CA/Changing Trust Settings

How To Override Default Root Certificate Settings

This page describes how to override the default root certificate settings in Mozilla products, including Firefox and Thunderbird.

See the Root Change Process if you are looking for instructions for changing default root certificates in Mozilla products.

When distributing binary and source code versions of Firefox, Thunderbird, and other Mozilla-related software products the Mozilla Foundation and its wholly-owned subsidiary the Mozilla Corporation include with such software a default set of X.509v3 certificates for various Certification Authorities (CAs). The certificates included by default have their "trust bits" set for various purposes, so that the software in question can use the CA certificates to verify certificates for SSL servers, S/MIME email users, and digitally-signed code objects without having to ask users for further permission or information.

CAs apply to have their root certificates included by default in Mozilla products by following the Mozilla CA Certificate Policy and applying for inclusion as per CA:How_to_apply.

Users of Mozilla products may override the default root certificate settings by either deleting the root certificate or by changing the trust bit settings of a root certificate. The sections below describe how to make these changes, and how the software responds to such changes.

Important: If you change the trust bit of a root certificate, that change will be permanent (can only be changed again by you) and will not be affected by upgrading to newer versions of the software. On the other hand, if you delete a root certificate that is in the default root store, that certificate may re-appear when you restart the program.

Changing Root Certificate Trust Bit Settings

Root certificates that are included by default have their "trust bits" set for various purposes, so that the software in question can use the CA certificates to verify certificates for SSL servers, S/MIME email users, and digitally-signed code objects without having to ask users for further permission or information.

The following describes how to change these settings in your installation of Firefox and Thunderbird.

Important: This change will be permanent, such that it can only be changed again by you. This change will not be affected by upgrading to newer versions of Mozilla software.

Caution: If you turn off the websites trust bit of a commonly used root certificate, you may get an "Untrusted Connection" error when you navigate to a website that you regularly use. Therefore, it is strongly recommended that you note which root certificate you modify, so that you can turn the trust bit back on if the change negatively impacts your browsing experience.

Firefox

1. Open the Options/Preferences window:
   • On Windows: Pull down the Tools menu and select Options…
   • On Mac: Pull down the Firefox menu and select Preferences...
   • On Linux: Pull down the Edit menu and select Preferences
2. Select Advanced
3. Select Encryption
4. Click on View Certificates to open the Certificate Manager
5. Select Authorities
   • Note: The root certificates with "Builtin Object Token" as the Security Device are the root certificates that are included by default in Mozilla products.
6. Select the Root Certificate that you want to change
7. Click on Edit...
8. Select/Unselect the check-boxes indicating the trust bits, then click on OK
9. Click on OK in the Certificate Manager
10. Close the Options/Preferences window
11. Close and restart Firefox

Thunderbird

1. Open the Options/Preferences window:
   • On Windows: Pull down the Tools menu and select Options…
   • On Mac: Pull down the Thunderbird menu and select Preferences...
   • On Linux: Pull down the Edit menu and select Preferences
2. Select Advanced
3. Select Certificates
4. Click on View Certificates to open the Certificate Manager
5. Select Authorities
   • Note: The root certificates with "Builtin Object Token" as the Security Device are the root certificates that are included by default in Mozilla products.
6. Select the Root Certificate that you want to change
7. Click on Edit...
8. Select/Unselect the check-boxes indicating the trust bits, then click on OK
9. Click on OK in the Certificate Manager
10. Close the Options/Preferences window
11. Close and restart Thunderbird

SeaMonkey

1. Open the Preferences window:
   • On Windows: Pull down the Edit menu and select Preferences
   • On Mac: Pull down the SeaMonkey menu and select Preferences...
   • On Linux: Pull down the Edit menu and select Preferences
2. Select Privacy & Security
3. Select Certificates
4. Click on Manage Certificates to open the Certificate Manager
5. Select Authorities
   • Note: The root certificates with "Builtin Object Token" as the Security Device are the root certificates that are included by default in Mozilla products.
6. Select the Root Certificate that you want to change
7. Click on Edit...
8. Select/Unselect the check-boxes indicating the trust bits, then click on OK
9. Click on OK in the Certificate Manager
10. Close the Preferences window
11. Close and restart SeaMonkey

Deleting a Root Certificate

When distributing binary and source code versions of Firefox, Thunderbird, and other Mozilla-related software products the Mozilla Foundation and its wholly-owned subsidiary the Mozilla Corporation include with such software a default set of X.509v3 certificates for various Certification Authorities (CAs).

The following describes how to delete a root certificate from your current instance of Firefox and Thunderbird.

Important: This change may be overridden when you restart the program. If the root certificate that you deleted is still in Mozilla's default root store, then the root certificate will be included again the next time you restart the program.

Firefox

1. Open the Options/Preferences window:
   • On Windows: Pull down the Tools menu and select Options…
   • On Mac: Pull down the Firefox menu and select Preferences...
   • On Linux: Pull down the Edit menu and select Preferences
2. Select Advanced
3. Select Encryption
4. Click on View Certificates to open the Certificate Manager
5. Select Authorities
   • Note: The root certificates with "Builtin Object Token" as the Security Device are the root certificates that are included by default in Mozilla products.
6. Select the Root Certificate that you want to delete
7. Click on Delete...
8. If you are sure you want to delete that root certificate, click on OK
9. Click on OK in the Certificate Manager
10. Close the Options/Preferences window

Thunderbird

1. Open the Options/Preferences window:
   • On Windows: Pull down the Tools menu and select Options…
   • On Mac: Pull down the Thunderbird menu and select Preferences...
   • On Linux: Pull down the Edit menu and select Preferences
2. Select Advanced
3. Select Certificates
4. Click on View Certificates to open the Certificate Manager
5. Select Authorities
   • Note: The root certificates with "Builtin Object Token" as the Security Device are the root certificates that are included by default in Mozilla products.
6. Select the Root Certificate that you want to delete
7. Click on Delete...
8. If you are sure you want to delete that root certificate, click on OK
9. Click on OK in the Certificate Manager
10. Close the Options/Preferences window

SeaMonkey

1. Open the Preferences window:
   • On Windows: Pull down the Edit menu and select Preferences
   • On Mac: Pull down the SeaMonkey menu and select Preferences...
   • On Linux: Pull down the Edit menu and select Preferences
2. Select Privacy & Security
3. Select Certificates
4. Click on Manage Certificates to open the Certificate Manager
5. Select Authorities
   • Note: The root certificates with "Builtin Object Token" as the Security Device are the root certificates that are included by default in Mozilla products.
6. Select the Root Certificate that you want to delete
7. Click on Delete...
8. If you are sure you want to delete that root certificate, click on OK
9. Click on OK in the Certificate Manager
10. Close the Preferences window

How Mozilla Products Respond to User Changes of Root Certificates

The following explains how Mozilla products behave when users change or delete root certificates.

For simplicity, the following assumes the basic and most common configuration, in which you have only the software distributed by Mozilla and do not have any additional PKCS#11 modules (with or without any additional hardware) installed that may be capable of storing additional certificates. The model with them is slightly more complicated than the one described here.

Network Security Services (NSS) is capable of accessing certificates that have been stored in a number of places, all accessible through the PKCS#11 API. The two places of greatest interest are

1. Your certificate database, which is kept in a file on disk that you can alter. It starts out empty. Any root certificates it contains are there because of actions that you have taken, such as downloading or importing roots, or editing trust flags. As a rule, an update to your Mozilla installation of a Mozilla product will not change the contents of this database. (Rarely, it may change the FORMAT of the database, but not the content.)
2. Mozilla's trusted root list, kept in a read-only shared library which is one of the files that gets updated whenever your product's executable files get updated.

Both of these stores of certificates may contain certificates and trust flags.

When NSS goes looking for a stored certificate, or trust flags for a stored certificate, it first looks in your certificate database. If it finds the certificate there, it stops. It uses whatever trust flags are there in that database with that certificate.

If it does NOT find the certificate it wants in that database, it looks in Mozilla's trusted root list. If it finds the cert there, then it uses the cert and trust flags it finds there. It does not copy the cert and flags from the root list into your database. It just uses them where and as they are.

When you use your product's certificate manager to edit the trust flags on a certificate, the cert manager first looks for the cert in your database, and if it's there, then that copy gets edited. If it's not there, then cert manager looks for a copy in the trusted cert list, and if found, copies it and its flags into your data base, and then edits it there. (After all, it cannot edit the copy in Mozilla's list, because that copy is read-only.) After that, that cert will remain in your database, and each time that the product goes looking for it, it will find it in your database, not in the trusted list.

If you delete a cert in your database, one that is also in the trusted list, it may appear to be completely gone, until you restart your program, at which point it will reappear, because it never left the trusted root list. It may reappear in the trusted root list with the trust flags from that list. That's why we tell people that if they want to get rid of a root, the thing to do is NOT to delete it, but rather is to take away all its trust. (The behavior when a cert is deleted has changed a few times over the years.)

If you edit the trust on a cert in the root list, taking away (say) one of the 3 trust flags, but leaving the other two, then that cert and the two trust bits will be in your cert DB. After that, if Mozilla removes that cert completely from Mozilla's trust list, it will remain in your cert DB with those two trust flags. Mozilla's changes to the default trust list never affect your databases. Your databases contain what YOU put there. They're your changes, your responsibility.

In conclusion, the changes Mozilla makes to Mozilla's read-only list of trusted root certs affect only those certs that do not also appear in your cert DB. When you cause copies of any of those certs to appear in your cert DB, then you have taken control of the trust for those copies, and changes made by Mozilla thereafter to those certs will not affect you.