security/integrity/ima/ima_template.c

/*
 * Copyright (C) 2013 Politecnico di Torino, Italy
 *                    TORSEC group -- http://security.polito.it
 *
 * Author: Roberto Sassu <roberto.sassu@polito.it>
 *
 * 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: ima_template.c
 *      Helpers to manage template descriptors.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include "ima.h"
#include "ima_template_lib.h"

static struct ima_template_desc defined_templates[] = {
	{.name = IMA_TEMPLATE_IMA_NAME, .fmt = IMA_TEMPLATE_IMA_FMT},
	{.name = "ima-ng", .fmt = "d-ng|n-ng"},
	{.name = "ima-sig", .fmt = "d-ng|n-ng|sig"},
	{.name = "", .fmt = ""},	/* placeholder for a custom format */
};

static struct ima_template_field supported_fields[] = {
	{.field_id = "d", .field_init = ima_eventdigest_init,
	 .field_show = ima_show_template_digest},
	{.field_id = "n", .field_init = ima_eventname_init,
	 .field_show = ima_show_template_string},
	{.field_id = "d-ng", .field_init = ima_eventdigest_ng_init,
	 .field_show = ima_show_template_digest_ng},
	{.field_id = "n-ng", .field_init = ima_eventname_ng_init,
	 .field_show = ima_show_template_string},
	{.field_id = "sig", .field_init = ima_eventsig_init,
	 .field_show = ima_show_template_sig},
};

static struct ima_template_desc *ima_template;
static struct ima_template_desc *lookup_template_desc(const char *name);
static int template_desc_init_fields(const char *template_fmt,
				     struct ima_template_field ***fields,
				     int *num_fields);

static int __init ima_template_setup(char *str)
{
	struct ima_template_desc *template_desc;
	int template_len = strlen(str);

	if (ima_template)
		return 1;

	/*
	 * Verify that a template with the supplied name exists.
	 * If not, use CONFIG_IMA_DEFAULT_TEMPLATE.
	 */
	template_desc = lookup_template_desc(str);
	if (!template_desc) {
		pr_err("template %s not found, using %s\n",
		       str, CONFIG_IMA_DEFAULT_TEMPLATE);
		return 1;
	}

	/*
	 * Verify whether the current hash algorithm is supported
	 * by the 'ima' template.
	 */
	if (template_len == 3 && strcmp(str, IMA_TEMPLATE_IMA_NAME) == 0 &&
	    ima_hash_algo != HASH_ALGO_SHA1 && ima_hash_algo != HASH_ALGO_MD5) {
		pr_err("template does not support hash alg\n");
		return 1;
	}

	ima_template = template_desc;
	return 1;
}
__setup("ima_template=", ima_template_setup);

static int __init ima_template_fmt_setup(char *str)
{
	int num_templates = ARRAY_SIZE(defined_templates);

	if (ima_template)
		return 1;

	if (template_desc_init_fields(str, NULL, NULL) < 0) {
		pr_err("format string '%s' not valid, using template %s\n",
		       str, CONFIG_IMA_DEFAULT_TEMPLATE);
		return 1;
	}

	defined_templates[num_templates - 1].fmt = str;
	ima_template = defined_templates + num_templates - 1;
	return 1;
}
__setup("ima_template_fmt=", ima_template_fmt_setup);

static struct ima_template_desc *lookup_template_desc(const char *name)
{
	int i;

	for (i = 0; i < ARRAY_SIZE(defined_templates); i++) {
		if (strcmp(defined_templates[i].name, name) == 0)
			return defined_templates + i;
	}

	return NULL;
}

static struct ima_template_field *lookup_template_field(const char *field_id)
{
	int i;

	for (i = 0; i < ARRAY_SIZE(supported_fields); i++)
		if (strncmp(supported_fields[i].field_id, field_id,
			    IMA_TEMPLATE_FIELD_ID_MAX_LEN) == 0)
			return &supported_fields[i];
	return NULL;
}

static int template_fmt_size(const char *template_fmt)
{
	char c;
	int template_fmt_len = strlen(template_fmt);
	int i = 0, j = 0;

	while (i < template_fmt_len) {
		c = template_fmt[i];
		if (c == '|')
			j++;
		i++;
	}

	return j + 1;
}

static int template_desc_init_fields(const char *template_fmt,
				     struct ima_template_field ***fields,
				     int *num_fields)
{
	const char *template_fmt_ptr;
	struct ima_template_field *found_fields[IMA_TEMPLATE_NUM_FIELDS_MAX];
	int template_num_fields = template_fmt_size(template_fmt);
	int i, len;

	if (template_num_fields > IMA_TEMPLATE_NUM_FIELDS_MAX) {
		pr_err("format string '%s' contains too many fields\n",
		       template_fmt);
		return -EINVAL;
	}

	for (i = 0, template_fmt_ptr = template_fmt; i < template_num_fields;
	     i++, template_fmt_ptr += len + 1) {
		char tmp_field_id[IMA_TEMPLATE_FIELD_ID_MAX_LEN + 1];

		len = strchrnul(template_fmt_ptr, '|') - template_fmt_ptr;
		if (len == 0 || len > IMA_TEMPLATE_FIELD_ID_MAX_LEN) {
			pr_err("Invalid field with length %d\n", len);
			return -EINVAL;
		}

		memcpy(tmp_field_id, template_fmt_ptr, len);
		tmp_field_id[len] = '\0';
		found_fields[i] = lookup_template_field(tmp_field_id);
		if (!found_fields[i]) {
			pr_err("field '%s' not found\n", tmp_field_id);
			return -ENOENT;
		}
	}

	if (fields && num_fields) {
		*fields = kmalloc_array(i, sizeof(*fields), GFP_KERNEL);
		if (*fields == NULL)
			return -ENOMEM;

		memcpy(*fields, found_fields, i * sizeof(*fields));
		*num_fields = i;
	}

	return 0;
}

struct ima_template_desc *ima_template_desc_current(void)
{
	if (!ima_template)
		ima_template =
		    lookup_template_desc(CONFIG_IMA_DEFAULT_TEMPLATE);
	return ima_template;
}

int __init ima_init_template(void)
{
	struct ima_template_desc *template = ima_template_desc_current();
	int result;

	result = template_desc_init_fields(template->fmt,
					   &(template->fields),
					   &(template->num_fields));
	if (result < 0)
		pr_err("template %s init failed, result: %d\n",
		       (strlen(template->name) ?
		       template->name : template->fmt), result);

	return result;
}