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