Fix a null-pointer dereference in establish_http_proxy_passthru()

Prevents that the client crashes if the peer does not specify
the 'realm' and/or 'nonce' values. These pointers are
dereferenced in DigestCalcHA1() and DigestCalcResponse();
hence, if not set, a null-pointer dereference would occur.

Signed-off-by: Guido Vranken <guidovranken@gmail.com>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <1497574736-2092-1-git-send-email-gv@guidovranken.nl>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg14844.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>
(cherry picked from commit 14865773ad64d861128bc80ad44c37bdc307c996)
(cherry picked from commit 479b6d13d8c230c11b6315665bf00998a1424eef)

diff --git a/proxy.c b/proxy.c
index 0502ce99ff45c7eeb5e7c9eeb62700d9913739ad..72f64cd60d91cc8990586ba0aebfd8853a0cb7f3 100644 (file)
--- a/proxy.c
+++ b/proxy.c
@@ -745,6 +745,12 @@ establish_http_proxy_passthru (struct http_proxy_info *p,
              const char *algor = get_pa_var("algorithm", pa, &gc);
              const char *opaque = get_pa_var("opaque", pa, &gc);
 
+             if ( !realm || !nonce )
+               {
+                 msg(D_LINK_ERRORS, "HTTP proxy: digest auth failed, malformed response from server: realm= or nonce= missing" );
+                 goto error;
+               }
+
              /* generate a client nonce */
              ASSERT(RAND_bytes(cnonce_raw, sizeof(cnonce_raw)));
              cnonce = make_base64_string2(cnonce_raw, sizeof(cnonce_raw), &gc);