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