env/envopts.c

   1 /*-
   2  * Copyright (c) 2005  - Garance Alistair Drosehn <gad@FreeBSD.org>.
   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  * The views and conclusions contained in the software and documentation
  27  * are those of the authors and should not be interpreted as representing
  28  * official policies, either expressed or implied, of the FreeBSD Project.
  29  */
  30
  31 #include <sys/cdefs.h>
  32 __FBSDID("$FreeBSD$");
  33
  34 #include <sys/stat.h>
  35 #include <sys/param.h>
  36 #include <err.h>
  37 #include <errno.h>
  38 #include <ctype.h>
  39 #include <stdio.h>
  40 #include <stdlib.h>
  41 #include <string.h>
  42 #include <unistd.h>
  43
  44 #include "envopts.h"
  45
  46 static const char *
  47                  expand_vars(int in_thisarg, char **thisarg_p, char **dest_p,
  48                      const char **src_p);
  49 static int       is_there(char *candidate);
  50
  51 /*
  52  * The is*() routines take a parameter of 'int', but expect values in the range
  53  * of unsigned char.  Define some wrappers which take a value of type 'char',
  54  * whether signed or unsigned, and ensure the value ends up in the right range.
  55  */
  56 #define isalnumch(Anychar) isalnum((u_char)(Anychar))
  57 #define isalphach(Anychar) isalpha((u_char)(Anychar))
  58 #define isspacech(Anychar) isspace((u_char)(Anychar))
  59
  60 /*
  61  * Routine to determine if a given fully-qualified filename is executable.
  62  * This is copied almost verbatim from FreeBSD's usr.bin/which/which.c.
  63  */
  64 static int
  65 is_there(char *candidate)
  66 {
  67         struct stat fin;
  68
  69         /* XXX work around access(2) false positives for superuser */
  70         if (access(candidate, X_OK) == 0 &&
  71             stat(candidate, &fin) == 0 &&
  72             S_ISREG(fin.st_mode) &&
  73             (getuid() != 0 ||
  74             (fin.st_mode & (S_IXUSR | S_IXGRP | S_IXOTH)) != 0)) {
  75                 if (env_verbosity > 1)
  76                         fprintf(stderr, "#env   matched:\t'%s'\n", candidate);
  77                 return (1);
  78         }
  79         return (0);
  80 }
  81
  82 /**
  83  * Routine to search through an alternate path-list, looking for a given
  84  * filename to execute.  If the file is found, replace the original
  85  * unqualified name with a fully-qualified path.  This allows `env' to
  86  * execute programs from a specific strict list of possible paths, without
  87  * changing the value of PATH seen by the program which will be executed.
  88  * E.G.:
  89  *      #!/usr/bin/env -S-P/usr/local/bin:/usr/bin perl
  90  * will execute /usr/local/bin/perl or /usr/bin/perl (whichever is found
  91  * first), no matter what the current value of PATH is, and without
  92  * changing the value of PATH that the script will see when it runs.
  93  *
  94  * This is similar to the print_matches() routine in usr.bin/which/which.c.
  95  */
  96 void
  97 search_paths(char *path, char **argv)
  98 {
  99         char candidate[PATH_MAX];
 100         const char *d;
 101         char *filename, *fqname;
 102
 103         /* If the file has a `/' in it, then no search is done */
 104         filename = *argv;
 105         if (strchr(filename, '/') != NULL)
 106                 return;
 107
 108         if (env_verbosity > 1) {
 109                 fprintf(stderr, "#env Searching:\t'%s'\n", path);
 110                 fprintf(stderr, "#env  for file:\t'%s'\n", filename);
 111         }
 112
 113         fqname = NULL;
 114         while ((d = strsep(&path, ":")) != NULL) {
 115                 if (*d == '\0')
 116                         d = ".";
 117                 if (snprintf(candidate, sizeof(candidate), "%s/%s", d,
 118                     filename) >= (int)sizeof(candidate))
 119                         continue;
 120                 if (is_there(candidate)) {
 121                         fqname = candidate;
 122                         break;
 123                 }
 124         }
 125
 126         if (fqname == NULL) {
 127                 errno = ENOENT;
 128                 err(127, "%s", filename);
 129         }
 130         *argv = strdup(candidate);
 131 }
 132
 133 /**
 134  * Routine to split a string into multiple parameters, while recognizing a
 135  * few special characters.  It recognizes both single and double-quoted
 136  * strings.  This processing is designed entirely for the benefit of the
 137  * parsing of "#!"-lines (aka "shebang" lines == the first line of an
 138  * executable script).  Different operating systems parse that line in very
 139  * different ways, and this split-on-spaces processing is meant to provide
 140  * ways to specify arbitrary arguments on that line, no matter how the OS
 141  * parses it.
 142  *
 143  * Within a single-quoted string, the two characters "\'" are treated as
 144  * a literal "'" character to add to the string, and "\\" are treated as
 145  * a literal "\" character to add.  Other than that, all characters are
 146  * copied until the processing gets to a terminating "'".
 147  *
 148  * Within a double-quoted string, many more "\"-style escape sequences
 149  * are recognized, mostly copied from what is recognized in the `printf'
 150  * command.  Some OS's will not allow a literal blank character to be
 151  * included in the one argument that they recognize on a shebang-line,
 152  * so a few additional escape-sequences are defined to provide ways to
 153  * specify blanks.
 154  *
 155  * Within a double-quoted string "\_" is turned into a literal blank.
 156  * (Inside of a single-quoted string, the two characters are just copied)
 157  * Outside of a quoted string, "\_" is treated as both a blank, and the
 158  * end of the current argument.  So with a shelbang-line of:
 159  *              #!/usr/bin/env -SA=avalue\_perl
 160  * the -S value would be broken up into arguments "A=avalue" and "perl".
 161  */
 162 void
 163 split_spaces(const char *str, int *origind, int *origc, char ***origv)
 164 {
 165         static const char *nullarg = "";
 166         const char *bq_src, *copystr, *src;
 167         char *dest, **newargv, *newstr, **nextarg, **oldarg;
 168         int addcount, bq_destlen, copychar, found_sep, in_arg, in_dq, in_sq;
 169
 170         /*
 171          * Ignore leading space on the string, and then malloc enough room
 172          * to build a copy of it.  The copy might end up shorter than the
 173          * original, due to quoted strings and '\'-processing.
 174          */
 175         while (isspacech(*str))
 176                 str++;
 177         if (*str == '\0')
 178                 return;
 179         newstr = malloc(strlen(str) + 1);
 180
 181         /*
 182          * Allocate plenty of space for the new array of arg-pointers,
 183          * and start that array off with the first element of the old
 184          * array.
 185          */
 186         newargv = malloc((*origc + (strlen(str) / 2) + 2) * sizeof(char *));
 187         nextarg = newargv;
 188         *nextarg++ = **origv;
 189
 190         /* Come up with the new args by splitting up the given string. */
 191         addcount = 0;
 192         bq_destlen = in_arg = in_dq = in_sq = 0;
 193         bq_src = NULL;
 194         for (src = str, dest = newstr; *src != '\0'; src++) {
 195                 /*
 196                  * This switch will look at a character in *src, and decide
 197                  * what should be copied to *dest.  It only decides what
 198                  * character(s) to copy, it should not modify *dest.  In some
 199                  * cases, it will look at multiple characters from *src.
 200                  */
 201                 copychar = found_sep = 0;
 202                 copystr = NULL;
 203                 switch (*src) {
 204                 case '"':
 205                         if (in_sq)
 206                                 copychar = *src;
 207                         else if (in_dq)
 208                                 in_dq = 0;
 209                         else {
 210                                 /*
 211                                  * Referencing nullarg ensures that a new
 212                                  * argument is created, even if this quoted
 213                                  * string ends up with zero characters.
 214                                  */
 215                                 copystr = nullarg;
 216                                 in_dq = 1;
 217                                 bq_destlen = dest - *(nextarg - 1);
 218                                 bq_src = src;
 219                         }
 220                         break;
 221                 case '$':
 222                         if (in_sq)
 223                                 copychar = *src;
 224                         else {
 225                                 copystr = expand_vars(in_arg, (nextarg - 1),
 226                                     &dest, &src);
 227                         }
 228                         break;
 229                 case '\'':
 230                         if (in_dq)
 231                                 copychar = *src;
 232                         else if (in_sq)
 233                                 in_sq = 0;
 234                         else {
 235                                 /*
 236                                  * Referencing nullarg ensures that a new
 237                                  * argument is created, even if this quoted
 238                                  * string ends up with zero characters.
 239                                  */
 240                                 copystr = nullarg;
 241                                 in_sq = 1;
 242                                 bq_destlen = dest - *(nextarg - 1);
 243                                 bq_src = src;
 244                         }
 245                         break;
 246                 case '\\':
 247                         if (in_sq) {
 248                                 /*
 249                                  * Inside single-quoted strings, only the
 250                                  * "\'" and "\\" are recognized as special
 251                                  * strings.
 252                                  */
 253                                 copychar = *(src + 1);
 254                                 if (copychar == '\'' || copychar == '\\')
 255                                         src++;
 256                                 else
 257                                         copychar = *src;
 258                                 break;
 259                         }
 260                         src++;
 261                         switch (*src) {
 262                         case '"':
 263                         case '#':
 264                         case '$':
 265                         case '\'':
 266                         case '\\':
 267                                 copychar = *src;
 268                                 break;
 269                         case '_':
 270                                 /*
 271                                  * Alternate way to get a blank, which allows
 272                                  * that blank be used to separate arguments
 273                                  * when it is not inside a quoted string.
 274                                  */
 275                                 if (in_dq)
 276                                         copychar = ' ';
 277                                 else {
 278                                         found_sep = 1;
 279                                         src++;
 280                                 }
 281                                 break;
 282                         case 'c':
 283                                 /*
 284                                  * Ignore remaining characters in the -S string.
 285                                  * This would not make sense if found in the
 286                                  * middle of a quoted string.
 287                                  */
 288                                 if (in_dq)
 289                                         errx(1, "Sequence '\\%c' is not allowed"
 290                                             " in quoted strings", *src);
 291                                 goto str_done;
 292                         case 'f':
 293                                 copychar = '\f';
 294                                 break;
 295                         case 'n':
 296                                 copychar = '\n';
 297                                 break;
 298                         case 'r':
 299                                 copychar = '\r';
 300                                 break;
 301                         case 't':
 302                                 copychar = '\t';
 303                                 break;
 304                         case 'v':
 305                                 copychar = '\v';
 306                                 break;
 307                         default:
 308                                 if (isspacech(*src))
 309                                         copychar = *src;
 310                                 else
 311                                         errx(1, "Invalid sequence '\\%c' in -S",
 312                                             *src);
 313                         }
 314                         break;
 315                 default:
 316                         if ((in_dq || in_sq) && in_arg)
 317                                 copychar = *src;
 318                         else if (isspacech(*src))
 319                                 found_sep = 1;
 320                         else {
 321                                 /*
 322                                  * If the first character of a new argument
 323                                  * is `#', then ignore the remaining chars.
 324                                  */
 325                                 if (!in_arg && *src == '#')
 326                                         goto str_done;
 327                                 copychar = *src;
 328                         }
 329                 }
 330                 /*
 331                  * Now that the switch has determined what (if anything)
 332                  * needs to be copied, copy whatever that is to *dest.
 333                  */
 334                 if (copychar || copystr != NULL) {
 335                         if (!in_arg) {
 336                                 /* This is the first byte of a new argument */
 337                                 *nextarg++ = dest;
 338                                 addcount++;
 339                                 in_arg = 1;
 340                         }
 341                         if (copychar)
 342                                 *dest++ = (char)copychar;
 343                         else if (copystr != NULL)
 344                                 while (*copystr != '\0')
 345                                         *dest++ = *copystr++;
 346                 } else if (found_sep) {
 347                         *dest++ = '\0';
 348                         while (isspacech(*src))
 349                                 src++;
 350                         --src;
 351                         in_arg = 0;
 352                 }
 353         }
 354 str_done:
 355         *dest = '\0';
 356         *nextarg = NULL;
 357         if (in_dq || in_sq) {
 358                 errx(1, "No terminating quote for string: %.*s%s",
 359                     bq_destlen, *(nextarg - 1), bq_src);
 360         }
 361         if (env_verbosity > 1) {
 362                 fprintf(stderr, "#env  split -S:\t'%s'\n", str);
 363                 oldarg = newargv + 1;
 364                 fprintf(stderr, "#env      into:\t'%s'\n", *oldarg);
 365                 for (oldarg++; *oldarg; oldarg++)
 366                         fprintf(stderr, "#env          &\t'%s'\n", *oldarg);
 367         }
 368
 369         /* Copy the unprocessed arg-pointers from the original array */
 370         for (oldarg = *origv + *origind; *oldarg; oldarg++)
 371                 *nextarg++ = *oldarg;
 372         *nextarg = NULL;
 373
 374         /* Update optind/argc/argv in the calling routine */
 375         *origind = 1;
 376         *origc += addcount;
 377         *origv = newargv;
 378 }
 379
 380 /**
 381  * Routine to split expand any environment variables referenced in the string
 382  * that -S is processing.  For now it only supports the form ${VARNAME}.  It
 383  * explicitly does not support $VARNAME, and obviously can not handle special
 384  * shell-variables such as $?, $*, $1, etc.  It is called with *src_p pointing
 385  * at the initial '$', and if successful it will update *src_p, *dest_p, and
 386  * possibly *thisarg_p in the calling routine.
 387  */
 388 static const char *
 389 expand_vars(int in_thisarg, char **thisarg_p, char **dest_p, const char **src_p)
 390 {
 391         const char *vbegin, *vend, *vvalue;
 392         char *newstr, *vname;
 393         int bad_reference;
 394         size_t namelen, newlen;
 395
 396         bad_reference = 1;
 397         vbegin = vend = (*src_p) + 1;
 398         if (*vbegin++ == '{')
 399                 if (*vbegin == '_' || isalphach(*vbegin)) {
 400                         vend = vbegin + 1;
 401                         while (*vend == '_' || isalnumch(*vend))
 402                                 vend++;
 403                         if (*vend == '}')
 404                                 bad_reference = 0;
 405                 }
 406         if (bad_reference)
 407                 errx(1, "Only ${VARNAME} expansion is supported, error at: %s",
 408                     *src_p);
 409
 410         /*
 411          * We now know we have a valid environment variable name, so update
 412          * the caller's source-pointer to the last character in that reference,
 413          * and then pick up the matching value.  If the variable is not found,
 414          * or if it has a null value, then our work here is done.
 415          */
 416         *src_p = vend;
 417         namelen = vend - vbegin + 1;
 418         vname = malloc(namelen);
 419         strlcpy(vname, vbegin, namelen);
 420         vvalue = getenv(vname);
 421         if (vvalue == NULL || *vvalue == '\0') {
 422                 if (env_verbosity > 2)
 423                         fprintf(stderr,
 424                             "#env  replacing ${%s} with null string\n",
 425                             vname);
 426                 free(vname);
 427                 return (NULL);
 428         }
 429
 430         if (env_verbosity > 2)
 431                 fprintf(stderr, "#env  expanding ${%s} into '%s'\n", vname,
 432                     vvalue);
 433
 434         /*
 435          * There is some value to copy to the destination.  If the value is
 436          * shorter than the ${VARNAME} reference that it replaces, then our
 437          * caller can just copy the value to the existing destination.
 438          */
 439         if (strlen(vname) + 3 >= strlen(vvalue)) {
 440                 free(vname);
 441                 return (vvalue);
 442         }
 443
 444         /*
 445          * The value is longer than the string it replaces, which means the
 446          * present destination area is too small to hold it.  Create a new
 447          * destination area, and update the caller's 'dest' variable to match.
 448          * If the caller has already started copying some info for 'thisarg'
 449          * into the present destination, then the new destination area must
 450          * include a copy of that data, and the pointer to 'thisarg' must also
 451          * be updated.  Note that it is still the caller which copies this
 452          * vvalue to the new *dest.
 453          */
 454         newlen = strlen(vvalue) + strlen(*src_p) + 1;
 455         if (in_thisarg) {
 456                 **dest_p = '\0';        /* Provide terminator for 'thisarg' */
 457                 newlen += strlen(*thisarg_p);
 458                 newstr = malloc(newlen);
 459                 strcpy(newstr, *thisarg_p);
 460                 *thisarg_p = newstr;
 461         } else {
 462                 newstr = malloc(newlen);
 463                 *newstr = '\0';
 464         }
 465         *dest_p = strchr(newstr, '\0');
 466         free(vname);
 467         return (vvalue);
 468 }