pr_devel("<==%s() = %d\n", __func__, ret);
  99         return ret;
 100 }
 101
 102 /*
 103  * Check for self-signedness in an X.509 cert and if found, check the signature
 104  * immediately if we can.
 105  */
 106 int x509_check_for_self_signed(struct x509_certificate *cert)
 107 {
 108         int ret = 0;
 109
 110         pr_devel("==>%s()\n", __func__);
 111
 112         if (cert->raw_subject_size != cert->raw_issuer_size ||
 113             memcmp(cert->raw_subject, cert->raw_issuer,
 114                    cert->raw_issuer_size) != 0)
 115                 goto not_self_signed;
 116
 117         if (cert->sig->auth_ids[0] || cert->sig->auth_ids[1]) {
 118                 /* If the AKID is present it may have one or two parts.  If
 119                  * both are supplied, both must match.
 120                  */
 121                 bool a = asymmetric_key_id_same(cert->skid, cert->sig->auth_ids[1]);
 122                 bool b = asymmetric_key_id_same(cert->id, cert->sig->auth_ids[0]);
 123
 124                 if (!a && !b)
 125                         goto not_self_signed;
 126
 127                 ret = -EKEYREJECTED;
 128                 if (((a && !b) || (b && !a)) &&
 129                     cert->sig->auth_ids[0] && cert->sig->auth_ids[1])
 130                         goto out;
 131         }
 132
 133         if (cert->unsupported_sig) {
 134                 ret = 0;
 135                 goto out;
 136         }
 137
 138         ret = public_key_verify_signature(cert->pub, cert->sig);
 139         if (ret < 0) {
 140                 if (ret == -ENOPKG) {
 141                         cert->unsupported_sig = true;
 142                         ret = 0;
 143                 }
 144                 goto out;
 145         }
 146
 147         pr_devel("Cert Self-signature verified");
 148         cert->self_signed = true;
 149
 150 out:
 151         pr_devel("<==%s() = %d\n", __func__, ret);
 152         return ret;
 153
 154 not_self_signed:
 155         pr_devel("<==%s() = 0 [not]\n", __func__);
 156         return 0;
 157 }
 158
 159 /*
 160  * Attempt to parse a data blob for a key as an X509 certificate.
 161  */
 162 static int x509_key_preparse(struct key_preparsed_payload *prep)
 163 {
 164         struct asymmetric_key_ids *kids;
 165         struct x509_certificate *cert;
 166         const char *q;
 167         size_t srlen, sulen;
 168         char *desc = NULL, *p;
 169         int ret;
 170
 171         cert = x509_cert_parse(prep->data, prep->datalen);
 172         if (IS_ERR(cert))
 173                 return PTR_ERR(cert);
 174
 175         pr_devel("Cert Issuer: %s\n", cert->issuer);
 176         pr_devel("Cert Subject: %s\n", cert->subject);
 177         pr_devel("Cert Key Algo: %s\n", cert->pub->pkey_algo);
 178         pr_devel("Cert Valid period: %lld-%lld\n", cert->valid_from, cert->valid_to);
 179
 180         cert->pub->id_type = "X509";
 181
 182         if (cert->unsupported_sig) {
 183                 public_key_signature_free(cert->sig);
 184                 cert->sig = NULL;
 185         } else {
 186                 pr_devel("Cert Signature: %s + %s\n",
 187                          cert->sig->pkey_algo, cert->sig->hash_algo);
 188         }
 189
 190         /* Don't permit addition of blacklisted keys */
 191         ret = -EKEYREJECTED;
 192         if (cert->blacklisted)
 193                 goto error_free_cert;
 194
 195         /* Propose a description */
 196         sulen = strlen(cert->subject);
 197         if (cert->raw_skid) {
 198                 srlen = cert->raw_skid_size;
 199                 q = cert->raw_skid;
 200         } else {
 201                 srlen = cert->raw_serial_size;
 202                 q = cert->raw_serial;
 203         }
 204
 205         ret = -ENOMEM;
 206         desc = kmalloc(sulen + 2 + srlen * 2 + 1, GFP_KERNEL);
 207         if (!desc)
 208                 goto error_free_cert;
 209         p = memcpy(desc, cert->subject, sulen);
 210         p += sulen;
 211         *p++ = ':';
 212         *p++ = ' ';
 213         p = bin2hex(p, q, srlen);
 214         *p = 0;
 215
 216         kids = kmalloc(sizeof(struct asymmetric_key_ids), GFP_KERNEL);
 217         if (!kids)
 218                 goto error_free_desc;
 219         kids->id[0] = cert->id;
 220         kids->id[1] = cert->skid;
 221         kids->id[2] = asymmetric_key_generate_id(cert->raw_subject,
 222                                                  cert->raw_subject_size,
 223                                                  "", 0);
 224         if (IS_ERR(kids->id[2])) {
 225                 ret = PTR_ERR(kids->id[2]);
 226                 goto error_free_kids;
 227         }
 228
 229         /* We're pinning the module by being linked against it */
 230         __module_get(public_key_subtype.owner);
 231         prep->payload.data[asym_subtype] = &public_key_subtype;
 232         prep->payload.data[asym_key_ids] = kids;
 233         prep->payload.data[asym_crypto] = cert->pub;
 234         prep->payload.data[asym_auth] = cert->sig;
 235         prep->description = desc;
 236         prep->quotalen = 100;
 237
 238         /* We've finished with the certificate */
 239         cert->pub = NULL;
 240         cert->id = NULL;
 241         cert->skid = NULL;
 242         cert->sig = NULL;
 243         desc = NULL;
 244         kids = NULL;
 245         ret = 0;
 246
 247 error_free_kids:
 248         kfree(kids);
 249 error_free_desc:
 250         kfree(desc);
 251 error_free_cert:
 252         x509_free_certificate(cert);
 253         return ret;
 254 }
 255
 256 static struct asymmetric_key_parser x509_key_parser = {
 257         .owner  = THIS_MODULE,
 258         .name   = "x509",
 259         .parse  = x509_key_preparse,
 260 };
 261
 262 /*
 263  * Module stuff
 264  */
 265 static int __init x509_key_init(void)
 266 {
 267         return register_asymmetric_key_parser(&x509_key_parser);
 268 }
 269
 270 static void __exit x509_key_exit(void)
 271 {
 272         unregister_asymmetric_key_parser(&x509_key_parser);
 273 }
 274
 275 module_init(x509_key_init);
 276 module_exit(x509_key_exit);
 277
 278 MODULE_DESCRIPTION("X.509 certificate parser");
 279 MODULE_AUTHOR("Red Hat, Inc.");
 280 MODULE_LICENSE("GPL");