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linux-stable/security/integrity/evm/evm_main.c

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// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2005-2010 IBM Corporation
*
* Author:
* Mimi Zohar <zohar@us.ibm.com>
* Kylene Hall <kjhall@us.ibm.com>
*
* File: evm_main.c
* implements evm_inode_setxattr, evm_inode_post_setxattr,
* evm_inode_removexattr, evm_verifyxattr, and evm_inode_set_acl.
*/
#define pr_fmt(fmt) "EVM: "fmt
#include <linux/init.h>
#include <linux/audit.h>
#include <linux/xattr.h>
#include <linux/integrity.h>
#include <linux/evm.h>
#include <linux/magic.h>
#include <linux/posix_acl_xattr.h>
#include <linux/lsm_hooks.h>
#include <crypto/hash.h>
#include <crypto/hash_info.h>
#include <crypto/utils.h>
#include "evm.h"
int evm_initialized;
static const char * const integrity_status_msg[] = {
"pass", "pass_immutable", "fail", "fail_immutable", "no_label",
"no_xattrs", "unknown"
};
int evm_hmac_attrs;
static struct xattr_list evm_config_default_xattrnames[] = {
{
.name = XATTR_NAME_SELINUX,
.enabled = IS_ENABLED(CONFIG_SECURITY_SELINUX)
},
{
.name = XATTR_NAME_SMACK,
.enabled = IS_ENABLED(CONFIG_SECURITY_SMACK)
},
{
.name = XATTR_NAME_SMACKEXEC,
.enabled = IS_ENABLED(CONFIG_EVM_EXTRA_SMACK_XATTRS)
},
{
.name = XATTR_NAME_SMACKTRANSMUTE,
.enabled = IS_ENABLED(CONFIG_EVM_EXTRA_SMACK_XATTRS)
},
{
.name = XATTR_NAME_SMACKMMAP,
.enabled = IS_ENABLED(CONFIG_EVM_EXTRA_SMACK_XATTRS)
},
{
.name = XATTR_NAME_APPARMOR,
.enabled = IS_ENABLED(CONFIG_SECURITY_APPARMOR)
},
{
.name = XATTR_NAME_IMA,
.enabled = IS_ENABLED(CONFIG_IMA_APPRAISE)
},
{
.name = XATTR_NAME_CAPS,
.enabled = true
},
};
LIST_HEAD(evm_config_xattrnames);
static int evm_fixmode __ro_after_init;
static int __init evm_set_fixmode(char *str)
{
if (strncmp(str, "fix", 3) == 0)
evm_fixmode = 1;
else
pr_err("invalid \"%s\" mode", str);
return 1;
}
__setup("evm=", evm_set_fixmode);
static void __init evm_init_config(void)
{
int i, xattrs;
xattrs = ARRAY_SIZE(evm_config_default_xattrnames);
pr_info("Initialising EVM extended attributes:\n");
for (i = 0; i < xattrs; i++) {
pr_info("%s%s\n", evm_config_default_xattrnames[i].name,
!evm_config_default_xattrnames[i].enabled ?
" (disabled)" : "");
list_add_tail(&evm_config_default_xattrnames[i].list,
&evm_config_xattrnames);
}
#ifdef CONFIG_EVM_ATTR_FSUUID
evm_hmac_attrs |= EVM_ATTR_FSUUID;
#endif
pr_info("HMAC attrs: 0x%x\n", evm_hmac_attrs);
}
static bool evm_key_loaded(void)
{
return (bool)(evm_initialized & EVM_KEY_MASK);
}
/*
* This function determines whether or not it is safe to ignore verification
* errors, based on the ability of EVM to calculate HMACs. If the HMAC key
* is not loaded, and it cannot be loaded in the future due to the
* EVM_SETUP_COMPLETE initialization flag, allowing an operation despite the
* attrs/xattrs being found invalid will not make them valid.
*/
static bool evm_hmac_disabled(void)
{
if (evm_initialized & EVM_INIT_HMAC)
return false;
if (!(evm_initialized & EVM_SETUP_COMPLETE))
return false;
return true;
}
static int evm_find_protected_xattrs(struct dentry *dentry)
{
struct inode *inode = d_backing_inode(dentry);
struct xattr_list *xattr;
int error;
int count = 0;
if (!(inode->i_opflags & IOP_XATTR))
return -EOPNOTSUPP;
list_for_each_entry_lockless(xattr, &evm_config_xattrnames, list) {
error = __vfs_getxattr(dentry, inode, xattr->name, NULL, 0);
if (error < 0) {
if (error == -ENODATA)
continue;
return error;
}
count++;
}
return count;
}
static int is_unsupported_fs(struct dentry *dentry)
{
struct inode *inode = d_backing_inode(dentry);
if (inode->i_sb->s_iflags & SB_I_EVM_UNSUPPORTED) {
pr_info_once("%s not supported\n", inode->i_sb->s_type->name);
return 1;
}
return 0;
}
/*
* evm_verify_hmac - calculate and compare the HMAC with the EVM xattr
*
* Compute the HMAC on the dentry's protected set of extended attributes
* and compare it against the stored security.evm xattr.
*
* For performance:
* - use the previoulsy retrieved xattr value and length to calculate the
* HMAC.)
* - cache the verification result in the iint, when available.
*
* Returns integrity status
*/
static enum integrity_status evm_verify_hmac(struct dentry *dentry,
const char *xattr_name,
char *xattr_value,
size_t xattr_value_len)
{
struct evm_ima_xattr_data *xattr_data = NULL;
struct signature_v2_hdr *hdr;
enum integrity_status evm_status = INTEGRITY_PASS;
struct evm_digest digest;
struct inode *inode = d_backing_inode(dentry);
struct evm_iint_cache *iint = evm_iint_inode(inode);
int rc, xattr_len, evm_immutable = 0;
if (iint && (iint->evm_status == INTEGRITY_PASS ||
iint->evm_status == INTEGRITY_PASS_IMMUTABLE))
return iint->evm_status;
if (is_unsupported_fs(dentry))
return INTEGRITY_UNKNOWN;
/* if status is not PASS, try to check again - against -ENOMEM */
/* first need to know the sig type */
rc = vfs_getxattr_alloc(&nop_mnt_idmap, dentry, XATTR_NAME_EVM,
(char **)&xattr_data, 0, GFP_NOFS);
if (rc <= 0) {
evm_status = INTEGRITY_FAIL;
if (rc == -ENODATA) {
rc = evm_find_protected_xattrs(dentry);
if (rc > 0)
evm_status = INTEGRITY_NOLABEL;
else if (rc == 0)
evm_status = INTEGRITY_NOXATTRS; /* new file */
} else if (rc == -EOPNOTSUPP) {
evm_status = INTEGRITY_UNKNOWN;
}
goto out;
}
xattr_len = rc;
/* check value type */
switch (xattr_data->type) {
case EVM_XATTR_HMAC:
if (xattr_len != sizeof(struct evm_xattr)) {
evm_status = INTEGRITY_FAIL;
goto out;
}
digest.hdr.algo = HASH_ALGO_SHA1;
rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
xattr_value_len, &digest);
if (rc)
break;
rc = crypto_memneq(xattr_data->data, digest.digest,
SHA1_DIGEST_SIZE);
if (rc)
rc = -EINVAL;
break;
case EVM_XATTR_PORTABLE_DIGSIG:
evm_immutable = 1;
fallthrough;
case EVM_IMA_XATTR_DIGSIG:
/* accept xattr with non-empty signature field */
if (xattr_len <= sizeof(struct signature_v2_hdr)) {
evm_status = INTEGRITY_FAIL;
goto out;
}
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);
if (rc)
break;
rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM,
(const char *)xattr_data, xattr_len,
digest.digest, digest.hdr.length);
if (!rc) {
if (xattr_data->type == EVM_XATTR_PORTABLE_DIGSIG) {
if (iint)
iint->flags |= EVM_IMMUTABLE_DIGSIG;
evm_status = INTEGRITY_PASS_IMMUTABLE;
} else if (!IS_RDONLY(inode) &&
!(inode->i_sb->s_readonly_remount) &&
!IS_IMMUTABLE(inode)) {
evm_update_evmxattr(dentry, xattr_name,
xattr_value,
xattr_value_len);
}
}
break;
default:
rc = -EINVAL;
break;
}
if (rc) {
if (rc == -ENODATA)
evm_status = INTEGRITY_NOXATTRS;
else if (evm_immutable)
evm_status = INTEGRITY_FAIL_IMMUTABLE;
else
evm_status = INTEGRITY_FAIL;
}
pr_debug("digest: (%d) [%*phN]\n", digest.hdr.length, digest.hdr.length,
digest.digest);
out:
if (iint)
iint->evm_status = evm_status;
kfree(xattr_data);
return evm_status;
}
static int evm_protected_xattr_common(const char *req_xattr_name,
bool all_xattrs)
{
int namelen;
int found = 0;
struct xattr_list *xattr;
namelen = strlen(req_xattr_name);
list_for_each_entry_lockless(xattr, &evm_config_xattrnames, list) {
if (!all_xattrs && !xattr->enabled)
continue;
if ((strlen(xattr->name) == namelen)
&& (strncmp(req_xattr_name, xattr->name, namelen) == 0)) {
found = 1;
break;
}
if (strncmp(req_xattr_name,
xattr->name + XATTR_SECURITY_PREFIX_LEN,
strlen(req_xattr_name)) == 0) {
found = 1;
break;
}
}
return found;
}
int evm_protected_xattr(const char *req_xattr_name)
{
return evm_protected_xattr_common(req_xattr_name, false);
}
int evm_protected_xattr_if_enabled(const char *req_xattr_name)
{
return evm_protected_xattr_common(req_xattr_name, true);
}
/**
* evm_read_protected_xattrs - read EVM protected xattr names, lengths, values
* @dentry: dentry of the read xattrs
* @buffer: buffer xattr names, lengths or values are copied to
* @buffer_size: size of buffer
* @type: n: names, l: lengths, v: values
* @canonical_fmt: data format (true: little endian, false: native format)
*
* Read protected xattr names (separated by |), lengths (u32) or values for a
* given dentry and return the total size of copied data. If buffer is NULL,
* just return the total size.
*
* Returns the total size on success, a negative value on error.
*/
int evm_read_protected_xattrs(struct dentry *dentry, u8 *buffer,
int buffer_size, char type, bool canonical_fmt)
{
struct xattr_list *xattr;
int rc, size, total_size = 0;
list_for_each_entry_lockless(xattr, &evm_config_xattrnames, list) {
rc = __vfs_getxattr(dentry, d_backing_inode(dentry),
xattr->name, NULL, 0);
if (rc < 0 && rc == -ENODATA)
continue;
else if (rc < 0)
return rc;
switch (type) {
case 'n':
size = strlen(xattr->name) + 1;
if (buffer) {
if (total_size)
*(buffer + total_size - 1) = '|';
memcpy(buffer + total_size, xattr->name, size);
}
break;
case 'l':
size = sizeof(u32);
if (buffer) {
if (canonical_fmt)
rc = (__force int)cpu_to_le32(rc);
*(u32 *)(buffer + total_size) = rc;
}
break;
case 'v':
size = rc;
if (buffer) {
rc = __vfs_getxattr(dentry,
d_backing_inode(dentry), xattr->name,
buffer + total_size,
buffer_size - total_size);
if (rc < 0)
return rc;
}
break;
default:
return -EINVAL;
}
total_size += size;
}
return total_size;
}
/**
* evm_verifyxattr - verify the integrity of the requested xattr
* @dentry: object of the verify xattr
* @xattr_name: requested xattr
* @xattr_value: requested xattr value
* @xattr_value_len: requested xattr value length
*
* Calculate the HMAC for the given dentry and verify it against the stored
* security.evm xattr. For performance, use the xattr value and length
* previously retrieved to calculate the HMAC.
*
* Returns the xattr integrity status.
*
* This function requires the caller to lock the inode's i_mutex before it
* is executed.
*/
enum integrity_status evm_verifyxattr(struct dentry *dentry,
const char *xattr_name,
void *xattr_value, size_t xattr_value_len)
{
if (!evm_key_loaded() || !evm_protected_xattr(xattr_name))
return INTEGRITY_UNKNOWN;
if (is_unsupported_fs(dentry))
return INTEGRITY_UNKNOWN;
return evm_verify_hmac(dentry, xattr_name, xattr_value,
xattr_value_len);
}
EXPORT_SYMBOL_GPL(evm_verifyxattr);
/*
* evm_verify_current_integrity - verify the dentry's metadata integrity
* @dentry: pointer to the affected dentry
*
* Verify and return the dentry's metadata integrity. The exceptions are
* before EVM is initialized or in 'fix' mode.
*/
static enum integrity_status evm_verify_current_integrity(struct dentry *dentry)
{
struct inode *inode = d_backing_inode(dentry);
if (!evm_key_loaded() || !S_ISREG(inode->i_mode) || evm_fixmode)
return INTEGRITY_PASS;
return evm_verify_hmac(dentry, NULL, NULL, 0);
}
/*
* evm_xattr_change - check if passed xattr value differs from current value
* @idmap: idmap of the mount
* @dentry: pointer to the affected dentry
* @xattr_name: requested xattr
* @xattr_value: requested xattr value
* @xattr_value_len: requested xattr value length
*
* Check if passed xattr value differs from current value.
*
* Returns 1 if passed xattr value differs from current value, 0 otherwise.
*/
static int evm_xattr_change(struct mnt_idmap *idmap,
struct dentry *dentry, const char *xattr_name,
const void *xattr_value, size_t xattr_value_len)
{
char *xattr_data = NULL;
int rc = 0;
rc = vfs_getxattr_alloc(&nop_mnt_idmap, dentry, xattr_name, &xattr_data,
0, GFP_NOFS);
if (rc < 0) {
rc = 1;
goto out;
}
if (rc == xattr_value_len)
rc = !!memcmp(xattr_value, xattr_data, rc);
else
rc = 1;
out:
kfree(xattr_data);
return rc;
}
/*
* evm_protect_xattr - protect the EVM extended attribute
*
* Prevent security.evm from being modified or removed without the
* necessary permissions or when the existing value is invalid.
*
* The posix xattr acls are 'system' prefixed, which normally would not
* affect security.evm. An interesting side affect of writing posix xattr
* acls is their modifying of the i_mode, which is included in security.evm.
* For posix xattr acls only, permit security.evm, even if it currently
* doesn't exist, to be updated unless the EVM signature is immutable.
*/
static int evm_protect_xattr(struct mnt_idmap *idmap,
struct dentry *dentry, const char *xattr_name,
const void *xattr_value, size_t xattr_value_len)
{
enum integrity_status evm_status;
if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
if (is_unsupported_fs(dentry))
return -EPERM;
} else if (!evm_protected_xattr(xattr_name)) {
if (!posix_xattr_acl(xattr_name))
return 0;
if (is_unsupported_fs(dentry))
return 0;
evm_status = evm_verify_current_integrity(dentry);
if ((evm_status == INTEGRITY_PASS) ||
(evm_status == INTEGRITY_NOXATTRS))
return 0;
goto out;
} else if (is_unsupported_fs(dentry))
return 0;
evm_status = evm_verify_current_integrity(dentry);
if (evm_status == INTEGRITY_NOXATTRS) {
struct evm_iint_cache *iint;
/* Exception if the HMAC is not going to be calculated. */
if (evm_hmac_disabled())
return 0;
iint = evm_iint_inode(d_backing_inode(dentry));
if (iint && (iint->flags & EVM_NEW_FILE))
return 0;
/* exception for pseudo filesystems */
if (dentry->d_sb->s_magic == TMPFS_MAGIC
|| dentry->d_sb->s_magic == SYSFS_MAGIC)
return 0;
integrity_audit_msg(AUDIT_INTEGRITY_METADATA,
dentry->d_inode, dentry->d_name.name,
"update_metadata",
integrity_status_msg[evm_status],
-EPERM, 0);
}
out:
/* Exception if the HMAC is not going to be calculated. */
if (evm_hmac_disabled() && (evm_status == INTEGRITY_NOLABEL ||
evm_status == INTEGRITY_UNKNOWN))
return 0;
/*
* Writing other xattrs is safe for portable signatures, as portable
* signatures are immutable and can never be updated.
*/
if (evm_status == INTEGRITY_FAIL_IMMUTABLE)
return 0;
if (evm_status == INTEGRITY_PASS_IMMUTABLE &&
!evm_xattr_change(idmap, dentry, xattr_name, xattr_value,
xattr_value_len))
return 0;
if (evm_status != INTEGRITY_PASS &&
evm_status != INTEGRITY_PASS_IMMUTABLE)
integrity_audit_msg(AUDIT_INTEGRITY_METADATA, d_backing_inode(dentry),
dentry->d_name.name, "appraise_metadata",
integrity_status_msg[evm_status],
-EPERM, 0);
return evm_status == INTEGRITY_PASS ? 0 : -EPERM;
}
/**
* evm_inode_setxattr - protect the EVM extended attribute
* @idmap: idmap of the mount
* @dentry: pointer to the affected dentry
* @xattr_name: pointer to the affected extended attribute name
* @xattr_value: pointer to the new extended attribute value
* @xattr_value_len: pointer to the new extended attribute value length
* @flags: flags to pass into filesystem operations
*
* Before allowing the 'security.evm' protected xattr to be updated,
* verify the existing value is valid. As only the kernel should have
* access to the EVM encrypted key needed to calculate the HMAC, prevent
* userspace from writing HMAC value. Writing 'security.evm' requires
* requires CAP_SYS_ADMIN privileges.
*/
static int evm_inode_setxattr(struct mnt_idmap *idmap, struct dentry *dentry,
const char *xattr_name, const void *xattr_value,
size_t xattr_value_len, int flags)
{
const struct evm_ima_xattr_data *xattr_data = xattr_value;
/* Policy permits modification of the protected xattrs even though
* there's no HMAC key loaded
*/
if (evm_initialized & EVM_ALLOW_METADATA_WRITES)
return 0;
if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
if (!xattr_value_len)
return -EINVAL;
if (xattr_data->type != EVM_IMA_XATTR_DIGSIG &&
xattr_data->type != EVM_XATTR_PORTABLE_DIGSIG)
return -EPERM;
}
return evm_protect_xattr(idmap, dentry, xattr_name, xattr_value,
xattr_value_len);
}
/**
* evm_inode_removexattr - protect the EVM extended attribute
* @idmap: idmap of the mount
* @dentry: pointer to the affected dentry
* @xattr_name: pointer to the affected extended attribute name
*
* Removing 'security.evm' requires CAP_SYS_ADMIN privileges and that
* the current value is valid.
*/
static int evm_inode_removexattr(struct mnt_idmap *idmap, struct dentry *dentry,
const char *xattr_name)
{
/* Policy permits modification of the protected xattrs even though
* there's no HMAC key loaded
*/
if (evm_initialized & EVM_ALLOW_METADATA_WRITES)
return 0;
return evm_protect_xattr(idmap, dentry, xattr_name, NULL, 0);
}
#ifdef CONFIG_FS_POSIX_ACL
static int evm_inode_set_acl_change(struct mnt_idmap *idmap,
struct dentry *dentry, const char *name,
struct posix_acl *kacl)
{
int rc;
umode_t mode;
struct inode *inode = d_backing_inode(dentry);
if (!kacl)
return 1;
rc = posix_acl_update_mode(idmap, inode, &mode, &kacl);
if (rc || (inode->i_mode != mode))
return 1;
return 0;
}
#else
static inline int evm_inode_set_acl_change(struct mnt_idmap *idmap,
struct dentry *dentry,
const char *name,
struct posix_acl *kacl)
{
return 0;
}
#endif
/**
* evm_inode_set_acl - protect the EVM extended attribute from posix acls
* @idmap: idmap of the idmapped mount
* @dentry: pointer to the affected dentry
* @acl_name: name of the posix acl
* @kacl: pointer to the posix acls
*
* Prevent modifying posix acls causing the EVM HMAC to be re-calculated
* and 'security.evm' xattr updated, unless the existing 'security.evm' is
* valid.
*
* Return: zero on success, -EPERM on failure.
*/
static int evm_inode_set_acl(struct mnt_idmap *idmap, struct dentry *dentry,
const char *acl_name, struct posix_acl *kacl)
{
enum integrity_status evm_status;
/* Policy permits modification of the protected xattrs even though
* there's no HMAC key loaded
*/
if (evm_initialized & EVM_ALLOW_METADATA_WRITES)
return 0;
evm_status = evm_verify_current_integrity(dentry);
if ((evm_status == INTEGRITY_PASS) ||
(evm_status == INTEGRITY_NOXATTRS))
return 0;
/* Exception if the HMAC is not going to be calculated. */
if (evm_hmac_disabled() && (evm_status == INTEGRITY_NOLABEL ||
evm_status == INTEGRITY_UNKNOWN))
return 0;
/*
* Writing other xattrs is safe for portable signatures, as portable
* signatures are immutable and can never be updated.
*/
if (evm_status == INTEGRITY_FAIL_IMMUTABLE)
return 0;
if (evm_status == INTEGRITY_PASS_IMMUTABLE &&
!evm_inode_set_acl_change(idmap, dentry, acl_name, kacl))
return 0;
if (evm_status != INTEGRITY_PASS_IMMUTABLE)
integrity_audit_msg(AUDIT_INTEGRITY_METADATA, d_backing_inode(dentry),
dentry->d_name.name, "appraise_metadata",
integrity_status_msg[evm_status],
-EPERM, 0);
return -EPERM;
}
/**
* evm_inode_remove_acl - Protect the EVM extended attribute from posix acls
* @idmap: idmap of the mount
* @dentry: pointer to the affected dentry
* @acl_name: name of the posix acl
*
* Prevent removing posix acls causing the EVM HMAC to be re-calculated
* and 'security.evm' xattr updated, unless the existing 'security.evm' is
* valid.
*
* Return: zero on success, -EPERM on failure.
*/
static int evm_inode_remove_acl(struct mnt_idmap *idmap, struct dentry *dentry,
const char *acl_name)
{
return evm_inode_set_acl(idmap, dentry, acl_name, NULL);
}
static void evm_reset_status(struct inode *inode)
{
struct evm_iint_cache *iint;
iint = evm_iint_inode(inode);
if (iint)
iint->evm_status = INTEGRITY_UNKNOWN;
}
/**
* evm_revalidate_status - report whether EVM status re-validation is necessary
* @xattr_name: pointer to the affected extended attribute name
*
* Report whether callers of evm_verifyxattr() should re-validate the
* EVM status.
*
* Return true if re-validation is necessary, false otherwise.
*/
bool evm_revalidate_status(const char *xattr_name)
{
if (!evm_key_loaded())
return false;
/* evm_inode_post_setattr() passes NULL */
if (!xattr_name)
return true;
if (!evm_protected_xattr(xattr_name) && !posix_xattr_acl(xattr_name) &&
strcmp(xattr_name, XATTR_NAME_EVM))
return false;
return true;
}
/**
* evm_inode_post_setxattr - update 'security.evm' to reflect the changes
* @dentry: pointer to the affected dentry
* @xattr_name: pointer to the affected extended attribute name
* @xattr_value: pointer to the new extended attribute value
* @xattr_value_len: pointer to the new extended attribute value length
* @flags: flags to pass into filesystem operations
*
* Update the HMAC stored in 'security.evm' to reflect the change.
*
* No need to take the i_mutex lock here, as this function is called from
* __vfs_setxattr_noperm(). The caller of which has taken the inode's
* i_mutex lock.
*/
static void evm_inode_post_setxattr(struct dentry *dentry,
const char *xattr_name,
const void *xattr_value,
size_t xattr_value_len,
int flags)
{
if (!evm_revalidate_status(xattr_name))
return;
evm_reset_status(dentry->d_inode);
if (!strcmp(xattr_name, XATTR_NAME_EVM))
return;
if (!(evm_initialized & EVM_INIT_HMAC))
return;
if (is_unsupported_fs(dentry))
return;
evm_update_evmxattr(dentry, xattr_name, xattr_value, xattr_value_len);
}
/**
* evm_inode_post_set_acl - Update the EVM extended attribute from posix acls
* @dentry: pointer to the affected dentry
* @acl_name: name of the posix acl
* @kacl: pointer to the posix acls
*
* Update the 'security.evm' xattr with the EVM HMAC re-calculated after setting
* posix acls.
*/
static void evm_inode_post_set_acl(struct dentry *dentry, const char *acl_name,
struct posix_acl *kacl)
{
return evm_inode_post_setxattr(dentry, acl_name, NULL, 0, 0);
}
/**
* evm_inode_post_removexattr - update 'security.evm' after removing the xattr
* @dentry: pointer to the affected dentry
* @xattr_name: pointer to the affected extended attribute name
*
* Update the HMAC stored in 'security.evm' to reflect removal of the xattr.
*
* No need to take the i_mutex lock here, as this function is called from
* vfs_removexattr() which takes the i_mutex.
*/
static void evm_inode_post_removexattr(struct dentry *dentry,
const char *xattr_name)
{
if (!evm_revalidate_status(xattr_name))
return;
evm_reset_status(dentry->d_inode);
if (!strcmp(xattr_name, XATTR_NAME_EVM))
return;
if (!(evm_initialized & EVM_INIT_HMAC))
return;
evm_update_evmxattr(dentry, xattr_name, NULL, 0);
}
/**
* evm_inode_post_remove_acl - Update the EVM extended attribute from posix acls
* @idmap: idmap of the mount
* @dentry: pointer to the affected dentry
* @acl_name: name of the posix acl
*
* Update the 'security.evm' xattr with the EVM HMAC re-calculated after
* removing posix acls.
*/
static inline void evm_inode_post_remove_acl(struct mnt_idmap *idmap,
struct dentry *dentry,
const char *acl_name)
{
evm_inode_post_removexattr(dentry, acl_name);
}
static int evm_attr_change(struct mnt_idmap *idmap,
struct dentry *dentry, struct iattr *attr)
{
struct inode *inode = d_backing_inode(dentry);
unsigned int ia_valid = attr->ia_valid;
if (!i_uid_needs_update(idmap, attr, inode) &&
!i_gid_needs_update(idmap, attr, inode) &&
(!(ia_valid & ATTR_MODE) || attr->ia_mode == inode->i_mode))
return 0;
return 1;
}
/**
* evm_inode_setattr - prevent updating an invalid EVM extended attribute
* @idmap: idmap of the mount
* @dentry: pointer to the affected dentry
* @attr: iattr structure containing the new file attributes
*
* Permit update of file attributes when files have a valid EVM signature,
* except in the case of them having an immutable portable signature.
*/
static int evm_inode_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
struct iattr *attr)
{
unsigned int ia_valid = attr->ia_valid;
enum integrity_status evm_status;
/* Policy permits modification of the protected attrs even though
* there's no HMAC key loaded
*/
if (evm_initialized & EVM_ALLOW_METADATA_WRITES)
return 0;
if (is_unsupported_fs(dentry))
return 0;
if (!(ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)))
return 0;
evm_status = evm_verify_current_integrity(dentry);
/*
* Writing attrs is safe for portable signatures, as portable signatures
* are immutable and can never be updated.
*/
if ((evm_status == INTEGRITY_PASS) ||
(evm_status == INTEGRITY_NOXATTRS) ||
(evm_status == INTEGRITY_FAIL_IMMUTABLE) ||
(evm_hmac_disabled() && (evm_status == INTEGRITY_NOLABEL ||
evm_status == INTEGRITY_UNKNOWN)))
return 0;
if (evm_status == INTEGRITY_PASS_IMMUTABLE &&
!evm_attr_change(idmap, dentry, attr))
return 0;
integrity_audit_msg(AUDIT_INTEGRITY_METADATA, d_backing_inode(dentry),
dentry->d_name.name, "appraise_metadata",
integrity_status_msg[evm_status], -EPERM, 0);
return -EPERM;
}
/**
* evm_inode_post_setattr - update 'security.evm' after modifying metadata
* @idmap: idmap of the idmapped mount
* @dentry: pointer to the affected dentry
* @ia_valid: for the UID and GID status
*
* For now, update the HMAC stored in 'security.evm' to reflect UID/GID
* changes.
*
* This function is called from notify_change(), which expects the caller
* to lock the inode's i_mutex.
*/
static void evm_inode_post_setattr(struct mnt_idmap *idmap,
struct dentry *dentry, int ia_valid)
{
if (!evm_revalidate_status(NULL))
return;
evm_reset_status(dentry->d_inode);
if (!(evm_initialized & EVM_INIT_HMAC))
return;
if (is_unsupported_fs(dentry))
return;
if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
evm_update_evmxattr(dentry, NULL, NULL, 0);
}
static int evm_inode_copy_up_xattr(const char *name)
{
if (strcmp(name, XATTR_NAME_EVM) == 0)
return 1; /* Discard */
return -EOPNOTSUPP;
}
/*
* evm_inode_init_security - initializes security.evm HMAC value
*/
int evm_inode_init_security(struct inode *inode, struct inode *dir,
const struct qstr *qstr, struct xattr *xattrs,
int *xattr_count)
{
struct evm_xattr *xattr_data;
struct xattr *xattr, *evm_xattr;
bool evm_protected_xattrs = false;
int rc;
if (!(evm_initialized & EVM_INIT_HMAC) || !xattrs)
return 0;
/*
* security_inode_init_security() makes sure that the xattrs array is
* contiguous, there is enough space for security.evm, and that there is
* a terminator at the end of the array.
*/
for (xattr = xattrs; xattr->name; xattr++) {
if (evm_protected_xattr(xattr->name))
evm_protected_xattrs = true;
}
/* EVM xattr not needed. */
if (!evm_protected_xattrs)
return 0;
evm_xattr = lsm_get_xattr_slot(xattrs, xattr_count);
/*
* Array terminator (xattr name = NULL) must be the first non-filled
* xattr slot.
*/
WARN_ONCE(evm_xattr != xattr,
"%s: xattrs terminator is not the first non-filled slot\n",
__func__);
xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS);
if (!xattr_data)
return -ENOMEM;
xattr_data->data.type = EVM_XATTR_HMAC;
rc = evm_init_hmac(inode, xattrs, xattr_data->digest);
if (rc < 0)
goto out;
evm_xattr->value = xattr_data;
evm_xattr->value_len = sizeof(*xattr_data);
evm_xattr->name = XATTR_EVM_SUFFIX;
return 0;
out:
kfree(xattr_data);
return rc;
}
EXPORT_SYMBOL_GPL(evm_inode_init_security);
static int evm_inode_alloc_security(struct inode *inode)
{
struct evm_iint_cache *iint = evm_iint_inode(inode);
/* Called by security_inode_alloc(), it cannot be NULL. */
iint->flags = 0UL;
iint->evm_status = INTEGRITY_UNKNOWN;
return 0;
}
static void evm_file_release(struct file *file)
{
struct inode *inode = file_inode(file);
struct evm_iint_cache *iint = evm_iint_inode(inode);
fmode_t mode = file->f_mode;
if (!S_ISREG(inode->i_mode) || !(mode & FMODE_WRITE))
return;
if (iint && atomic_read(&inode->i_writecount) == 1)
iint->flags &= ~EVM_NEW_FILE;
}
static void evm_post_path_mknod(struct mnt_idmap *idmap, struct dentry *dentry)
{
struct inode *inode = d_backing_inode(dentry);
struct evm_iint_cache *iint = evm_iint_inode(inode);
if (!S_ISREG(inode->i_mode))
return;
if (iint)
iint->flags |= EVM_NEW_FILE;
}
#ifdef CONFIG_EVM_LOAD_X509
void __init evm_load_x509(void)
{
int rc;
rc = integrity_load_x509(INTEGRITY_KEYRING_EVM, CONFIG_EVM_X509_PATH);
if (!rc)
evm_initialized |= EVM_INIT_X509;
}
#endif
static int __init init_evm(void)
{
int error;
struct list_head *pos, *q;
evm_init_config();
error = integrity_init_keyring(INTEGRITY_KEYRING_EVM);
if (error)
goto error;
error = evm_init_secfs();
if (error < 0) {
pr_info("Error registering secfs\n");
goto error;
}
error:
if (error != 0) {
if (!list_empty(&evm_config_xattrnames)) {
list_for_each_safe(pos, q, &evm_config_xattrnames)
list_del(pos);
}
}
return error;
}
static struct security_hook_list evm_hooks[] __ro_after_init = {
LSM_HOOK_INIT(inode_setattr, evm_inode_setattr),
LSM_HOOK_INIT(inode_post_setattr, evm_inode_post_setattr),
LSM_HOOK_INIT(inode_copy_up_xattr, evm_inode_copy_up_xattr),
LSM_HOOK_INIT(inode_setxattr, evm_inode_setxattr),
LSM_HOOK_INIT(inode_post_setxattr, evm_inode_post_setxattr),
LSM_HOOK_INIT(inode_set_acl, evm_inode_set_acl),
LSM_HOOK_INIT(inode_post_set_acl, evm_inode_post_set_acl),
LSM_HOOK_INIT(inode_remove_acl, evm_inode_remove_acl),
LSM_HOOK_INIT(inode_post_remove_acl, evm_inode_post_remove_acl),
LSM_HOOK_INIT(inode_removexattr, evm_inode_removexattr),
LSM_HOOK_INIT(inode_post_removexattr, evm_inode_post_removexattr),
LSM_HOOK_INIT(inode_init_security, evm_inode_init_security),
LSM_HOOK_INIT(inode_alloc_security, evm_inode_alloc_security),
LSM_HOOK_INIT(file_release, evm_file_release),
LSM_HOOK_INIT(path_post_mknod, evm_post_path_mknod),
};
static const struct lsm_id evm_lsmid = {
.name = "evm",
.id = LSM_ID_EVM,
};
static int __init init_evm_lsm(void)
{
security_add_hooks(evm_hooks, ARRAY_SIZE(evm_hooks), &evm_lsmid);
return 0;
}
struct lsm_blob_sizes evm_blob_sizes __ro_after_init = {
.lbs_inode = sizeof(struct evm_iint_cache),
.lbs_xattr_count = 1,
};
DEFINE_LSM(evm) = {
.name = "evm",
.init = init_evm_lsm,
.order = LSM_ORDER_LAST,
.blobs = &evm_blob_sizes,
};
late_initcall(init_evm);
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