--- /dev/null
+/*
+ * Copyright (C) 2005-2010 IBM Corporation
+ *
+ * Authors:
+ * Mimi Zohar <zohar@us.ibm.com>
+ * Kylene Hall <kjhall@us.ibm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 2 of the License.
+ *
+ * File: evm_crypto.c
+ * Using root's kernel master key (kmk), calculate the HMAC
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/crypto.h>
+#include <linux/xattr.h>
+#include <keys/encrypted-type.h>
+#include <crypto/hash.h>
+#include "evm.h"
+
+#define EVMKEY "evm-key"
+#define MAX_KEY_SIZE 128
+static unsigned char evmkey[MAX_KEY_SIZE];
+static int evmkey_len = MAX_KEY_SIZE;
+
+struct crypto_shash *hmac_tfm;
+struct crypto_shash *hash_tfm;
+
+static DEFINE_MUTEX(mutex);
+
+static struct shash_desc *init_desc(char type)
+{
+ long rc;
+ char *algo;
+ struct crypto_shash **tfm;
+ struct shash_desc *desc;
+
+ if (type == EVM_XATTR_HMAC) {
+ tfm = &hmac_tfm;
+ algo = evm_hmac;
+ } else {
+ tfm = &hash_tfm;
+ algo = evm_hash;
+ }
+
+ if (*tfm == NULL) {
+ mutex_lock(&mutex);
+ if (*tfm)
+ goto out;
+ *tfm = crypto_alloc_shash(algo, 0, CRYPTO_ALG_ASYNC);
+ if (IS_ERR(*tfm)) {
+ rc = PTR_ERR(*tfm);
+ pr_err("Can not allocate %s (reason: %ld)\n", algo, rc);
+ *tfm = NULL;
+ mutex_unlock(&mutex);
+ return ERR_PTR(rc);
+ }
+ if (type == EVM_XATTR_HMAC) {
+ rc = crypto_shash_setkey(*tfm, evmkey, evmkey_len);
+ if (rc) {
+ crypto_free_shash(*tfm);
+ *tfm = NULL;
+ mutex_unlock(&mutex);
+ return ERR_PTR(rc);
+ }
+ }
+out:
+ mutex_unlock(&mutex);
+ }
+
+ desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(*tfm),
+ GFP_KERNEL);
+ if (!desc)
+ return ERR_PTR(-ENOMEM);
+
+ desc->tfm = *tfm;
+ desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
+
+ 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 *digest)
+{
+ struct h_misc {
+ unsigned long ino;
+ __u32 generation;
+ uid_t uid;
+ gid_t gid;
+ umode_t mode;
+ } hmac_misc;
+
+ memset(&hmac_misc, 0, sizeof(hmac_misc));
+ hmac_misc.ino = inode->i_ino;
+ hmac_misc.generation = inode->i_generation;
+ 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)
+ crypto_shash_update(desc, inode->i_sb->s_uuid,
+ sizeof(inode->i_sb->s_uuid));
+ crypto_shash_final(desc, digest);
+}
+
+/*
+ * 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,
+ char type, char *digest)
+{
+ struct inode *inode = d_backing_inode(dentry);
+ struct shash_desc *desc;
+ char **xattrname;
+ size_t xattr_size = 0;
+ char *xattr_value = NULL;
+ int error;
+ int size;
+
+ if (!inode->i_op->getxattr)
+ return -EOPNOTSUPP;
+ desc = init_desc(type);
+ if (IS_ERR(desc))
+ return PTR_ERR(desc);
+
+ error = -ENODATA;
+ for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
+ if ((req_xattr_name && req_xattr_value)
+ && !strcmp(*xattrname, req_xattr_name)) {
+ error = 0;
+ crypto_shash_update(desc, (const u8 *)req_xattr_value,
+ req_xattr_value_len);
+ continue;
+ }
+ size = vfs_getxattr_alloc(dentry, *xattrname,
+ &xattr_value, xattr_size, GFP_NOFS);
+ if (size == -ENOMEM) {
+ error = -ENOMEM;
+ goto out;
+ }
+ if (size < 0)
+ continue;
+
+ error = 0;
+ xattr_size = size;
+ crypto_shash_update(desc, (const u8 *)xattr_value, xattr_size);
+ }
+ hmac_add_misc(desc, inode, digest);
+
+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,
+ char *digest)
+{
+ return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value,
+ req_xattr_value_len, EVM_XATTR_HMAC, digest);
+}
+
+int evm_calc_hash(struct dentry *dentry, const char *req_xattr_name,
+ const char *req_xattr_value, size_t req_xattr_value_len,
+ char *digest)
+{
+ return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value,
+ req_xattr_value_len, IMA_XATTR_DIGEST, digest);
+}
+
+/*
+ * 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_ima_xattr_data xattr_data;
+ int rc = 0;
+
+ rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
+ xattr_value_len, xattr_data.digest);
+ if (rc == 0) {
+ xattr_data.type = EVM_XATTR_HMAC;
+ rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_EVM,
+ &xattr_data,
+ sizeof(xattr_data), 0);
+ } else if (rc == -ENODATA && inode->i_op->removexattr) {
+ rc = inode->i_op->removexattr(dentry, XATTR_NAME_EVM);
+ }
+ return rc;
+}
+
+int evm_init_hmac(struct inode *inode, const struct xattr *lsm_xattr,
+ char *hmac_val)
+{
+ struct shash_desc *desc;
+
+ desc = init_desc(EVM_XATTR_HMAC);
+ if (IS_ERR(desc)) {
+ pr_info("init_desc failed\n");
+ return PTR_ERR(desc);
+ }
+
+ crypto_shash_update(desc, lsm_xattr->value, lsm_xattr->value_len);
+ hmac_add_misc(desc, inode, 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 = 0;
+
+ 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;
+ if (ekp->decrypted_datalen > MAX_KEY_SIZE) {
+ rc = -EINVAL;
+ goto out;
+ }
+ memcpy(evmkey, ekp->decrypted_data, ekp->decrypted_datalen);
+out:
+ /* burn the original key contents */
+ memset(ekp->decrypted_data, 0, ekp->decrypted_datalen);
+ up_read(&evm_key->sem);
+ key_put(evm_key);
+ return rc;
+}
Code Review / kvmfornfv.git / blobdiff