[PATCH 12/13: eCryptfs] Crypto functions

Phillip Hellewell
2006-05-13T03:48:33Z

This is the 12th patch in a series of 13 constituting the kernel
components of the eCryptfs cryptographic filesystem.

eCryptfs crypto functions. Scatterlist abstraction functions. Page
encryption/decryption functions. Inode cryptographic context
initialization functions. Header region manipulation
functions. Functions in which filename and xattr encoding/decoding can
be easily implemented.

Signed-off-by: Phillip Hellewell <phillip@hellewell.homeip.net>
Signed-off-by: Michael Halcrow <mhalcrow@us.ibm.com>

---

crypto.c | 1508 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 1508 insertions(+)

Index: linux-2.6.17-rc3-mm1-ecryptfs/fs/ecryptfs/crypto.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6.17-rc3-mm1-ecryptfs/fs/ecryptfs/crypto.c 2006-05-12 20:00:25.000000000 -0600
@@ -0,0 +1,1508 @@
+/**
+ * eCryptfs: Linux filesystem encryption layer
+ *
+ * Copyright (C) 1997-2004 Erez Zadok
+ * Copyright (C) 2001-2004 Stony Brook University
+ * Copyright (C) 2004-2006 International Business Machines Corp.
+ * Author(s): Michael A. Halcrow <mahalcro@us.ibm.com>
+ * Michael C. Thompson <mcthomps@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; 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 <asm/scatterlist.h>
+#include "ecryptfs_kernel.h"
+
+/**
+ * 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
+ */
+inline void ecryptfs_to_hex(char *dst, char *src, int 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
+ */
+inline 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.
+ */
+int ecryptfs_calculate_md5(char *dst, struct ecryptfs_crypt_stat *crypt_stat,
+ char *src, int len)
+{
+ int rc = 0;
+ struct scatterlist sg;
+
+ sg_init_one(&sg, (u8 *)src, len);
+ if (!crypt_stat->md5_tfm) {
+ crypt_stat->md5_tfm =
+ crypto_alloc_tfm("md5", CRYPTO_TFM_REQ_MAY_SLEEP);
+ if (!crypt_stat->md5_tfm) {
+ rc = -ENOMEM;
+ ecryptfs_printk(KERN_ERR, "Error attempting to "
+ "allocate crypto context\n");
+ goto out;
+ }
+ }
+ crypto_digest_init(crypt_stat->md5_tfm);
+ crypto_digest_update(crypt_stat->md5_tfm, &sg, 1);
+ crypto_digest_final(crypt_stat->md5_tfm, dst);
+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 page whose's 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.
+ */
+int ecryptfs_derive_iv(char *iv, struct ecryptfs_crypt_stat *crypt_stat,
+ pgoff_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, "%ld", 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));
+ mutex_init(&crypt_stat->cs_mutex);
+ ECRYPTFS_SET_FLAG(crypt_stat->flags, ECRYPTFS_STRUCT_INITIALIZED);
+}
+
+/**
+ * ecryptfs_destruct_crypt_stat
+ * @crypt_stat: Pointer to the crypt_stat struct to initialize.
+ *
+ * Releases all memory associated with a crypt_stat struct.
+ */
+void ecryptfs_destruct_crypt_stat(struct ecryptfs_crypt_stat *crypt_stat)
+{
+ if (crypt_stat->tfm)
+ crypto_free_tfm(crypt_stat->tfm);
+ if (crypt_stat->md5_tfm)
+ crypto_free_tfm(crypt_stat->md5_tfm);
+ memset(crypt_stat, 0, sizeof(struct ecryptfs_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;
+
+ while (size > 0 && i < sg_size) {
+ pg = virt_to_page(addr);
+ offset = offset_in_page(addr);
+ if (sg) {
+ sg[i].page = pg;
+ sg[i].offset = 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)
+{
+ int rc = 0;
+
+ ASSERT(crypt_stat && crypt_stat->tfm
+ && ECRYPTFS_CHECK_FLAG(crypt_stat->flags,
+ ECRYPTFS_STRUCT_INITIALIZED));
+ if (unlikely(ecryptfs_verbosity > 0)) {
+ ecryptfs_printk(KERN_DEBUG, "Key size [%d]; key:\n",
+ crypt_stat->key_size_bits / 8);
+ ecryptfs_dump_hex(crypt_stat->key,
+ crypt_stat->key_size_bits / 8);
+ }
+ /* Consider doing this once, when the file is opened */
+ rc = crypto_cipher_setkey(crypt_stat->tfm, crypt_stat->key,
+ crypt_stat->key_size_bits / 8);
+ if (rc) {
+ ecryptfs_printk(KERN_ERR, "Error setting key; rc = [%d]\n",
+ rc);
+ rc = -EINVAL;
+ goto out;
+ }
+ ecryptfs_printk(KERN_DEBUG, "Encrypting [%d] bytes.\n", size);
+ crypto_cipher_encrypt_iv(crypt_stat->tfm, dest_sg, src_sg, size, iv);
+out:
+ return rc;
+}
+
+void
+ecryptfs_extent_to_lwr_pg_idx_and_offset(unsigned long *lower_page_idx,
+ int *byte_offset,
+ struct ecryptfs_crypt_stat *crypt_stat,
+ unsigned long extent_num)
+{
+ unsigned long lower_extent_num;
+ int extents_occupied_by_headers_at_front;
+ int bytes_occupied_by_headers_at_front;
+ int extent_offset;
+ int extents_per_page;
+
+ bytes_occupied_by_headers_at_front =
+ ( crypt_stat->header_extent_size
+ * crypt_stat->num_header_extents_at_front );
+ extents_occupied_by_headers_at_front =
+ ( bytes_occupied_by_headers_at_front
+ / crypt_stat->extent_size );
+ lower_extent_num = extents_occupied_by_headers_at_front + extent_num;
+ extents_per_page = PAGE_CACHE_SIZE / crypt_stat->extent_size;
+ (*lower_page_idx) = lower_extent_num / extents_per_page;
+ extent_offset = lower_extent_num % extents_per_page;
+ (*byte_offset) = extent_offset * crypt_stat->extent_size;
+ ecryptfs_printk(KERN_DEBUG, " * crypt_stat->header_extent_size = "
+ "[%d]\n", crypt_stat->header_extent_size);
+ ecryptfs_printk(KERN_DEBUG, " * crypt_stat->"
+ "num_header_extents_at_front = [%d]\n",
+ crypt_stat->num_header_extents_at_front);
+ ecryptfs_printk(KERN_DEBUG, " * extents_occupied_by_headers_at_"
+ "front = [%d]\n", extents_occupied_by_headers_at_front);
+ ecryptfs_printk(KERN_DEBUG, " * lower_extent_num = [0x%.16x]\n",
+ lower_extent_num);
+ ecryptfs_printk(KERN_DEBUG, " * extents_per_page = [%d]\n",
+ extents_per_page);
+ ecryptfs_printk(KERN_DEBUG, " * (*lower_page_idx) = [0x%.16x]\n",
+ (*lower_page_idx));
+ ecryptfs_printk(KERN_DEBUG, " * extent_offset = [%d]\n",
+ extent_offset);
+ ecryptfs_printk(KERN_DEBUG, " * (*byte_offset) = [%d]\n",
+ (*byte_offset));
+}
+
+int ecryptfs_write_out_page(struct ecryptfs_page_crypt_context *ctx,
+ struct page *lower_page, struct inode *lower_inode,
+ int byte_offset_in_page, int bytes_to_write)
+{
+ int rc = 0;
+
+ if (ctx->mode == ECRYPTFS_PREPARE_COMMIT_MODE) {
+ rc = ecryptfs_commit_lower_page(lower_page, lower_inode,
+ ctx->param.lower_file,
+ byte_offset_in_page,
+ bytes_to_write);
+ if (rc) {
+ ecryptfs_printk(KERN_ERR, "Error calling lower "
+ "commit; rc = [%d]\n", rc);
+ goto out;
+ }
+ } else {
+ rc = ecryptfs_writepage_and_release_lower_page(lower_page,
+ lower_inode,
+ ctx->param.wbc);
+ if (rc) {
+ ecryptfs_printk(KERN_ERR, "Error calling lower "
+ "writepage(); rc = [%d]\n", rc);
+ goto out;
+ }
+ }
+out:
+ return rc;
+}
+
+int ecryptfs_read_in_page(struct ecryptfs_page_crypt_context *ctx,
+ struct page **lower_page, struct inode *lower_inode,
+ unsigned long lower_page_idx, int byte_offset_in_page)
+{
+ int rc = 0;
+
+ if (ctx->mode == ECRYPTFS_PREPARE_COMMIT_MODE) {
+ /* TODO: Limit this to only the data extents that are
+ * needed */
+ rc = ecryptfs_get_lower_page(lower_page, lower_inode,
+ ctx->param.lower_file,
+ lower_page_idx,
+ byte_offset_in_page,
+ (PAGE_CACHE_SIZE
+ - byte_offset_in_page));
+ if (rc) {
+ ecryptfs_printk(
+ KERN_ERR, "Error attempting to grab, map, "
+ "and prepare_write lower page with index "
+ "[0x%.16x]; rc = [%d]\n", lower_page_idx, rc);
+ goto out;
+ }
+ } else {
+ rc = ecryptfs_grab_and_map_lower_page(lower_page, NULL,
+ lower_inode,
+ lower_page_idx);
+ if (rc) {
+ ecryptfs_printk(
+ KERN_ERR, "Error attempting to grab and map "
+ "lower page with index [0x%.16x]; rc = [%d]\n",
+ lower_page_idx, rc);
+ goto out;
+ }
+ }
+out:
+ return rc;
+}
+
+/**
+ * ecryptfs_encrypt_page
+ * @ctx: The context of the page
+ *
+ * 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.
+ *
+ * The actual operations performed on each page depends on the
+ * contents of the ecryptfs_page_crypt_context struct.
+ *
+ * Returns zero on success; negative on error
+ */
+int ecryptfs_encrypt_page(struct ecryptfs_page_crypt_context *ctx)
+{
+ char extent_iv[ECRYPTFS_MAX_IV_BYTES];
+ unsigned long base_extent;
+ unsigned long extent_offset = 0;
+ unsigned long lower_page_idx = 0;
+ unsigned long prior_lower_page_idx = 0;
+ struct page *lower_page;
+ struct inode *lower_inode;
+ struct ecryptfs_inode_info *inode_info;
+ struct ecryptfs_crypt_stat *crypt_stat;
+ int rc = 0;
+ int lower_byte_offset = 0;
+ int orig_byte_offset = 0;
+ int num_extents_per_page;
+#define ECRYPTFS_PAGE_STATE_UNREAD 0
+#define ECRYPTFS_PAGE_STATE_READ 1
+#define ECRYPTFS_PAGE_STATE_MODIFIED 2
+#define ECRYPTFS_PAGE_STATE_WRITTEN 3
+ int page_state;
+
+ lower_inode = ecryptfs_inode_to_lower(ctx->page->mapping->host);
+ inode_info = ecryptfs_inode_to_private(ctx->page->mapping->host);
+ crypt_stat = &inode_info->crypt_stat;
+ if (!ECRYPTFS_CHECK_FLAG(crypt_stat->flags, ECRYPTFS_ENCRYPTED)) {
+ rc = ecryptfs_copy_page_to_lower(ctx->page, lower_inode,
+ ctx->param.lower_file);
+ if (rc)
+ ecryptfs_printk(KERN_ERR, "Error attempting to copy "
+ "page at index [0x%.16x]\n",
+ ctx->page->index);
+ goto out;
+ }
+ num_extents_per_page = PAGE_CACHE_SIZE / crypt_stat->extent_size;
+ base_extent = (ctx->page->index * num_extents_per_page);
+ page_state = ECRYPTFS_PAGE_STATE_UNREAD;
+ while (extent_offset < num_extents_per_page) {
+ ecryptfs_extent_to_lwr_pg_idx_and_offset(
+ &lower_page_idx, &lower_byte_offset, crypt_stat,
+ (base_extent + extent_offset));
+ if (prior_lower_page_idx != lower_page_idx
+ && page_state == ECRYPTFS_PAGE_STATE_MODIFIED) {
+ rc = ecryptfs_write_out_page(ctx, lower_page,
+ lower_inode,
+ orig_byte_offset,
+ (PAGE_CACHE_SIZE
+ - orig_byte_offset));
+ if (rc) {
+ ecryptfs_printk(KERN_ERR, "Error attempting "
+ "to write out page; rc = [%d]"
+ "\n", rc);
+ goto out;
+ }
+ page_state = ECRYPTFS_PAGE_STATE_WRITTEN;
+ }
+ if (page_state == ECRYPTFS_PAGE_STATE_UNREAD
+ || page_state == ECRYPTFS_PAGE_STATE_WRITTEN) {
+ rc = ecryptfs_read_in_page(ctx, &lower_page,
+ lower_inode, lower_page_idx,
+ lower_byte_offset);
+ if (rc) {
+ ecryptfs_printk(KERN_ERR, "Error attempting "
+ "to read in lower page with "
+ "index [0x%.16x]; rc = [%d]\n",
+ lower_page_idx, rc);
+ goto out;
+ }
+ orig_byte_offset = lower_byte_offset;
+ prior_lower_page_idx = lower_page_idx;
+ page_state = ECRYPTFS_PAGE_STATE_READ;
+ }
+ ASSERT(page_state == ECRYPTFS_PAGE_STATE_MODIFIED
+ || page_state == ECRYPTFS_PAGE_STATE_READ);
+ rc = ecryptfs_derive_iv(extent_iv, crypt_stat,
+ (base_extent + extent_offset));
+ if (rc) {
+ ecryptfs_printk(KERN_ERR, "Error attempting to "
+ "derive IV for extent [0x%.16x]; "
+ "rc = [%d]\n",
+ (base_extent + 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(ctx->page)
+ + (extent_offset
+ * crypt_stat->extent_size)), 8);
+ }
+ rc = ecryptfs_encrypt_page_offset(
+ crypt_stat, lower_page, lower_byte_offset, ctx->page,
+ (extent_offset * crypt_stat->extent_size),
+ crypt_stat->extent_size, extent_iv);
+ ecryptfs_printk(KERN_DEBUG, "Encrypt extent [0x%.16x]; "
+ "rc = [%d]\n",
+ (base_extent + extent_offset), rc);
+ if (unlikely(ecryptfs_verbosity > 0)) {
+ ecryptfs_printk(KERN_DEBUG, "First 8 bytes after "
+ "encryption:\n");
+ ecryptfs_dump_hex((char *)(page_address(lower_page)
+ + lower_byte_offset), 8);
+ }
+ page_state = ECRYPTFS_PAGE_STATE_MODIFIED;
+ extent_offset++;
+ }
+ ASSERT(orig_byte_offset == 0);
+ rc = ecryptfs_write_out_page(ctx, lower_page, lower_inode, 0,
+ (lower_byte_offset
+ + crypt_stat->extent_size));
+ if (rc) {
+ ecryptfs_printk(KERN_ERR, "Error attempting to write out "
+ "page; rc = [%d]\n", rc);
+ goto out;
+ }
+out:
+ return rc;
+}
+
+/**
+ * ecryptfs_decrypt_page
+ * @file: The ecryptfs file
+ * @page: The page in ecryptfs to decrypt
+ *
+ * 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 file *file, struct page *page)
+{
+ char extent_iv[ECRYPTFS_MAX_IV_BYTES];
+ unsigned long base_extent;
+ unsigned long extent_offset = 0;
+ unsigned long lower_page_idx = 0;
+ unsigned long prior_lower_page_idx = 0;
+ struct page *lower_page;
+ char *lower_page_virt = NULL;
+ struct inode *lower_inode;
+ struct ecryptfs_crypt_stat *crypt_stat;
+ int rc = 0;
+ int byte_offset;
+ int num_extents_per_page;
+ int page_state;
+
+ crypt_stat = &(ecryptfs_inode_to_private(
+ page->mapping->host)->crypt_stat);
+ lower_inode = ecryptfs_inode_to_lower(page->mapping->host);
+ if (!ECRYPTFS_CHECK_FLAG(crypt_stat->flags, ECRYPTFS_ENCRYPTED)) {
+ rc = ecryptfs_do_readpage(file, page, page->index);
+ if (rc)
+ ecryptfs_printk(KERN_ERR, "Error attempting to copy "
+ "page at index [0x%.16x]\n",
+ page->index);
+ goto out;
+ }
+ num_extents_per_page = PAGE_CACHE_SIZE / crypt_stat->extent_size;
+ base_extent = (page->index * num_extents_per_page);
+ lower_page_virt = kmem_cache_alloc(ecryptfs_lower_page_cache,
+ SLAB_KERNEL);
+ if (!lower_page_virt) {
+ rc = -ENOMEM;
+ ecryptfs_printk(KERN_ERR, "Error getting page for encrypted "
+ "lower page(s)\n");
+ goto out;
+ }
+ lower_page = virt_to_page(lower_page_virt);
+ page_state = ECRYPTFS_PAGE_STATE_UNREAD;
+ while (extent_offset < num_extents_per_page) {
+ ecryptfs_extent_to_lwr_pg_idx_and_offset(
+ &lower_page_idx, &byte_offset, crypt_stat,
+ (base_extent + extent_offset));
+ if (prior_lower_page_idx != lower_page_idx
+ || page_state == ECRYPTFS_PAGE_STATE_UNREAD) {
+ rc = ecryptfs_do_readpage(file, lower_page,
+ lower_page_idx);
+ if (rc) {
+ ecryptfs_printk(KERN_ERR, "Error reading "
+ "lower encrypted page; rc = "
+ "[%d]\n", rc);
+ goto out;
+ }
+ prior_lower_page_idx = lower_page_idx;
+ page_state = ECRYPTFS_PAGE_STATE_READ;
+ }
+ rc = ecryptfs_derive_iv(extent_iv, crypt_stat,
+ (base_extent + extent_offset));
+ if (rc) {
+ ecryptfs_printk(KERN_ERR, "Error attempting to "
+ "derive IV for extent [0x%.16x]; rc = "
+ "[%d]\n",
+ (base_extent + 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((lower_page_virt + byte_offset), 8);
+ }
+ rc = ecryptfs_decrypt_page_offset(crypt_stat, page,
+ (extent_offset
+ * crypt_stat->extent_size),
+ lower_page, byte_offset,
+ crypt_stat->extent_size,
+ extent_iv);
+ if (rc != crypt_stat->extent_size) {
+ ecryptfs_printk(KERN_ERR, "Error attempting to "
+ "decrypt extent [0x%.16x]\n",
+ (base_extent + extent_offset));
+ goto out;
+ }
+ rc = 0;
+ if (unlikely(ecryptfs_verbosity > 0)) {
+ ecryptfs_printk(KERN_DEBUG, "First 8 bytes after "
+ "decryption:\n");
+ ecryptfs_dump_hex((char *)(page_address(page)
+ + byte_offset), 8);
+ }
+ extent_offset++;
+ }
+out:
+ if (lower_page_virt)
+ kmem_cache_free(ecryptfs_lower_page_cache, lower_page_virt);
+ return rc;
+}
+
+/**
+ * decrypt_scatterlist
+ *
+ * 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)
+{
+ int rc = 0;
+
+ /* Consider doing this once, when the file is opened */
+ rc = crypto_cipher_setkey(crypt_stat->tfm, crypt_stat->key,
+ crypt_stat->key_size_bits / 8);
+ if (rc) {
+ ecryptfs_printk(KERN_ERR, "Error setting key; rc = [%d]\n",
+ rc);
+ rc = -EINVAL;
+ goto out;
+ }
+ ecryptfs_printk(KERN_DEBUG, "Decrypting [%d] bytes.\n", size);
+ rc = crypto_cipher_decrypt_iv(crypt_stat->tfm, dest_sg, src_sg, size,
+ iv);
+ if (rc) {
+ ecryptfs_printk(KERN_ERR, "Error decrypting; rc = [%d]\n",
+ rc);
+ goto out;
+ }
+ rc = size;
+out:
+ return rc;
+}
+
+/**
+ * ecryptfs_encrypt_page_offset
+ *
+ * Returns the number of bytes encrypted
+ */
+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;
+
+ src_sg.page = src_page;
+ src_sg.offset = src_offset;
+ src_sg.length = size;
+ dst_sg.page = dst_page;
+ dst_sg.offset = dst_offset;
+ dst_sg.length = size;
+ return encrypt_scatterlist(crypt_stat, &dst_sg, &src_sg, size, iv);
+}
+
+/**
+ * ecryptfs_decrypt_page_offset
+ *
+ * Returns the number of bytes decrypted
+ */
+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;
+
+ src_sg.page = src_page;
+ src_sg.offset = src_offset;
+ src_sg.length = size;
+ dst_sg.page = dst_page;
+ dst_sg.offset = dst_offset;
+ dst_sg.length = size;
+ 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)
+{
+ int rc = -EINVAL;
+
+ if (crypt_stat->cipher == NULL) {
+ ecryptfs_printk(KERN_ERR, "No cipher specified\n");
+ goto out;
+ }
+ ecryptfs_printk(KERN_DEBUG,
+ "Initializing cipher [%s]; strlen = [%d]\n",
+ crypt_stat->cipher, (int)strlen(crypt_stat->cipher));
+ if (crypt_stat->tfm) {
+ rc = 0;
+ goto out;
+ }
+ crypt_stat->tfm = crypto_alloc_tfm(crypt_stat->cipher,
+ ECRYPTFS_DEFAULT_CHAINING_MODE);
+ if (crypt_stat->tfm == NULL) {
+ ecryptfs_printk(KERN_ERR, "cryptfs: init_crypt_ctx(): Error "
+ "initializing cipher [%s]\n",
+ crypt_stat->cipher);
+ goto out;
+ }
+ rc = 0;
+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 (PAGE_CACHE_SIZE <= ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE) {
+ crypt_stat->header_extent_size =
+ ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE;
+ } else
+ crypt_stat->header_extent_size = PAGE_CACHE_SIZE;
+ crypt_stat->num_header_extents_at_front = 1;
+}
+
+/**
+ * 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];
+
+ ASSERT(crypt_stat->iv_bytes <= MD5_DIGEST_SIZE);
+ ASSERT(crypt_stat->iv_bytes > 0);
+ if (!ECRYPTFS_CHECK_FLAG(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_bits / 8));
+ 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);
+ ECRYPTFS_SET_FLAG(crypt_stat->flags,
+ ECRYPTFS_SECURITY_WARNING);
+ }
+ return rc;
+}
+
+/**
+ * ecryptfs_set_default_crypt_stat_vals
+ * @crypt_stat
+ *
+ * Default values in the event that policy does not override them.
+ */
+static void
+ecryptfs_set_default_crypt_stat_vals(struct ecryptfs_crypt_stat *crypt_stat)
+{
+ int key_size_bits = ECRYPTFS_DEFAULT_KEY_BYTES * 8;
+
+ ecryptfs_set_default_sizes(crypt_stat);
+ strcpy(crypt_stat->cipher, ECRYPTFS_DEFAULT_CIPHER);
+ crypt_stat->key_size_bits = key_size_bits;
+ get_random_bytes(crypt_stat->key, key_size_bits / 8);
+ ECRYPTFS_SET_FLAG(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_bits / 8);
+ }
+ crypt_stat->file_version = ECRYPTFS_FILE_VERSION;
+}
+
+/**
+ * ecryptfs_new_file_context
+ * @ecryptfs_dentry
+ *
+ * If the crypto context for the file has not yet been established,
+ * this is where we do that. Establishing a new crypto context
+ * involves the following decisions:
+ * - What cipher to use?
+ * - What set of authentication tokens to use?
+ * Here we just worry about getting enough information into the
+ * authentication tokens so that we know that they are available.
+ * We associate the available authentication tokens with the new file
+ * via the set of signatures in the crypt_stat struct. Later, when
+ * the headers are actually written out, we may again defer to
+ * userspace to perform the encryption of the session key; for the
+ * foreseeable future, this will be the case with public key packets.
+ *
+ * Returns zero on success; non-zero otherwise
+ */
+/* Associate an authentication token(s) with the file */
+int ecryptfs_new_file_context(struct dentry *ecryptfs_dentry)
+{
+ int rc = 0;
+ struct ecryptfs_crypt_stat *crypt_stat =
+ &ecryptfs_inode_to_private(ecryptfs_dentry->d_inode)->crypt_stat;
+ struct ecryptfs_mount_crypt_stat *mount_crypt_stat =
+ &ecryptfs_superblock_to_private(
+ ecryptfs_dentry->d_sb)->mount_crypt_stat;
+ int cipher_name_len;
+
+ ecryptfs_set_default_crypt_stat_vals(crypt_stat);
+ /* See if there are mount crypt options */
+ if (mount_crypt_stat->global_auth_tok) {
+ ecryptfs_printk(KERN_DEBUG, "Initializing context for new "
+ "file using mount_crypt_stat\n");
+ ECRYPTFS_SET_FLAG(crypt_stat->flags, ECRYPTFS_ENCRYPTED);
+ ECRYPTFS_SET_FLAG(crypt_stat->flags, ECRYPTFS_KEY_VALID);
+ memcpy(crypt_stat->keysigs[crypt_stat->num_keysigs++],
+ mount_crypt_stat->global_auth_tok_sig,
+ ECRYPTFS_SIG_SIZE_HEX);
+ cipher_name_len =
+ strlen(mount_crypt_stat->global_default_cipher_name);
+ memcpy(crypt_stat->cipher,
+ mount_crypt_stat->global_default_cipher_name,
+ cipher_name_len);
+ crypt_stat->cipher[cipher_name_len] = '\0';
+ } else
+ /* We should not encounter this scenario since we
+ * should detect lack of global_auth_tok at mount time
+ * TODO: Applies to 0.1 release only; remove in future
+ * release */
+ BUG();
+ rc = ecryptfs_init_crypt_ctx(crypt_stat);
+ if (rc)
+ ecryptfs_printk(KERN_ERR, "Error initializing cryptographic "
+ "context for cipher [%s]: rc = [%d]\n",
+ crypt_stat->cipher, rc);
+ return rc;
+}
+
+/**
+ * contains_ecryptfs_marker - check for the ecryptfs marker
+ * @data: The data block in which to check
+ *
+ * Returns one if marker found; zero if not found
+ */
+int contains_ecryptfs_marker(char *data)
+{
+ u32 m_1, m_2;
+
+ memcpy(&m_1, data, 4);
+ m_1 = be32_to_cpu(m_1);
+ memcpy(&m_2, (data + 4), 4);
+ m_2 = be32_to_cpu(m_2);
+ if ((m_1 ^ MAGIC_ECRYPTFS_MARKER) == m_2)
+ return 1;
+ ecryptfs_printk(KERN_DEBUG, "m_1 = [0x%.8x]; m_2 = [0x%.8x]; "
+ "MAGIC_ECRYPTFS_MARKER = [0x%.8x]\n", m_1, m_2,
+ MAGIC_ECRYPTFS_MARKER);
+ ecryptfs_printk(KERN_DEBUG, "(m_1 ^ MAGIC_ECRYPTFS_MARKER) = "
+ "[0x%.8x]\n", (m_1 ^ MAGIC_ECRYPTFS_MARKER));
+ return 0;
+}
+
+struct ecryptfs_flag_map_elem {
+ u32 file_flag;
+ u32 local_flag;
+};
+
+/* Add support for additional flags by adding elements here. */
+static struct ecryptfs_flag_map_elem ecryptfs_flag_map[] = {
+ {0x00000001, ECRYPTFS_ENABLE_HMAC},
+ {0x00000002, ECRYPTFS_ENCRYPTED}
+};
+
+/**
+ * ecryptfs_process_flags
+ * @crypt_stat
+ * @page_virt: Source data to be parsed
+ * @bytes_read: Updated with the number of bytes read
+ *
+ * Returns zero on success; non-zero if the flag set is invalid
+ */
+static int ecryptfs_process_flags(struct ecryptfs_crypt_stat *crypt_stat,
+ char *page_virt, int *bytes_read)
+{
+ int rc = 0;
+ int i;
+ u32 flags;
+
+ memcpy(&flags, page_virt, 4);
+ flags = be32_to_cpu(flags);
+ for (i = 0; i < ((sizeof(ecryptfs_flag_map)
+ / sizeof(struct ecryptfs_flag_map_elem))); i++)
+ if (flags & ecryptfs_flag_map[i].file_flag) {
+ ECRYPTFS_SET_FLAG(crypt_stat->flags,
+ ecryptfs_flag_map[i].local_flag);
+ } else
+ ECRYPTFS_CLEAR_FLAG(crypt_stat->flags,
+ ecryptfs_flag_map[i].local_flag);
+ /* Version is in top 8 bits of the 32-bit flag vector */
+ crypt_stat->file_version = ((flags >> 24) & 0xFF);
+ (*bytes_read) = 4;
+ return rc;
+}
+
+/**
+ * write_ecryptfs_marker
+ * @page_virt: The pointer to in a page to begin writing the marker
+ * @written: Number of bytes written
+ *
+ * Marker = 0x3c81b7f5
+ */
+static void write_ecryptfs_marker(char *page_virt, int *written)
+{
+ u32 m_1, m_2;
+
+ get_random_bytes(&m_1, (MAGIC_ECRYPTFS_MARKER_SIZE_BYTES / 2));
+ m_2 = (m_1 ^ MAGIC_ECRYPTFS_MARKER);
+ m_1 = cpu_to_be32(m_1);
+ memcpy(page_virt, &m_1, (MAGIC_ECRYPTFS_MARKER_SIZE_BYTES / 2));
+ m_2 = cpu_to_be32(m_2);
+ memcpy(page_virt + (MAGIC_ECRYPTFS_MARKER_SIZE_BYTES / 2), &m_2,
+ (MAGIC_ECRYPTFS_MARKER_SIZE_BYTES / 2));
+ (*written) = MAGIC_ECRYPTFS_MARKER_SIZE_BYTES;
+}
+
+static void
+write_ecryptfs_flags(char *page_virt, struct ecryptfs_crypt_stat *crypt_stat,
+ int *written)
+{
+ u32 flags = 0;
+ int i;
+
+ for (i = 0; i < ((sizeof(ecryptfs_flag_map)
+ / sizeof(struct ecryptfs_flag_map_elem))); i++)
+ if (ECRYPTFS_CHECK_FLAG(crypt_stat->flags,
+ ecryptfs_flag_map[i].local_flag))
+ flags |= ecryptfs_flag_map[i].file_flag;
+ /* Version is in top 8 bits of the 32-bit flag vector */
+ flags |= ((((u8)crypt_stat->file_version) << 24) & 0xFF000000);
+ flags = cpu_to_be32(flags);
+ memcpy(page_virt, &flags, 4);
+ (*written) = 4;
+}
+
+struct ecryptfs_cipher_code_str_map_elem {
+ char cipher_str[16];
+ u16 cipher_code;
+};
+
+/* Add support for additional ciphers by adding elements here. The
+ * cipher_code is whatever OpenPGP applicatoins use to identify the
+ * ciphers. */
+/* List in order of probability. */
+static struct ecryptfs_cipher_code_str_map_elem
+ecryptfs_cipher_code_str_map[] = {
+ {"aes", 0x07},
+ {"blowfish", 0x04},
+ {"des3_ede", 0x02},
+ {"cast5", 0x03}
+};
+
+/**
+ * ecryptfs_code_for_cipher_string
+ * @str: The string representing the cipher name
+ *
+ * Returns zero on no match, or the cipher code on match
+ */
+u16 ecryptfs_code_for_cipher_string(char *str)
+{
+ int i;
+
+ for (i = 0; i < (sizeof(ecryptfs_cipher_code_str_map)
+ / sizeof(struct ecryptfs_cipher_code_str_map_elem));
+ i++)
+ if (strcmp(str, ecryptfs_cipher_code_str_map[i].cipher_str)==0)
+ return ecryptfs_cipher_code_str_map[i].cipher_code;
+ return 0;
+}
+
+/**
+ * ecryptfs_cipher_code_to_string
+ * @str: Destination to write out the cipher name
+ * @cipher_code: The code to convert to cipher name string
+ *
+ * Returns zero on success
+ */
+int ecryptfs_cipher_code_to_string(char *str, u16 cipher_code)
+{
+ int rc = 0;
+ int i;
+
+ str[0] = '\0';
+ for (i = 0; i < (sizeof(ecryptfs_cipher_code_str_map)
+ / sizeof(struct ecryptfs_cipher_code_str_map_elem));
+ i++)
+ if (cipher_code == ecryptfs_cipher_code_str_map[i].cipher_code)
+ strcpy(str, ecryptfs_cipher_code_str_map[i].cipher_str);
+ if (str[0] == '\0') {
+ ecryptfs_printk(KERN_WARNING, "Cipher code not recognized: "
+ "[%d]\n", cipher_code);
+ rc = -EINVAL;
+ }
+ return rc;
+}
+
+/**
+ * ecryptfs_read_header_region
+ * @data
+ * @dentry
+ * @nd
+ *
+ * Returns zero on success; non-zero otherwise
+ */
+int ecryptfs_read_header_region(char *data, struct dentry *dentry,
+ struct nameidata *nd)
+{
+ int rc = 0;
+ struct vfsmount *mnt = NULL;
+ struct file *file = NULL;
+ mm_segment_t oldfs;
+
+ mnt = mntget(nd->mnt);
+ file = dentry_open(dentry, mnt, O_RDONLY);
+ if (IS_ERR(file)) {
+ ecryptfs_printk(KERN_DEBUG, "Error opening file to "
+ "read header region\n");
+ mntput(mnt);
+ rc = PTR_ERR(file);
+ goto out;
+ }
+ file->f_pos = 0;
+ oldfs = get_fs();
+ set_fs(get_ds());
+ /* For releases 0.1 and 0.2, all of the header information
+ * fits in the first data extent-sized region. */
+ rc = file->f_op->read(file, (char __user *)data,
+ ECRYPTFS_DEFAULT_EXTENT_SIZE, &file->f_pos);
+ set_fs(oldfs);
+ fput(file);
+ rc = 0;
+out:
+ return rc;
+}
+
+static void
+write_header_metadata(char *virt, struct ecryptfs_crypt_stat *crypt_stat,
+ int *written)
+{
+ u32 header_extent_size;
+ u16 num_header_extents_at_front;
+
+ header_extent_size = (u32)crypt_stat->header_extent_size;
+ num_header_extents_at_front =
+ (u16)crypt_stat->num_header_extents_at_front;
+ header_extent_size = cpu_to_be32(header_extent_size);
+ memcpy(virt, &header_extent_size, 4);
+ virt += 4;
+ num_header_extents_at_front = cpu_to_be16(num_header_extents_at_front);
+ memcpy(virt, &num_header_extents_at_front, 2);
+ (*written) = 6;
+}
+
+struct kmem_cache *ecryptfs_header_cache_0;
+struct kmem_cache *ecryptfs_header_cache_1;
+struct kmem_cache *ecryptfs_header_cache_2;
+
+/**
+ * ecryptfs_write_headers_virt
+ * @page_virt
+ * @crypt_stat
+ * @ecryptfs_dentry
+ *
+ * Format version: 1
+ *
+ * Header Extent:
+ * Octets 0-7: Unencrypted file size (big-endian)
+ * Octets 8-15: eCryptfs special marker
+ * Octets 16-19: Flags
+ * Octet 16: File format version number (between 0 and 255)
+ * Octets 17-18: Reserved
+ * Octet 19: Bit 1 (lsb): Reserved
+ * Bit 2: Encrypted?
+ * Bits 3-8: Reserved
+ * Octets 20-23: Header extent size (big-endian)
+ * Octets 24-25: Number of header extents at front of file
+ * (big-endian)
+ * Octet 26: Begin RFC 2440 authentication token packet set
+ * Data Extent 0:
+ * Lower data (CBC encrypted)
+ * Data Extent 1:
+ * Lower data (CBC encrypted)
+ * ...
+ *
+ * Returns zero on success
+ */
+int ecryptfs_write_headers_virt(char *page_virt,
+ struct ecryptfs_crypt_stat *crypt_stat,
+ struct dentry *ecryptfs_dentry)
+{
+ int rc;
+ int written;
+ int offset;
+
+ offset = ECRYPTFS_FILE_SIZE_BYTES;
+ write_ecryptfs_marker((page_virt + offset), &written);
+ offset += written;
+ write_ecryptfs_flags((page_virt + offset), crypt_stat, &written);
+ offset += written;
+ write_header_metadata((page_virt + offset), crypt_stat, &written);
+ offset += written;
+ rc = ecryptfs_generate_key_packet_set((page_virt + offset), crypt_stat,
+ ecryptfs_dentry, &written);
+ if (rc)
+ ecryptfs_printk(KERN_WARNING, "Error generating key packet "
+ "set; rc = [%d]\n", rc);
+ return rc;
+}
+
+/**
+ * ecryptfs_write_headers
+ * @lower_file: The lower file struct, which was returned from dentry_open
+ *
+ * Write the file headers out. This will likely involve a userspace
+ * callout, in which the session key is encrypted with one or more
+ * public keys and/or the passphrase necessary to do the encryption is
+ * retrieved via a prompt. Exactly what happens at this point should
+ * be policy-dependent.
+ *
+ * Returns zero on success; non-zero on error
+ */
+int ecryptfs_write_headers(struct dentry *ecryptfs_dentry,
+ struct file *lower_file)
+{
+ mm_segment_t oldfs;
+ struct ecryptfs_crypt_stat *crypt_stat;
+ char *page_virt;
+ int current_header_page;
+ int header_pages;
+ int rc = 0;
+
+ crypt_stat = &ecryptfs_inode_to_private(
+ ecryptfs_dentry->d_inode)->crypt_stat;
+ if (likely(ECRYPTFS_CHECK_FLAG(crypt_stat->flags,
+ ECRYPTFS_ENCRYPTED))) {
+ if (!ECRYPTFS_CHECK_FLAG(crypt_stat->flags,
+ ECRYPTFS_KEY_VALID)) {
+ ecryptfs_printk(KERN_DEBUG, "Key is "
+ "invalid; bailing out\n");
+ rc = -EINVAL;
+ goto out;
+ }
+ } else {
+ rc = -EINVAL;
+ ecryptfs_printk(KERN_WARNING,
+ "Called with crypt_stat->encrypted == 0\n");
+ goto out;
+ }
+ /* Released in this function */
+ page_virt = kmem_cache_alloc(ecryptfs_header_cache_0, SLAB_USER);
+ if (!page_virt) {
+ ecryptfs_printk(KERN_ERR, "Out of memory\n");
+ rc = -ENOMEM;
+ goto out;
+ }
+ memset(page_virt, 0, PAGE_CACHE_SIZE);
+ rc = ecryptfs_write_headers_virt(page_virt, crypt_stat,
+ ecryptfs_dentry);
+ if (unlikely(rc)) {
+ ecryptfs_printk(KERN_ERR, "Error whilst writing headers\n");
+ memset(page_virt, 0, PAGE_CACHE_SIZE);
+ goto out_free;
+ }
+ ecryptfs_printk(KERN_DEBUG,
+ "Writing key packet set to underlying file\n");
+ lower_file->f_pos = 0;
+ oldfs = get_fs();
+ set_fs(get_ds());
+ ecryptfs_printk(KERN_DEBUG, "Calling lower_file->f_op->"
+ "write() w/ header page; lower_file->f_pos = "
+ "[0x%.16x]\n", lower_file->f_pos);
+ lower_file->f_op->write(lower_file, (char __user *)page_virt,
+ PAGE_CACHE_SIZE, &lower_file->f_pos);
+ header_pages = ((crypt_stat->header_extent_size
+ * crypt_stat->num_header_extents_at_front)
+ / PAGE_CACHE_SIZE);
+ memset(page_virt, 0, PAGE_CACHE_SIZE);
+ current_header_page = 1;
+ while (current_header_page < header_pages) {
+ ecryptfs_printk(KERN_DEBUG, "Calling lower_file->f_op->"
+ "write() w/ zero'd page; lower_file->f_pos = "
+ "[0x%.16x]\n", lower_file->f_pos);
+ lower_file->f_op->write(lower_file, (char __user *)page_virt,
+ PAGE_CACHE_SIZE, &lower_file->f_pos);
+ current_header_page++;
+ }
+ set_fs(oldfs);
+ ecryptfs_printk(KERN_DEBUG,
+ "Done writing key packet set to underlying file.\n");
+out_free:
+ kmem_cache_free(ecryptfs_header_cache_0, page_virt);
+out:
+ return rc;
+}
+
+static int parse_header_metadata(struct ecryptfs_crypt_stat *crypt_stat,
+ char *virt, int *bytes_read)
+{
+ int rc = 0;
+ u32 header_extent_size;
+ u16 num_header_extents_at_front;
+
+ memcpy(&header_extent_size, virt, 4);
+ header_extent_size = be32_to_cpu(header_extent_size);
+ virt += 4;
+ memcpy(&num_header_extents_at_front, virt, 2);
+ num_header_extents_at_front = be16_to_cpu(num_header_extents_at_front);
+ crypt_stat->header_extent_size = (int)header_extent_size;
+ crypt_stat->num_header_extents_at_front =
+ (int)num_header_extents_at_front;
+ (*bytes_read) = 6;
+ if (crypt_stat->header_extent_size
+ < ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE) {
+ rc = -EINVAL;
+ ecryptfs_printk(KERN_WARNING, "Invalid header extent size: "
+ "[%d]\n", crypt_stat->header_extent_size);
+ }
+ return rc;
+}
+
+/**
+ * set_default_header_data
+ *
+ * For version 0 file format; this function is only for backwards
+ * compatibility for files created with the prior versions of
+ * eCryptfs.
+ */
+inline void set_default_header_data(struct ecryptfs_crypt_stat *crypt_stat)
+{
+ crypt_stat->header_extent_size = 4096;
+ crypt_stat->num_header_extents_at_front = 1;
+}
+
+/**
+ * ecryptfs_read_headers_virt
+ *
+ * Read/parse the header data. The header format is detailed in the
+ * comment block for the ecryptfs_write_headers_virt() function.
+ *
+ * Returns zero on success
+ */
+int ecryptfs_read_headers_virt(char *page_virt,
+ struct ecryptfs_crypt_stat *crypt_stat,
+ struct dentry *ecryptfs_dentry)
+{
+ int rc = 0;
+ int offset;
+ int bytes_read;
+
+ ecryptfs_set_default_sizes(crypt_stat);
+ offset = ECRYPTFS_FILE_SIZE_BYTES;
+ rc = contains_ecryptfs_marker(page_virt + offset);
+ if (rc == 0) {
+ ecryptfs_printk(KERN_WARNING, "Valid eCryptfs marker not "
+ "found\n");
+ rc = -EINVAL;
+ goto out;
+ }
+ offset += MAGIC_ECRYPTFS_MARKER_SIZE_BYTES;
+ rc = ecryptfs_process_flags(crypt_stat, (page_virt + offset),
+ &bytes_read);
+ if (rc) {
+ ecryptfs_printk(KERN_WARNING, "Error processing flags\n");
+ goto out;
+ }
+ if (crypt_stat->file_version > ECRYPTFS_SUPPORTED_FILE_VERSION) {
+ ecryptfs_printk(KERN_WARNING, "File version is [%d]; only "
+ "file version [%d] is supported by this "
+ "version of eCryptfs\n",
+ crypt_stat->file_version,
+ ECRYPTFS_SUPPORTED_FILE_VERSION);
+ rc = -EINVAL;
+ goto out;
+ }
+ offset += bytes_read;
+ if (crypt_stat->file_version >= 1) {
+ rc = parse_header_metadata(crypt_stat, (page_virt + offset),
+ &bytes_read);
+ if (rc) {
+ ecryptfs_printk(KERN_WARNING, "Error reading header "
+ "metadata; rc = [%d]\n", rc);
+ }
+ offset += bytes_read;
+ } else
+ set_default_header_data(crypt_stat);
+ rc = ecryptfs_parse_packet_set(crypt_stat, (page_virt + offset),
+ ecryptfs_dentry);
+out:
+ return rc;
+}
+
+/**
+ * ecryptfs_read_headers
+ *
+ * Returns zero if valid headers found and parsed; non-zero otherwise
+ */
+int ecryptfs_read_headers(struct dentry *ecryptfs_dentry,
+ struct file *lower_file)
+{
+ int rc = 0;
+ char *page_virt = NULL;
+ mm_segment_t oldfs;
+ ssize_t bytes_read;
+ struct ecryptfs_crypt_stat *crypt_stat =
+ &ecryptfs_inode_to_private(ecryptfs_dentry->d_inode)->crypt_stat;
+
+ /* Read the first page from the underlying file */
+ page_virt = kmem_cache_alloc(ecryptfs_header_cache_1, SLAB_USER);
+ if (!page_virt) {
+ rc = -ENOMEM;
+ ecryptfs_printk(KERN_ERR, "Unable to allocate page_virt\n");
+ goto out;
+ }
+ lower_file->f_pos = 0;
+ oldfs = get_fs();
+ set_fs(get_ds());
+ bytes_read = lower_file->f_op->read(lower_file,
+ (char __user *)page_virt,
+ ECRYPTFS_DEFAULT_EXTENT_SIZE,
+ &lower_file->f_pos);
+ set_fs(oldfs);
+ if (bytes_read != ECRYPTFS_DEFAULT_EXTENT_SIZE) {
+ ecryptfs_printk(KERN_ERR, "Expected size of header not read."
+ "Instead [%d] bytes were read\n", bytes_read);
+ rc = -EINVAL;
+ goto out;
+ }
+ rc = ecryptfs_read_headers_virt(page_virt, crypt_stat,
+ ecryptfs_dentry);
+ if (rc) {
+ ecryptfs_printk(KERN_DEBUG, "Valid eCryptfs headers not "
+ "found\n");
+ rc = -EINVAL;
+ }
+out:
+ if (page_virt) {
+ memset(page_virt, 0, PAGE_CACHE_SIZE);
+ kmem_cache_free(ecryptfs_header_cache_1, page_virt);
+ }
+ return rc;
+}
+
+/**
+ * ecryptfs_encode_filename - converts a plaintext file name to cipher text
+ * @crypt_stat: The crypt_stat struct associated with the file anem to encode
+ * @name: The plaintext name
+ * @length: The length of the plaintext
+ * @encoded_name: The encypted name
+ *
+ * Encrypts and encodes a filename into something that constitutes a
+ * valid filename for a filesystem, with printable characters.
+ *
+ * We assume that we have a properly initialized crypto context,
+ * pointed to by crypt_stat->tfm.
+ *
+ * TODO: Implement filename decoding and decryption here, in place of
+ * memcpy. We are keeping the framework around for now to (1)
+ * facilitate testing of the components needed to implement filename
+ * encryption and (2) to provide a code base from which other
+ * developers in the community can easily implement this feature.
+ *
+ * Returns the length of encoded filename; negative if error
+ */
+int
+ecryptfs_encode_filename(struct ecryptfs_crypt_stat *crypt_stat,
+ const char *name, int length, char **encoded_name)
+{
+ int error = 0;
+
+ (*encoded_name) = kmalloc(length + 2, GFP_KERNEL);
+ if (!(*encoded_name)) {
+ error = -ENOMEM;
+ goto out;
+ }
+ /* TODO: Filename encryption is a scheduled feature for a
+ * future version of eCryptfs. This function is here only for
+ * the purpose of providing a framework for other developers
+ * to easily implement filename encryption. Hint: Replace this
+ * memcpy() with a call to encrypt and encode the
+ * filename, the set the length accordingly. */
+ memcpy((void *)(*encoded_name), (void *)name, length);
+ (*encoded_name)[length] = '\0';
+ error = length + 1;
+out:
+ return error;
+}
+
+/**
+ * ecryptfs_decode_filename - converts the cipher text name to plaintext
+ * @crypt_stat: The crypt_stat struct associated with the file
+ * @name: The filename in cipher text
+ * @length: The length of the cipher text name
+ * @decrypted_name: The plaintext name
+ *
+ * Decodes and decrypts the filename.
+ *
+ * We assume that we have a properly initialized crypto context,
+ * pointed to by crypt_stat->tfm.
+ *
+ * TODO: Implement filename decoding and decryption here, in place of
+ * memcpy. We are keeping the framework around for now to (1)
+ * facilitate testing of the components needed to implement filename
+ * encryption and (2) to provide a code base from which other
+ * developers in the community can easily implement this feature.
+ *
+ * Returns the length of decoded filename; negative if error
+ */
+int
+ecryptfs_decode_filename(struct ecryptfs_crypt_stat *crypt_stat,
+ const char *name, int length, char **decrypted_name)
+{
+ int error = 0;
+
+ (*decrypted_name) = kmalloc(length + 2, GFP_KERNEL);
+ if (!(*decrypted_name)) {
+ error = -ENOMEM;
+ goto out;
+ }
+ /* TODO: Filename encryption is a scheduled feature for a
+ * future version of eCryptfs. This function is here only for
+ * the purpose of providing a framework for other developers
+ * to easily implement filename encryption. Hint: Replace this
+ * memcpy() with a call to decode and decrypt the
+ * filename, the set the length accordingly. */
+ memcpy((void *)(*decrypted_name), (void *)name, length);
+ (*decrypted_name)[length + 1] = '\0'; /* Only for convenience
+ * in printing out the
+ * string in debug
+ * messages */
+ error = length;
+out:
+ return error;
+}