1 /* vi: set sw=4 ts=4: */
2 /*
3 * uncompress for busybox -- (c) 2002 Robert Griebl
4 *
5 * based on the original compress42.c source
6 * (see disclaimer below)
7 */
8 /* (N)compress42.c - File compression ala IEEE Computer, Mar 1992.
9 *
10 * Authors:
11 * Spencer W. Thomas (decvax!harpo!utah-cs!utah-gr!thomas)
12 * Jim McKie (decvax!mcvax!jim)
13 * Steve Davies (decvax!vax135!petsd!peora!srd)
14 * Ken Turkowski (decvax!decwrl!turtlevax!ken)
15 * James A. Woods (decvax!ihnp4!ames!jaw)
16 * Joe Orost (decvax!vax135!petsd!joe)
17 * Dave Mack (csu@alembic.acs.com)
18 * Peter Jannesen, Network Communication Systems
19 * (peter@ncs.nl)
20 *
21 * marc@suse.de : a small security fix for a buffer overflow
22 *
23 * [... History snipped ...]
24 */
25 #include "libbb.h"
26 #include "bb_archive.h"
27
28
29 /* Default input buffer size */
30 #define IBUFSIZ 2048
31
32 /* Default output buffer size */
33 #define OBUFSIZ 2048
34
35 /* Defines for third byte of header */
36 #define BIT_MASK 0x1f /* Mask for 'number of compresssion bits' */
37 /* Masks 0x20 and 0x40 are free. */
38 /* I think 0x20 should mean that there is */
39 /* a fourth header byte (for expansion). */
40 #define BLOCK_MODE 0x80 /* Block compression if table is full and */
41 /* compression rate is dropping flush tables */
42 /* the next two codes should not be changed lightly, as they must not */
43 /* lie within the contiguous general code space. */
44 #define FIRST 257 /* first free entry */
45 #define CLEAR 256 /* table clear output code */
46
47 #define INIT_BITS 9 /* initial number of bits/code */
48
49
50 /* machine variants which require cc -Dmachine: pdp11, z8000, DOS */
51 #define HBITS 17 /* 50% occupancy */
52 #define HSIZE (1<<HBITS)
53 #define HMASK (HSIZE-1) /* unused */
54 #define HPRIME 9941 /* unused */
55 #define BITS 16
56 #define BITS_STR "16"
57 #undef MAXSEG_64K /* unused */
58 #define MAXCODE(n) (1L << (n))
59
60 #define htabof(i) htab[i]
61 #define codetabof(i) codetab[i]
62 #define tab_prefixof(i) codetabof(i)
63 #define tab_suffixof(i) ((unsigned char *)(htab))[i]
64 #define de_stack ((unsigned char *)&(htab[HSIZE-1]))
65 #define clear_tab_prefixof() memset(codetab, 0, 256)
66
67 /*
68 * Decompress stdin to stdout. This routine adapts to the codes in the
69 * file building the "string" table on-the-fly; requiring no table to
70 * be stored in the compressed file.
71 */
72
IF_DESKTOP(long long)73 IF_DESKTOP(long long) int FAST_FUNC
74 unpack_Z_stream(transformer_state_t *xstate)
75 {
76 IF_DESKTOP(long long total_written = 0;)
77 IF_DESKTOP(long long) int retval = -1;
78 unsigned char *stackp;
79 int finchar;
80 long oldcode;
81 long incode;
82 int inbits;
83 int posbits;
84 int outpos;
85 int insize;
86 int bitmask;
87 long free_ent;
88 long maxcode;
89 long maxmaxcode;
90 int n_bits;
91 int rsize = 0;
92 unsigned char *inbuf; /* were eating insane amounts of stack - */
93 unsigned char *outbuf; /* bad for some embedded targets */
94 unsigned char *htab;
95 unsigned short *codetab;
96
97 /* Hmm, these were statics - why?! */
98 /* user settable max # bits/code */
99 int maxbits; /* = BITS; */
100 /* block compress mode -C compatible with 2.0 */
101 int block_mode; /* = BLOCK_MODE; */
102
103 if (check_signature16(xstate, COMPRESS_MAGIC))
104 return -1;
105
106 inbuf = xzalloc(IBUFSIZ + 64);
107 outbuf = xzalloc(OBUFSIZ + 2048);
108 htab = xzalloc(HSIZE); /* wasn't zeroed out before, maybe can xmalloc? */
109 codetab = xzalloc(HSIZE * sizeof(codetab[0]));
110
111 insize = 0;
112
113 /* xread isn't good here, we have to return - caller may want
114 * to do some cleanup (e.g. delete incomplete unpacked file etc) */
115 if (full_read(xstate->src_fd, inbuf, 1) != 1) {
116 bb_simple_error_msg("short read");
117 goto err;
118 }
119
120 maxbits = inbuf[0] & BIT_MASK;
121 block_mode = inbuf[0] & BLOCK_MODE;
122 maxmaxcode = MAXCODE(maxbits);
123
124 if (maxbits > BITS) {
125 bb_error_msg("compressed with %d bits, can only handle "
126 BITS_STR" bits", maxbits);
127 goto err;
128 }
129
130 n_bits = INIT_BITS;
131 maxcode = MAXCODE(INIT_BITS) - 1;
132 bitmask = (1 << INIT_BITS) - 1;
133 oldcode = -1;
134 finchar = 0;
135 outpos = 0;
136 posbits = 0 << 3;
137
138 free_ent = ((block_mode) ? FIRST : 256);
139
140 /* As above, initialize the first 256 entries in the table. */
141 /*clear_tab_prefixof(); - done by xzalloc */
142
143 {
144 int i;
145 for (i = 255; i >= 0; --i)
146 tab_suffixof(i) = (unsigned char) i;
147 }
148
149 do {
150 resetbuf:
151 {
152 int i;
153 int e;
154 int o;
155
156 o = posbits >> 3;
157 e = insize - o;
158
159 for (i = 0; i < e; ++i)
160 inbuf[i] = inbuf[i + o];
161
162 insize = e;
163 posbits = 0;
164 }
165
166 if (insize < (int) (IBUFSIZ + 64) - IBUFSIZ) {
167 rsize = safe_read(xstate->src_fd, inbuf + insize, IBUFSIZ);
168 if (rsize < 0)
169 bb_simple_error_msg_and_die(bb_msg_read_error);
170 insize += rsize;
171 }
172
173 inbits = ((rsize > 0) ? (insize - insize % n_bits) << 3 :
174 (insize << 3) - (n_bits - 1));
175
176 while (inbits > posbits) {
177 long code;
178
179 if (free_ent > maxcode) {
180 posbits =
181 ((posbits - 1) +
182 ((n_bits << 3) -
183 (posbits - 1 + (n_bits << 3)) % (n_bits << 3)));
184 ++n_bits;
185 if (n_bits == maxbits) {
186 maxcode = maxmaxcode;
187 } else {
188 maxcode = MAXCODE(n_bits) - 1;
189 }
190 bitmask = (1 << n_bits) - 1;
191 goto resetbuf;
192 }
193 {
194 unsigned char *p = &inbuf[posbits >> 3];
195 code = ((p[0]
196 | ((long) (p[1]) << 8)
197 | ((long) (p[2]) << 16)) >> (posbits & 0x7)) & bitmask;
198 }
199 posbits += n_bits;
200
201 if (oldcode == -1) {
202 if (code >= 256)
203 bb_simple_error_msg_and_die("corrupted data"); /* %ld", code); */
204 oldcode = code;
205 finchar = (int) oldcode;
206 outbuf[outpos++] = (unsigned char) finchar;
207 continue;
208 }
209
210 if (code == CLEAR && block_mode) {
211 clear_tab_prefixof();
212 free_ent = FIRST - 1;
213 posbits =
214 ((posbits - 1) +
215 ((n_bits << 3) -
216 (posbits - 1 + (n_bits << 3)) % (n_bits << 3)));
217 n_bits = INIT_BITS;
218 maxcode = MAXCODE(INIT_BITS) - 1;
219 bitmask = (1 << INIT_BITS) - 1;
220 goto resetbuf;
221 }
222
223 incode = code;
224 stackp = de_stack;
225
226 /* Special case for KwKwK string. */
227 if (code >= free_ent) {
228 if (code > free_ent) {
229 /*
230 unsigned char *p;
231
232 posbits -= n_bits;
233 p = &inbuf[posbits >> 3];
234 bb_error_msg
235 ("insize:%d posbits:%d inbuf:%02X %02X %02X %02X %02X (%d)",
236 insize, posbits, p[-1], p[0], p[1], p[2], p[3],
237 (posbits & 07));
238 */
239 bb_simple_error_msg("corrupted data");
240 goto err;
241 }
242
243 *--stackp = (unsigned char) finchar;
244 code = oldcode;
245 }
246
247 /* Generate output characters in reverse order */
248 while (code >= 256) {
249 if (stackp <= &htabof(0))
250 bb_simple_error_msg_and_die("corrupted data");
251 *--stackp = tab_suffixof(code);
252 code = tab_prefixof(code);
253 }
254
255 finchar = tab_suffixof(code);
256 *--stackp = (unsigned char) finchar;
257
258 /* And put them out in forward order */
259 {
260 int i;
261
262 i = de_stack - stackp;
263 if (outpos + i >= OBUFSIZ) {
264 do {
265 if (i > OBUFSIZ - outpos) {
266 i = OBUFSIZ - outpos;
267 }
268
269 if (i > 0) {
270 memcpy(outbuf + outpos, stackp, i);
271 outpos += i;
272 }
273
274 if (outpos >= OBUFSIZ) {
275 xtransformer_write(xstate, outbuf, outpos);
276 IF_DESKTOP(total_written += outpos;)
277 outpos = 0;
278 }
279 stackp += i;
280 i = de_stack - stackp;
281 } while (i > 0);
282 } else {
283 memcpy(outbuf + outpos, stackp, i);
284 outpos += i;
285 }
286 }
287
288 /* Generate the new entry. */
289 if (free_ent < maxmaxcode) {
290 tab_prefixof(free_ent) = (unsigned short) oldcode;
291 tab_suffixof(free_ent) = (unsigned char) finchar;
292 free_ent++;
293 }
294
295 /* Remember previous code. */
296 oldcode = incode;
297 }
298 } while (rsize > 0);
299
300 if (outpos > 0) {
301 xtransformer_write(xstate, outbuf, outpos);
302 IF_DESKTOP(total_written += outpos;)
303 }
304
305 retval = IF_DESKTOP(total_written) + 0;
306 err:
307 free(inbuf);
308 free(outbuf);
309 free(htab);
310 free(codetab);
311 return retval;
312 }
313