1 /* $NetBSD: unpack.c,v 1.3 2017/08/04 07:27:08 mrg Exp $ */ 2 3 /*- 4 * SPDX-License-Identifier: BSD-2-Clause 5 * 6 * Copyright (c) 2009 Xin LI <delphij@FreeBSD.org> 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 */ 29 30 /* This file is #included by gzip.c */ 31 32 /* 33 * pack(1) file format: 34 * 35 * The first 7 bytes is the header: 36 * 00, 01 - Signature (US, RS), we already validated it earlier. 37 * 02..05 - Uncompressed size 38 * 06 - Level for the huffman tree (<=24) 39 * 40 * pack(1) will then store symbols (leaf) nodes count in each huffman 41 * tree levels, each level would consume 1 byte (See [1]). 42 * 43 * After the symbol count table, there is the symbol table, storing 44 * symbols represented by corresponding leaf node. EOB is not being 45 * explicitly transmitted (not necessary anyway) in the symbol table. 46 * 47 * Compressed data goes after the symbol table. 48 * 49 * NOTES 50 * 51 * [1] If we count EOB into the symbols, that would mean that we will 52 * have at most 256 symbols in the huffman tree. pack(1) rejects empty 53 * file and files that just repeats one character, which means that we 54 * will have at least 2 symbols. Therefore, pack(1) would reduce the 55 * last level symbol count by 2 which makes it a number in 56 * range [0..254], so all levels' symbol count would fit into 1 byte. 57 */ 58 59 #define PACK_HEADER_LENGTH 7 60 #define HTREE_MAXLEVEL 24 61 62 /* 63 * unpack descriptor 64 * 65 * Represent the huffman tree in a similar way that pack(1) would 66 * store in a packed file. We store all symbols in a linear table, 67 * and store pointers to each level's first symbol. In addition to 68 * that, maintain two counts for each level: inner nodes count and 69 * leaf nodes count. 70 */ 71 typedef struct { 72 int symbol_size; /* Size of the symbol table */ 73 int treelevels; /* Levels for the huffman tree */ 74 75 int *symbolsin; /* Table of leaf symbols count in each 76 * level */ 77 int *inodesin; /* Table of internal nodes count in 78 * each level */ 79 80 char *symbol; /* The symbol table */ 81 char *symbol_eob; /* Pointer to the EOB symbol */ 82 char **tree; /* Decoding huffman tree (pointers to 83 * first symbol of each tree level */ 84 85 off_t uncompressed_size; /* Uncompressed size */ 86 FILE *fpIn; /* Input stream */ 87 FILE *fpOut; /* Output stream */ 88 } unpack_descriptor_t; 89 90 /* 91 * Release resource allocated to an unpack descriptor. 92 * 93 * Caller is responsible to make sure that all of these pointers are 94 * initialized (in our case, they all point to valid memory block). 95 * We don't zero out pointers here because nobody else would ever 96 * reference the memory block without scrubbing them. 97 */ 98 static void 99 unpack_descriptor_fini(unpack_descriptor_t *unpackd) 100 { 101 102 free(unpackd->symbolsin); 103 free(unpackd->inodesin); 104 free(unpackd->symbol); 105 free(unpackd->tree); 106 107 fclose(unpackd->fpIn); 108 fclose(unpackd->fpOut); 109 } 110 111 /* 112 * Recursively fill the internal node count table 113 */ 114 static void 115 unpackd_fill_inodesin(const unpack_descriptor_t *unpackd, int level) 116 { 117 118 /* 119 * The internal nodes would be 1/2 of total internal nodes and 120 * leaf nodes in the next level. For the last level there 121 * would be no internal node by definition. 122 */ 123 if (level < unpackd->treelevels) { 124 unpackd_fill_inodesin(unpackd, level + 1); 125 unpackd->inodesin[level] = (unpackd->inodesin[level + 1] + 126 unpackd->symbolsin[level + 1]) / 2; 127 } else 128 unpackd->inodesin[level] = 0; 129 } 130 131 /* 132 * Update counter for accepted bytes 133 */ 134 static void 135 accepted_bytes(off_t *bytes_in, off_t newbytes) 136 { 137 138 if (bytes_in != NULL) 139 (*bytes_in) += newbytes; 140 } 141 142 /* 143 * Read file header and construct the tree. Also, prepare the buffered I/O 144 * for decode routine. 145 * 146 * Return value is uncompressed size. 147 */ 148 static void 149 unpack_parse_header(int in, int out, char *pre, size_t prelen, off_t *bytes_in, 150 unpack_descriptor_t *unpackd) 151 { 152 unsigned char hdr[PACK_HEADER_LENGTH]; /* buffer for header */ 153 ssize_t bytesread; /* Bytes read from the file */ 154 int i, j, thisbyte; 155 156 /* Prepend the header buffer if we already read some data */ 157 if (prelen != 0) 158 memcpy(hdr, pre, prelen); 159 160 /* Read in and fill the rest bytes of header */ 161 bytesread = read(in, hdr + prelen, PACK_HEADER_LENGTH - prelen); 162 if (bytesread < 0) 163 maybe_err("Error reading pack header"); 164 infile_newdata(bytesread); 165 166 accepted_bytes(bytes_in, PACK_HEADER_LENGTH); 167 168 /* Obtain uncompressed length (bytes 2,3,4,5) */ 169 unpackd->uncompressed_size = 0; 170 for (i = 2; i <= 5; i++) { 171 unpackd->uncompressed_size <<= 8; 172 unpackd->uncompressed_size |= hdr[i]; 173 } 174 175 /* Get the levels of the tree */ 176 unpackd->treelevels = hdr[6]; 177 if (unpackd->treelevels > HTREE_MAXLEVEL || unpackd->treelevels < 1) 178 maybe_errx("Huffman tree has insane levels"); 179 180 /* Let libc take care for buffering from now on */ 181 if ((unpackd->fpIn = fdopen(in, "r")) == NULL) 182 maybe_err("Can not fdopen() input stream"); 183 if ((unpackd->fpOut = fdopen(out, "w")) == NULL) 184 maybe_err("Can not fdopen() output stream"); 185 186 /* Allocate for the tables of bounds and the tree itself */ 187 unpackd->inodesin = 188 calloc(unpackd->treelevels, sizeof(*(unpackd->inodesin))); 189 unpackd->symbolsin = 190 calloc(unpackd->treelevels, sizeof(*(unpackd->symbolsin))); 191 unpackd->tree = 192 calloc(unpackd->treelevels, (sizeof(*(unpackd->tree)))); 193 if (unpackd->inodesin == NULL || unpackd->symbolsin == NULL || 194 unpackd->tree == NULL) 195 maybe_err("calloc"); 196 197 /* We count from 0 so adjust to match array upper bound */ 198 unpackd->treelevels--; 199 200 /* Read the levels symbol count table and calculate total */ 201 unpackd->symbol_size = 1; /* EOB */ 202 for (i = 0; i <= unpackd->treelevels; i++) { 203 if ((thisbyte = fgetc(unpackd->fpIn)) == EOF) 204 maybe_err("File appears to be truncated"); 205 unpackd->symbolsin[i] = (unsigned char)thisbyte; 206 unpackd->symbol_size += unpackd->symbolsin[i]; 207 } 208 accepted_bytes(bytes_in, unpackd->treelevels); 209 if (unpackd->symbol_size > 256) 210 maybe_errx("Bad symbol table"); 211 infile_newdata(unpackd->treelevels); 212 213 /* Allocate for the symbol table, point symbol_eob at the beginning */ 214 unpackd->symbol_eob = unpackd->symbol = calloc(1, unpackd->symbol_size); 215 if (unpackd->symbol == NULL) 216 maybe_err("calloc"); 217 218 /* 219 * Read in the symbol table, which contain [2, 256] symbols. 220 * In order to fit the count in one byte, pack(1) would offset 221 * it by reducing 2 from the actual number from the last level. 222 * 223 * We adjust the last level's symbol count by 1 here, because 224 * the EOB symbol is not being transmitted explicitly. Another 225 * adjustment would be done later afterward. 226 */ 227 unpackd->symbolsin[unpackd->treelevels]++; 228 for (i = 0; i <= unpackd->treelevels; i++) { 229 unpackd->tree[i] = unpackd->symbol_eob; 230 for (j = 0; j < unpackd->symbolsin[i]; j++) { 231 if ((thisbyte = fgetc(unpackd->fpIn)) == EOF) 232 maybe_errx("Symbol table truncated"); 233 *unpackd->symbol_eob++ = (char)thisbyte; 234 } 235 infile_newdata(unpackd->symbolsin[i]); 236 accepted_bytes(bytes_in, unpackd->symbolsin[i]); 237 } 238 239 /* Now, take account for the EOB symbol as well */ 240 unpackd->symbolsin[unpackd->treelevels]++; 241 242 /* 243 * The symbolsin table has been constructed now. 244 * Calculate the internal nodes count table based on it. 245 */ 246 unpackd_fill_inodesin(unpackd, 0); 247 } 248 249 /* 250 * Decode huffman stream, based on the huffman tree. 251 */ 252 static void 253 unpack_decode(const unpack_descriptor_t *unpackd, off_t *bytes_in) 254 { 255 int thislevel, thiscode, thisbyte, inlevelindex; 256 int i; 257 off_t bytes_out = 0; 258 const char *thissymbol; /* The symbol pointer decoded from stream */ 259 260 /* 261 * Decode huffman. Fetch every bytes from the file, get it 262 * into 'thiscode' bit-by-bit, then output the symbol we got 263 * when one has been found. 264 * 265 * Assumption: sizeof(int) > ((max tree levels + 1) / 8). 266 * bad things could happen if not. 267 */ 268 thislevel = 0; 269 thiscode = thisbyte = 0; 270 271 while ((thisbyte = fgetc(unpackd->fpIn)) != EOF) { 272 accepted_bytes(bytes_in, 1); 273 infile_newdata(1); 274 check_siginfo(); 275 276 /* 277 * Split one bit from thisbyte, from highest to lowest, 278 * feed the bit into thiscode, until we got a symbol from 279 * the tree. 280 */ 281 for (i = 7; i >= 0; i--) { 282 thiscode = (thiscode << 1) | ((thisbyte >> i) & 1); 283 284 /* Did we got a symbol? (referencing leaf node) */ 285 if (thiscode >= unpackd->inodesin[thislevel]) { 286 inlevelindex = 287 thiscode - unpackd->inodesin[thislevel]; 288 if (inlevelindex > unpackd->symbolsin[thislevel]) 289 maybe_errx("File corrupt"); 290 291 thissymbol = 292 &(unpackd->tree[thislevel][inlevelindex]); 293 if ((thissymbol == unpackd->symbol_eob) && 294 (bytes_out == unpackd->uncompressed_size)) 295 goto finished; 296 297 fputc((*thissymbol), unpackd->fpOut); 298 bytes_out++; 299 300 /* Prepare for next input */ 301 thislevel = 0; thiscode = 0; 302 } else { 303 thislevel++; 304 if (thislevel > unpackd->treelevels) 305 maybe_errx("File corrupt"); 306 } 307 } 308 } 309 310 finished: 311 if (bytes_out != unpackd->uncompressed_size) 312 maybe_errx("Premature EOF"); 313 } 314 315 /* Handler for pack(1)'ed file */ 316 static off_t 317 unpack(int in, int out, char *pre, size_t prelen, off_t *bytes_in) 318 { 319 unpack_descriptor_t unpackd; 320 321 in = dup(in); 322 if (in == -1) 323 maybe_err("dup"); 324 out = dup(out); 325 if (out == -1) 326 maybe_err("dup"); 327 328 unpack_parse_header(in, out, pre, prelen, bytes_in, &unpackd); 329 unpack_decode(&unpackd, bytes_in); 330 unpack_descriptor_fini(&unpackd); 331 332 /* If we reached here, the unpack was successful */ 333 return (unpackd.uncompressed_size); 334 } 335