crypto.c

linux 内核源代码

	loff_t extent_offset;
	int rc = 0;

	ecryptfs_inode = page->mapping->host;
	crypt_stat =
		&(ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat);
	if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
		rc = ecryptfs_write_lower_page_segment(ecryptfs_inode, page,
						       0, PAGE_CACHE_SIZE);
		if (rc)
			printk(KERN_ERR "%s: Error attempting to copy "
			       "page at index [%ld]\n", __FUNCTION__,
			       page->index);
		goto out;
	}
	enc_extent_virt = kmalloc(PAGE_CACHE_SIZE, GFP_USER);
	if (!enc_extent_virt) {
		rc = -ENOMEM;
		ecryptfs_printk(KERN_ERR, "Error allocating memory for "
				"encrypted extent\n");
		goto out;
	}
	enc_extent_page = virt_to_page(enc_extent_virt);
	for (extent_offset = 0;
	     extent_offset < (PAGE_CACHE_SIZE / crypt_stat->extent_size);
	     extent_offset++) {
		loff_t offset;

		rc = ecryptfs_encrypt_extent(enc_extent_page, crypt_stat, page,
					     extent_offset);
		if (rc) {
			printk(KERN_ERR "%s: Error encrypting extent; "
			       "rc = [%d]\n", __FUNCTION__, rc);
			goto out;
		}
		ecryptfs_lower_offset_for_extent(
			&offset, ((((loff_t)page->index)
				   * (PAGE_CACHE_SIZE
				      / crypt_stat->extent_size))
				  + extent_offset), crypt_stat);
		rc = ecryptfs_write_lower(ecryptfs_inode, enc_extent_virt,
					  offset, crypt_stat->extent_size);
		if (rc) {
			ecryptfs_printk(KERN_ERR, "Error attempting "
					"to write lower page; rc = [%d]"
					"\n", rc);
			goto out;
		}
	}
out:
	kfree(enc_extent_virt);
	return rc;
}

static int ecryptfs_decrypt_extent(struct page *page,
				   struct ecryptfs_crypt_stat *crypt_stat,
				   struct page *enc_extent_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, "Decrypting extent "
				"with iv:\n");
		ecryptfs_dump_hex(extent_iv, crypt_stat->iv_bytes);
		ecryptfs_printk(KERN_DEBUG, "First 8 bytes before "
				"decryption:\n");
		ecryptfs_dump_hex((char *)
				  (page_address(enc_extent_page)
				   + (extent_offset * crypt_stat->extent_size)),
				  8);
	}
	rc = ecryptfs_decrypt_page_offset(crypt_stat, page,
					  (extent_offset
					   * crypt_stat->extent_size),
					  enc_extent_page, 0,
					  crypt_stat->extent_size, extent_iv);
	if (rc < 0) {
		printk(KERN_ERR "%s: Error attempting to decrypt to 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, "Decrypt extent [0x%.16x]; "
				"rc = [%d]\n", (extent_base + extent_offset),
				rc);
		ecryptfs_printk(KERN_DEBUG, "First 8 bytes after "
				"decryption:\n");
		ecryptfs_dump_hex((char *)(page_address(page)
					   + (extent_offset
					      * crypt_stat->extent_size)), 8);
	}
out:
	return rc;
}

/**
 * ecryptfs_decrypt_page
 * @page: Page mapped from the eCryptfs inode for the file; data read
 *        and decrypted from the lower file will be written into this
 *        page
 *
 * Decrypt 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_decrypt_page(struct page *page)
{
	struct inode *ecryptfs_inode;
	struct ecryptfs_crypt_stat *crypt_stat;
	char *enc_extent_virt = NULL;
	struct page *enc_extent_page;
	unsigned long extent_offset;
	int rc = 0;

	ecryptfs_inode = page->mapping->host;
	crypt_stat =
		&(ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat);
	if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
		rc = ecryptfs_read_lower_page_segment(page, page->index, 0,
						      PAGE_CACHE_SIZE,
						      ecryptfs_inode);
		if (rc)
			printk(KERN_ERR "%s: Error attempting to copy "
			       "page at index [%ld]\n", __FUNCTION__,
			       page->index);
		goto out;
	}
	enc_extent_virt = kmalloc(PAGE_CACHE_SIZE, GFP_USER);
	if (!enc_extent_virt) {
		rc = -ENOMEM;
		ecryptfs_printk(KERN_ERR, "Error allocating memory for "
				"encrypted extent\n");
		goto out;
	}
	enc_extent_page = virt_to_page(enc_extent_virt);
	for (extent_offset = 0;
	     extent_offset < (PAGE_CACHE_SIZE / crypt_stat->extent_size);
	     extent_offset++) {
		loff_t offset;

		ecryptfs_lower_offset_for_extent(
			&offset, ((page->index * (PAGE_CACHE_SIZE
						  / crypt_stat->extent_size))
				  + extent_offset), crypt_stat);
		rc = ecryptfs_read_lower(enc_extent_virt, offset,
					 crypt_stat->extent_size,
					 ecryptfs_inode);
		if (rc) {
			ecryptfs_printk(KERN_ERR, "Error attempting "
					"to read lower page; rc = [%d]"
					"\n", rc);
			goto out;
		}
		rc = ecryptfs_decrypt_extent(page, crypt_stat, enc_extent_page,
					     extent_offset);
		if (rc) {
			printk(KERN_ERR "%s: Error encrypting extent; "
			       "rc = [%d]\n", __FUNCTION__, rc);
			goto out;
		}
	}
out:
	kfree(enc_extent_virt);
	return rc;
}

/**
 * decrypt_scatterlist
 * @crypt_stat: Cryptographic context
 * @dest_sg: The destination scatterlist to decrypt into
 * @src_sg: The source scatterlist to decrypt from
 * @size: The number of bytes to decrypt
 * @iv: The initialization vector to use for the decryption
 *
 * Returns the number of bytes decrypted; negative value on error
 */
static int decrypt_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;

	/* 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, "Decrypting [%d] bytes.\n", size);
	rc = crypto_blkcipher_decrypt_iv(&desc, dest_sg, src_sg, size);
	mutex_unlock(&crypt_stat->cs_tfm_mutex);
	if (rc) {
		ecryptfs_printk(KERN_ERR, "Error decrypting; rc = [%d]\n",
				rc);
		goto out;
	}
	rc = size;
out:
	return rc;
}

/**
 * ecryptfs_encrypt_page_offset
 * @crypt_stat: The cryptographic context
 * @dst_page: The page to encrypt into
 * @dst_offset: The offset in the page to encrypt into
 * @src_page: The page to encrypt from
 * @src_offset: The offset in the page to encrypt from
 * @size: The number of bytes to encrypt
 * @iv: The initialization vector to use for the encryption
 *
 * Returns the number of bytes encrypted
 */
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)
{
	struct scatterlist src_sg, dst_sg;

	sg_init_table(&src_sg, 1);
	sg_init_table(&dst_sg, 1);

	sg_set_page(&src_sg, src_page, size, src_offset);
	sg_set_page(&dst_sg, dst_page, size, dst_offset);
	return encrypt_scatterlist(crypt_stat, &dst_sg, &src_sg, size, iv);
}

/**
 * ecryptfs_decrypt_page_offset
 * @crypt_stat: The cryptographic context
 * @dst_page: The page to decrypt into
 * @dst_offset: The offset in the page to decrypt into
 * @src_page: The page to decrypt from
 * @src_offset: The offset in the page to decrypt from
 * @size: The number of bytes to decrypt
 * @iv: The initialization vector to use for the decryption
 *
 * Returns the number of bytes decrypted
 */
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)
{
	struct scatterlist src_sg, dst_sg;

	sg_init_table(&src_sg, 1);
	sg_set_page(&src_sg, src_page, size, src_offset);

	sg_init_table(&dst_sg, 1);
	sg_set_page(&dst_sg, dst_page, size, dst_offset);

	return decrypt_scatterlist(crypt_stat, &dst_sg, &src_sg, size, iv);
}

#define ECRYPTFS_MAX_SCATTERLIST_LEN 4

/**
 * ecryptfs_init_crypt_ctx
 * @crypt_stat: Uninitilized crypt stats structure
 *
 * Initialize the crypto context.
 *
 * TODO: Performance: Keep a cache of initialized cipher contexts;
 * only init if needed
 */
int ecryptfs_init_crypt_ctx(struct ecryptfs_crypt_stat *crypt_stat)
{
	char *full_alg_name;
	int rc = -EINVAL;

	if (!crypt_stat->cipher) {
		ecryptfs_printk(KERN_ERR, "No cipher specified\n");
		goto out;
	}
	ecryptfs_printk(KERN_DEBUG,
			"Initializing cipher [%s]; strlen = [%d]; "
			"key_size_bits = [%d]\n",
			crypt_stat->cipher, (int)strlen(crypt_stat->cipher),
			crypt_stat->key_size << 3);
	if (crypt_stat->tfm) {
		rc = 0;
		goto out;
	}
	mutex_lock(&crypt_stat->cs_tfm_mutex);
	rc = ecryptfs_crypto_api_algify_cipher_name(&full_alg_name,
						    crypt_stat->cipher, "cbc");
	if (rc)
		goto out_unlock;
	crypt_stat->tfm = crypto_alloc_blkcipher(full_alg_name, 0,
						 CRYPTO_ALG_ASYNC);
	kfree(full_alg_name);
	if (IS_ERR(crypt_stat->tfm)) {
		rc = PTR_ERR(crypt_stat->tfm);
		ecryptfs_printk(KERN_ERR, "cryptfs: init_crypt_ctx(): "
				"Error initializing cipher [%s]\n",
				crypt_stat->cipher);
		goto out_unlock;
	}
	crypto_blkcipher_set_flags(crypt_stat->tfm, CRYPTO_TFM_REQ_WEAK_KEY);
	rc = 0;
out_unlock:
	mutex_unlock(&crypt_stat->cs_tfm_mutex);
out:
	return rc;
}

static void set_extent_mask_and_shift(struct ecryptfs_crypt_stat *crypt_stat)
{
	int extent_size_tmp;

	crypt_stat->extent_mask = 0xFFFFFFFF;
	crypt_stat->extent_shift = 0;
	if (crypt_stat->extent_size == 0)
		return;
	extent_size_tmp = crypt_stat->extent_size;
	while ((extent_size_tmp & 0x01) == 0) {
		extent_size_tmp >>= 1;
		crypt_stat->extent_mask <<= 1;
		crypt_stat->extent_shift++;
	}
}

void ecryptfs_set_default_sizes(struct ecryptfs_crypt_stat *crypt_stat)
{
	/* Default values; may be overwritten as we are parsing the
	 * packets. */
	crypt_stat->extent_size = ECRYPTFS_DEFAULT_EXTENT_SIZE;
	set_extent_mask_and_shift(crypt_stat);
	crypt_stat->iv_bytes = ECRYPTFS_DEFAULT_IV_BYTES;
	if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
		crypt_stat->num_header_extents_at_front = 0;
	else {
		if (PAGE_CACHE_SIZE <= ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE)
			crypt_stat->num_header_extents_at_front =
				(ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE
				 / crypt_stat->extent_size);
		else
			crypt_stat->num_header_extents_at_front =
				(PAGE_CACHE_SIZE / crypt_stat->extent_size);
	}
}

/**
 * ecryptfs_compute_root_iv
 * @crypt_stats
 *
 * On error, sets the root IV to all 0's.
 */
int ecryptfs_compute_root_iv(struct ecryptfs_crypt_stat *crypt_stat)
{
	int rc = 0;
	char dst[MD5_DIGEST_SIZE];

	BUG_ON(crypt_stat->iv_bytes > MD5_DIGEST_SIZE);
	BUG_ON(crypt_stat->iv_bytes <= 0);
	if (!(crypt_stat->flags & ECRYPTFS_KEY_VALID)) {
		rc = -EINVAL;
		ecryptfs_printk(KERN_WARNING, "Session key not valid; "
				"cannot generate root IV\n");
		goto out;
	}
	rc = ecryptfs_calculate_md5(dst, crypt_stat, crypt_stat->key,
				    crypt_stat->key_size);
	if (rc) {
		ecryptfs_printk(KERN_WARNING, "Error attempting to compute "
				"MD5 while generating root IV\n");
		goto out;
	}
	memcpy(crypt_stat->root_iv, dst, crypt_stat->iv_bytes);
out:
	if (rc) {
		memset(crypt_stat->root_iv, 0, crypt_stat->iv_bytes);
		crypt_stat->flags |= ECRYPTFS_SECURITY_WARNING;
	}
	return rc;
}

static void ecryptfs_generate_new_key(struct ecryptfs_crypt_stat *crypt_stat)
{
	get_random_bytes(crypt_stat->key, crypt_stat->key_size);
	crypt_stat->flags |= ECRYPTFS_KEY_VALID;
	ecryptfs_compute_root_iv(crypt_stat);
	if (unlikely(ecryptfs_verbosity > 0)) {
		ecryptfs_printk(KERN_DEBUG, "Generated new session key:\n");
		ecryptfs_dump_hex(crypt_stat->key,
				  crypt_stat->key_size);
	}
}

/**
 * ecryptfs_copy_mount_wide_flags_to_inode_flags
 * @crypt_stat: The inode's cryptographic context
 * @mount_crypt_stat: The mount point's cryptographic context
 *
 * This function propagates the mount-wide flags to individual inode
 * flags.
 */
static void ecryptfs_copy_mount_wide_flags_to_inode_flags(
	struct ecryptfs_crypt_stat *crypt_stat,
	struct ecryptfs_mount_crypt_stat *mount_crypt_stat)
{
	if (mount_crypt_stat->flags & ECRYPTFS_XATTR_METADATA_ENABLED)
		crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
	if (mount_crypt_stat->flags & ECRYPTFS_ENCRYPTED_VIEW_ENABLED)
		crypt_stat->flags |= ECRYPTFS_VIEW_AS_ENCRYPTED;
}

static int ecryptfs_copy_mount_wide_sigs_to_inode_sigs(
	struct ecryptfs_crypt_stat *crypt_stat,
	struct ecryptfs_mount_crypt_stat *mount_crypt_stat)
{
	struct ecryptfs_global_auth_tok *global_auth_tok;
	int rc = 0;

	mutex_lock(&mount_crypt_stat->global_auth_tok_list_mutex);
	list_for_each_entry(global_auth_tok,
			    &mount_crypt_stat->global_auth_tok_list,
			    mount_crypt_stat_list) {
		rc = ecryptfs_add_keysig(crypt_stat, global_auth_tok->sig);
		if (rc) {
			printk(KERN_ERR "Error adding keysig; rc = [%d]\n", rc);
			mutex_unlock(
				&mount_crypt_stat->global_auth_tok_list_mutex);
			goto out;
		}
	}
	mutex_unlock(&mount_crypt_stat->global_auth_tok_list_mutex);
out:
	return rc;
}

/**
 * ecryptfs_set_default_crypt_stat_vals
 * @crypt_stat: The inode's cryptographic context
 * @mount_crypt_stat: The mount point's cryptographic context
 *
 * Default values in the event that policy does not override them.
 */