crypto/asymmetric_keys/x509_public_key.c

   1 /* Instantiate a public key crypto key from an X.509 Certificate
   2  *
   3  * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public Licence
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the Licence, or (at your option) any later version.
  10  */
  11
  12 #define pr_fmt(fmt) "X.509: "fmt
  13 #include <linux/module.h>
  14 #include <linux/kernel.h>
  15 #include <linux/slab.h>
  16 #include <keys/asymmetric-subtype.h>
  17 #include <keys/asymmetric-parser.h>
  18 #include <keys/system_keyring.h>
  19 #include <crypto/hash.h>
  20 #include "asymmetric_keys.h"
  21 #include "x509_parser.h"
  22
  23 /*
  24  * Set up the signature parameters in an X.509 certificate.  This involves
  25  * digesting the signed data and extracting the signature.
  26  */
  27 int x509_get_sig_params(struct x509_certificate *cert)
  28 {
  29         struct public_key_signature *sig = cert->sig;
  30         struct crypto_shash *tfm;
  31         struct shash_desc *desc;
  32         size_t desc_size;
  33         int ret;
  34
  35         pr_devel("==>%s()\n", __func__);
  36
  37         if (!cert->pub->pkey_algo)
  38                 cert->unsupported_key = true;
  39
  40         if (!sig->pkey_algo)
  41                 cert->unsupported_sig = true;
  42
  43         /* We check the hash if we can - even if we can't then verify it */
  44         if (!sig->hash_algo) {
  45                 cert->unsupported_sig = true;
  46                 return 0;
  47         }
  48
  49         sig->s = kmemdup(cert->raw_sig, cert->raw_sig_size, GFP_KERNEL);
  50         if (!sig->s)
  51                 return -ENOMEM;
  52
  53         sig->s_size = cert->raw_sig_size;
  54
  55         /* Allocate the hashing algorithm we're going to need and find out how
  56          * big the hash operational data will be.
  57          */
  58         tfm = crypto_alloc_shash(sig->hash_algo, 0, 0);
  59         if (IS_ERR(tfm)) {
  60                 if (PTR_ERR(tfm) == -ENOENT) {
  61                         cert->unsupported_sig = true;
  62                         return 0;
  63                 }
  64                 return PTR_ERR(tfm);
  65         }
  66
  67         desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
  68         sig->digest_size = crypto_shash_digestsize(tfm);
  69
  70         ret = -ENOMEM;
  71         sig->digest = kmalloc(sig->digest_size, GFP_KERNEL);
  72         if (!sig->digest)
  73                 goto error;
  74
  75         desc = kzalloc(desc_size, GFP_KERNEL);
  76         if (!desc)
  77                 goto error;
  78
  79         desc->tfm = tfm;
  80         desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
  81
  82         ret = crypto_shash_digest(desc, cert->tbs, cert->tbs_size, sig->digest);
  83         if (ret < 0)
  84                 goto error_2;
  85
  86         ret = is_hash_blacklisted(sig->digest, sig->digest_size, "tbs");
  87         if (ret == -EKEYREJECTED) {
  88                 pr_err("Cert %*phN is blacklisted\n",
  89                        sig->digest_size, sig->digest);
  90                 cert->blacklisted = true;
  91                 ret = 0;
  92         }
  93
  94 error_2:
  95         kfree(desc);
  96 error:
  97         crypto_free_shash(tfm);
  98         pr_devel("<==%s() = %d\n", __func__, ret);
  99         return ret;
 100 }
 101
 102 /*
 103  * Check for self-signedness in an X.509 cert and if found, check the signature
 104  * immediately if we can.
 105  */
 106 int x509_check_for_self_signed(struct x509_certificate *cert)
 107 {
 108         int ret = 0;
 109
 110         pr_devel("==>%s()\n", __func__);
 111
 112         if (cert->raw_subject_size != cert->raw_issuer_size ||
 113             memcmp(cert->raw_subject, cert->raw_issuer,
 114                    cert->raw_issuer_size) != 0)
 115                 goto not_self_signed;
 116
 117         if (cert->sig->auth_ids[0] || cert->sig->auth_ids[1]) {
 118                 /* If the AKID is present it may have one or two parts.  If
 119                  * both are supplied, both must match.
 120                  */
 121                 bool a = asymmetric_key_id_same(cert->skid, cert->sig->auth_ids[1]);
 122                 bool b = asymmetric_key_id_same(cert->id, cert->sig->auth_ids[0]);
 123
 124                 if (!a && !b)
 125                         goto not_self_signed;
 126
 127                 ret = -EKEYREJECTED;
 128                 if (((a && !b) || (b && !a)) &&
 129                     cert->sig->auth_ids[0] && cert->sig->auth_ids[1])
 130                         goto out;
 131         }
 132
 133         ret = -EKEYREJECTED;
 134         if (strcmp(cert->pub->pkey_algo, cert->sig->pkey_algo) != 0)
 135                 goto out;
 136
 137         ret = public_key_verify_signature(cert->pub, cert->sig);
 138         if (ret < 0) {
 139                 if (ret == -ENOPKG) {
 140                         cert->unsupported_sig = true;
 141                         ret = 0;
 142                 }
 143                 goto out;
 144         }
 145
 146         pr_devel("Cert Self-signature verified");
 147         cert->self_signed = true;
 148
 149 out:
 150         pr_devel("<==%s() = %d\n", __func__, ret);
 151         return ret;
 152
 153 not_self_signed:
 154         pr_devel("<==%s() = 0 [not]\n", __func__);
 155         return 0;
 156 }
 157
 158 /*
 159  * Attempt to parse a data blob for a key as an X509 certificate.
 160  */
 161 static int x509_key_preparse(struct key_preparsed_payload *prep)
 162 {
 163         struct asymmetric_key_ids *kids;
 164         struct x509_certificate *cert;
 165         const char *q;
 166         size_t srlen, sulen;
 167         char *desc = NULL, *p;
 168         int ret;
 169
 170         cert = x509_cert_parse(prep->data, prep->datalen);
 171         if (IS_ERR(cert))
 172                 return PTR_ERR(cert);
 173
 174         pr_devel("Cert Issuer: %s\n", cert->issuer);
 175         pr_devel("Cert Subject: %s\n", cert->subject);
 176
 177         if (cert->unsupported_key) {
 178                 ret = -ENOPKG;
 179                 goto error_free_cert;
 180         }
 181
 182         pr_devel("Cert Key Algo: %s\n", cert->pub->pkey_algo);
 183         pr_devel("Cert Valid period: %lld-%lld\n", cert->valid_from, cert->valid_to);
 184
 185         cert->pub->id_type = "X509";
 186
 187         if (cert->unsupported_sig) {
 188                 public_key_signature_free(cert->sig);
 189                 cert->sig = NULL;
 190         } else {
 191                 pr_devel("Cert Signature: %s + %s\n",
 192                          cert->sig->pkey_algo, cert->sig->hash_algo);
 193         }
 194
 195         /* Don't permit addition of blacklisted keys */
 196         ret = -EKEYREJECTED;
 197         if (cert->blacklisted)
 198                 goto error_free_cert;
 199
 200         /* Propose a description */
 201         sulen = strlen(cert->subject);
 202         if (cert->raw_skid) {
 203                 srlen = cert->raw_skid_size;
 204                 q = cert->raw_skid;
 205         } else {
 206                 srlen = cert->raw_serial_size;
 207                 q = cert->raw_serial;
 208         }
 209
 210         ret = -ENOMEM;
 211         desc = kmalloc(sulen + 2 + srlen * 2 + 1, GFP_KERNEL);
 212         if (!desc)
 213                 goto error_free_cert;
 214         p = memcpy(desc, cert->subject, sulen);
 215         p += sulen;
 216         *p++ = ':';
 217         *p++ = ' ';
 218         p = bin2hex(p, q, srlen);
 219         *p = 0;
 220
 221         kids = kmalloc(sizeof(struct asymmetric_key_ids), GFP_KERNEL);
 222         if (!kids)
 223                 goto error_free_desc;
 224         kids->id[0] = cert->id;
 225         kids->id[1] = cert->skid;
 226
 227         /* We're pinning the module by being linked against it */
 228         __module_get(public_key_subtype.owner);
 229         prep->payload.data[asym_subtype] = &public_key_subtype;
 230         prep->payload.data[asym_key_ids] = kids;
 231         prep->payload.data[asym_crypto] = cert->pub;
 232         prep->payload.data[asym_auth] = cert->sig;
 233         prep->description = desc;
 234         prep->quotalen = 100;
 235
 236         /* We've finished with the certificate */
 237         cert->pub = NULL;
 238         cert->id = NULL;
 239         cert->skid = NULL;
 240         cert->sig = NULL;
 241         desc = NULL;
 242         ret = 0;
 243
 244 error_free_desc:
 245         kfree(desc);
 246 error_free_cert:
 247         x509_free_certificate(cert);
 248         return ret;
 249 }
 250
 251 static struct asymmetric_key_parser x509_key_parser = {
 252         .owner  = THIS_MODULE,
 253         .name   = "x509",
 254         .parse  = x509_key_preparse,
 255 };
 256
 257 /*
 258  * Module stuff
 259  */
 260 static int __init x509_key_init(void)
 261 {
 262         return register_asymmetric_key_parser(&x509_key_parser);
 263 }
 264
 265 static void __exit x509_key_exit(void)
 266 {
 267         unregister_asymmetric_key_parser(&x509_key_parser);
 268 }
 269
 270 module_init(x509_key_init);
 271 module_exit(x509_key_exit);
 272
 273 MODULE_DESCRIPTION("X.509 certificate parser");
 274 MODULE_AUTHOR("Red Hat, Inc.");
 275 MODULE_LICENSE("GPL");