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
@@ -164,24 +164,26 @@ var CLIPPERZ = module.exports = function(CONFIG) {
 	 +" RETURNING o.otps_id!=otp.otps_id AS yes, o.otp_ref",
 	 [ req.session.otp, req.session.u ],
 	 function(e,r) {
 	 if(e) return cb(e);
 	 if(!r.rowCount) return cb(new Error('no OTP found'));
 	 r=r.rows[0];
 	 if(!r.yes) return cb(new Error('OTP is in a sorry state'));
 	 cb(null,{ref:r.otp_ref});
 	});
        }]
       },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;
        req.session.b = clipperz_random();
        req.session.B = srp_k.mul(BIGNUM(req.session.v,16)).add(srp_g.powm(BIGNUM(req.session.b,16),srp_n)).toString(16);
        var rv = {s:req.session.s,B:req.session.B}
        if(r.otp && r.otp.otp_ref) rv.oneTimePassword=r.otp.otp_ref;
        res.res(rv);
       });
  
       case 'credentialCheck':
        var u = clipperz_hash(BIGNUM(req.session.A,16).toString(10)+BIGNUM(req.session.B,16).toString(10));