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-rw-r--r--fs/crypto/fname.c90
-rw-r--r--fs/crypto/fscrypt_private.h13
-rw-r--r--fs/crypto/keyinfo.c3
-rw-r--r--fs/crypto/policy.c98
4 files changed, 139 insertions, 65 deletions
diff --git a/fs/crypto/fname.c b/fs/crypto/fname.c
index 37b49894c762..d1bb02b1ee58 100644
--- a/fs/crypto/fname.c
+++ b/fs/crypto/fname.c
@@ -159,6 +159,8 @@ static int fname_decrypt(struct inode *inode,
static const char *lookup_table =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";
+#define BASE64_CHARS(nbytes) DIV_ROUND_UP((nbytes) * 4, 3)
+
/**
* digest_encode() -
*
@@ -230,11 +232,14 @@ EXPORT_SYMBOL(fscrypt_fname_encrypted_size);
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
@@ -266,6 +271,10 @@ EXPORT_SYMBOL(fscrypt_fname_free_buffer);
*
* 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,
@@ -274,7 +283,7 @@ 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] = '.';
@@ -289,20 +298,24 @@ int fscrypt_fname_disk_to_usr(struct inode *inode,
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);
@@ -336,10 +349,35 @@ int fscrypt_fname_usr_to_disk(struct inode *inode,
}
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;
@@ -373,25 +411,37 @@ int fscrypt_setup_filename(struct inode *dir, const struct qstr *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;
diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h
index e39696e64494..1e1f8a361b75 100644
--- a/fs/crypto/fscrypt_private.h
+++ b/fs/crypto/fscrypt_private.h
@@ -13,8 +13,6 @@
#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
@@ -22,10 +20,6 @@
#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
@@ -51,13 +45,6 @@ struct fscrypt_context {
#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.
diff --git a/fs/crypto/keyinfo.c b/fs/crypto/keyinfo.c
index 8cdfddce2b34..179e578b875b 100644
--- a/fs/crypto/keyinfo.c
+++ b/fs/crypto/keyinfo.c
@@ -183,9 +183,6 @@ int fscrypt_get_encryption_info(struct inode *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) ||
diff --git a/fs/crypto/policy.c b/fs/crypto/policy.c
index 4908906d54d5..210976e7a269 100644
--- a/fs/crypto/policy.c
+++ b/fs/crypto/policy.c
@@ -34,9 +34,6 @@ static int create_encryption_context_from_policy(struct inode *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);
@@ -87,8 +84,6 @@ int fscrypt_ioctl_set_policy(struct file *filp, const void __user *arg)
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
@@ -118,8 +113,7 @@ int fscrypt_ioctl_get_policy(struct file *filp, void __user *arg)
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));
@@ -143,27 +137,61 @@ int fscrypt_ioctl_get_policy(struct file *filp, void __user *arg)
}
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;
@@ -172,17 +200,32 @@ int fscrypt_has_permitted_context(struct inode *parent, struct inode *child)
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);
@@ -202,9 +245,6 @@ int fscrypt_inherit_context(struct inode *parent, struct inode *child,
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;
Copyright © 1996 – 2023 Jason A. Donenfeld. All Rights Reverse Engineered.