5 files changed, 509 insertions, 202 deletions

diff --git a/uncrypt/Android.mk b/uncrypt/Android.mk
index bd769f900..0a30b49f0 100644
--- a/uncrypt/Android.mk
+++ b/uncrypt/Android.mk
@@ -15,13 +15,30 @@
 LOCAL_PATH := $(call my-dir)
 
 include $(CLEAR_VARS)
+LOCAL_CLANG := true
+LOCAL_SRC_FILES := bootloader_message_writer.cpp
+LOCAL_MODULE := libbootloader_message_writer
+LOCAL_STATIC_LIBRARIES := libbase libfs_mgr
+LOCAL_C_INCLUDES := $(LOCAL_PATH)/..
+LOCAL_EXPORT_C_INCLUDE_DIRS := $(LOCAL_PATH)/include
+include $(BUILD_STATIC_LIBRARY)
+
+include $(CLEAR_VARS)
+
+LOCAL_CLANG := true
 
 LOCAL_C_INCLUDES += $(commands_recovery_local_path)
 
 LOCAL_SRC_FILES := uncrypt.cpp
 LOCAL_MODULE_TAGS := optional
+
+LOCAL_C_INCLUDES := $(LOCAL_PATH)/..
+
 LOCAL_MODULE := uncrypt
 
-LOCAL_STATIC_LIBRARIES := libbase liblog libfs_mgr libcutils
+LOCAL_STATIC_LIBRARIES := libbootloader_message_writer libbase \
+                          liblog libfs_mgr libcutils \
+
+LOCAL_INIT_RC := uncrypt.rc
 
 include $(BUILD_EXECUTABLE)
diff --git a/uncrypt/bootloader_message_writer.cpp b/uncrypt/bootloader_message_writer.cpp
new file mode 100644
index 000000000..3bb106aa0
--- /dev/null
+++ b/uncrypt/bootloader_message_writer.cpp
@@ -0,0 +1,107 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <string.h>
+#include <sys/system_properties.h>
+
+#include <string>
+#include <vector>
+
+#include <android-base/file.h>
+#include <android-base/stringprintf.h>
+#include <android-base/unique_fd.h>
+#include <fs_mgr.h>
+
+#include "bootloader.h"
+
+static struct fstab* read_fstab(std::string* err) {
+  // The fstab path is always "/fstab.${ro.hardware}".
+  std::string fstab_path = "/fstab.";
+  char value[PROP_VALUE_MAX];
+  if (__system_property_get("ro.hardware", value) == 0) {
+    *err = "failed to get ro.hardware";
+    return nullptr;
+  }
+  fstab_path += value;
+  struct fstab* fstab = fs_mgr_read_fstab(fstab_path.c_str());
+  if (fstab == nullptr) {
+    *err = "failed to read " + fstab_path;
+  }
+  return fstab;
+}
+
+static std::string get_misc_blk_device(std::string* err) {
+  struct fstab* fstab = read_fstab(err);
+  if (fstab == nullptr) {
+    return "";
+  }
+  fstab_rec* record = fs_mgr_get_entry_for_mount_point(fstab, "/misc");
+  if (record == nullptr) {
+    *err = "failed to find /misc partition";
+    return "";
+  }
+  return record->blk_device;
+}
+
+static bool write_bootloader_message(const bootloader_message& boot, std::string* err) {
+  std::string misc_blk_device = get_misc_blk_device(err);
+  if (misc_blk_device.empty()) {
+    return false;
+  }
+  android::base::unique_fd fd(open(misc_blk_device.c_str(), O_WRONLY | O_SYNC));
+  if (fd.get() == -1) {
+    *err = android::base::StringPrintf("failed to open %s: %s", misc_blk_device.c_str(),
+                                       strerror(errno));
+    return false;
+  }
+  if (!android::base::WriteFully(fd.get(), &boot, sizeof(boot))) {
+    *err = android::base::StringPrintf("failed to write %s: %s", misc_blk_device.c_str(),
+                                       strerror(errno));
+    return false;
+  }
+  // TODO: O_SYNC and fsync duplicates each other?
+  if (fsync(fd.get()) == -1) {
+    *err = android::base::StringPrintf("failed to fsync %s: %s", misc_blk_device.c_str(),
+                                       strerror(errno));
+    return false;
+  }
+  return true;
+}
+
+bool clear_bootloader_message(std::string* err) {
+  bootloader_message boot = {};
+  return write_bootloader_message(boot, err);
+}
+
+bool write_bootloader_message(const std::vector<std::string>& options, std::string* err) {
+  bootloader_message boot = {};
+  strlcpy(boot.command, "boot-recovery", sizeof(boot.command));
+  strlcpy(boot.recovery, "recovery\n", sizeof(boot.recovery));
+  for (const auto& s : options) {
+    strlcat(boot.recovery, s.c_str(), sizeof(boot.recovery));
+    if (s.back() != '\n') {
+      strlcat(boot.recovery, "\n", sizeof(boot.recovery));
+    }
+  }
+  return write_bootloader_message(boot, err);
+}
+
+extern "C" bool write_bootloader_message(const char* options) {
+  std::string err;
+  return write_bootloader_message({options}, &err);
+}
diff --git a/uncrypt/include/bootloader_message_writer.h b/uncrypt/include/bootloader_message_writer.h
new file mode 100644
index 000000000..e0ca3f44a
--- /dev/null
+++ b/uncrypt/include/bootloader_message_writer.h
@@ -0,0 +1,35 @@
+/*
+ * Copyright (C) 2016 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.
+ */
+
+#ifndef BOOTLOADER_MESSAGE_WRITER_H
+#define BOOTLOADER_MESSAGE_WRITER_H
+
+#ifdef __cplusplus
+#include <string>
+#include <vector>
+
+bool clear_bootloader_message(std::string* err);
+
+bool write_bootloader_message(const std::vector<std::string>& options, std::string* err);
+
+#else
+#include <stdbool.h>
+
+// C Interface.
+bool write_bootloader_message(const char* options);
+#endif
+
+#endif  // BOOTLOADER_MESSAGE_WRITER_H
diff --git a/uncrypt/uncrypt.cpp b/uncrypt/uncrypt.cpp
index 1db3013c6..d7105a01f 100644
--- a/uncrypt/uncrypt.cpp
+++ b/uncrypt/uncrypt.cpp
@@ -39,75 +39,126 @@
 // Recovery can take this block map file and retrieve the underlying
 // file data to use as an update package.
 
+/**
+ * In addition to the uncrypt work, uncrypt also takes care of setting and
+ * clearing the bootloader control block (BCB) at /misc partition.
+ *
+ * uncrypt is triggered as init services on demand. It uses socket to
+ * communicate with its caller (i.e. system_server). The socket is managed by
+ * init (i.e. created prior to the service starts, and destroyed when uncrypt
+ * exits).
+ *
+ * Below is the uncrypt protocol.
+ *
+ *    a. caller                 b. init                    c. uncrypt
+ * ---------------            ------------               --------------
+ *  a1. ctl.start:
+ *    setup-bcb /
+ *    clear-bcb /
+ *    uncrypt
+ *
+ *                         b2. create socket at
+ *                           /dev/socket/uncrypt
+ *
+ *                                                   c3. listen and accept
+ *
+ *  a4. send a 4-byte int
+ *    (message length)
+ *                                                   c5. receive message length
+ *  a6. send message
+ *                                                   c7. receive message
+ *                                                   c8. <do the work; may send
+ *                                                      the progress>
+ *  a9. <may handle progress>
+ *                                                   c10. <upon finishing>
+ *                                                     send "100" or "-1"
+ *
+ *  a11. receive status code
+ *  a12. send a 4-byte int to
+ *    ack the receive of the
+ *    final status code
+ *                                                   c13. receive and exit
+ *
+ *                          b14. destroy the socket
+ *
+ * Note that a12 and c13 are necessary to ensure a11 happens before the socket
+ * gets destroyed in b14.
+ */
+
+#include <arpa/inet.h>
 #include <errno.h>
 #include <fcntl.h>
+#include <inttypes.h>
+#include <libgen.h>
 #include <linux/fs.h>
 #include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/mman.h>
+#include <sys/socket.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <unistd.h>
 
-#include <base/file.h>
-#include <base/strings.h>
+#include <algorithm>
+#include <memory>
+#include <vector>
+
+#include <android-base/file.h>
+#include <android-base/logging.h>
+#include <android-base/stringprintf.h>
+#include <android-base/strings.h>
+#include <bootloader_message_writer.h>
+#include <cutils/android_reboot.h>
 #include <cutils/properties.h>
+#include <cutils/sockets.h>
 #include <fs_mgr.h>
+
 #define LOG_TAG "uncrypt"
 #include <log/log.h>
 
+#include "unique_fd.h"
+
 #define WINDOW_SIZE 5
 
-static const std::string cache_block_map = "/cache/recovery/block.map";
-static const std::string status_file = "/cache/recovery/uncrypt_status";
-static const std::string uncrypt_file = "/cache/recovery/uncrypt_file";
+// uncrypt provides three services: SETUP_BCB, CLEAR_BCB and UNCRYPT.
+//
+// SETUP_BCB and CLEAR_BCB services use socket communication and do not rely
+// on /cache partitions. They will handle requests to reboot into recovery
+// (for applying updates for non-A/B devices, or factory resets for all
+// devices).
+//
+// UNCRYPT service still needs files on /cache partition (UNCRYPT_PATH_FILE
+// and CACHE_BLOCK_MAP). It will be working (and needed) only for non-A/B
+// devices, on which /cache partitions always exist.
+static const std::string CACHE_BLOCK_MAP = "/cache/recovery/block.map";
+static const std::string UNCRYPT_PATH_FILE = "/cache/recovery/uncrypt_file";
+static const std::string UNCRYPT_SOCKET = "uncrypt";
 
-static struct fstab* fstab = NULL;
+static struct fstab* fstab = nullptr;
 
 static int write_at_offset(unsigned char* buffer, size_t size, int wfd, off64_t offset) {
     if (TEMP_FAILURE_RETRY(lseek64(wfd, offset, SEEK_SET)) == -1) {
-        ALOGE("error seeking to offset %lld: %s\n", offset, strerror(errno));
+        ALOGE("error seeking to offset %" PRId64 ": %s", offset, strerror(errno));
         return -1;
     }
-    size_t written = 0;
-    while (written < size) {
-        ssize_t wrote = TEMP_FAILURE_RETRY(write(wfd, buffer + written, size - written));
-        if (wrote == -1) {
-            ALOGE("error writing offset %lld: %s\n", (offset + written), strerror(errno));
-            return -1;
-        }
-        written += wrote;
+    if (!android::base::WriteFully(wfd, buffer, size)) {
+        ALOGE("error writing offset %" PRId64 ": %s", offset, strerror(errno));
+        return -1;
     }
     return 0;
 }
 
-static void add_block_to_ranges(int** ranges, int* range_alloc, int* range_used, int new_block) {
-    // If the current block start is < 0, set the start to the new
-    // block.  (This only happens for the very first block of the very
-    // first range.)
-    if ((*ranges)[*range_used*2-2] < 0) {
-        (*ranges)[*range_used*2-2] = new_block;
-        (*ranges)[*range_used*2-1] = new_block;
-    }
-
-    if (new_block == (*ranges)[*range_used*2-1]) {
+static void add_block_to_ranges(std::vector<int>& ranges, int new_block) {
+    if (!ranges.empty() && new_block == ranges.back()) {
         // If the new block comes immediately after the current range,
         // all we have to do is extend the current range.
-        ++(*ranges)[*range_used*2-1];
+        ++ranges.back();
     } else {
         // We need to start a new range.
-
-        // If there isn't enough room in the array, we need to expand it.
-        if (*range_used >= *range_alloc) {
-            *range_alloc *= 2;
-            *ranges = reinterpret_cast<int*>(realloc(*ranges, *range_alloc * 2 * sizeof(int)));
-        }
-
-        ++*range_used;
-        (*ranges)[*range_used*2-2] = new_block;
-        (*ranges)[*range_used*2-1] = new_block+1;
+        ranges.push_back(new_block);
+        ranges.push_back(new_block + 1);
     }
 }
 
@@ -117,13 +168,13 @@ static struct fstab* read_fstab() {
     // The fstab path is always "/fstab.${ro.hardware}".
     char fstab_path[PATH_MAX+1] = "/fstab.";
     if (!property_get("ro.hardware", fstab_path+strlen(fstab_path), "")) {
-        ALOGE("failed to get ro.hardware\n");
+        ALOGE("failed to get ro.hardware");
         return NULL;
     }
 
     fstab = fs_mgr_read_fstab(fstab_path);
     if (!fstab) {
-        ALOGE("failed to read %s\n", fstab_path);
+        ALOGE("failed to read %s", fstab_path);
         return NULL;
     }
 
@@ -144,7 +195,7 @@ static const char* find_block_device(const char* path, bool* encryptable, bool*
             (path[len] == '/' || path[len] == 0)) {
             *encrypted = false;
             *encryptable = false;
-            if (fs_mgr_is_encryptable(v)) {
+            if (fs_mgr_is_encryptable(v) || fs_mgr_is_file_encrypted(v)) {
                 *encryptable = true;
                 char buffer[PROPERTY_VALUE_MAX+1];
                 if (property_get("ro.crypto.state", buffer, "") &&
@@ -159,101 +210,108 @@ static const char* find_block_device(const char* path, bool* encryptable, bool*
     return NULL;
 }
 
+static bool write_status_to_socket(int status, int socket) {
+    int status_out = htonl(status);
+    return android::base::WriteFully(socket, &status_out, sizeof(int));
+}
+
 // Parse uncrypt_file to find the update package name.
-static bool find_uncrypt_package(std::string& package_name)
-{
-    if (!android::base::ReadFileToString(uncrypt_file, &package_name)) {
-        ALOGE("failed to open \"%s\": %s\n", uncrypt_file.c_str(), strerror(errno));
+static bool find_uncrypt_package(const std::string& uncrypt_path_file, std::string* package_name) {
+    CHECK(package_name != nullptr);
+    std::string uncrypt_path;
+    if (!android::base::ReadFileToString(uncrypt_path_file, &uncrypt_path)) {
+        ALOGE("failed to open \"%s\": %s", uncrypt_path_file.c_str(), strerror(errno));
         return false;
     }
 
     // Remove the trailing '\n' if present.
-    package_name = android::base::Trim(package_name);
-
+    *package_name = android::base::Trim(uncrypt_path);
     return true;
 }
 
 static int produce_block_map(const char* path, const char* map_file, const char* blk_dev,
-                             bool encrypted, int status_fd) {
-    int mapfd = open(map_file, O_WRONLY | O_CREAT | O_SYNC, S_IRUSR | S_IWUSR);
-    if (mapfd == -1) {
-        ALOGE("failed to open %s\n", map_file);
+                             bool encrypted, int socket) {
+    std::string err;
+    if (!android::base::RemoveFileIfExists(map_file, &err)) {
+        ALOGE("failed to remove the existing map file %s: %s", map_file, err.c_str());
+        return -1;
+    }
+    std::string tmp_map_file = std::string(map_file) + ".tmp";
+    unique_fd mapfd(open(tmp_map_file.c_str(), O_WRONLY | O_CREAT, S_IRUSR | S_IWUSR));
+    if (!mapfd) {
+        ALOGE("failed to open %s: %s\n", tmp_map_file.c_str(), strerror(errno));
         return -1;
     }
-    FILE* mapf = fdopen(mapfd, "w");
 
-    // Make sure we can write to the status_file.
-    if (!android::base::WriteStringToFd("0\n", status_fd)) {
-        ALOGE("failed to update \"%s\"\n", status_file.c_str());
+    // Make sure we can write to the socket.
+    if (!write_status_to_socket(0, socket)) {
+        ALOGE("failed to write to socket %d\n", socket);
         return -1;
     }
 
     struct stat sb;
-    int ret = stat(path, &sb);
-    if (ret != 0) {
-        ALOGE("failed to stat %s\n", path);
+    if (stat(path, &sb) != 0) {
+        ALOGE("failed to stat %s", path);
         return -1;
     }
 
-    ALOGI(" block size: %ld bytes\n", (long)sb.st_blksize);
+    ALOGI(" block size: %ld bytes", static_cast<long>(sb.st_blksize));
 
     int blocks = ((sb.st_size-1) / sb.st_blksize) + 1;
-    ALOGI("  file size: %lld bytes, %d blocks\n", (long long)sb.st_size, blocks);
+    ALOGI("  file size: %" PRId64 " bytes, %d blocks", sb.st_size, blocks);
 
-    int range_alloc = 1;
-    int range_used = 1;
-    int* ranges = reinterpret_cast<int*>(malloc(range_alloc * 2 * sizeof(int)));
-    ranges[0] = -1;
-    ranges[1] = -1;
+    std::vector<int> ranges;
 
-    fprintf(mapf, "%s\n%lld %lu\n", blk_dev, (long long)sb.st_size, (unsigned long)sb.st_blksize);
+    std::string s = android::base::StringPrintf("%s\n%" PRId64 " %ld\n",
+                       blk_dev, sb.st_size, static_cast<long>(sb.st_blksize));
+    if (!android::base::WriteStringToFd(s, mapfd.get())) {
+        ALOGE("failed to write %s: %s", tmp_map_file.c_str(), strerror(errno));
+        return -1;
+    }
 
-    unsigned char* buffers[WINDOW_SIZE];
+    std::vector<std::vector<unsigned char>> buffers;
     if (encrypted) {
-        for (size_t i = 0; i < WINDOW_SIZE; ++i) {
-            buffers[i] = reinterpret_cast<unsigned char*>(malloc(sb.st_blksize));
-        }
+        buffers.resize(WINDOW_SIZE, std::vector<unsigned char>(sb.st_blksize));
     }
     int head_block = 0;
     int head = 0, tail = 0;
-    size_t pos = 0;
 
-    int fd = open(path, O_RDONLY);
-    if (fd < 0) {
-        ALOGE("failed to open fd for reading: %s\n", strerror(errno));
+    unique_fd fd(open(path, O_RDONLY));
+    if (!fd) {
+        ALOGE("failed to open %s for reading: %s", path, strerror(errno));
         return -1;
     }
 
-    int wfd = -1;
+    unique_fd wfd(-1);
     if (encrypted) {
-        wfd = open(blk_dev, O_WRONLY | O_SYNC);
-        if (wfd < 0) {
-            ALOGE("failed to open fd for writing: %s\n", strerror(errno));
+        wfd = open(blk_dev, O_WRONLY);
+        if (!wfd) {
+            ALOGE("failed to open fd for writing: %s", strerror(errno));
             return -1;
         }
     }
 
+    off64_t pos = 0;
     int last_progress = 0;
     while (pos < sb.st_size) {
         // Update the status file, progress must be between [0, 99].
         int progress = static_cast<int>(100 * (double(pos) / double(sb.st_size)));
         if (progress > last_progress) {
-          last_progress = progress;
-          android::base::WriteStringToFd(std::to_string(progress) + "\n", status_fd);
+            last_progress = progress;
+            write_status_to_socket(progress, socket);
         }
 
         if ((tail+1) % WINDOW_SIZE == head) {
             // write out head buffer
             int block = head_block;
-            ret = ioctl(fd, FIBMAP, &block);
-            if (ret != 0) {
-                ALOGE("failed to find block %d\n", head_block);
+            if (ioctl(fd.get(), FIBMAP, &block) != 0) {
+                ALOGE("failed to find block %d", head_block);
                 return -1;
             }
-            add_block_to_ranges(&ranges, &range_alloc, &range_used, block);
+            add_block_to_ranges(ranges, block);
             if (encrypted) {
-                if (write_at_offset(buffers[head], sb.st_blksize, wfd,
-                        (off64_t)sb.st_blksize * block) != 0) {
+                if (write_at_offset(buffers[head].data(), sb.st_blksize, wfd.get(),
+                        static_cast<off64_t>(sb.st_blksize) * block) != 0) {
                     return -1;
                 }
             }
@@ -263,17 +321,13 @@ static int produce_block_map(const char* path, const char* map_file, const char*
 
         // read next block to tail
         if (encrypted) {
-            size_t so_far = 0;
-            while (so_far < sb.st_blksize && pos < sb.st_size) {
-                ssize_t this_read =
-                        TEMP_FAILURE_RETRY(read(fd, buffers[tail] + so_far, sb.st_blksize - so_far));
-                if (this_read == -1) {
-                    ALOGE("failed to read: %s\n", strerror(errno));
-                    return -1;
-                }
-                so_far += this_read;
-                pos += this_read;
+            size_t to_read = static_cast<size_t>(
+                    std::min(static_cast<off64_t>(sb.st_blksize), sb.st_size - pos));
+            if (!android::base::ReadFully(fd.get(), buffers[tail].data(), to_read)) {
+                ALOGE("failed to read: %s", strerror(errno));
+                return -1;
             }
+            pos += to_read;
         } else {
             // If we're not encrypting; we don't need to actually read
             // anything, just skip pos forward as if we'd read a
@@ -286,15 +340,14 @@ static int produce_block_map(const char* path, const char* map_file, const char*
     while (head != tail) {
         // write out head buffer
         int block = head_block;
-        ret = ioctl(fd, FIBMAP, &block);
-        if (ret != 0) {
-            ALOGE("failed to find block %d\n", head_block);
+        if (ioctl(fd.get(), FIBMAP, &block) != 0) {
+            ALOGE("failed to find block %d", head_block);
             return -1;
         }
-        add_block_to_ranges(&ranges, &range_alloc, &range_used, block);
+        add_block_to_ranges(ranges, block);
         if (encrypted) {
-            if (write_at_offset(buffers[head], sb.st_blksize, wfd,
-                    (off64_t)sb.st_blksize * block) != 0) {
+            if (write_at_offset(buffers[head].data(), sb.st_blksize, wfd.get(),
+                    static_cast<off64_t>(sb.st_blksize) * block) != 0) {
                 return -1;
             }
         }
@@ -302,68 +355,66 @@ static int produce_block_map(const char* path, const char* map_file, const char*
         ++head_block;
     }
 
-    fprintf(mapf, "%d\n", range_used);
-    for (int i = 0; i < range_used; ++i) {
-        fprintf(mapf, "%d %d\n", ranges[i*2], ranges[i*2+1]);
-    }
-
-    if (fsync(mapfd) == -1) {
-        ALOGE("failed to fsync \"%s\": %s\n", map_file, strerror(errno));
+    if (!android::base::WriteStringToFd(
+            android::base::StringPrintf("%zu\n", ranges.size() / 2), mapfd.get())) {
+        ALOGE("failed to write %s: %s", tmp_map_file.c_str(), strerror(errno));
         return -1;
     }
-    fclose(mapf);
-    close(fd);
-    if (encrypted) {
-        if (fsync(wfd) == -1) {
-            ALOGE("failed to fsync \"%s\": %s\n", blk_dev, strerror(errno));
+    for (size_t i = 0; i < ranges.size(); i += 2) {
+        if (!android::base::WriteStringToFd(
+                android::base::StringPrintf("%d %d\n", ranges[i], ranges[i+1]), mapfd.get())) {
+            ALOGE("failed to write %s: %s", tmp_map_file.c_str(), strerror(errno));
             return -1;
         }
-        close(wfd);
     }
 
-    return 0;
-}
+    if (fsync(mapfd.get()) == -1) {
+        ALOGE("failed to fsync \"%s\": %s", tmp_map_file.c_str(), strerror(errno));
+        return -1;
+    }
+    if (close(mapfd.get()) == -1) {
+        ALOGE("failed to close %s: %s", tmp_map_file.c_str(), strerror(errno));
+        return -1;
+    }
+    mapfd = -1;
 
-static void wipe_misc() {
-    ALOGI("removing old commands from misc");
-    for (int i = 0; i < fstab->num_entries; ++i) {
-        struct fstab_rec* v = &fstab->recs[i];
-        if (!v->mount_point) continue;
-        if (strcmp(v->mount_point, "/misc") == 0) {
-            int fd = open(v->blk_device, O_WRONLY | O_SYNC);
-            uint8_t zeroes[1088];   // sizeof(bootloader_message) from recovery
-            memset(zeroes, 0, sizeof(zeroes));
-
-            size_t written = 0;
-            size_t size = sizeof(zeroes);
-            while (written < size) {
-                ssize_t w = TEMP_FAILURE_RETRY(write(fd, zeroes, size-written));
-                if (w == -1) {
-                    ALOGE("zero write failed: %s\n", strerror(errno));
-                    return;
-                } else {
-                    written += w;
-                }
-            }
-            if (fsync(fd) == -1) {
-                ALOGE("failed to fsync \"%s\": %s\n", v->blk_device, strerror(errno));
-                close(fd);
-                return;
-            }
-            close(fd);
+    if (encrypted) {
+        if (fsync(wfd.get()) == -1) {
+            ALOGE("failed to fsync \"%s\": %s", blk_dev, strerror(errno));
+            return -1;
+        }
+        if (close(wfd.get()) == -1) {
+            ALOGE("failed to close %s: %s", blk_dev, strerror(errno));
+            return -1;
         }
+        wfd = -1;
     }
-}
 
-static void reboot_to_recovery() {
-    ALOGI("rebooting to recovery");
-    property_set("sys.powerctl", "reboot,recovery");
-    sleep(10);
-    ALOGE("reboot didn't succeed?");
+    if (rename(tmp_map_file.c_str(), map_file) == -1) {
+        ALOGE("failed to rename %s to %s: %s", tmp_map_file.c_str(), map_file, strerror(errno));
+        return -1;
+    }
+    // Sync dir to make rename() result written to disk.
+    std::string file_name = map_file;
+    std::string dir_name = dirname(&file_name[0]);
+    unique_fd dfd(open(dir_name.c_str(), O_RDONLY | O_DIRECTORY));
+    if (!dfd) {
+        ALOGE("failed to open dir %s: %s", dir_name.c_str(), strerror(errno));
+        return -1;
+    }
+    if (fsync(dfd.get()) == -1) {
+        ALOGE("failed to fsync %s: %s", dir_name.c_str(), strerror(errno));
+        return -1;
+    }
+    if (close(dfd.get()) == -1) {
+        ALOGE("failed to close %s: %s", dir_name.c_str(), strerror(errno));
+        return -1;
+    }
+    dfd = -1;
+    return 0;
 }
 
-int uncrypt(const char* input_path, const char* map_file, int status_fd) {
-
+static int uncrypt(const char* input_path, const char* map_file, const int socket) {
     ALOGI("update package is \"%s\"", input_path);
 
     // Turn the name of the file we're supposed to convert into an
@@ -374,10 +425,6 @@ int uncrypt(const char* input_path, const char* map_file, int status_fd) {
         return 1;
     }
 
-    if (read_fstab() == NULL) {
-        return 1;
-    }
-
     bool encryptable;
     bool encrypted;
     const char* blk_dev = find_block_device(path, &encryptable, &encrypted);
@@ -389,8 +436,8 @@ int uncrypt(const char* input_path, const char* map_file, int status_fd) {
     // If the filesystem it's on isn't encrypted, we only produce the
     // block map, we don't rewrite the file contents (it would be
     // pointless to do so).
-    ALOGI("encryptable: %s\n", encryptable ? "yes" : "no");
-    ALOGI("  encrypted: %s\n", encrypted ? "yes" : "no");
+    ALOGI("encryptable: %s", encryptable ? "yes" : "no");
+    ALOGI("  encrypted: %s", encrypted ? "yes" : "no");
 
     // Recovery supports installing packages from 3 paths: /cache,
     // /data, and /sdcard.  (On a particular device, other locations
@@ -401,7 +448,7 @@ int uncrypt(const char* input_path, const char* map_file, int status_fd) {
     // and /sdcard we leave the file alone.
     if (strncmp(path, "/data/", 6) == 0) {
         ALOGI("writing block map %s", map_file);
-        if (produce_block_map(path, map_file, blk_dev, encrypted, status_fd) != 0) {
+        if (produce_block_map(path, map_file, blk_dev, encrypted, socket) != 0) {
             return 1;
         }
     }
@@ -409,57 +456,141 @@ int uncrypt(const char* input_path, const char* map_file, int status_fd) {
     return 0;
 }
 
-int main(int argc, char** argv) {
-    const char* input_path;
-    const char* map_file;
+static bool uncrypt_wrapper(const char* input_path, const char* map_file, const int socket) {
+    std::string package;
+    if (input_path == nullptr) {
+        if (!find_uncrypt_package(UNCRYPT_PATH_FILE, &package)) {
+            write_status_to_socket(-1, socket);
+            return false;
+        }
+        input_path = package.c_str();
+    }
+    CHECK(map_file != nullptr);
+    int status = uncrypt(input_path, map_file, socket);
+    if (status != 0) {
+        write_status_to_socket(-1, socket);
+        return false;
+    }
+    write_status_to_socket(100, socket);
+    return true;
+}
 
-    if (argc != 3 && argc != 1 && (argc == 2 && strcmp(argv[1], "--reboot") != 0)) {
-        fprintf(stderr, "usage: %s [--reboot] [<transform_path> <map_file>]\n", argv[0]);
-        return 2;
+static bool clear_bcb(const int socket) {
+    std::string err;
+    if (!clear_bootloader_message(&err)) {
+        ALOGE("failed to clear bootloader message: %s", err.c_str());
+        write_status_to_socket(-1, socket);
+        return false;
     }
+    write_status_to_socket(100, socket);
+    return true;
+}
 
-    // When uncrypt is started with "--reboot", it wipes misc and reboots.
-    // Otherwise it uncrypts the package and writes the block map.
-    if (argc == 2) {
-        if (read_fstab() == NULL) {
-            return 1;
-        }
-        wipe_misc();
-        reboot_to_recovery();
+static bool setup_bcb(const int socket) {
+    // c5. receive message length
+    int length;
+    if (!android::base::ReadFully(socket, &length, 4)) {
+        ALOGE("failed to read the length: %s", strerror(errno));
+        return false;
+    }
+    length = ntohl(length);
+
+    // c7. receive message
+    std::string content;
+    content.resize(length);
+    if (!android::base::ReadFully(socket, &content[0], length)) {
+        ALOGE("failed to read the length: %s", strerror(errno));
+        return false;
+    }
+    ALOGI("  received command: [%s] (%zu)", content.c_str(), content.size());
+
+    // c8. setup the bcb command
+    std::string err;
+    if (!write_bootloader_message({content}, &err)) {
+        ALOGE("failed to set bootloader message: %s", err.c_str());
+        write_status_to_socket(-1, socket);
+        return false;
+    }
+    // c10. send "100" status
+    write_status_to_socket(100, socket);
+    return true;
+}
+
+static void usage(const char* exename) {
+    fprintf(stderr, "Usage of %s:\n", exename);
+    fprintf(stderr, "%s [<package_path> <map_file>]  Uncrypt ota package.\n", exename);
+    fprintf(stderr, "%s --clear-bcb  Clear BCB data in misc partition.\n", exename);
+    fprintf(stderr, "%s --setup-bcb  Setup BCB data by command file.\n", exename);
+}
+
+int main(int argc, char** argv) {
+    enum { UNCRYPT, SETUP_BCB, CLEAR_BCB } action;
+    const char* input_path = nullptr;
+    const char* map_file = CACHE_BLOCK_MAP.c_str();
+
+    if (argc == 2 && strcmp(argv[1], "--clear-bcb") == 0) {
+        action = CLEAR_BCB;
+    } else if (argc == 2 && strcmp(argv[1], "--setup-bcb") == 0) {
+        action = SETUP_BCB;
+    } else if (argc == 1) {
+        action = UNCRYPT;
+    } else if (argc == 3) {
+        input_path = argv[1];
+        map_file = argv[2];
+        action = UNCRYPT;
     } else {
-        // The pipe has been created by the system server.
-        int status_fd = open(status_file.c_str(), O_WRONLY | O_CREAT | O_SYNC, S_IRUSR | S_IWUSR);
-        if (status_fd == -1) {
-            ALOGE("failed to open pipe \"%s\": %s\n", status_file.c_str(), strerror(errno));
-            return 1;
-        }
+        usage(argv[0]);
+        return 2;
+    }
 
-        if (argc == 3) {
-            // when command-line args are given this binary is being used
-            // for debugging.
-            input_path = argv[1];
-            map_file = argv[2];
-        } else {
-            std::string package;
-            if (!find_uncrypt_package(package)) {
-                android::base::WriteStringToFd("-1\n", status_fd);
-                close(status_fd);
-                return 1;
-            }
-            input_path = package.c_str();
-            map_file = cache_block_map.c_str();
-        }
+    if ((fstab = read_fstab()) == nullptr) {
+        return 1;
+    }
 
-        int status = uncrypt(input_path, map_file, status_fd);
-        if (status != 0) {
-            android::base::WriteStringToFd("-1\n", status_fd);
-            close(status_fd);
-            return 1;
-        }
+    // c3. The socket is created by init when starting the service. uncrypt
+    // will use the socket to communicate with its caller.
+    unique_fd service_socket(android_get_control_socket(UNCRYPT_SOCKET.c_str()));
+    if (!service_socket) {
+        ALOGE("failed to open socket \"%s\": %s", UNCRYPT_SOCKET.c_str(), strerror(errno));
+        return 1;
+    }
+    fcntl(service_socket.get(), F_SETFD, FD_CLOEXEC);
 
-        android::base::WriteStringToFd("100\n", status_fd);
-        close(status_fd);
+    if (listen(service_socket.get(), 1) == -1) {
+        ALOGE("failed to listen on socket %d: %s", service_socket.get(), strerror(errno));
+        return 1;
     }
 
-    return 0;
+    unique_fd socket_fd(accept4(service_socket.get(), nullptr, nullptr, SOCK_CLOEXEC));
+    if (!socket_fd) {
+        ALOGE("failed to accept on socket %d: %s", service_socket.get(), strerror(errno));
+        return 1;
+    }
+
+    bool success = false;
+    switch (action) {
+        case UNCRYPT:
+            success = uncrypt_wrapper(input_path, map_file, socket_fd.get());
+            break;
+        case SETUP_BCB:
+            success = setup_bcb(socket_fd.get());
+            break;
+        case CLEAR_BCB:
+            success = clear_bcb(socket_fd.get());
+            break;
+        default:  // Should never happen.
+            ALOGE("Invalid uncrypt action code: %d", action);
+            return 1;
+    }
+
+    // c13. Read a 4-byte code from the client before uncrypt exits. This is to
+    // ensure the client to receive the last status code before the socket gets
+    // destroyed.
+    int code;
+    if (android::base::ReadFully(socket_fd.get(), &code, 4)) {
+        ALOGI("  received %d, exiting now", code);
+    } else {
+        ALOGE("failed to read the code: %s", strerror(errno));
+    }
+    return success ? 0 : 1;
 }
diff --git a/uncrypt/uncrypt.rc b/uncrypt/uncrypt.rc
new file mode 100644
index 000000000..52f564eb6
--- /dev/null
+++ b/uncrypt/uncrypt.rc
@@ -0,0 +1,17 @@
+service uncrypt /system/bin/uncrypt
+    class main
+    socket uncrypt stream 600 system system
+    disabled
+    oneshot
+
+service setup-bcb /system/bin/uncrypt --setup-bcb
+    class main
+    socket uncrypt stream 600 system system
+    disabled
+    oneshot
+
+service clear-bcb /system/bin/uncrypt --clear-bcb
+    class main
+    socket uncrypt stream 600 system system
+    disabled
+    oneshot