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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 DEBUG = 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
round_up(size_t n)48 round_up(size_t n)
49 {
50     return n + ROUND_UP[n % 4];
51 }
52 
53 static inline size_t
padding_extra(size_t n)54 padding_extra(size_t n)
55 {
56     return ROUND_UP[n % 4];
57 }
58 
BackupDataWriter(int fd)59 BackupDataWriter::BackupDataWriter(int fd)
60     :m_fd(fd),
61      m_status(NO_ERROR),
62      m_pos(0),
63      m_entityCount(0)
64 {
65 }
66 
~BackupDataWriter()67 BackupDataWriter::~BackupDataWriter()
68 {
69 }
70 
71 // Pad out anything they've previously written to the next 4 byte boundary.
72 status_t
write_padding_for(int n)73 BackupDataWriter::write_padding_for(int n)
74 {
75     ssize_t amt;
76     ssize_t paddingSize;
77 
78     paddingSize = padding_extra(n);
79     if (paddingSize > 0) {
80         uint32_t padding = 0xbcbcbcbc;
81         if (DEBUG) ALOGI("writing %d padding bytes for %d", paddingSize, n);
82         amt = write(m_fd, &padding, paddingSize);
83         if (amt != paddingSize) {
84             m_status = errno;
85             return m_status;
86         }
87         m_pos += amt;
88     }
89     return NO_ERROR;
90 }
91 
92 status_t
WriteEntityHeader(const String8 & key,size_t dataSize)93 BackupDataWriter::WriteEntityHeader(const String8& key, size_t dataSize)
94 {
95     if (m_status != NO_ERROR) {
96         return m_status;
97     }
98 
99     ssize_t amt;
100 
101     amt = write_padding_for(m_pos);
102     if (amt != 0) {
103         return amt;
104     }
105 
106     String8 k;
107     if (m_keyPrefix.length() > 0) {
108         k = m_keyPrefix;
109         k += ":";
110         k += key;
111     } else {
112         k = key;
113     }
114     if (DEBUG) {
115         ALOGD("Writing header: prefix='%s' key='%s' dataSize=%d", m_keyPrefix.string(),
116                 key.string(), dataSize);
117     }
118 
119     entity_header_v1 header;
120     ssize_t keyLen;
121 
122     keyLen = k.length();
123 
124     header.type = tolel(BACKUP_HEADER_ENTITY_V1);
125     header.keyLen = tolel(keyLen);
126     header.dataSize = tolel(dataSize);
127 
128     if (DEBUG) ALOGI("writing entity header, %d bytes", sizeof(entity_header_v1));
129     amt = write(m_fd, &header, sizeof(entity_header_v1));
130     if (amt != sizeof(entity_header_v1)) {
131         m_status = errno;
132         return m_status;
133     }
134     m_pos += amt;
135 
136     if (DEBUG) ALOGI("writing entity header key, %d bytes", keyLen+1);
137     amt = write(m_fd, k.string(), keyLen+1);
138     if (amt != keyLen+1) {
139         m_status = errno;
140         return m_status;
141     }
142     m_pos += amt;
143 
144     amt = write_padding_for(keyLen+1);
145 
146     m_entityCount++;
147 
148     return amt;
149 }
150 
151 status_t
WriteEntityData(const void * data,size_t size)152 BackupDataWriter::WriteEntityData(const void* data, size_t size)
153 {
154     if (DEBUG) ALOGD("Writing data: size=%lu", (unsigned long) size);
155 
156     if (m_status != NO_ERROR) {
157         if (DEBUG) {
158             ALOGD("Not writing data - stream in error state %d (%s)", m_status, strerror(m_status));
159         }
160         return m_status;
161     }
162 
163     // We don't write padding here, because they're allowed to call this several
164     // times with smaller buffers.  We write it at the end of WriteEntityHeader
165     // instead.
166     ssize_t amt = write(m_fd, data, size);
167     if (amt != (ssize_t)size) {
168         m_status = errno;
169         if (DEBUG) ALOGD("write returned error %d (%s)", m_status, strerror(m_status));
170         return m_status;
171     }
172     m_pos += amt;
173     return NO_ERROR;
174 }
175 
176 void
SetKeyPrefix(const String8 & keyPrefix)177 BackupDataWriter::SetKeyPrefix(const String8& keyPrefix)
178 {
179     m_keyPrefix = keyPrefix;
180 }
181 
182 
BackupDataReader(int fd)183 BackupDataReader::BackupDataReader(int fd)
184     :m_fd(fd),
185      m_done(false),
186      m_status(NO_ERROR),
187      m_pos(0),
188      m_entityCount(0)
189 {
190     memset(&m_header, 0, sizeof(m_header));
191 }
192 
~BackupDataReader()193 BackupDataReader::~BackupDataReader()
194 {
195 }
196 
197 status_t
Status()198 BackupDataReader::Status()
199 {
200     return m_status;
201 }
202 
203 #define CHECK_SIZE(actual, expected) \
204     do { \
205         if ((actual) != (expected)) { \
206             if ((actual) == 0) { \
207                 m_status = EIO; \
208                 m_done = true; \
209             } else { \
210                 m_status = errno; \
211                 ALOGD("CHECK_SIZE(a=%ld e=%ld) failed at line %d m_status='%s'", \
212                     long(actual), long(expected), __LINE__, strerror(m_status)); \
213             } \
214             return m_status; \
215         } \
216     } while(0)
217 #define SKIP_PADDING() \
218     do { \
219         status_t err = skip_padding(); \
220         if (err != NO_ERROR) { \
221             ALOGD("SKIP_PADDING FAILED at line %d", __LINE__); \
222             m_status = err; \
223             return err; \
224         } \
225     } while(0)
226 
227 status_t
ReadNextHeader(bool * done,int * type)228 BackupDataReader::ReadNextHeader(bool* done, int* type)
229 {
230     *done = m_done;
231     if (m_status != NO_ERROR) {
232         return m_status;
233     }
234 
235     int amt;
236 
237     amt = skip_padding();
238     if (amt == EIO) {
239         *done = m_done = true;
240         return NO_ERROR;
241     }
242     else if (amt != NO_ERROR) {
243         return amt;
244     }
245     amt = read(m_fd, &m_header, sizeof(m_header));
246     *done = m_done = (amt == 0);
247     if (*done) {
248         return NO_ERROR;
249     }
250     CHECK_SIZE(amt, sizeof(m_header));
251     m_pos += sizeof(m_header);
252     if (type) {
253         *type = m_header.type;
254     }
255 
256     // validate and fix up the fields.
257     m_header.type = fromlel(m_header.type);
258     switch (m_header.type)
259     {
260         case BACKUP_HEADER_ENTITY_V1:
261         {
262             m_header.entity.keyLen = fromlel(m_header.entity.keyLen);
263             if (m_header.entity.keyLen <= 0) {
264                 ALOGD("Entity header at %d has keyLen<=0: 0x%08x\n", (int)m_pos,
265                         (int)m_header.entity.keyLen);
266                 m_status = EINVAL;
267             }
268             m_header.entity.dataSize = fromlel(m_header.entity.dataSize);
269             m_entityCount++;
270 
271             // read the rest of the header (filename)
272             size_t size = m_header.entity.keyLen;
273             char* buf = m_key.lockBuffer(size);
274             if (buf == NULL) {
275                 m_status = ENOMEM;
276                 return m_status;
277             }
278             int amt = read(m_fd, buf, size+1);
279             CHECK_SIZE(amt, (int)size+1);
280             m_key.unlockBuffer(size);
281             m_pos += size+1;
282             SKIP_PADDING();
283             m_dataEndPos = m_pos + m_header.entity.dataSize;
284 
285             break;
286         }
287         default:
288             ALOGD("Chunk header at %d has invalid type: 0x%08x",
289                     (int)(m_pos - sizeof(m_header)), (int)m_header.type);
290             m_status = EINVAL;
291     }
292 
293     return m_status;
294 }
295 
296 bool
HasEntities()297 BackupDataReader::HasEntities()
298 {
299     return m_status == NO_ERROR && m_header.type == BACKUP_HEADER_ENTITY_V1;
300 }
301 
302 status_t
ReadEntityHeader(String8 * key,size_t * dataSize)303 BackupDataReader::ReadEntityHeader(String8* key, size_t* dataSize)
304 {
305     if (m_status != NO_ERROR) {
306         return m_status;
307     }
308     if (m_header.type != BACKUP_HEADER_ENTITY_V1) {
309         return EINVAL;
310     }
311     *key = m_key;
312     *dataSize = m_header.entity.dataSize;
313     return NO_ERROR;
314 }
315 
316 status_t
SkipEntityData()317 BackupDataReader::SkipEntityData()
318 {
319     if (m_status != NO_ERROR) {
320         return m_status;
321     }
322     if (m_header.type != BACKUP_HEADER_ENTITY_V1) {
323         return EINVAL;
324     }
325     if (m_header.entity.dataSize > 0) {
326         int pos = lseek(m_fd, m_dataEndPos, SEEK_SET);
327         if (pos == -1) {
328             return errno;
329         }
330         m_pos = pos;
331     }
332     SKIP_PADDING();
333     return NO_ERROR;
334 }
335 
336 ssize_t
ReadEntityData(void * data,size_t size)337 BackupDataReader::ReadEntityData(void* data, size_t size)
338 {
339     if (m_status != NO_ERROR) {
340         return -1;
341     }
342     int remaining = m_dataEndPos - m_pos;
343     //ALOGD("ReadEntityData size=%d m_pos=0x%x m_dataEndPos=0x%x remaining=%d\n",
344     //        size, m_pos, m_dataEndPos, remaining);
345     if (remaining <= 0) {
346         return 0;
347     }
348     if (((int)size) > remaining) {
349         size = remaining;
350     }
351     //ALOGD("   reading %d bytes", size);
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
skip_padding()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