qpdf/libqpdf/QPDFTokenizer.cc

#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/QTC.hh>
#include <qpdf/QPDFExc.hh>
#include <qpdf/QUtil.hh>
#include <qpdf/QPDFObjectHandle.hh>
#include <qpdf/QIntC.hh>

#include <stdexcept>
#include <stdlib.h>
#include <string.h>

static bool is_delimiter(char ch)
{
    return (strchr(" \t\n\v\f\r()<>[]{}/%", ch) != 0);
}

class QPDFWordTokenFinder: public InputSource::Finder
{
  public:
    QPDFWordTokenFinder(PointerHolder<InputSource> is,
                        std::string const& str) :
        is(is),
        str(str)
    {
    }
    virtual ~QPDFWordTokenFinder()
    {
    }
    virtual bool check();

  private:
    PointerHolder<InputSource> is;
    std::string str;
};

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::Members::~Members()
{
}

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 ch = static_cast<char>(strtol(num, 0, 16));
                    if (ch == '\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, ch);
                    }
                    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, 0, 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, 0, 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(PointerHolder<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(PointerHolder<InputSource> input)
{
    if (! input.getPointer())
    {
        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;
                std::string value = t.getValue();
                for (std::string::iterator iter = value.begin();
                     iter != value.end(); ++iter)
                {
                    char ch = *iter;
                    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 (((ch < 32) && (! isSpace(ch))) || (ch > 127))
                    {
                        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(PointerHolder<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;
}