reject zero A from the client (as per CLP-01-017)

1 files changed, 2 insertions, 0 deletions

diff --git a/backend/node/src/clipperz.js b/backend/node/src/clipperz.js
index 72b6c9f..842de31 100644
--- a/backend/node/src/clipperz.js
+++ b/backend/node/src/clipperz.js
@@ -173,6 +173,8 @@ var CLIPPERZ = module.exports = function(CONFIG) {
        }]
       },function(e,r) {
        if(e) return cb(e);
+       var A = BIGNUM(ppp.A,16);
+       if(A.eq(0)) return cb(new Error('Ground Zero'));
        req.session.C = ppp.C; req.session.A = ppp.A;
        req.session.s = r.u.u_srp_s; req.session.v = r.u.u_srp_v;
        req.session.u = r.u.u_id;