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KEYS: verify a certificate is signed by a 'trusted' key

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Only public keys, with certificates signed by an existing
'trusted' key on the system trusted keyring, should be added
to a trusted keyring.  This patch adds support for verifying
a certificate's signature.

This is derived from David Howells pkcs7_request_asymmetric_key() patch.

Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Signed-off-by: David Howells <dhowells@redhat.com>
This commit is contained in:
Mimi Zohar 2013-08-20 14:36:27 -04:00 committed by David Howells
parent af34cb0c3d
commit 09fbc47373
1 changed files with 80 additions and 1 deletions
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81
crypto/asymmetric_keys/x509_public_key.c
View file

@ -18,11 +18,59 @@
#include <linux/asn1_decoder.h>
#include <keys/asymmetric-subtype.h>
#include <keys/asymmetric-parser.h>
#include <keys/system_keyring.h>
#include <crypto/hash.h>
#include "asymmetric_keys.h"
#include "public_key.h"
#include "x509_parser.h"
/*
* Find a key in the given keyring by issuer and authority.
*/
static struct key *x509_request_asymmetric_key(
struct key *keyring,
const char *signer, size_t signer_len,
const char *authority, size_t auth_len)
{
key_ref_t key;
char *id;
/* Construct an identifier. */
id = kmalloc(signer_len + 2 + auth_len + 1, GFP_KERNEL);
if (!id)
return ERR_PTR(-ENOMEM);
memcpy(id, signer, signer_len);
id[signer_len + 0] = ':';
id[signer_len + 1] = ' ';
memcpy(id + signer_len + 2, authority, auth_len);
id[signer_len + 2 + auth_len] = 0;
pr_debug("Look up: \"%s\"\n", id);
key = keyring_search(make_key_ref(keyring, 1),
&key_type_asymmetric, id);
if (IS_ERR(key))
pr_debug("Request for module key '%s' err %ld\n",
id, PTR_ERR(key));
kfree(id);
if (IS_ERR(key)) {
switch (PTR_ERR(key)) {
/* Hide some search errors */
case -EACCES:
case -ENOTDIR:
case -EAGAIN:
return ERR_PTR(-ENOKEY);
default:
return ERR_CAST(key);
}
}
pr_devel("<==%s() = 0 [%x]\n", __func__, key_serial(key_ref_to_ptr(key)));
return key_ref_to_ptr(key);
}
/*
* Set up the signature parameters in an X.509 certificate. This involves
* digesting the signed data and extracting the signature.
@ -102,6 +150,33 @@ int x509_check_signature(const struct public_key *pub,
}
EXPORT_SYMBOL_GPL(x509_check_signature);
/*
* Check the new certificate against the ones in the trust keyring. If one of
* those is the signing key and validates the new certificate, then mark the
* new certificate as being trusted.
*
* Return 0 if the new certificate was successfully validated, 1 if we couldn't
* find a matching parent certificate in the trusted list and an error if there
* is a matching certificate but the signature check fails.
*/
static int x509_validate_trust(struct x509_certificate *cert,
struct key *trust_keyring)
{
const struct public_key *pk;
struct key *key;
int ret = 1;
key = x509_request_asymmetric_key(trust_keyring,
cert->issuer, strlen(cert->issuer),
cert->authority,
strlen(cert->authority));
if (!IS_ERR(key)) {
pk = key->payload.data;
ret = x509_check_signature(pk, cert);
}
return ret;
}
/*
* Attempt to parse a data blob for a key as an X509 certificate.
*/
@ -155,9 +230,13 @@ static int x509_key_preparse(struct key_preparsed_payload *prep)
/* Check the signature on the key if it appears to be self-signed */
if (!cert->authority ||
strcmp(cert->fingerprint, cert->authority) == 0) {
ret = x509_check_signature(cert->pub, cert);
ret = x509_check_signature(cert->pub, cert); /* self-signed */
if (ret < 0)
goto error_free_cert;
} else {
ret = x509_validate_trust(cert, system_trusted_keyring);
if (!ret)
prep->trusted = 1;
}
/* Propose a description */