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4da8f8c8a1
Add a new configuration DM_VERITY_VERIFY_ROOTHASH_SIG_SECONDARY_KEYRING to enable dm-verity signatures to be verified against the secondary trusted keyring. Instead of relying on the builtin trusted keyring (with hard-coded certificates), the second trusted keyring can include certificate authorities from the builtin trusted keyring and child certificates loaded at run time. Using the secondary trusted keyring enables to use dm-verity disks (e.g. loop devices) signed by keys which did not exist at kernel build time, leveraging the certificate chain of trust model. In practice, this makes it possible to update certificates without kernel update and reboot, aligning with module and kernel (kexec) signature verification which already use the secondary trusted keyring. Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
138 lines
3.1 KiB
C
138 lines
3.1 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (C) 2019 Microsoft Corporation.
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*
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* Author: Jaskaran Singh Khurana <jaskarankhurana@linux.microsoft.com>
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*
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*/
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#include <linux/device-mapper.h>
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#include <linux/verification.h>
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#include <keys/user-type.h>
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#include <linux/module.h>
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#include "dm-verity.h"
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#include "dm-verity-verify-sig.h"
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#define DM_VERITY_VERIFY_ERR(s) DM_VERITY_ROOT_HASH_VERIFICATION " " s
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static bool require_signatures;
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module_param(require_signatures, bool, false);
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MODULE_PARM_DESC(require_signatures,
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"Verify the roothash of dm-verity hash tree");
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#define DM_VERITY_IS_SIG_FORCE_ENABLED() \
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(require_signatures != false)
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bool verity_verify_is_sig_opt_arg(const char *arg_name)
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{
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return (!strcasecmp(arg_name,
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DM_VERITY_ROOT_HASH_VERIFICATION_OPT_SIG_KEY));
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}
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static int verity_verify_get_sig_from_key(const char *key_desc,
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struct dm_verity_sig_opts *sig_opts)
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{
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struct key *key;
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const struct user_key_payload *ukp;
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int ret = 0;
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key = request_key(&key_type_user,
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key_desc, NULL);
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if (IS_ERR(key))
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return PTR_ERR(key);
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down_read(&key->sem);
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ukp = user_key_payload_locked(key);
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if (!ukp) {
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ret = -EKEYREVOKED;
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goto end;
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}
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sig_opts->sig = kmalloc(ukp->datalen, GFP_KERNEL);
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if (!sig_opts->sig) {
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ret = -ENOMEM;
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goto end;
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}
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sig_opts->sig_size = ukp->datalen;
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memcpy(sig_opts->sig, ukp->data, sig_opts->sig_size);
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end:
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up_read(&key->sem);
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key_put(key);
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return ret;
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}
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int verity_verify_sig_parse_opt_args(struct dm_arg_set *as,
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struct dm_verity *v,
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struct dm_verity_sig_opts *sig_opts,
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unsigned int *argc,
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const char *arg_name)
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{
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struct dm_target *ti = v->ti;
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int ret = 0;
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const char *sig_key = NULL;
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if (!*argc) {
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ti->error = DM_VERITY_VERIFY_ERR("Signature key not specified");
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return -EINVAL;
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}
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sig_key = dm_shift_arg(as);
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(*argc)--;
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ret = verity_verify_get_sig_from_key(sig_key, sig_opts);
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if (ret < 0)
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ti->error = DM_VERITY_VERIFY_ERR("Invalid key specified");
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v->signature_key_desc = kstrdup(sig_key, GFP_KERNEL);
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if (!v->signature_key_desc)
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return -ENOMEM;
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return ret;
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}
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/*
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* verify_verify_roothash - Verify the root hash of the verity hash device
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* using builtin trusted keys.
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*
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* @root_hash: For verity, the roothash/data to be verified.
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* @root_hash_len: Size of the roothash/data to be verified.
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* @sig_data: The trusted signature that verifies the roothash/data.
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* @sig_len: Size of the signature.
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*
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*/
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int verity_verify_root_hash(const void *root_hash, size_t root_hash_len,
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const void *sig_data, size_t sig_len)
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{
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int ret;
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if (!root_hash || root_hash_len == 0)
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return -EINVAL;
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if (!sig_data || sig_len == 0) {
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if (DM_VERITY_IS_SIG_FORCE_ENABLED())
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return -ENOKEY;
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else
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return 0;
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}
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ret = verify_pkcs7_signature(root_hash, root_hash_len, sig_data,
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sig_len,
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#ifdef CONFIG_DM_VERITY_VERIFY_ROOTHASH_SIG_SECONDARY_KEYRING
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VERIFY_USE_SECONDARY_KEYRING,
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#else
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NULL,
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#endif
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VERIFYING_UNSPECIFIED_SIGNATURE, NULL, NULL);
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return ret;
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}
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void verity_verify_sig_opts_cleanup(struct dm_verity_sig_opts *sig_opts)
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{
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kfree(sig_opts->sig);
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sig_opts->sig = NULL;
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sig_opts->sig_size = 0;
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}
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