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  * Set up the signature parameters in an X.509 certificate.  This involves
  28  * digesting the signed data and extracting the signature.
  29  */
  30 int x509_get_sig_params(struct x509_certificate *cert)
  31 {
  32         struct crypto_shash *tfm;
  33         struct shash_desc *desc;
  34         size_t digest_size, desc_size;
  35         void *digest;
  36         int ret;
  37
  38         pr_devel("==>%s()\n", __func__);
  39
  40         if (cert->sig.rsa.s)
  41                 return 0;
  42
  43         cert->sig.rsa.s = mpi_read_raw_data(cert->raw_sig, cert->raw_sig_size);
  44         if (!cert->sig.rsa.s)
  45                 return -ENOMEM;
  46         cert->sig.nr_mpi = 1;
  47
  48         /* Allocate the hashing algorithm we're going to need and find out how
  49          * big the hash operational data will be.
  50          */
  51         tfm = crypto_alloc_shash(hash_algo_name[cert->sig.pkey_hash_algo], 0, 0);
  52         if (IS_ERR(tfm))
  53                 return (PTR_ERR(tfm) == -ENOENT) ? -ENOPKG : PTR_ERR(tfm);
  54
  55         desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
  56         digest_size = crypto_shash_digestsize(tfm);
  57
  58         /* We allocate the hash operational data storage on the end of the
  59          * digest storage space.
  60          */
  61         ret = -ENOMEM;
  62         digest = kzalloc(digest_size + desc_size, GFP_KERNEL);
  63         if (!digest)
  64                 goto error;
  65
  66         cert->sig.digest = digest;
  67         cert->sig.digest_size = digest_size;
  68
  69         desc = digest + digest_size;
  70         desc->tfm = tfm;
  71         desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
  72
  73         ret = crypto_shash_init(desc);
  74         if (ret < 0)
  75                 goto error;
  76         might_sleep();
  77         ret = crypto_shash_finup(desc, cert->tbs, cert->tbs_size, digest);
  78 error:
  79         crypto_free_shash(tfm);
  80         pr_devel("<==%s() = %d\n", __func__, ret);
  81         return ret;
  82 }
  83 EXPORT_SYMBOL_GPL(x509_get_sig_params);
  84
  85 /*
  86  * Check the signature on a certificate using the provided public key
  87  */
  88 int x509_check_signature(const struct public_key *pub,
  89                          struct x509_certificate *cert)
  90 {
  91         int ret;
  92
  93         pr_devel("==>%s()\n", __func__);
  94
  95         ret = x509_get_sig_params(cert);
  96         if (ret < 0)
  97                 return ret;
  98
  99         ret = public_key_verify_signature(pub, &cert->sig);
 100         pr_debug("Cert Verification: %d\n", ret);
 101         return ret;
 102 }
 103 EXPORT_SYMBOL_GPL(x509_check_signature);
 104
 105 /*
 106  * Attempt to parse a data blob for a key as an X509 certificate.
 107  */
 108 static int x509_key_preparse(struct key_preparsed_payload *prep)
 109 {
 110         struct x509_certificate *cert;
 111         size_t srlen, sulen;
 112         char *desc = NULL;
 113         int ret;
 114
 115         cert = x509_cert_parse(prep->data, prep->datalen);
 116         if (IS_ERR(cert))
 117                 return PTR_ERR(cert);
 118
 119         pr_devel("Cert Issuer: %s\n", cert->issuer);
 120         pr_devel("Cert Subject: %s\n", cert->subject);
 121
 122         if (cert->pub->pkey_algo >= PKEY_ALGO__LAST ||
 123             cert->sig.pkey_algo >= PKEY_ALGO__LAST ||
 124             cert->sig.pkey_hash_algo >= PKEY_HASH__LAST ||
 125             !pkey_algo[cert->pub->pkey_algo] ||
 126             !pkey_algo[cert->sig.pkey_algo] ||
 127             !hash_algo_name[cert->sig.pkey_hash_algo]) {
 128                 ret = -ENOPKG;
 129                 goto error_free_cert;
 130         }
 131
 132         pr_devel("Cert Key Algo: %s\n", pkey_algo_name[cert->pub->pkey_algo]);
 133         pr_devel("Cert Valid From: %04ld-%02d-%02d %02d:%02d:%02d\n",
 134                  cert->valid_from.tm_year + 1900, cert->valid_from.tm_mon + 1,
 135                  cert->valid_from.tm_mday, cert->valid_from.tm_hour,
 136                  cert->valid_from.tm_min,  cert->valid_from.tm_sec);
 137         pr_devel("Cert Valid To: %04ld-%02d-%02d %02d:%02d:%02d\n",
 138                  cert->valid_to.tm_year + 1900, cert->valid_to.tm_mon + 1,
 139                  cert->valid_to.tm_mday, cert->valid_to.tm_hour,
 140                  cert->valid_to.tm_min,  cert->valid_to.tm_sec);
 141         pr_devel("Cert Signature: %s + %s\n",
 142                  pkey_algo_name[cert->sig.pkey_algo],
 143                  hash_algo_name[cert->sig.pkey_hash_algo]);
 144
 145         if (!cert->fingerprint) {
 146                 pr_warn("Cert for '%s' must have a SubjKeyId extension\n",
 147                         cert->subject);
 148                 ret = -EKEYREJECTED;
 149                 goto error_free_cert;
 150         }
 151
 152         cert->pub->algo = pkey_algo[cert->pub->pkey_algo];
 153         cert->pub->id_type = PKEY_ID_X509;
 154
 155         /* Check the signature on the key if it appears to be self-signed */
 156         if (!cert->authority ||
 157             strcmp(cert->fingerprint, cert->authority) == 0) {
 158                 ret = x509_check_signature(cert->pub, cert);
 159                 if (ret < 0)
 160                         goto error_free_cert;
 161         }
 162
 163         /* Propose a description */
 164         sulen = strlen(cert->subject);
 165         srlen = strlen(cert->fingerprint);
 166         ret = -ENOMEM;
 167         desc = kmalloc(sulen + 2 + srlen + 1, GFP_KERNEL);
 168         if (!desc)
 169                 goto error_free_cert;
 170         memcpy(desc, cert->subject, sulen);
 171         desc[sulen] = ':';
 172         desc[sulen + 1] = ' ';
 173         memcpy(desc + sulen + 2, cert->fingerprint, srlen);
 174         desc[sulen + 2 + srlen] = 0;
 175
 176         /* We're pinning the module by being linked against it */
 177         __module_get(public_key_subtype.owner);
 178         prep->type_data[0] = &public_key_subtype;
 179         prep->type_data[1] = cert->fingerprint;
 180         prep->payload = cert->pub;
 181         prep->description = desc;
 182         prep->quotalen = 100;
 183
 184         /* We've finished with the certificate */
 185         cert->pub = NULL;
 186         cert->fingerprint = NULL;
 187         desc = NULL;
 188         ret = 0;
 189
 190 error_free_cert:
 191         x509_free_certificate(cert);
 192         return ret;
 193 }
 194
 195 static struct asymmetric_key_parser x509_key_parser = {
 196         .owner  = THIS_MODULE,
 197         .name   = "x509",
 198         .parse  = x509_key_preparse,
 199 };
 200
 201 /*
 202  * Module stuff
 203  */
 204 static int __init x509_key_init(void)
 205 {
 206         return register_asymmetric_key_parser(&x509_key_parser);
 207 }
 208
 209 static void __exit x509_key_exit(void)
 210 {
 211         unregister_asymmetric_key_parser(&x509_key_parser);
 212 }
 213
 214 module_init(x509_key_init);
 215 module_exit(x509_key_exit);
 216
 217 MODULE_DESCRIPTION("X.509 certificate parser");
 218 MODULE_LICENSE("GPL");