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KEYS: Keyring asymmetric key restrict method with chaining 

Add a restrict_link_by_key_or_keyring_chain link restriction that
searches for signing keys in the destination keyring in addition to the
signing key or keyring designated when the destination keyring was
created. Userspace enables this behavior by including the "chain" option
in the keyring restriction:

  keyctl(KEYCTL_RESTRICT_KEYRING, keyring, "asymmetric",
         "key_or_keyring:<signing key>:chain");

Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
hifive-unleashed-5.1
Mat Martineau 2016-10-04 16:42:45 -07:00
parent 7e3c4d2208
commit 8e323a02e8
4 changed files with 164 additions and 55 deletions
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7
Documentation/crypto/asymmetric-keys.txt
View File

@ -343,7 +343,7 @@ Several restriction methods are available:
(3) Restrict using a separate key or keyring
- Option string used with KEYCTL_RESTRICT_KEYRING:
- "key_or_keyring:<key or keyring serial number>"
- "key_or_keyring:<key or keyring serial number>[:chain]"
Whenever a key link is requested, the link will only succeed if the key
being linked is signed by one of the designated keys. This key may be
@ -351,6 +351,11 @@ Several restriction methods are available:
a group of keys may be searched for the signing key by providing the
serial number for a keyring.
When the "chain" option is provided at the end of the string, the keys
within the destination keyring will also be searched for signing keys.
This allows for verification of certificate chains by adding each
cert in order (starting closest to the root) to one keyring.
In all of these cases, if the signing key is found the signature of the key to
be linked will be verified using the signing key. The requested key is added
to the keyring only if the signature is successfully verified. -ENOKEY is

33
crypto/asymmetric_keys/asymmetric_type.c
View File

@ -496,20 +496,37 @@ static struct key_restriction *asymmetric_lookup_restriction(
restrict_method = strsep(&next, ":");
if ((strcmp(restrict_method, "key_or_keyring") == 0) && next) {
char *key_text;
key_serial_t serial;
struct key *key;
key_restrict_link_func_t link_fn =
restrict_link_by_key_or_keyring;
bool allow_null_key = false;
if (kstrtos32(next, 0, &serial) < 0)
goto out;
key_text = strsep(&next, ":");
key = key_lookup(serial);
if (IS_ERR(key)) {
ret = ERR_CAST(key);
goto out;
if (next) {
if (strcmp(next, "chain") != 0)
goto out;
link_fn = restrict_link_by_key_or_keyring_chain;
allow_null_key = true;
}
ret = asymmetric_restriction_alloc(
restrict_link_by_key_or_keyring, key);
if (kstrtos32(key_text, 0, &serial) < 0)
goto out;
if ((serial == 0) && allow_null_key) {
key = NULL;
} else {
key = key_lookup(serial);
if (IS_ERR(key)) {
ret = ERR_CAST(key);
goto out;
}
}
ret = asymmetric_restriction_alloc(link_fn, key);
if (IS_ERR(ret))
key_put(key);
}

174
crypto/asymmetric_keys/restrict.c
View File

@ -109,6 +109,105 @@ int restrict_link_by_signature(struct key *dest_keyring,
return ret;
}
static bool match_either_id(const struct asymmetric_key_ids *pair,
const struct asymmetric_key_id *single)
{
return (asymmetric_key_id_same(pair->id[0], single) ||
asymmetric_key_id_same(pair->id[1], single));
}
static int key_or_keyring_common(struct key *dest_keyring,
const struct key_type *type,
const union key_payload *payload,
struct key *trusted, bool check_dest)
{
const struct public_key_signature *sig;
struct key *key = NULL;
int ret;
pr_devel("==>%s()\n", __func__);
if (!dest_keyring)
return -ENOKEY;
else if (dest_keyring->type != &key_type_keyring)
return -EOPNOTSUPP;
if (!trusted && !check_dest)
return -ENOKEY;
if (type != &key_type_asymmetric)
return -EOPNOTSUPP;
sig = payload->data[asym_auth];
if (!sig->auth_ids[0] && !sig->auth_ids[1])
return -ENOKEY;
if (trusted) {
if (trusted->type == &key_type_keyring) {
/* See if we have a key that signed this one. */
key = find_asymmetric_key(trusted, sig->auth_ids[0],
sig->auth_ids[1], false);
if (IS_ERR(key))
key = NULL;
} else if (trusted->type == &key_type_asymmetric) {
const struct asymmetric_key_ids *signer_ids;
signer_ids = asymmetric_key_ids(trusted);
/*
* The auth_ids come from the candidate key (the
* one that is being considered for addition to
* dest_keyring) and identify the key that was
* used to sign.
*
* The signer_ids are identifiers for the
* signing key specified for dest_keyring.
*
* The first auth_id is the preferred id, and
* the second is the fallback. If only one
* auth_id is present, it may match against
* either signer_id. If two auth_ids are
* present, the first auth_id must match one
* signer_id and the second auth_id must match
* the second signer_id.
*/
if (!sig->auth_ids[0] || !sig->auth_ids[1]) {
const struct asymmetric_key_id *auth_id;
auth_id = sig->auth_ids[0] ?: sig->auth_ids[1];
if (match_either_id(signer_ids, auth_id))
key = __key_get(trusted);
} else if (asymmetric_key_id_same(signer_ids->id[1],
sig->auth_ids[1]) &&
match_either_id(signer_ids,
sig->auth_ids[0])) {
key = __key_get(trusted);
}
} else {
return -EOPNOTSUPP;
}
}
if (check_dest && !key) {
/* See if the destination has a key that signed this one. */
key = find_asymmetric_key(dest_keyring, sig->auth_ids[0],
sig->auth_ids[1], false);
if (IS_ERR(key))
key = NULL;
}
if (!key)
return -ENOKEY;
ret = key_validate(key);
if (ret == 0)
ret = verify_signature(key, sig);
key_put(key);
return ret;
}
/**
* restrict_link_by_key_or_keyring - Restrict additions to a ring of public
* keys using the restrict_key information stored in the ring.
@ -132,50 +231,33 @@ int restrict_link_by_key_or_keyring(struct key *dest_keyring,
const union key_payload *payload,
struct key *trusted)
{
const struct public_key_signature *sig;
struct key *key;
int ret;
pr_devel("==>%s()\n", __func__);
if (!dest_keyring)
return -ENOKEY;
else if (dest_keyring->type != &key_type_keyring)
return -EOPNOTSUPP;
if (!trusted)
return -ENOKEY;
if (type != &key_type_asymmetric)
return -EOPNOTSUPP;
sig = payload->data[asym_auth];
if (!sig->auth_ids[0] && !sig->auth_ids[1])
return -ENOKEY;
if (trusted->type == &key_type_keyring) {
/* See if we have a key that signed this one. */
key = find_asymmetric_key(trusted, sig->auth_ids[0],
sig->auth_ids[1], false);
if (IS_ERR(key))
return -ENOKEY;
} else if (trusted->type == &key_type_asymmetric) {
const struct asymmetric_key_ids *kids;
kids = asymmetric_key_ids(trusted);
if (!asymmetric_key_id_same(kids->id[1], sig->auth_ids[0]))
return -ENOKEY;
key = __key_get(trusted);
} else {
return -EOPNOTSUPP;
}
ret = key_validate(key);
if (ret == 0)
ret = verify_signature(key, sig);
key_put(key);
return ret;
return key_or_keyring_common(dest_keyring, type, payload, trusted,
false);
}
/**
* restrict_link_by_key_or_keyring_chain - Restrict additions to a ring of
* public keys using the restrict_key information stored in the ring.
* @dest_keyring: Keyring being linked to.
* @type: The type of key being added.
* @payload: The payload of the new key.
* @trusted: A key or ring of keys that can be used to vouch for the new cert.
*
* Check the new certificate only against the key or keys passed in the data
* parameter. If one of those is the signing key and validates the new
* certificate, then mark the new certificate as being ok to link.
*
* Returns 0 if the new certificate was accepted, -ENOKEY if we
* couldn't find a matching parent certificate in the trusted list,
* -EKEYREJECTED if the signature check fails, and some other error if
* there is a matching certificate but the signature check cannot be
* performed.
*/
int restrict_link_by_key_or_keyring_chain(struct key *dest_keyring,
const struct key_type *type,
const union key_payload *payload,
struct key *trusted)
{
return key_or_keyring_common(dest_keyring, type, payload, trusted,
true);
}

5
include/crypto/public_key.h
View File

@ -60,6 +60,11 @@ extern int restrict_link_by_key_or_keyring(struct key *dest_keyring,
const union key_payload *payload,
struct key *trusted);
extern int restrict_link_by_key_or_keyring_chain(struct key *trust_keyring,
const struct key_type *type,
const union key_payload *payload,
struct key *trusted);
extern int verify_signature(const struct key *key,
const struct public_key_signature *sig);