308 lines
8.2 KiB
C++
308 lines
8.2 KiB
C++
//===-- sanitizer_common_interceptors_scanf.inc -----------------*- C++ -*-===//
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// Scanf implementation for use in *Sanitizer interceptors.
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// Follows http://pubs.opengroup.org/onlinepubs/9699919799/functions/fscanf.html
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// with a few common GNU extensions.
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//
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//===----------------------------------------------------------------------===//
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#include <stdarg.h>
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struct ScanfDirective {
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int argIdx; // argument index, or -1 of not specified ("%n$")
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int fieldWidth;
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bool suppressed; // suppress assignment ("*")
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bool allocate; // allocate space ("m")
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char lengthModifier[2];
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char convSpecifier;
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bool maybeGnuMalloc;
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};
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static const char *parse_number(const char *p, int *out) {
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*out = internal_atoll(p);
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while (*p >= '0' && *p <= '9')
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++p;
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return p;
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}
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static bool char_is_one_of(char c, const char *s) {
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return !!internal_strchr(s, c);
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}
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// Parse scanf format string. If a valid directive in encountered, it is
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// returned in dir. This function returns the pointer to the first
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// unprocessed character, or 0 in case of error.
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// In case of the end-of-string, a pointer to the closing \0 is returned.
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static const char *scanf_parse_next(const char *p, bool allowGnuMalloc,
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ScanfDirective *dir) {
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internal_memset(dir, 0, sizeof(*dir));
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dir->argIdx = -1;
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while (*p) {
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if (*p != '%') {
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++p;
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continue;
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}
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++p;
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// %%
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if (*p == '%') {
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++p;
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continue;
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}
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if (*p == '\0') {
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return 0;
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}
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// %n$
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if (*p >= '0' && *p <= '9') {
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int number;
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const char *q = parse_number(p, &number);
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if (*q == '$') {
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dir->argIdx = number;
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p = q + 1;
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}
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// Otherwise, do not change p. This will be re-parsed later as the field
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// width.
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}
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// *
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if (*p == '*') {
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dir->suppressed = true;
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++p;
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}
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// Field width.
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if (*p >= '0' && *p <= '9') {
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p = parse_number(p, &dir->fieldWidth);
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if (dir->fieldWidth <= 0)
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return 0;
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}
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// m
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if (*p == 'm') {
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dir->allocate = true;
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++p;
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}
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// Length modifier.
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if (char_is_one_of(*p, "jztLq")) {
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dir->lengthModifier[0] = *p;
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++p;
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} else if (*p == 'h') {
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dir->lengthModifier[0] = 'h';
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++p;
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if (*p == 'h') {
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dir->lengthModifier[1] = 'h';
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++p;
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}
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} else if (*p == 'l') {
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dir->lengthModifier[0] = 'l';
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++p;
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if (*p == 'l') {
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dir->lengthModifier[1] = 'l';
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++p;
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}
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}
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// Conversion specifier.
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dir->convSpecifier = *p++;
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// Consume %[...] expression.
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if (dir->convSpecifier == '[') {
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if (*p == '^')
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++p;
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if (*p == ']')
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++p;
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while (*p && *p != ']')
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++p;
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if (*p == 0)
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return 0; // unexpected end of string
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// Consume the closing ']'.
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++p;
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}
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// This is unfortunately ambiguous between old GNU extension
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// of %as, %aS and %a[...] and newer POSIX %a followed by
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// letters s, S or [.
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if (allowGnuMalloc && dir->convSpecifier == 'a' &&
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!dir->lengthModifier[0]) {
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if (*p == 's' || *p == 'S') {
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dir->maybeGnuMalloc = true;
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++p;
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} else if (*p == '[') {
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// Watch for %a[h-j%d], if % appears in the
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// [...] range, then we need to give up, we don't know
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// if scanf will parse it as POSIX %a [h-j %d ] or
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// GNU allocation of string with range dh-j plus %.
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const char *q = p + 1;
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if (*q == '^')
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++q;
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if (*q == ']')
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++q;
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while (*q && *q != ']' && *q != '%')
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++q;
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if (*q == 0 || *q == '%')
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return 0;
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p = q + 1; // Consume the closing ']'.
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dir->maybeGnuMalloc = true;
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}
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}
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break;
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}
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return p;
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}
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// Returns true if the character is an integer conversion specifier.
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static bool scanf_is_integer_conv(char c) {
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return char_is_one_of(c, "diouxXn");
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}
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// Returns true if the character is an floating point conversion specifier.
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static bool scanf_is_float_conv(char c) {
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return char_is_one_of(c, "aAeEfFgG");
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}
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// Returns string output character size for string-like conversions,
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// or 0 if the conversion is invalid.
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static int scanf_get_char_size(ScanfDirective *dir) {
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if (char_is_one_of(dir->convSpecifier, "CS")) {
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// wchar_t
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return 0;
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}
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if (char_is_one_of(dir->convSpecifier, "cs[")) {
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if (dir->lengthModifier[0] == 'l')
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// wchar_t
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return 0;
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else if (dir->lengthModifier[0] == 0)
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return sizeof(char);
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else
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return 0;
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}
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return 0;
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}
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enum ScanfStoreSize {
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// Store size not known in advance; can be calculated as strlen() of the
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// destination buffer.
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SSS_STRLEN = -1,
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// Invalid conversion specifier.
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SSS_INVALID = 0
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};
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// Returns the store size of a scanf directive (if >0), or a value of
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// ScanfStoreSize.
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static int scanf_get_store_size(ScanfDirective *dir) {
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if (dir->allocate) {
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if (!char_is_one_of(dir->convSpecifier, "cCsS["))
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return SSS_INVALID;
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return sizeof(char *);
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}
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if (dir->maybeGnuMalloc) {
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if (dir->convSpecifier != 'a' || dir->lengthModifier[0])
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return SSS_INVALID;
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// This is ambiguous, so check the smaller size of char * (if it is
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// a GNU extension of %as, %aS or %a[...]) and float (if it is
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// POSIX %a followed by s, S or [ letters).
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return sizeof(char *) < sizeof(float) ? sizeof(char *) : sizeof(float);
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}
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if (scanf_is_integer_conv(dir->convSpecifier)) {
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switch (dir->lengthModifier[0]) {
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case 'h':
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return dir->lengthModifier[1] == 'h' ? sizeof(char) : sizeof(short);
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case 'l':
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return dir->lengthModifier[1] == 'l' ? sizeof(long long) : sizeof(long);
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case 'L':
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return sizeof(long long);
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case 'j':
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return sizeof(INTMAX_T);
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case 'z':
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return sizeof(SIZE_T);
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case 't':
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return sizeof(PTRDIFF_T);
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case 0:
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return sizeof(int);
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default:
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return SSS_INVALID;
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}
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}
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if (scanf_is_float_conv(dir->convSpecifier)) {
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switch (dir->lengthModifier[0]) {
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case 'L':
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case 'q':
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return sizeof(long double);
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case 'l':
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return dir->lengthModifier[1] == 'l' ? sizeof(long double)
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: sizeof(double);
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case 0:
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return sizeof(float);
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default:
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return SSS_INVALID;
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}
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}
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if (char_is_one_of(dir->convSpecifier, "sS[")) {
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unsigned charSize = scanf_get_char_size(dir);
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if (charSize == 0)
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return SSS_INVALID;
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if (dir->fieldWidth == 0)
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return SSS_STRLEN;
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return (dir->fieldWidth + 1) * charSize;
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}
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if (char_is_one_of(dir->convSpecifier, "cC")) {
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unsigned charSize = scanf_get_char_size(dir);
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if (charSize == 0)
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return SSS_INVALID;
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if (dir->fieldWidth == 0)
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return charSize;
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return dir->fieldWidth * charSize;
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}
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if (dir->convSpecifier == 'p') {
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if (dir->lengthModifier[1] != 0)
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return SSS_INVALID;
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return sizeof(void *);
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}
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return SSS_INVALID;
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}
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// Common part of *scanf interceptors.
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// Process format string and va_list, and report all store ranges.
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// Stops when "consuming" n_inputs input items.
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static void scanf_common(void *ctx, int n_inputs, bool allowGnuMalloc,
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const char *format, va_list aq) {
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CHECK_GT(n_inputs, 0);
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const char *p = format;
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while (*p && n_inputs) {
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ScanfDirective dir;
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p = scanf_parse_next(p, allowGnuMalloc, &dir);
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if (!p)
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break;
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if (dir.convSpecifier == 0) {
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// This can only happen at the end of the format string.
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CHECK_EQ(*p, 0);
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break;
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}
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// Here the directive is valid. Do what it says.
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if (dir.argIdx != -1) {
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// Unsupported.
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break;
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}
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if (dir.suppressed)
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continue;
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int size = scanf_get_store_size(&dir);
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if (size == SSS_INVALID)
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break;
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void *argp = va_arg(aq, void *);
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if (dir.convSpecifier != 'n')
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--n_inputs;
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if (size == SSS_STRLEN) {
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size = internal_strlen((const char *)argp) + 1;
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}
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COMMON_INTERCEPTOR_WRITE_RANGE(ctx, argp, size);
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}
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}
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