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 <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");