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lsm: infrastructure management of the key security blob

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Move management of the key->security blob out of the individual security
modules and into the security infrastructure. Instead of allocating the
blobs from within the modules the modules tell the infrastructure how
much space is required, and the space is allocated there.  There are
no existing modules that require a key_free hook, so the call to it and
the definition for it have been removed.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: John Johansen <john.johansen@canonical.com>
[PM: subject tweak]
Signed-off-by: Paul Moore <paul@paul-moore.com>
This commit is contained in:
Casey Schaufler 2024-07-10 14:32:26 -07:00 committed by Paul Moore
parent 2aff9d20d5
commit 5f8d28f6d7
7 changed files with 69 additions and 38 deletions
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1
include/linux/lsm_hook_defs.h
View File

@ -403,7 +403,6 @@ LSM_HOOK(int, 0, xfrm_decode_session, struct sk_buff *skb, u32 *secid,
#ifdef CONFIG_KEYS
LSM_HOOK(int, 0, key_alloc, struct key *key, const struct cred *cred,
unsigned long flags)
LSM_HOOK(void, LSM_RET_VOID, key_free, struct key *key)
LSM_HOOK(int, 0, key_permission, key_ref_t key_ref, const struct cred *cred,
enum key_need_perm need_perm)
LSM_HOOK(int, 0, key_getsecurity, struct key *key, char **buffer)

1
include/linux/lsm_hooks.h
View File

@ -76,6 +76,7 @@ struct lsm_blob_sizes {
int lbs_sock;
int lbs_superblock;
int lbs_ipc;
int lbs_key;
int lbs_msg_msg;
int lbs_task;
int lbs_xattr_count; /* number of xattr slots in new_xattrs array */

39
security/security.c
View File

@ -227,6 +227,7 @@ static void __init lsm_set_blob_sizes(struct lsm_blob_sizes *needed)
blob_sizes.lbs_inode = sizeof(struct rcu_head);
lsm_set_blob_size(&needed->lbs_inode, &blob_sizes.lbs_inode);
lsm_set_blob_size(&needed->lbs_ipc, &blob_sizes.lbs_ipc);
lsm_set_blob_size(&needed->lbs_key, &blob_sizes.lbs_key);
lsm_set_blob_size(&needed->lbs_msg_msg, &blob_sizes.lbs_msg_msg);
lsm_set_blob_size(&needed->lbs_sock, &blob_sizes.lbs_sock);
lsm_set_blob_size(&needed->lbs_superblock, &blob_sizes.lbs_superblock);
@ -402,6 +403,9 @@ static void __init ordered_lsm_init(void)
init_debug("file blob size = %d\n", blob_sizes.lbs_file);
init_debug("inode blob size = %d\n", blob_sizes.lbs_inode);
init_debug("ipc blob size = %d\n", blob_sizes.lbs_ipc);
#ifdef CONFIG_KEYS
init_debug("key blob size = %d\n", blob_sizes.lbs_key);
#endif /* CONFIG_KEYS */
init_debug("msg_msg blob size = %d\n", blob_sizes.lbs_msg_msg);
init_debug("sock blob size = %d\n", blob_sizes.lbs_sock);
init_debug("superblock blob size = %d\n", blob_sizes.lbs_superblock);
@ -718,6 +722,29 @@ static int lsm_ipc_alloc(struct kern_ipc_perm *kip)
return 0;
}
#ifdef CONFIG_KEYS
/**
* lsm_key_alloc - allocate a composite key blob
* @key: the key that needs a blob
*
* Allocate the key blob for all the modules
*
* Returns 0, or -ENOMEM if memory can't be allocated.
*/
static int lsm_key_alloc(struct key *key)
{
if (blob_sizes.lbs_key == 0) {
key->security = NULL;
return 0;
}
key->security = kzalloc(blob_sizes.lbs_key, GFP_KERNEL);
if (key->security == NULL)
return -ENOMEM;
return 0;
}
#endif /* CONFIG_KEYS */
/**
* lsm_msg_msg_alloc - allocate a composite msg_msg blob
* @mp: the msg_msg that needs a blob
@ -5316,7 +5343,14 @@ EXPORT_SYMBOL(security_skb_classify_flow);
int security_key_alloc(struct key *key, const struct cred *cred,
unsigned long flags)
{
return call_int_hook(key_alloc, key, cred, flags);
int rc = lsm_key_alloc(key);
if (unlikely(rc))
return rc;
rc = call_int_hook(key_alloc, key, cred, flags);
if (unlikely(rc))
security_key_free(key);
return rc;
}
/**
@ -5327,7 +5361,8 @@ int security_key_alloc(struct key *key, const struct cred *cred,
*/
void security_key_free(struct key *key)
{
call_void_hook(key_free, key);
kfree(key->security);
key->security = NULL;
}
/**

21
security/selinux/hooks.c
View File

@ -6663,11 +6663,7 @@ static int selinux_key_alloc(struct key *k, const struct cred *cred,
unsigned long flags)
{
const struct task_security_struct *tsec;
struct key_security_struct *ksec;
ksec = kzalloc(sizeof(struct key_security_struct), GFP_KERNEL);
if (!ksec)
return -ENOMEM;
struct key_security_struct *ksec = selinux_key(k);
tsec = selinux_cred(cred);
if (tsec->keycreate_sid)
@ -6675,18 +6671,9 @@ static int selinux_key_alloc(struct key *k, const struct cred *cred,
else
ksec->sid = tsec->sid;
k->security = ksec;
return 0;
}
static void selinux_key_free(struct key *k)
{
struct key_security_struct *ksec = k->security;
k->security = NULL;
kfree(ksec);
}
static int selinux_key_permission(key_ref_t key_ref,
const struct cred *cred,
enum key_need_perm need_perm)
@ -6727,14 +6714,14 @@ static int selinux_key_permission(key_ref_t key_ref,
sid = cred_sid(cred);
key = key_ref_to_ptr(key_ref);
ksec = key->security;
ksec = selinux_key(key);
return avc_has_perm(sid, ksec->sid, SECCLASS_KEY, perm, NULL);
}
static int selinux_key_getsecurity(struct key *key, char **_buffer)
{
struct key_security_struct *ksec = key->security;
struct key_security_struct *ksec = selinux_key(key);
char *context = NULL;
unsigned len;
int rc;
@ -6986,6 +6973,7 @@ struct lsm_blob_sizes selinux_blob_sizes __ro_after_init = {
.lbs_file = sizeof(struct file_security_struct),
.lbs_inode = sizeof(struct inode_security_struct),
.lbs_ipc = sizeof(struct ipc_security_struct),
.lbs_key = sizeof(struct key_security_struct),
.lbs_msg_msg = sizeof(struct msg_security_struct),
.lbs_sock = sizeof(struct sk_security_struct),
.lbs_superblock = sizeof(struct superblock_security_struct),
@ -7324,7 +7312,6 @@ static struct security_hook_list selinux_hooks[] __ro_after_init = {
#endif
#ifdef CONFIG_KEYS
LSM_HOOK_INIT(key_free, selinux_key_free),
LSM_HOOK_INIT(key_permission, selinux_key_permission),
LSM_HOOK_INIT(key_getsecurity, selinux_key_getsecurity),
#ifdef CONFIG_KEY_NOTIFICATIONS

7
security/selinux/include/objsec.h
View File

@ -195,6 +195,13 @@ selinux_superblock(const struct super_block *superblock)
return superblock->s_security + selinux_blob_sizes.lbs_superblock;
}
#ifdef CONFIG_KEYS
static inline struct key_security_struct *selinux_key(const struct key *key)
{
return key->security + selinux_blob_sizes.lbs_key;
}
#endif /* CONFIG_KEYS */
static inline struct sk_security_struct *selinux_sock(const struct sock *sock)
{
return sock->sk_security + selinux_blob_sizes.lbs_sock;

7
security/smack/smack.h
View File

@ -360,6 +360,13 @@ static inline struct socket_smack *smack_sock(const struct sock *sock)
return sock->sk_security + smack_blob_sizes.lbs_sock;
}
#ifdef CONFIG_KEYS
static inline struct smack_known **smack_key(const struct key *key)
{
return key->security + smack_blob_sizes.lbs_key;
}
#endif /* CONFIG_KEYS */
/*
* Is the directory transmuting?
*/

31
security/smack/smack_lsm.c
View File

@ -4504,23 +4504,13 @@ static void smack_inet_csk_clone(struct sock *sk,
static int smack_key_alloc(struct key *key, const struct cred *cred,
unsigned long flags)
{
struct smack_known **blob = smack_key(key);
struct smack_known *skp = smk_of_task(smack_cred(cred));
key->security = skp;
*blob = skp;
return 0;
}
/**
* smack_key_free - Clear the key security blob
* @key: the object
*
* Clear the blob pointer
*/
static void smack_key_free(struct key *key)
{
key->security = NULL;
}
/**
* smack_key_permission - Smack access on a key
* @key_ref: gets to the object
@ -4534,6 +4524,8 @@ static int smack_key_permission(key_ref_t key_ref,
const struct cred *cred,
enum key_need_perm need_perm)
{
struct smack_known **blob;
struct smack_known *skp;
struct key *keyp;
struct smk_audit_info ad;
struct smack_known *tkp = smk_of_task(smack_cred(cred));
@ -4571,7 +4563,9 @@ static int smack_key_permission(key_ref_t key_ref,
* If the key hasn't been initialized give it access so that
* it may do so.
*/
if (keyp->security == NULL)
blob = smack_key(keyp);
skp = *blob;
if (skp == NULL)
return 0;
/*
* This should not occur
@ -4587,8 +4581,8 @@ static int smack_key_permission(key_ref_t key_ref,
ad.a.u.key_struct.key = keyp->serial;
ad.a.u.key_struct.key_desc = keyp->description;
#endif
rc = smk_access(tkp, keyp->security, request, &ad);
rc = smk_bu_note("key access", tkp, keyp->security, request, rc);
rc = smk_access(tkp, skp, request, &ad);
rc = smk_bu_note("key access", tkp, skp, request, rc);
return rc;
}
@ -4603,11 +4597,12 @@ static int smack_key_permission(key_ref_t key_ref,
*/
static int smack_key_getsecurity(struct key *key, char **_buffer)
{
struct smack_known *skp = key->security;
struct smack_known **blob = smack_key(key);
struct smack_known *skp = *blob;
size_t length;
char *copy;
if (key->security == NULL) {
if (skp == NULL) {
*_buffer = NULL;
return 0;
}
@ -5041,6 +5036,7 @@ struct lsm_blob_sizes smack_blob_sizes __ro_after_init = {
.lbs_file = sizeof(struct smack_known *),
.lbs_inode = sizeof(struct inode_smack),
.lbs_ipc = sizeof(struct smack_known *),
.lbs_key = sizeof(struct smack_known *),
.lbs_msg_msg = sizeof(struct smack_known *),
.lbs_sock = sizeof(struct socket_smack),
.lbs_superblock = sizeof(struct superblock_smack),
@ -5178,7 +5174,6 @@ static struct security_hook_list smack_hooks[] __ro_after_init = {
/* key management security hooks */
#ifdef CONFIG_KEYS
LSM_HOOK_INIT(key_alloc, smack_key_alloc),
LSM_HOOK_INIT(key_free, smack_key_free),
LSM_HOOK_INIT(key_permission, smack_key_permission),
LSM_HOOK_INIT(key_getsecurity, smack_key_getsecurity),
#ifdef CONFIG_KEY_NOTIFICATIONS