1 files changed, 334 insertions, 0 deletions
diff --git a/security/integrity/evm/evm_secfs.c b/security/integrity/evm/evm_secfs.c
new file mode 100644
index 000000000..8a9db7dfc
--- /dev/null
+++ b/security/integrity/evm/evm_secfs.c
@@ -0,0 +1,334 @@
+// 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_init_tpm;
+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;
+	int offset = 0;
+	ssize_t rc, size = 0;
+	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;
+	}
+
+	list_for_each_entry(xattr, &evm_config_xattrnames, list) {
+		if (!xattr->enabled)
+			continue;
+
+		sprintf(temp + offset, "%s\n", xattr->name);
+		offset += strlen(xattr->name) + 1;
+	}
+
+	mutex_unlock(&xattr_list_mutex);
+	rc = simple_read_from_buffer(buf, count, ppos, temp, strlen(temp));
+
+	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(sizeof(struct xattr_list), GFP_KERNEL);
+	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(&init_user_ns, 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 (!evm_xattrs || 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;
+
+	evm_dir = securityfs_create_dir("evm", integrity_dir);
+	if (!evm_dir || IS_ERR(evm_dir))
+		return -EFAULT;
+
+	evm_init_tpm = securityfs_create_file("evm", 0660,
+					      evm_dir, NULL, &evm_key_ops);
+	if (!evm_init_tpm || IS_ERR(evm_init_tpm)) {
+		error = -EFAULT;
+		goto out;
+	}
+
+	evm_symlink = securityfs_create_symlink("evm", NULL,
+						"integrity/evm/evm", NULL);
+	if (!evm_symlink || 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_init_tpm);
+	securityfs_remove(evm_dir);
+	return error;
+}