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 <image.h>
  12 #include <dm/devres.h>
  13 #include <linux/compat.h>
  14 #include <linux/err.h>
  15 #include <linux/errno.h>
  16 #else
  17 #include <linux/module.h>
  18 #endif
  19 #include <linux/kernel.h>
  20 #ifdef __UBOOT__
  21 #include <crypto/x509_parser.h>
  22 #include <u-boot/hash-checksum.h>
  23 #else
  24 #include <linux/slab.h>
  25 #include <keys/asymmetric-subtype.h>
  26 #include <keys/asymmetric-parser.h>
  27 #include <keys/system_keyring.h>
  28 #include <crypto/hash.h>
  29 #include "asymmetric_keys.h"
  30 #include "x509_parser.h"
  31 #endif
  32
  33 /*
  34  * Set up the signature parameters in an X.509 certificate.  This involves
  35  * digesting the signed data and extracting the signature.
  36  */
  37 int x509_get_sig_params(struct x509_certificate *cert)
  38 {
  39         struct public_key_signature *sig = cert->sig;
  40 #ifdef __UBOOT__
  41         struct image_region region;
  42 #else
  43         struct crypto_shash *tfm;
  44         struct shash_desc *desc;
  45         size_t desc_size;
  46 #endif
  47         int ret;
  48
  49         pr_devel("==>%s()\n", __func__);
  50
  51         if (!cert->pub->pkey_algo)
  52                 cert->unsupported_key = true;
  53
  54         if (!sig->pkey_algo)
  55                 cert->unsupported_sig = true;
  56
  57         /* We check the hash if we can - even if we can't then verify it */
  58         if (!sig->hash_algo) {
  59                 cert->unsupported_sig = true;
  60                 return 0;
  61         }
  62
  63         sig->s = kmemdup(cert->raw_sig, cert->raw_sig_size, GFP_KERNEL);
  64         if (!sig->s)
  65                 return -ENOMEM;
  66
  67         sig->s_size = cert->raw_sig_size;
  68
  69 #ifdef __UBOOT__
  70         if (!sig->hash_algo)
  71                 return -ENOPKG;
  72         if (!strcmp(sig->hash_algo, "sha256"))
  73                 sig->digest_size = SHA256_SUM_LEN;
  74         else if (!strcmp(sig->hash_algo, "sha384"))
  75                 sig->digest_size = SHA384_SUM_LEN;
  76         else if (!strcmp(sig->hash_algo, "sha512"))
  77                 sig->digest_size = SHA512_SUM_LEN;
  78         else if (!strcmp(sig->hash_algo, "sha1"))
  79                 sig->digest_size = SHA1_SUM_LEN;
  80         else
  81                 return -ENOPKG;
  82
  83         sig->digest = calloc(1, sig->digest_size);
  84         if (!sig->digest)
  85                 return -ENOMEM;
  86
  87         region.data = cert->tbs;
  88         region.size = cert->tbs_size;
  89         hash_calculate(sig->hash_algo, &region, 1, sig->digest);
  90
  91         /* TODO: is_hash_blacklisted()? */
  92
  93         ret = 0;
  94 #else
  95         /* Allocate the hashing algorithm we're going to need and find out how
  96          * big the hash operational data will be.
  97          */
  98         tfm = crypto_alloc_shash(sig->hash_algo, 0, 0);
  99         if (IS_ERR(tfm)) {
 100                 if (PTR_ERR(tfm) == -ENOENT) {
 101                         cert->unsupported_sig = true;
 102                         return 0;
 103                 }
 104                 return PTR_ERR(tfm);
 105         }
 106
 107         desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
 108         sig->digest_size = crypto_shash_digestsize(tfm);
 109
 110         ret = -ENOMEM;
 111         sig->digest = kmalloc(sig->digest_size, GFP_KERNEL);
 112         if (!sig->digest)
 113                 goto error;
 114
 115         desc = kzalloc(desc_size, GFP_KERNEL);
 116         if (!desc)
 117                 goto error;
 118
 119         desc->tfm = tfm;
 120
 121         ret = crypto_shash_digest(desc, cert->tbs, cert->tbs_size, sig->digest);
 122         if (ret < 0)
 123                 goto error_2;
 124
 125         ret = is_hash_blacklisted(sig->digest, sig->digest_size, "tbs");
 126         if (ret == -EKEYREJECTED) {
 127                 pr_err("Cert %*phN is blacklisted\n",
 128                        sig->digest_size, sig->digest);
 129                 cert->blacklisted = true;
 130                 ret = 0;
 131         }
 132
 133 error_2:
 134         kfree(desc);
 135 error:
 136         crypto_free_shash(tfm);
 137 #endif /* __UBOOT__ */
 138         pr_devel("<==%s() = %d\n", __func__, ret);
 139         return ret;
 140 }
 141
 142 /*
 143  * Check for self-signedness in an X.509 cert and if found, check the signature
 144  * immediately if we can.
 145  */
 146 int x509_check_for_self_signed(struct x509_certificate *cert)
 147 {
 148         int ret = 0;
 149
 150         pr_devel("==>%s()\n", __func__);
 151
 152         if (cert->raw_subject_size != cert->raw_issuer_size ||
 153             memcmp(cert->raw_subject, cert->raw_issuer,
 154                    cert->raw_issuer_size) != 0)
 155                 goto not_self_signed;
 156
 157         if (cert->sig->auth_ids[0] || cert->sig->auth_ids[1]) {
 158                 /* If the AKID is present it may have one or two parts.  If
 159                  * both are supplied, both must match.
 160                  */
 161                 bool a = asymmetric_key_id_same(cert->skid, cert->sig->auth_ids[1]);
 162                 bool b = asymmetric_key_id_same(cert->id, cert->sig->auth_ids[0]);
 163
 164                 if (!a && !b)
 165                         goto not_self_signed;
 166
 167                 ret = -EKEYREJECTED;
 168                 if (((a && !b) || (b && !a)) &&
 169                     cert->sig->auth_ids[0] && cert->sig->auth_ids[1])
 170                         goto out;
 171         }
 172
 173         ret = -EKEYREJECTED;
 174         if (strcmp(cert->pub->pkey_algo, cert->sig->pkey_algo) != 0)
 175                 goto out;
 176
 177         ret = public_key_verify_signature(cert->pub, cert->sig);
 178         if (ret < 0) {
 179                 if (ret == -ENOPKG) {
 180                         cert->unsupported_sig = true;
 181                         ret = 0;
 182                 }
 183                 goto out;
 184         }
 185
 186         pr_devel("Cert Self-signature verified");
 187         cert->self_signed = true;
 188
 189 out:
 190         pr_devel("<==%s() = %d\n", __func__, ret);
 191         return ret;
 192
 193 not_self_signed:
 194         pr_devel("<==%s() = 0 [not]\n", __func__);
 195         return 0;
 196 }
 197
 198 #ifndef __UBOOT__
 199 /*
 200  * Attempt to parse a data blob for a key as an X509 certificate.
 201  */
 202 static int x509_key_preparse(struct key_preparsed_payload *prep)
 203 {
 204         struct asymmetric_key_ids *kids;
 205         struct x509_certificate *cert;
 206         const char *q;
 207         size_t srlen, sulen;
 208         char *desc = NULL, *p;
 209         int ret;
 210
 211         cert = x509_cert_parse(prep->data, prep->datalen);
 212         if (IS_ERR(cert))
 213                 return PTR_ERR(cert);
 214
 215         pr_devel("Cert Issuer: %s\n", cert->issuer);
 216         pr_devel("Cert Subject: %s\n", cert->subject);
 217
 218         if (cert->unsupported_key) {
 219                 ret = -ENOPKG;
 220                 goto error_free_cert;
 221         }
 222
 223         pr_devel("Cert Key Algo: %s\n", cert->pub->pkey_algo);
 224         pr_devel("Cert Valid period: %lld-%lld\n", cert->valid_from, cert->valid_to);
 225
 226         cert->pub->id_type = "X509";
 227
 228         if (cert->unsupported_sig) {
 229                 public_key_signature_free(cert->sig);
 230                 cert->sig = NULL;
 231         } else {
 232                 pr_devel("Cert Signature: %s + %s\n",
 233                          cert->sig->pkey_algo, cert->sig->hash_algo);
 234         }
 235
 236         /* Don't permit addition of blacklisted keys */
 237         ret = -EKEYREJECTED;
 238         if (cert->blacklisted)
 239                 goto error_free_cert;
 240
 241         /* Propose a description */
 242         sulen = strlen(cert->subject);
 243         if (cert->raw_skid) {
 244                 srlen = cert->raw_skid_size;
 245                 q = cert->raw_skid;
 246         } else {
 247                 srlen = cert->raw_serial_size;
 248                 q = cert->raw_serial;
 249         }
 250
 251         ret = -ENOMEM;
 252         desc = kmalloc(sulen + 2 + srlen * 2 + 1, GFP_KERNEL);
 253         if (!desc)
 254                 goto error_free_cert;
 255         p = memcpy(desc, cert->subject, sulen);
 256         p += sulen;
 257         *p++ = ':';
 258         *p++ = ' ';
 259         p = bin2hex(p, q, srlen);
 260         *p = 0;
 261
 262         kids = kmalloc(sizeof(struct asymmetric_key_ids), GFP_KERNEL);
 263         if (!kids)
 264                 goto error_free_desc;
 265         kids->id[0] = cert->id;
 266         kids->id[1] = cert->skid;
 267
 268         /* We're pinning the module by being linked against it */
 269         __module_get(public_key_subtype.owner);
 270         prep->payload.data[asym_subtype] = &public_key_subtype;
 271         prep->payload.data[asym_key_ids] = kids;
 272         prep->payload.data[asym_crypto] = cert->pub;
 273         prep->payload.data[asym_auth] = cert->sig;
 274         prep->description = desc;
 275         prep->quotalen = 100;
 276
 277         /* We've finished with the certificate */
 278         cert->pub = NULL;
 279         cert->id = NULL;
 280         cert->skid = NULL;
 281         cert->sig = NULL;
 282         desc = NULL;
 283         ret = 0;
 284
 285 error_free_desc:
 286         kfree(desc);
 287 error_free_cert:
 288         x509_free_certificate(cert);
 289         return ret;
 290 }
 291
 292 static struct asymmetric_key_parser x509_key_parser = {
 293         .owner  = THIS_MODULE,
 294         .name   = "x509",
 295         .parse  = x509_key_preparse,
 296 };
 297
 298 /*
 299  * Module stuff
 300  */
 301 static int __init x509_key_init(void)
 302 {
 303         return register_asymmetric_key_parser(&x509_key_parser);
 304 }
 305
 306 static void __exit x509_key_exit(void)
 307 {
 308         unregister_asymmetric_key_parser(&x509_key_parser);
 309 }
 310
 311 module_init(x509_key_init);
 312 module_exit(x509_key_exit);
 313 #endif /* !__UBOOT__ */
 314
 315 MODULE_DESCRIPTION("X.509 certificate parser");
 316 MODULE_AUTHOR("Red Hat, Inc.");
 317 MODULE_LICENSE("GPL");