src/compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors_format.inc

   1 //===-- sanitizer_common_interceptors_format.inc ----------------*- C++ -*-===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // Scanf/printf implementation for use in *Sanitizer interceptors.
  11 // Follows http://pubs.opengroup.org/onlinepubs/9699919799/functions/fscanf.html
  12 // and http://pubs.opengroup.org/onlinepubs/9699919799/functions/fprintf.html
  13 // with a few common GNU extensions.
  14 //
  15 //===----------------------------------------------------------------------===//
  16
  17 #include <stdarg.h>
  18
  19 static const char *parse_number(const char *p, int *out) {
  20   *out = internal_atoll(p);
  21   while (*p >= '0' && *p <= '9')
  22     ++p;
  23   return p;
  24 }
  25
  26 static const char *maybe_parse_param_index(const char *p, int *out) {
  27   // n$
  28   if (*p >= '0' && *p <= '9') {
  29     int number;
  30     const char *q = parse_number(p, &number);
  31     CHECK(q);
  32     if (*q == '$') {
  33       *out = number;
  34       p = q + 1;
  35     }
  36   }
  37
  38   // Otherwise, do not change p. This will be re-parsed later as the field
  39   // width.
  40   return p;
  41 }
  42
  43 static bool char_is_one_of(char c, const char *s) {
  44   return !!internal_strchr(s, c);
  45 }
  46
  47 static const char *maybe_parse_length_modifier(const char *p, char ll[2]) {
  48   if (char_is_one_of(*p, "jztLq")) {
  49     ll[0] = *p;
  50     ++p;
  51   } else if (*p == 'h') {
  52     ll[0] = 'h';
  53     ++p;
  54     if (*p == 'h') {
  55       ll[1] = 'h';
  56       ++p;
  57     }
  58   } else if (*p == 'l') {
  59     ll[0] = 'l';
  60     ++p;
  61     if (*p == 'l') {
  62       ll[1] = 'l';
  63       ++p;
  64     }
  65   }
  66   return p;
  67 }
  68
  69 // Returns true if the character is an integer conversion specifier.
  70 static bool format_is_integer_conv(char c) {
  71   return char_is_one_of(c, "diouxXn");
  72 }
  73
  74 // Returns true if the character is an floating point conversion specifier.
  75 static bool format_is_float_conv(char c) {
  76   return char_is_one_of(c, "aAeEfFgG");
  77 }
  78
  79 // Returns string output character size for string-like conversions,
  80 // or 0 if the conversion is invalid.
  81 static int format_get_char_size(char convSpecifier,
  82                                 const char lengthModifier[2]) {
  83   if (char_is_one_of(convSpecifier, "CS")) {
  84     return sizeof(wchar_t);
  85   }
  86
  87   if (char_is_one_of(convSpecifier, "cs[")) {
  88     if (lengthModifier[0] == 'l' && lengthModifier[1] == '\0')
  89       return sizeof(wchar_t);
  90     else if (lengthModifier[0] == '\0')
  91       return sizeof(char);
  92   }
  93
  94   return 0;
  95 }
  96
  97 enum FormatStoreSize {
  98   // Store size not known in advance; can be calculated as wcslen() of the
  99   // destination buffer.
 100   FSS_WCSLEN = -2,
 101   // Store size not known in advance; can be calculated as strlen() of the
 102   // destination buffer.
 103   FSS_STRLEN = -1,
 104   // Invalid conversion specifier.
 105   FSS_INVALID = 0
 106 };
 107
 108 // Returns the memory size of a format directive (if >0), or a value of
 109 // FormatStoreSize.
 110 static int format_get_value_size(char convSpecifier,
 111                                  const char lengthModifier[2],
 112                                  bool promote_float) {
 113   if (format_is_integer_conv(convSpecifier)) {
 114     switch (lengthModifier[0]) {
 115     case 'h':
 116       return lengthModifier[1] == 'h' ? sizeof(char) : sizeof(short);
 117     case 'l':
 118       return lengthModifier[1] == 'l' ? sizeof(long long) : sizeof(long);
 119     case 'q':
 120       return sizeof(long long);
 121     case 'L':
 122       return sizeof(long long);
 123     case 'j':
 124       return sizeof(INTMAX_T);
 125     case 'z':
 126       return sizeof(SIZE_T);
 127     case 't':
 128       return sizeof(PTRDIFF_T);
 129     case 0:
 130       return sizeof(int);
 131     default:
 132       return FSS_INVALID;
 133     }
 134   }
 135
 136   if (format_is_float_conv(convSpecifier)) {
 137     switch (lengthModifier[0]) {
 138     case 'L':
 139     case 'q':
 140       return sizeof(long double);
 141     case 'l':
 142       return lengthModifier[1] == 'l' ? sizeof(long double)
 143                                            : sizeof(double);
 144     case 0:
 145       // Printf promotes floats to doubles but scanf does not
 146       return promote_float ? sizeof(double) : sizeof(float);
 147     default:
 148       return FSS_INVALID;
 149     }
 150   }
 151
 152   if (convSpecifier == 'p') {
 153     if (lengthModifier[0] != 0)
 154       return FSS_INVALID;
 155     return sizeof(void *);
 156   }
 157
 158   return FSS_INVALID;
 159 }
 160
 161 struct ScanfDirective {
 162   int argIdx; // argument index, or -1 if not specified ("%n$")
 163   int fieldWidth;
 164   const char *begin;
 165   const char *end;
 166   bool suppressed; // suppress assignment ("*")
 167   bool allocate;   // allocate space ("m")
 168   char lengthModifier[2];
 169   char convSpecifier;
 170   bool maybeGnuMalloc;
 171 };
 172
 173 // Parse scanf format string. If a valid directive in encountered, it is
 174 // returned in dir. This function returns the pointer to the first
 175 // unprocessed character, or 0 in case of error.
 176 // In case of the end-of-string, a pointer to the closing \0 is returned.
 177 static const char *scanf_parse_next(const char *p, bool allowGnuMalloc,
 178                                     ScanfDirective *dir) {
 179   internal_memset(dir, 0, sizeof(*dir));
 180   dir->argIdx = -1;
 181
 182   while (*p) {
 183     if (*p != '%') {
 184       ++p;
 185       continue;
 186     }
 187     dir->begin = p;
 188     ++p;
 189     // %%
 190     if (*p == '%') {
 191       ++p;
 192       continue;
 193     }
 194     if (*p == '\0') {
 195       return nullptr;
 196     }
 197     // %n$
 198     p = maybe_parse_param_index(p, &dir->argIdx);
 199     CHECK(p);
 200     // *
 201     if (*p == '*') {
 202       dir->suppressed = true;
 203       ++p;
 204     }
 205     // Field width
 206     if (*p >= '0' && *p <= '9') {
 207       p = parse_number(p, &dir->fieldWidth);
 208       CHECK(p);
 209       if (dir->fieldWidth <= 0)  // Width if at all must be non-zero
 210         return nullptr;
 211     }
 212     // m
 213     if (*p == 'm') {
 214       dir->allocate = true;
 215       ++p;
 216     }
 217     // Length modifier.
 218     p = maybe_parse_length_modifier(p, dir->lengthModifier);
 219     // Conversion specifier.
 220     dir->convSpecifier = *p++;
 221     // Consume %[...] expression.
 222     if (dir->convSpecifier == '[') {
 223       if (*p == '^')
 224         ++p;
 225       if (*p == ']')
 226         ++p;
 227       while (*p && *p != ']')
 228         ++p;
 229       if (*p == 0)
 230         return nullptr; // unexpected end of string
 231                         // Consume the closing ']'.
 232       ++p;
 233     }
 234     // This is unfortunately ambiguous between old GNU extension
 235     // of %as, %aS and %a[...] and newer POSIX %a followed by
 236     // letters s, S or [.
 237     if (allowGnuMalloc && dir->convSpecifier == 'a' &&
 238         !dir->lengthModifier[0]) {
 239       if (*p == 's' || *p == 'S') {
 240         dir->maybeGnuMalloc = true;
 241         ++p;
 242       } else if (*p == '[') {
 243         // Watch for %a[h-j%d], if % appears in the
 244         // [...] range, then we need to give up, we don't know
 245         // if scanf will parse it as POSIX %a [h-j %d ] or
 246         // GNU allocation of string with range dh-j plus %.
 247         const char *q = p + 1;
 248         if (*q == '^')
 249           ++q;
 250         if (*q == ']')
 251           ++q;
 252         while (*q && *q != ']' && *q != '%')
 253           ++q;
 254         if (*q == 0 || *q == '%')
 255           return nullptr;
 256         p = q + 1; // Consume the closing ']'.
 257         dir->maybeGnuMalloc = true;
 258       }
 259     }
 260     dir->end = p;
 261     break;
 262   }
 263   return p;
 264 }
 265
 266 static int scanf_get_value_size(ScanfDirective *dir) {
 267   if (dir->allocate) {
 268     if (!char_is_one_of(dir->convSpecifier, "cCsS["))
 269       return FSS_INVALID;
 270     return sizeof(char *);
 271   }
 272
 273   if (dir->maybeGnuMalloc) {
 274     if (dir->convSpecifier != 'a' || dir->lengthModifier[0])
 275       return FSS_INVALID;
 276     // This is ambiguous, so check the smaller size of char * (if it is
 277     // a GNU extension of %as, %aS or %a[...]) and float (if it is
 278     // POSIX %a followed by s, S or [ letters).
 279     return sizeof(char *) < sizeof(float) ? sizeof(char *) : sizeof(float);
 280   }
 281
 282   if (char_is_one_of(dir->convSpecifier, "cCsS[")) {
 283     bool needsTerminator = char_is_one_of(dir->convSpecifier, "sS[");
 284     unsigned charSize =
 285         format_get_char_size(dir->convSpecifier, dir->lengthModifier);
 286     if (charSize == 0)
 287       return FSS_INVALID;
 288     if (dir->fieldWidth == 0) {
 289       if (!needsTerminator)
 290         return charSize;
 291       return (charSize == sizeof(char)) ? FSS_STRLEN : FSS_WCSLEN;
 292     }
 293     return (dir->fieldWidth + needsTerminator) * charSize;
 294   }
 295
 296   return format_get_value_size(dir->convSpecifier, dir->lengthModifier, false);
 297 }
 298
 299 // Common part of *scanf interceptors.
 300 // Process format string and va_list, and report all store ranges.
 301 // Stops when "consuming" n_inputs input items.
 302 static void scanf_common(void *ctx, int n_inputs, bool allowGnuMalloc,
 303                          const char *format, va_list aq) {
 304   CHECK_GT(n_inputs, 0);
 305   const char *p = format;
 306
 307   COMMON_INTERCEPTOR_READ_RANGE(ctx, format, internal_strlen(format) + 1);
 308
 309   while (*p) {
 310     ScanfDirective dir;
 311     p = scanf_parse_next(p, allowGnuMalloc, &dir);
 312     if (!p)
 313       break;
 314     if (dir.convSpecifier == 0) {
 315       // This can only happen at the end of the format string.
 316       CHECK_EQ(*p, 0);
 317       break;
 318     }
 319     // Here the directive is valid. Do what it says.
 320     if (dir.argIdx != -1) {
 321       // Unsupported.
 322       break;
 323     }
 324     if (dir.suppressed)
 325       continue;
 326     int size = scanf_get_value_size(&dir);
 327     if (size == FSS_INVALID) {
 328       Report("WARNING: unexpected format specifier in scanf interceptor: "
 329         "%.*s\n", dir.end - dir.begin, dir.begin);
 330       break;
 331     }
 332     void *argp = va_arg(aq, void *);
 333     if (dir.convSpecifier != 'n')
 334       --n_inputs;
 335     if (n_inputs < 0)
 336       break;
 337     if (size == FSS_STRLEN) {
 338       size = internal_strlen((const char *)argp) + 1;
 339     } else if (size == FSS_WCSLEN) {
 340       // FIXME: actually use wcslen() to calculate it.
 341       size = 0;
 342     }
 343     COMMON_INTERCEPTOR_WRITE_RANGE(ctx, argp, size);
 344   }
 345 }
 346
 347 #if SANITIZER_INTERCEPT_PRINTF
 348
 349 struct PrintfDirective {
 350   int fieldWidth;
 351   int fieldPrecision;
 352   int argIdx; // width argument index, or -1 if not specified ("%*n$")
 353   int precisionIdx; // precision argument index, or -1 if not specified (".*n$")
 354   const char *begin;
 355   const char *end;
 356   bool starredWidth;
 357   bool starredPrecision;
 358   char lengthModifier[2];
 359   char convSpecifier;
 360 };
 361
 362 static const char *maybe_parse_number(const char *p, int *out) {
 363   if (*p >= '0' && *p <= '9')
 364     p = parse_number(p, out);
 365   return p;
 366 }
 367
 368 static const char *maybe_parse_number_or_star(const char *p, int *out,
 369                                               bool *star) {
 370   if (*p == '*') {
 371     *star = true;
 372     ++p;
 373   } else {
 374     *star = false;
 375     p = maybe_parse_number(p, out);
 376   }
 377   return p;
 378 }
 379
 380 // Parse printf format string. Same as scanf_parse_next.
 381 static const char *printf_parse_next(const char *p, PrintfDirective *dir) {
 382   internal_memset(dir, 0, sizeof(*dir));
 383   dir->argIdx = -1;
 384   dir->precisionIdx = -1;
 385
 386   while (*p) {
 387     if (*p != '%') {
 388       ++p;
 389       continue;
 390     }
 391     dir->begin = p;
 392     ++p;
 393     // %%
 394     if (*p == '%') {
 395       ++p;
 396       continue;
 397     }
 398     if (*p == '\0') {
 399       return nullptr;
 400     }
 401     // %n$
 402     p = maybe_parse_param_index(p, &dir->precisionIdx);
 403     CHECK(p);
 404     // Flags
 405     while (char_is_one_of(*p, "'-+ #0")) {
 406       ++p;
 407     }
 408     // Field width
 409     p = maybe_parse_number_or_star(p, &dir->fieldWidth,
 410                                    &dir->starredWidth);
 411     if (!p)
 412       return nullptr;
 413     // Precision
 414     if (*p == '.') {
 415       ++p;
 416       // Actual precision is optional (surprise!)
 417       p = maybe_parse_number_or_star(p, &dir->fieldPrecision,
 418                                      &dir->starredPrecision);
 419       if (!p)
 420         return nullptr;
 421       // m$
 422       if (dir->starredPrecision) {
 423         p = maybe_parse_param_index(p, &dir->precisionIdx);
 424         CHECK(p);
 425       }
 426     }
 427     // Length modifier.
 428     p = maybe_parse_length_modifier(p, dir->lengthModifier);
 429     // Conversion specifier.
 430     dir->convSpecifier = *p++;
 431     dir->end = p;
 432     break;
 433   }
 434   return p;
 435 }
 436
 437 static int printf_get_value_size(PrintfDirective *dir) {
 438   if (char_is_one_of(dir->convSpecifier, "cCsS")) {
 439     unsigned charSize =
 440         format_get_char_size(dir->convSpecifier, dir->lengthModifier);
 441     if (charSize == 0)
 442       return FSS_INVALID;
 443     if (char_is_one_of(dir->convSpecifier, "sS")) {
 444       return (charSize == sizeof(char)) ? FSS_STRLEN : FSS_WCSLEN;
 445     }
 446     return charSize;
 447   }
 448
 449   return format_get_value_size(dir->convSpecifier, dir->lengthModifier, true);
 450 }
 451
 452 #define SKIP_SCALAR_ARG(aq, convSpecifier, size)                   \
 453   do {                                                             \
 454     if (format_is_float_conv(convSpecifier)) {                     \
 455       switch (size) {                                              \
 456       case 8:                                                      \
 457         va_arg(*aq, double);                                       \
 458         break;                                                     \
 459       case 12:                                                     \
 460         va_arg(*aq, long double);                                  \
 461         break;                                                     \
 462       case 16:                                                     \
 463         va_arg(*aq, long double);                                  \
 464         break;                                                     \
 465       default:                                                     \
 466         Report("WARNING: unexpected floating-point arg size"       \
 467                " in printf interceptor: %d\n", size);              \
 468         return;                                                    \
 469       }                                                            \
 470     } else {                                                       \
 471       switch (size) {                                              \
 472       case 1:                                                      \
 473       case 2:                                                      \
 474       case 4:                                                      \
 475         va_arg(*aq, u32);                                          \
 476         break;                                                     \
 477       case 8:                                                      \
 478         va_arg(*aq, u64);                                          \
 479         break;                                                     \
 480       default:                                                     \
 481         Report("WARNING: unexpected arg size"                      \
 482                " in printf interceptor: %d\n", size);              \
 483         return;                                                    \
 484       }                                                            \
 485     }                                                              \
 486   } while (0)
 487
 488 // Common part of *printf interceptors.
 489 // Process format string and va_list, and report all load ranges.
 490 static void printf_common(void *ctx, const char *format, va_list aq) {
 491   COMMON_INTERCEPTOR_READ_RANGE(ctx, format, internal_strlen(format) + 1);
 492
 493   const char *p = format;
 494
 495   while (*p) {
 496     PrintfDirective dir;
 497     p = printf_parse_next(p, &dir);
 498     if (!p)
 499       break;
 500     if (dir.convSpecifier == 0) {
 501       // This can only happen at the end of the format string.
 502       CHECK_EQ(*p, 0);
 503       break;
 504     }
 505     // Here the directive is valid. Do what it says.
 506     if (dir.argIdx != -1 || dir.precisionIdx != -1) {
 507       // Unsupported.
 508       break;
 509     }
 510     if (dir.starredWidth) {
 511       // Dynamic width
 512       SKIP_SCALAR_ARG(&aq, 'd', sizeof(int));
 513     }
 514     if (dir.starredPrecision) {
 515       // Dynamic precision
 516       SKIP_SCALAR_ARG(&aq, 'd', sizeof(int));
 517     }
 518     // %m does not require an argument: strlen(errno).
 519     if (dir.convSpecifier == 'm')
 520       continue;
 521     int size = printf_get_value_size(&dir);
 522     if (size == FSS_INVALID) {
 523       Report("WARNING: unexpected format specifier in printf "
 524              "interceptor: %.*s\n", dir.end - dir.begin, dir.begin);
 525       break;
 526     }
 527     if (dir.convSpecifier == 'n') {
 528       void *argp = va_arg(aq, void *);
 529       COMMON_INTERCEPTOR_WRITE_RANGE(ctx, argp, size);
 530       continue;
 531     } else if (size == FSS_STRLEN) {
 532       if (void *argp = va_arg(aq, void *)) {
 533         if (dir.starredPrecision) {
 534           // FIXME: properly support starred precision for strings.
 535           size = 0;
 536         } else if (dir.fieldPrecision > 0) {
 537           // Won't read more than "precision" symbols.
 538           size = internal_strnlen((const char *)argp, dir.fieldPrecision);
 539           if (size < dir.fieldPrecision) size++;
 540         } else {
 541           // Whole string will be accessed.
 542           size = internal_strlen((const char *)argp) + 1;
 543         }
 544         COMMON_INTERCEPTOR_READ_RANGE(ctx, argp, size);
 545       }
 546     } else if (size == FSS_WCSLEN) {
 547       if (void *argp = va_arg(aq, void *)) {
 548         // FIXME: Properly support wide-character strings (via wcsrtombs).
 549         size = 0;
 550         COMMON_INTERCEPTOR_READ_RANGE(ctx, argp, size);
 551       }
 552     } else {
 553       // Skip non-pointer args
 554       SKIP_SCALAR_ARG(&aq, dir.convSpecifier, size);
 555     }
 556   }
 557 }
 558
 559 #endif // SANITIZER_INTERCEPT_PRINTF