1 files changed, 216 insertions, 0 deletions

diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
new file mode 100644
index 000000000000..5dd5b140242c
--- /dev/null
+++ b/security/integrity/evm/evm_crypto.c
@@ -0,0 +1,216 @@
+/*
+ * 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 <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;
+
+static struct shash_desc *init_desc(void)
+{
+        int rc;
+        struct shash_desc *desc;
+
+        if (hmac_tfm == NULL) {
+                hmac_tfm = crypto_alloc_shash(evm_hmac, 0, CRYPTO_ALG_ASYNC);
+                if (IS_ERR(hmac_tfm)) {
+                        pr_err("Can not allocate %s (reason: %ld)\n",
+                               evm_hmac, PTR_ERR(hmac_tfm));
+                        rc = PTR_ERR(hmac_tfm);
+                        hmac_tfm = NULL;
+                        return ERR_PTR(rc);
+                }
+        }
+
+        desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(hmac_tfm),
+                        GFP_KERNEL);
+        if (!desc)
+                return ERR_PTR(-ENOMEM);
+
+        desc->tfm = hmac_tfm;
+        desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
+
+        rc = crypto_shash_setkey(hmac_tfm, evmkey, evmkey_len);
+        if (rc)
+                goto out;
+        rc = crypto_shash_init(desc);
+out:
+        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 = inode->i_uid;
+        hmac_misc.gid = inode->i_gid;
+        hmac_misc.mode = inode->i_mode;
+        crypto_shash_update(desc, (const u8 *)&hmac_misc, sizeof hmac_misc);
+        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.
+ */
+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 shash_desc *desc;
+        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;
+        desc = init_desc();
+        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;
+}
+
+/*
+ * 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;
+        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)
+                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();
+        if (IS_ERR(desc)) {
+                printk(KERN_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;
+}