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evm: Store and detect metadata inode attributes changes

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On stacked filesystem the metadata inode may be different than the one
file data inode and therefore changes to it need to be detected
independently. Therefore, store the i_version, device number, and inode
number associated with the file metadata inode.

Implement a function to detect changes to the inode and if a change is
detected reset the evm_status. This function will be called by IMA when
IMA detects that the metadata inode is different from the file's inode.

Co-developed-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
This commit is contained in:
Stefan Berger 2024-02-23 12:25:09 -05:00 committed by Mimi Zohar
parent 309e2b775d
commit a652aa5906
4 changed files with 57 additions and 10 deletions
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8
include/linux/evm.h
View File

@ -26,6 +26,8 @@ extern int evm_protected_xattr_if_enabled(const char *req_xattr_name);
extern int evm_read_protected_xattrs(struct dentry *dentry, u8 *buffer,
int buffer_size, char type,
bool canonical_fmt);
extern bool evm_metadata_changed(struct inode *inode,
struct inode *metadata_inode);
#ifdef CONFIG_FS_POSIX_ACL
extern int posix_xattr_acl(const char *xattrname);
#else
@ -76,5 +78,11 @@ static inline int evm_read_protected_xattrs(struct dentry *dentry, u8 *buffer,
return -EOPNOTSUPP;
}
static inline bool evm_metadata_changed(struct inode *inode,
struct inode *metadata_inode)
{
return false;
}
#endif /* CONFIG_EVM */
#endif /* LINUX_EVM_H */

6
security/integrity/evm/evm.h
View File

@ -39,6 +39,7 @@ struct xattr_list {
struct evm_iint_cache {
unsigned long flags;
enum integrity_status evm_status:4;
struct integrity_inode_attributes metadata_inode;
};
extern struct lsm_blob_sizes evm_blob_sizes;
@ -74,11 +75,12 @@ int evm_update_evmxattr(struct dentry *dentry,
size_t req_xattr_value_len);
int evm_calc_hmac(struct dentry *dentry, const char *req_xattr_name,
const char *req_xattr_value,
size_t req_xattr_value_len, struct evm_digest *data);
size_t req_xattr_value_len, struct evm_digest *data,
struct evm_iint_cache *iint);
int evm_calc_hash(struct dentry *dentry, const char *req_xattr_name,
const char *req_xattr_value,
size_t req_xattr_value_len, char type,
struct evm_digest *data);
struct evm_digest *data, struct evm_iint_cache *iint);
int evm_init_hmac(struct inode *inode, const struct xattr *xattrs,
char *hmac_val);
int evm_init_secfs(void);

23
security/integrity/evm/evm_crypto.c
View File

@ -221,7 +221,8 @@ static int evm_calc_hmac_or_hash(struct dentry *dentry,
const char *req_xattr_name,
const char *req_xattr_value,
size_t req_xattr_value_len,
uint8_t type, struct evm_digest *data)
uint8_t type, struct evm_digest *data,
struct evm_iint_cache *iint)
{
struct inode *inode = d_inode(d_real(dentry, D_REAL_METADATA));
struct xattr_list *xattr;
@ -231,6 +232,7 @@ static int evm_calc_hmac_or_hash(struct dentry *dentry,
int error;
int size, user_space_size;
bool ima_present = false;
u64 i_version = 0;
if (!(inode->i_opflags & IOP_XATTR) ||
inode->i_sb->s_user_ns != &init_user_ns)
@ -294,6 +296,13 @@ static int evm_calc_hmac_or_hash(struct dentry *dentry,
}
hmac_add_misc(desc, inode, type, data->digest);
if (inode != d_backing_inode(dentry) && iint) {
if (IS_I_VERSION(inode))
i_version = inode_query_iversion(inode);
integrity_inode_attrs_store(&iint->metadata_inode, i_version,
inode);
}
/* Portable EVM signatures must include an IMA hash */
if (type == EVM_XATTR_PORTABLE_DIGSIG && !ima_present)
error = -EPERM;
@ -305,18 +314,19 @@ out:
int evm_calc_hmac(struct dentry *dentry, const char *req_xattr_name,
const char *req_xattr_value, size_t req_xattr_value_len,
struct evm_digest *data)
struct evm_digest *data, struct evm_iint_cache *iint)
{
return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value,
req_xattr_value_len, EVM_XATTR_HMAC, data);
req_xattr_value_len, EVM_XATTR_HMAC, data,
iint);
}
int evm_calc_hash(struct dentry *dentry, const char *req_xattr_name,
const char *req_xattr_value, size_t req_xattr_value_len,
char type, struct evm_digest *data)
char type, struct evm_digest *data, struct evm_iint_cache *iint)
{
return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value,
req_xattr_value_len, type, data);
req_xattr_value_len, type, data, iint);
}
static int evm_is_immutable(struct dentry *dentry, struct inode *inode)
@ -357,6 +367,7 @@ int evm_update_evmxattr(struct dentry *dentry, const char *xattr_name,
const char *xattr_value, size_t xattr_value_len)
{
struct inode *inode = d_backing_inode(dentry);
struct evm_iint_cache *iint = evm_iint_inode(inode);
struct evm_digest data;
int rc = 0;
@ -372,7 +383,7 @@ int evm_update_evmxattr(struct dentry *dentry, const char *xattr_name,
data.hdr.algo = HASH_ALGO_SHA1;
rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
xattr_value_len, &data);
xattr_value_len, &data, iint);
if (rc == 0) {
data.hdr.xattr.sha1.type = EVM_XATTR_HMAC;
rc = __vfs_setxattr_noperm(&nop_mnt_idmap, dentry,

30
security/integrity/evm/evm_main.c
View File

@ -226,7 +226,7 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry,
digest.hdr.algo = HASH_ALGO_SHA1;
rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
xattr_value_len, &digest);
xattr_value_len, &digest, iint);
if (rc)
break;
rc = crypto_memneq(xattr_data->data, digest.digest,
@ -247,7 +247,8 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry,
hdr = (struct signature_v2_hdr *)xattr_data;
digest.hdr.algo = hdr->hash_algo;
rc = evm_calc_hash(dentry, xattr_name, xattr_value,
xattr_value_len, xattr_data->type, &digest);
xattr_value_len, xattr_data->type, &digest,
iint);
if (rc)
break;
rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM,
@ -733,6 +734,31 @@ static void evm_reset_status(struct inode *inode)
iint->evm_status = INTEGRITY_UNKNOWN;
}
/**
* evm_metadata_changed: Detect changes to the metadata
* @inode: a file's inode
* @metadata_inode: metadata inode
*
* On a stacked filesystem detect whether the metadata has changed. If this is
* the case reset the evm_status associated with the inode that represents the
* file.
*/
bool evm_metadata_changed(struct inode *inode, struct inode *metadata_inode)
{
struct evm_iint_cache *iint = evm_iint_inode(inode);
bool ret = false;
if (iint) {
ret = (!IS_I_VERSION(metadata_inode) ||
integrity_inode_attrs_changed(&iint->metadata_inode,
metadata_inode));
if (ret)
iint->evm_status = INTEGRITY_UNKNOWN;
}
return ret;
}
/**
* evm_revalidate_status - report whether EVM status re-validation is necessary
* @xattr_name: pointer to the affected extended attribute name