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 <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         if (!cert->pub->pkey_algo)
  34                 cert->unsupported_key = true;
  35
  36         if (!sig->pkey_algo)
  37                 cert->unsupported_sig = true;
  38
  39         /* We check the hash if we can - even if we can't then verify it */
  40         if (!sig->hash_algo) {
  41                 cert->unsupported_sig = true;
  42                 return 0;
  43         }
  44
  45         sig->s = kmemdup(cert->raw_sig, cert->raw_sig_size, GFP_KERNEL);
  46         if (!sig->s)
  47                 return -ENOMEM;
  48
  49         sig->s_size = cert->raw_sig_size;
  50
  51         /* Allocate the hashing algorithm we're going to need and find out how
  52          * big the hash operational data will be.
  53          */
  54         tfm = crypto_alloc_shash(sig->hash_algo, 0, 0);
  55         if (IS_ERR(tfm)) {
  56                 if (PTR_ERR(tfm) == -ENOENT) {
  57                         cert->unsupported_sig = true;
  58                         return 0;
  59                 }
  60                 return PTR_ERR(tfm);
  61         }
  62
  63         desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
  64         sig->digest_size = crypto_shash_digestsize(tfm);
  65
  66         ret = -ENOMEM;
  67         sig->digest = kmalloc(sig->digest_size, GFP_KERNEL);
  68         if (!sig->digest)
  69                 goto error;
  70
  71         desc = kzalloc(desc_size, GFP_KERNEL);
  72         if (!desc)
  73                 goto error;
  74
  75         desc->tfm = tfm;
  76
  77         ret = crypto_shash_digest(desc, cert->tbs, cert->tbs_size, sig->digest);
  78         if (ret < 0)
  79                 goto error_2;
  80
  81         ret = is_hash_blacklisted(sig->digest, sig->digest_size, "tbs");
  82         if (ret == -EKEYREJECTED) {
  83                 pr_err("Cert %*phN is blacklisted\n",
  84                        sig->digest_size, sig->digest);
  85                 cert->blacklisted = true;
  86                 ret = 0;
  87         }
  88
  89 error_2:
  90         kfree(desc);
  91 error:
  92         crypto_free_shash(tfm);
  93         pr_devel("<==%s() = %d\n", __func__, ret);
  94         return ret;
  95 }
  96
  97 /*
  98  * Check for self-signedness in an X.509 cert and if found, check the signature
  99  * immediately if we can.
 100  */
 101 int x509_check_for_self_signed(struct x509_certificate *cert)
 102 {
 103         int ret = 0;
 104
 105         pr_devel("==>%s()\n", __func__);
 106
 107         if (cert->raw_subject_size != cert->raw_issuer_size ||
 108             memcmp(cert->raw_subject, cert->raw_issuer,
 109                    cert->raw_issuer_size) != 0)
 110                 goto not_self_signed;
 111
 112         if (cert->sig->auth_ids[0] || cert->sig->auth_ids[1]) {
 113                 /* If the AKID is present it may have one or two parts.  If
 114                  * both are supplied, both must match.
 115                  */
 116                 bool a = asymmetric_key_id_same(cert->skid, cert->sig->auth_ids[1]);
 117                 bool b = asymmetric_key_id_same(cert->id, cert->sig->auth_ids[0]);
 118
 119                 if (!a && !b)
 120                         goto not_self_signed;
 121
 122                 ret = -EKEYREJECTED;
 123                 if (((a && !b) || (b && !a)) &&
 124                     cert->sig->auth_ids[0] && cert->sig->auth_ids[1])
 125                         goto out;
 126         }
 127
 128         ret = -EKEYREJECTED;
 129         if (strcmp(cert->pub->pkey_algo, cert->sig->pkey_algo) != 0)
 130                 goto out;
 131
 132         ret = public_key_verify_signature(cert->pub, cert->sig);
 133         if (ret < 0) {
 134                 if (ret == -ENOPKG) {
 135                         cert->unsupported_sig = true;
 136                         ret = 0;
 137                 }
 138                 goto out;
 139         }
 140
 141         pr_devel("Cert Self-signature verified");
 142         cert->self_signed = true;
 143
 144 out:
 145         pr_devel("<==%s() = %d\n", __func__, ret);
 146         return ret;
 147
 148 not_self_signed:
 149         pr_devel("<==%s() = 0 [not]\n", __func__);
 150         return 0;
 151 }
 152
 153 /*
 154  * Attempt to parse a data blob for a key as an X509 certificate.
 155  */
 156 static int x509_key_preparse(struct key_preparsed_payload *prep)
 157 {
 158         struct asymmetric_key_ids *kids;
 159         struct x509_certificate *cert;
 160         const char *q;
 161         size_t srlen, sulen;
 162         char *desc = NULL, *p;
 163         int ret;
 164
 165         cert = x509_cert_parse(prep->data, prep->datalen);
 166         if (IS_ERR(cert))
 167                 return PTR_ERR(cert);
 168
 169         pr_devel("Cert Issuer: %s\n", cert->issuer);
 170         pr_devel("Cert Subject: %s\n", cert->subject);
 171
 172         if (cert->unsupported_key) {
 173                 ret = -ENOPKG;
 174                 goto error_free_cert;
 175         }
 176
 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
 222         /* We're pinning the module by being linked against it */
 223         __module_get(public_key_subtype.owner);
 224         prep->payload.data[asym_subtype] = &public_key_subtype;
 225         prep->payload.data[asym_key_ids] = kids;
 226         prep->payload.data[asym_crypto] = cert->pub;
 227         prep->payload.data[asym_auth] = cert->sig;
 228         prep->description = desc;
 229         prep->quotalen = 100;
 230
 231         /* We've finished with the certificate */
 232         cert->pub = NULL;
 233         cert->id = NULL;
 234         cert->skid = NULL;
 235         cert->sig = NULL;
 236         desc = NULL;
 237         ret = 0;
 238
 239 error_free_desc:
 240         kfree(desc);
 241 error_free_cert:
 242         x509_free_certificate(cert);
 243         return ret;
 244 }
 245
 246 static struct asymmetric_key_parser x509_key_parser = {
 247         .owner  = THIS_MODULE,
 248         .name   = "x509",
 249         .parse  = x509_key_preparse,
 250 };
 251
 252 /*
 253  * Module stuff
 254  */
 255 static int __init x509_key_init(void)
 256 {
 257         return register_asymmetric_key_parser(&x509_key_parser);
 258 }
 259
 260 static void __exit x509_key_exit(void)
 261 {
 262         unregister_asymmetric_key_parser(&x509_key_parser);
 263 }
 264
 265 module_init(x509_key_init);
 266 module_exit(x509_key_exit);
 267
 268 MODULE_DESCRIPTION("X.509 certificate parser");
 269 MODULE_AUTHOR("Red Hat, Inc.");
 270 MODULE_LICENSE("GPL");