Implement a new method of sideloading over ADB that does not require the entire package to be held in RAM (useful for low-RAM devices and devices using block OTA where we'd rather have more RAM available for binary patching). We communicate with the host using a new adb service called "sideload-host", which makes the host act as a server, sending us different parts of the package file on request. We create a FUSE filesystem that creates a virtual file "/sideload/package.zip" that is backed by the ADB connection -- users see a normal file, but when they read from the file we're actually fetching the data from the adb host. This file is then passed to the verification and installation systems like any other. To prevent a malicious adb host implementation from serving different data to the verification and installation phases of sideloading, the FUSE filesystem verifies that the contents of the file don't change between reads -- every time we fetch a block from the host we compare its hash to the previous hash for that block (if it was read before) and cause the read to fail if it changes. One necessary change is that the minadbd started by recovery in sideload mode no longer drops its root privileges (they're needed to mount the FUSE filesystem). We rely on SELinux enforcement to restrict the set of things that can be accessed. Change-Id: Ida7dbd3b04c1d4e27a2779d88c1da0c7c81fb114
146 lines
4.2 KiB
C++
146 lines
4.2 KiB
C++
/*
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* Copyright (C) 2012 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include <unistd.h>
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#include <dirent.h>
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#include <errno.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/types.h>
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#include <sys/wait.h>
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#include <sys/stat.h>
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#include <signal.h>
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#include <fcntl.h>
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#include "ui.h"
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#include "cutils/properties.h"
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#include "install.h"
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#include "common.h"
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#include "adb_install.h"
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extern "C" {
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#include "minadbd/adb.h"
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}
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static RecoveryUI* ui = NULL;
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static void
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set_usb_driver(bool enabled) {
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int fd = open("/sys/class/android_usb/android0/enable", O_WRONLY);
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if (fd < 0) {
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ui->Print("failed to open driver control: %s\n", strerror(errno));
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return;
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}
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if (write(fd, enabled ? "1" : "0", 1) < 0) {
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ui->Print("failed to set driver control: %s\n", strerror(errno));
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}
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if (close(fd) < 0) {
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ui->Print("failed to close driver control: %s\n", strerror(errno));
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}
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}
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static void
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stop_adbd() {
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property_set("ctl.stop", "adbd");
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set_usb_driver(false);
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}
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static void
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maybe_restart_adbd() {
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char value[PROPERTY_VALUE_MAX+1];
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int len = property_get("ro.debuggable", value, NULL);
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if (len == 1 && value[0] == '1') {
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ui->Print("Restarting adbd...\n");
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set_usb_driver(true);
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property_set("ctl.start", "adbd");
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}
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}
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// How long (in seconds) we wait for the host to start sending us a
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// package, before timing out.
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#define ADB_INSTALL_TIMEOUT 300
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int
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apply_from_adb(RecoveryUI* ui_, int* wipe_cache, const char* install_file) {
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ui = ui_;
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stop_adbd();
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set_usb_driver(true);
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ui->Print("\n\nNow send the package you want to apply\n"
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"to the device with \"adb sideload <filename>\"...\n");
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pid_t child;
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if ((child = fork()) == 0) {
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execl("/sbin/recovery", "recovery", "--adbd", NULL);
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_exit(-1);
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}
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// ADB_SIDELOAD_HOST_PATHNAME will start to exist once the host
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// connects and starts serving a package. Poll for its
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// appearance. (Note that inotify doesn't work with FUSE.)
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int result;
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int status;
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bool waited = false;
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struct stat st;
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for (int i = 0; i < ADB_INSTALL_TIMEOUT; ++i) {
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if (waitpid(child, &status, WNOHANG) != 0) {
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result = INSTALL_ERROR;
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waited = true;
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break;
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}
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if (stat(ADB_SIDELOAD_HOST_PATHNAME, &st) != 0) {
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if (errno == ENOENT && i < ADB_INSTALL_TIMEOUT-1) {
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sleep(1);
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continue;
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} else {
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ui->Print("\nTimed out waiting for package.\n\n", strerror(errno));
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result = INSTALL_ERROR;
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kill(child, SIGKILL);
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break;
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}
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}
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result = install_package(ADB_SIDELOAD_HOST_PATHNAME, wipe_cache, install_file, false);
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break;
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}
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if (!waited) {
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// Calling stat() on this magic filename signals the minadbd
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// subprocess to shut down.
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stat(ADB_SIDELOAD_HOST_EXIT_PATHNAME, &st);
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// TODO(dougz): there should be a way to cancel waiting for a
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// package (by pushing some button combo on the device). For now
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// you just have to 'adb sideload' a file that's not a valid
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// package, like "/dev/null".
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waitpid(child, &status, 0);
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}
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if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
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if (WEXITSTATUS(status) == 3) {
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ui->Print("\nYou need adb 1.0.32 or newer to sideload\nto this device.\n\n");
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} else if (!WIFSIGNALED(status)) {
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ui->Print("\n(adbd status %d)\n", WEXITSTATUS(status));
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}
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}
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set_usb_driver(false);
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maybe_restart_adbd();
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return result;
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}
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