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/ratelimit.h>
  17 #include <linux/key-type.h>
  18 #include <crypto/public_key.h>
  19 #include <keys/asymmetric-type.h>
  20
  21 #include "integrity.h"
  22
  23 /*
  24  * Request an asymmetric key.
  25  */
  26 static struct key *request_asymmetric_key(struct key *keyring, uint32_t keyid)
  27 {
  28         struct key *key;
  29         char name[12];
  30
  31         sprintf(name, "id:%08x", keyid);
  32
  33         pr_debug("key search: \"%s\"\n", name);
  34
  35         if (keyring) {
  36                 /* search in specific keyring */
  37                 key_ref_t kref;
  38                 kref = keyring_search(make_key_ref(keyring, 1),
  39                                       &key_type_asymmetric, name);
  40                 if (IS_ERR(kref))
  41                         key = ERR_CAST(kref);
  42                 else
  43                         key = key_ref_to_ptr(kref);
  44         } else {
  45                 key = request_key(&key_type_asymmetric, name, NULL);
  46         }
  47
  48         if (IS_ERR(key)) {
  49                 pr_err_ratelimited("Request for unknown key '%s' err %ld\n",
  50                                    name, PTR_ERR(key));
  51                 switch (PTR_ERR(key)) {
  52                         /* Hide some search errors */
  53                 case -EACCES:
  54                 case -ENOTDIR:
  55                 case -EAGAIN:
  56                         return ERR_PTR(-ENOKEY);
  57                 default:
  58                         return key;
  59                 }
  60         }
  61
  62         pr_debug("%s() = 0 [%x]\n", __func__, key_serial(key));
  63
  64         return key;
  65 }
  66
  67 int asymmetric_verify(struct key *keyring, const char *sig,
  68                       int siglen, const char *data, int datalen)
  69 {
  70         struct public_key_signature pks;
  71         struct signature_v2_hdr *hdr = (struct signature_v2_hdr *)sig;
  72         struct key *key;
  73         int ret = -ENOMEM;
  74
  75         if (siglen <= sizeof(*hdr))
  76                 return -EBADMSG;
  77
  78         siglen -= sizeof(*hdr);
  79
  80         if (siglen != __be16_to_cpu(hdr->sig_size))
  81                 return -EBADMSG;
  82
  83         if (hdr->hash_algo >= PKEY_HASH__LAST)
  84                 return -ENOPKG;
  85
  86         key = request_asymmetric_key(keyring, __be32_to_cpu(hdr->keyid));
  87         if (IS_ERR(key))
  88                 return PTR_ERR(key);
  89
  90         memset(&pks, 0, sizeof(pks));
  91
  92         pks.pkey_hash_algo = hdr->hash_algo;
  93         pks.digest = (u8 *)data;
  94         pks.digest_size = datalen;
  95         pks.nr_mpi = 1;
  96         pks.rsa.s = mpi_read_raw_data(hdr->sig, siglen);
  97
  98         if (pks.rsa.s)
  99                 ret = verify_signature(key, &pks);
 100
 101         mpi_free(pks.rsa.s);
 102         key_put(key);
 103         pr_debug("%s() = %d\n", __func__, ret);
 104         return ret;
 105 }