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mirror of https://github.com/qpdf/qpdf.git synced 2024-10-31 19:02:30 +00:00
qpdf/libqpdf/QPDFTokenizer.cc
2022-07-26 13:40:13 +01:00

710 lines
23 KiB
C++

#include <qpdf/QPDFTokenizer.hh>
// DO NOT USE ctype -- it is locale dependent for some things, and
// it's not worth the risk of including it in case it may accidentally
// be used.
#include <qpdf/QIntC.hh>
#include <qpdf/QPDFExc.hh>
#include <qpdf/QPDFObjectHandle.hh>
#include <qpdf/QTC.hh>
#include <qpdf/QUtil.hh>
#include <stdexcept>
#include <stdlib.h>
#include <string.h>
static bool
is_delimiter(char ch)
{
return (strchr(" \t\n\v\f\r()<>[]{}/%", ch) != nullptr);
}
namespace
{
class QPDFWordTokenFinder: public InputSource::Finder
{
public:
QPDFWordTokenFinder(
std::shared_ptr<InputSource> is, std::string const& str) :
is(is),
str(str)
{
}
virtual ~QPDFWordTokenFinder() = default;
virtual bool check();
private:
std::shared_ptr<InputSource> is;
std::string str;
};
} // namespace
bool
QPDFWordTokenFinder::check()
{
// Find a word token matching the given string, preceded by a
// delimiter, and followed by a delimiter or EOF.
QPDFTokenizer tokenizer;
QPDFTokenizer::Token t = tokenizer.readToken(is, "finder", true);
qpdf_offset_t pos = is->tell();
if (!(t == QPDFTokenizer::Token(QPDFTokenizer::tt_word, str))) {
QTC::TC("qpdf", "QPDFTokenizer finder found wrong word");
return false;
}
qpdf_offset_t token_start = is->getLastOffset();
char next;
bool next_okay = false;
if (is->read(&next, 1) == 0) {
QTC::TC("qpdf", "QPDFTokenizer inline image at EOF");
next_okay = true;
} else {
next_okay = is_delimiter(next);
}
is->seek(pos, SEEK_SET);
if (!next_okay) {
return false;
}
if (token_start == 0) {
// Can't actually happen...we never start the search at the
// beginning of the input.
return false;
}
return true;
}
QPDFTokenizer::Members::Members() :
allow_eof(false),
include_ignorable(false)
{
reset();
}
void
QPDFTokenizer::Members::reset()
{
state = st_top;
type = tt_bad;
val = "";
raw_val = "";
error_message = "";
unread_char = false;
char_to_unread = '\0';
inline_image_bytes = 0;
string_depth = 0;
string_ignoring_newline = false;
last_char_was_bs = false;
last_char_was_cr = false;
}
QPDFTokenizer::Token::Token(token_type_e type, std::string const& value) :
type(type),
value(value),
raw_value(value)
{
if (type == tt_string) {
raw_value = QPDFObjectHandle::newString(value).unparse();
} else if (type == tt_name) {
raw_value = QPDFObjectHandle::newName(value).unparse();
}
}
QPDFTokenizer::QPDFTokenizer() :
m(new Members())
{
}
void
QPDFTokenizer::allowEOF()
{
this->m->allow_eof = true;
}
void
QPDFTokenizer::includeIgnorable()
{
this->m->include_ignorable = true;
}
bool
QPDFTokenizer::isSpace(char ch)
{
return ((ch == '\0') || QUtil::is_space(ch));
}
bool
QPDFTokenizer::isDelimiter(char ch)
{
return is_delimiter(ch);
}
void
QPDFTokenizer::resolveLiteral()
{
if ((this->m->val.length() > 0) && (this->m->val.at(0) == '/')) {
this->m->type = tt_name;
// Deal with # in name token. Note: '/' by itself is a
// valid name, so don't strip leading /. That way we
// don't have to deal with the empty string as a name.
std::string nval = "/";
size_t len = this->m->val.length();
for (size_t i = 1; i < len; ++i) {
char ch = this->m->val.at(i);
if (ch == '#') {
if ((i + 2 < len) &&
QUtil::is_hex_digit(this->m->val.at(i + 1)) &&
QUtil::is_hex_digit(this->m->val.at(i + 2))) {
char num[3];
num[0] = this->m->val.at(i + 1);
num[1] = this->m->val.at(i + 2);
num[2] = '\0';
char ch2 = static_cast<char>(strtol(num, nullptr, 16));
if (ch2 == '\0') {
this->m->type = tt_bad;
QTC::TC("qpdf", "QPDFTokenizer null in name");
this->m->error_message =
"null character not allowed in name token";
nval += "#00";
} else {
nval.append(1, ch2);
}
i += 2;
} else {
QTC::TC("qpdf", "QPDFTokenizer bad name");
this->m->error_message =
"name with stray # will not work with PDF >= 1.2";
// Use null to encode a bad # -- this is reversed
// in QPDF_Name::normalizeName.
nval += '\0';
}
} else {
nval.append(1, ch);
}
}
this->m->val = nval;
} else if (QUtil::is_number(this->m->val.c_str())) {
if (this->m->val.find('.') != std::string::npos) {
this->m->type = tt_real;
} else {
this->m->type = tt_integer;
}
} else if ((this->m->val == "true") || (this->m->val == "false")) {
this->m->type = tt_bool;
} else if (this->m->val == "null") {
this->m->type = tt_null;
} else {
// I don't really know what it is, so leave it as tt_word.
// Lots of cases ($, #, etc.) other than actual words fall
// into this category, but that's okay at least for now.
this->m->type = tt_word;
}
}
void
QPDFTokenizer::presentCharacter(char ch)
{
if (this->m->state == st_token_ready) {
throw std::logic_error(
"INTERNAL ERROR: QPDF tokenizer presented character "
"while token is waiting");
}
char orig_ch = ch;
// State machine is implemented such that some characters may be
// handled more than once. This happens whenever you have to use
// the character that caused a state change in the new state.
bool handled = true;
if (this->m->state == st_top) {
// Note: we specifically do not use ctype here. It is
// locale-dependent.
if (isSpace(ch)) {
if (this->m->include_ignorable) {
this->m->state = st_in_space;
this->m->val += ch;
}
} else if (ch == '%') {
this->m->state = st_in_comment;
if (this->m->include_ignorable) {
this->m->val += ch;
}
} else if (ch == '(') {
this->m->string_depth = 1;
this->m->string_ignoring_newline = false;
memset(
this->m->bs_num_register,
'\0',
sizeof(this->m->bs_num_register));
this->m->last_char_was_bs = false;
this->m->last_char_was_cr = false;
this->m->state = st_in_string;
} else if (ch == '<') {
this->m->state = st_lt;
} else if (ch == '>') {
this->m->state = st_gt;
} else {
this->m->val += ch;
if (ch == ')') {
this->m->type = tt_bad;
QTC::TC("qpdf", "QPDFTokenizer bad )");
this->m->error_message = "unexpected )";
this->m->state = st_token_ready;
} else if (ch == '[') {
this->m->type = tt_array_open;
this->m->state = st_token_ready;
} else if (ch == ']') {
this->m->type = tt_array_close;
this->m->state = st_token_ready;
} else if (ch == '{') {
this->m->type = tt_brace_open;
this->m->state = st_token_ready;
} else if (ch == '}') {
this->m->type = tt_brace_close;
this->m->state = st_token_ready;
} else {
this->m->state = st_literal;
}
}
} else if (this->m->state == st_in_space) {
// We only enter this state if include_ignorable is true.
if (!isSpace(ch)) {
this->m->type = tt_space;
this->m->unread_char = true;
this->m->char_to_unread = ch;
this->m->state = st_token_ready;
} else {
this->m->val += ch;
}
} else if (this->m->state == st_in_comment) {
if ((ch == '\r') || (ch == '\n')) {
if (this->m->include_ignorable) {
this->m->type = tt_comment;
this->m->unread_char = true;
this->m->char_to_unread = ch;
this->m->state = st_token_ready;
} else {
this->m->state = st_top;
}
} else if (this->m->include_ignorable) {
this->m->val += ch;
}
} else if (this->m->state == st_lt) {
if (ch == '<') {
this->m->val = "<<";
this->m->type = tt_dict_open;
this->m->state = st_token_ready;
} else {
handled = false;
this->m->state = st_in_hexstring;
}
} else if (this->m->state == st_gt) {
if (ch == '>') {
this->m->val = ">>";
this->m->type = tt_dict_close;
this->m->state = st_token_ready;
} else {
this->m->val = ">";
this->m->type = tt_bad;
QTC::TC("qpdf", "QPDFTokenizer bad >");
this->m->error_message = "unexpected >";
this->m->unread_char = true;
this->m->char_to_unread = ch;
this->m->state = st_token_ready;
}
} else if (this->m->state == st_in_string) {
if (this->m->string_ignoring_newline && (ch != '\n')) {
this->m->string_ignoring_newline = false;
}
size_t bs_num_count = strlen(this->m->bs_num_register);
bool ch_is_octal = ((ch >= '0') && (ch <= '7'));
if ((bs_num_count == 3) || ((bs_num_count > 0) && (!ch_is_octal))) {
// We've accumulated \ddd. PDF Spec says to ignore
// high-order overflow.
this->m->val +=
static_cast<char>(strtol(this->m->bs_num_register, nullptr, 8));
memset(
this->m->bs_num_register,
'\0',
sizeof(this->m->bs_num_register));
bs_num_count = 0;
}
if (this->m->string_ignoring_newline && (ch == '\n')) {
// ignore
this->m->string_ignoring_newline = false;
} else if (
ch_is_octal && (this->m->last_char_was_bs || (bs_num_count > 0))) {
this->m->bs_num_register[bs_num_count++] = ch;
} else if (this->m->last_char_was_bs) {
switch (ch) {
case 'n':
this->m->val += '\n';
break;
case 'r':
this->m->val += '\r';
break;
case 't':
this->m->val += '\t';
break;
case 'b':
this->m->val += '\b';
break;
case 'f':
this->m->val += '\f';
break;
case '\n':
break;
case '\r':
this->m->string_ignoring_newline = true;
break;
default:
// PDF spec says backslash is ignored before anything else
this->m->val += ch;
break;
}
} else if (ch == '\\') {
// last_char_was_bs is set/cleared below as appropriate
if (bs_num_count) {
throw std::logic_error(
"INTERNAL ERROR: QPDFTokenizer: bs_num_count != 0 "
"when ch == '\\'");
}
} else if (ch == '(') {
this->m->val += ch;
++this->m->string_depth;
} else if ((ch == ')') && (--this->m->string_depth == 0)) {
this->m->type = tt_string;
this->m->state = st_token_ready;
} else if (ch == '\r') {
// CR by itself is converted to LF
this->m->val += '\n';
} else if (ch == '\n') {
// CR LF is converted to LF
if (!this->m->last_char_was_cr) {
this->m->val += ch;
}
} else {
this->m->val += ch;
}
this->m->last_char_was_cr =
((!this->m->string_ignoring_newline) && (ch == '\r'));
this->m->last_char_was_bs =
((!this->m->last_char_was_bs) && (ch == '\\'));
} else if (this->m->state == st_literal) {
if (isDelimiter(ch)) {
// A C-locale whitespace character or delimiter terminates
// token. It is important to unread the whitespace
// character even though it is ignored since it may be the
// newline after a stream keyword. Removing it here could
// make the stream-reading code break on some files,
// though not on any files in the test suite as of this
// writing.
this->m->type = tt_word;
this->m->unread_char = true;
this->m->char_to_unread = ch;
this->m->state = st_token_ready;
} else {
this->m->val += ch;
}
} else if (this->m->state == st_inline_image) {
this->m->val += ch;
size_t len = this->m->val.length();
if (len == this->m->inline_image_bytes) {
QTC::TC("qpdf", "QPDFTokenizer found EI by byte count");
this->m->type = tt_inline_image;
this->m->inline_image_bytes = 0;
this->m->state = st_token_ready;
}
} else {
handled = false;
}
if (handled) {
// okay
} else if (this->m->state == st_in_hexstring) {
if (ch == '>') {
this->m->type = tt_string;
this->m->state = st_token_ready;
if (this->m->val.length() % 2) {
// PDF spec says odd hexstrings have implicit
// trailing 0.
this->m->val += '0';
}
char num[3];
num[2] = '\0';
std::string nval;
for (unsigned int i = 0; i < this->m->val.length(); i += 2) {
num[0] = this->m->val.at(i);
num[1] = this->m->val.at(i + 1);
char nch = static_cast<char>(strtol(num, nullptr, 16));
nval += nch;
}
this->m->val = nval;
} else if (QUtil::is_hex_digit(ch)) {
this->m->val += ch;
} else if (isSpace(ch)) {
// ignore
} else {
this->m->type = tt_bad;
QTC::TC("qpdf", "QPDFTokenizer bad hexstring character");
this->m->error_message =
std::string("invalid character (") + ch + ") in hexstring";
this->m->state = st_token_ready;
}
} else {
throw std::logic_error(
"INTERNAL ERROR: invalid state while reading token");
}
if ((this->m->state == st_token_ready) && (this->m->type == tt_word)) {
resolveLiteral();
}
if (!(betweenTokens() ||
((this->m->state == st_token_ready) && this->m->unread_char))) {
this->m->raw_val += orig_ch;
}
}
void
QPDFTokenizer::presentEOF()
{
if (this->m->state == st_literal) {
QTC::TC("qpdf", "QPDFTokenizer EOF reading appendable token");
resolveLiteral();
} else if (
(this->m->include_ignorable) && (this->m->state == st_in_space)) {
this->m->type = tt_space;
} else if (
(this->m->include_ignorable) && (this->m->state == st_in_comment)) {
this->m->type = tt_comment;
} else if (betweenTokens()) {
this->m->type = tt_eof;
} else if (this->m->state != st_token_ready) {
QTC::TC("qpdf", "QPDFTokenizer EOF reading token");
this->m->type = tt_bad;
this->m->error_message = "EOF while reading token";
}
this->m->state = st_token_ready;
}
void
QPDFTokenizer::expectInlineImage(std::shared_ptr<InputSource> input)
{
if (this->m->state != st_top) {
throw std::logic_error("QPDFTokenizer::expectInlineImage called"
" when tokenizer is in improper state");
}
findEI(input);
this->m->state = st_inline_image;
}
void
QPDFTokenizer::findEI(std::shared_ptr<InputSource> input)
{
if (!input.get()) {
return;
}
qpdf_offset_t last_offset = input->getLastOffset();
qpdf_offset_t pos = input->tell();
// Use QPDFWordTokenFinder to find EI surrounded by delimiters.
// Then read the next several tokens or up to EOF. If we find any
// suspicious-looking or tokens, this is probably still part of
// the image data, so keep looking for EI. Stop at the first EI
// that passes. If we get to the end without finding one, return
// the last EI we found. Store the number of bytes expected in the
// inline image including the EI and use that to break out of
// inline image, falling back to the old method if needed.
bool okay = false;
bool first_try = true;
while (!okay) {
QPDFWordTokenFinder f(input, "EI");
if (!input->findFirst("EI", input->tell(), 0, f)) {
break;
}
this->m->inline_image_bytes = QIntC::to_size(input->tell() - pos - 2);
QPDFTokenizer check;
bool found_bad = false;
// Look at the next 10 tokens or up to EOF. The next inline
// image's image data would look like bad tokens, but there
// will always be at least 10 tokens between one inline
// image's EI and the next valid one's ID since width, height,
// bits per pixel, and color space are all required as well as
// a BI and ID. If we get 10 good tokens in a row or hit EOF,
// we can be pretty sure we've found the actual EI.
for (int i = 0; i < 10; ++i) {
QPDFTokenizer::Token t = check.readToken(input, "checker", true);
token_type_e type = t.getType();
if (type == tt_eof) {
okay = true;
} else if (type == tt_bad) {
found_bad = true;
} else if (type == tt_word) {
// The qpdf tokenizer lumps alphabetic and otherwise
// uncategorized characters into "words". We recognize
// strings of alphabetic characters as potential valid
// operators for purposes of telling whether we're in
// valid content or not. It's not perfect, but it
// should work more reliably than what we used to do,
// which was already good enough for the vast majority
// of files.
bool found_alpha = false;
bool found_non_printable = false;
bool found_other = false;
for (char ch: t.getValue()) {
if (((ch >= 'a') && (ch <= 'z')) ||
((ch >= 'A') && (ch <= 'Z')) || (ch == '*')) {
// Treat '*' as alpha since there are valid
// PDF operators that contain * along with
// alphabetic characters.
found_alpha = true;
} else if (
(static_cast<signed char>(ch) < 32) && (!isSpace(ch))) {
// Compare ch as a signed char so characters
// outside of 7-bit will be < 0.
found_non_printable = true;
break;
} else {
found_other = true;
}
}
if (found_non_printable || (found_alpha && found_other)) {
found_bad = true;
}
}
if (okay || found_bad) {
break;
}
}
if (!found_bad) {
okay = true;
}
if (!okay) {
first_try = false;
}
}
if (okay && (!first_try)) {
QTC::TC("qpdf", "QPDFTokenizer found EI after more than one try");
}
input->seek(pos, SEEK_SET);
input->setLastOffset(last_offset);
}
bool
QPDFTokenizer::getToken(Token& token, bool& unread_char, char& ch)
{
bool ready = (this->m->state == st_token_ready);
unread_char = this->m->unread_char;
ch = this->m->char_to_unread;
if (ready) {
if (this->m->type == tt_bad) {
this->m->val = this->m->raw_val;
}
token = Token(
this->m->type,
this->m->val,
this->m->raw_val,
this->m->error_message);
this->m->reset();
}
return ready;
}
bool
QPDFTokenizer::betweenTokens()
{
return (
(this->m->state == st_top) ||
((!this->m->include_ignorable) &&
((this->m->state == st_in_comment) ||
(this->m->state == st_in_space))));
}
QPDFTokenizer::Token
QPDFTokenizer::readToken(
std::shared_ptr<InputSource> input,
std::string const& context,
bool allow_bad,
size_t max_len)
{
qpdf_offset_t offset = input->tell();
Token token;
bool unread_char;
char char_to_unread;
bool presented_eof = false;
while (!getToken(token, unread_char, char_to_unread)) {
char ch;
if (input->read(&ch, 1) == 0) {
if (!presented_eof) {
presentEOF();
presented_eof = true;
if ((this->m->type == tt_eof) && (!this->m->allow_eof)) {
// Nothing in the qpdf library calls readToken
// without allowEOF anymore, so this case is not
// exercised.
this->m->type = tt_bad;
this->m->error_message = "unexpected EOF";
offset = input->getLastOffset();
}
} else {
throw std::logic_error(
"getToken returned false after presenting EOF");
}
} else {
presentCharacter(ch);
if (betweenTokens() && (input->getLastOffset() == offset)) {
++offset;
}
if (max_len && (this->m->raw_val.length() >= max_len) &&
(this->m->state != st_token_ready)) {
// terminate this token now
QTC::TC("qpdf", "QPDFTokenizer block long token");
this->m->type = tt_bad;
this->m->state = st_token_ready;
this->m->error_message =
"exceeded allowable length while reading token";
}
}
}
if (unread_char) {
input->unreadCh(char_to_unread);
}
if (token.getType() != tt_eof) {
input->setLastOffset(offset);
}
if (token.getType() == tt_bad) {
if (allow_bad) {
QTC::TC("qpdf", "QPDFTokenizer allowing bad token");
} else {
throw QPDFExc(
qpdf_e_damaged_pdf,
input->getName(),
context,
offset,
token.getErrorMessage());
}
}
return token;
}