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-rw-r--r--security/integrity/evm/evm_crypto.c183
1 files changed, 183 insertions, 0 deletions
diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
new file mode 100644
index 00000000000..d49bb002f3d
--- /dev/null
+++ b/security/integrity/evm/evm_crypto.c
@@ -0,0 +1,183 @@
+/*
+ * 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
+ */
+
+#include <linux/module.h>
+#include <linux/crypto.h>
+#include <linux/xattr.h>
+#include <linux/scatterlist.h>
+#include <keys/encrypted-type.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;
+
+static int init_desc(struct hash_desc *desc)
+{
+ int rc;
+
+ desc->tfm = crypto_alloc_hash(evm_hmac, 0, CRYPTO_ALG_ASYNC);
+ if (IS_ERR(desc->tfm)) {
+ pr_info("Can not allocate %s (reason: %ld)\n",
+ evm_hmac, PTR_ERR(desc->tfm));
+ rc = PTR_ERR(desc->tfm);
+ return rc;
+ }
+ desc->flags = 0;
+ rc = crypto_hash_setkey(desc->tfm, evmkey, evmkey_len);
+ if (rc)
+ goto out;
+ rc = crypto_hash_init(desc);
+out:
+ if (rc)
+ crypto_free_hash(desc->tfm);
+ return rc;
+}
+
+/* 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 hash_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;
+ struct scatterlist sg[1];
+
+ memset(&hmac_misc, 0, sizeof hmac_misc);
+ hmac_misc.ino = inode->i_ino;
+ hmac_misc.generation = inode->i_generation;
+ hmac_misc.uid = inode->i_uid;
+ hmac_misc.gid = inode->i_gid;
+ hmac_misc.mode = inode->i_mode;
+ sg_init_one(sg, &hmac_misc, sizeof hmac_misc);
+ crypto_hash_update(desc, sg, sizeof hmac_misc);
+ crypto_hash_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.
+ */
+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)
+{
+ struct inode *inode = dentry->d_inode;
+ struct hash_desc desc;
+ struct scatterlist sg[1];
+ char **xattrname;
+ size_t xattr_size = 0;
+ char *xattr_value = NULL;
+ int error;
+ int size;
+
+ if (!inode->i_op || !inode->i_op->getxattr)
+ return -EOPNOTSUPP;
+ error = init_desc(&desc);
+ if (error)
+ return error;
+
+ error = -ENODATA;
+ for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
+ if ((req_xattr_name && req_xattr_value)
+ && !strcmp(*xattrname, req_xattr_name)) {
+ error = 0;
+ sg_init_one(sg, req_xattr_value, req_xattr_value_len);
+ crypto_hash_update(&desc, sg, 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;
+ sg_init_one(sg, xattr_value, xattr_size);
+ crypto_hash_update(&desc, sg, xattr_size);
+ }
+ hmac_add_misc(&desc, inode, digest);
+ kfree(xattr_value);
+out:
+ crypto_free_hash(desc.tfm);
+ return error;
+}
+
+/*
+ * 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 = dentry->d_inode;
+ u8 hmac[SHA1_DIGEST_SIZE];
+ int rc = 0;
+
+ rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
+ xattr_value_len, hmac);
+ if (rc == 0)
+ rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_EVM,
+ hmac, SHA1_DIGEST_SIZE, 0);
+ else if (rc == -ENODATA)
+ rc = inode->i_op->removexattr(dentry, XATTR_NAME_EVM);
+ return rc;
+}
+
+/*
+ * 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;
+}