F: fs/fscache/
F: include/linux/fscache*.h
-FS-CRYPTO: FILE SYSTEM LEVEL ENCRYPTION SUPPORT
+FSCRYPT: FILE SYSTEM LEVEL ENCRYPTION SUPPORT
M: Theodore Y. Ts'o <tytso@mit.edu>
M: Jaegeuk Kim <jaegeuk@kernel.org>
-L: linux-fsdevel@vger.kernel.org
+L: linux-fscrypt@vger.kernel.org
+Q: https://patchwork.kernel.org/project/linux-fscrypt/list/
+T: git git://git.kernel.org/pub/scm/linux/kernel/git/tytso/fscrypt.git
S: Supported
F: fs/crypto/
F: include/linux/fscrypt*.h
static const char *lookup_table =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";
+#define BASE64_CHARS(nbytes) DIV_ROUND_UP((nbytes) * 4, 3)
+
/**
* digest_encode() -
*
int fscrypt_fname_alloc_buffer(const struct inode *inode,
u32 ilen, struct fscrypt_str *crypto_str)
{
- unsigned int olen = fscrypt_fname_encrypted_size(inode, ilen);
+ u32 olen = fscrypt_fname_encrypted_size(inode, ilen);
+ const u32 max_encoded_len =
+ max_t(u32, BASE64_CHARS(FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE),
+ 1 + BASE64_CHARS(sizeof(struct fscrypt_digested_name)));
crypto_str->len = olen;
- if (olen < FS_FNAME_CRYPTO_DIGEST_SIZE * 2)
- olen = FS_FNAME_CRYPTO_DIGEST_SIZE * 2;
+ olen = max(olen, max_encoded_len);
+
/*
* Allocated buffer can hold one more character to null-terminate the
* string
*
* The caller must have allocated sufficient memory for the @oname string.
*
+ * If the key is available, we'll decrypt the disk name; otherwise, we'll encode
+ * it for presentation. Short names are directly base64-encoded, while long
+ * names are encoded in fscrypt_digested_name format.
+ *
* Return: 0 on success, -errno on failure
*/
int fscrypt_fname_disk_to_usr(struct inode *inode,
struct fscrypt_str *oname)
{
const struct qstr qname = FSTR_TO_QSTR(iname);
- char buf[24];
+ struct fscrypt_digested_name digested_name;
if (fscrypt_is_dot_dotdot(&qname)) {
oname->name[0] = '.';
if (inode->i_crypt_info)
return fname_decrypt(inode, iname, oname);
- if (iname->len <= FS_FNAME_CRYPTO_DIGEST_SIZE) {
+ if (iname->len <= FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE) {
oname->len = digest_encode(iname->name, iname->len,
oname->name);
return 0;
}
if (hash) {
- memcpy(buf, &hash, 4);
- memcpy(buf + 4, &minor_hash, 4);
+ digested_name.hash = hash;
+ digested_name.minor_hash = minor_hash;
} else {
- memset(buf, 0, 8);
+ digested_name.hash = 0;
+ digested_name.minor_hash = 0;
}
- memcpy(buf + 8, iname->name + iname->len - 16, 16);
+ memcpy(digested_name.digest,
+ FSCRYPT_FNAME_DIGEST(iname->name, iname->len),
+ FSCRYPT_FNAME_DIGEST_SIZE);
oname->name[0] = '_';
- oname->len = 1 + digest_encode(buf, 24, oname->name + 1);
+ oname->len = 1 + digest_encode((const char *)&digested_name,
+ sizeof(digested_name), oname->name + 1);
return 0;
}
EXPORT_SYMBOL(fscrypt_fname_disk_to_usr);
}
EXPORT_SYMBOL(fscrypt_fname_usr_to_disk);
+/**
+ * fscrypt_setup_filename() - prepare to search a possibly encrypted directory
+ * @dir: the directory that will be searched
+ * @iname: the user-provided filename being searched for
+ * @lookup: 1 if we're allowed to proceed without the key because it's
+ * ->lookup() or we're finding the dir_entry for deletion; 0 if we cannot
+ * proceed without the key because we're going to create the dir_entry.
+ * @fname: the filename information to be filled in
+ *
+ * Given a user-provided filename @iname, this function sets @fname->disk_name
+ * to the name that would be stored in the on-disk directory entry, if possible.
+ * If the directory is unencrypted this is simply @iname. Else, if we have the
+ * directory's encryption key, then @iname is the plaintext, so we encrypt it to
+ * get the disk_name.
+ *
+ * Else, for keyless @lookup operations, @iname is the presented ciphertext, so
+ * we decode it to get either the ciphertext disk_name (for short names) or the
+ * fscrypt_digested_name (for long names). Non-@lookup operations will be
+ * impossible in this case, so we fail them with ENOKEY.
+ *
+ * If successful, fscrypt_free_filename() must be called later to clean up.
+ *
+ * Return: 0 on success, -errno on failure
+ */
int fscrypt_setup_filename(struct inode *dir, const struct qstr *iname,
int lookup, struct fscrypt_name *fname)
{
- int ret = 0, bigname = 0;
+ int ret;
+ int digested;
memset(fname, 0, sizeof(struct fscrypt_name));
fname->usr_fname = iname;
* We don't have the key and we are doing a lookup; decode the
* user-supplied name
*/
- if (iname->name[0] == '_')
- bigname = 1;
- if ((bigname && (iname->len != 33)) || (!bigname && (iname->len > 43)))
- return -ENOENT;
+ if (iname->name[0] == '_') {
+ if (iname->len !=
+ 1 + BASE64_CHARS(sizeof(struct fscrypt_digested_name)))
+ return -ENOENT;
+ digested = 1;
+ } else {
+ if (iname->len >
+ BASE64_CHARS(FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE))
+ return -ENOENT;
+ digested = 0;
+ }
- fname->crypto_buf.name = kmalloc(32, GFP_KERNEL);
+ fname->crypto_buf.name =
+ kmalloc(max_t(size_t, FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE,
+ sizeof(struct fscrypt_digested_name)),
+ GFP_KERNEL);
if (fname->crypto_buf.name == NULL)
return -ENOMEM;
- ret = digest_decode(iname->name + bigname, iname->len - bigname,
+ ret = digest_decode(iname->name + digested, iname->len - digested,
fname->crypto_buf.name);
if (ret < 0) {
ret = -ENOENT;
goto errout;
}
fname->crypto_buf.len = ret;
- if (bigname) {
- memcpy(&fname->hash, fname->crypto_buf.name, 4);
- memcpy(&fname->minor_hash, fname->crypto_buf.name + 4, 4);
+ if (digested) {
+ const struct fscrypt_digested_name *n =
+ (const void *)fname->crypto_buf.name;
+ fname->hash = n->hash;
+ fname->minor_hash = n->minor_hash;
} else {
fname->disk_name.name = fname->crypto_buf.name;
fname->disk_name.len = fname->crypto_buf.len;
#include <linux/fscrypt_supp.h>
-#define FS_FNAME_CRYPTO_DIGEST_SIZE 32
-
/* Encryption parameters */
#define FS_XTS_TWEAK_SIZE 16
#define FS_AES_128_ECB_KEY_SIZE 16
#define FS_AES_256_CBC_KEY_SIZE 32
#define FS_AES_256_CTS_KEY_SIZE 32
#define FS_AES_256_XTS_KEY_SIZE 64
-#define FS_MAX_KEY_SIZE 64
-
-#define FS_KEY_DESC_PREFIX "fscrypt:"
-#define FS_KEY_DESC_PREFIX_SIZE 8
#define FS_KEY_DERIVATION_NONCE_SIZE 16
#define FS_ENCRYPTION_CONTEXT_FORMAT_V1 1
-/* This is passed in from userspace into the kernel keyring */
-struct fscrypt_key {
- u32 mode;
- u8 raw[FS_MAX_KEY_SIZE];
- u32 size;
-} __packed;
-
/*
* A pointer to this structure is stored in the file system's in-core
* representation of an inode.
if (res)
return res;
- if (!inode->i_sb->s_cop->get_context)
- return -EOPNOTSUPP;
-
res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
if (res < 0) {
if (!fscrypt_dummy_context_enabled(inode) ||
{
struct fscrypt_context ctx;
- if (!inode->i_sb->s_cop->set_context)
- return -EOPNOTSUPP;
-
ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1;
memcpy(ctx.master_key_descriptor, policy->master_key_descriptor,
FS_KEY_DESCRIPTOR_SIZE);
if (ret == -ENODATA) {
if (!S_ISDIR(inode->i_mode))
ret = -ENOTDIR;
- else if (!inode->i_sb->s_cop->empty_dir)
- ret = -EOPNOTSUPP;
else if (!inode->i_sb->s_cop->empty_dir(inode))
ret = -ENOTEMPTY;
else
struct fscrypt_policy policy;
int res;
- if (!inode->i_sb->s_cop->get_context ||
- !inode->i_sb->s_cop->is_encrypted(inode))
+ if (!inode->i_sb->s_cop->is_encrypted(inode))
return -ENODATA;
res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
}
EXPORT_SYMBOL(fscrypt_ioctl_get_policy);
+/**
+ * fscrypt_has_permitted_context() - is a file's encryption policy permitted
+ * within its directory?
+ *
+ * @parent: inode for parent directory
+ * @child: inode for file being looked up, opened, or linked into @parent
+ *
+ * Filesystems must call this before permitting access to an inode in a
+ * situation where the parent directory is encrypted (either before allowing
+ * ->lookup() to succeed, or for a regular file before allowing it to be opened)
+ * and before any operation that involves linking an inode into an encrypted
+ * directory, including link, rename, and cross rename. It enforces the
+ * constraint that within a given encrypted directory tree, all files use the
+ * same encryption policy. The pre-access check is needed to detect potentially
+ * malicious offline violations of this constraint, while the link and rename
+ * checks are needed to prevent online violations of this constraint.
+ *
+ * Return: 1 if permitted, 0 if forbidden. If forbidden, the caller must fail
+ * the filesystem operation with EPERM.
+ */
int fscrypt_has_permitted_context(struct inode *parent, struct inode *child)
{
- struct fscrypt_info *parent_ci, *child_ci;
+ const struct fscrypt_operations *cops = parent->i_sb->s_cop;
+ const struct fscrypt_info *parent_ci, *child_ci;
+ struct fscrypt_context parent_ctx, child_ctx;
int res;
- if ((parent == NULL) || (child == NULL)) {
- printk(KERN_ERR "parent %p child %p\n", parent, child);
- BUG_ON(1);
- }
-
/* No restrictions on file types which are never encrypted */
if (!S_ISREG(child->i_mode) && !S_ISDIR(child->i_mode) &&
!S_ISLNK(child->i_mode))
return 1;
- /* no restrictions if the parent directory is not encrypted */
- if (!parent->i_sb->s_cop->is_encrypted(parent))
+ /* No restrictions if the parent directory is unencrypted */
+ if (!cops->is_encrypted(parent))
return 1;
- /* if the child directory is not encrypted, this is always a problem */
- if (!parent->i_sb->s_cop->is_encrypted(child))
+
+ /* Encrypted directories must not contain unencrypted files */
+ if (!cops->is_encrypted(child))
return 0;
+
+ /*
+ * Both parent and child are encrypted, so verify they use the same
+ * encryption policy. Compare the fscrypt_info structs if the keys are
+ * available, otherwise retrieve and compare the fscrypt_contexts.
+ *
+ * Note that the fscrypt_context retrieval will be required frequently
+ * when accessing an encrypted directory tree without the key.
+ * Performance-wise this is not a big deal because we already don't
+ * really optimize for file access without the key (to the extent that
+ * such access is even possible), given that any attempted access
+ * already causes a fscrypt_context retrieval and keyring search.
+ *
+ * In any case, if an unexpected error occurs, fall back to "forbidden".
+ */
+
res = fscrypt_get_encryption_info(parent);
if (res)
return 0;
return 0;
parent_ci = parent->i_crypt_info;
child_ci = child->i_crypt_info;
- if (!parent_ci && !child_ci)
- return 1;
- if (!parent_ci || !child_ci)
+
+ if (parent_ci && child_ci) {
+ return memcmp(parent_ci->ci_master_key, child_ci->ci_master_key,
+ FS_KEY_DESCRIPTOR_SIZE) == 0 &&
+ (parent_ci->ci_data_mode == child_ci->ci_data_mode) &&
+ (parent_ci->ci_filename_mode ==
+ child_ci->ci_filename_mode) &&
+ (parent_ci->ci_flags == child_ci->ci_flags);
+ }
+
+ res = cops->get_context(parent, &parent_ctx, sizeof(parent_ctx));
+ if (res != sizeof(parent_ctx))
return 0;
- return (memcmp(parent_ci->ci_master_key,
- child_ci->ci_master_key,
- FS_KEY_DESCRIPTOR_SIZE) == 0 &&
- (parent_ci->ci_data_mode == child_ci->ci_data_mode) &&
- (parent_ci->ci_filename_mode == child_ci->ci_filename_mode) &&
- (parent_ci->ci_flags == child_ci->ci_flags));
+ res = cops->get_context(child, &child_ctx, sizeof(child_ctx));
+ if (res != sizeof(child_ctx))
+ return 0;
+
+ return memcmp(parent_ctx.master_key_descriptor,
+ child_ctx.master_key_descriptor,
+ FS_KEY_DESCRIPTOR_SIZE) == 0 &&
+ (parent_ctx.contents_encryption_mode ==
+ child_ctx.contents_encryption_mode) &&
+ (parent_ctx.filenames_encryption_mode ==
+ child_ctx.filenames_encryption_mode) &&
+ (parent_ctx.flags == child_ctx.flags);
}
EXPORT_SYMBOL(fscrypt_has_permitted_context);
struct fscrypt_info *ci;
int res;
- if (!parent->i_sb->s_cop->set_context)
- return -EOPNOTSUPP;
-
res = fscrypt_get_encryption_info(parent);
if (res < 0)
return res;
}
/*
- * NOTE! unlike strncmp, ext4_match returns 1 for success, 0 for failure.
+ * Test whether a directory entry matches the filename being searched for.
*
- * `len <= EXT4_NAME_LEN' is guaranteed by caller.
- * `de != NULL' is guaranteed by caller.
+ * Return: %true if the directory entry matches, otherwise %false.
*/
-static inline int ext4_match(struct ext4_filename *fname,
- struct ext4_dir_entry_2 *de)
+static inline bool ext4_match(const struct ext4_filename *fname,
+ const struct ext4_dir_entry_2 *de)
{
- const void *name = fname_name(fname);
- u32 len = fname_len(fname);
+ struct fscrypt_name f;
if (!de->inode)
- return 0;
+ return false;
+ f.usr_fname = fname->usr_fname;
+ f.disk_name = fname->disk_name;
#ifdef CONFIG_EXT4_FS_ENCRYPTION
- if (unlikely(!name)) {
- if (fname->usr_fname->name[0] == '_') {
- int ret;
- if (de->name_len < 16)
- return 0;
- ret = memcmp(de->name + de->name_len - 16,
- fname->crypto_buf.name + 8, 16);
- return (ret == 0) ? 1 : 0;
- }
- name = fname->crypto_buf.name;
- len = fname->crypto_buf.len;
- }
+ f.crypto_buf = fname->crypto_buf;
#endif
- if (de->name_len != len)
- return 0;
- return (memcmp(de->name, name, len) == 0) ? 1 : 0;
+ return fscrypt_match_name(&f, de->name, de->name_len);
}
/*
struct ext4_dir_entry_2 * de;
char * dlimit;
int de_len;
- int res;
de = (struct ext4_dir_entry_2 *)search_buf;
dlimit = search_buf + buf_size;
while ((char *) de < dlimit) {
/* this code is executed quadratically often */
/* do minimal checking `by hand' */
- if ((char *) de + de->name_len <= dlimit) {
- res = ext4_match(fname, de);
- if (res < 0) {
- res = -1;
- goto return_result;
- }
- if (res > 0) {
- /* found a match - just to be sure, do
- * a full check */
- if (ext4_check_dir_entry(dir, NULL, de, bh,
- bh->b_data,
- bh->b_size, offset)) {
- res = -1;
- goto return_result;
- }
- *res_dir = de;
- res = 1;
- goto return_result;
- }
-
+ if ((char *) de + de->name_len <= dlimit &&
+ ext4_match(fname, de)) {
+ /* found a match - just to be sure, do
+ * a full check */
+ if (ext4_check_dir_entry(dir, NULL, de, bh, bh->b_data,
+ bh->b_size, offset))
+ return -1;
+ *res_dir = de;
+ return 1;
}
/* prevent looping on a bad block */
de_len = ext4_rec_len_from_disk(de->rec_len,
dir->i_sb->s_blocksize);
- if (de_len <= 0) {
- res = -1;
- goto return_result;
- }
+ if (de_len <= 0)
+ return -1;
offset += de_len;
de = (struct ext4_dir_entry_2 *) ((char *) de + de_len);
}
-
- res = 0;
-return_result:
- return res;
+ return 0;
}
static int is_dx_internal_node(struct inode *dir, ext4_lblk_t block,
if (!IS_ERR(inode) && ext4_encrypted_inode(dir) &&
(S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode)) &&
!fscrypt_has_permitted_context(dir, inode)) {
- int nokey = ext4_encrypted_inode(inode) &&
- !fscrypt_has_encryption_key(inode);
- if (nokey) {
- iput(inode);
- return ERR_PTR(-ENOKEY);
- }
ext4_warning(inode->i_sb,
"Inconsistent encryption contexts: %lu/%lu",
- (unsigned long) dir->i_ino,
- (unsigned long) inode->i_ino);
+ dir->i_ino, inode->i_ino);
iput(inode);
return ERR_PTR(-EPERM);
}
int nlen, rlen;
unsigned int offset = 0;
char *top;
- int res;
de = (struct ext4_dir_entry_2 *)buf;
top = buf + buf_size - reclen;
while ((char *) de <= top) {
if (ext4_check_dir_entry(dir, NULL, de, bh,
- buf, buf_size, offset)) {
- res = -EFSCORRUPTED;
- goto return_result;
- }
- /* Provide crypto context and crypto buffer to ext4 match */
- res = ext4_match(fname, de);
- if (res < 0)
- goto return_result;
- if (res > 0) {
- res = -EEXIST;
- goto return_result;
- }
+ buf, buf_size, offset))
+ return -EFSCORRUPTED;
+ if (ext4_match(fname, de))
+ return -EEXIST;
nlen = EXT4_DIR_REC_LEN(de->name_len);
rlen = ext4_rec_len_from_disk(de->rec_len, buf_size);
if ((de->inode ? rlen - nlen : rlen) >= reclen)
de = (struct ext4_dir_entry_2 *)((char *)de + rlen);
offset += rlen;
}
-
if ((char *) de > top)
- res = -ENOSPC;
- else {
- *dest_de = de;
- res = 0;
- }
-return_result:
- return res;
+ return -ENOSPC;
+
+ *dest_de = de;
+ return 0;
}
void ext4_insert_dentry(struct inode *inode,
struct f2fs_dir_entry *de;
unsigned long bit_pos = 0;
int max_len = 0;
- struct fscrypt_str de_name = FSTR_INIT(NULL, 0);
- struct fscrypt_str *name = &fname->disk_name;
if (max_slots)
*max_slots = 0;
continue;
}
- /* encrypted case */
- de_name.name = d->filename[bit_pos];
- de_name.len = le16_to_cpu(de->name_len);
-
- /* show encrypted name */
- if (fname->hash) {
- if (de->hash_code == cpu_to_le32(fname->hash))
- goto found;
- } else if (de_name.len == name->len &&
- de->hash_code == namehash &&
- !memcmp(de_name.name, name->name, name->len))
+ if (de->hash_code == namehash &&
+ fscrypt_match_name(fname, d->filename[bit_pos],
+ le16_to_cpu(de->name_len)))
goto found;
if (max_slots && max_len > *max_slots)
struct f2fs_dir_entry *de = NULL;
bool room = false;
int max_slots;
- f2fs_hash_t namehash;
-
- if(fname->hash)
- namehash = cpu_to_le32(fname->hash);
- else
- namehash = f2fs_dentry_hash(&name);
+ f2fs_hash_t namehash = f2fs_dentry_hash(&name, fname);
nbucket = dir_buckets(level, F2FS_I(dir)->i_dir_level);
nblock = bucket_blocks(level);
level = 0;
slots = GET_DENTRY_SLOTS(new_name->len);
- dentry_hash = f2fs_dentry_hash(new_name);
+ dentry_hash = f2fs_dentry_hash(new_name, NULL);
current_depth = F2FS_I(dir)->i_current_depth;
if (F2FS_I(dir)->chash == dentry_hash) {
/*
* hash.c
*/
-f2fs_hash_t f2fs_dentry_hash(const struct qstr *name_info);
+f2fs_hash_t f2fs_dentry_hash(const struct qstr *name_info,
+ struct fscrypt_name *fname);
/*
* node.c
*buf++ = pad;
}
-f2fs_hash_t f2fs_dentry_hash(const struct qstr *name_info)
+f2fs_hash_t f2fs_dentry_hash(const struct qstr *name_info,
+ struct fscrypt_name *fname)
{
__u32 hash;
f2fs_hash_t f2fs_hash;
const unsigned char *name = name_info->name;
size_t len = name_info->len;
+ /* encrypted bigname case */
+ if (fname && !fname->disk_name.name)
+ return cpu_to_le32(fname->hash);
+
if (is_dot_dotdot(name_info))
return 0;
return NULL;
}
- namehash = f2fs_dentry_hash(&name);
+ namehash = f2fs_dentry_hash(&name, fname);
inline_dentry = inline_data_addr(ipage);
f2fs_wait_on_page_writeback(ipage, NODE, true);
- name_hash = f2fs_dentry_hash(new_name);
+ name_hash = f2fs_dentry_hash(new_name, NULL);
make_dentry_ptr(NULL, &d, (void *)dentry_blk, 2);
f2fs_update_dentry(ino, mode, &d, new_name, name_hash, bit_pos);
if (f2fs_encrypted_inode(dir) &&
(S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode)) &&
!fscrypt_has_permitted_context(dir, inode)) {
- bool nokey = f2fs_encrypted_inode(inode) &&
- !fscrypt_has_encryption_key(inode);
- err = nokey ? -ENOKEY : -EPERM;
+ f2fs_msg(inode->i_sb, KERN_WARNING,
+ "Inconsistent encryption contexts: %lu/%lu",
+ dir->i_ino, inode->i_ino);
+ err = -EPERM;
goto err_out;
}
return d_splice_alias(inode, dentry);
goto out_dent;
}
+ if (ubifs_crypt_is_encrypted(dir) &&
+ (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode)) &&
+ !fscrypt_has_permitted_context(dir, inode)) {
+ ubifs_warn(c, "Inconsistent encryption contexts: %lu/%lu",
+ dir->i_ino, inode->i_ino);
+ err = -EPERM;
+ goto out_inode;
+ }
+
done:
kfree(dent);
fscrypt_free_filename(&nm);
d_add(dentry, inode);
return NULL;
+out_inode:
+ iput(inode);
out_dent:
kfree(dent);
out_fname:
char encrypted_path[1];
} __packed;
-/**
- * This function is used to calculate the disk space required to
- * store a filename of length l in encrypted symlink format.
- */
-static inline u32 fscrypt_symlink_data_len(u32 l)
-{
- if (l < FS_CRYPTO_BLOCK_SIZE)
- l = FS_CRYPTO_BLOCK_SIZE;
- return (l + sizeof(struct fscrypt_symlink_data) - 1);
-}
-
struct fscrypt_str {
unsigned char *name;
u32 len;
return -EOPNOTSUPP;
}
+static inline bool fscrypt_match_name(const struct fscrypt_name *fname,
+ const u8 *de_name, u32 de_name_len)
+{
+ /* Encryption support disabled; use standard comparison */
+ if (de_name_len != fname->disk_name.len)
+ return false;
+ return !memcmp(de_name, fname->disk_name.name, fname->disk_name.len);
+}
+
/* bio.c */
static inline void fscrypt_decrypt_bio_pages(struct fscrypt_ctx *ctx,
struct bio *bio)
extern int fscrypt_fname_usr_to_disk(struct inode *, const struct qstr *,
struct fscrypt_str *);
+#define FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE 32
+
+/* Extracts the second-to-last ciphertext block; see explanation below */
+#define FSCRYPT_FNAME_DIGEST(name, len) \
+ ((name) + round_down((len) - FS_CRYPTO_BLOCK_SIZE - 1, \
+ FS_CRYPTO_BLOCK_SIZE))
+
+#define FSCRYPT_FNAME_DIGEST_SIZE FS_CRYPTO_BLOCK_SIZE
+
+/**
+ * fscrypt_digested_name - alternate identifier for an on-disk filename
+ *
+ * When userspace lists an encrypted directory without access to the key,
+ * filenames whose ciphertext is longer than FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE
+ * bytes are shown in this abbreviated form (base64-encoded) rather than as the
+ * full ciphertext (base64-encoded). This is necessary to allow supporting
+ * filenames up to NAME_MAX bytes, since base64 encoding expands the length.
+ *
+ * To make it possible for filesystems to still find the correct directory entry
+ * despite not knowing the full on-disk name, we encode any filesystem-specific
+ * 'hash' and/or 'minor_hash' which the filesystem may need for its lookups,
+ * followed by the second-to-last ciphertext block of the filename. Due to the
+ * use of the CBC-CTS encryption mode, the second-to-last ciphertext block
+ * depends on the full plaintext. (Note that ciphertext stealing causes the
+ * last two blocks to appear "flipped".) This makes accidental collisions very
+ * unlikely: just a 1 in 2^128 chance for two filenames to collide even if they
+ * share the same filesystem-specific hashes.
+ *
+ * However, this scheme isn't immune to intentional collisions, which can be
+ * created by anyone able to create arbitrary plaintext filenames and view them
+ * without the key. Making the "digest" be a real cryptographic hash like
+ * SHA-256 over the full ciphertext would prevent this, although it would be
+ * less efficient and harder to implement, especially since the filesystem would
+ * need to calculate it for each directory entry examined during a search.
+ */
+struct fscrypt_digested_name {
+ u32 hash;
+ u32 minor_hash;
+ u8 digest[FSCRYPT_FNAME_DIGEST_SIZE];
+};
+
+/**
+ * fscrypt_match_name() - test whether the given name matches a directory entry
+ * @fname: the name being searched for
+ * @de_name: the name from the directory entry
+ * @de_name_len: the length of @de_name in bytes
+ *
+ * Normally @fname->disk_name will be set, and in that case we simply compare
+ * that to the name stored in the directory entry. The only exception is that
+ * if we don't have the key for an encrypted directory and a filename in it is
+ * very long, then we won't have the full disk_name and we'll instead need to
+ * match against the fscrypt_digested_name.
+ *
+ * Return: %true if the name matches, otherwise %false.
+ */
+static inline bool fscrypt_match_name(const struct fscrypt_name *fname,
+ const u8 *de_name, u32 de_name_len)
+{
+ if (unlikely(!fname->disk_name.name)) {
+ const struct fscrypt_digested_name *n =
+ (const void *)fname->crypto_buf.name;
+ if (WARN_ON_ONCE(fname->usr_fname->name[0] != '_'))
+ return false;
+ if (de_name_len <= FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE)
+ return false;
+ return !memcmp(FSCRYPT_FNAME_DIGEST(de_name, de_name_len),
+ n->digest, FSCRYPT_FNAME_DIGEST_SIZE);
+ }
+
+ if (de_name_len != fname->disk_name.len)
+ return false;
+ return !memcmp(de_name, fname->disk_name.name, fname->disk_name.len);
+}
+
/* bio.c */
extern void fscrypt_decrypt_bio_pages(struct fscrypt_ctx *, struct bio *);
extern void fscrypt_pullback_bio_page(struct page **, bool);
__u8 filenames_encryption_mode;
__u8 flags;
__u8 master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE];
-} __packed;
+};
#define FS_IOC_SET_ENCRYPTION_POLICY _IOR('f', 19, struct fscrypt_policy)
#define FS_IOC_GET_ENCRYPTION_PWSALT _IOW('f', 20, __u8[16])
#define FS_IOC_GET_ENCRYPTION_POLICY _IOW('f', 21, struct fscrypt_policy)
+/* Parameters for passing an encryption key into the kernel keyring */
+#define FS_KEY_DESC_PREFIX "fscrypt:"
+#define FS_KEY_DESC_PREFIX_SIZE 8
+
+/* Structure that userspace passes to the kernel keyring */
+#define FS_MAX_KEY_SIZE 64
+
+struct fscrypt_key {
+ __u32 mode;
+ __u8 raw[FS_MAX_KEY_SIZE];
+ __u32 size;
+};
+
/*
* Inode flags (FS_IOC_GETFLAGS / FS_IOC_SETFLAGS)
*
git.samba.org / sfrench / cifs-2.6.git / commitdiff