diff options
| -rw-r--r-- | Documentation/filesystems/fsverity.rst | 76 | ||||
| -rw-r--r-- | fs/ext4/ioctl.c | 7 | ||||
| -rw-r--r-- | fs/f2fs/file.c | 11 | ||||
| -rw-r--r-- | fs/verity/Makefile | 1 | ||||
| -rw-r--r-- | fs/verity/fsverity_private.h | 13 | ||||
| -rw-r--r-- | fs/verity/open.c | 133 | ||||
| -rw-r--r-- | fs/verity/read_metadata.c | 195 | ||||
| -rw-r--r-- | fs/verity/signature.c | 20 | ||||
| -rw-r--r-- | include/linux/fsverity.h | 12 | ||||
| -rw-r--r-- | include/uapi/linux/fsverity.h | 14 |
10 files changed, 417 insertions, 65 deletions
diff --git a/Documentation/filesystems/fsverity.rst b/Documentation/filesystems/fsverity.rst index e0204a23e997..1d831e3cbcb3 100644 --- a/Documentation/filesystems/fsverity.rst +++ b/Documentation/filesystems/fsverity.rst @@ -217,6 +217,82 @@ FS_IOC_MEASURE_VERITY can fail with the following errors: - ``EOVERFLOW``: the digest is longer than the specified ``digest_size`` bytes. Try providing a larger buffer. +FS_IOC_READ_VERITY_METADATA +--------------------------- + +The FS_IOC_READ_VERITY_METADATA ioctl reads verity metadata from a +verity file. This ioctl is available since Linux v5.12. + +This ioctl allows writing a server program that takes a verity file +and serves it to a client program, such that the client can do its own +fs-verity compatible verification of the file. This only makes sense +if the client doesn't trust the server and if the server needs to +provide the storage for the client. + +This is a fairly specialized use case, and most fs-verity users won't +need this ioctl. + +This ioctl takes in a pointer to the following structure:: + + #define FS_VERITY_METADATA_TYPE_MERKLE_TREE 1 + #define FS_VERITY_METADATA_TYPE_DESCRIPTOR 2 + #define FS_VERITY_METADATA_TYPE_SIGNATURE 3 + + struct fsverity_read_metadata_arg { + __u64 metadata_type; + __u64 offset; + __u64 length; + __u64 buf_ptr; + __u64 __reserved; + }; + +``metadata_type`` specifies the type of metadata to read: + +- ``FS_VERITY_METADATA_TYPE_MERKLE_TREE`` reads the blocks of the + Merkle tree. The blocks are returned in order from the root level + to the leaf level. Within each level, the blocks are returned in + the same order that their hashes are themselves hashed. + See `Merkle tree`_ for more information. + +- ``FS_VERITY_METADATA_TYPE_DESCRIPTOR`` reads the fs-verity + descriptor. See `fs-verity descriptor`_. + +- ``FS_VERITY_METADATA_TYPE_SIGNATURE`` reads the signature which was + passed to FS_IOC_ENABLE_VERITY, if any. See `Built-in signature + verification`_. + +The semantics are similar to those of ``pread()``. ``offset`` +specifies the offset in bytes into the metadata item to read from, and +``length`` specifies the maximum number of bytes to read from the +metadata item. ``buf_ptr`` is the pointer to the buffer to read into, +cast to a 64-bit integer. ``__reserved`` must be 0. On success, the +number of bytes read is returned. 0 is returned at the end of the +metadata item. The returned length may be less than ``length``, for +example if the ioctl is interrupted. + +The metadata returned by FS_IOC_READ_VERITY_METADATA isn't guaranteed +to be authenticated against the file digest that would be returned by +`FS_IOC_MEASURE_VERITY`_, as the metadata is expected to be used to +implement fs-verity compatible verification anyway (though absent a +malicious disk, the metadata will indeed match). E.g. to implement +this ioctl, the filesystem is allowed to just read the Merkle tree +blocks from disk without actually verifying the path to the root node. + +FS_IOC_READ_VERITY_METADATA can fail with the following errors: + +- ``EFAULT``: the caller provided inaccessible memory +- ``EINTR``: the ioctl was interrupted before any data was read +- ``EINVAL``: reserved fields were set, or ``offset + length`` + overflowed +- ``ENODATA``: the file is not a verity file, or + FS_VERITY_METADATA_TYPE_SIGNATURE was requested but the file doesn't + have a built-in signature +- ``ENOTTY``: this type of filesystem does not implement fs-verity, or + this ioctl is not yet implemented on it +- ``EOPNOTSUPP``: the kernel was not configured with fs-verity + support, or the filesystem superblock has not had the 'verity' + feature enabled on it. (See `Filesystem support`_.) + FS_IOC_GETFLAGS --------------- diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c index d9665d2f82db..713b1ae44c1a 100644 --- a/fs/ext4/ioctl.c +++ b/fs/ext4/ioctl.c @@ -1309,6 +1309,12 @@ out: return -EOPNOTSUPP; return fsverity_ioctl_measure(filp, (void __user *)arg); + case FS_IOC_READ_VERITY_METADATA: + if (!ext4_has_feature_verity(sb)) + return -EOPNOTSUPP; + return fsverity_ioctl_read_metadata(filp, + (const void __user *)arg); + default: return -ENOTTY; } @@ -1391,6 +1397,7 @@ long ext4_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg) case FS_IOC_GETFSMAP: case FS_IOC_ENABLE_VERITY: case FS_IOC_MEASURE_VERITY: + case FS_IOC_READ_VERITY_METADATA: case EXT4_IOC_CLEAR_ES_CACHE: case EXT4_IOC_GETSTATE: case EXT4_IOC_GET_ES_CACHE: diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c index 8e53f8898688..471a6ff0c937 100644 --- a/fs/f2fs/file.c +++ b/fs/f2fs/file.c @@ -3374,6 +3374,14 @@ static int f2fs_ioc_measure_verity(struct file *filp, unsigned long arg) return fsverity_ioctl_measure(filp, (void __user *)arg); } +static int f2fs_ioc_read_verity_metadata(struct file *filp, unsigned long arg) +{ + if (!f2fs_sb_has_verity(F2FS_I_SB(file_inode(filp)))) + return -EOPNOTSUPP; + + return fsverity_ioctl_read_metadata(filp, (const void __user *)arg); +} + static int f2fs_ioc_getfslabel(struct file *filp, unsigned long arg) { struct inode *inode = file_inode(filp); @@ -4291,6 +4299,8 @@ static long __f2fs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) return f2fs_ioc_enable_verity(filp, arg); case FS_IOC_MEASURE_VERITY: return f2fs_ioc_measure_verity(filp, arg); + case FS_IOC_READ_VERITY_METADATA: + return f2fs_ioc_read_verity_metadata(filp, arg); case FS_IOC_GETFSLABEL: return f2fs_ioc_getfslabel(filp, arg); case FS_IOC_SETFSLABEL: @@ -4548,6 +4558,7 @@ long f2fs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg) case F2FS_IOC_RESIZE_FS: case FS_IOC_ENABLE_VERITY: case FS_IOC_MEASURE_VERITY: + case FS_IOC_READ_VERITY_METADATA: case FS_IOC_GETFSLABEL: case FS_IOC_SETFSLABEL: case F2FS_IOC_GET_COMPRESS_BLOCKS: diff --git a/fs/verity/Makefile b/fs/verity/Makefile index 570e9136334d..435559a4fa9e 100644 --- a/fs/verity/Makefile +++ b/fs/verity/Makefile @@ -5,6 +5,7 @@ obj-$(CONFIG_FS_VERITY) += enable.o \ init.o \ measure.o \ open.o \ + read_metadata.o \ verify.o obj-$(CONFIG_FS_VERITY_BUILTIN_SIGNATURES) += signature.o diff --git a/fs/verity/fsverity_private.h b/fs/verity/fsverity_private.h index 6413d28664d6..a7920434bae5 100644 --- a/fs/verity/fsverity_private.h +++ b/fs/verity/fsverity_private.h @@ -122,12 +122,17 @@ int fsverity_init_merkle_tree_params(struct merkle_tree_params *params, const u8 *salt, size_t salt_size); struct fsverity_info *fsverity_create_info(const struct inode *inode, - void *desc, size_t desc_size); + struct fsverity_descriptor *desc, + size_t desc_size); void fsverity_set_info(struct inode *inode, struct fsverity_info *vi); void fsverity_free_info(struct fsverity_info *vi); +int fsverity_get_descriptor(struct inode *inode, + struct fsverity_descriptor **desc_ret, + size_t *desc_size_ret); + int __init fsverity_init_info_cache(void); void __init fsverity_exit_info_cache(void); @@ -135,15 +140,13 @@ void __init fsverity_exit_info_cache(void); #ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES int fsverity_verify_signature(const struct fsverity_info *vi, - const struct fsverity_descriptor *desc, - size_t desc_size); + const u8 *signature, size_t sig_size); int __init fsverity_init_signature(void); #else /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */ static inline int fsverity_verify_signature(const struct fsverity_info *vi, - const struct fsverity_descriptor *desc, - size_t desc_size) + const u8 *signature, size_t sig_size) { return 0; } diff --git a/fs/verity/open.c b/fs/verity/open.c index 228d0eca3e2e..60ff8af7219f 100644 --- a/fs/verity/open.c +++ b/fs/verity/open.c @@ -142,45 +142,17 @@ static int compute_file_digest(struct fsverity_hash_alg *hash_alg, } /* - * Validate the given fsverity_descriptor and create a new fsverity_info from - * it. The signature (if present) is also checked. + * Create a new fsverity_info from the given fsverity_descriptor (with optional + * appended signature), and check the signature if present. The + * fsverity_descriptor must have already undergone basic validation. */ struct fsverity_info *fsverity_create_info(const struct inode *inode, - void *_desc, size_t desc_size) + struct fsverity_descriptor *desc, + size_t desc_size) { - struct fsverity_descriptor *desc = _desc; struct fsverity_info *vi; int err; - if (desc_size < sizeof(*desc)) { - fsverity_err(inode, "Unrecognized descriptor size: %zu bytes", - desc_size); - return ERR_PTR(-EINVAL); - } - - if (desc->version != 1) { - fsverity_err(inode, "Unrecognized descriptor version: %u", - desc->version); - return ERR_PTR(-EINVAL); - } - - if (memchr_inv(desc->__reserved, 0, sizeof(desc->__reserved))) { - fsverity_err(inode, "Reserved bits set in descriptor"); - return ERR_PTR(-EINVAL); - } - - if (desc->salt_size > sizeof(desc->salt)) { - fsverity_err(inode, "Invalid salt_size: %u", desc->salt_size); - return ERR_PTR(-EINVAL); - } - - if (le64_to_cpu(desc->data_size) != inode->i_size) { - fsverity_err(inode, - "Wrong data_size: %llu (desc) != %lld (inode)", - le64_to_cpu(desc->data_size), inode->i_size); - return ERR_PTR(-EINVAL); - } - vi = kmem_cache_zalloc(fsverity_info_cachep, GFP_KERNEL); if (!vi) return ERR_PTR(-ENOMEM); @@ -209,7 +181,8 @@ struct fsverity_info *fsverity_create_info(const struct inode *inode, vi->tree_params.hash_alg->name, vi->tree_params.digest_size, vi->file_digest); - err = fsverity_verify_signature(vi, desc, desc_size); + err = fsverity_verify_signature(vi, desc->signature, + le32_to_cpu(desc->sig_size)); out: if (err) { fsverity_free_info(vi); @@ -245,15 +218,57 @@ void fsverity_free_info(struct fsverity_info *vi) kmem_cache_free(fsverity_info_cachep, vi); } -/* Ensure the inode has an ->i_verity_info */ -static int ensure_verity_info(struct inode *inode) +static bool validate_fsverity_descriptor(struct inode *inode, + const struct fsverity_descriptor *desc, + size_t desc_size) { - struct fsverity_info *vi = fsverity_get_info(inode); - struct fsverity_descriptor *desc; - int res; + if (desc_size < sizeof(*desc)) { + fsverity_err(inode, "Unrecognized descriptor size: %zu bytes", + desc_size); + return false; + } - if (vi) - return 0; + if (desc->version != 1) { + fsverity_err(inode, "Unrecognized descriptor version: %u", + desc->version); + return false; + } + + if (memchr_inv(desc->__reserved, 0, sizeof(desc->__reserved))) { + fsverity_err(inode, "Reserved bits set in descriptor"); + return false; + } + + if (desc->salt_size > sizeof(desc->salt)) { + fsverity_err(inode, "Invalid salt_size: %u", desc->salt_size); + return false; + } + + if (le64_to_cpu(desc->data_size) != inode->i_size) { + fsverity_err(inode, + "Wrong data_size: %llu (desc) != %lld (inode)", + le64_to_cpu(desc->data_size), inode->i_size); + return false; + } + + if (le32_to_cpu(desc->sig_size) > desc_size - sizeof(*desc)) { + fsverity_err(inode, "Signature overflows verity descriptor"); + return false; + } + + return true; +} + +/* + * Read the inode's fsverity_descriptor (with optional appended signature) from + * the filesystem, and do basic validation of it. + */ +int fsverity_get_descriptor(struct inode *inode, + struct fsverity_descriptor **desc_ret, + size_t *desc_size_ret) +{ + int res; + struct fsverity_descriptor *desc; res = inode->i_sb->s_vop->get_verity_descriptor(inode, NULL, 0); if (res < 0) { @@ -272,20 +287,46 @@ static int ensure_verity_info(struct inode *inode) res = inode->i_sb->s_vop->get_verity_descriptor(inode, desc, res); if (res < 0) { fsverity_err(inode, "Error %d reading verity descriptor", res); - goto out_free_desc; + kfree(desc); + return res; + } + + if (!validate_fsverity_descriptor(inode, desc, res)) { + kfree(desc); + return -EINVAL; } - vi = fsverity_create_info(inode, desc, res); + *desc_ret = desc; + *desc_size_ret = res; + return 0; +} + +/* Ensure the inode has an ->i_verity_info */ +static int ensure_verity_info(struct inode *inode) +{ + struct fsverity_info *vi = fsverity_get_info(inode); + struct fsverity_descriptor *desc; + size_t desc_size; + int err; + + if (vi) + return 0; + + err = fsverity_get_descriptor(inode, &desc, &desc_size); + if (err) + return err; + + vi = fsverity_create_info(inode, desc, desc_size); if (IS_ERR(vi)) { - res = PTR_ERR(vi); + err = PTR_ERR(vi); goto out_free_desc; } fsverity_set_info(inode, vi); - res = 0; + err = 0; out_free_desc: kfree(desc); - return res; + return err; } /** diff --git a/fs/verity/read_metadata.c b/fs/verity/read_metadata.c new file mode 100644 index 000000000000..7e2d0c7bdf0d --- /dev/null +++ b/fs/verity/read_metadata.c @@ -0,0 +1,195 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Ioctl to read verity metadata + * + * Copyright 2021 Google LLC + */ + +#include "fsverity_private.h" + +#include <linux/backing-dev.h> +#include <linux/highmem.h> +#include <linux/sched/signal.h> +#include <linux/uaccess.h> + +static int fsverity_read_merkle_tree(struct inode *inode, + const struct fsverity_info *vi, + void __user *buf, u64 offset, int length) +{ + const struct fsverity_operations *vops = inode->i_sb->s_vop; + u64 end_offset; + unsigned int offs_in_page; + pgoff_t index, last_index; + int retval = 0; + int err = 0; + + end_offset = min(offset + length, vi->tree_params.tree_size); + if (offset >= end_offset) + return 0; + offs_in_page = offset_in_page(offset); + last_index = (end_offset - 1) >> PAGE_SHIFT; + + /* + * Iterate through each Merkle tree page in the requested range and copy + * the requested portion to userspace. Note that the Merkle tree block + * size isn't important here, as we are returning a byte stream; i.e., + * we can just work with pages even if the tree block size != PAGE_SIZE. + */ + for (index = offset >> PAGE_SHIFT; index <= last_index; index++) { + unsigned long num_ra_pages = + min_t(unsigned long, last_index - index + 1, + inode->i_sb->s_bdi->io_pages); + unsigned int bytes_to_copy = min_t(u64, end_offset - offset, + PAGE_SIZE - offs_in_page); + struct page *page; + const void *virt; + + page = vops->read_merkle_tree_page(inode, index, num_ra_pages); + if (IS_ERR(page)) { + err = PTR_ERR(page); + fsverity_err(inode, + "Error %d reading Merkle tree page %lu", + err, index); + break; + } + + virt = kmap(page); + if (copy_to_user(buf, virt + offs_in_page, bytes_to_copy)) { + kunmap(page); + put_page(page); + err = -EFAULT; + break; + } + kunmap(page); + put_page(page); + + retval += bytes_to_copy; + buf += bytes_to_copy; + offset += bytes_to_copy; + + if (fatal_signal_pending(current)) { + err = -EINTR; + break; + } + cond_resched(); + offs_in_page = 0; + } + return retval ? retval : err; +} + +/* Copy the requested portion of the buffer to userspace. */ +static int fsverity_read_buffer(void __user *dst, u64 offset, int length, + const void *src, size_t src_length) +{ + if (offset >= src_length) + return 0; + src += offset; + src_length -= offset; + + length = min_t(size_t, length, src_length); + + if (copy_to_user(dst, src, length)) + return -EFAULT; + + return length; +} + +static int fsverity_read_descriptor(struct inode *inode, + void __user *buf, u64 offset, int length) +{ + struct fsverity_descriptor *desc; + size_t desc_size; + int res; + + res = fsverity_get_descriptor(inode, &desc, &desc_size); + if (res) + return res; + + /* don't include the signature */ + desc_size = offsetof(struct fsverity_descriptor, signature); + desc->sig_size = 0; + + res = fsverity_read_buffer(buf, offset, length, desc, desc_size); + + kfree(desc); + return res; +} + +static int fsverity_read_signature(struct inode *inode, + void __user *buf, u64 offset, int length) +{ + struct fsverity_descriptor *desc; + size_t desc_size; + int res; + + res = fsverity_get_descriptor(inode, &desc, &desc_size); + if (res) + return res; + + if (desc->sig_size == 0) { + res = -ENODATA; + goto out; + } + + /* + * Include only the signature. Note that fsverity_get_descriptor() + * already verified that sig_size is in-bounds. + */ + res = fsverity_read_buffer(buf, offset, length, desc->signature, + le32_to_cpu(desc->sig_size)); +out: + kfree(desc); + return res; +} + +/** + * fsverity_ioctl_read_metadata() - read verity metadata from a file + * @filp: file to read the metadata from + * @uarg: user pointer to fsverity_read_metadata_arg + * + * Return: length read on success, 0 on EOF, -errno on failure + */ +int fsverity_ioctl_read_metadata(struct file *filp, const void __user *uarg) +{ + struct inode *inode = file_inode(filp); + const struct fsverity_info *vi; + struct fsverity_read_metadata_arg arg; + int length; + void __user *buf; + + vi = fsverity_get_info(inode); + if (!vi) + return -ENODATA; /* not a verity file */ + /* + * Note that we don't have to explicitly check that the file is open for + * reading, since verity files can only be opened for reading. + */ + + if (copy_from_user(&arg, uarg, sizeof(arg))) + return -EFAULT; + + if (arg.__reserved) + return -EINVAL; + + /* offset + length must not overflow. */ + if (arg.offset + arg.length < arg.offset) + return -EINVAL; + + /* Ensure that the return value will fit in INT_MAX. */ + length = min_t(u64, arg.length, INT_MAX); + + buf = u64_to_user_ptr(arg.buf_ptr); + + switch (arg.metadata_type) { + case FS_VERITY_METADATA_TYPE_MERKLE_TREE: + return fsverity_read_merkle_tree(inode, vi, buf, arg.offset, + length); + case FS_VERITY_METADATA_TYPE_DESCRIPTOR: + return fsverity_read_descriptor(inode, buf, arg.offset, length); + case FS_VERITY_METADATA_TYPE_SIGNATURE: + return fsverity_read_signature(inode, buf, arg.offset, length); + default: + return -EINVAL; + } +} +EXPORT_SYMBOL_GPL(fsverity_ioctl_read_metadata); diff --git a/fs/verity/signature.c b/fs/verity/signature.c index 012468eda2a7..143a530a8008 100644 --- a/fs/verity/signature.c +++ b/fs/verity/signature.c @@ -29,21 +29,19 @@ static struct key *fsverity_keyring; /** * fsverity_verify_signature() - check a verity file's signature * @vi: the file's fsverity_info - * @desc: the file's fsverity_descriptor - * @desc_size: size of @desc + * @signature: the file's built-in signature + * @sig_size: size of signature in bytes, or 0 if no signature * - * If the file's fs-verity descriptor includes a signature of the file digest, - * verify it against the certificates in the fs-verity keyring. + * If the file includes a signature of its fs-verity file digest, verify it + * against the certificates in the fs-verity keyring. * * Return: 0 on success (signature valid or not required); -errno on failure */ int fsverity_verify_signature(const struct fsverity_info *vi, - const struct fsverity_descriptor *desc, - size_t desc_size) + const u8 *signature, size_t sig_size) { const struct inode *inode = vi->inode; const struct fsverity_hash_alg *hash_alg = vi->tree_params.hash_alg; - const u32 sig_size = le32_to_cpu(desc->sig_size); struct fsverity_formatted_digest *d; int err; @@ -56,11 +54,6 @@ int fsverity_verify_signature(const struct fsverity_info *vi, return 0; } - if (sig_size > desc_size - sizeof(*desc)) { - fsverity_err(inode, "Signature overflows verity descriptor"); - return -EBADMSG; - } - d = kzalloc(sizeof(*d) + hash_alg->digest_size, GFP_KERNEL); if (!d) return -ENOMEM; @@ -70,8 +63,7 @@ int fsverity_verify_signature(const struct fsverity_info *vi, memcpy(d->digest, vi->file_digest, hash_alg->digest_size); err = verify_pkcs7_signature(d, sizeof(*d) + hash_alg->digest_size, - desc->signature, sig_size, - fsverity_keyring, + signature, sig_size, fsverity_keyring, VERIFYING_UNSPECIFIED_SIGNATURE, NULL, NULL); kfree(d); diff --git a/include/linux/fsverity.h b/include/linux/fsverity.h index c1144a450392..b568b3c7d095 100644 --- a/include/linux/fsverity.h +++ b/include/linux/fsverity.h @@ -138,6 +138,10 @@ int fsverity_file_open(struct inode *inode, struct file *filp); int fsverity_prepare_setattr(struct dentry *dentry, struct iattr *attr); void fsverity_cleanup_inode(struct inode *inode); +/* read_metadata.c */ + +int fsverity_ioctl_read_metadata(struct file *filp, const void __user *uarg); + /* verify.c */ bool fsverity_verify_page(struct page *page); @@ -183,6 +187,14 @@ static inline void fsverity_cleanup_inode(struct inode *inode) { } +/* read_metadata.c */ + +static inline int fsverity_ioctl_read_metadata(struct file *filp, + const void __user *uarg) +{ + return -EOPNOTSUPP; +} + /* verify.c */ static inline bool fsverity_verify_page(struct page *page) diff --git a/include/uapi/linux/fsverity.h b/include/uapi/linux/fsverity.h index 33f44156f8ea..15384e22e331 100644 --- a/include/uapi/linux/fsverity.h +++ b/include/uapi/linux/fsverity.h @@ -83,7 +83,21 @@ struct fsverity_formatted_digest { __u8 digest[]; }; +#define FS_VERITY_METADATA_TYPE_MERKLE_TREE 1 +#define FS_VERITY_METADATA_TYPE_DESCRIPTOR 2 +#define FS_VERITY_METADATA_TYPE_SIGNATURE 3 + +struct fsverity_read_metadata_arg { + __u64 metadata_type; + __u64 offset; + __u64 length; + __u64 buf_ptr; + __u64 __reserved; +}; + #define FS_IOC_ENABLE_VERITY _IOW('f', 133, struct fsverity_enable_arg) #define FS_IOC_MEASURE_VERITY _IOWR('f', 134, struct fsverity_digest) +#define FS_IOC_READ_VERITY_METADATA \ + _IOWR('f', 135, struct fsverity_read_metadata_arg) #endif /* _UAPI_LINUX_FSVERITY_H */ |