MFC r265095, r265167;

citrus: Avoid invalid code points.

The UTF-8 decoder should not accept byte sequences which decode to
unicode code positions U+D800 to U+DFFF (UTF-16 surrogates).[1]

Contrary to the original OpenBSD patch, we do pass U+FFFE and U+FFFF,
both values are valid "non-characters" [2] and must be mapped through
UTFs.

[1] http://www.cl.cam.ac.uk/~mgk25/unicode.html#utf-8
[2] http://www.unicode.org/faq/private_use.html

Reported by:	Stefan Sperling [1]
Thanks to:	jilles [2]
Obtained from:	OpenBSD

1 files changed, 7 insertions, 0 deletions

diff --git a/lib/libc/locale/utf8.c b/lib/libc/locale/utf8.c
index 40f0e17..cffa241 100644
--- a/lib/libc/locale/utf8.c
+++ b/lib/libc/locale/utf8.c
@@ -203,6 +203,13 @@ _UTF8_mbrtowc(wchar_t * __restrict pwc, const char * __restrict s, size_t n,
 		errno = EILSEQ;
 		return ((size_t)-1);
 	}
+	if (wch >= 0xd800 && wch <= 0xdfff) {
+		/*
+		 * Malformed input; invalid code points.
+		 */
+		errno = EILSEQ;
+		return ((size_t)-1);
+	}
 	if (pwc != NULL)
 		*pwc = wch;
 	us->want = 0;