security/integrity/ima/ima_crypto.c

/*
 * Copyright (C) 2005,2006,2007,2008 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: ima_crypto.c
 *	Calculates md5/sha1 file hash, template hash, boot-aggreate hash
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/kernel.h>
#include <linux/file.h>
#include <linux/crypto.h>
#include <linux/scatterlist.h>
#include <linux/err.h>
#include <linux/slab.h>
#include <crypto/hash.h>
#include <crypto/hash_info.h>
#include "ima.h"

static struct crypto_shash *ima_shash_tfm;

/**
 * ima_kernel_read - read file content
 *
 * This is a function for reading file content instead of kernel_read().
 * It does not perform locking checks to ensure it cannot be blocked.
 * It does not perform security checks because it is irrelevant for IMA.
 *
 */
static int ima_kernel_read(struct file *file, loff_t offset,
			   char *addr, unsigned long count)
{
	mm_segment_t old_fs;
	char __user *buf = addr;
	ssize_t ret;

	if (!(file->f_mode & FMODE_READ))
		return -EBADF;
	if (!file->f_op->read && !file->f_op->aio_read)
		return -EINVAL;

	old_fs = get_fs();
	set_fs(get_ds());
	if (file->f_op->read)
		ret = file->f_op->read(file, buf, count, &offset);
	else
		ret = do_sync_read(file, buf, count, &offset);
	set_fs(old_fs);
	return ret;
}

int ima_init_crypto(void)
{
	long rc;

	ima_shash_tfm = crypto_alloc_shash(hash_algo_name[ima_hash_algo], 0, 0);
	if (IS_ERR(ima_shash_tfm)) {
		rc = PTR_ERR(ima_shash_tfm);
		pr_err("Can not allocate %s (reason: %ld)\n",
		       hash_algo_name[ima_hash_algo], rc);
		return rc;
	}
	return 0;
}

static struct crypto_shash *ima_alloc_tfm(enum hash_algo algo)
{
	struct crypto_shash *tfm = ima_shash_tfm;
	int rc;

	if (algo != ima_hash_algo && algo < HASH_ALGO__LAST) {
		tfm = crypto_alloc_shash(hash_algo_name[algo], 0, 0);
		if (IS_ERR(tfm)) {
			rc = PTR_ERR(tfm);
			pr_err("Can not allocate %s (reason: %d)\n",
			       hash_algo_name[algo], rc);
		}
	}
	return tfm;
}

static void ima_free_tfm(struct crypto_shash *tfm)
{
	if (tfm != ima_shash_tfm)
		crypto_free_shash(tfm);
}

/*
 * Calculate the MD5/SHA1 file digest
 */
static int ima_calc_file_hash_tfm(struct file *file,
				  struct ima_digest_data *hash,
				  struct crypto_shash *tfm)
{
	loff_t i_size, offset = 0;
	char *rbuf;
	int rc, read = 0;
	struct {
		struct shash_desc shash;
		char ctx[crypto_shash_descsize(tfm)];
	} desc;

	desc.shash.tfm = tfm;
	desc.shash.flags = 0;

	hash->length = crypto_shash_digestsize(tfm);

	rc = crypto_shash_init(&desc.shash);
	if (rc != 0)
		return rc;

	i_size = i_size_read(file_inode(file));

	if (i_size == 0)
		goto out;

	rbuf = kzalloc(PAGE_SIZE, GFP_KERNEL);
	if (!rbuf)
		return -ENOMEM;

	if (!(file->f_mode & FMODE_READ)) {
		file->f_mode |= FMODE_READ;
		read = 1;
	}

	while (offset < i_size) {
		int rbuf_len;

		rbuf_len = ima_kernel_read(file, offset, rbuf, PAGE_SIZE);
		if (rbuf_len < 0) {
			rc = rbuf_len;
			break;
		}
		if (rbuf_len == 0)
			break;
		offset += rbuf_len;

		rc = crypto_shash_update(&desc.shash, rbuf, rbuf_len);
		if (rc)
			break;
	}
	if (read)
		file->f_mode &= ~FMODE_READ;
	kfree(rbuf);
out:
	if (!rc)
		rc = crypto_shash_final(&desc.shash, hash->digest);
	return rc;
}

int ima_calc_file_hash(struct file *file, struct ima_digest_data *hash)
{
	struct crypto_shash *tfm;
	int rc;

	tfm = ima_alloc_tfm(hash->algo);
	if (IS_ERR(tfm))
		return PTR_ERR(tfm);

	rc = ima_calc_file_hash_tfm(file, hash, tfm);

	ima_free_tfm(tfm);

	return rc;
}

/*
 * Calculate the hash of template data
 */
static int ima_calc_field_array_hash_tfm(struct ima_field_data *field_data,
					 struct ima_template_desc *td,
					 int num_fields,
					 struct ima_digest_data *hash,
					 struct crypto_shash *tfm)
{
	struct {
		struct shash_desc shash;
		char ctx[crypto_shash_descsize(tfm)];
	} desc;
	int rc, i;

	desc.shash.tfm = tfm;
	desc.shash.flags = 0;

	hash->length = crypto_shash_digestsize(tfm);

	rc = crypto_shash_init(&desc.shash);
	if (rc != 0)
		return rc;

	for (i = 0; i < num_fields; i++) {
		u8 buffer[IMA_EVENT_NAME_LEN_MAX + 1] = { 0 };
		u8 *data_to_hash = field_data[i].data;
		u32 datalen = field_data[i].len;

		if (strcmp(td->name, IMA_TEMPLATE_IMA_NAME) != 0) {
			rc = crypto_shash_update(&desc.shash,
						(const u8 *) &field_data[i].len,
						sizeof(field_data[i].len));
			if (rc)
				break;
		} else if (strcmp(td->fields[i]->field_id, "n") == 0) {
			memcpy(buffer, data_to_hash, datalen);
			data_to_hash = buffer;
			datalen = IMA_EVENT_NAME_LEN_MAX + 1;
		}
		rc = crypto_shash_update(&desc.shash, data_to_hash, datalen);
		if (rc)
			break;
	}

	if (!rc)
		rc = crypto_shash_final(&desc.shash, hash->digest);

	return rc;
}

int ima_calc_field_array_hash(struct ima_field_data *field_data,
			      struct ima_template_desc *desc, int num_fields,
			      struct ima_digest_data *hash)
{
	struct crypto_shash *tfm;
	int rc;

	tfm = ima_alloc_tfm(hash->algo);
	if (IS_ERR(tfm))
		return PTR_ERR(tfm);

	rc = ima_calc_field_array_hash_tfm(field_data, desc, num_fields,
					   hash, tfm);

	ima_free_tfm(tfm);

	return rc;
}

static void __init ima_pcrread(int idx, u8 *pcr)
{
	if (!ima_used_chip)
		return;

	if (tpm_pcr_read(TPM_ANY_NUM, idx, pcr) != 0)
		pr_err("Error Communicating to TPM chip\n");
}

/*
 * Calculate the boot aggregate hash
 */
static int __init ima_calc_boot_aggregate_tfm(char *digest,
					      struct crypto_shash *tfm)
{
	u8 pcr_i[TPM_DIGEST_SIZE];
	int rc, i;
	struct {
		struct shash_desc shash;
		char ctx[crypto_shash_descsize(tfm)];
	} desc;

	desc.shash.tfm = tfm;
	desc.shash.flags = 0;

	rc = crypto_shash_init(&desc.shash);
	if (rc != 0)
		return rc;

	/* cumulative sha1 over tpm registers 0-7 */
	for (i = TPM_PCR0; i < TPM_PCR8; i++) {
		ima_pcrread(i, pcr_i);
		/* now accumulate with current aggregate */
		rc = crypto_shash_update(&desc.shash, pcr_i, TPM_DIGEST_SIZE);
	}
	if (!rc)
		crypto_shash_final(&desc.shash, digest);
	return rc;
}

int __init ima_calc_boot_aggregate(struct ima_digest_data *hash)
{
	struct crypto_shash *tfm;
	int rc;

	tfm = ima_alloc_tfm(hash->algo);
	if (IS_ERR(tfm))
		return PTR_ERR(tfm);

	hash->length = crypto_shash_digestsize(tfm);
	rc = ima_calc_boot_aggregate_tfm(hash->digest, tfm);

	ima_free_tfm(tfm);

	return rc;
}