Resguardo inicial

linux-7.2.3/security/integrity/evm/Kconfig

@@ -0,0 +1,76 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config EVM
+	bool "EVM support"
+	select KEYS
+	select ENCRYPTED_KEYS
+	select CRYPTO_HMAC
+	select CRYPTO_SHA1
+	select CRYPTO_HASH_INFO
+	select SECURITY_PATH
+	default n
+	help
+	  EVM protects a file's security extended attributes against
+	  integrity attacks.
+
+	  If you are unsure how to answer this question, answer N.
+
+config EVM_ATTR_FSUUID
+	bool "FSUUID (version 2)"
+	default y
+	depends on EVM
+	help
+	  Include filesystem UUID for HMAC calculation.
+
+	  Default value is 'selected', which is former version 2.
+	  if 'not selected', it is former version 1
+
+	  WARNING: changing the HMAC calculation method or adding
+	  additional info to the calculation, requires existing EVM
+	  labeled file systems to be relabeled.
+
+config EVM_EXTRA_SMACK_XATTRS
+	bool "Additional SMACK xattrs"
+	depends on EVM && SECURITY_SMACK
+	default n
+	help
+	  Include additional SMACK xattrs for HMAC calculation.
+
+	  In addition to the original security xattrs (eg. security.selinux,
+	  security.SMACK64, security.capability, and security.ima) included
+	  in the HMAC calculation, enabling this option includes newly defined
+	  Smack xattrs: security.SMACK64EXEC, security.SMACK64TRANSMUTE and
+	  security.SMACK64MMAP.
+
+	  WARNING: changing the HMAC calculation method or adding
+	  additional info to the calculation, requires existing EVM
+	  labeled file systems to be relabeled.
+
+config EVM_ADD_XATTRS
+	bool "Add additional EVM extended attributes at runtime"
+	depends on EVM
+	default n
+	help
+	  Allow userland to provide additional xattrs for HMAC calculation.
+
+	  When this option is enabled, root can add additional xattrs to the
+	  list used by EVM by writing them into
+	  /sys/kernel/security/integrity/evm/evm_xattrs.
+
+config EVM_LOAD_X509
+	bool "Load an X509 certificate onto the '.evm' trusted keyring"
+	depends on EVM && INTEGRITY_TRUSTED_KEYRING
+	default n
+	help
+	   Load an X509 certificate onto the '.evm' trusted keyring.
+
+	   This option enables X509 certificate loading from the kernel
+	   onto the '.evm' trusted keyring.  A public key can be used to
+	   verify EVM integrity starting from the 'init' process. The
+	   key must have digitalSignature usage set.
+
+config EVM_X509_PATH
+	string "EVM X509 certificate path"
+	depends on EVM_LOAD_X509
+	default "/etc/keys/x509_evm.der"
+	help
+	   This option defines X509 certificate path.

linux-7.2.3/security/integrity/evm/Makefile

@@ -0,0 +1,8 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Makefile for building the Extended Verification Module(EVM)
+#
+obj-$(CONFIG_EVM) += evm.o
+
+evm-y := evm_main.o evm_crypto.o evm_secfs.o
+evm-$(CONFIG_FS_POSIX_ACL) += evm_posix_acl.o

linux-7.2.3/security/integrity/evm/evm.h

@@ -0,0 +1,89 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2005-2010 IBM Corporation
+ *
+ * Authors:
+ * Mimi Zohar <zohar@us.ibm.com>
+ * Kylene Hall <kjhall@us.ibm.com>
+ *
+ * File: evm.h
+ */
+
+#ifndef __INTEGRITY_EVM_H
+#define __INTEGRITY_EVM_H
+
+#include <linux/xattr.h>
+#include <linux/security.h>
+
+#include "../integrity.h"
+
+#define EVM_INIT_HMAC	0x0001
+#define EVM_INIT_X509	0x0002
+#define EVM_ALLOW_METADATA_WRITES	0x0004
+#define EVM_SIGV3_REQUIRED		0x0008
+#define EVM_SETUP_COMPLETE 0x80000000 /* userland has signaled key load */
+
+#define EVM_KEY_MASK (EVM_INIT_HMAC | EVM_INIT_X509)
+#define EVM_INIT_MASK (EVM_INIT_HMAC | EVM_INIT_X509 | EVM_SETUP_COMPLETE | \
+		       EVM_ALLOW_METADATA_WRITES | EVM_SIGV3_REQUIRED)
+
+struct xattr_list {
+	struct list_head list;
+	char *name;
+	bool enabled;
+};
+
+#define EVM_NEW_FILE			0x00000001
+#define EVM_IMMUTABLE_DIGSIG		0x00000002
+
+/* EVM integrity metadata associated with an inode */
+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;
+
+static inline struct evm_iint_cache *evm_iint_inode(const struct inode *inode)
+{
+	if (unlikely(!inode->i_security))
+		return NULL;
+
+	return inode->i_security + evm_blob_sizes.lbs_inode;
+}
+
+extern int evm_initialized;
+
+#define EVM_ATTR_FSUUID		0x0001
+
+extern int evm_hmac_attrs;
+
+/* List of EVM protected security xattrs */
+extern struct list_head evm_config_xattrnames;
+
+struct evm_digest {
+	struct ima_digest_data_hdr hdr;
+	char digest[IMA_MAX_DIGEST_SIZE];
+} __packed;
+
+int evm_protected_xattr(const char *req_xattr_name);
+
+int evm_init_key(void);
+int evm_update_evmxattr(struct dentry *dentry,
+			const char *req_xattr_name,
+			const char *req_xattr_value,
+			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,
+		  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_iint_cache *iint);
+int evm_init_hmac(struct inode *inode, const struct xattr *xattrs,
+		  char *hmac_val);
+int evm_init_secfs(void);
+
+#endif

linux-7.2.3/security/integrity/evm/evm_crypto.c

@@ -0,0 +1,459 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2005-2010 IBM Corporation
+ *
+ * Authors:
+ * Mimi Zohar <zohar@us.ibm.com>
+ * Kylene Hall <kjhall@us.ibm.com>
+ *
+ * File: evm_crypto.c
+ *	 Using root's kernel master key (kmk), calculate the HMAC
+ */
+
+#define pr_fmt(fmt) "EVM: "fmt
+
+#include <linux/export.h>
+#include <linux/hex.h>
+#include <linux/crypto.h>
+#include <linux/xattr.h>
+#include <linux/evm.h>
+#include <keys/encrypted-type.h>
+#include <crypto/hash.h>
+#include <crypto/hash_info.h>
+#include "evm.h"
+
+#define EVMKEY "evm-key"
+#define MAX_KEY_SIZE 128
+static unsigned char evmkey[MAX_KEY_SIZE];
+static const int evmkey_len = MAX_KEY_SIZE;
+
+static struct crypto_shash *hmac_tfm;
+static struct crypto_shash *evm_tfm[HASH_ALGO__LAST];
+
+static DEFINE_MUTEX(mutex);
+
+#define EVM_SET_KEY_BUSY 0
+
+static unsigned long evm_set_key_flags;
+
+static const char evm_hmac[] = "hmac(sha1)";
+
+/**
+ * evm_set_key() - set EVM HMAC key from the kernel
+ * @key: pointer to a buffer with the key data
+ * @keylen: length of the key data
+ *
+ * This function allows setting the EVM HMAC key from the kernel
+ * without using the "encrypted" key subsystem keys. It can be used
+ * by the crypto HW kernel module which has its own way of managing
+ * keys.
+ *
+ * key length should be between 32 and 128 bytes long
+ */
+int evm_set_key(void *key, size_t keylen)
+{
+	int rc;
+
+	rc = -EBUSY;
+	if (test_and_set_bit(EVM_SET_KEY_BUSY, &evm_set_key_flags))
+		goto busy;
+	rc = -EINVAL;
+	if (keylen > MAX_KEY_SIZE)
+		goto inval;
+	memcpy(evmkey, key, keylen);
+	evm_initialized |= EVM_INIT_HMAC;
+	pr_info("key initialized\n");
+	return 0;
+inval:
+	clear_bit(EVM_SET_KEY_BUSY, &evm_set_key_flags);
+busy:
+	pr_err("key initialization failed\n");
+	return rc;
+}
+EXPORT_SYMBOL_GPL(evm_set_key);
+
+static struct shash_desc *init_desc(char type, uint8_t hash_algo)
+{
+	long rc;
+	const char *algo;
+	struct crypto_shash **tfm, *tmp_tfm;
+	struct shash_desc *desc;
+
+	if (type == EVM_XATTR_HMAC) {
+		if (!(evm_initialized & EVM_INIT_HMAC)) {
+			pr_err_once("HMAC key is not set\n");
+			return ERR_PTR(-ENOKEY);
+		}
+		tfm = &hmac_tfm;
+		algo = evm_hmac;
+	} else {
+		if (hash_algo >= HASH_ALGO__LAST)
+			return ERR_PTR(-EINVAL);
+
+		tfm = &evm_tfm[hash_algo];
+		algo = hash_algo_name[hash_algo];
+	}
+
+	if (*tfm)
+		goto alloc;
+	mutex_lock(&mutex);
+	if (*tfm)
+		goto unlock;
+
+	tmp_tfm = crypto_alloc_shash(algo, 0, CRYPTO_NOLOAD);
+	if (IS_ERR(tmp_tfm)) {
+		pr_err("Can not allocate %s (reason: %ld)\n", algo,
+		       PTR_ERR(tmp_tfm));
+		mutex_unlock(&mutex);
+		return ERR_CAST(tmp_tfm);
+	}
+	if (type == EVM_XATTR_HMAC) {
+		rc = crypto_shash_setkey(tmp_tfm, evmkey, evmkey_len);
+		if (rc) {
+			crypto_free_shash(tmp_tfm);
+			mutex_unlock(&mutex);
+			return ERR_PTR(rc);
+		}
+	}
+	*tfm = tmp_tfm;
+unlock:
+	mutex_unlock(&mutex);
+alloc:
+	desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(*tfm),
+			GFP_KERNEL);
+	if (!desc)
+		return ERR_PTR(-ENOMEM);
+
+	desc->tfm = *tfm;
+
+	rc = crypto_shash_init(desc);
+	if (rc) {
+		kfree(desc);
+		return ERR_PTR(rc);
+	}
+	return desc;
+}
+
+/* Protect against 'cutting & pasting' security.evm xattr, include inode
+ * specific info.
+ *
+ * (Additional directory/file metadata needs to be added for more complete
+ * protection.)
+ */
+static void hmac_add_misc(struct shash_desc *desc, struct inode *inode,
+			  char type, char *digest)
+{
+	struct h_misc {
+		/*
+		 * Although inode->i_ino is now u64, this field remains
+		 * unsigned long to allow existing HMAC and signatures from
+		 * 32-bit hosts to continue working when i_ino hasn't changed
+		 * and fits in a u32.
+		 */
+		unsigned long ino;
+		__u32 generation;
+		uid_t uid;
+		gid_t gid;
+		umode_t mode;
+	} hmac_misc;
+
+	memset(&hmac_misc, 0, sizeof(hmac_misc));
+	/* Don't include the inode or generation number in portable
+	 * signatures
+	 */
+	if (type != EVM_XATTR_PORTABLE_DIGSIG) {
+		hmac_misc.ino = inode->i_ino;
+		hmac_misc.generation = inode->i_generation;
+	}
+	/* The hmac uid and gid must be encoded in the initial user
+	 * namespace (not the filesystems user namespace) as encoding
+	 * them in the filesystems user namespace allows an attack
+	 * where first they are written in an unprivileged fuse mount
+	 * of a filesystem and then the system is tricked to mount the
+	 * filesystem for real on next boot and trust it because
+	 * everything is signed.
+	 */
+	hmac_misc.uid = from_kuid(&init_user_ns, inode->i_uid);
+	hmac_misc.gid = from_kgid(&init_user_ns, inode->i_gid);
+	hmac_misc.mode = inode->i_mode;
+	crypto_shash_update(desc, (const u8 *)&hmac_misc, sizeof(hmac_misc));
+	if ((evm_hmac_attrs & EVM_ATTR_FSUUID) &&
+	    type != EVM_XATTR_PORTABLE_DIGSIG)
+		crypto_shash_update(desc, (u8 *)&inode->i_sb->s_uuid, UUID_SIZE);
+	crypto_shash_final(desc, digest);
+
+	pr_debug("hmac_misc: (%zu) [%*phN]\n", sizeof(struct h_misc),
+		 (int)sizeof(struct h_misc), &hmac_misc);
+}
+
+/*
+ * Dump large security xattr values as a continuous ascii hexadecimal string.
+ * (pr_debug is limited to 64 bytes.)
+ */
+static void dump_security_xattr_l(const char *prefix, const void *src,
+				  size_t count)
+{
+#if defined(DEBUG) || defined(CONFIG_DYNAMIC_DEBUG)
+	char *asciihex, *p;
+
+	p = asciihex = kmalloc(count * 2 + 1, GFP_KERNEL);
+	if (!asciihex)
+		return;
+
+	p = bin2hex(p, src, count);
+	*p = 0;
+	pr_debug("%s: (%zu) %.*s\n", prefix, count, (int)count * 2, asciihex);
+	kfree(asciihex);
+#endif
+}
+
+static void dump_security_xattr(const char *name, const char *value,
+				size_t value_len)
+{
+	if (value_len < 64)
+		pr_debug("%s: (%zu) [%*phN]\n", name, value_len,
+			 (int)value_len, value);
+	else
+		dump_security_xattr_l(name, value, value_len);
+}
+
+/*
+ * Calculate the HMAC value across the set of protected security xattrs.
+ *
+ * Instead of retrieving the requested xattr, for performance, calculate
+ * the hmac using the requested xattr value. Don't alloc/free memory for
+ * each xattr, but attempt to re-use the previously allocated memory.
+ */
+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,
+				 struct evm_iint_cache *iint)
+{
+	struct inode *inode = d_inode(d_real(dentry, D_REAL_METADATA));
+	struct xattr_list *xattr;
+	struct shash_desc *desc;
+	size_t xattr_size = 0;
+	char *xattr_value = NULL;
+	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)
+		return -EOPNOTSUPP;
+
+	desc = init_desc(type, data->hdr.algo);
+	if (IS_ERR(desc))
+		return PTR_ERR(desc);
+
+	data->hdr.length = crypto_shash_digestsize(desc->tfm);
+
+	error = -ENODATA;
+	list_for_each_entry_lockless(xattr, &evm_config_xattrnames, list) {
+		bool is_ima = false;
+
+		if (strcmp(xattr->name, XATTR_NAME_IMA) == 0)
+			is_ima = true;
+
+		/*
+		 * Skip non-enabled xattrs for locally calculated
+		 * signatures/HMACs.
+		 */
+		if (type != EVM_XATTR_PORTABLE_DIGSIG && !xattr->enabled)
+			continue;
+
+		if ((req_xattr_name && req_xattr_value)
+		    && !strcmp(xattr->name, req_xattr_name)) {
+			error = 0;
+			crypto_shash_update(desc, (const u8 *)req_xattr_value,
+					     req_xattr_value_len);
+			if (is_ima)
+				ima_present = true;
+
+			dump_security_xattr(req_xattr_name,
+					    req_xattr_value,
+					    req_xattr_value_len);
+			continue;
+		}
+		size = vfs_getxattr_alloc(&nop_mnt_idmap, dentry, xattr->name,
+					  &xattr_value, xattr_size, GFP_NOFS);
+		if (size == -ENOMEM) {
+			error = -ENOMEM;
+			goto out;
+		}
+		if (size < 0)
+			continue;
+
+		user_space_size = vfs_getxattr(&nop_mnt_idmap, dentry,
+					       xattr->name, NULL, 0);
+		if (user_space_size != size)
+			pr_debug("file %s: xattr %s size mismatch (kernel: %d, user: %d)\n",
+				 dentry->d_name.name, xattr->name, size,
+				 user_space_size);
+		error = 0;
+		xattr_size = size;
+		crypto_shash_update(desc, (const u8 *)xattr_value, xattr_size);
+		if (is_ima)
+			ima_present = true;
+
+		dump_security_xattr(xattr->name, xattr_value, xattr_size);
+	}
+	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;
+out:
+	kfree(xattr_value);
+	kfree(desc);
+	return error;
+}
+
+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_iint_cache *iint)
+{
+	return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value,
+				    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, struct evm_iint_cache *iint)
+{
+	return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value,
+				     req_xattr_value_len, type, data, iint);
+}
+
+static int evm_is_immutable(struct dentry *dentry, struct inode *inode)
+{
+	const struct evm_ima_xattr_data *xattr_data = NULL;
+	struct evm_iint_cache *iint;
+	int rc = 0;
+
+	iint = evm_iint_inode(inode);
+	if (iint && (iint->flags & EVM_IMMUTABLE_DIGSIG))
+		return 1;
+
+	/* Do this the hard way */
+	rc = vfs_getxattr_alloc(&nop_mnt_idmap, dentry, XATTR_NAME_EVM,
+				(char **)&xattr_data, 0, GFP_NOFS);
+	if (rc <= 0) {
+		if (rc == -ENODATA)
+			rc = 0;
+		goto out;
+	}
+	if (xattr_data->type == EVM_XATTR_PORTABLE_DIGSIG)
+		rc = 1;
+	else
+		rc = 0;
+
+out:
+	kfree(xattr_data);
+	return rc;
+}
+
+
+/*
+ * Calculate the hmac and update security.evm xattr
+ *
+ * Expects to be called with i_mutex locked.
+ */
+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;
+
+	/*
+	 * Don't permit any transformation of the EVM xattr if the signature
+	 * is of an immutable type
+	 */
+	rc = evm_is_immutable(dentry, inode);
+	if (rc < 0)
+		return rc;
+	if (rc)
+		return -EPERM;
+
+	data.hdr.algo = HASH_ALGO_SHA1;
+	rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
+			   xattr_value_len, &data, iint);
+	if (rc == 0) {
+		data.hdr.xattr.sha1.type = EVM_XATTR_HMAC;
+		rc = __vfs_setxattr_noperm(&nop_mnt_idmap, dentry,
+					   XATTR_NAME_EVM,
+					   &data.hdr.xattr.data[1],
+					   SHA1_DIGEST_SIZE + 1, 0);
+	} else if (rc == -ENODATA && (inode->i_opflags & IOP_XATTR)) {
+		rc = __vfs_removexattr(&nop_mnt_idmap, dentry, XATTR_NAME_EVM);
+	}
+	return rc;
+}
+
+int evm_init_hmac(struct inode *inode, const struct xattr *xattrs,
+		  char *hmac_val)
+{
+	struct shash_desc *desc;
+	const struct xattr *xattr;
+	struct xattr_list *xattr_entry;
+
+	desc = init_desc(EVM_XATTR_HMAC, HASH_ALGO_SHA1);
+	if (IS_ERR(desc)) {
+		pr_info("init_desc failed\n");
+		return PTR_ERR(desc);
+	}
+
+	list_for_each_entry_lockless(xattr_entry, &evm_config_xattrnames,
+				     list) {
+		for (xattr = xattrs; xattr->name; xattr++) {
+			if (strcmp(xattr_entry->name +
+				   XATTR_SECURITY_PREFIX_LEN, xattr->name) != 0)
+				continue;
+
+			crypto_shash_update(desc, xattr->value,
+					    xattr->value_len);
+		}
+	}
+
+	hmac_add_misc(desc, inode, EVM_XATTR_HMAC, hmac_val);
+	kfree(desc);
+	return 0;
+}
+
+/*
+ * Get the key from the TPM for the SHA1-HMAC
+ */
+int evm_init_key(void)
+{
+	struct key *evm_key;
+	struct encrypted_key_payload *ekp;
+	int rc;
+
+	evm_key = request_key(&key_type_encrypted, EVMKEY, NULL);
+	if (IS_ERR(evm_key))
+		return -ENOENT;
+
+	down_read(&evm_key->sem);
+	ekp = evm_key->payload.data[0];
+
+	rc = evm_set_key(ekp->decrypted_data, ekp->decrypted_datalen);
+
+	/* burn the original key contents */
+	memset(ekp->decrypted_data, 0, ekp->decrypted_datalen);
+	up_read(&evm_key->sem);
+	key_put(evm_key);
+	return rc;
+}

linux-7.2.3/security/integrity/evm/evm_posix_acl.c

@@ -0,0 +1,23 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2011 IBM Corporation
+ *
+ * Author:
+ * Mimi Zohar <zohar@us.ibm.com>
+ */
+
+#include <linux/xattr.h>
+#include <linux/evm.h>
+
+int posix_xattr_acl(const char *xattr)
+{
+	int xattr_len = strlen(xattr);
+
+	if ((strlen(XATTR_NAME_POSIX_ACL_ACCESS) == xattr_len)
+	     && (strncmp(XATTR_NAME_POSIX_ACL_ACCESS, xattr, xattr_len) == 0))
+		return 1;
+	if ((strlen(XATTR_NAME_POSIX_ACL_DEFAULT) == xattr_len)
+	     && (strncmp(XATTR_NAME_POSIX_ACL_DEFAULT, xattr, xattr_len) == 0))
+		return 1;
+	return 0;
+}

linux-7.2.3/security/integrity/evm/evm_secfs.c

@@ -0,0 +1,346 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2010 IBM Corporation
+ *
+ * Authors:
+ * Mimi Zohar <zohar@us.ibm.com>
+ *
+ * File: evm_secfs.c
+ *	- Used to signal when key is on keyring
+ *	- Get the key and enable EVM
+ */
+
+#include <linux/audit.h>
+#include <linux/uaccess.h>
+#include <linux/init.h>
+#include <linux/mutex.h>
+#include "evm.h"
+
+static struct dentry *evm_dir;
+static struct dentry *evm_symlink;
+
+#ifdef CONFIG_EVM_ADD_XATTRS
+static struct dentry *evm_xattrs;
+static DEFINE_MUTEX(xattr_list_mutex);
+static int evm_xattrs_locked;
+#endif
+
+/**
+ * evm_read_key - read() for <securityfs>/evm
+ *
+ * @filp: file pointer, not actually used
+ * @buf: where to put the result
+ * @count: maximum to send along
+ * @ppos: where to start
+ *
+ * Returns number of bytes read or error code, as appropriate
+ */
+static ssize_t evm_read_key(struct file *filp, char __user *buf,
+			    size_t count, loff_t *ppos)
+{
+	char temp[80];
+	ssize_t rc;
+
+	if (*ppos != 0)
+		return 0;
+
+	sprintf(temp, "%d", (evm_initialized & ~EVM_SETUP_COMPLETE));
+	rc = simple_read_from_buffer(buf, count, ppos, temp, strlen(temp));
+
+	return rc;
+}
+
+/**
+ * evm_write_key - write() for <securityfs>/evm
+ * @file: file pointer, not actually used
+ * @buf: where to get the data from
+ * @count: bytes sent
+ * @ppos: where to start
+ *
+ * Used to signal that key is on the kernel key ring.
+ * - get the integrity hmac key from the kernel key ring
+ * - create list of hmac protected extended attributes
+ * Returns number of bytes written or error code, as appropriate
+ */
+static ssize_t evm_write_key(struct file *file, const char __user *buf,
+			     size_t count, loff_t *ppos)
+{
+	unsigned int i;
+	int ret;
+
+	if (!capable(CAP_SYS_ADMIN) || (evm_initialized & EVM_SETUP_COMPLETE))
+		return -EPERM;
+
+	ret = kstrtouint_from_user(buf, count, 0, &i);
+
+	if (ret)
+		return ret;
+
+	/* Reject invalid values */
+	if (!i || (i & ~EVM_INIT_MASK) != 0)
+		return -EINVAL;
+
+	/*
+	 * Don't allow a request to enable metadata writes if
+	 * an HMAC key is loaded.
+	 */
+	if ((i & EVM_ALLOW_METADATA_WRITES) &&
+	    (evm_initialized & EVM_INIT_HMAC) != 0)
+		return -EPERM;
+
+	if (i & EVM_INIT_HMAC) {
+		ret = evm_init_key();
+		if (ret != 0)
+			return ret;
+		/* Forbid further writes after the symmetric key is loaded */
+		i |= EVM_SETUP_COMPLETE;
+	}
+
+	evm_initialized |= i;
+
+	/* Don't allow protected metadata modification if a symmetric key
+	 * is loaded
+	 */
+	if (evm_initialized & EVM_INIT_HMAC)
+		evm_initialized &= ~(EVM_ALLOW_METADATA_WRITES);
+
+	return count;
+}
+
+static const struct file_operations evm_key_ops = {
+	.read		= evm_read_key,
+	.write		= evm_write_key,
+};
+
+#ifdef CONFIG_EVM_ADD_XATTRS
+/**
+ * evm_read_xattrs - read() for <securityfs>/evm_xattrs
+ *
+ * @filp: file pointer, not actually used
+ * @buf: where to put the result
+ * @count: maximum to send along
+ * @ppos: where to start
+ *
+ * Returns number of bytes read or error code, as appropriate
+ */
+static ssize_t evm_read_xattrs(struct file *filp, char __user *buf,
+			       size_t count, loff_t *ppos)
+{
+	char *temp;
+	size_t offset = 0, size = 0;
+	ssize_t rc;
+	struct xattr_list *xattr;
+
+	if (*ppos != 0)
+		return 0;
+
+	rc = mutex_lock_interruptible(&xattr_list_mutex);
+	if (rc)
+		return -ERESTARTSYS;
+
+	list_for_each_entry(xattr, &evm_config_xattrnames, list) {
+		if (!xattr->enabled)
+			continue;
+
+		size += strlen(xattr->name) + 1;
+	}
+
+	temp = kmalloc(size + 1, GFP_KERNEL);
+	if (!temp) {
+		mutex_unlock(&xattr_list_mutex);
+		return -ENOMEM;
+	}
+
+	temp[size] = '\0';
+
+	/*
+	 * No truncation possible: size is computed over the same enabled
+	 * xattrs under xattr_list_mutex, so offset never exceeds size.
+	 */
+	list_for_each_entry(xattr, &evm_config_xattrnames, list) {
+		if (!xattr->enabled)
+			continue;
+
+		offset += snprintf(temp + offset, size + 1 - offset, "%s\n",
+				   xattr->name);
+	}
+
+	mutex_unlock(&xattr_list_mutex);
+	rc = simple_read_from_buffer(buf, count, ppos, temp, offset);
+
+	kfree(temp);
+
+	return rc;
+}
+
+/**
+ * evm_write_xattrs - write() for <securityfs>/evm_xattrs
+ * @file: file pointer, not actually used
+ * @buf: where to get the data from
+ * @count: bytes sent
+ * @ppos: where to start
+ *
+ * Returns number of bytes written or error code, as appropriate
+ */
+static ssize_t evm_write_xattrs(struct file *file, const char __user *buf,
+				size_t count, loff_t *ppos)
+{
+	int len, err;
+	struct xattr_list *xattr, *tmp;
+	struct audit_buffer *ab;
+	struct iattr newattrs;
+	struct inode *inode;
+
+	if (!capable(CAP_SYS_ADMIN) || evm_xattrs_locked)
+		return -EPERM;
+
+	if (*ppos != 0)
+		return -EINVAL;
+
+	if (count > XATTR_NAME_MAX)
+		return -E2BIG;
+
+	ab = audit_log_start(audit_context(), GFP_KERNEL,
+			     AUDIT_INTEGRITY_EVM_XATTR);
+	if (!ab && IS_ENABLED(CONFIG_AUDIT))
+		return -ENOMEM;
+
+	xattr = kmalloc_obj(struct xattr_list);
+	if (!xattr) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	xattr->enabled = true;
+	xattr->name = memdup_user_nul(buf, count);
+	if (IS_ERR(xattr->name)) {
+		err = PTR_ERR(xattr->name);
+		xattr->name = NULL;
+		goto out;
+	}
+
+	/* Remove any trailing newline */
+	len = strlen(xattr->name);
+	if (len && xattr->name[len-1] == '\n')
+		xattr->name[len-1] = '\0';
+
+	audit_log_format(ab, "xattr=");
+	audit_log_untrustedstring(ab, xattr->name);
+
+	if (strcmp(xattr->name, ".") == 0) {
+		evm_xattrs_locked = 1;
+		newattrs.ia_mode = S_IFREG | 0440;
+		newattrs.ia_valid = ATTR_MODE;
+		inode = evm_xattrs->d_inode;
+		inode_lock(inode);
+		err = simple_setattr(&nop_mnt_idmap, evm_xattrs, &newattrs);
+		inode_unlock(inode);
+		if (!err)
+			err = count;
+		goto out;
+	}
+
+	if (strncmp(xattr->name, XATTR_SECURITY_PREFIX,
+		    XATTR_SECURITY_PREFIX_LEN) != 0) {
+		err = -EINVAL;
+		goto out;
+	}
+
+	/*
+	 * xattr_list_mutex guards against races in evm_read_xattrs().
+	 * Entries are only added to the evm_config_xattrnames list
+	 * and never deleted. Therefore, the list is traversed
+	 * using list_for_each_entry_lockless() without holding
+	 * the mutex in evm_calc_hmac_or_hash(), evm_find_protected_xattrs()
+	 * and evm_protected_xattr().
+	 */
+	mutex_lock(&xattr_list_mutex);
+	list_for_each_entry(tmp, &evm_config_xattrnames, list) {
+		if (strcmp(xattr->name, tmp->name) == 0) {
+			err = -EEXIST;
+			if (!tmp->enabled) {
+				tmp->enabled = true;
+				err = count;
+			}
+			mutex_unlock(&xattr_list_mutex);
+			goto out;
+		}
+	}
+	list_add_tail_rcu(&xattr->list, &evm_config_xattrnames);
+	mutex_unlock(&xattr_list_mutex);
+
+	audit_log_format(ab, " res=0");
+	audit_log_end(ab);
+	return count;
+out:
+	audit_log_format(ab, " res=%d", (err < 0) ? err : 0);
+	audit_log_end(ab);
+	if (xattr) {
+		kfree(xattr->name);
+		kfree(xattr);
+	}
+	return err;
+}
+
+static const struct file_operations evm_xattr_ops = {
+	.read		= evm_read_xattrs,
+	.write		= evm_write_xattrs,
+};
+
+static int evm_init_xattrs(void)
+{
+	evm_xattrs = securityfs_create_file("evm_xattrs", 0660, evm_dir, NULL,
+					    &evm_xattr_ops);
+	if (IS_ERR(evm_xattrs))
+		return -EFAULT;
+
+	return 0;
+}
+#else
+static int evm_init_xattrs(void)
+{
+	return 0;
+}
+#endif
+
+int __init evm_init_secfs(void)
+{
+	int error = 0;
+	struct dentry *dentry;
+
+	error = integrity_fs_init();
+	if (error < 0)
+		return -EFAULT;
+
+	evm_dir = securityfs_create_dir("evm", integrity_dir);
+	if (IS_ERR(evm_dir)) {
+		error = -EFAULT;
+		goto out;
+	}
+
+	dentry = securityfs_create_file("evm", 0660,
+				      evm_dir, NULL, &evm_key_ops);
+	if (IS_ERR(dentry)) {
+		error = -EFAULT;
+		goto out;
+	}
+
+	evm_symlink = securityfs_create_symlink("evm", NULL,
+						"integrity/evm/evm", NULL);
+	if (IS_ERR(evm_symlink)) {
+		error = -EFAULT;
+		goto out;
+	}
+
+	if (evm_init_xattrs() != 0) {
+		error = -EFAULT;
+		goto out;
+	}
+
+	return 0;
+out:
+	securityfs_remove(evm_symlink);
+	securityfs_remove(evm_dir);
+	integrity_fs_fini();
+	return error;
+}