lib/crypto/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 #ifdef __UBOOT__
  10 #include <common.h>
  11 #include <linux/compat.h>
  12 #include <linux/errno.h>
  13 #else
  14 #include <linux/module.h>
  15 #endif
  16 #include <linux/kernel.h>
  17 #ifndef __UBOOT__
  18 #include <linux/slab.h>
  19 #include <keys/asymmetric-subtype.h>
  20 #include <keys/asymmetric-parser.h>
  21 #include <keys/system_keyring.h>
  22 #include <crypto/hash.h>
  23 #include "asymmetric_keys.h"
  24 #endif
  25 #include "x509_parser.h"
  26
  27 /*
  28  * Set up the signature parameters in an X.509 certificate.  This involves
  29  * digesting the signed data and extracting the signature.
  30  */
  31 int x509_get_sig_params(struct x509_certificate *cert)
  32 {
  33         struct public_key_signature *sig = cert->sig;
  34 #ifndef __UBOOT__
  35         struct crypto_shash *tfm;
  36         struct shash_desc *desc;
  37         size_t desc_size;
  38 #endif
  39         int ret;
  40
  41         pr_devel("==>%s()\n", __func__);
  42
  43         if (!cert->pub->pkey_algo)
  44                 cert->unsupported_key = true;
  45
  46         if (!sig->pkey_algo)
  47                 cert->unsupported_sig = true;
  48
  49         /* We check the hash if we can - even if we can't then verify it */
  50         if (!sig->hash_algo) {
  51                 cert->unsupported_sig = true;
  52                 return 0;
  53         }
  54
  55         sig->s = kmemdup(cert->raw_sig, cert->raw_sig_size, GFP_KERNEL);
  56         if (!sig->s)
  57                 return -ENOMEM;
  58
  59         sig->s_size = cert->raw_sig_size;
  60
  61 #ifdef __UBOOT__
  62         /*
  63          * Note:
  64          * This part (filling sig->digest) should be implemented if
  65          * x509_check_for_self_signed() is enabled x509_cert_parse().
  66          * Currently, this check won't affect UEFI secure boot.
  67          */
  68         ret = 0;
  69 #else
  70         /* Allocate the hashing algorithm we're going to need and find out how
  71          * big the hash operational data will be.
  72          */
  73         tfm = crypto_alloc_shash(sig->hash_algo, 0, 0);
  74         if (IS_ERR(tfm)) {
  75                 if (PTR_ERR(tfm) == -ENOENT) {
  76                         cert->unsupported_sig = true;
  77                         return 0;
  78                 }
  79                 return PTR_ERR(tfm);
  80         }
  81
  82         desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
  83         sig->digest_size = crypto_shash_digestsize(tfm);
  84
  85         ret = -ENOMEM;
  86         sig->digest = kmalloc(sig->digest_size, GFP_KERNEL);
  87         if (!sig->digest)
  88                 goto error;
  89
  90         desc = kzalloc(desc_size, GFP_KERNEL);
  91         if (!desc)
  92                 goto error;
  93
  94         desc->tfm = tfm;
  95
  96         ret = crypto_shash_digest(desc, cert->tbs, cert->tbs_size, sig->digest);
  97         if (ret < 0)
  98                 goto error_2;
  99
 100         ret = is_hash_blacklisted(sig->digest, sig->digest_size, "tbs");
 101         if (ret == -EKEYREJECTED) {
 102                 pr_err("Cert %*phN is blacklisted\n",
 103                        sig->digest_size, sig->digest);
 104                 cert->blacklisted = true;
 105                 ret = 0;
 106         }
 107
 108 error_2:
 109         kfree(desc);
 110 error:
 111         crypto_free_shash(tfm);
 112 #endif /* __UBOOT__ */
 113         pr_devel("<==%s() = %d\n", __func__, ret);
 114         return ret;
 115 }
 116
 117 #ifndef __UBOOT__
 118 /*
 119  * Check for self-signedness in an X.509 cert and if found, check the signature
 120  * immediately if we can.
 121  */
 122 int x509_check_for_self_signed(struct x509_certificate *cert)
 123 {
 124         int ret = 0;
 125
 126         pr_devel("==>%s()\n", __func__);
 127
 128         if (cert->raw_subject_size != cert->raw_issuer_size ||
 129             memcmp(cert->raw_subject, cert->raw_issuer,
 130                    cert->raw_issuer_size) != 0)
 131                 goto not_self_signed;
 132
 133         if (cert->sig->auth_ids[0] || cert->sig->auth_ids[1]) {
 134                 /* If the AKID is present it may have one or two parts.  If
 135                  * both are supplied, both must match.
 136                  */
 137                 bool a = asymmetric_key_id_same(cert->skid, cert->sig->auth_ids[1]);
 138                 bool b = asymmetric_key_id_same(cert->id, cert->sig->auth_ids[0]);
 139
 140                 if (!a && !b)
 141                         goto not_self_signed;
 142
 143                 ret = -EKEYREJECTED;
 144                 if (((a && !b) || (b && !a)) &&
 145                     cert->sig->auth_ids[0] && cert->sig->auth_ids[1])
 146                         goto out;
 147         }
 148
 149         ret = -EKEYREJECTED;
 150         if (strcmp(cert->pub->pkey_algo, cert->sig->pkey_algo) != 0)
 151                 goto out;
 152
 153         ret = public_key_verify_signature(cert->pub, cert->sig);
 154         if (ret < 0) {
 155                 if (ret == -ENOPKG) {
 156                         cert->unsupported_sig = true;
 157                         ret = 0;
 158                 }
 159                 goto out;
 160         }
 161
 162         pr_devel("Cert Self-signature verified");
 163         cert->self_signed = true;
 164
 165 out:
 166         pr_devel("<==%s() = %d\n", __func__, ret);
 167         return ret;
 168
 169 not_self_signed:
 170         pr_devel("<==%s() = 0 [not]\n", __func__);
 171         return 0;
 172 }
 173
 174 /*
 175  * Attempt to parse a data blob for a key as an X509 certificate.
 176  */
 177 static int x509_key_preparse(struct key_preparsed_payload *prep)
 178 {
 179         struct asymmetric_key_ids *kids;
 180         struct x509_certificate *cert;
 181         const char *q;
 182         size_t srlen, sulen;
 183         char *desc = NULL, *p;
 184         int ret;
 185
 186         cert = x509_cert_parse(prep->data, prep->datalen);
 187         if (IS_ERR(cert))
 188                 return PTR_ERR(cert);
 189
 190         pr_devel("Cert Issuer: %s\n", cert->issuer);
 191         pr_devel("Cert Subject: %s\n", cert->subject);
 192
 193         if (cert->unsupported_key) {
 194                 ret = -ENOPKG;
 195                 goto error_free_cert;
 196         }
 197
 198         pr_devel("Cert Key Algo: %s\n", cert->pub->pkey_algo);
 199         pr_devel("Cert Valid period: %lld-%lld\n", cert->valid_from, cert->valid_to);
 200
 201         cert->pub->id_type = "X509";
 202
 203         if (cert->unsupported_sig) {
 204                 public_key_signature_free(cert->sig);
 205                 cert->sig = NULL;
 206         } else {
 207                 pr_devel("Cert Signature: %s + %s\n",
 208                          cert->sig->pkey_algo, cert->sig->hash_algo);
 209         }
 210
 211         /* Don't permit addition of blacklisted keys */
 212         ret = -EKEYREJECTED;
 213         if (cert->blacklisted)
 214                 goto error_free_cert;
 215
 216         /* Propose a description */
 217         sulen = strlen(cert->subject);
 218         if (cert->raw_skid) {
 219                 srlen = cert->raw_skid_size;
 220                 q = cert->raw_skid;
 221         } else {
 222                 srlen = cert->raw_serial_size;
 223                 q = cert->raw_serial;
 224         }
 225
 226         ret = -ENOMEM;
 227         desc = kmalloc(sulen + 2 + srlen * 2 + 1, GFP_KERNEL);
 228         if (!desc)
 229                 goto error_free_cert;
 230         p = memcpy(desc, cert->subject, sulen);
 231         p += sulen;
 232         *p++ = ':';
 233         *p++ = ' ';
 234         p = bin2hex(p, q, srlen);
 235         *p = 0;
 236
 237         kids = kmalloc(sizeof(struct asymmetric_key_ids), GFP_KERNEL);
 238         if (!kids)
 239                 goto error_free_desc;
 240         kids->id[0] = cert->id;
 241         kids->id[1] = cert->skid;
 242
 243         /* We're pinning the module by being linked against it */
 244         __module_get(public_key_subtype.owner);
 245         prep->payload.data[asym_subtype] = &public_key_subtype;
 246         prep->payload.data[asym_key_ids] = kids;
 247         prep->payload.data[asym_crypto] = cert->pub;
 248         prep->payload.data[asym_auth] = cert->sig;
 249         prep->description = desc;
 250         prep->quotalen = 100;
 251
 252         /* We've finished with the certificate */
 253         cert->pub = NULL;
 254         cert->id = NULL;
 255         cert->skid = NULL;
 256         cert->sig = NULL;
 257         desc = NULL;
 258         ret = 0;
 259
 260 error_free_desc:
 261         kfree(desc);
 262 error_free_cert:
 263         x509_free_certificate(cert);
 264         return ret;
 265 }
 266
 267 static struct asymmetric_key_parser x509_key_parser = {
 268         .owner  = THIS_MODULE,
 269         .name   = "x509",
 270         .parse  = x509_key_preparse,
 271 };
 272
 273 /*
 274  * Module stuff
 275  */
 276 static int __init x509_key_init(void)
 277 {
 278         return register_asymmetric_key_parser(&x509_key_parser);
 279 }
 280
 281 static void __exit x509_key_exit(void)
 282 {
 283         unregister_asymmetric_key_parser(&x509_key_parser);
 284 }
 285
 286 module_init(x509_key_init);
 287 module_exit(x509_key_exit);
 288 #endif /* !__UBOOT__ */
 289
 290 MODULE_DESCRIPTION("X.509 certificate parser");
 291 MODULE_AUTHOR("Red Hat, Inc.");
 292 MODULE_LICENSE("GPL");