pkgs/build-support/libredirect/libredirect.c

   1 #define _GNU_SOURCE
   2 #include <stdio.h>
   3 #include <stdarg.h>
   4 #include <stdlib.h>
   5 #include <unistd.h>
   6 #include <dlfcn.h>
   7 #include <sys/types.h>
   8 #include <sys/stat.h>
   9 #include <fcntl.h>
  10 #include <limits.h>
  11 #include <string.h>
  12 #include <spawn.h>
  13 #include <dirent.h>
  14
  15 #define MAX_REDIRECTS 128
  16
  17 #ifdef __APPLE__
  18   struct dyld_interpose {
  19     const void * replacement;
  20     const void * replacee;
  21   };
  22   #define WRAPPER(ret, name) static ret _libredirect_wrapper_##name
  23   #define LOOKUP_REAL(name) &name
  24   #define WRAPPER_DEF(name) \
  25     __attribute__((used)) static struct dyld_interpose _libredirect_interpose_##name \
  26       __attribute__((section("__DATA,__interpose"))) = { &_libredirect_wrapper_##name, &name };
  27 #else
  28   #define WRAPPER(ret, name) ret name
  29   #define LOOKUP_REAL(name) dlsym(RTLD_NEXT, #name)
  30   #define WRAPPER_DEF(name)
  31 #endif
  32
  33 static int nrRedirects = 0;
  34 static char * from[MAX_REDIRECTS];
  35 static char * to[MAX_REDIRECTS];
  36
  37 static int isInitialized = 0;
  38
  39 // FIXME: might run too late.
  40 static void init() __attribute__((constructor));
  41
  42 static void init()
  43 {
  44     if (isInitialized) return;
  45
  46     char * spec = getenv("NIX_REDIRECTS");
  47     if (!spec) return;
  48
  49     // Ensure we only run this code once.
  50     // We do not do `unsetenv("NIX_REDIRECTS")` to ensure that redirects
  51     // also get initialized for subprocesses.
  52     isInitialized = 1;
  53
  54     char * spec2 = malloc(strlen(spec) + 1);
  55     strcpy(spec2, spec);
  56
  57     char * pos = spec2, * eq;
  58     while ((eq = strchr(pos, '='))) {
  59         *eq = 0;
  60         from[nrRedirects] = pos;
  61         pos = eq + 1;
  62         to[nrRedirects] = pos;
  63         nrRedirects++;
  64         if (nrRedirects == MAX_REDIRECTS) break;
  65         char * end = strchr(pos, ':');
  66         if (!end) break;
  67         *end = 0;
  68         pos = end + 1;
  69     }
  70
  71 }
  72
  73 static const char * rewrite(const char * volatile path, char * buf)
  74 {
  75     // Marking the path volatile is needed so the the following check isn't
  76     // optimized away by the compiler.
  77     if (path == NULL) return path;
  78
  79     for (int n = 0; n < nrRedirects; ++n) {
  80         int len = strlen(from[n]);
  81         if (strncmp(path, from[n], len) != 0) continue;
  82         if (snprintf(buf, PATH_MAX, "%s%s", to[n], path + len) >= PATH_MAX)
  83             abort();
  84         return buf;
  85     }
  86
  87     return path;
  88 }
  89
  90 static char * rewrite_non_const(char * path, char * buf)
  91 {
  92     // as long as the argument `path` is non-const, we can consider discarding
  93     // the const qualifier of the return value to be safe.
  94     return (char *)rewrite(path, buf);
  95 }
  96
  97 static int open_needs_mode(int flags)
  98 {
  99 #ifdef O_TMPFILE
 100     return (flags & O_CREAT) || (flags & O_TMPFILE) == O_TMPFILE;
 101 #else
 102     return flags & O_CREAT;
 103 #endif
 104 }
 105
 106 /* The following set of Glibc library functions is very incomplete -
 107    it contains only what we needed for programs in Nixpkgs. Just add
 108    more functions as needed. */
 109
 110 WRAPPER(int, open)(const char * path, int flags, ...)
 111 {
 112     int (*open_real) (const char *, int, ...) = LOOKUP_REAL(open);
 113     mode_t mode = 0;
 114     if (open_needs_mode(flags)) {
 115         va_list ap;
 116         va_start(ap, flags);
 117         mode = va_arg(ap, mode_t);
 118         va_end(ap);
 119     }
 120     char buf[PATH_MAX];
 121     return open_real(rewrite(path, buf), flags, mode);
 122 }
 123 WRAPPER_DEF(open)
 124
 125 // In musl libc, open64 is simply a macro for open
 126 #if !defined(__APPLE__) && !defined(open64)
 127 WRAPPER(int, open64)(const char * path, int flags, ...)
 128 {
 129     int (*open64_real) (const char *, int, mode_t) = LOOKUP_REAL(open64);
 130     mode_t mode = 0;
 131     if (open_needs_mode(flags)) {
 132         va_list ap;
 133         va_start(ap, flags);
 134         mode = va_arg(ap, mode_t);
 135         va_end(ap);
 136     }
 137     char buf[PATH_MAX];
 138     return open64_real(rewrite(path, buf), flags, mode);
 139 }
 140 WRAPPER_DEF(open64)
 141 #endif
 142
 143 WRAPPER(int, openat)(int dirfd, const char * path, int flags, ...)
 144 {
 145     int (*openat_real) (int, const char *, int, ...) = LOOKUP_REAL(openat);
 146     mode_t mode = 0;
 147     if (open_needs_mode(flags)) {
 148         va_list ap;
 149         va_start(ap, flags);
 150         mode = va_arg(ap, mode_t);
 151         va_end(ap);
 152     }
 153     char buf[PATH_MAX];
 154     return openat_real(dirfd, rewrite(path, buf), flags, mode);
 155 }
 156 WRAPPER_DEF(openat)
 157
 158 WRAPPER(FILE *, fopen)(const char * path, const char * mode)
 159 {
 160     FILE * (*fopen_real) (const char *, const char *) = LOOKUP_REAL(fopen);
 161     char buf[PATH_MAX];
 162     return fopen_real(rewrite(path, buf), mode);
 163 }
 164 WRAPPER_DEF(fopen)
 165
 166 #ifdef __GLIBC__
 167 WRAPPER(FILE *, __nss_files_fopen)(const char * path)
 168 {
 169     FILE * (*__nss_files_fopen_real) (const char *) = LOOKUP_REAL(__nss_files_fopen);
 170     char buf[PATH_MAX];
 171     return __nss_files_fopen_real(rewrite(path, buf));
 172 }
 173 WRAPPER_DEF(__nss_files_fopen)
 174 #endif
 175
 176 // In musl libc, fopen64 is simply a macro for fopen
 177 #if !defined(__APPLE__) && !defined(fopen64)
 178 WRAPPER(FILE *, fopen64)(const char * path, const char * mode)
 179 {
 180     FILE * (*fopen64_real) (const char *, const char *) = LOOKUP_REAL(fopen64);
 181     char buf[PATH_MAX];
 182     return fopen64_real(rewrite(path, buf), mode);
 183 }
 184 WRAPPER_DEF(fopen64)
 185 #endif
 186
 187 #ifdef __linux__
 188 WRAPPER(int, __xstat)(int ver, const char * path, struct stat * st)
 189 {
 190     int (*__xstat_real) (int ver, const char *, struct stat *) = LOOKUP_REAL(__xstat);
 191     char buf[PATH_MAX];
 192     return __xstat_real(ver, rewrite(path, buf), st);
 193 }
 194 WRAPPER_DEF(__xstat)
 195 #endif
 196
 197 #ifdef __linux__
 198 WRAPPER(int, __xstat64)(int ver, const char * path, struct stat64 * st)
 199 {
 200     int (*__xstat64_real) (int ver, const char *, struct stat64 *) = LOOKUP_REAL(__xstat64);
 201     char buf[PATH_MAX];
 202     return __xstat64_real(ver, rewrite(path, buf), st);
 203 }
 204 WRAPPER_DEF(__xstat64)
 205 #endif
 206
 207 #if defined(__linux__) && defined(STATX_TYPE)
 208 WRAPPER(int, statx)(int dirfd, const char * restrict pathname, int flags,
 209     unsigned int mask, struct statx * restrict statxbuf)
 210 {
 211     int (*statx_real) (int, const char * restrict, int,
 212         unsigned int, struct statx * restrict) = LOOKUP_REAL(statx);
 213     char buf[PATH_MAX];
 214     return statx_real(dirfd, rewrite(pathname, buf), flags, mask, statxbuf);
 215 }
 216 WRAPPER_DEF(statx)
 217 #endif
 218
 219 WRAPPER(int, fstatat)(int dirfd, const char * pathname, struct stat * statbuf, int flags)
 220 {
 221     int (*fstatat_real) (int, const char *, struct stat *, int) = LOOKUP_REAL(fstatat);
 222     char buf[PATH_MAX];
 223     return fstatat_real(dirfd, rewrite(pathname, buf), statbuf, flags);
 224 }
 225 WRAPPER_DEF(fstatat);
 226
 227 // In musl libc, fstatat64 is simply a macro for fstatat
 228 #if !defined(__APPLE__) && !defined(fstatat64)
 229 WRAPPER(int, fstatat64)(int dirfd, const char * pathname, struct stat64 * statbuf, int flags)
 230 {
 231     int (*fstatat64_real) (int, const char *, struct stat64 *, int) = LOOKUP_REAL(fstatat64);
 232     char buf[PATH_MAX];
 233     return fstatat64_real(dirfd, rewrite(pathname, buf), statbuf, flags);
 234 }
 235 WRAPPER_DEF(fstatat64);
 236 #endif
 237
 238 WRAPPER(int, stat)(const char * path, struct stat * st)
 239 {
 240     int (*__stat_real) (const char *, struct stat *) = LOOKUP_REAL(stat);
 241     char buf[PATH_MAX];
 242     return __stat_real(rewrite(path, buf), st);
 243 }
 244 WRAPPER_DEF(stat)
 245
 246 // In musl libc, stat64 is simply a macro for stat
 247 #if !defined(__APPLE__) && !defined(stat64)
 248 WRAPPER(int, stat64)(const char * path, struct stat64 * st)
 249 {
 250     int (*stat64_real) (const char *, struct stat64 *) = LOOKUP_REAL(stat64);
 251     char buf[PATH_MAX];
 252     return stat64_real(rewrite(path, buf), st);
 253 }
 254 WRAPPER_DEF(stat64)
 255 #endif
 256
 257 WRAPPER(int, access)(const char * path, int mode)
 258 {
 259     int (*access_real) (const char *, int mode) = LOOKUP_REAL(access);
 260     char buf[PATH_MAX];
 261     return access_real(rewrite(path, buf), mode);
 262 }
 263 WRAPPER_DEF(access)
 264
 265 WRAPPER(int, posix_spawn)(pid_t * pid, const char * path,
 266     const posix_spawn_file_actions_t * file_actions,
 267     const posix_spawnattr_t * attrp,
 268     char * const argv[], char * const envp[])
 269 {
 270     int (*posix_spawn_real) (pid_t *, const char *,
 271         const posix_spawn_file_actions_t *,
 272         const posix_spawnattr_t *,
 273         char * const argv[], char * const envp[]) = LOOKUP_REAL(posix_spawn);
 274     char buf[PATH_MAX];
 275     return posix_spawn_real(pid, rewrite(path, buf), file_actions, attrp, argv, envp);
 276 }
 277 WRAPPER_DEF(posix_spawn)
 278
 279 WRAPPER(int, posix_spawnp)(pid_t * pid, const char * file,
 280     const posix_spawn_file_actions_t * file_actions,
 281     const posix_spawnattr_t * attrp,
 282     char * const argv[], char * const envp[])
 283 {
 284     int (*posix_spawnp_real) (pid_t *, const char *,
 285         const posix_spawn_file_actions_t *,
 286         const posix_spawnattr_t *,
 287         char * const argv[], char * const envp[]) = LOOKUP_REAL(posix_spawnp);
 288     char buf[PATH_MAX];
 289     return posix_spawnp_real(pid, rewrite(file, buf), file_actions, attrp, argv, envp);
 290 }
 291 WRAPPER_DEF(posix_spawnp)
 292
 293 WRAPPER(int, execv)(const char * path, char * const argv[])
 294 {
 295     int (*execv_real) (const char * path, char * const argv[]) = LOOKUP_REAL(execv);
 296     char buf[PATH_MAX];
 297     return execv_real(rewrite(path, buf), argv);
 298 }
 299 WRAPPER_DEF(execv)
 300
 301 WRAPPER(int, execvp)(const char * path, char * const argv[])
 302 {
 303     int (*_execvp) (const char *, char * const argv[]) = LOOKUP_REAL(execvp);
 304     char buf[PATH_MAX];
 305     return _execvp(rewrite(path, buf), argv);
 306 }
 307 WRAPPER_DEF(execvp)
 308
 309 WRAPPER(int, execve)(const char * path, char * const argv[], char * const envp[])
 310 {
 311     int (*_execve) (const char *, char * const argv[], char * const envp[]) = LOOKUP_REAL(execve);
 312     char buf[PATH_MAX];
 313     return _execve(rewrite(path, buf), argv, envp);
 314 }
 315 WRAPPER_DEF(execve)
 316
 317 WRAPPER(DIR *, opendir)(const char * path)
 318 {
 319     char buf[PATH_MAX];
 320     DIR * (*_opendir) (const char*) = LOOKUP_REAL(opendir);
 321
 322     return _opendir(rewrite(path, buf));
 323 }
 324 WRAPPER_DEF(opendir)
 325
 326 #define SYSTEM_CMD_MAX 512
 327
 328 static char * replace_substring(char * source, char * buf, char * replace_string, char * start_ptr, char * suffix_ptr) {
 329     char head[SYSTEM_CMD_MAX] = {0};
 330     strncpy(head, source, start_ptr - source);
 331
 332     char tail[SYSTEM_CMD_MAX] = {0};
 333     if(suffix_ptr < source + strlen(source)) {
 334        strcpy(tail, suffix_ptr);
 335     }
 336
 337     sprintf(buf, "%s%s%s", head, replace_string, tail);
 338     return buf;
 339 }
 340
 341 static char * replace_string(char * buf, char * from, char * to) {
 342     int num_matches = 0;
 343     char * matches[SYSTEM_CMD_MAX];
 344     int from_len = strlen(from);
 345     for(int i=0; i<strlen(buf); i++){
 346        char *cmp_start = buf + i;
 347        if(strncmp(from, cmp_start, from_len) == 0){
 348           matches[num_matches] = cmp_start;
 349           num_matches++;
 350        }
 351     }
 352     int len_diff = strlen(to) - strlen(from);
 353     for(int n = 0; n < num_matches; n++) {
 354        char replaced[SYSTEM_CMD_MAX];
 355        replace_substring(buf, replaced, to, matches[n], matches[n]+from_len);
 356        strcpy(buf, replaced);
 357        for(int nn = n+1; nn < num_matches; nn++) {
 358           matches[nn] += len_diff;
 359        }
 360     }
 361     return buf;
 362 }
 363
 364 static void rewriteSystemCall(const char * command, char * buf) {
 365     char * p = buf;
 366
 367     #ifdef __APPLE__
 368     // The dyld environment variable is not inherited by the subprocess spawned
 369     // by system(), so this hack redefines it.
 370     Dl_info info;
 371     dladdr(&rewriteSystemCall, &info);
 372     p = stpcpy(p, "export DYLD_INSERT_LIBRARIES=");
 373     p = stpcpy(p, info.dli_fname);
 374     p = stpcpy(p, ";");
 375     #endif
 376
 377     stpcpy(p, command);
 378
 379     for (int n = 0; n < nrRedirects; ++n) {
 380        replace_string(buf, from[n], to[n]);
 381     }
 382 }
 383
 384 WRAPPER(int, system)(const char *command)
 385 {
 386     int (*_system) (const char*) = LOOKUP_REAL(system);
 387
 388     char newCommand[SYSTEM_CMD_MAX];
 389     rewriteSystemCall(command, newCommand);
 390     return _system(newCommand);
 391 }
 392 WRAPPER_DEF(system)
 393
 394 WRAPPER(int, chdir)(const char *path)
 395 {
 396     int (*chdir_real) (const char *) = LOOKUP_REAL(chdir);
 397     char buf[PATH_MAX];
 398     return chdir_real(rewrite(path, buf));
 399 }
 400 WRAPPER_DEF(chdir);
 401
 402 WRAPPER(int, mkdir)(const char *path, mode_t mode)
 403 {
 404     int (*mkdir_real) (const char *path, mode_t mode) = LOOKUP_REAL(mkdir);
 405     char buf[PATH_MAX];
 406     return mkdir_real(rewrite(path, buf), mode);
 407 }
 408 WRAPPER_DEF(mkdir)
 409
 410 WRAPPER(int, mkdirat)(int dirfd, const char *path, mode_t mode)
 411 {
 412     int (*mkdirat_real) (int dirfd, const char *path, mode_t mode) = LOOKUP_REAL(mkdirat);
 413     char buf[PATH_MAX];
 414     return mkdirat_real(dirfd, rewrite(path, buf), mode);
 415 }
 416 WRAPPER_DEF(mkdirat)
 417
 418 WRAPPER(int, unlink)(const char *path)
 419 {
 420     int (*unlink_real) (const char *path) = LOOKUP_REAL(unlink);
 421     char buf[PATH_MAX];
 422     return unlink_real(rewrite(path, buf));
 423 }
 424 WRAPPER_DEF(unlink)
 425
 426 WRAPPER(int, unlinkat)(int dirfd, const char *path, int flags)
 427 {
 428     int (*unlinkat_real) (int dirfd, const char *path, int flags) = LOOKUP_REAL(unlinkat);
 429     char buf[PATH_MAX];
 430     return unlinkat_real(dirfd, rewrite(path, buf), flags);
 431 }
 432 WRAPPER_DEF(unlinkat)
 433
 434 WRAPPER(int, rmdir)(const char *path)
 435 {
 436     int (*rmdir_real) (const char *path) = LOOKUP_REAL(rmdir);
 437     char buf[PATH_MAX];
 438     return rmdir_real(rewrite(path, buf));
 439 }
 440 WRAPPER_DEF(rmdir)
 441
 442 static void copy_temp_wildcard(char * dest, char * src, int suffixlen) {
 443     int dest_len = strnlen(dest, PATH_MAX);
 444     int src_len = strnlen(src, PATH_MAX);
 445     memcpy(dest + dest_len - (6 + suffixlen), src + src_len - (6 + suffixlen), 6);
 446 }
 447
 448 WRAPPER(int, mkstemp)(char *template)
 449 {
 450     int (*mkstemp_real) (char *template) = LOOKUP_REAL(mkstemp);
 451     char buf[PATH_MAX];
 452     char * rewritten = rewrite_non_const(template, buf);
 453     int retval = mkstemp_real(rewritten);
 454     if (retval >= 0 && rewritten != template) {
 455         copy_temp_wildcard(template, rewritten, 0);
 456     }
 457     return retval;
 458 }
 459 WRAPPER_DEF(mkstemp)
 460
 461 WRAPPER(int, mkostemp)(char *template, int flags)
 462 {
 463     int (*mkostemp_real) (char *template, int flags) = LOOKUP_REAL(mkostemp);
 464     char buf[PATH_MAX];
 465     char * rewritten = rewrite_non_const(template, buf);
 466     int retval = mkostemp_real(rewritten, flags);
 467     if (retval >= 0 && rewritten != template) {
 468         copy_temp_wildcard(template, rewritten, 0);
 469     }
 470     return retval;
 471 }
 472 WRAPPER_DEF(mkostemp)
 473
 474 WRAPPER(int, mkstemps)(char *template, int suffixlen)
 475 {
 476     int (*mkstemps_real) (char *template, int suffixlen) = LOOKUP_REAL(mkstemps);
 477     char buf[PATH_MAX];
 478     char * rewritten = rewrite_non_const(template, buf);
 479     int retval = mkstemps_real(rewritten, suffixlen);
 480     if (retval >= 0 && rewritten != template) {
 481         copy_temp_wildcard(template, rewritten, suffixlen);
 482     }
 483     return retval;
 484 }
 485 WRAPPER_DEF(mkstemps)
 486
 487 WRAPPER(int, mkostemps)(char *template, int suffixlen, int flags)
 488 {
 489     int (*mkostemps_real) (char *template, int suffixlen, int flags) = LOOKUP_REAL(mkostemps);
 490     char buf[PATH_MAX];
 491     char * rewritten = rewrite_non_const(template, buf);
 492     int retval = mkostemps_real(rewritten, suffixlen, flags);
 493     if (retval >= 0 && rewritten != template) {
 494         copy_temp_wildcard(template, rewritten, suffixlen);
 495     }
 496     return retval;
 497 }
 498 WRAPPER_DEF(mkostemps)
 499
 500 WRAPPER(char *, mkdtemp)(char *template)
 501 {
 502     char * (*mkdtemp_real) (char *template) = LOOKUP_REAL(mkdtemp);
 503     char buf[PATH_MAX];
 504     char * rewritten = rewrite_non_const(template, buf);
 505     char * retval = mkdtemp_real(rewritten);
 506     if (retval == NULL) {
 507         return retval;
 508     };
 509     if (rewritten != template) {
 510         copy_temp_wildcard(template, rewritten, 0);
 511     }
 512     return template;
 513 }
 514 WRAPPER_DEF(mkdtemp)
 515
 516 WRAPPER(char *, mktemp)(char *template)
 517 {
 518     char * (*mktemp_real) (char *template) = LOOKUP_REAL(mktemp);
 519     char buf[PATH_MAX];
 520     char * rewritten = rewrite_non_const(template, buf);
 521     char * retval = mktemp_real(rewritten);
 522     if (retval == NULL) {
 523         return retval;
 524     };
 525     if (rewritten != template) {
 526         copy_temp_wildcard(template, rewritten, 0);
 527     }
 528     return template;
 529 }
 530 WRAPPER_DEF(mktemp)