url: do not read past end of buffer

url_decode_internal could have been tricked into reading past the length
of the **query buffer if there are fewer than 2 characters after a % (in
a null-terminated string, % would have to be the last character).
Prevent this from happening by checking len before decoding the %
sequence.

Helped-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Matthew DeVore <matvore@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/url.c b/url.c
index 25576c390baa79cb0a203d7f682e8f3442f91a60..9ea9d5611b73c024b42b0808841a143d50905b14 100644 (file)
--- a/url.c
+++ b/url.c
@@ -46,7 +46,7 @@ static char *url_decode_internal(const char **query, int len,
                        break;
                }
 
-               if (c == '%') {
+               if (c == '%' && (len < 0 || len >= 3)) {
                        int val = hex2chr(q + 1);
                        if (0 <= val) {
                                strbuf_addch(out, val);