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/*
* 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
*/
#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 "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(ima_hash, 0, 0);
if (IS_ERR(ima_shash_tfm)) {
rc = PTR_ERR(ima_shash_tfm);
pr_err("Can not allocate %s (reason: %ld)\n", ima_hash, rc);
return rc;
}
return 0;
}
/*
* Calculate the MD5/SHA1 file digest
*/
int ima_calc_file_hash(struct file *file, char *digest)
{
loff_t i_size, offset = 0;
char *rbuf;
int rc, read = 0;
struct {
struct shash_desc shash;
char ctx[crypto_shash_descsize(ima_shash_tfm)];
} desc;
desc.shash.tfm = ima_shash_tfm;
desc.shash.flags = 0;
rc = crypto_shash_init(&desc.shash);
if (rc != 0)
return rc;
rbuf = kzalloc(PAGE_SIZE, GFP_KERNEL);
if (!rbuf) {
rc = -ENOMEM;
goto out;
}
if (!(file->f_mode & FMODE_READ)) {
file->f_mode |= FMODE_READ;
read = 1;
}
i_size = i_size_read(file_inode(file));
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;
}
kfree(rbuf);
if (!rc)
rc = crypto_shash_final(&desc.shash, digest);
if (read)
file->f_mode &= ~FMODE_READ;
out:
return rc;
}
/*
* Calculate the hash of a given buffer
*/
int ima_calc_buffer_hash(const void *data, int len, char *digest)
{
struct {
struct shash_desc shash;
char ctx[crypto_shash_descsize(ima_shash_tfm)];
} desc;
desc.shash.tfm = ima_shash_tfm;
desc.shash.flags = 0;
return crypto_shash_digest(&desc.shash, data, len, digest);
}
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("IMA: Error Communicating to TPM chip\n");
}
/*
* Calculate the boot aggregate hash
*/
int __init ima_calc_boot_aggregate(char *digest)
{
u8 pcr_i[IMA_DIGEST_SIZE];
int rc, i;
struct {
struct shash_desc shash;
char ctx[crypto_shash_descsize(ima_shash_tfm)];
} desc;
desc.shash.tfm = ima_shash_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, IMA_DIGEST_SIZE);
}
if (!rc)
crypto_shash_final(&desc.shash, digest);
return rc;
}
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