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 static const
  27 struct public_key_algorithm *x509_public_key_algorithms[PKEY_ALGO__LAST] = {
  28         [PKEY_ALGO_DSA]         = NULL,
  29 #if defined(CONFIG_PUBLIC_KEY_ALGO_RSA) || \
  30         defined(CONFIG_PUBLIC_KEY_ALGO_RSA_MODULE)
  31         [PKEY_ALGO_RSA]         = &RSA_public_key_algorithm,
  32 #endif
  33 };
  34
  35 /*
  36  * Check the signature on a certificate using the provided public key
  37  */
  38 static int x509_check_signature(const struct public_key *pub,
  39                                 const struct x509_certificate *cert)
  40 {
  41         struct public_key_signature *sig;
  42         struct crypto_shash *tfm;
  43         struct shash_desc *desc;
  44         size_t digest_size, desc_size;
  45         int ret;
  46
  47         pr_devel("==>%s()\n", __func__);
  48
  49         /* Allocate the hashing algorithm we're going to need and find out how
  50          * big the hash operational data will be.
  51          */
  52         tfm = crypto_alloc_shash(pkey_hash_algo[cert->sig_hash_algo], 0, 0);
  53         if (IS_ERR(tfm))
  54                 return (PTR_ERR(tfm) == -ENOENT) ? -ENOPKG : PTR_ERR(tfm);
  55
  56         desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
  57         digest_size = crypto_shash_digestsize(tfm);
  58
  59         /* We allocate the hash operational data storage on the end of our
  60          * context data.
  61          */
  62         ret = -ENOMEM;
  63         sig = kzalloc(sizeof(*sig) + desc_size + digest_size, GFP_KERNEL);
  64         if (!sig)
  65                 goto error_no_sig;
  66
  67         sig->pkey_hash_algo     = cert->sig_hash_algo;
  68         sig->digest             = (u8 *)sig + sizeof(*sig) + desc_size;
  69         sig->digest_size        = digest_size;
  70
  71         desc = (void *)sig + sizeof(*sig);
  72         desc->tfm       = tfm;
  73         desc->flags     = CRYPTO_TFM_REQ_MAY_SLEEP;
  74
  75         ret = crypto_shash_init(desc);
  76         if (ret < 0)
  77                 goto error;
  78
  79         ret = -ENOMEM;
  80         sig->rsa.s = mpi_read_raw_data(cert->sig, cert->sig_size);
  81         if (!sig->rsa.s)
  82                 goto error;
  83
  84         ret = crypto_shash_finup(desc, cert->tbs, cert->tbs_size, sig->digest);
  85         if (ret < 0)
  86                 goto error_mpi;
  87
  88         ret = pub->algo->verify_signature(pub, sig);
  89
  90         pr_debug("Cert Verification: %d\n", ret);
  91
  92 error_mpi:
  93         mpi_free(sig->rsa.s);
  94 error:
  95         kfree(sig);
  96 error_no_sig:
  97         crypto_free_shash(tfm);
  98
  99         pr_devel("<==%s() = %d\n", __func__, ret);
 100         return ret;
 101 }
 102
 103 /*
 104  * Attempt to parse a data blob for a key as an X509 certificate.
 105  */
 106 static int x509_key_preparse(struct key_preparsed_payload *prep)
 107 {
 108         struct x509_certificate *cert;
 109         size_t srlen, sulen;
 110         char *desc = NULL;
 111         int ret;
 112
 113         cert = x509_cert_parse(prep->data, prep->datalen);
 114         if (IS_ERR(cert))
 115                 return PTR_ERR(cert);
 116
 117         pr_devel("Cert Issuer: %s\n", cert->issuer);
 118         pr_devel("Cert Subject: %s\n", cert->subject);
 119         pr_devel("Cert Key Algo: %s\n", pkey_algo[cert->pkey_algo]);
 120         pr_devel("Cert Valid From: %04ld-%02d-%02d %02d:%02d:%02d\n",
 121                  cert->valid_from.tm_year + 1900, cert->valid_from.tm_mon + 1,
 122                  cert->valid_from.tm_mday, cert->valid_from.tm_hour,
 123                  cert->valid_from.tm_min,  cert->valid_from.tm_sec);
 124         pr_devel("Cert Valid To: %04ld-%02d-%02d %02d:%02d:%02d\n",
 125                  cert->valid_to.tm_year + 1900, cert->valid_to.tm_mon + 1,
 126                  cert->valid_to.tm_mday, cert->valid_to.tm_hour,
 127                  cert->valid_to.tm_min,  cert->valid_to.tm_sec);
 128         pr_devel("Cert Signature: %s + %s\n",
 129                  pkey_algo[cert->sig_pkey_algo],
 130                  pkey_hash_algo[cert->sig_hash_algo]);
 131
 132         if (!cert->fingerprint || !cert->authority) {
 133                 pr_warn("Cert for '%s' must have SubjKeyId and AuthKeyId extensions\n",
 134                         cert->subject);
 135                 ret = -EKEYREJECTED;
 136                 goto error_free_cert;
 137         }
 138
 139         cert->pub->algo = x509_public_key_algorithms[cert->pkey_algo];
 140         cert->pub->id_type = PKEY_ID_X509;
 141
 142         /* Check the signature on the key */
 143         if (strcmp(cert->fingerprint, cert->authority) == 0) {
 144                 ret = x509_check_signature(cert->pub, cert);
 145                 if (ret < 0)
 146                         goto error_free_cert;
 147         }
 148
 149         /* Propose a description */
 150         sulen = strlen(cert->subject);
 151         srlen = strlen(cert->fingerprint);
 152         ret = -ENOMEM;
 153         desc = kmalloc(sulen + 2 + srlen + 1, GFP_KERNEL);
 154         if (!desc)
 155                 goto error_free_cert;
 156         memcpy(desc, cert->subject, sulen);
 157         desc[sulen] = ':';
 158         desc[sulen + 1] = ' ';
 159         memcpy(desc + sulen + 2, cert->fingerprint, srlen);
 160         desc[sulen + 2 + srlen] = 0;
 161
 162         /* We're pinning the module by being linked against it */
 163         __module_get(public_key_subtype.owner);
 164         prep->type_data[0] = &public_key_subtype;
 165         prep->type_data[1] = cert->fingerprint;
 166         prep->payload = cert->pub;
 167         prep->description = desc;
 168         prep->quotalen = 100;
 169
 170         /* We've finished with the certificate */
 171         cert->pub = NULL;
 172         cert->fingerprint = NULL;
 173         desc = NULL;
 174         ret = 0;
 175
 176 error_free_cert:
 177         x509_free_certificate(cert);
 178         return ret;
 179 }
 180
 181 static struct asymmetric_key_parser x509_key_parser = {
 182         .owner  = THIS_MODULE,
 183         .name   = "x509",
 184         .parse  = x509_key_preparse,
 185 };
 186
 187 /*
 188  * Module stuff
 189  */
 190 static int __init x509_key_init(void)
 191 {
 192         return register_asymmetric_key_parser(&x509_key_parser);
 193 }
 194
 195 static void __exit x509_key_exit(void)
 196 {
 197         unregister_asymmetric_key_parser(&x509_key_parser);
 198 }
 199
 200 module_init(x509_key_init);
 201 module_exit(x509_key_exit);