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Date: Tue, 4 Nov 2008 15:41:20 -0600
From: Michael Halcrow <mhalcrow@...ibm.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
Dustin Kirkland <dustin.kirkland@...il.com>,
Eric Sandeen <sandeen@...hat.com>,
Tyler Hicks <tchicks@...ibm.com>,
David Kleikamp <shaggy@...ibm.com>
Subject: [PATCH 3/5] eCryptfs: Filename Encryption: Encoding and encryption
functions
These functions support encrypting and encoding the filename
contents. The encrypted filename contents may consist of any ASCII
characters. This patch includes a custom encoding mechanism to map the
ASCII characters to a reduced character set that is appropriate for
filenames.
Signed-off-by: Michael Halcrow <mhalcrow@...ibm.com>
---
fs/ecryptfs/crypto.c | 433 ++++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 433 insertions(+), 0 deletions(-)
diff --git a/fs/ecryptfs/crypto.c b/fs/ecryptfs/crypto.c
index c9839df..18c78ab 100644
--- a/fs/ecryptfs/crypto.c
+++ b/fs/ecryptfs/crypto.c
@@ -1721,6 +1721,98 @@ out:
}
/**
+ * ecryptfs_encrypt_filename - encrypt filename
+ *
+ * CBC-encrypts the filename. We do not want to encrypt the same
+ * filename with the same key and IV, which may happen with hard
+ * links, so we prepend random bits to each filename.
+ *
+ * Returns zero on success; non-zero otherwise
+ */
+static int
+ecryptfs_encrypt_filename(struct ecryptfs_filename *filename,
+ struct ecryptfs_crypt_stat *crypt_stat,
+ struct ecryptfs_mount_crypt_stat *mount_crypt_stat)
+{
+ int rc = 0;
+
+ filename->encrypted_filename = NULL;
+ filename->encrypted_filename_size = 0;
+ if ((crypt_stat && (crypt_stat->flags & ECRYPTFS_ENCFN_USE_MOUNT_FNEK))
+ || (mount_crypt_stat && (mount_crypt_stat->flags
+ & ECRYPTFS_GLOBAL_ENCFN_USE_MOUNT_FNEK))) {
+ size_t packet_size;
+ size_t remaining_bytes;
+
+ rc = ecryptfs_write_tag_70_packet(
+ NULL, NULL,
+ &filename->encrypted_filename_size,
+ mount_crypt_stat, NULL,
+ filename->filename_size);
+ if (rc) {
+ printk(KERN_ERR "%s: Error attempting to get packet "
+ "size for tag 72; rc = [%d]\n", __func__,
+ rc);
+ filename->encrypted_filename_size = 0;
+ goto out;
+ }
+ filename->encrypted_filename =
+ kmalloc(filename->encrypted_filename_size, GFP_KERNEL);
+ if (!filename->encrypted_filename) {
+ printk(KERN_ERR "%s: Out of memory whilst attempting "
+ "to kmalloc [%Zd] bytes\n", __func__,
+ filename->encrypted_filename_size);
+ rc = -ENOMEM;
+ goto out;
+ }
+ remaining_bytes = filename->encrypted_filename_size;
+ rc = ecryptfs_write_tag_70_packet(filename->encrypted_filename,
+ &remaining_bytes,
+ &packet_size,
+ mount_crypt_stat,
+ filename->filename,
+ filename->filename_size);
+ if (rc) {
+ printk(KERN_ERR "%s: Error attempting to generate "
+ "tag 70 packet; rc = [%d]\n", __func__,
+ rc);
+ kfree(filename->encrypted_filename);
+ filename->encrypted_filename = NULL;
+ filename->encrypted_filename_size = 0;
+ goto out;
+ }
+ filename->encrypted_filename_size = packet_size;
+ } else {
+ printk(KERN_ERR "%s: No support for requested filename "
+ "encryption method in this release\n", __func__);
+ rc = -ENOTSUPP;
+ goto out;
+ }
+out:
+ return rc;
+}
+
+static int ecryptfs_copy_filename(char **copied_name, size_t *copied_name_size,
+ const char *name, size_t name_size)
+{
+ int rc = 0;
+
+ (*copied_name) = kmalloc((name_size + 2), GFP_KERNEL);
+ if (!(*copied_name)) {
+ rc = -ENOMEM;
+ goto out;
+ }
+ memcpy((void *)(*copied_name), (void *)name, name_size);
+ (*copied_name)[(name_size)] = '\0'; /* Only for convenience
+ * in printing out the
+ * string in debug
+ * messages */
+ (*copied_name_size) = (name_size + 1);
+out:
+ return rc;
+}
+
+/**
* ecryptfs_process_key_cipher - Perform key cipher initialization.
* @key_tfm: Crypto context for key material, set by this function
* @cipher_name: Name of the cipher
@@ -1911,3 +2003,344 @@ out:
mutex_unlock(&key_tfm_list_mutex);
return rc;
}
+
+/* 64 characters forming a 6-bit target field */
+static unsigned char *portable_filename_chars = ("-.0123456789ABCD"
+ "EFGHIJKLMNOPQRST"
+ "UVWXYZabcdefghij"
+ "klmnopqrstuvwxyz");
+
+/* We could either offset on every reverse map or just pad some 0x00's
+ * at the front here */
+static unsigned char filename_rev_map[] = {
+ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 7 */
+ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 15 */
+ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 23 */
+ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 31 */
+ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 39 */
+ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, /* 47 */
+ 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, /* 55 */
+ 0x0A, 0x0B, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 63 */
+ 0x00, 0x0C, 0x0D, 0x0E, 0x0F, 0x10, 0x11, 0x12, /* 71 */
+ 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1A, /* 79 */
+ 0x1B, 0x1C, 0x1D, 0x1E, 0x1F, 0x20, 0x21, 0x22, /* 87 */
+ 0x23, 0x24, 0x25, 0x00, 0x00, 0x00, 0x00, 0x00, /* 95 */
+ 0x00, 0x26, 0x27, 0x28, 0x29, 0x2A, 0x2B, 0x2C, /* 103 */
+ 0x2D, 0x2E, 0x2F, 0x30, 0x31, 0x32, 0x33, 0x34, /* 111 */
+ 0x35, 0x36, 0x37, 0x38, 0x39, 0x3A, 0x3B, 0x3C, /* 119 */
+ 0x3D, 0x3E, 0x3F
+};
+
+/**
+ * ecryptfs_encode_for_filename
+ * @dst: Destination location for encoded filename
+ * @dst_size: Size of the encoded filename in bytes
+ * @src: Source location for the filename to encode
+ * @src_size: Size of the source in bytes
+ */
+void ecryptfs_encode_for_filename(unsigned char *dst, size_t *dst_size,
+ unsigned char *src, size_t src_size)
+{
+ size_t num_blocks;
+ size_t block_num = 0;
+ size_t dst_offset = 0;
+ unsigned char last_block[3];
+
+ if (src_size == 0) {
+ (*dst_size) = 0;
+ goto out;
+ }
+ num_blocks = (src_size / 3);
+ if ((src_size % 3) == 0) {
+ memcpy(last_block, (&src[src_size - 3]), 3);
+ } else {
+ num_blocks++;
+ last_block[2] = 0x00;
+ switch (src_size % 3) {
+ case 1:
+ last_block[0] = src[src_size - 1];
+ last_block[1] = 0x00;
+ break;
+ case 2:
+ last_block[0] = src[src_size - 2];
+ last_block[1] = src[src_size - 1];
+ }
+ }
+ (*dst_size) = (num_blocks * 4);
+ if (!dst)
+ goto out;
+ while (block_num < num_blocks) {
+ unsigned char *src_block;
+ unsigned char dst_block[4];
+
+ if (block_num == (num_blocks - 1))
+ src_block = last_block;
+ else
+ src_block = &src[block_num * 3];
+ dst_block[0] = ((src_block[0] >> 2) & 0x3F);
+ dst_block[1] = (((src_block[0] << 4) & 0x30)
+ | ((src_block[1] >> 4) & 0x0F));
+ dst_block[2] = (((src_block[1] << 2) & 0x3C)
+ | ((src_block[2] >> 6) & 0x03));
+ dst_block[3] = (src_block[2] & 0x3F);
+ dst[dst_offset++] = portable_filename_chars[dst_block[0]];
+ dst[dst_offset++] = portable_filename_chars[dst_block[1]];
+ dst[dst_offset++] = portable_filename_chars[dst_block[2]];
+ dst[dst_offset++] = portable_filename_chars[dst_block[3]];
+ block_num++;
+ }
+out:
+ return;
+}
+
+int ecryptfs_decode_from_filename(unsigned char *dst, size_t *dst_size,
+ const unsigned char *src, size_t src_size)
+{
+ u8 current_bit_offset = 0;
+ size_t src_byte_offset = 0;
+ size_t dst_byte_offset = 0;
+ int rc = 0;
+
+ if (dst == NULL) {
+ /* Not exact; conservatively long */
+ (*dst_size) = (((src_size + 1) * 3) / 4);
+ goto out;
+ }
+ while (src_byte_offset < src_size) {
+ unsigned char src_byte =
+ filename_rev_map[(int)src[src_byte_offset]];
+
+ switch (current_bit_offset) {
+ case 0:
+ dst[dst_byte_offset] = (src_byte << 2);
+ current_bit_offset = 6;
+ break;
+ case 6:
+ dst[dst_byte_offset++] |= (src_byte >> 4);
+ dst[dst_byte_offset] = ((src_byte & 0xF)
+ << 4);
+ current_bit_offset = 4;
+ break;
+ case 4:
+ dst[dst_byte_offset++] |= (src_byte >> 2);
+ dst[dst_byte_offset] = (src_byte << 6);
+ current_bit_offset = 2;
+ break;
+ case 2:
+ dst[dst_byte_offset++] |= (src_byte);
+ dst[dst_byte_offset] = 0;
+ current_bit_offset = 0;
+ break;
+ }
+ src_byte_offset++;
+ }
+ (*dst_size) = dst_byte_offset;
+out:
+ return rc;
+}
+
+/**
+ * ecryptfs_encrypt_and_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.
+ *
+ * Returns zero on success; non-zero on otherwise
+ */
+int ecryptfs_encrypt_and_encode_filename(
+ char **encoded_name,
+ size_t *encoded_name_size,
+ struct ecryptfs_crypt_stat *crypt_stat,
+ struct ecryptfs_mount_crypt_stat *mount_crypt_stat,
+ const char *name, size_t name_size)
+{
+ size_t encoded_name_no_prefix_size;
+ int rc = 0;
+
+ (*encoded_name) = NULL;
+ (*encoded_name_size) = 0;
+ if ((crypt_stat && (crypt_stat->flags & ECRYPTFS_ENCRYPT_FILENAMES))
+ || (mount_crypt_stat && (mount_crypt_stat->flags
+ & ECRYPTFS_GLOBAL_ENCRYPT_FILENAMES))) {
+ struct ecryptfs_filename *filename;
+
+ filename = kzalloc(sizeof(*filename), GFP_KERNEL);
+ if (!filename) {
+ printk(KERN_ERR "%s: Out of memory whilst attempting "
+ "to kzalloc [%d] bytes\n", __func__,
+ sizeof(*filename));
+ rc = -ENOMEM;
+ goto out;
+ }
+ filename->filename = (char *)name;
+ filename->filename_size = name_size;
+ rc = ecryptfs_encrypt_filename(filename, crypt_stat,
+ mount_crypt_stat);
+ if (rc) {
+ printk(KERN_ERR "%s: Error attempting to encrypt "
+ "filename; rc = [%d]\n", __func__, rc);
+ kfree(filename);
+ goto out;
+ }
+ ecryptfs_encode_for_filename(
+ NULL, &encoded_name_no_prefix_size,
+ filename->encrypted_filename,
+ filename->encrypted_filename_size);
+ if ((crypt_stat && (crypt_stat->flags
+ & ECRYPTFS_ENCFN_USE_MOUNT_FNEK))
+ || (mount_crypt_stat
+ && (mount_crypt_stat->flags
+ & ECRYPTFS_GLOBAL_ENCFN_USE_MOUNT_FNEK)))
+ (*encoded_name_size) =
+ (ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE
+ + encoded_name_no_prefix_size);
+ else
+ (*encoded_name_size) =
+ (ECRYPTFS_FEK_ENCRYPTED_FILENAME_PREFIX_SIZE
+ + encoded_name_no_prefix_size);
+ (*encoded_name) = kmalloc((*encoded_name_size) + 1, GFP_KERNEL);
+ if (!(*encoded_name)) {
+ printk(KERN_ERR "%s: Out of memory whilst attempting "
+ "to kzalloc [%d] bytes\n", __func__,
+ (*encoded_name_size));
+ rc = -ENOMEM;
+ kfree(filename->encrypted_filename);
+ kfree(filename);
+ goto out;
+ }
+ if ((crypt_stat && (crypt_stat->flags
+ & ECRYPTFS_ENCFN_USE_MOUNT_FNEK))
+ || (mount_crypt_stat
+ && (mount_crypt_stat->flags
+ & ECRYPTFS_GLOBAL_ENCFN_USE_MOUNT_FNEK))) {
+ memcpy((*encoded_name),
+ ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX,
+ ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE);
+ ecryptfs_encode_for_filename(
+ ((*encoded_name)
+ + ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE),
+ &encoded_name_no_prefix_size,
+ filename->encrypted_filename,
+ filename->encrypted_filename_size);
+ (*encoded_name_size) =
+ (ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE
+ + encoded_name_no_prefix_size);
+ (*encoded_name)[(*encoded_name_size)] = '\0';
+ (*encoded_name_size)++;
+ } else {
+ rc = -ENOTSUPP;
+ }
+ if (rc) {
+ printk(KERN_ERR "%s: Error attempting to encode "
+ "encrypted filename; rc = [%d]\n", __func__,
+ rc);
+ kfree((*encoded_name));
+ (*encoded_name) = NULL;
+ (*encoded_name_size) = 0;
+ }
+ kfree(filename->encrypted_filename);
+ kfree(filename);
+ } else {
+ rc = ecryptfs_copy_filename(encoded_name,
+ encoded_name_size,
+ name, name_size);
+ }
+out:
+ return rc;
+}
+
+/**
+ * ecryptfs_decode_and_decrypt_filename - converts the encoded cipher text name to decoded plaintext
+ * @plaintext_name: The plaintext name
+ * @plaintext_name_size: The plaintext name size
+ * @ecryptfs_dir_dentry: eCryptfs directory dentry
+ * @name: The filename in cipher text
+ * @name_size: The cipher text name size
+ *
+ * Decrypts and decodes the filename.
+ *
+ * Returns zero on error; non-zero otherwise
+ */
+int ecryptfs_decode_and_decrypt_filename(char **plaintext_name,
+ size_t *plaintext_name_size,
+ struct dentry *ecryptfs_dir_dentry,
+ const char *name, size_t name_size)
+{
+ char *decoded_name;
+ size_t decoded_name_size;
+ size_t packet_size;
+ int rc = 0;
+
+ if ((name_size > ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE)
+ && (strncmp(name, ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX,
+ ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE) == 0)) {
+ struct ecryptfs_mount_crypt_stat *mount_crypt_stat =
+ &ecryptfs_superblock_to_private(
+ ecryptfs_dir_dentry->d_sb)->mount_crypt_stat;
+ const char *orig_name = name;
+ size_t orig_name_size = name_size;
+
+ name += ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE;
+ name_size -= ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE;
+ rc = ecryptfs_decode_from_filename(NULL, &decoded_name_size,
+ name, name_size);
+ if (rc) {
+ printk(KERN_ERR "%s: Error attempting to decode "
+ "filename; rc = [%d]\n", __func__, rc);
+ rc = ecryptfs_copy_filename(plaintext_name,
+ plaintext_name_size,
+ orig_name, orig_name_size);
+ goto out;
+ }
+ decoded_name = kmalloc(decoded_name_size, GFP_KERNEL);
+ if (!decoded_name) {
+ printk(KERN_ERR "%s: Out of memory whilst attempting "
+ "to kmalloc [%Zd] bytes\n", __func__,
+ decoded_name_size);
+ rc = -ENOMEM;
+ goto out;
+ }
+ rc = ecryptfs_decode_from_filename(decoded_name,
+ &decoded_name_size,
+ name, name_size);
+ if (rc) {
+ printk(KERN_ERR "%s: Error attempting to decode "
+ "filename; rc = [%d]\n", __func__, rc);
+ rc = ecryptfs_copy_filename(plaintext_name,
+ plaintext_name_size,
+ orig_name, orig_name_size);
+ goto out_free;
+ }
+ rc = ecryptfs_parse_tag_70_packet(plaintext_name,
+ plaintext_name_size,
+ &packet_size,
+ mount_crypt_stat,
+ decoded_name,
+ decoded_name_size);
+ if (rc) {
+ printk(KERN_INFO "%s: Could not parse tag 70 packet "
+ "from filename; copying through filename "
+ "as-is\n", __func__);
+ rc = ecryptfs_copy_filename(plaintext_name,
+ plaintext_name_size,
+ orig_name, orig_name_size);
+ goto out_free;
+ }
+ } else {
+ rc = ecryptfs_copy_filename(plaintext_name,
+ plaintext_name_size,
+ name, name_size);
+ goto out;
+ }
+out_free:
+ kfree(decoded_name);
+out:
+ return rc;
+}
--
1.5.3.6
--
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