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         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 = public_key_verify_signature(cert->pub, cert->sig);
 120         if (ret < 0) {
 121                 if (ret == -ENOPKG) {
 122                         cert->unsupported_sig = true;
 123                         ret = 0;
 124                 }
 125                 goto out;
 126         }
 127
 128         pr_devel("Cert Self-signature verified");
 129         cert->self_signed = true;
 130
 131 out:
 132         pr_devel("<==%s() = %d\n", __func__, ret);
 133         return ret;
 134
 135 not_self_signed:
 136         pr_devel("<==%s() = 0 [not]\n", __func__);
 137         return 0;
 138 }
 139
 140 /*
 141  * Attempt to parse a data blob for a key as an X509 certificate.
 142  */
 143 static int x509_key_preparse(struct key_preparsed_payload *prep)
 144 {
 145         struct asymmetric_key_ids *kids;
 146         struct x509_certificate *cert;
 147         const char *q;
 148         size_t srlen, sulen;
 149         char *desc = NULL, *p;
 150         int ret;
 151
 152         cert = x509_cert_parse(prep->data, prep->datalen);
 153         if (IS_ERR(cert))
 154                 return PTR_ERR(cert);
 155
 156         pr_devel("Cert Issuer: %s\n", cert->issuer);
 157         pr_devel("Cert Subject: %s\n", cert->subject);
 158         pr_devel("Cert Key Algo: %s\n", cert->pub->pkey_algo);
 159         pr_devel("Cert Valid period: %lld-%lld\n", cert->valid_from, cert->valid_to);
 160
 161         cert->pub->id_type = "X509";
 162
 163         if (cert->unsupported_sig) {
 164                 public_key_signature_free(cert->sig);
 165                 cert->sig = NULL;
 166         } else {
 167                 pr_devel("Cert Signature: %s + %s\n",
 168                          cert->sig->pkey_algo, cert->sig->hash_algo);
 169         }
 170
 171         /* Don't permit addition of blacklisted keys */
 172         ret = -EKEYREJECTED;
 173         if (cert->blacklisted)
 174                 goto error_free_cert;
 175
 176         /* Propose a description */
 177         sulen = strlen(cert->subject);
 178         if (cert->raw_skid) {
 179                 srlen = cert->raw_skid_size;
 180                 q = cert->raw_skid;
 181         } else {
 182                 srlen = cert->raw_serial_size;
 183                 q = cert->raw_serial;
 184         }
 185
 186         ret = -ENOMEM;
 187         desc = kmalloc(sulen + 2 + srlen * 2 + 1, GFP_KERNEL);
 188         if (!desc)
 189                 goto error_free_cert;
 190         p = memcpy(desc, cert->subject, sulen);
 191         p += sulen;
 192         *p++ = ':';
 193         *p++ = ' ';
 194         p = bin2hex(p, q, srlen);
 195         *p = 0;
 196
 197         kids = kmalloc(sizeof(struct asymmetric_key_ids), GFP_KERNEL);
 198         if (!kids)
 199                 goto error_free_desc;
 200         kids->id[0] = cert->id;
 201         kids->id[1] = cert->skid;
 202         kids->id[2] = asymmetric_key_generate_id(cert->raw_subject,
 203                                                  cert->raw_subject_size,
 204                                                  "", 0);
 205         if (IS_ERR(kids->id[2])) {
 206                 ret = PTR_ERR(kids->id[2]);
 207                 goto error_free_kids;
 208         }
 209
 210         /* We're pinning the module by being linked against it */
 211         __module_get(public_key_subtype.owner);
 212         prep->payload.data[asym_subtype] = &public_key_subtype;
 213         prep->payload.data[asym_key_ids] = kids;
 214         prep->payload.data[asym_crypto] = cert->pub;
 215         prep->payload.data[asym_auth] = cert->sig;
 216         prep->description = desc;
 217         prep->quotalen = 100;
 218
 219         /* We've finished with the certificate */
 220         cert->pub = NULL;
 221         cert->id = NULL;
 222         cert->skid = NULL;
 223         cert->sig = NULL;
 224         desc = NULL;
 225         kids = NULL;
 226         ret = 0;
 227
 228 error_free_kids:
 229         kfree(kids);
 230 error_free_desc:
 231         kfree(desc);
 232 error_free_cert:
 233         x509_free_certificate(cert);
 234         return ret;
 235 }
 236
 237 static struct asymmetric_key_parser x509_key_parser = {
 238         .owner  = THIS_MODULE,
 239         .name   = "x509",
 240         .parse  = x509_key_preparse,
 241 };
 242
 243 /*
 244  * Module stuff
 245  */
 246 static int __init x509_key_init(void)
 247 {
 248         return register_asymmetric_key_parser(&x509_key_parser);
 249 }
 250
 251 static void __exit x509_key_exit(void)
 252 {
 253         unregister_asymmetric_key_parser(&x509_key_parser);
 254 }
 255
 256 module_init(x509_key_init);
 257 module_exit(x509_key_exit);
 258
 259 MODULE_DESCRIPTION("X.509 certificate parser");
 260 MODULE_AUTHOR("Red Hat, Inc.");
 261 MODULE_LICENSE("GPL");