linux-stable/kernel/module_signing.c

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// SPDX-License-Identifier: GPL-2.0-or-later
/* Module signature checker
*
* Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*/
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/module.h>
#include <linux/module_signature.h>
#include <linux/string.h>
KEYS: Move the point of trust determination to __key_link() Move the point at which a key is determined to be trustworthy to __key_link() so that we use the contents of the keyring being linked in to to determine whether the key being linked in is trusted or not. What is 'trusted' then becomes a matter of what's in the keyring. Currently, the test is done when the key is parsed, but given that at that point we can only sensibly refer to the contents of the system trusted keyring, we can only use that as the basis for working out the trustworthiness of a new key. With this change, a trusted keyring is a set of keys that once the trusted-only flag is set cannot be added to except by verification through one of the contained keys. Further, adding a key into a trusted keyring, whilst it might grant trustworthiness in the context of that keyring, does not automatically grant trustworthiness in the context of a second keyring to which it could be secondarily linked. To accomplish this, the authentication data associated with the key source must now be retained. For an X.509 cert, this means the contents of the AuthorityKeyIdentifier and the signature data. If system keyrings are disabled then restrict_link_by_builtin_trusted() resolves to restrict_link_reject(). The integrity digital signature code still works correctly with this as it was previously using KEY_FLAG_TRUSTED_ONLY, which doesn't permit anything to be added if there is no system keyring against which trust can be determined. Signed-off-by: David Howells <dhowells@redhat.com>
2016-04-06 15:14:26 +00:00
#include <linux/verification.h>
#include <crypto/public_key.h>
#include "module-internal.h"
/*
* Verify the signature on a module.
*/
int mod_verify_sig(const void *mod, struct load_info *info)
{
MODSIGN: Implement module signature checking Check the signature on the module against the keys compiled into the kernel or available in a hardware key store. Currently, only RSA keys are supported - though that's easy enough to change, and the signature is expected to contain raw components (so not a PGP or PKCS#7 formatted blob). The signature blob is expected to consist of the following pieces in order: (1) The binary identifier for the key. This is expected to match the SubjectKeyIdentifier from an X.509 certificate. Only X.509 type identifiers are currently supported. (2) The signature data, consisting of a series of MPIs in which each is in the format of a 2-byte BE word sizes followed by the content data. (3) A 12 byte information block of the form: struct module_signature { enum pkey_algo algo : 8; enum pkey_hash_algo hash : 8; enum pkey_id_type id_type : 8; u8 __pad; __be32 id_length; __be32 sig_length; }; The three enums are defined in crypto/public_key.h. 'algo' contains the public-key algorithm identifier (0->DSA, 1->RSA). 'hash' contains the digest algorithm identifier (0->MD4, 1->MD5, 2->SHA1, etc.). 'id_type' contains the public-key identifier type (0->PGP, 1->X.509). '__pad' should be 0. 'id_length' should contain in the binary identifier length in BE form. 'sig_length' should contain in the signature data length in BE form. The lengths are in BE order rather than CPU order to make dealing with cross-compilation easier. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> (minor Kconfig fix)
2012-09-26 09:11:03 +00:00
struct module_signature ms;
size_t sig_len, modlen = info->len;
int ret;
MODSIGN: Implement module signature checking Check the signature on the module against the keys compiled into the kernel or available in a hardware key store. Currently, only RSA keys are supported - though that's easy enough to change, and the signature is expected to contain raw components (so not a PGP or PKCS#7 formatted blob). The signature blob is expected to consist of the following pieces in order: (1) The binary identifier for the key. This is expected to match the SubjectKeyIdentifier from an X.509 certificate. Only X.509 type identifiers are currently supported. (2) The signature data, consisting of a series of MPIs in which each is in the format of a 2-byte BE word sizes followed by the content data. (3) A 12 byte information block of the form: struct module_signature { enum pkey_algo algo : 8; enum pkey_hash_algo hash : 8; enum pkey_id_type id_type : 8; u8 __pad; __be32 id_length; __be32 sig_length; }; The three enums are defined in crypto/public_key.h. 'algo' contains the public-key algorithm identifier (0->DSA, 1->RSA). 'hash' contains the digest algorithm identifier (0->MD4, 1->MD5, 2->SHA1, etc.). 'id_type' contains the public-key identifier type (0->PGP, 1->X.509). '__pad' should be 0. 'id_length' should contain in the binary identifier length in BE form. 'sig_length' should contain in the signature data length in BE form. The lengths are in BE order rather than CPU order to make dealing with cross-compilation easier. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> (minor Kconfig fix)
2012-09-26 09:11:03 +00:00
pr_devel("==>%s(,%zu)\n", __func__, modlen);
MODSIGN: Implement module signature checking Check the signature on the module against the keys compiled into the kernel or available in a hardware key store. Currently, only RSA keys are supported - though that's easy enough to change, and the signature is expected to contain raw components (so not a PGP or PKCS#7 formatted blob). The signature blob is expected to consist of the following pieces in order: (1) The binary identifier for the key. This is expected to match the SubjectKeyIdentifier from an X.509 certificate. Only X.509 type identifiers are currently supported. (2) The signature data, consisting of a series of MPIs in which each is in the format of a 2-byte BE word sizes followed by the content data. (3) A 12 byte information block of the form: struct module_signature { enum pkey_algo algo : 8; enum pkey_hash_algo hash : 8; enum pkey_id_type id_type : 8; u8 __pad; __be32 id_length; __be32 sig_length; }; The three enums are defined in crypto/public_key.h. 'algo' contains the public-key algorithm identifier (0->DSA, 1->RSA). 'hash' contains the digest algorithm identifier (0->MD4, 1->MD5, 2->SHA1, etc.). 'id_type' contains the public-key identifier type (0->PGP, 1->X.509). '__pad' should be 0. 'id_length' should contain in the binary identifier length in BE form. 'sig_length' should contain in the signature data length in BE form. The lengths are in BE order rather than CPU order to make dealing with cross-compilation easier. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> (minor Kconfig fix)
2012-09-26 09:11:03 +00:00
if (modlen <= sizeof(ms))
MODSIGN: Implement module signature checking Check the signature on the module against the keys compiled into the kernel or available in a hardware key store. Currently, only RSA keys are supported - though that's easy enough to change, and the signature is expected to contain raw components (so not a PGP or PKCS#7 formatted blob). The signature blob is expected to consist of the following pieces in order: (1) The binary identifier for the key. This is expected to match the SubjectKeyIdentifier from an X.509 certificate. Only X.509 type identifiers are currently supported. (2) The signature data, consisting of a series of MPIs in which each is in the format of a 2-byte BE word sizes followed by the content data. (3) A 12 byte information block of the form: struct module_signature { enum pkey_algo algo : 8; enum pkey_hash_algo hash : 8; enum pkey_id_type id_type : 8; u8 __pad; __be32 id_length; __be32 sig_length; }; The three enums are defined in crypto/public_key.h. 'algo' contains the public-key algorithm identifier (0->DSA, 1->RSA). 'hash' contains the digest algorithm identifier (0->MD4, 1->MD5, 2->SHA1, etc.). 'id_type' contains the public-key identifier type (0->PGP, 1->X.509). '__pad' should be 0. 'id_length' should contain in the binary identifier length in BE form. 'sig_length' should contain in the signature data length in BE form. The lengths are in BE order rather than CPU order to make dealing with cross-compilation easier. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> (minor Kconfig fix)
2012-09-26 09:11:03 +00:00
return -EBADMSG;
memcpy(&ms, mod + (modlen - sizeof(ms)), sizeof(ms));
ret = mod_check_sig(&ms, modlen, info->name);
if (ret)
return ret;
MODSIGN: Implement module signature checking Check the signature on the module against the keys compiled into the kernel or available in a hardware key store. Currently, only RSA keys are supported - though that's easy enough to change, and the signature is expected to contain raw components (so not a PGP or PKCS#7 formatted blob). The signature blob is expected to consist of the following pieces in order: (1) The binary identifier for the key. This is expected to match the SubjectKeyIdentifier from an X.509 certificate. Only X.509 type identifiers are currently supported. (2) The signature data, consisting of a series of MPIs in which each is in the format of a 2-byte BE word sizes followed by the content data. (3) A 12 byte information block of the form: struct module_signature { enum pkey_algo algo : 8; enum pkey_hash_algo hash : 8; enum pkey_id_type id_type : 8; u8 __pad; __be32 id_length; __be32 sig_length; }; The three enums are defined in crypto/public_key.h. 'algo' contains the public-key algorithm identifier (0->DSA, 1->RSA). 'hash' contains the digest algorithm identifier (0->MD4, 1->MD5, 2->SHA1, etc.). 'id_type' contains the public-key identifier type (0->PGP, 1->X.509). '__pad' should be 0. 'id_length' should contain in the binary identifier length in BE form. 'sig_length' should contain in the signature data length in BE form. The lengths are in BE order rather than CPU order to make dealing with cross-compilation easier. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> (minor Kconfig fix)
2012-09-26 09:11:03 +00:00
sig_len = be32_to_cpu(ms.sig_len);
modlen -= sig_len + sizeof(ms);
info->len = modlen;
MODSIGN: Implement module signature checking Check the signature on the module against the keys compiled into the kernel or available in a hardware key store. Currently, only RSA keys are supported - though that's easy enough to change, and the signature is expected to contain raw components (so not a PGP or PKCS#7 formatted blob). The signature blob is expected to consist of the following pieces in order: (1) The binary identifier for the key. This is expected to match the SubjectKeyIdentifier from an X.509 certificate. Only X.509 type identifiers are currently supported. (2) The signature data, consisting of a series of MPIs in which each is in the format of a 2-byte BE word sizes followed by the content data. (3) A 12 byte information block of the form: struct module_signature { enum pkey_algo algo : 8; enum pkey_hash_algo hash : 8; enum pkey_id_type id_type : 8; u8 __pad; __be32 id_length; __be32 sig_length; }; The three enums are defined in crypto/public_key.h. 'algo' contains the public-key algorithm identifier (0->DSA, 1->RSA). 'hash' contains the digest algorithm identifier (0->MD4, 1->MD5, 2->SHA1, etc.). 'id_type' contains the public-key identifier type (0->PGP, 1->X.509). '__pad' should be 0. 'id_length' should contain in the binary identifier length in BE form. 'sig_length' should contain in the signature data length in BE form. The lengths are in BE order rather than CPU order to make dealing with cross-compilation easier. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> (minor Kconfig fix)
2012-09-26 09:11:03 +00:00
return verify_pkcs7_signature(mod, modlen, mod + modlen, sig_len,
VERIFY_USE_SECONDARY_KEYRING,
VERIFYING_MODULE_SIGNATURE,
NULL, NULL);
}