[PATCH] ecryptfs: fs/Makefile and fs/Kconfig

eCryptfs is a stacked cryptographic filesystem for Linux.  It is derived from
Erez Zadok's Cryptfs, implemented through the FiST framework for generating
stacked filesystems.  eCryptfs extends Cryptfs to provide advanced key
management and policy features.  eCryptfs stores cryptographic metadata in the
header of each file written, so that encrypted files can be copied between
hosts; the file will be decryptable with the proper key, and there is no need
to keep track of any additional information aside from what is already in the
encrypted file itself.

[akpm@osdl.org: updates for ongoing API changes]
[bunk@stusta.de: cleanups]
[akpm@osdl.org: alpha build fix]
[akpm@osdl.org: cleanups]
[tytso@mit.edu: inode-diet updates]
[pbadari@us.ibm.com: generic_file_*_read/write() interface updates]
[rdunlap@xenotime.net: printk format fixes]
[akpm@osdl.org: make slab creation and teardown table-driven]
Signed-off-by: Phillip Hellewell <phillip@hellewell.homeip.net>
Signed-off-by: Michael Halcrow <mhalcrow@us.ibm.com>
Signed-off-by: Erez Zadok <ezk@cs.sunysb.edu>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Badari Pulavarty <pbadari@us.ibm.com>
Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 1061 insertions, 0 deletions

diff --git a/fs/ecryptfs/keystore.c b/fs/ecryptfs/keystore.c
new file mode 100644
index 000000000000..ba454785a0c5
--- /dev/null
+++ b/fs/ecryptfs/keystore.c
@@ -0,0 +1,1061 @@
+/**
+ * eCryptfs: Linux filesystem encryption layer
+ * In-kernel key management code.  Includes functions to parse and
+ * write authentication token-related packets with the underlying
+ * file.
+ *
+ * Copyright (C) 2004-2006 International Business Machines Corp.
+ *   Author(s): Michael A. Halcrow <mhalcrow@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/string.h>
+#include <linux/sched.h>
+#include <linux/syscalls.h>
+#include <linux/pagemap.h>
+#include <linux/key.h>
+#include <linux/random.h>
+#include <linux/crypto.h>
+#include <linux/scatterlist.h>
+#include "ecryptfs_kernel.h"
+
+/**
+ * request_key returned an error instead of a valid key address;
+ * determine the type of error, make appropriate log entries, and
+ * return an error code.
+ */
+int process_request_key_err(long err_code)
+{
+	int rc = 0;
+
+	switch (err_code) {
+	case ENOKEY:
+		ecryptfs_printk(KERN_WARNING, "No key\n");
+		rc = -ENOENT;
+		break;
+	case EKEYEXPIRED:
+		ecryptfs_printk(KERN_WARNING, "Key expired\n");
+		rc = -ETIME;
+		break;
+	case EKEYREVOKED:
+		ecryptfs_printk(KERN_WARNING, "Key revoked\n");
+		rc = -EINVAL;
+		break;
+	default:
+		ecryptfs_printk(KERN_WARNING, "Unknown error code: "
+				"[0x%.16x]\n", err_code);
+		rc = -EINVAL;
+	}
+	return rc;
+}
+
+static void wipe_auth_tok_list(struct list_head *auth_tok_list_head)
+{
+	struct list_head *walker;
+	struct ecryptfs_auth_tok_list_item *auth_tok_list_item;
+
+	walker = auth_tok_list_head->next;
+	while (walker != auth_tok_list_head) {
+		auth_tok_list_item =
+		    list_entry(walker, struct ecryptfs_auth_tok_list_item,
+			       list);
+		walker = auth_tok_list_item->list.next;
+		memset(auth_tok_list_item, 0,
+		       sizeof(struct ecryptfs_auth_tok_list_item));
+		kmem_cache_free(ecryptfs_auth_tok_list_item_cache,
+				auth_tok_list_item);
+	}
+}
+
+struct kmem_cache *ecryptfs_auth_tok_list_item_cache;
+
+/**
+ * parse_packet_length
+ * @data: Pointer to memory containing length at offset
+ * @size: This function writes the decoded size to this memory
+ *        address; zero on error
+ * @length_size: The number of bytes occupied by the encoded length
+ *
+ * Returns Zero on success
+ */
+static int parse_packet_length(unsigned char *data, size_t *size,
+			       size_t *length_size)
+{
+	int rc = 0;
+
+	(*length_size) = 0;
+	(*size) = 0;
+	if (data[0] < 192) {
+		/* One-byte length */
+		(*size) = data[0];
+		(*length_size) = 1;
+	} else if (data[0] < 224) {
+		/* Two-byte length */
+		(*size) = ((data[0] - 192) * 256);
+		(*size) += (data[1] + 192);
+		(*length_size) = 2;
+	} else if (data[0] == 255) {
+		/* Five-byte length; we're not supposed to see this */
+		ecryptfs_printk(KERN_ERR, "Five-byte packet length not "
+				"supported\n");
+		rc = -EINVAL;
+		goto out;
+	} else {
+		ecryptfs_printk(KERN_ERR, "Error parsing packet length\n");
+		rc = -EINVAL;
+		goto out;
+	}
+out:
+	return rc;
+}
+
+/**
+ * write_packet_length
+ * @dest: The byte array target into which to write the
+ *       length. Must have at least 5 bytes allocated.
+ * @size: The length to write.
+ * @packet_size_length: The number of bytes used to encode the
+ *                      packet length is written to this address.
+ *
+ * Returns zero on success; non-zero on error.
+ */
+static int write_packet_length(char *dest, size_t size,
+			       size_t *packet_size_length)
+{
+	int rc = 0;
+
+	if (size < 192) {
+		dest[0] = size;
+		(*packet_size_length) = 1;
+	} else if (size < 65536) {
+		dest[0] = (((size - 192) / 256) + 192);
+		dest[1] = ((size - 192) % 256);
+		(*packet_size_length) = 2;
+	} else {
+		rc = -EINVAL;
+		ecryptfs_printk(KERN_WARNING,
+				"Unsupported packet size: [%d]\n", size);
+	}
+	return rc;
+}
+
+/**
+ * parse_tag_3_packet
+ * @crypt_stat: The cryptographic context to modify based on packet
+ *              contents.
+ * @data: The raw bytes of the packet.
+ * @auth_tok_list: eCryptfs parses packets into authentication tokens;
+ *                 a new authentication token will be placed at the end
+ *                 of this list for this packet.
+ * @new_auth_tok: Pointer to a pointer to memory that this function
+ *                allocates; sets the memory address of the pointer to
+ *                NULL on error. This object is added to the
+ *                auth_tok_list.
+ * @packet_size: This function writes the size of the parsed packet
+ *               into this memory location; zero on error.
+ * @max_packet_size: maximum number of bytes to parse
+ *
+ * Returns zero on success; non-zero on error.
+ */
+static int
+parse_tag_3_packet(struct ecryptfs_crypt_stat *crypt_stat,
+		   unsigned char *data, struct list_head *auth_tok_list,
+		   struct ecryptfs_auth_tok **new_auth_tok,
+		   size_t *packet_size, size_t max_packet_size)
+{
+	int rc = 0;
+	size_t body_size;
+	struct ecryptfs_auth_tok_list_item *auth_tok_list_item;
+	size_t length_size;
+
+	(*packet_size) = 0;
+	(*new_auth_tok) = NULL;
+
+	/* we check that:
+	 *   one byte for the Tag 3 ID flag
+	 *   two bytes for the body size
+	 * do not exceed the maximum_packet_size
+	 */
+	if (unlikely((*packet_size) + 3 > max_packet_size)) {
+		ecryptfs_printk(KERN_ERR, "Packet size exceeds max\n");
+		rc = -EINVAL;
+		goto out;
+	}
+
+	/* check for Tag 3 identifyer - one byte */
+	if (data[(*packet_size)++] != ECRYPTFS_TAG_3_PACKET_TYPE) {
+		ecryptfs_printk(KERN_ERR, "Enter w/ first byte != 0x%.2x\n",
+				ECRYPTFS_TAG_3_PACKET_TYPE);
+		rc = -EINVAL;
+		goto out;
+	}
+	/* Released: wipe_auth_tok_list called in ecryptfs_parse_packet_set or
+	 * at end of function upon failure */
+	auth_tok_list_item =
+	    kmem_cache_alloc(ecryptfs_auth_tok_list_item_cache, SLAB_KERNEL);
+	if (!auth_tok_list_item) {
+		ecryptfs_printk(KERN_ERR, "Unable to allocate memory\n");
+		rc = -ENOMEM;
+		goto out;
+	}
+	memset(auth_tok_list_item, 0,
+	       sizeof(struct ecryptfs_auth_tok_list_item));
+	(*new_auth_tok) = &auth_tok_list_item->auth_tok;
+
+	/* check for body size - one to two bytes */
+	rc = parse_packet_length(&data[(*packet_size)], &body_size,
+				 &length_size);
+	if (rc) {
+		ecryptfs_printk(KERN_WARNING, "Error parsing packet length; "
+				"rc = [%d]\n", rc);
+		goto out_free;
+	}
+	if (unlikely(body_size < (0x05 + ECRYPTFS_SALT_SIZE))) {
+		ecryptfs_printk(KERN_WARNING, "Invalid body size ([%d])\n",
+				body_size);
+		rc = -EINVAL;
+		goto out_free;
+	}
+	(*packet_size) += length_size;
+
+	/* now we know the length of the remainting Tag 3 packet size:
+	 *   5 fix bytes for: version string, cipher, S2K ID, hash algo,
+	 *                    number of hash iterations
+	 *   ECRYPTFS_SALT_SIZE bytes for salt
+	 *   body_size bytes minus the stuff above is the encrypted key size
+	 */
+	if (unlikely((*packet_size) + body_size > max_packet_size)) {
+		ecryptfs_printk(KERN_ERR, "Packet size exceeds max\n");
+		rc = -EINVAL;
+		goto out_free;
+	}
+
+	/* There are 5 characters of additional information in the
+	 * packet */
+	(*new_auth_tok)->session_key.encrypted_key_size =
+		body_size - (0x05 + ECRYPTFS_SALT_SIZE);
+	ecryptfs_printk(KERN_DEBUG, "Encrypted key size = [%d]\n",
+			(*new_auth_tok)->session_key.encrypted_key_size);
+
+	/* Version 4 (from RFC2440) - one byte */
+	if (unlikely(data[(*packet_size)++] != 0x04)) {
+		ecryptfs_printk(KERN_DEBUG, "Unknown version number "
+				"[%d]\n", data[(*packet_size) - 1]);
+		rc = -EINVAL;
+		goto out_free;
+	}
+
+	/* cipher - one byte */
+	ecryptfs_cipher_code_to_string(crypt_stat->cipher,
+				       (u16)data[(*packet_size)]);
+	/* A little extra work to differentiate among the AES key
+	 * sizes; see RFC2440 */
+	switch(data[(*packet_size)++]) {
+	case RFC2440_CIPHER_AES_192:
+		crypt_stat->key_size = 24;
+		break;
+	default:
+		crypt_stat->key_size =
+			(*new_auth_tok)->session_key.encrypted_key_size;
+	}
+	ecryptfs_init_crypt_ctx(crypt_stat);
+	/* S2K identifier 3 (from RFC2440) */
+	if (unlikely(data[(*packet_size)++] != 0x03)) {
+		ecryptfs_printk(KERN_ERR, "Only S2K ID 3 is currently "
+				"supported\n");
+		rc = -ENOSYS;
+		goto out_free;
+	}
+
+	/* TODO: finish the hash mapping */
+	/* hash algorithm - one byte */
+	switch (data[(*packet_size)++]) {
+	case 0x01: /* See RFC2440 for these numbers and their mappings */
+		/* Choose MD5 */
+		/* salt - ECRYPTFS_SALT_SIZE bytes */
+		memcpy((*new_auth_tok)->token.password.salt,
+		       &data[(*packet_size)], ECRYPTFS_SALT_SIZE);
+		(*packet_size) += ECRYPTFS_SALT_SIZE;
+
+		/* This conversion was taken straight from RFC2440 */
+		/* number of hash iterations - one byte */
+		(*new_auth_tok)->token.password.hash_iterations =
+			((u32) 16 + (data[(*packet_size)] & 15))
+				<< ((data[(*packet_size)] >> 4) + 6);
+		(*packet_size)++;
+
+		/* encrypted session key -
+		 *   (body_size-5-ECRYPTFS_SALT_SIZE) bytes */
+		memcpy((*new_auth_tok)->session_key.encrypted_key,
+		       &data[(*packet_size)],
+		       (*new_auth_tok)->session_key.encrypted_key_size);
+		(*packet_size) +=
+			(*new_auth_tok)->session_key.encrypted_key_size;
+		(*new_auth_tok)->session_key.flags &=
+			~ECRYPTFS_CONTAINS_DECRYPTED_KEY;
+		(*new_auth_tok)->session_key.flags |=
+			ECRYPTFS_CONTAINS_ENCRYPTED_KEY;
+		(*new_auth_tok)->token.password.hash_algo = 0x01;
+		break;
+	default:
+		ecryptfs_printk(KERN_ERR, "Unsupported hash algorithm: "
+				"[%d]\n", data[(*packet_size) - 1]);
+		rc = -ENOSYS;
+		goto out_free;
+	}
+	(*new_auth_tok)->token_type = ECRYPTFS_PASSWORD;
+	/* TODO: Parametarize; we might actually want userspace to
+	 * decrypt the session key. */
+	ECRYPTFS_CLEAR_FLAG((*new_auth_tok)->session_key.flags,
+			    ECRYPTFS_USERSPACE_SHOULD_TRY_TO_DECRYPT);
+	ECRYPTFS_CLEAR_FLAG((*new_auth_tok)->session_key.flags,
+			    ECRYPTFS_USERSPACE_SHOULD_TRY_TO_ENCRYPT);
+	list_add(&auth_tok_list_item->list, auth_tok_list);
+	goto out;
+out_free:
+	(*new_auth_tok) = NULL;
+	memset(auth_tok_list_item, 0,
+	       sizeof(struct ecryptfs_auth_tok_list_item));
+	kmem_cache_free(ecryptfs_auth_tok_list_item_cache,
+			auth_tok_list_item);
+out:
+	if (rc)
+		(*packet_size) = 0;
+	return rc;
+}
+
+/**
+ * parse_tag_11_packet
+ * @data: The raw bytes of the packet
+ * @contents: This function writes the data contents of the literal
+ *            packet into this memory location
+ * @max_contents_bytes: The maximum number of bytes that this function
+ *                      is allowed to write into contents
+ * @tag_11_contents_size: This function writes the size of the parsed
+ *                        contents into this memory location; zero on
+ *                        error
+ * @packet_size: This function writes the size of the parsed packet
+ *               into this memory location; zero on error
+ * @max_packet_size: maximum number of bytes to parse
+ *
+ * Returns zero on success; non-zero on error.
+ */
+static int
+parse_tag_11_packet(unsigned char *data, unsigned char *contents,
+		    size_t max_contents_bytes, size_t *tag_11_contents_size,
+		    size_t *packet_size, size_t max_packet_size)
+{
+	int rc = 0;
+	size_t body_size;
+	size_t length_size;
+
+	(*packet_size) = 0;
+	(*tag_11_contents_size) = 0;
+
+	/* check that:
+	 *   one byte for the Tag 11 ID flag
+	 *   two bytes for the Tag 11 length
+	 * do not exceed the maximum_packet_size
+	 */
+	if (unlikely((*packet_size) + 3 > max_packet_size)) {
+		ecryptfs_printk(KERN_ERR, "Packet size exceeds max\n");
+		rc = -EINVAL;
+		goto out;
+	}
+
+	/* check for Tag 11 identifyer - one byte */
+	if (data[(*packet_size)++] != ECRYPTFS_TAG_11_PACKET_TYPE) {
+		ecryptfs_printk(KERN_WARNING,
+				"Invalid tag 11 packet format\n");
+		rc = -EINVAL;
+		goto out;
+	}
+
+	/* get Tag 11 content length - one or two bytes */
+	rc = parse_packet_length(&data[(*packet_size)], &body_size,
+				 &length_size);
+	if (rc) {
+		ecryptfs_printk(KERN_WARNING,
+				"Invalid tag 11 packet format\n");
+		goto out;
+	}
+	(*packet_size) += length_size;
+
+	if (body_size < 13) {
+		ecryptfs_printk(KERN_WARNING, "Invalid body size ([%d])\n",
+				body_size);
+		rc = -EINVAL;
+		goto out;
+	}
+	/* We have 13 bytes of surrounding packet values */
+	(*tag_11_contents_size) = (body_size - 13);
+
+	/* now we know the length of the remainting Tag 11 packet size:
+	 *   14 fix bytes for: special flag one, special flag two,
+	 *   		       12 skipped bytes
+	 *   body_size bytes minus the stuff above is the Tag 11 content
+	 */
+	/* FIXME why is the body size one byte smaller than the actual
+	 * size of the body?
+	 * this seems to be an error here as well as in
+	 * write_tag_11_packet() */
+	if (unlikely((*packet_size) + body_size + 1 > max_packet_size)) {
+		ecryptfs_printk(KERN_ERR, "Packet size exceeds max\n");
+		rc = -EINVAL;
+		goto out;
+	}
+
+	/* special flag one - one byte */
+	if (data[(*packet_size)++] != 0x62) {
+		ecryptfs_printk(KERN_WARNING, "Unrecognizable packet\n");
+		rc = -EINVAL;
+		goto out;
+	}
+
+	/* special flag two - one byte */
+	if (data[(*packet_size)++] != 0x08) {
+		ecryptfs_printk(KERN_WARNING, "Unrecognizable packet\n");
+		rc = -EINVAL;
+		goto out;
+	}
+
+	/* skip the next 12 bytes */
+	(*packet_size) += 12; /* We don't care about the filename or
+			       * the timestamp */
+
+	/* get the Tag 11 contents - tag_11_contents_size bytes */
+	memcpy(contents, &data[(*packet_size)], (*tag_11_contents_size));
+	(*packet_size) += (*tag_11_contents_size);
+
+out:
+	if (rc) {
+		(*packet_size) = 0;
+		(*tag_11_contents_size) = 0;
+	}
+	return rc;
+}
+
+/**
+ * decrypt_session_key - Decrypt the session key with the given auth_tok.
+ *
+ * Returns Zero on success; non-zero error otherwise.
+ */
+static int decrypt_session_key(struct ecryptfs_auth_tok *auth_tok,
+			       struct ecryptfs_crypt_stat *crypt_stat)
+{
+	int rc = 0;
+	struct ecryptfs_password *password_s_ptr;
+	struct crypto_tfm *tfm = NULL;
+	struct scatterlist src_sg[2], dst_sg[2];
+	struct mutex *tfm_mutex = NULL;
+	/* TODO: Use virt_to_scatterlist for these */
+	char *encrypted_session_key;
+	char *session_key;
+
+	password_s_ptr = &auth_tok->token.password;
+	if (ECRYPTFS_CHECK_FLAG(password_s_ptr->flags,
+				ECRYPTFS_SESSION_KEY_ENCRYPTION_KEY_SET))
+		ecryptfs_printk(KERN_DEBUG, "Session key encryption key "
+				"set; skipping key generation\n");
+	ecryptfs_printk(KERN_DEBUG, "Session key encryption key (size [%d])"
+			":\n",
+			password_s_ptr->session_key_encryption_key_bytes);
+	if (ecryptfs_verbosity > 0)
+		ecryptfs_dump_hex(password_s_ptr->session_key_encryption_key,
+				  password_s_ptr->
+				  session_key_encryption_key_bytes);
+	if (!strcmp(crypt_stat->cipher,
+		    crypt_stat->mount_crypt_stat->global_default_cipher_name)
+	    && crypt_stat->mount_crypt_stat->global_key_tfm) {
+		tfm = crypt_stat->mount_crypt_stat->global_key_tfm;
+		tfm_mutex = &crypt_stat->mount_crypt_stat->global_key_tfm_mutex;
+	} else {
+		tfm = crypto_alloc_tfm(crypt_stat->cipher,
+				       CRYPTO_TFM_REQ_WEAK_KEY);
+		if (!tfm) {
+			printk(KERN_ERR "Error allocating crypto context\n");
+			rc = -ENOMEM;
+			goto out;
+		}
+	}
+	if (password_s_ptr->session_key_encryption_key_bytes
+	    < crypto_tfm_alg_min_keysize(tfm)) {
+		printk(KERN_WARNING "Session key encryption key is [%d] bytes; "
+		       "minimum keysize for selected cipher is [%d] bytes.\n",
+		       password_s_ptr->session_key_encryption_key_bytes,
+		       crypto_tfm_alg_min_keysize(tfm));
+		rc = -EINVAL;
+		goto out;
+	}
+	if (tfm_mutex)
+		mutex_lock(tfm_mutex);
+	crypto_cipher_setkey(tfm, password_s_ptr->session_key_encryption_key,
+			     crypt_stat->key_size);
+	/* TODO: virt_to_scatterlist */
+	encrypted_session_key = (char *)__get_free_page(GFP_KERNEL);
+	if (!encrypted_session_key) {
+		ecryptfs_printk(KERN_ERR, "Out of memory\n");
+		rc = -ENOMEM;
+		goto out_free_tfm;
+	}
+	session_key = (char *)__get_free_page(GFP_KERNEL);
+	if (!session_key) {
+		kfree(encrypted_session_key);
+		ecryptfs_printk(KERN_ERR, "Out of memory\n");
+		rc = -ENOMEM;
+		goto out_free_tfm;
+	}
+	memcpy(encrypted_session_key, auth_tok->session_key.encrypted_key,
+	       auth_tok->session_key.encrypted_key_size);
+	src_sg[0].page = virt_to_page(encrypted_session_key);
+	src_sg[0].offset = 0;
+	BUG_ON(auth_tok->session_key.encrypted_key_size > PAGE_CACHE_SIZE);
+	src_sg[0].length = auth_tok->session_key.encrypted_key_size;
+	dst_sg[0].page = virt_to_page(session_key);
+	dst_sg[0].offset = 0;
+	auth_tok->session_key.decrypted_key_size =
+	    auth_tok->session_key.encrypted_key_size;
+	dst_sg[0].length = auth_tok->session_key.encrypted_key_size;
+	/* TODO: Handle error condition */
+	crypto_cipher_decrypt(tfm, dst_sg, src_sg,
+			      auth_tok->session_key.encrypted_key_size);
+	auth_tok->session_key.decrypted_key_size =
+	    auth_tok->session_key.encrypted_key_size;
+	memcpy(auth_tok->session_key.decrypted_key, session_key,
+	       auth_tok->session_key.decrypted_key_size);
+	auth_tok->session_key.flags |= ECRYPTFS_CONTAINS_DECRYPTED_KEY;
+	memcpy(crypt_stat->key, auth_tok->session_key.decrypted_key,
+	       auth_tok->session_key.decrypted_key_size);
+	ECRYPTFS_SET_FLAG(crypt_stat->flags, ECRYPTFS_KEY_VALID);
+	ecryptfs_printk(KERN_DEBUG, "Decrypted session key:\n");
+	if (ecryptfs_verbosity > 0)
+		ecryptfs_dump_hex(crypt_stat->key,
+				  crypt_stat->key_size);
+	memset(encrypted_session_key, 0, PAGE_CACHE_SIZE);
+	free_page((unsigned long)encrypted_session_key);
+	memset(session_key, 0, PAGE_CACHE_SIZE);
+	free_page((unsigned long)session_key);
+out_free_tfm:
+	if (tfm_mutex)
+		mutex_unlock(tfm_mutex);
+	else
+		crypto_free_tfm(tfm);
+out:
+	return rc;
+}
+
+/**
+ * ecryptfs_parse_packet_set
+ * @dest: The header page in memory
+ * @version: Version of file format, to guide parsing behavior
+ *
+ * Get crypt_stat to have the file's session key if the requisite key
+ * is available to decrypt the session key.
+ *
+ * Returns Zero if a valid authentication token was retrieved and
+ * processed; negative value for file not encrypted or for error
+ * conditions.
+ */
+int ecryptfs_parse_packet_set(struct ecryptfs_crypt_stat *crypt_stat,
+			      unsigned char *src,
+			      struct dentry *ecryptfs_dentry)
+{
+	size_t i = 0;
+	int rc = 0;
+	size_t found_auth_tok = 0;
+	size_t next_packet_is_auth_tok_packet;
+	char sig[ECRYPTFS_SIG_SIZE_HEX];
+	struct list_head auth_tok_list;
+	struct list_head *walker;
+	struct ecryptfs_auth_tok *chosen_auth_tok = NULL;
+	struct ecryptfs_mount_crypt_stat *mount_crypt_stat =
+		&ecryptfs_superblock_to_private(
+			ecryptfs_dentry->d_sb)->mount_crypt_stat;
+	struct ecryptfs_auth_tok *candidate_auth_tok = NULL;
+	size_t packet_size;
+	struct ecryptfs_auth_tok *new_auth_tok;
+	unsigned char sig_tmp_space[ECRYPTFS_SIG_SIZE];
+	size_t tag_11_contents_size;
+	size_t tag_11_packet_size;
+
+	INIT_LIST_HEAD(&auth_tok_list);
+	/* Parse the header to find as many packets as we can, these will be
+	 * added the our &auth_tok_list */
+	next_packet_is_auth_tok_packet = 1;
+	while (next_packet_is_auth_tok_packet) {
+		size_t max_packet_size = ((PAGE_CACHE_SIZE - 8) - i);
+
+		switch (src[i]) {
+		case ECRYPTFS_TAG_3_PACKET_TYPE:
+			rc = parse_tag_3_packet(crypt_stat,
+						(unsigned char *)&src[i],
+						&auth_tok_list, &new_auth_tok,
+						&packet_size, max_packet_size);
+			if (rc) {
+				ecryptfs_printk(KERN_ERR, "Error parsing "
+						"tag 3 packet\n");
+				rc = -EIO;
+				goto out_wipe_list;
+			}
+			i += packet_size;
+			rc = parse_tag_11_packet((unsigned char *)&src[i],
+						 sig_tmp_space,
+						 ECRYPTFS_SIG_SIZE,
+						 &tag_11_contents_size,
+						 &tag_11_packet_size,
+						 max_packet_size);
+			if (rc) {
+				ecryptfs_printk(KERN_ERR, "No valid "
+						"(ecryptfs-specific) literal "
+						"packet containing "
+						"authentication token "
+						"signature found after "
+						"tag 3 packet\n");
+				rc = -EIO;
+				goto out_wipe_list;
+			}
+			i += tag_11_packet_size;
+			if (ECRYPTFS_SIG_SIZE != tag_11_contents_size) {
+				ecryptfs_printk(KERN_ERR, "Expected "
+						"signature of size [%d]; "
+						"read size [%d]\n",
+						ECRYPTFS_SIG_SIZE,
+						tag_11_contents_size);
+				rc = -EIO;
+				goto out_wipe_list;
+			}
+			ecryptfs_to_hex(new_auth_tok->token.password.signature,
+					sig_tmp_space, tag_11_contents_size);
+			new_auth_tok->token.password.signature[
+				ECRYPTFS_PASSWORD_SIG_SIZE] = '\0';
+			ECRYPTFS_SET_FLAG(crypt_stat->flags,
+					  ECRYPTFS_ENCRYPTED);
+			break;
+		case ECRYPTFS_TAG_11_PACKET_TYPE:
+			ecryptfs_printk(KERN_WARNING, "Invalid packet set "
+					"(Tag 11 not allowed by itself)\n");
+			rc = -EIO;
+			goto out_wipe_list;
+			break;
+		default:
+			ecryptfs_printk(KERN_DEBUG, "No packet at offset "
+					"[%d] of the file header; hex value of "
+					"character is [0x%.2x]\n", i, src[i]);
+			next_packet_is_auth_tok_packet = 0;
+		}
+	}
+	if (list_empty(&auth_tok_list)) {
+		rc = -EINVAL; /* Do not support non-encrypted files in
+			       * the 0.1 release */
+		goto out;
+	}
+	/* If we have a global auth tok, then we should try to use
+	 * it */
+	if (mount_crypt_stat->global_auth_tok) {
+		memcpy(sig, mount_crypt_stat->global_auth_tok_sig,
+		       ECRYPTFS_SIG_SIZE_HEX);
+		chosen_auth_tok = mount_crypt_stat->global_auth_tok;
+	} else
+		BUG(); /* We should always have a global auth tok in
+			* the 0.1 release */
+	/* Scan list to see if our chosen_auth_tok works */
+	list_for_each(walker, &auth_tok_list) {
+		struct ecryptfs_auth_tok_list_item *auth_tok_list_item;
+		auth_tok_list_item =
+		    list_entry(walker, struct ecryptfs_auth_tok_list_item,
+			       list);
+		candidate_auth_tok = &auth_tok_list_item->auth_tok;
+		if (unlikely(ecryptfs_verbosity > 0)) {
+			ecryptfs_printk(KERN_DEBUG,
+					"Considering cadidate auth tok:\n");
+			ecryptfs_dump_auth_tok(candidate_auth_tok);
+		}
+		/* TODO: Replace ECRYPTFS_SIG_SIZE_HEX w/ dynamic value */
+		if (candidate_auth_tok->token_type == ECRYPTFS_PASSWORD
+		    && !strncmp(candidate_auth_tok->token.password.signature,
+				sig, ECRYPTFS_SIG_SIZE_HEX)) {
+			found_auth_tok = 1;
+			goto leave_list;
+			/* TODO: Transfer the common salt into the
+			 * crypt_stat salt */
+		}
+	}
+leave_list:
+	if (!found_auth_tok) {
+		ecryptfs_printk(KERN_ERR, "Could not find authentication "
+				"token on temporary list for sig [%.*s]\n",
+				ECRYPTFS_SIG_SIZE_HEX, sig);
+		rc = -EIO;
+		goto out_wipe_list;
+	} else {
+		memcpy(&(candidate_auth_tok->token.password),
+		       &(chosen_auth_tok->token.password),
+		       sizeof(struct ecryptfs_password));
+		rc = decrypt_session_key(candidate_auth_tok, crypt_stat);
+		if (rc) {
+			ecryptfs_printk(KERN_ERR, "Error decrypting the "
+					"session key\n");
+			goto out_wipe_list;
+		}
+		rc = ecryptfs_compute_root_iv(crypt_stat);
+		if (rc) {
+			ecryptfs_printk(KERN_ERR, "Error computing "
+					"the root IV\n");
+			goto out_wipe_list;
+		}
+	}
+	rc = ecryptfs_init_crypt_ctx(crypt_stat);
+	if (rc) {
+		ecryptfs_printk(KERN_ERR, "Error initializing crypto "
+				"context for cipher [%s]; rc = [%d]\n",
+				crypt_stat->cipher, rc);
+	}
+out_wipe_list:
+	wipe_auth_tok_list(&auth_tok_list);
+out:
+	return rc;
+}
+
+/**
+ * write_tag_11_packet
+ * @dest: Target into which Tag 11 packet is to be written
+ * @max: Maximum packet length
+ * @contents: Byte array of contents to copy in
+ * @contents_length: Number of bytes in contents
+ * @packet_length: Length of the Tag 11 packet written; zero on error
+ *
+ * Returns zero on success; non-zero on error.
+ */
+static int
+write_tag_11_packet(char *dest, int max, char *contents, size_t contents_length,
+		    size_t *packet_length)
+{
+	int rc = 0;
+	size_t packet_size_length;
+
+	(*packet_length) = 0;
+	if ((13 + contents_length) > max) {
+		rc = -EINVAL;
+		ecryptfs_printk(KERN_ERR, "Packet length larger than "
+				"maximum allowable\n");
+		goto out;
+	}
+	/* General packet header */
+	/* Packet tag */
+	dest[(*packet_length)++] = ECRYPTFS_TAG_11_PACKET_TYPE;
+	/* Packet length */
+	rc = write_packet_length(&dest[(*packet_length)],
+				 (13 + contents_length), &packet_size_length);
+	if (rc) {
+		ecryptfs_printk(KERN_ERR, "Error generating tag 11 packet "
+				"header; cannot generate packet length\n");
+		goto out;
+	}
+	(*packet_length) += packet_size_length;
+	/* Tag 11 specific */
+	/* One-octet field that describes how the data is formatted */
+	dest[(*packet_length)++] = 0x62; /* binary data */
+	/* One-octet filename length followed by filename */
+	dest[(*packet_length)++] = 8;
+	memcpy(&dest[(*packet_length)], "_CONSOLE", 8);
+	(*packet_length) += 8;
+	/* Four-octet number indicating modification date */
+	memset(&dest[(*packet_length)], 0x00, 4);
+	(*packet_length) += 4;
+	/* Remainder is literal data */
+	memcpy(&dest[(*packet_length)], contents, contents_length);
+	(*packet_length) += contents_length;
+ out:
+	if (rc)
+		(*packet_length) = 0;
+	return rc;
+}
+
+/**
+ * write_tag_3_packet
+ * @dest: Buffer into which to write the packet
+ * @max: Maximum number of bytes that can be written
+ * @auth_tok: Authentication token
+ * @crypt_stat: The cryptographic context
+ * @key_rec: encrypted key
+ * @packet_size: This function will write the number of bytes that end
+ *               up constituting the packet; set to zero on error
+ *
+ * Returns zero on success; non-zero on error.
+ */
+static int
+write_tag_3_packet(char *dest, size_t max, struct ecryptfs_auth_tok *auth_tok,
+		   struct ecryptfs_crypt_stat *crypt_stat,
+		   struct ecryptfs_key_record *key_rec, size_t *packet_size)
+{
+	int rc = 0;
+
+	size_t i;
+	size_t signature_is_valid = 0;
+	size_t encrypted_session_key_valid = 0;
+	char session_key_encryption_key[ECRYPTFS_MAX_KEY_BYTES];
+	struct scatterlist dest_sg[2];
+	struct scatterlist src_sg[2];
+	struct crypto_tfm *tfm = NULL;
+	struct mutex *tfm_mutex = NULL;
+	size_t key_rec_size;
+	size_t packet_size_length;
+	size_t cipher_code;
+
+	(*packet_size) = 0;
+	/* Check for a valid signature on the auth_tok */
+	for (i = 0; i < ECRYPTFS_SIG_SIZE_HEX; i++)
+		signature_is_valid |= auth_tok->token.password.signature[i];
+	if (!signature_is_valid)
+		BUG();
+	ecryptfs_from_hex((*key_rec).sig, auth_tok->token.password.signature,
+			  ECRYPTFS_SIG_SIZE);
+	encrypted_session_key_valid = 0;
+	for (i = 0; i < crypt_stat->key_size; i++)
+		encrypted_session_key_valid |=
+			auth_tok->session_key.encrypted_key[i];
+	if (encrypted_session_key_valid) {
+		memcpy((*key_rec).enc_key,
+		       auth_tok->session_key.encrypted_key,
+		       auth_tok->session_key.encrypted_key_size);
+		goto encrypted_session_key_set;
+	}
+	if (auth_tok->session_key.encrypted_key_size == 0)
+		auth_tok->session_key.encrypted_key_size =
+			crypt_stat->key_size;
+	if (crypt_stat->key_size == 24
+	    && strcmp("aes", crypt_stat->cipher) == 0) {
+		memset((crypt_stat->key + 24), 0, 8);
+		auth_tok->session_key.encrypted_key_size = 32;
+	}
+	(*key_rec).enc_key_size =
+		auth_tok->session_key.encrypted_key_size;
+	if (ECRYPTFS_CHECK_FLAG(auth_tok->token.password.flags,
+				ECRYPTFS_SESSION_KEY_ENCRYPTION_KEY_SET)) {
+		ecryptfs_printk(KERN_DEBUG, "Using previously generated "
+				"session key encryption key of size [%d]\n",
+				auth_tok->token.password.
+				session_key_encryption_key_bytes);
+		memcpy(session_key_encryption_key,
+		       auth_tok->token.password.session_key_encryption_key,
+		       crypt_stat->key_size);
+		ecryptfs_printk(KERN_DEBUG,
+				"Cached session key " "encryption key: \n");
+		if (ecryptfs_verbosity > 0)
+			ecryptfs_dump_hex(session_key_encryption_key, 16);
+	}
+	if (unlikely(ecryptfs_verbosity > 0)) {
+		ecryptfs_printk(KERN_DEBUG, "Session key encryption key:\n");
+		ecryptfs_dump_hex(session_key_encryption_key, 16);
+	}
+	rc = virt_to_scatterlist(crypt_stat->key,
+				 (*key_rec).enc_key_size, src_sg, 2);
+	if (!rc) {
+		ecryptfs_printk(KERN_ERR, "Error generating scatterlist "
+				"for crypt_stat session key\n");
+		rc = -ENOMEM;
+		goto out;
+	}
+	rc = virt_to_scatterlist((*key_rec).enc_key,
+				 (*key_rec).enc_key_size, dest_sg, 2);
+	if (!rc) {
+		ecryptfs_printk(KERN_ERR, "Error generating scatterlist "
+				"for crypt_stat encrypted session key\n");
+		rc = -ENOMEM;
+		goto out;
+	}
+	if (!strcmp(crypt_stat->cipher,
+		    crypt_stat->mount_crypt_stat->global_default_cipher_name)
+	    && crypt_stat->mount_crypt_stat->global_key_tfm) {
+		tfm = crypt_stat->mount_crypt_stat->global_key_tfm;
+		tfm_mutex = &crypt_stat->mount_crypt_stat->global_key_tfm_mutex;
+	} else
+		tfm = crypto_alloc_tfm(crypt_stat->cipher, 0);
+	if (!tfm) {
+		ecryptfs_printk(KERN_ERR, "Could not initialize crypto "
+				"context for cipher [%s]\n",
+				crypt_stat->cipher);
+		rc = -EINVAL;
+		goto out;
+	}
+	if (tfm_mutex)
+		mutex_lock(tfm_mutex);
+	rc = crypto_cipher_setkey(tfm, session_key_encryption_key,
+				  crypt_stat->key_size);
+	if (rc < 0) {
+		if (tfm_mutex)
+			mutex_unlock(tfm_mutex);
+		ecryptfs_printk(KERN_ERR, "Error setting key for crypto "
+				"context\n");
+		goto out;
+	}
+	rc = 0;
+	ecryptfs_printk(KERN_DEBUG, "Encrypting [%d] bytes of the key\n",
+			crypt_stat->key_size);
+	crypto_cipher_encrypt(tfm, dest_sg, src_sg,
+			      (*key_rec).enc_key_size);
+	if (tfm_mutex)
+		mutex_unlock(tfm_mutex);
+	ecryptfs_printk(KERN_DEBUG, "This should be the encrypted key:\n");
+	if (ecryptfs_verbosity > 0)
+		ecryptfs_dump_hex((*key_rec).enc_key,
+				  (*key_rec).enc_key_size);
+encrypted_session_key_set:
+	/* Now we have a valid key_rec.  Append it to the
+	 * key_rec set. */
+	key_rec_size = (sizeof(struct ecryptfs_key_record)
+			- ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES
+			+ ((*key_rec).enc_key_size));
+	/* TODO: Include a packet size limit as a parameter to this
+	 * function once we have multi-packet headers (for versions
+	 * later than 0.1 */
+	if (key_rec_size >= ECRYPTFS_MAX_KEYSET_SIZE) {
+		ecryptfs_printk(KERN_ERR, "Keyset too large\n");
+		rc = -EINVAL;
+		goto out;
+	}
+	/* TODO: Packet size limit */
+	/* We have 5 bytes of surrounding packet data */
+	if ((0x05 + ECRYPTFS_SALT_SIZE
+	     + (*key_rec).enc_key_size) >= max) {
+		ecryptfs_printk(KERN_ERR, "Authentication token is too "
+				"large\n");
+		rc = -EINVAL;
+		goto out;
+	}
+	/* This format is inspired by OpenPGP; see RFC 2440
+	 * packet tag 3 */
+	dest[(*packet_size)++] = ECRYPTFS_TAG_3_PACKET_TYPE;
+	/* ver+cipher+s2k+hash+salt+iter+enc_key */
+	rc = write_packet_length(&dest[(*packet_size)],
+				 (0x05 + ECRYPTFS_SALT_SIZE
+				  + (*key_rec).enc_key_size),
+				 &packet_size_length);
+	if (rc) {
+		ecryptfs_printk(KERN_ERR, "Error generating tag 3 packet "
+				"header; cannot generate packet length\n");
+		goto out;
+	}
+	(*packet_size) += packet_size_length;
+	dest[(*packet_size)++] = 0x04; /* version 4 */
+	cipher_code = ecryptfs_code_for_cipher_string(crypt_stat);
+	if (cipher_code == 0) {
+		ecryptfs_printk(KERN_WARNING, "Unable to generate code for "
+				"cipher [%s]\n", crypt_stat->cipher);
+		rc = -EINVAL;
+		goto out;
+	}
+	dest[(*packet_size)++] = cipher_code;
+	dest[(*packet_size)++] = 0x03;	/* S2K */
+	dest[(*packet_size)++] = 0x01;	/* MD5 (TODO: parameterize) */
+	memcpy(&dest[(*packet_size)], auth_tok->token.password.salt,
+	       ECRYPTFS_SALT_SIZE);
+	(*packet_size) += ECRYPTFS_SALT_SIZE;	/* salt */
+	dest[(*packet_size)++] = 0x60;	/* hash iterations (65536) */
+	memcpy(&dest[(*packet_size)], (*key_rec).enc_key,
+	       (*key_rec).enc_key_size);
+	(*packet_size) += (*key_rec).enc_key_size;
+out:
+	if (tfm && !tfm_mutex)
+		crypto_free_tfm(tfm);
+	if (rc)
+		(*packet_size) = 0;
+	return rc;
+}
+
+/**
+ * ecryptfs_generate_key_packet_set
+ * @dest: Virtual address from which to write the key record set
+ * @crypt_stat: The cryptographic context from which the
+ *              authentication tokens will be retrieved
+ * @ecryptfs_dentry: The dentry, used to retrieve the mount crypt stat
+ *                   for the global parameters
+ * @len: The amount written
+ * @max: The maximum amount of data allowed to be written
+ *
+ * Generates a key packet set and writes it to the virtual address
+ * passed in.
+ *
+ * Returns zero on success; non-zero on error.
+ */
+int
+ecryptfs_generate_key_packet_set(char *dest_base,
+				 struct ecryptfs_crypt_stat *crypt_stat,
+				 struct dentry *ecryptfs_dentry, size_t *len,
+				 size_t max)
+{
+	int rc = 0;
+	struct ecryptfs_auth_tok *auth_tok;
+	struct ecryptfs_mount_crypt_stat *mount_crypt_stat =
+		&ecryptfs_superblock_to_private(
+			ecryptfs_dentry->d_sb)->mount_crypt_stat;
+	size_t written;
+	struct ecryptfs_key_record key_rec;
+
+	(*len) = 0;
+	if (mount_crypt_stat->global_auth_tok) {
+		auth_tok = mount_crypt_stat->global_auth_tok;
+		if (auth_tok->token_type == ECRYPTFS_PASSWORD) {
+			rc = write_tag_3_packet((dest_base + (*len)),
+						max, auth_tok,
+						crypt_stat, &key_rec,
+						&written);
+			if (rc) {
+				ecryptfs_printk(KERN_WARNING, "Error "
+						"writing tag 3 packet\n");
+				goto out;
+			}
+			(*len) += written;
+			/* Write auth tok signature packet */
+			rc = write_tag_11_packet(
+				(dest_base + (*len)),
+				(max - (*len)),
+				key_rec.sig, ECRYPTFS_SIG_SIZE, &written);
+			if (rc) {
+				ecryptfs_printk(KERN_ERR, "Error writing "
+						"auth tok signature packet\n");
+				goto out;
+			}
+			(*len) += written;
+		} else {
+			ecryptfs_printk(KERN_WARNING, "Unsupported "
+					"authentication token type\n");
+			rc = -EINVAL;
+			goto out;
+		}
+		if (rc) {
+			ecryptfs_printk(KERN_WARNING, "Error writing "
+					"authentication token packet with sig "
+					"= [%s]\n",
+					mount_crypt_stat->global_auth_tok_sig);
+			rc = -EIO;
+			goto out;
+		}
+	} else
+		BUG();
+	if (likely((max - (*len)) > 0)) {
+		dest_base[(*len)] = 0x00;
+	} else {
+		ecryptfs_printk(KERN_ERR, "Error writing boundary byte\n");
+		rc = -EIO;
+	}
+out:
+	if (rc)
+		(*len) = 0;
+	return rc;
+}