commit 669790f191189a4e1c9416572909dd3a158547f5
from: xentrac <xentrac@special-circumstanc.es>
date: Fri Feb 26 04:01:06 2021 UTC

Report incorrect /Filter type with decode failure

Previously, when the instigator produced a PDF file with a stream with
`<</Filter 718>>` in its stream dictionary, pdf was failing by
aborting with an assert failure.  An assert failure is not the right
way to report that the program’s input is invalid.  This change simply
returns NULL from `decode_stream` in this case.

commit - c9ab81f899e5ed4668d95cf5d250364c5ba50922
commit + 669790f191189a4e1c9416572909dd3a158547f5
blob - c2d370e2a67ee3320b3b7ed10179087ef21e2ecb
blob + a559b5fa565035ded75e18332670c06ebd382dc4
--- pdf.c
+++ pdf.c
@@ -1902,9 +1902,12 @@ decode_stream(const Dict *d, HBytes b, HParser *p)
 		errx(1, "stream data parser: LL(1) compile failed");
 #endif
 
-	if (v->token_type == TT_SEQUENCE)
-		return NULL;	// XXX filter chains not supported, yet
-	assert(v->token_type == TT_BYTES);
+	if (v->token_type != TT_BYTES) {
+		// XXX TT_SEQUENCE would be a filter chains; that’s not supported, yet.
+		// But it might also be something bogus, in which case we should fail.
+		return NULL;
+	}
+
 	if (bytes_eq(v->bytes, "FlateDecode"))
 		filter = FlateDecode;
 	else if (bytes_eq(v->bytes, "ASCIIHexDecode"))