From 4b51c3ab400eb8e02e21a6cd9e39b4800f4ab219 Mon Sep 17 00:00:00 2001 From: Tao Bao Date: Tue, 6 Mar 2018 22:05:25 -0800 Subject: Export fuse_sideload.h for libfusesideload. Move the module into a separate directory so that we can export only the expected header. With this change, minadbd no longer needs to include bootable/recovery. Test: mmma -j bootable/recovery Change-Id: I69b888ceb160a33a67d79c5bda208dc17ad6ed86 --- fuse_sideload/fuse_sideload.cpp | 492 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 492 insertions(+) create mode 100644 fuse_sideload/fuse_sideload.cpp (limited to 'fuse_sideload/fuse_sideload.cpp') diff --git a/fuse_sideload/fuse_sideload.cpp b/fuse_sideload/fuse_sideload.cpp new file mode 100644 index 000000000..1c7e98f01 --- /dev/null +++ b/fuse_sideload/fuse_sideload.cpp @@ -0,0 +1,492 @@ +/* + * Copyright (C) 2014 The Android Open Source Project + * + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +// This module creates a special filesystem containing two files. +// +// "/sideload/package.zip" appears to be a normal file, but reading +// from it causes data to be fetched from the adb host. We can use +// this to sideload packages over an adb connection without having to +// store the entire package in RAM on the device. +// +// Because we may not trust the adb host, this filesystem maintains +// the following invariant: each read of a given position returns the +// same data as the first read at that position. That is, once a +// section of the file is read, future reads of that section return +// the same data. (Otherwise, a malicious adb host process could +// return one set of bits when the package is read for signature +// verification, and then different bits for when the package is +// accessed by the installer.) If the adb host returns something +// different than it did on the first read, the reader of the file +// will see their read fail with EINVAL. +// +// The other file, "/sideload/exit", is used to control the subprocess +// that creates this filesystem. Calling stat() on the exit file +// causes the filesystem to be unmounted and the adb process on the +// device shut down. +// +// Note that only the minimal set of file operations needed for these +// two files is implemented. In particular, you can't opendir() or +// readdir() on the "/sideload" directory; ls on it won't work. + +#include "fuse_sideload.h" + +#include +#include +#include // PATH_MAX +#include +#include +#include +#include +#include +#include +#include // MIN +#include +#include +#include + +#include +#include +#include + +#include +#include +#include + +static constexpr uint64_t PACKAGE_FILE_ID = FUSE_ROOT_ID + 1; +static constexpr uint64_t EXIT_FLAG_ID = FUSE_ROOT_ID + 2; + +static constexpr int NO_STATUS = 1; +static constexpr int NO_STATUS_EXIT = 2; + +using SHA256Digest = std::array; + +struct fuse_data { + android::base::unique_fd ffd; // file descriptor for the fuse socket + + provider_vtab vtab; + + uint64_t file_size; // bytes + + uint32_t block_size; // block size that the adb host is using to send the file to us + uint32_t file_blocks; // file size in block_size blocks + + uid_t uid; + gid_t gid; + + uint32_t curr_block; // cache the block most recently read from the host + uint8_t* block_data; + + uint8_t* extra_block; // another block of storage for reads that span two blocks + + std::vector + hashes; // SHA-256 hash of each block (all zeros if block hasn't been read yet) +}; + +static void fuse_reply(const fuse_data* fd, uint64_t unique, const void* data, size_t len) { + fuse_out_header hdr; + hdr.len = len + sizeof(hdr); + hdr.error = 0; + hdr.unique = unique; + + struct iovec vec[2]; + vec[0].iov_base = &hdr; + vec[0].iov_len = sizeof(hdr); + vec[1].iov_base = const_cast(data); + vec[1].iov_len = len; + + int res = writev(fd->ffd, vec, 2); + if (res == -1) { + printf("*** REPLY FAILED *** %s\n", strerror(errno)); + } +} + +static int handle_init(void* data, fuse_data* fd, const fuse_in_header* hdr) { + const fuse_init_in* req = static_cast(data); + + // Kernel 2.6.16 is the first stable kernel with struct fuse_init_out defined (fuse version 7.6). + // The structure is the same from 7.6 through 7.22. Beginning with 7.23, the structure increased + // in size and added new parameters. + if (req->major != FUSE_KERNEL_VERSION || req->minor < 6) { + printf("Fuse kernel version mismatch: Kernel version %d.%d, Expected at least %d.6", req->major, + req->minor, FUSE_KERNEL_VERSION); + return -1; + } + + fuse_init_out out; + out.minor = MIN(req->minor, FUSE_KERNEL_MINOR_VERSION); + size_t fuse_struct_size = sizeof(out); +#if defined(FUSE_COMPAT_22_INIT_OUT_SIZE) + /* FUSE_KERNEL_VERSION >= 23. */ + + // If the kernel only works on minor revs older than or equal to 22, then use the older structure + // size since this code only uses the 7.22 version of the structure. + if (req->minor <= 22) { + fuse_struct_size = FUSE_COMPAT_22_INIT_OUT_SIZE; + } +#endif + + out.major = FUSE_KERNEL_VERSION; + out.max_readahead = req->max_readahead; + out.flags = 0; + out.max_background = 32; + out.congestion_threshold = 32; + out.max_write = 4096; + fuse_reply(fd, hdr->unique, &out, fuse_struct_size); + + return NO_STATUS; +} + +static void fill_attr(fuse_attr* attr, const fuse_data* fd, uint64_t nodeid, uint64_t size, + uint32_t mode) { + *attr = {}; + attr->nlink = 1; + attr->uid = fd->uid; + attr->gid = fd->gid; + attr->blksize = 4096; + + attr->ino = nodeid; + attr->size = size; + attr->blocks = (size == 0) ? 0 : (((size - 1) / attr->blksize) + 1); + attr->mode = mode; +} + +static int handle_getattr(void* /* data */, const fuse_data* fd, const fuse_in_header* hdr) { + fuse_attr_out out = {}; + out.attr_valid = 10; + + if (hdr->nodeid == FUSE_ROOT_ID) { + fill_attr(&(out.attr), fd, hdr->nodeid, 4096, S_IFDIR | 0555); + } else if (hdr->nodeid == PACKAGE_FILE_ID) { + fill_attr(&(out.attr), fd, PACKAGE_FILE_ID, fd->file_size, S_IFREG | 0444); + } else if (hdr->nodeid == EXIT_FLAG_ID) { + fill_attr(&(out.attr), fd, EXIT_FLAG_ID, 0, S_IFREG | 0); + } else { + return -ENOENT; + } + + fuse_reply(fd, hdr->unique, &out, sizeof(out)); + return (hdr->nodeid == EXIT_FLAG_ID) ? NO_STATUS_EXIT : NO_STATUS; +} + +static int handle_lookup(void* data, const fuse_data* fd, const fuse_in_header* hdr) { + if (data == nullptr) return -ENOENT; + + fuse_entry_out out = {}; + out.entry_valid = 10; + out.attr_valid = 10; + + std::string filename(static_cast(data)); + if (filename == FUSE_SIDELOAD_HOST_FILENAME) { + out.nodeid = PACKAGE_FILE_ID; + out.generation = PACKAGE_FILE_ID; + fill_attr(&(out.attr), fd, PACKAGE_FILE_ID, fd->file_size, S_IFREG | 0444); + } else if (filename == FUSE_SIDELOAD_HOST_EXIT_FLAG) { + out.nodeid = EXIT_FLAG_ID; + out.generation = EXIT_FLAG_ID; + fill_attr(&(out.attr), fd, EXIT_FLAG_ID, 0, S_IFREG | 0); + } else { + return -ENOENT; + } + + fuse_reply(fd, hdr->unique, &out, sizeof(out)); + return (out.nodeid == EXIT_FLAG_ID) ? NO_STATUS_EXIT : NO_STATUS; +} + +static int handle_open(void* /* data */, const fuse_data* fd, const fuse_in_header* hdr) { + if (hdr->nodeid == EXIT_FLAG_ID) return -EPERM; + if (hdr->nodeid != PACKAGE_FILE_ID) return -ENOENT; + + fuse_open_out out = {}; + out.fh = 10; // an arbitrary number; we always use the same handle + fuse_reply(fd, hdr->unique, &out, sizeof(out)); + return NO_STATUS; +} + +static int handle_flush(void* /* data */, fuse_data* /* fd */, const fuse_in_header* /* hdr */) { + return 0; +} + +static int handle_release(void* /* data */, fuse_data* /* fd */, const fuse_in_header* /* hdr */) { + return 0; +} + +// Fetch a block from the host into fd->curr_block and fd->block_data. +// Returns 0 on successful fetch, negative otherwise. +static int fetch_block(fuse_data* fd, uint32_t block) { + if (block == fd->curr_block) { + return 0; + } + + if (block >= fd->file_blocks) { + memset(fd->block_data, 0, fd->block_size); + fd->curr_block = block; + return 0; + } + + size_t fetch_size = fd->block_size; + if (block * fd->block_size + fetch_size > fd->file_size) { + // If we're reading the last (partial) block of the file, expect a shorter response from the + // host, and pad the rest of the block with zeroes. + fetch_size = fd->file_size - (block * fd->block_size); + memset(fd->block_data + fetch_size, 0, fd->block_size - fetch_size); + } + + int result = fd->vtab.read_block(block, fd->block_data, fetch_size); + if (result < 0) return result; + + fd->curr_block = block; + + // Verify the hash of the block we just got from the host. + // + // - If the hash of the just-received data matches the stored hash for the block, accept it. + // - If the stored hash is all zeroes, store the new hash and accept the block (this is the first + // time we've read this block). + // - Otherwise, return -EINVAL for the read. + + SHA256Digest hash; + SHA256(fd->block_data, fd->block_size, hash.data()); + + const SHA256Digest& blockhash = fd->hashes[block]; + if (hash == blockhash) { + return 0; + } + + for (uint8_t i : blockhash) { + if (i != 0) { + fd->curr_block = -1; + return -EIO; + } + } + + fd->hashes[block] = hash; + return 0; +} + +static int handle_read(void* data, fuse_data* fd, const fuse_in_header* hdr) { + if (hdr->nodeid != PACKAGE_FILE_ID) return -ENOENT; + + const fuse_read_in* req = static_cast(data); + uint64_t offset = req->offset; + uint32_t size = req->size; + + // The docs on the fuse kernel interface are vague about what to do when a read request extends + // past the end of the file. We can return a short read -- the return structure does include a + // length field -- but in testing that caused the program using the file to segfault. (I + // speculate that this is due to the reading program accessing it via mmap; maybe mmap dislikes + // when you return something short of a whole page?) To fix this we zero-pad reads that extend + // past the end of the file so we're always returning exactly as many bytes as were requested. + // (Users of the mapped file have to know its real length anyway.) + + fuse_out_header outhdr; + outhdr.len = sizeof(outhdr) + size; + outhdr.error = 0; + outhdr.unique = hdr->unique; + + struct iovec vec[3]; + vec[0].iov_base = &outhdr; + vec[0].iov_len = sizeof(outhdr); + + uint32_t block = offset / fd->block_size; + int result = fetch_block(fd, block); + if (result != 0) return result; + + // Two cases: + // + // - the read request is entirely within this block. In this case we can reply immediately. + // + // - the read request goes over into the next block. Note that since we mount the filesystem + // with max_read=block_size, a read can never span more than two blocks. In this case we copy + // the block to extra_block and issue a fetch for the following block. + + uint32_t block_offset = offset - (block * fd->block_size); + + int vec_used; + if (size + block_offset <= fd->block_size) { + // First case: the read fits entirely in the first block. + + vec[1].iov_base = fd->block_data + block_offset; + vec[1].iov_len = size; + vec_used = 2; + } else { + // Second case: the read spills over into the next block. + + memcpy(fd->extra_block, fd->block_data + block_offset, fd->block_size - block_offset); + vec[1].iov_base = fd->extra_block; + vec[1].iov_len = fd->block_size - block_offset; + + result = fetch_block(fd, block + 1); + if (result != 0) return result; + vec[2].iov_base = fd->block_data; + vec[2].iov_len = size - vec[1].iov_len; + vec_used = 3; + } + + if (writev(fd->ffd, vec, vec_used) == -1) { + printf("*** READ REPLY FAILED: %s ***\n", strerror(errno)); + } + return NO_STATUS; +} + +int run_fuse_sideload(const provider_vtab& vtab, uint64_t file_size, uint32_t block_size, + const char* mount_point) { + // If something's already mounted on our mountpoint, try to remove it. (Mostly in case of a + // previous abnormal exit.) + umount2(mount_point, MNT_FORCE); + + // fs/fuse/inode.c in kernel code uses the greater of 4096 and the passed-in max_read. + if (block_size < 4096) { + fprintf(stderr, "block size (%u) is too small\n", block_size); + return -1; + } + if (block_size > (1 << 22)) { // 4 MiB + fprintf(stderr, "block size (%u) is too large\n", block_size); + return -1; + } + + fuse_data fd = {}; + fd.vtab = vtab; + fd.file_size = file_size; + fd.block_size = block_size; + fd.file_blocks = (file_size == 0) ? 0 : (((file_size - 1) / block_size) + 1); + + int result; + if (fd.file_blocks > (1 << 18)) { + fprintf(stderr, "file has too many blocks (%u)\n", fd.file_blocks); + result = -1; + goto done; + } + + // All hashes will be zero-initialized. + fd.hashes.resize(fd.file_blocks); + fd.uid = getuid(); + fd.gid = getgid(); + + fd.curr_block = -1; + fd.block_data = static_cast(malloc(block_size)); + if (fd.block_data == nullptr) { + fprintf(stderr, "failed to allocate %d bites for block_data\n", block_size); + result = -1; + goto done; + } + fd.extra_block = static_cast(malloc(block_size)); + if (fd.extra_block == nullptr) { + fprintf(stderr, "failed to allocate %d bites for extra_block\n", block_size); + result = -1; + goto done; + } + + fd.ffd.reset(open("/dev/fuse", O_RDWR)); + if (!fd.ffd) { + perror("open /dev/fuse"); + result = -1; + goto done; + } + + { + std::string opts = android::base::StringPrintf( + "fd=%d,user_id=%d,group_id=%d,max_read=%u,allow_other,rootmode=040000", fd.ffd.get(), + fd.uid, fd.gid, block_size); + + result = mount("/dev/fuse", mount_point, "fuse", MS_NOSUID | MS_NODEV | MS_RDONLY | MS_NOEXEC, + opts.c_str()); + if (result == -1) { + perror("mount"); + goto done; + } + } + + uint8_t request_buffer[sizeof(fuse_in_header) + PATH_MAX * 8]; + for (;;) { + ssize_t len = TEMP_FAILURE_RETRY(read(fd.ffd, request_buffer, sizeof(request_buffer))); + if (len == -1) { + perror("read request"); + if (errno == ENODEV) { + result = -1; + break; + } + continue; + } + + if (static_cast(len) < sizeof(fuse_in_header)) { + fprintf(stderr, "request too short: len=%zd\n", len); + continue; + } + + fuse_in_header* hdr = reinterpret_cast(request_buffer); + void* data = request_buffer + sizeof(fuse_in_header); + + result = -ENOSYS; + + switch (hdr->opcode) { + case FUSE_INIT: + result = handle_init(data, &fd, hdr); + break; + + case FUSE_LOOKUP: + result = handle_lookup(data, &fd, hdr); + break; + + case FUSE_GETATTR: + result = handle_getattr(data, &fd, hdr); + break; + + case FUSE_OPEN: + result = handle_open(data, &fd, hdr); + break; + + case FUSE_READ: + result = handle_read(data, &fd, hdr); + break; + + case FUSE_FLUSH: + result = handle_flush(data, &fd, hdr); + break; + + case FUSE_RELEASE: + result = handle_release(data, &fd, hdr); + break; + + default: + fprintf(stderr, "unknown fuse request opcode %d\n", hdr->opcode); + break; + } + + if (result == NO_STATUS_EXIT) { + result = 0; + break; + } + + if (result != NO_STATUS) { + fuse_out_header outhdr; + outhdr.len = sizeof(outhdr); + outhdr.error = result; + outhdr.unique = hdr->unique; + TEMP_FAILURE_RETRY(write(fd.ffd, &outhdr, sizeof(outhdr))); + } + } + +done: + fd.vtab.close(); + + if (umount2(mount_point, MNT_DETACH) == -1) { + fprintf(stderr, "fuse_sideload umount failed: %s\n", strerror(errno)); + } + + free(fd.block_data); + free(fd.extra_block); + + return result; +} -- cgit v1.2.3