security/integrity/digsig_asymmetric.c

   1 /*
   2  * Copyright (C) 2013 Intel Corporation
   3  *
   4  * Author:
   5  * Dmitry Kasatkin <dmitry.kasatkin@intel.com>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation, version 2 of the License.
  10  *
  11  */
  12
  13 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  14
  15 #include <linux/err.h>
  16 #include <linux/key-type.h>
  17 #include <crypto/public_key.h>
  18 #include <keys/asymmetric-type.h>
  19
  20 #include "integrity.h"
  21
  22 /*
  23  * Request an asymmetric key.
  24  */
  25 static struct key *request_asymmetric_key(struct key *keyring, uint32_t keyid)
  26 {
  27         struct key *key;
  28         char name[12];
  29
  30         sprintf(name, "id:%x", keyid);
  31
  32         pr_debug("key search: \"%s\"\n", name);
  33
  34         if (keyring) {
  35                 /* search in specific keyring */
  36                 key_ref_t kref;
  37                 kref = keyring_search(make_key_ref(keyring, 1),
  38                                       &key_type_asymmetric, name);
  39                 if (IS_ERR(kref))
  40                         key = ERR_CAST(kref);
  41                 else
  42                         key = key_ref_to_ptr(kref);
  43         } else {
  44                 key = request_key(&key_type_asymmetric, name, NULL);
  45         }
  46
  47         if (IS_ERR(key)) {
  48                 pr_warn("Request for unknown key '%s' err %ld\n",
  49                         name, PTR_ERR(key));
  50                 switch (PTR_ERR(key)) {
  51                         /* Hide some search errors */
  52                 case -EACCES:
  53                 case -ENOTDIR:
  54                 case -EAGAIN:
  55                         return ERR_PTR(-ENOKEY);
  56                 default:
  57                         return key;
  58                 }
  59         }
  60
  61         pr_debug("%s() = 0 [%x]\n", __func__, key_serial(key));
  62
  63         return key;
  64 }
  65
  66 int asymmetric_verify(struct key *keyring, const char *sig,
  67                       int siglen, const char *data, int datalen)
  68 {
  69         struct public_key_signature pks;
  70         struct signature_v2_hdr *hdr = (struct signature_v2_hdr *)sig;
  71         struct key *key;
  72         int ret = -ENOMEM;
  73
  74         if (siglen <= sizeof(*hdr))
  75                 return -EBADMSG;
  76
  77         siglen -= sizeof(*hdr);
  78
  79         if (siglen != __be16_to_cpu(hdr->sig_size))
  80                 return -EBADMSG;
  81
  82         if (hdr->hash_algo >= PKEY_HASH__LAST)
  83                 return -ENOPKG;
  84
  85         key = request_asymmetric_key(keyring, __be32_to_cpu(hdr->keyid));
  86         if (IS_ERR(key))
  87                 return PTR_ERR(key);
  88
  89         memset(&pks, 0, sizeof(pks));
  90
  91         pks.pkey_hash_algo = hdr->hash_algo;
  92         pks.digest = (u8 *)data;
  93         pks.digest_size = datalen;
  94         pks.nr_mpi = 1;
  95         pks.rsa.s = mpi_read_raw_data(hdr->sig, siglen);
  96
  97         if (pks.rsa.s)
  98                 ret = verify_signature(key, &pks);
  99
 100         mpi_free(pks.rsa.s);
 101         key_put(key);
 102         pr_debug("%s() = %d\n", __func__, ret);
 103         return ret;
 104 }