XX-4101 / QR Code Panic Fix

Make auth request return an error instead of panic when the partner's DH public key is not in the E2E group

auth/request.go

@@ -137,6 +137,11 @@ func requestAuth(partner, me contact.Contact, rng io.Reader, reset bool,
 	sender := storage.GetUser().ReceptionID
 
 	//generate ownership proof
+	if !dhGrp.Inside(partner.DhPubKey.GetLargeInt()) {
+		return 0, errors.Errorf("partner's DH public key is not in the E2E "+
+			"group; E2E group fingerprint is %d and DH key has %d",
+			dhGrp.GetFingerprint(), partner.DhPubKey.GetGroupFingerprint())
+	}
 	ownership := cAuth.MakeOwnershipProof(originDHPrivKey, partner.DhPubKey,
 		dhGrp)
 	confirmFp := cAuth.MakeOwnershipProofFP(ownership)