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      1 /*
      2  * Copyright (C) 2009 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #define LOG_TAG "backup_data"
     18 
     19 #include <androidfw/BackupHelpers.h>
     20 #include <utils/ByteOrder.h>
     21 
     22 #include <stdio.h>
     23 #include <string.h>
     24 #include <unistd.h>
     25 
     26 #include <cutils/log.h>
     27 
     28 namespace android {
     29 
     30 static const bool kIsDebug = false;
     31 
     32 /*
     33  * File Format (v1):
     34  *
     35  * All ints are stored little-endian.
     36  *
     37  *  - An app_header_v1 struct.
     38  *  - The name of the package, utf-8, null terminated, padded to 4-byte boundary.
     39  *  - A sequence of zero or more key/value paires (entities), each with
     40  *      - A entity_header_v1 struct
     41  *      - The key, utf-8, null terminated, padded to 4-byte boundary.
     42  *      - The value, padded to 4 byte boundary
     43  */
     44 
     45 const static int ROUND_UP[4] = { 0, 3, 2, 1 };
     46 
     47 static inline size_t
     48 padding_extra(size_t n)
     49 {
     50     return ROUND_UP[n % 4];
     51 }
     52 
     53 BackupDataWriter::BackupDataWriter(int fd)
     54     :m_fd(fd),
     55      m_status(NO_ERROR),
     56      m_entityCount(0)
     57 {
     58     m_pos = (ssize_t) lseek(fd, 0, SEEK_CUR);
     59     if (kIsDebug) ALOGI("BackupDataWriter(%d) @ %ld", fd, (long)m_pos);
     60 }
     61 
     62 BackupDataWriter::~BackupDataWriter()
     63 {
     64 }
     65 
     66 // Pad out anything they've previously written to the next 4 byte boundary.
     67 status_t
     68 BackupDataWriter::write_padding_for(int n)
     69 {
     70     ssize_t amt;
     71     ssize_t paddingSize;
     72 
     73     paddingSize = padding_extra(n);
     74     if (paddingSize > 0) {
     75         uint32_t padding = 0xbcbcbcbc;
     76         if (kIsDebug) ALOGI("writing %zd padding bytes for %d", paddingSize, n);
     77         amt = write(m_fd, &padding, paddingSize);
     78         if (amt != paddingSize) {
     79             m_status = errno;
     80             return m_status;
     81         }
     82         m_pos += amt;
     83     }
     84     return NO_ERROR;
     85 }
     86 
     87 status_t
     88 BackupDataWriter::WriteEntityHeader(const String8& key, size_t dataSize)
     89 {
     90     if (m_status != NO_ERROR) {
     91         return m_status;
     92     }
     93 
     94     ssize_t amt;
     95 
     96     amt = write_padding_for(m_pos);
     97     if (amt != 0) {
     98         return amt;
     99     }
    100 
    101     String8 k;
    102     if (m_keyPrefix.length() > 0) {
    103         k = m_keyPrefix;
    104         k += ":";
    105         k += key;
    106     } else {
    107         k = key;
    108     }
    109     if (kIsDebug) {
    110         ALOGD("Writing header: prefix='%s' key='%s' dataSize=%zu", m_keyPrefix.string(),
    111                 key.string(), dataSize);
    112     }
    113 
    114     entity_header_v1 header;
    115     ssize_t keyLen;
    116 
    117     keyLen = k.length();
    118 
    119     header.type = tolel(BACKUP_HEADER_ENTITY_V1);
    120     header.keyLen = tolel(keyLen);
    121     header.dataSize = tolel(dataSize);
    122 
    123     if (kIsDebug) ALOGI("writing entity header, %zu bytes", sizeof(entity_header_v1));
    124     amt = write(m_fd, &header, sizeof(entity_header_v1));
    125     if (amt != sizeof(entity_header_v1)) {
    126         m_status = errno;
    127         return m_status;
    128     }
    129     m_pos += amt;
    130 
    131     if (kIsDebug) ALOGI("writing entity header key, %zd bytes", keyLen+1);
    132     amt = write(m_fd, k.string(), keyLen+1);
    133     if (amt != keyLen+1) {
    134         m_status = errno;
    135         return m_status;
    136     }
    137     m_pos += amt;
    138 
    139     amt = write_padding_for(keyLen+1);
    140 
    141     m_entityCount++;
    142 
    143     return amt;
    144 }
    145 
    146 status_t
    147 BackupDataWriter::WriteEntityData(const void* data, size_t size)
    148 {
    149     if (kIsDebug) ALOGD("Writing data: size=%lu", (unsigned long) size);
    150 
    151     if (m_status != NO_ERROR) {
    152         if (kIsDebug) {
    153             ALOGD("Not writing data - stream in error state %d (%s)", m_status, strerror(m_status));
    154         }
    155         return m_status;
    156     }
    157 
    158     // We don't write padding here, because they're allowed to call this several
    159     // times with smaller buffers.  We write it at the end of WriteEntityHeader
    160     // instead.
    161     ssize_t amt = write(m_fd, data, size);
    162     if (amt != (ssize_t)size) {
    163         m_status = errno;
    164         if (kIsDebug) ALOGD("write returned error %d (%s)", m_status, strerror(m_status));
    165         return m_status;
    166     }
    167     m_pos += amt;
    168     return NO_ERROR;
    169 }
    170 
    171 void
    172 BackupDataWriter::SetKeyPrefix(const String8& keyPrefix)
    173 {
    174     m_keyPrefix = keyPrefix;
    175 }
    176 
    177 
    178 BackupDataReader::BackupDataReader(int fd)
    179     :m_fd(fd),
    180      m_done(false),
    181      m_status(NO_ERROR),
    182      m_entityCount(0)
    183 {
    184     memset(&m_header, 0, sizeof(m_header));
    185     m_pos = (ssize_t) lseek(fd, 0, SEEK_CUR);
    186     if (kIsDebug) ALOGI("BackupDataReader(%d) @ %ld", fd, (long)m_pos);
    187 }
    188 
    189 BackupDataReader::~BackupDataReader()
    190 {
    191 }
    192 
    193 status_t
    194 BackupDataReader::Status()
    195 {
    196     return m_status;
    197 }
    198 
    199 #define CHECK_SIZE(actual, expected) \
    200     do { \
    201         if ((actual) != (expected)) { \
    202             if ((actual) == 0) { \
    203                 m_status = EIO; \
    204                 m_done = true; \
    205             } else { \
    206                 m_status = errno; \
    207                 ALOGD("CHECK_SIZE(a=%ld e=%ld) failed at line %d m_status='%s'", \
    208                     long(actual), long(expected), __LINE__, strerror(m_status)); \
    209             } \
    210             return m_status; \
    211         } \
    212     } while(0)
    213 #define SKIP_PADDING() \
    214     do { \
    215         status_t err = skip_padding(); \
    216         if (err != NO_ERROR) { \
    217             ALOGD("SKIP_PADDING FAILED at line %d", __LINE__); \
    218             m_status = err; \
    219             return err; \
    220         } \
    221     } while(0)
    222 
    223 status_t
    224 BackupDataReader::ReadNextHeader(bool* done, int* type)
    225 {
    226     *done = m_done;
    227     if (m_status != NO_ERROR) {
    228         return m_status;
    229     }
    230 
    231     int amt;
    232 
    233     amt = skip_padding();
    234     if (amt == EIO) {
    235         *done = m_done = true;
    236         return NO_ERROR;
    237     }
    238     else if (amt != NO_ERROR) {
    239         return amt;
    240     }
    241     amt = read(m_fd, &m_header, sizeof(m_header));
    242     *done = m_done = (amt == 0);
    243     if (*done) {
    244         return NO_ERROR;
    245     }
    246     CHECK_SIZE(amt, sizeof(m_header));
    247     m_pos += sizeof(m_header);
    248     if (type) {
    249         *type = m_header.type;
    250     }
    251 
    252     // validate and fix up the fields.
    253     m_header.type = fromlel(m_header.type);
    254     switch (m_header.type)
    255     {
    256         case BACKUP_HEADER_ENTITY_V1:
    257         {
    258             m_header.entity.keyLen = fromlel(m_header.entity.keyLen);
    259             if (m_header.entity.keyLen <= 0) {
    260                 ALOGD("Entity header at %d has keyLen<=0: 0x%08x\n", (int)m_pos,
    261                         (int)m_header.entity.keyLen);
    262                 m_status = EINVAL;
    263             }
    264             m_header.entity.dataSize = fromlel(m_header.entity.dataSize);
    265             m_entityCount++;
    266 
    267             // read the rest of the header (filename)
    268             size_t size = m_header.entity.keyLen;
    269             char* buf = m_key.lockBuffer(size);
    270             if (buf == NULL) {
    271                 m_status = ENOMEM;
    272                 return m_status;
    273             }
    274             int amt = read(m_fd, buf, size+1);
    275             CHECK_SIZE(amt, (int)size+1);
    276             m_key.unlockBuffer(size);
    277             m_pos += size+1;
    278             SKIP_PADDING();
    279             m_dataEndPos = m_pos + m_header.entity.dataSize;
    280 
    281             break;
    282         }
    283         default:
    284             ALOGD("Chunk header at %d has invalid type: 0x%08x",
    285                     (int)(m_pos - sizeof(m_header)), (int)m_header.type);
    286             m_status = EINVAL;
    287     }
    288 
    289     return m_status;
    290 }
    291 
    292 bool
    293 BackupDataReader::HasEntities()
    294 {
    295     return m_status == NO_ERROR && m_header.type == BACKUP_HEADER_ENTITY_V1;
    296 }
    297 
    298 status_t
    299 BackupDataReader::ReadEntityHeader(String8* key, size_t* dataSize)
    300 {
    301     if (m_status != NO_ERROR) {
    302         return m_status;
    303     }
    304     if (m_header.type != BACKUP_HEADER_ENTITY_V1) {
    305         return EINVAL;
    306     }
    307     *key = m_key;
    308     *dataSize = m_header.entity.dataSize;
    309     return NO_ERROR;
    310 }
    311 
    312 status_t
    313 BackupDataReader::SkipEntityData()
    314 {
    315     if (m_status != NO_ERROR) {
    316         return m_status;
    317     }
    318     if (m_header.type != BACKUP_HEADER_ENTITY_V1) {
    319         return EINVAL;
    320     }
    321     if (m_header.entity.dataSize > 0) {
    322         int pos = lseek(m_fd, m_dataEndPos, SEEK_SET);
    323         if (pos == -1) {
    324             return errno;
    325         }
    326         m_pos = pos;
    327     }
    328     SKIP_PADDING();
    329     return NO_ERROR;
    330 }
    331 
    332 ssize_t
    333 BackupDataReader::ReadEntityData(void* data, size_t size)
    334 {
    335     if (m_status != NO_ERROR) {
    336         return -1;
    337     }
    338     int remaining = m_dataEndPos - m_pos;
    339     if (kIsDebug) {
    340         ALOGD("ReadEntityData size=%zu m_pos=0x%zx m_dataEndPos=0x%zx remaining=%d\n",
    341                 size, m_pos, m_dataEndPos, remaining);
    342     }
    343     if (remaining <= 0) {
    344         return 0;
    345     }
    346     if (((int)size) > remaining) {
    347         size = remaining;
    348     }
    349     if (kIsDebug) {
    350         ALOGD("   reading %zu bytes", size);
    351     }
    352     int amt = read(m_fd, data, size);
    353     if (amt < 0) {
    354         m_status = errno;
    355         return -1;
    356     }
    357     if (amt == 0) {
    358         m_status = EIO;
    359         m_done = true;
    360     }
    361     m_pos += amt;
    362     return amt;
    363 }
    364 
    365 status_t
    366 BackupDataReader::skip_padding()
    367 {
    368     ssize_t amt;
    369     ssize_t paddingSize;
    370 
    371     paddingSize = padding_extra(m_pos);
    372     if (paddingSize > 0) {
    373         uint32_t padding;
    374         amt = read(m_fd, &padding, paddingSize);
    375         CHECK_SIZE(amt, paddingSize);
    376         m_pos += amt;
    377     }
    378     return NO_ERROR;
    379 }
    380 
    381 
    382 } // namespace android
    383