1 files changed, 284 insertions, 0 deletions
diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
new file mode 100644
index 00000000000..a8fa45fef8f
--- /dev/null
+++ b/security/integrity/evm/evm_main.c
@@ -0,0 +1,284 @@
+/*
+ * Copyright (C) 2005-2010 IBM Corporation
+ *
+ * Author:
+ * 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_main.c
+ *	implements evm_inode_setxattr, evm_inode_post_setxattr,
+ *	evm_inode_removexattr, and evm_verifyxattr
+ */
+
+#include <linux/module.h>
+#include <linux/crypto.h>
+#include <linux/xattr.h>
+#include <linux/integrity.h>
+#include "evm.h"
+
+int evm_initialized;
+
+char *evm_hmac = "hmac(sha1)";
+
+char *evm_config_xattrnames[] = {
+#ifdef CONFIG_SECURITY_SELINUX
+	XATTR_NAME_SELINUX,
+#endif
+#ifdef CONFIG_SECURITY_SMACK
+	XATTR_NAME_SMACK,
+#endif
+	XATTR_NAME_CAPS,
+	NULL
+};
+
+/*
+ * 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.)
+ *
+ * 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 integrity_iint_cache *iint)
+{
+	char hmac_val[SHA1_DIGEST_SIZE];
+	int rc;
+
+	if (iint->hmac_status != INTEGRITY_UNKNOWN)
+		return iint->hmac_status;
+
+	memset(hmac_val, 0, sizeof hmac_val);
+	rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
+			   xattr_value_len, hmac_val);
+	if (rc < 0)
+		return INTEGRITY_UNKNOWN;
+
+	rc = vfs_xattr_cmp(dentry, XATTR_NAME_EVM, hmac_val, sizeof hmac_val,
+			   GFP_NOFS);
+	if (rc < 0)
+		goto err_out;
+	iint->hmac_status = INTEGRITY_PASS;
+	return iint->hmac_status;
+
+err_out:
+	switch (rc) {
+	case -ENODATA:		/* file not labelled */
+		iint->hmac_status = INTEGRITY_NOLABEL;
+		break;
+	case -EINVAL:
+		iint->hmac_status = INTEGRITY_FAIL;
+		break;
+	default:
+		iint->hmac_status = INTEGRITY_UNKNOWN;
+	}
+	return iint->hmac_status;
+}
+
+static int evm_protected_xattr(const char *req_xattr_name)
+{
+	char **xattrname;
+	int namelen;
+	int found = 0;
+
+	namelen = strlen(req_xattr_name);
+	for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
+		if ((strlen(*xattrname) == namelen)
+		    && (strncmp(req_xattr_name, *xattrname, namelen) == 0)) {
+			found = 1;
+			break;
+		}
+	}
+	return found;
+}
+
+/**
+ * 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)
+{
+	struct inode *inode = dentry->d_inode;
+	struct integrity_iint_cache *iint;
+	enum integrity_status status;
+
+	if (!evm_initialized || !evm_protected_xattr(xattr_name))
+		return INTEGRITY_UNKNOWN;
+
+	iint = integrity_iint_find(inode);
+	if (!iint)
+		return INTEGRITY_UNKNOWN;
+	status = evm_verify_hmac(dentry, xattr_name, xattr_value,
+				 xattr_value_len, iint);
+	return status;
+}
+EXPORT_SYMBOL_GPL(evm_verifyxattr);
+
+/*
+ * evm_protect_xattr - protect the EVM extended attribute
+ *
+ * Prevent security.evm from being modified or removed.
+ */
+static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name,
+			     const void *xattr_value, size_t xattr_value_len)
+{
+	if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
+		if (!capable(CAP_SYS_ADMIN))
+			return -EPERM;
+	}
+	return 0;
+}
+
+/**
+ * evm_inode_setxattr - protect the EVM extended attribute
+ * @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
+ *
+ * Prevent 'security.evm' from being modified
+ */
+int evm_inode_setxattr(struct dentry *dentry, const char *xattr_name,
+		       const void *xattr_value, size_t xattr_value_len)
+{
+	return evm_protect_xattr(dentry, xattr_name, xattr_value,
+				 xattr_value_len);
+}
+
+/**
+ * evm_inode_removexattr - protect the EVM extended attribute
+ * @dentry: pointer to the affected dentry
+ * @xattr_name: pointer to the affected extended attribute name
+ *
+ * Prevent 'security.evm' from being removed.
+ */
+int evm_inode_removexattr(struct dentry *dentry, const char *xattr_name)
+{
+	return evm_protect_xattr(dentry, xattr_name, NULL, 0);
+}
+
+/**
+ * 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
+ *
+ * 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.
+ */
+void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name,
+			     const void *xattr_value, size_t xattr_value_len)
+{
+	if (!evm_initialized || !evm_protected_xattr(xattr_name))
+		return;
+
+	evm_update_evmxattr(dentry, xattr_name, xattr_value, xattr_value_len);
+	return;
+}
+
+/**
+ * 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.
+ */
+void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name)
+{
+	struct inode *inode = dentry->d_inode;
+
+	if (!evm_initialized || !evm_protected_xattr(xattr_name))
+		return;
+
+	mutex_lock(&inode->i_mutex);
+	evm_update_evmxattr(dentry, xattr_name, NULL, 0);
+	mutex_unlock(&inode->i_mutex);
+	return;
+}
+
+/**
+ * evm_inode_post_setattr - update 'security.evm' after modifying metadata
+ * @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.
+ */
+void evm_inode_post_setattr(struct dentry *dentry, int ia_valid)
+{
+	if (!evm_initialized)
+		return;
+
+	if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
+		evm_update_evmxattr(dentry, NULL, NULL, 0);
+	return;
+}
+
+static struct crypto_hash *tfm_hmac;	/* preload crypto alg */
+static int __init init_evm(void)
+{
+	int error;
+
+	tfm_hmac = crypto_alloc_hash(evm_hmac, 0, CRYPTO_ALG_ASYNC);
+	error = evm_init_secfs();
+	if (error < 0) {
+		printk(KERN_INFO "EVM: Error registering secfs\n");
+		goto err;
+	}
+err:
+	return error;
+}
+
+static void __exit cleanup_evm(void)
+{
+	evm_cleanup_secfs();
+	crypto_free_hash(tfm_hmac);
+}
+
+/*
+ * evm_display_config - list the EVM protected security extended attributes
+ */
+static int __init evm_display_config(void)
+{
+	char **xattrname;
+
+	for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++)
+		printk(KERN_INFO "EVM: %s\n", *xattrname);
+	return 0;
+}
+
+pure_initcall(evm_display_config);
+late_initcall(init_evm);
+
+MODULE_DESCRIPTION("Extended Verification Module");
+MODULE_LICENSE("GPL");