kernel/module_signing.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* Module signature checker
   3  *
   4  * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
   5  * Written by David Howells (dhowells@redhat.com)
   6  */
   7
   8 #include <linux/kernel.h>
   9 #include <linux/errno.h>
  10 #include <linux/string.h>
  11 #include <linux/verification.h>
  12 #include <crypto/public_key.h>
  13 #include "module-internal.h"
  14
  15 enum pkey_id_type {
  16         PKEY_ID_PGP,            /* OpenPGP generated key ID */
  17         PKEY_ID_X509,           /* X.509 arbitrary subjectKeyIdentifier */
  18         PKEY_ID_PKCS7,          /* Signature in PKCS#7 message */
  19 };
  20
  21 /*
  22  * Module signature information block.
  23  *
  24  * The constituents of the signature section are, in order:
  25  *
  26  *      - Signer's name
  27  *      - Key identifier
  28  *      - Signature data
  29  *      - Information block
  30  */
  31 struct module_signature {
  32         u8      algo;           /* Public-key crypto algorithm [0] */
  33         u8      hash;           /* Digest algorithm [0] */
  34         u8      id_type;        /* Key identifier type [PKEY_ID_PKCS7] */
  35         u8      signer_len;     /* Length of signer's name [0] */
  36         u8      key_id_len;     /* Length of key identifier [0] */
  37         u8      __pad[3];
  38         __be32  sig_len;        /* Length of signature data */
  39 };
  40
  41 /*
  42  * Verify the signature on a module.
  43  */
  44 int mod_verify_sig(const void *mod, struct load_info *info)
  45 {
  46         struct module_signature ms;
  47         size_t sig_len, modlen = info->len;
  48
  49         pr_devel("==>%s(,%zu)\n", __func__, modlen);
  50
  51         if (modlen <= sizeof(ms))
  52                 return -EBADMSG;
  53
  54         memcpy(&ms, mod + (modlen - sizeof(ms)), sizeof(ms));
  55         modlen -= sizeof(ms);
  56
  57         sig_len = be32_to_cpu(ms.sig_len);
  58         if (sig_len >= modlen)
  59                 return -EBADMSG;
  60         modlen -= sig_len;
  61         info->len = modlen;
  62
  63         if (ms.id_type != PKEY_ID_PKCS7) {
  64                 pr_err("%s: Module is not signed with expected PKCS#7 message\n",
  65                        info->name);
  66                 return -ENOPKG;
  67         }
  68
  69         if (ms.algo != 0 ||
  70             ms.hash != 0 ||
  71             ms.signer_len != 0 ||
  72             ms.key_id_len != 0 ||
  73             ms.__pad[0] != 0 ||
  74             ms.__pad[1] != 0 ||
  75             ms.__pad[2] != 0) {
  76                 pr_err("%s: PKCS#7 signature info has unexpected non-zero params\n",
  77                        info->name);
  78                 return -EBADMSG;
  79         }
  80
  81         return verify_pkcs7_signature(mod, modlen, mod + modlen, sig_len,
  82                                       VERIFY_USE_SECONDARY_KEYRING,
  83                                       VERIFYING_MODULE_SIGNATURE,
  84                                       NULL, NULL);
  85 }