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