forked from Minki/linux
7d30198ee2
There are non-root X.509 v3 certificates in use out there that contain no Authority Key Identifier extension (RFC5280 section 4.2.1.1). For trust verification purposes the kernel asymmetric key type keeps two struct asymmetric_key_id instances that the key can be looked up by, and another two to look up the key's issuer. The x509 public key type and the PKCS7 type generate them from the SKID and AKID extensions in the certificate. In effect current code has no way to look up the issuer certificate for verification without the AKID. To remedy this, add a third asymmetric_key_id blob to the arrays in both asymmetric_key_id's (for certficate subject) and in the public_keys_signature's auth_ids (for issuer lookup), using just raw subject and issuer DNs from the certificate. Adapt asymmetric_key_ids() and its callers to use the third ID for lookups when none of the other two are available. Attempt to keep the logic intact when they are, to minimise behaviour changes. Adapt the restrict functions' NULL-checks to include that ID too. Do not modify the lookup logic in pkcs7_verify.c, the AKID extensions are still required there. Internally use a new "dn:" prefix to the search specifier string generated for the key lookup in find_asymmetric_key(). This tells asymmetric_key_match_preparse to only match the data against the raw DN in the third ID and shouldn't conflict with search specifiers already in use. In effect implement what (2) in the struct asymmetric_key_id comment (include/keys/asymmetric-type.h) is probably talking about already, so do not modify that comment. It is also how "openssl verify" looks up issuer certificates without the AKID available. Lookups by the raw DN are unambiguous only provided that the CAs respect the condition in RFC5280 4.2.1.1 that the AKID may only be omitted if the CA uses a single signing key. The following is an example of two things that this change enables. A self-signed ceritficate is generated following the example from https://letsencrypt.org/docs/certificates-for-localhost/, and can be looked up by an identifier and verified against itself by linking to a restricted keyring -- both things not possible before due to the missing AKID extension: $ openssl req -x509 -out localhost.crt -outform DER -keyout localhost.key \ -newkey rsa:2048 -nodes -sha256 \ -subj '/CN=localhost' -extensions EXT -config <( \ echo -e "[dn]\nCN=localhost\n[req]\ndistinguished_name = dn\n[EXT]\n" \ "subjectAltName=DNS:localhost\nkeyUsage=digitalSignature\n" \ "extendedKeyUsage=serverAuth") $ keyring=`keyctl newring test @u` $ trusted=`keyctl padd asymmetric trusted $keyring < localhost.crt`; \ echo $trusted 39726322 $ keyctl search $keyring asymmetric dn:3112301006035504030c096c6f63616c686f7374 39726322 $ keyctl restrict_keyring $keyring asymmetric key_or_keyring:$trusted $ keyctl padd asymmetric verified $keyring < localhost.crt Signed-off-by: Andrew Zaborowski <andrew.zaborowski@intel.com> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> Acked-by: Jarkko Sakkinen <jarkko@kernel.org> Acked-by: David Howells <dhowells@redhat.com> Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
87 lines
2.4 KiB
C
87 lines
2.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0-or-later */
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/* Asymmetric public-key algorithm definitions
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*
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* See Documentation/crypto/asymmetric-keys.rst
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*
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* Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*/
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#ifndef _LINUX_PUBLIC_KEY_H
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#define _LINUX_PUBLIC_KEY_H
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#include <linux/keyctl.h>
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#include <linux/oid_registry.h>
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/*
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* Cryptographic data for the public-key subtype of the asymmetric key type.
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*
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* Note that this may include private part of the key as well as the public
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* part.
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*/
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struct public_key {
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void *key;
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u32 keylen;
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enum OID algo;
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void *params;
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u32 paramlen;
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bool key_is_private;
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const char *id_type;
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const char *pkey_algo;
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};
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extern void public_key_free(struct public_key *key);
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/*
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* Public key cryptography signature data
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*/
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struct public_key_signature {
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struct asymmetric_key_id *auth_ids[3];
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u8 *s; /* Signature */
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u8 *digest;
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u32 s_size; /* Number of bytes in signature */
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u32 digest_size; /* Number of bytes in digest */
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const char *pkey_algo;
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const char *hash_algo;
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const char *encoding;
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const void *data;
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unsigned int data_size;
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};
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extern void public_key_signature_free(struct public_key_signature *sig);
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extern struct asymmetric_key_subtype public_key_subtype;
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struct key;
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struct key_type;
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union key_payload;
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extern int restrict_link_by_signature(struct key *dest_keyring,
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const struct key_type *type,
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const union key_payload *payload,
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struct key *trust_keyring);
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extern int restrict_link_by_key_or_keyring(struct key *dest_keyring,
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const struct key_type *type,
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const union key_payload *payload,
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struct key *trusted);
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extern int restrict_link_by_key_or_keyring_chain(struct key *trust_keyring,
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const struct key_type *type,
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const union key_payload *payload,
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struct key *trusted);
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extern int query_asymmetric_key(const struct kernel_pkey_params *,
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struct kernel_pkey_query *);
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extern int encrypt_blob(struct kernel_pkey_params *, const void *, void *);
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extern int decrypt_blob(struct kernel_pkey_params *, const void *, void *);
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extern int create_signature(struct kernel_pkey_params *, const void *, void *);
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extern int verify_signature(const struct key *,
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const struct public_key_signature *);
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int public_key_verify_signature(const struct public_key *pkey,
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const struct public_key_signature *sig);
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#endif /* _LINUX_PUBLIC_KEY_H */
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