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
@@ -152,48 +152,50 @@ var CLIPPERZ = module.exports = function(CONFIG) {
         if(req.session.u!=r.u.u_id) return cb(new Error('user/OTP mismatch'));
         PG.Q(
           "UPDATE clipperz.theotp AS otp"
          +" SET"
          +"  otps_id=CASE WHEN s.otps_code='REQUESTED' THEN ("
          +"   SELECT ss.otps_id FROM clipperz.otpstatus AS ss WHERE ss.otps_code='USED'"
          +"  ) ELSE otp.otps_id END,"
          +"  otp_utime=current_timestamp"
          +" FROM clipperz.otpstatus AS s, clipperz.theotp AS o"
          +" WHERE"
          +"  o.otp_id=otp.otp_id AND otp.otps_id=s.otps_id"
          +"  AND otp.otp_id=$1 AND otp.u_id=$2"
          +" 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));
        var A = BIGNUM(req.session.A,16);
        var S = A.mul(BIGNUM(req.session.v,16).powm(BIGNUM(u,16),srp_n)).powm(BIGNUM(req.session.b,16),srp_n);
        var K = clipperz_hash(S.toString(10));
        var M1 = clipperz_hash(
                  srp_hn
                  +clipperz_hash(req.session.C)
                  +BIGNUM(req.session.s,16).toString(10)
                  +A.toString(10)
                  +BIGNUM(req.session.B,16).toString(10)
                  +K );
        if(M1!=ppp.M1) return res.res({error:'?'});
        req.session.K = K;