optionally detect initial EOL in CCITTFaxDecode streams

If /EndOfLine is set for a CCITTFaxDecode stream, the image must start
with an EOL per the spec. Other readers seem to ignore all data up to
the first EOL in that case - instead of rejecting such images as broken.
Required for e.g. "1848 - 1d faxd doesn't start with EOL.pdf".

1 files changed, 18 insertions, 1 deletions

diff --git a/source/fitz/filter-fax.c b/source/fitz/filter-fax.c
index 8ac98f42..9ed5797a 100644
--- a/source/fitz/filter-fax.c
+++ b/source/fitz/filter-fax.c
@@ -311,6 +311,7 @@ typedef struct fz_faxd_s fz_faxd;
 
 enum
 {
+	STATE_INIT,		/* initial state, optionally waiting for EOL */
 	STATE_NORMAL,	/* neutral state, waiting for any code */
 	STATE_MAKEUP,	/* got a 1d makeup code, waiting for terminating code */
 	STATE_EOL,		/* at eol, needs output buffer space */
@@ -557,6 +558,22 @@ read_faxd(fz_stream *stm, unsigned char *buf, int len)
 	unsigned char *ep = buf + len;
 	unsigned char *tmp;
 
+	if (fax->stage == STATE_INIT && fax->end_of_line)
+	{
+		fill_bits(fax);
+		if ((fax->word >> (32 - 12)) != 1)
+		{
+			fz_warn(stm->ctx, "faxd stream doesn't start with EOL");
+			while (!fill_bits(fax) && (fax->word >> (32 - 12)) != 1)
+				eat_bits(fax, 1);
+		}
+		if ((fax->word >> (32 - 12)) != 1)
+			fz_throw(stm->ctx, FZ_ERROR_GENERIC, "initial EOL not found");
+	}
+
+	if (fax->stage == STATE_INIT)
+		fax->stage = STATE_NORMAL;
+
 	if (fax->stage == STATE_DONE)
 		return 0;
 
@@ -746,7 +763,7 @@ fz_open_faxd(fz_stream *chain,
 		fax->bidx = 32;
 		fax->word = 0;
 
-		fax->stage = STATE_NORMAL;
+		fax->stage = STATE_INIT;
 		fax->a = -1;
 		fax->c = 0;
 		fax->dim = fax->k < 0 ? 2 : 1;