Commit message: src/wav.c: Fix heap read overflow

This is CVE-2018-19758.

Closes: https://github.com/erikd/libsndfile/issues/435
CVE: CVE-2018-19758
CWE: CWE-125
Vulnerability description: There is a heap-based buffer over-read at wav.c in wav_write_header in libsndfile 1.0.28 that will cause a denial of service.

Project: libsndfile
File: wav.c

wav_write_header (SF_PRIVATE *psf, int calc_length)
{	sf_count_t	current ;
	int 		error, has_data = SF_FALSE ;

	current = psf_ftell (psf) ;

	if (current > psf->dataoffset)
		has_data = SF_TRUE ;

	if (calc_length)
	{	psf->filelength = psf_get_filelen (psf) ;

		psf->datalength = psf->filelength - psf->dataoffset ;

		if (psf->dataend)
			psf->datalength -= psf->filelength - psf->dataend ;
		else if (psf->bytewidth > 0 && psf->sf.seekable == SF_TRUE)
			psf->datalength = psf->sf.frames * psf->bytewidth * psf->sf.channels ;
		} ;

	/* Reset the current header length to zero. */
	psf->header.ptr [0] = 0 ;
	psf->header.indx = 0 ;
	psf_fseek (psf, 0, SEEK_SET) ;

	/*
	** RIFX signifies big-endian format for all header and data.
	** To prevent lots of code copying here, we'll set the psf->rwf_endian flag
	** once here, and never specify endian-ness for all other header operations.
	*/

	/* RIFF/RIFX marker, length, WAVE and 'fmt ' markers. */

	if (psf->endian == SF_ENDIAN_LITTLE)
		psf_binheader_writef (psf, "etm8", BHWm (RIFF_MARKER), BHW8 ((psf->filelength < 8) ? 8 : psf->filelength - 8)) ;
	else
		psf_binheader_writef (psf, "Etm8", BHWm (RIFX_MARKER), BHW8 ((psf->filelength < 8) ? 8 : psf->filelength - 8)) ;

	/* WAVE and 'fmt ' markers. */
	psf_binheader_writef (psf, "mm", BHWm (WAVE_MARKER), BHWm (fmt_MARKER)) ;

	/* Write the 'fmt ' chunk. */
	switch (SF_CONTAINER (psf->sf.format))
	{	case SF_FORMAT_WAV :
				if ((error = wav_write_fmt_chunk (psf)) != 0)
					return error ;
				break ;

		case SF_FORMAT_WAVEX :
				if ((error = wavex_write_fmt_chunk (psf)) != 0)
					return error ;
				break ;

		default :
				return SFE_UNIMPLEMENTED ;
		} ;

	/* The LIST/INFO chunk. */
	if (psf->strings.flags & SF_STR_LOCATE_START)
		wavlike_write_strings (psf, SF_STR_LOCATE_START) ;

	if (psf->peak_info != NULL && psf->peak_info->peak_loc == SF_PEAK_START)
		wavlike_write_peak_chunk (psf) ;

	if (psf->broadcast_16k != NULL)
		wavlike_write_bext_chunk (psf) ;

	if (psf->cart_16k != NULL)
		wavlike_write_cart_chunk (psf) ;

	if (psf->cues != NULL)
	{	uint32_t k ;

		psf_binheader_writef (psf, "em44", BHWm (cue_MARKER), BHW4 (4 + psf->cues->cue_count * 6 * 4), BHW4 (psf->cues->cue_count)) ;

		for (k = 0 ; k < psf->cues->cue_count ; k++)
			psf_binheader_writef (psf, "e44m444", BHW4 (psf->cues->cue_points [k].indx), BHW4 (psf->cues->cue_points [k].position),
						BHWm (psf->cues->cue_points [k].fcc_chunk), BHW4 (psf->cues->cue_points [k].chunk_start),
						BHW4 (psf->cues->cue_points [k].block_start), BHW4 (psf->cues->cue_points [k].sample_offset)) ;
		} ;

	if (psf->instrument != NULL)
	{	int		tmp ;
		double	dtune = (double) (0x40000000) / 25.0 ;

		psf_binheader_writef (psf, "m4", BHWm (smpl_MARKER), BHW4 (9 * 4 + psf->instrument->loop_count * 6 * 4)) ;
		psf_binheader_writef (psf, "44", BHW4 (0), BHW4 (0)) ; /* Manufacturer zero is everyone */
		tmp = (int) (1.0e9 / psf->sf.samplerate) ; /* Sample period in nano seconds */
		psf_binheader_writef (psf, "44", BHW4 (tmp), BHW4 (psf->instrument->basenote)) ;
		tmp = (uint32_t) (psf->instrument->detune * dtune + 0.5) ;
		psf_binheader_writef (psf, "4", BHW4 (tmp)) ;
		psf_binheader_writef (psf, "44", BHW4 (0), BHW4 (0)) ; /* SMTPE format */
		psf_binheader_writef (psf, "44", BHW4 (psf->instrument->loop_count), BHW4 (0)) ;

		for (tmp = 0 ; tmp < psf->instrument->loop_count ; tmp++)
		{	int type ;

			type = psf->instrument->loops [tmp].mode ;
			type = (type == SF_LOOP_FORWARD ? 0 : type == SF_LOOP_BACKWARD ? 2 : type == SF_LOOP_ALTERNATING ? 1 : 32) ;

			psf_binheader_writef (psf, "44", BHW4 (tmp), BHW4 (type)) ;
			psf_binheader_writef (psf, "44", BHW4 (psf->instrument->loops [tmp].start), BHW4 (psf->instrument->loops [tmp].end - 1)) ;
			psf_binheader_writef (psf, "44", BHW4 (0), BHW4 (psf->instrument->loops [tmp].count)) ;
			} ;
		} ;

	/* Write custom headers. */
	if (psf->wchunks.used > 0)
		wavlike_write_custom_chunks (psf) ;

	if (psf->header.indx + 16 < psf->dataoffset)
	{	/* Add PAD data if necessary. */
		size_t k = psf->dataoffset - (psf->header.indx + 16) ;
		psf_binheader_writef (psf, "m4z", BHWm (PAD_MARKER), BHW4 (k), BHWz (k)) ;
		} ;

	psf_binheader_writef (psf, "tm8", BHWm (data_MARKER), BHW8 (psf->datalength)) ;
	psf_fwrite (psf->header.ptr, psf->header.indx, 1, psf) ;
	if (psf->error)
		return psf->error ;

	if (has_data && psf->dataoffset != psf->header.indx)
	{	psf_log_printf (psf, "Oooops : has_data && psf->dataoffset != psf->header.indx\n") ;
		return psf->error = SFE_INTERNAL ;
		} ;

	psf->dataoffset = psf->header.indx ;

	if (! has_data)
		psf_fseek (psf, psf->dataoffset, SEEK_SET) ;
	else if (current > 0)
		psf_fseek (psf, current, SEEK_SET) ;

	return psf->error ;
} /* wav_write_header */