crypto.c

linux 内核源代码

/**
 * eCryptfs: Linux filesystem encryption layer
 *
 * Copyright (C) 1997-2004 Erez Zadok
 * Copyright (C) 2001-2004 Stony Brook University
 * Copyright (C) 2004-2007 International Business Machines Corp.
 *   Author(s): Michael A. Halcrow <[e-mail]>
 *   		Michael C. Thompson <[e-mail]>
 *
 * 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; either version 2 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
 * 02111-1307, USA.
 */

#include <linux/fs.h>
#include <linux/mount.h>
#include <linux/pagemap.h>
#include <linux/random.h>
#include <linux/compiler.h>
#include <linux/key.h>
#include <linux/namei.h>
#include <linux/crypto.h>
#include <linux/file.h>
#include <linux/scatterlist.h>
#include "ecryptfs_kernel.h"

static int
ecryptfs_decrypt_page_offset(struct ecryptfs_crypt_stat *crypt_stat,
			     struct page *dst_page, int dst_offset,
			     struct page *src_page, int src_offset, int size,
			     unsigned char *iv);
static int
ecryptfs_encrypt_page_offset(struct ecryptfs_crypt_stat *crypt_stat,
			     struct page *dst_page, int dst_offset,
			     struct page *src_page, int src_offset, int size,
			     unsigned char *iv);

/**
 * ecryptfs_to_hex
 * @dst: Buffer to take hex character representation of contents of
 *       src; must be at least of size (src_size * 2)
 * @src: Buffer to be converted to a hex string respresentation
 * @src_size: number of bytes to convert
 */
void ecryptfs_to_hex(char *dst, char *src, size_t src_size)
{
	int x;

	for (x = 0; x < src_size; x++)
		sprintf(&dst[x * 2], "%.2x", (unsigned char)src[x]);
}

/**
 * ecryptfs_from_hex
 * @dst: Buffer to take the bytes from src hex; must be at least of
 *       size (src_size / 2)
 * @src: Buffer to be converted from a hex string respresentation to raw value
 * @dst_size: size of dst buffer, or number of hex characters pairs to convert
 */
void ecryptfs_from_hex(char *dst, char *src, int dst_size)
{
	int x;
	char tmp[3] = { 0, };

	for (x = 0; x < dst_size; x++) {
		tmp[0] = src[x * 2];
		tmp[1] = src[x * 2 + 1];
		dst[x] = (unsigned char)simple_strtol(tmp, NULL, 16);
	}
}

/**
 * ecryptfs_calculate_md5 - calculates the md5 of @src
 * @dst: Pointer to 16 bytes of allocated memory
 * @crypt_stat: Pointer to crypt_stat struct for the current inode
 * @src: Data to be md5'd
 * @len: Length of @src
 *
 * Uses the allocated crypto context that crypt_stat references to
 * generate the MD5 sum of the contents of src.
 */
static int ecryptfs_calculate_md5(char *dst,
				  struct ecryptfs_crypt_stat *crypt_stat,
				  char *src, int len)
{
	struct scatterlist sg;
	struct hash_desc desc = {
		.tfm = crypt_stat->hash_tfm,
		.flags = CRYPTO_TFM_REQ_MAY_SLEEP
	};
	int rc = 0;

	mutex_lock(&crypt_stat->cs_hash_tfm_mutex);
	sg_init_one(&sg, (u8 *)src, len);
	if (!desc.tfm) {
		desc.tfm = crypto_alloc_hash(ECRYPTFS_DEFAULT_HASH, 0,
					     CRYPTO_ALG_ASYNC);
		if (IS_ERR(desc.tfm)) {
			rc = PTR_ERR(desc.tfm);
			ecryptfs_printk(KERN_ERR, "Error attempting to "
					"allocate crypto context; rc = [%d]\n",
					rc);
			goto out;
		}
		crypt_stat->hash_tfm = desc.tfm;
	}
	rc = crypto_hash_init(&desc);
	if (rc) {
		printk(KERN_ERR
		       "%s: Error initializing crypto hash; rc = [%d]\n",
		       __FUNCTION__, rc);
		goto out;
	}
	rc = crypto_hash_update(&desc, &sg, len);
	if (rc) {
		printk(KERN_ERR
		       "%s: Error updating crypto hash; rc = [%d]\n",
		       __FUNCTION__, rc);
		goto out;
	}
	rc = crypto_hash_final(&desc, dst);
	if (rc) {
		printk(KERN_ERR
		       "%s: Error finalizing crypto hash; rc = [%d]\n",
		       __FUNCTION__, rc);
		goto out;
	}
out:
	mutex_unlock(&crypt_stat->cs_hash_tfm_mutex);
	return rc;
}

static int ecryptfs_crypto_api_algify_cipher_name(char **algified_name,
						  char *cipher_name,
						  char *chaining_modifier)
{
	int cipher_name_len = strlen(cipher_name);
	int chaining_modifier_len = strlen(chaining_modifier);
	int algified_name_len;
	int rc;

	algified_name_len = (chaining_modifier_len + cipher_name_len + 3);
	(*algified_name) = kmalloc(algified_name_len, GFP_KERNEL);
	if (!(*algified_name)) {
		rc = -ENOMEM;
		goto out;
	}
	snprintf((*algified_name), algified_name_len, "%s(%s)",
		 chaining_modifier, cipher_name);
	rc = 0;
out:
	return rc;
}

/**
 * ecryptfs_derive_iv
 * @iv: destination for the derived iv vale
 * @crypt_stat: Pointer to crypt_stat struct for the current inode
 * @offset: Offset of the extent whose IV we are to derive
 *
 * Generate the initialization vector from the given root IV and page
 * offset.
 *
 * Returns zero on success; non-zero on error.
 */
static int ecryptfs_derive_iv(char *iv, struct ecryptfs_crypt_stat *crypt_stat,
			      loff_t offset)
{
	int rc = 0;
	char dst[MD5_DIGEST_SIZE];
	char src[ECRYPTFS_MAX_IV_BYTES + 16];

	if (unlikely(ecryptfs_verbosity > 0)) {
		ecryptfs_printk(KERN_DEBUG, "root iv:\n");
		ecryptfs_dump_hex(crypt_stat->root_iv, crypt_stat->iv_bytes);
	}
	/* TODO: It is probably secure to just cast the least
	 * significant bits of the root IV into an unsigned long and
	 * add the offset to that rather than go through all this
	 * hashing business. -Halcrow */
	memcpy(src, crypt_stat->root_iv, crypt_stat->iv_bytes);
	memset((src + crypt_stat->iv_bytes), 0, 16);
	snprintf((src + crypt_stat->iv_bytes), 16, "%lld", offset);
	if (unlikely(ecryptfs_verbosity > 0)) {
		ecryptfs_printk(KERN_DEBUG, "source:\n");
		ecryptfs_dump_hex(src, (crypt_stat->iv_bytes + 16));
	}
	rc = ecryptfs_calculate_md5(dst, crypt_stat, src,
				    (crypt_stat->iv_bytes + 16));
	if (rc) {
		ecryptfs_printk(KERN_WARNING, "Error attempting to compute "
				"MD5 while generating IV for a page\n");
		goto out;
	}
	memcpy(iv, dst, crypt_stat->iv_bytes);
	if (unlikely(ecryptfs_verbosity > 0)) {
		ecryptfs_printk(KERN_DEBUG, "derived iv:\n");
		ecryptfs_dump_hex(iv, crypt_stat->iv_bytes);
	}
out:
	return rc;
}

/**
 * ecryptfs_init_crypt_stat
 * @crypt_stat: Pointer to the crypt_stat struct to initialize.
 *
 * Initialize the crypt_stat structure.
 */
void
ecryptfs_init_crypt_stat(struct ecryptfs_crypt_stat *crypt_stat)
{
	memset((void *)crypt_stat, 0, sizeof(struct ecryptfs_crypt_stat));
	INIT_LIST_HEAD(&crypt_stat->keysig_list);
	mutex_init(&crypt_stat->keysig_list_mutex);
	mutex_init(&crypt_stat->cs_mutex);
	mutex_init(&crypt_stat->cs_tfm_mutex);
	mutex_init(&crypt_stat->cs_hash_tfm_mutex);
	crypt_stat->flags |= ECRYPTFS_STRUCT_INITIALIZED;
}

/**
 * ecryptfs_destroy_crypt_stat
 * @crypt_stat: Pointer to the crypt_stat struct to initialize.
 *
 * Releases all memory associated with a crypt_stat struct.
 */
void ecryptfs_destroy_crypt_stat(struct ecryptfs_crypt_stat *crypt_stat)
{
	struct ecryptfs_key_sig *key_sig, *key_sig_tmp;

	if (crypt_stat->tfm)
		crypto_free_blkcipher(crypt_stat->tfm);
	if (crypt_stat->hash_tfm)
		crypto_free_hash(crypt_stat->hash_tfm);
	mutex_lock(&crypt_stat->keysig_list_mutex);
	list_for_each_entry_safe(key_sig, key_sig_tmp,
				 &crypt_stat->keysig_list, crypt_stat_list) {
		list_del(&key_sig->crypt_stat_list);
		kmem_cache_free(ecryptfs_key_sig_cache, key_sig);
	}
	mutex_unlock(&crypt_stat->keysig_list_mutex);
	memset(crypt_stat, 0, sizeof(struct ecryptfs_crypt_stat));
}

void ecryptfs_destroy_mount_crypt_stat(
	struct ecryptfs_mount_crypt_stat *mount_crypt_stat)
{
	struct ecryptfs_global_auth_tok *auth_tok, *auth_tok_tmp;

	if (!(mount_crypt_stat->flags & ECRYPTFS_MOUNT_CRYPT_STAT_INITIALIZED))
		return;
	mutex_lock(&mount_crypt_stat->global_auth_tok_list_mutex);
	list_for_each_entry_safe(auth_tok, auth_tok_tmp,
				 &mount_crypt_stat->global_auth_tok_list,
				 mount_crypt_stat_list) {
		list_del(&auth_tok->mount_crypt_stat_list);
		mount_crypt_stat->num_global_auth_toks--;
		if (auth_tok->global_auth_tok_key
		    && !(auth_tok->flags & ECRYPTFS_AUTH_TOK_INVALID))
			key_put(auth_tok->global_auth_tok_key);
		kmem_cache_free(ecryptfs_global_auth_tok_cache, auth_tok);
	}
	mutex_unlock(&mount_crypt_stat->global_auth_tok_list_mutex);
	memset(mount_crypt_stat, 0, sizeof(struct ecryptfs_mount_crypt_stat));
}

/**
 * virt_to_scatterlist
 * @addr: Virtual address
 * @size: Size of data; should be an even multiple of the block size
 * @sg: Pointer to scatterlist array; set to NULL to obtain only
 *      the number of scatterlist structs required in array
 * @sg_size: Max array size
 *
 * Fills in a scatterlist array with page references for a passed
 * virtual address.
 *
 * Returns the number of scatterlist structs in array used
 */
int virt_to_scatterlist(const void *addr, int size, struct scatterlist *sg,
			int sg_size)
{
	int i = 0;
	struct page *pg;
	int offset;
	int remainder_of_page;

	sg_init_table(sg, sg_size);

	while (size > 0 && i < sg_size) {
		pg = virt_to_page(addr);
		offset = offset_in_page(addr);
		if (sg)
			sg_set_page(&sg[i], pg, 0, offset);
		remainder_of_page = PAGE_CACHE_SIZE - offset;
		if (size >= remainder_of_page) {
			if (sg)
				sg[i].length = remainder_of_page;
			addr += remainder_of_page;
			size -= remainder_of_page;
		} else {
			if (sg)
				sg[i].length = size;
			addr += size;
			size = 0;
		}
		i++;
	}
	if (size > 0)
		return -ENOMEM;
	return i;
}

/**
 * encrypt_scatterlist
 * @crypt_stat: Pointer to the crypt_stat struct to initialize.
 * @dest_sg: Destination of encrypted data
 * @src_sg: Data to be encrypted
 * @size: Length of data to be encrypted
 * @iv: iv to use during encryption
 *
 * Returns the number of bytes encrypted; negative value on error
 */
static int encrypt_scatterlist(struct ecryptfs_crypt_stat *crypt_stat,
			       struct scatterlist *dest_sg,
			       struct scatterlist *src_sg, int size,
			       unsigned char *iv)
{
	struct blkcipher_desc desc = {
		.tfm = crypt_stat->tfm,
		.info = iv,
		.flags = CRYPTO_TFM_REQ_MAY_SLEEP
	};
	int rc = 0;

	BUG_ON(!crypt_stat || !crypt_stat->tfm
	       || !(crypt_stat->flags & ECRYPTFS_STRUCT_INITIALIZED));
	if (unlikely(ecryptfs_verbosity > 0)) {
		ecryptfs_printk(KERN_DEBUG, "Key size [%d]; key:\n",
				crypt_stat->key_size);
		ecryptfs_dump_hex(crypt_stat->key,
				  crypt_stat->key_size);
	}
	/* Consider doing this once, when the file is opened */
	mutex_lock(&crypt_stat->cs_tfm_mutex);
	rc = crypto_blkcipher_setkey(crypt_stat->tfm, crypt_stat->key,
				     crypt_stat->key_size);
	if (rc) {
		ecryptfs_printk(KERN_ERR, "Error setting key; rc = [%d]\n",
				rc);
		mutex_unlock(&crypt_stat->cs_tfm_mutex);
		rc = -EINVAL;
		goto out;
	}
	ecryptfs_printk(KERN_DEBUG, "Encrypting [%d] bytes.\n", size);
	crypto_blkcipher_encrypt_iv(&desc, dest_sg, src_sg, size);
	mutex_unlock(&crypt_stat->cs_tfm_mutex);
out:
	return rc;
}

/**
 * ecryptfs_lower_offset_for_extent
 *
 * Convert an eCryptfs page index into a lower byte offset
 */
void ecryptfs_lower_offset_for_extent(loff_t *offset, loff_t extent_num,
				      struct ecryptfs_crypt_stat *crypt_stat)
{
	(*offset) = ((crypt_stat->extent_size
		      * crypt_stat->num_header_extents_at_front)
		     + (crypt_stat->extent_size * extent_num));
}

/**
 * ecryptfs_encrypt_extent
 * @enc_extent_page: Allocated page into which to encrypt the data in
 *                   @page
 * @crypt_stat: crypt_stat containing cryptographic context for the
 *              encryption operation
 * @page: Page containing plaintext data extent to encrypt
 * @extent_offset: Page extent offset for use in generating IV
 *
 * Encrypts one extent of data.
 *
 * Return zero on success; non-zero otherwise
 */
static int ecryptfs_encrypt_extent(struct page *enc_extent_page,
				   struct ecryptfs_crypt_stat *crypt_stat,
				   struct page *page,
				   unsigned long extent_offset)
{
	loff_t extent_base;
	char extent_iv[ECRYPTFS_MAX_IV_BYTES];
	int rc;

	extent_base = (((loff_t)page->index)
		       * (PAGE_CACHE_SIZE / crypt_stat->extent_size));
	rc = ecryptfs_derive_iv(extent_iv, crypt_stat,
				(extent_base + extent_offset));
	if (rc) {
		ecryptfs_printk(KERN_ERR, "Error attempting to "
				"derive IV for extent [0x%.16x]; "
				"rc = [%d]\n", (extent_base + extent_offset),
				rc);
		goto out;
	}
	if (unlikely(ecryptfs_verbosity > 0)) {
		ecryptfs_printk(KERN_DEBUG, "Encrypting extent "
				"with iv:\n");
		ecryptfs_dump_hex(extent_iv, crypt_stat->iv_bytes);
		ecryptfs_printk(KERN_DEBUG, "First 8 bytes before "
				"encryption:\n");
		ecryptfs_dump_hex((char *)
				  (page_address(page)
				   + (extent_offset * crypt_stat->extent_size)),
				  8);
	}
	rc = ecryptfs_encrypt_page_offset(crypt_stat, enc_extent_page, 0,
					  page, (extent_offset
						 * crypt_stat->extent_size),
					  crypt_stat->extent_size, extent_iv);
	if (rc < 0) {
		printk(KERN_ERR "%s: Error attempting to encrypt page with "
		       "page->index = [%ld], extent_offset = [%ld]; "
		       "rc = [%d]\n", __FUNCTION__, page->index, extent_offset,
		       rc);
		goto out;
	}
	rc = 0;
	if (unlikely(ecryptfs_verbosity > 0)) {
		ecryptfs_printk(KERN_DEBUG, "Encrypt extent [0x%.16x]; "
				"rc = [%d]\n", (extent_base + extent_offset),
				rc);
		ecryptfs_printk(KERN_DEBUG, "First 8 bytes after "
				"encryption:\n");
		ecryptfs_dump_hex((char *)(page_address(enc_extent_page)), 8);
	}
out:
	return rc;
}

/**
 * ecryptfs_encrypt_page
 * @page: Page mapped from the eCryptfs inode for the file; contains
 *        decrypted content that needs to be encrypted (to a temporary
 *        page; not in place) and written out to the lower file
 *
 * Encrypt an eCryptfs page. This is done on a per-extent basis. Note
 * that eCryptfs pages may straddle the lower pages -- for instance,
 * if the file was created on a machine with an 8K page size
 * (resulting in an 8K header), and then the file is copied onto a
 * host with a 32K page size, then when reading page 0 of the eCryptfs
 * file, 24K of page 0 of the lower file will be read and decrypted,
 * and then 8K of page 1 of the lower file will be read and decrypted.
 *
 * Returns zero on success; negative on error
 */
int ecryptfs_encrypt_page(struct page *page)
{
	struct inode *ecryptfs_inode;
	struct ecryptfs_crypt_stat *crypt_stat;
	char *enc_extent_virt = NULL;
	struct page *enc_extent_page;