1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
|
/* SPDX-License-Identifier: GPL-3.0-or-later */
/*
* meta_reader.c
*
* Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
*/
#include "config.h"
#include "sqfs/meta_reader.h"
#include "util.h"
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <stdio.h>
struct sqfs_meta_reader_t {
uint64_t start;
uint64_t limit;
size_t data_used;
/* The location of the current block in the image */
uint64_t block_offset;
/* The location of the next block after the current one */
uint64_t next_block;
/* A byte offset into the uncompressed data of the current block */
size_t offset;
/* The underlying file descriptor to read from */
int fd;
/* A pointer to the compressor to use for extracting data */
compressor_t *cmp;
/* The raw data read from the input file */
uint8_t data[SQFS_META_BLOCK_SIZE];
/* The uncompressed data read from the input file */
uint8_t scratch[SQFS_META_BLOCK_SIZE];
};
sqfs_meta_reader_t *sqfs_meta_reader_create(int fd, compressor_t *cmp,
uint64_t start, uint64_t limit)
{
sqfs_meta_reader_t *m = calloc(1, sizeof(*m));
if (m == NULL) {
perror("creating meta data reader");
return NULL;
}
m->start = start;
m->limit = limit;
m->fd = fd;
m->cmp = cmp;
return m;
}
void sqfs_meta_reader_destroy(sqfs_meta_reader_t *m)
{
free(m);
}
int sqfs_meta_reader_seek(sqfs_meta_reader_t *m, uint64_t block_start,
size_t offset)
{
bool compressed;
uint16_t header;
ssize_t ret;
size_t size;
if (block_start < m->start || block_start >= m->limit)
goto fail_range;
if (block_start == m->block_offset) {
if (offset >= m->data_used)
goto fail_offset;
m->offset = offset;
return 0;
}
if (read_data_at("reading meta data header", block_start,
m->fd, &header, 2)) {
return -1;
}
header = le16toh(header);
compressed = (header & 0x8000) == 0;
size = header & 0x7FFF;
if (size > sizeof(m->data))
goto fail_too_large;
if ((block_start + 2 + size) > m->limit)
goto fail_block_bounds;
if (read_data_at("reading meta data block", block_start + 2,
m->fd, m->data, size)) {
return -1;
}
if (compressed) {
ret = m->cmp->do_block(m->cmp, m->data, size,
m->scratch, sizeof(m->scratch));
if (ret <= 0) {
fputs("error uncompressing meta data block\n", stderr);
return -1;
}
memcpy(m->data, m->scratch, ret);
m->data_used = ret;
} else {
m->data_used = size;
}
if (offset >= m->data_used)
goto fail_offset;
m->block_offset = block_start;
m->next_block = block_start + size + 2;
m->offset = offset;
return 0;
fail_block_bounds:
fputs("found metadata block that exceeds filesystem bounds.\n",
stderr);
return -1;
fail_too_large:
fputs("found metadata block larger than maximum size.\n", stderr);
return -1;
fail_offset:
fputs("Tried to seek past end of metadata block.\n", stderr);
return -1;
fail_range:
fputs("Tried to read meta data block past filesystem bounds.\n",
stderr);
return -1;
}
void sqfs_meta_reader_get_position(sqfs_meta_reader_t *m, uint64_t *block_start,
size_t *offset)
{
*block_start = m->block_offset;
*offset = m->offset;
}
int sqfs_meta_reader_read(sqfs_meta_reader_t *m, void *data, size_t size)
{
size_t diff;
while (size != 0) {
diff = m->data_used - m->offset;
if (diff == 0) {
if (sqfs_meta_reader_seek(m, m->next_block, 0))
return -1;
diff = m->data_used;
}
if (diff > size)
diff = size;
memcpy(data, m->data + m->offset, diff);
m->offset += diff;
data = (char *)data + diff;
size -= diff;
}
return 0;
}
|
