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 <linux/err.h>
  17 #include <linux/mpi.h>
  18 #include <linux/asn1_decoder.h>
  19 #include <keys/asymmetric-subtype.h>
  20 #include <keys/asymmetric-parser.h>
  21 #include <crypto/hash.h>
  22 #include "asymmetric_keys.h"
  23 #include "public_key.h"
  24 #include "x509_parser.h"
  25
  26 /*
  27  * Check the signature on a certificate using the provided public key
  28  */
  29 static int x509_check_signature(const struct public_key *pub,
  30                                 const struct x509_certificate *cert)
  31 {
  32         struct public_key_signature *sig;
  33         struct crypto_shash *tfm;
  34         struct shash_desc *desc;
  35         size_t digest_size, desc_size;
  36         int ret;
  37
  38         pr_devel("==>%s()\n", __func__);
  39
  40         /* Allocate the hashing algorithm we're going to need and find out how
  41          * big the hash operational data will be.
  42          */
  43         tfm = crypto_alloc_shash(pkey_hash_algo_name[cert->sig_hash_algo], 0, 0);
  44         if (IS_ERR(tfm))
  45                 return (PTR_ERR(tfm) == -ENOENT) ? -ENOPKG : PTR_ERR(tfm);
  46
  47         desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
  48         digest_size = crypto_shash_digestsize(tfm);
  49
  50         /* We allocate the hash operational data storage on the end of our
  51          * context data.
  52          */
  53         ret = -ENOMEM;
  54         sig = kzalloc(sizeof(*sig) + desc_size + digest_size, GFP_KERNEL);
  55         if (!sig)
  56                 goto error_no_sig;
  57
  58         sig->pkey_hash_algo     = cert->sig_hash_algo;
  59         sig->digest             = (u8 *)sig + sizeof(*sig) + desc_size;
  60         sig->digest_size        = digest_size;
  61
  62         desc = (void *)sig + sizeof(*sig);
  63         desc->tfm       = tfm;
  64         desc->flags     = CRYPTO_TFM_REQ_MAY_SLEEP;
  65
  66         ret = crypto_shash_init(desc);
  67         if (ret < 0)
  68                 goto error;
  69
  70         ret = -ENOMEM;
  71         sig->rsa.s = mpi_read_raw_data(cert->sig, cert->sig_size);
  72         if (!sig->rsa.s)
  73                 goto error;
  74
  75         ret = crypto_shash_finup(desc, cert->tbs, cert->tbs_size, sig->digest);
  76         if (ret < 0)
  77                 goto error_mpi;
  78
  79         ret = pub->algo->verify_signature(pub, sig);
  80
  81         pr_debug("Cert Verification: %d\n", ret);
  82
  83 error_mpi:
  84         mpi_free(sig->rsa.s);
  85 error:
  86         kfree(sig);
  87 error_no_sig:
  88         crypto_free_shash(tfm);
  89
  90         pr_devel("<==%s() = %d\n", __func__, ret);
  91         return ret;
  92 }
  93
  94 /*
  95  * Attempt to parse a data blob for a key as an X509 certificate.
  96  */
  97 static int x509_key_preparse(struct key_preparsed_payload *prep)
  98 {
  99         struct x509_certificate *cert;
 100         struct tm now;
 101         size_t srlen, sulen;
 102         char *desc = NULL;
 103         int ret;
 104
 105         cert = x509_cert_parse(prep->data, prep->datalen);
 106         if (IS_ERR(cert))
 107                 return PTR_ERR(cert);
 108
 109         pr_devel("Cert Issuer: %s\n", cert->issuer);
 110         pr_devel("Cert Subject: %s\n", cert->subject);
 111         pr_devel("Cert Key Algo: %s\n", pkey_algo_name[cert->pkey_algo]);
 112         pr_devel("Cert Valid From: %04ld-%02d-%02d %02d:%02d:%02d\n",
 113                  cert->valid_from.tm_year + 1900, cert->valid_from.tm_mon + 1,
 114                  cert->valid_from.tm_mday, cert->valid_from.tm_hour,
 115                  cert->valid_from.tm_min,  cert->valid_from.tm_sec);
 116         pr_devel("Cert Valid To: %04ld-%02d-%02d %02d:%02d:%02d\n",
 117                  cert->valid_to.tm_year + 1900, cert->valid_to.tm_mon + 1,
 118                  cert->valid_to.tm_mday, cert->valid_to.tm_hour,
 119                  cert->valid_to.tm_min,  cert->valid_to.tm_sec);
 120         pr_devel("Cert Signature: %s + %s\n",
 121                  pkey_algo_name[cert->sig_pkey_algo],
 122                  pkey_hash_algo_name[cert->sig_hash_algo]);
 123
 124         if (!cert->fingerprint || !cert->authority) {
 125                 pr_warn("Cert for '%s' must have SubjKeyId and AuthKeyId extensions\n",
 126                         cert->subject);
 127                 ret = -EKEYREJECTED;
 128                 goto error_free_cert;
 129         }
 130
 131         time_to_tm(CURRENT_TIME.tv_sec, 0, &now);
 132         pr_devel("Now: %04ld-%02d-%02d %02d:%02d:%02d\n",
 133                  now.tm_year + 1900, now.tm_mon + 1, now.tm_mday,
 134                  now.tm_hour, now.tm_min,  now.tm_sec);
 135         if (now.tm_year < cert->valid_from.tm_year ||
 136             (now.tm_year == cert->valid_from.tm_year &&
 137              (now.tm_mon < cert->valid_from.tm_mon ||
 138               (now.tm_mon == cert->valid_from.tm_mon &&
 139                (now.tm_mday < cert->valid_from.tm_mday ||
 140                 (now.tm_mday == cert->valid_from.tm_mday &&
 141                  (now.tm_hour < cert->valid_from.tm_hour ||
 142                   (now.tm_hour == cert->valid_from.tm_hour &&
 143                    (now.tm_min < cert->valid_from.tm_min ||
 144                     (now.tm_min == cert->valid_from.tm_min &&
 145                      (now.tm_sec < cert->valid_from.tm_sec
 146                       ))))))))))) {
 147                 pr_warn("Cert %s is not yet valid\n", cert->fingerprint);
 148                 ret = -EKEYREJECTED;
 149                 goto error_free_cert;
 150         }
 151         if (now.tm_year > cert->valid_to.tm_year ||
 152             (now.tm_year == cert->valid_to.tm_year &&
 153              (now.tm_mon > cert->valid_to.tm_mon ||
 154               (now.tm_mon == cert->valid_to.tm_mon &&
 155                (now.tm_mday > cert->valid_to.tm_mday ||
 156                 (now.tm_mday == cert->valid_to.tm_mday &&
 157                  (now.tm_hour > cert->valid_to.tm_hour ||
 158                   (now.tm_hour == cert->valid_to.tm_hour &&
 159                    (now.tm_min > cert->valid_to.tm_min ||
 160                     (now.tm_min == cert->valid_to.tm_min &&
 161                      (now.tm_sec > cert->valid_to.tm_sec
 162                       ))))))))))) {
 163                 pr_warn("Cert %s has expired\n", cert->fingerprint);
 164                 ret = -EKEYEXPIRED;
 165                 goto error_free_cert;
 166         }
 167
 168         cert->pub->algo = pkey_algo[cert->pkey_algo];
 169         cert->pub->id_type = PKEY_ID_X509;
 170
 171         /* Check the signature on the key */
 172         if (strcmp(cert->fingerprint, cert->authority) == 0) {
 173                 ret = x509_check_signature(cert->pub, cert);
 174                 if (ret < 0)
 175                         goto error_free_cert;
 176         }
 177
 178         /* Propose a description */
 179         sulen = strlen(cert->subject);
 180         srlen = strlen(cert->fingerprint);
 181         ret = -ENOMEM;
 182         desc = kmalloc(sulen + 2 + srlen + 1, GFP_KERNEL);
 183         if (!desc)
 184                 goto error_free_cert;
 185         memcpy(desc, cert->subject, sulen);
 186         desc[sulen] = ':';
 187         desc[sulen + 1] = ' ';
 188         memcpy(desc + sulen + 2, cert->fingerprint, srlen);
 189         desc[sulen + 2 + srlen] = 0;
 190
 191         /* We're pinning the module by being linked against it */
 192         __module_get(public_key_subtype.owner);
 193         prep->type_data[0] = &public_key_subtype;
 194         prep->type_data[1] = cert->fingerprint;
 195         prep->payload = cert->pub;
 196         prep->description = desc;
 197         prep->quotalen = 100;
 198
 199         /* We've finished with the certificate */
 200         cert->pub = NULL;
 201         cert->fingerprint = NULL;
 202         desc = NULL;
 203         ret = 0;
 204
 205 error_free_cert:
 206         x509_free_certificate(cert);
 207         return ret;
 208 }
 209
 210 static struct asymmetric_key_parser x509_key_parser = {
 211         .owner  = THIS_MODULE,
 212         .name   = "x509",
 213         .parse  = x509_key_preparse,
 214 };
 215
 216 /*
 217  * Module stuff
 218  */
 219 static int __init x509_key_init(void)
 220 {
 221         return register_asymmetric_key_parser(&x509_key_parser);
 222 }
 223
 224 static void __exit x509_key_exit(void)
 225 {
 226         unregister_asymmetric_key_parser(&x509_key_parser);
 227 }
 228
 229 module_init(x509_key_init);
 230 module_exit(x509_key_exit);