1 /*- 2 * Copyright (c) 2007 S.Sam Arun Raj 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24 * SUCH DAMAGE. 25 */ 26 27 #include <sys/types.h> 28 #include <sys/stat.h> 29 30 #include <ctype.h> 31 #include <err.h> 32 #include <errno.h> 33 #include <fcntl.h> 34 #include <getopt.h> 35 #include <inttypes.h> 36 #include <stdint.h> 37 #include <stdio.h> 38 #include <stdlib.h> 39 #include <string.h> 40 #include <sysexits.h> 41 #include <unistd.h> 42 43 #include <libelf.h> 44 #include <libelftc.h> 45 #include <gelf.h> 46 47 #include "_elftc.h" 48 49 ELFTC_VCSID("$Id: strings.c 3648 2018-11-22 23:26:43Z emaste $"); 50 51 enum radix_style { 52 RADIX_DECIMAL, 53 RADIX_HEX, 54 RADIX_OCTAL 55 }; 56 57 enum encoding_style { 58 ENCODING_7BIT, 59 ENCODING_8BIT, 60 ENCODING_16BIT_BIG, 61 ENCODING_16BIT_LITTLE, 62 ENCODING_32BIT_BIG, 63 ENCODING_32BIT_LITTLE 64 }; 65 66 #define PRINTABLE(c) \ 67 ((c) >= 0 && (c) <= 255 && \ 68 ((c) == '\t' || isprint((c)) || \ 69 (encoding == ENCODING_8BIT && (c) > 127))) 70 71 static int encoding_size, entire_file, show_filename, show_loc; 72 static enum encoding_style encoding; 73 static enum radix_style radix; 74 static intmax_t min_len; 75 76 static struct option strings_longopts[] = { 77 { "all", no_argument, NULL, 'a'}, 78 { "bytes", required_argument, NULL, 'n'}, 79 { "encoding", required_argument, NULL, 'e'}, 80 { "help", no_argument, NULL, 'h'}, 81 { "print-file-name", no_argument, NULL, 'f'}, 82 { "radix", required_argument, NULL, 't'}, 83 { "version", no_argument, NULL, 'v'}, 84 { NULL, 0, NULL, 0 } 85 }; 86 87 long getcharacter(void); 88 int handle_file(const char *); 89 int handle_elf(const char *, int); 90 int handle_binary(const char *, int); 91 int find_strings(const char *, off_t, off_t); 92 void show_version(void); 93 void usage(void); 94 95 /* 96 * strings(1) extracts text(contiguous printable characters) 97 * from elf and binary files. 98 */ 99 int 100 main(int argc, char **argv) 101 { 102 int ch, rc; 103 104 rc = 0; 105 min_len = 0; 106 encoding_size = 1; 107 if (elf_version(EV_CURRENT) == EV_NONE) 108 errx(EXIT_FAILURE, "ELF library initialization failed: %s", 109 elf_errmsg(-1)); 110 111 while ((ch = getopt_long(argc, argv, "1234567890ae:fhn:ot:Vv", 112 strings_longopts, NULL)) != -1) { 113 switch ((char)ch) { 114 case 'a': 115 entire_file = 1; 116 break; 117 case 'e': 118 if (*optarg == 's') { 119 encoding = ENCODING_7BIT; 120 } else if (*optarg == 'S') { 121 encoding = ENCODING_8BIT; 122 } else if (*optarg == 'b') { 123 encoding = ENCODING_16BIT_BIG; 124 encoding_size = 2; 125 } else if (*optarg == 'B') { 126 encoding = ENCODING_32BIT_BIG; 127 encoding_size = 4; 128 } else if (*optarg == 'l') { 129 encoding = ENCODING_16BIT_LITTLE; 130 encoding_size = 2; 131 } else if (*optarg == 'L') { 132 encoding = ENCODING_32BIT_LITTLE; 133 encoding_size = 4; 134 } else 135 usage(); 136 /* NOTREACHED */ 137 break; 138 case 'f': 139 show_filename = 1; 140 break; 141 case 'n': 142 min_len = strtoimax(optarg, (char**)NULL, 10); 143 if (min_len <= 0) 144 errx(EX_USAGE, "option -n should specify a " 145 "positive decimal integer."); 146 break; 147 case 'o': 148 show_loc = 1; 149 radix = RADIX_OCTAL; 150 break; 151 case 't': 152 show_loc = 1; 153 if (*optarg == 'd') 154 radix = RADIX_DECIMAL; 155 else if (*optarg == 'o') 156 radix = RADIX_OCTAL; 157 else if (*optarg == 'x') 158 radix = RADIX_HEX; 159 else 160 usage(); 161 /* NOTREACHED */ 162 break; 163 case 'v': 164 case 'V': 165 show_version(); 166 /* NOTREACHED */ 167 case '0': 168 case '1': 169 case '2': 170 case '3': 171 case '4': 172 case '5': 173 case '6': 174 case '7': 175 case '8': 176 case '9': 177 min_len *= 10; 178 min_len += ch - '0'; 179 break; 180 case 'h': 181 case '?': 182 default: 183 usage(); 184 /* NOTREACHED */ 185 } 186 } 187 argc -= optind; 188 argv += optind; 189 190 if (min_len == 0) 191 min_len = 4; 192 if (*argv == NULL) 193 rc = find_strings("{standard input}", 0, 0); 194 else while (*argv != NULL) { 195 if (handle_file(*argv) != 0) 196 rc = 1; 197 argv++; 198 } 199 return (rc); 200 } 201 202 int 203 handle_file(const char *name) 204 { 205 int fd, rt; 206 207 if (name == NULL) 208 return (1); 209 if (freopen(name, "rb", stdin) == NULL) { 210 warnx("'%s': %s", name, strerror(errno)); 211 return (1); 212 } 213 214 fd = fileno(stdin); 215 if (fd < 0) 216 return (1); 217 rt = handle_elf(name, fd); 218 return (rt); 219 } 220 221 /* 222 * Files not understood by handle_elf, will be passed off here and will 223 * treated as a binary file. This would include text file, core dumps ... 224 */ 225 int 226 handle_binary(const char *name, int fd) 227 { 228 struct stat buf; 229 230 memset(&buf, 0, sizeof(buf)); 231 (void)lseek(fd, 0, SEEK_SET); 232 if (!fstat(fd, &buf)) 233 return (find_strings(name, 0, buf.st_size)); 234 return (1); 235 } 236 237 /* 238 * Will analyse a file to see if it ELF, other files including ar(1), 239 * core dumps are passed off and treated as flat binary files. Unlike 240 * GNU size in FreeBSD this routine will not treat ELF object from 241 * different archs as flat binary files(has to overridden using -a). 242 */ 243 int 244 handle_elf(const char *name, int fd) 245 { 246 GElf_Ehdr elfhdr; 247 GElf_Shdr shdr; 248 Elf *elf; 249 Elf_Scn *scn; 250 int rc; 251 252 rc = 0; 253 /* If entire file is chosen, treat it as a binary file */ 254 if (entire_file) 255 return (handle_binary(name, fd)); 256 257 (void)lseek(fd, 0, SEEK_SET); 258 elf = elf_begin(fd, ELF_C_READ, NULL); 259 if (elf_kind(elf) != ELF_K_ELF) { 260 (void)elf_end(elf); 261 return (handle_binary(name, fd)); 262 } 263 264 if (gelf_getehdr(elf, &elfhdr) == NULL) { 265 (void)elf_end(elf); 266 warnx("%s: ELF file could not be processed", name); 267 return (1); 268 } 269 270 if (elfhdr.e_shnum == 0 && elfhdr.e_type == ET_CORE) { 271 (void)elf_end(elf); 272 return (handle_binary(name, fd)); 273 } else { 274 scn = NULL; 275 while ((scn = elf_nextscn(elf, scn)) != NULL) { 276 if (gelf_getshdr(scn, &shdr) == NULL) 277 continue; 278 if (shdr.sh_type != SHT_NOBITS && 279 (shdr.sh_flags & SHF_ALLOC) != 0) { 280 rc = find_strings(name, shdr.sh_offset, 281 shdr.sh_size); 282 } 283 } 284 } 285 (void)elf_end(elf); 286 return (rc); 287 } 288 289 /* 290 * Retrieves a character from input stream based on the encoding 291 * type requested. 292 */ 293 long 294 getcharacter(void) 295 { 296 long rt; 297 int i; 298 char buf[4], c; 299 300 rt = EOF; 301 for(i = 0; i < encoding_size; i++) { 302 c = getc(stdin); 303 if (feof(stdin)) 304 return (EOF); 305 buf[i] = c; 306 } 307 308 switch (encoding) { 309 case ENCODING_7BIT: 310 case ENCODING_8BIT: 311 rt = buf[0]; 312 break; 313 case ENCODING_16BIT_BIG: 314 rt = (buf[0] << 8) | buf[1]; 315 break; 316 case ENCODING_16BIT_LITTLE: 317 rt = buf[0] | (buf[1] << 8); 318 break; 319 case ENCODING_32BIT_BIG: 320 rt = ((long) buf[0] << 24) | ((long) buf[1] << 16) | 321 ((long) buf[2] << 8) | buf[3]; 322 break; 323 case ENCODING_32BIT_LITTLE: 324 rt = buf[0] | ((long) buf[1] << 8) | ((long) buf[2] << 16) | 325 ((long) buf[3] << 24); 326 break; 327 } 328 return (rt); 329 } 330 331 /* 332 * Input stream stdin is read until the end of file is reached or until 333 * the section size is reached in case of ELF files. Contiguous 334 * characters of >= min_size(default 4) will be displayed. 335 */ 336 int 337 find_strings(const char *name, off_t offset, off_t size) 338 { 339 off_t cur_off, start_off; 340 char *obuf; 341 long c; 342 int i; 343 344 if ((obuf = (char*)calloc(1, min_len + 1)) == NULL) { 345 fprintf(stderr, "Unable to allocate memory: %s\n", 346 strerror(errno)); 347 return (1); 348 } 349 350 (void)fseeko(stdin, offset, SEEK_SET); 351 cur_off = offset; 352 start_off = 0; 353 for (;;) { 354 if ((offset + size) && (cur_off >= offset + size)) 355 break; 356 start_off = cur_off; 357 memset(obuf, 0, min_len + 1); 358 for(i = 0; i < min_len; i++) { 359 c = getcharacter(); 360 if (c == EOF && feof(stdin)) 361 goto _exit1; 362 if (PRINTABLE(c)) { 363 obuf[i] = c; 364 obuf[i + 1] = 0; 365 cur_off += encoding_size; 366 } else { 367 if (encoding == ENCODING_8BIT && 368 (uint8_t)c > 127) { 369 obuf[i] = c; 370 obuf[i + 1] = 0; 371 cur_off += encoding_size; 372 continue; 373 } 374 cur_off += encoding_size; 375 break; 376 } 377 } 378 379 if (i >= min_len && ((cur_off <= offset + size) || 380 !(offset + size))) { 381 if (show_filename) 382 printf("%s: ", name); 383 if (show_loc) { 384 switch (radix) { 385 case RADIX_DECIMAL: 386 printf("%7ju ", (uintmax_t)start_off); 387 break; 388 case RADIX_HEX: 389 printf("%7jx ", (uintmax_t)start_off); 390 break; 391 case RADIX_OCTAL: 392 printf("%7jo ", (uintmax_t)start_off); 393 break; 394 } 395 } 396 printf("%s", obuf); 397 398 for (;;) { 399 if ((offset + size) && 400 (cur_off >= offset + size)) 401 break; 402 c = getcharacter(); 403 cur_off += encoding_size; 404 if (encoding == ENCODING_8BIT && 405 (uint8_t)c > 127) { 406 putchar(c); 407 continue; 408 } 409 if (!PRINTABLE(c) || c == EOF) 410 break; 411 putchar(c); 412 } 413 putchar('\n'); 414 } 415 } 416 _exit1: 417 free(obuf); 418 return (0); 419 } 420 421 #define USAGE_MESSAGE "\ 422 Usage: %s [options] [file...]\n\ 423 Print contiguous sequences of printable characters.\n\n\ 424 Options:\n\ 425 -a | --all Scan the entire file for strings.\n\ 426 -e ENC | --encoding=ENC Select the character encoding to use.\n\ 427 -f | --print-file-name Print the file name before each string.\n\ 428 -h | --help Print a help message and exit.\n\ 429 -n N | --bytes=N | -N Print sequences with 'N' or more characters.\n\ 430 -o Print offsets in octal.\n\ 431 -t R | --radix=R Print offsets using the radix named by 'R'.\n\ 432 -v | --version Print a version identifier and exit.\n" 433 434 void 435 usage(void) 436 { 437 438 fprintf(stderr, USAGE_MESSAGE, ELFTC_GETPROGNAME()); 439 exit(EXIT_FAILURE); 440 } 441 442 void 443 show_version(void) 444 { 445 446 printf("%s (%s)\n", ELFTC_GETPROGNAME(), elftc_version()); 447 exit(EXIT_SUCCESS); 448 } 449