CA/Changing Trust Settings

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

If you are seeing "Your connection is not secure" errors and you don't know why, visit this support page.

Some browsers only display the root certificates that the user has actually used, and dynamically download new ones on demand. However, Mozilla believes it is important for users to know the root certificates that could be used, so the full set of certificates is always shown. This also allows you to edit the trust bits for any root certificates that you do not want to use.


Important Warnings

Following instructions on this page may negatively affect your security and/or your browsing experience.

If you turn off the websites trust bit of a commonly used root certificate, you may get an "Your connection is not secure" error when you navigate to one or more popular websites. Bypassing such errors can be a security risk unless you know what you are doing. 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.

If you change the trust bits of a root certificate or add or delete roots, that change will be will not be affected by upgrading to newer versions of the software. It can only be changed again by you.

Deleting a root certificate that is in the default root store is equivalent to turning off all of the trust bits for that root. Therefore, even though the root certificate will re-appear in the Certificate Manager, it will be treated as though you changed the trust bits of that root certificate to turn them all off.

Trusting an Additional Root Certificate

The following describes how to manually import a root certificate into your installation of Firefox or other Mozilla products.

  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 Privacy & Security
  3. Scroll down to the Certificates section
  4. Click on View Certificates.. to open the Certificate Manager
  5. Select Authorities tab
    • 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. Click on Import...
  7. Select the file of the Root Certificate that you want to import
  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 tab

Changing Root Certificate Trust Settings

To change the trust settings for root certificates in your installation of Firefox or other Mozilla products, follow the instructions above, except when you are in the Authorities tab of the Certificate Manager:

  1. Select the Root Certificate that you want to change
  2. Click on Edit Trust...
  3. Select/Unselect the check-boxes indicating the trust bits, then click on OK

Close and restart Firefox

Deleting a Root Certificate

To delete a root certificate from your current instance of Firefox or other Mozilla products, follow the instructions above, except when you are in the Authorities tab of the Certificate Manager:

  1. Select the Root Certificate that you want to delete
  2. Click on Delete or Distrust...
  3. If you are sure you want to delete that root certificate, click on OK

Close and restart Firefox

Restoring the Default Trust Settings for All Root Certificates

Restoring the Default Trust Settings for a Single Root Certificate

If you want the cert to again respect any updates Mozilla makes to the default root store, this is extremely difficult. It is far easier to reset the entire store using the instructions above.

Deeply Geeky Certificate Database Information

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 built-in 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 built-in 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 built-in 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 built-in root 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 the built-in 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 built-in list.

If you delete a cert in your database that is also in the built-in list, it may appear to be completely gone, until you restart your program, at which point it will reappear, because it never left the built-in root list. However, the trust bits will be turned off for the root.

If you edit the trust on a cert in the root list, taking away (say) one of the 2 trust flags, but leaving the other one, then that cert and the single trust bit will be in your cert DB. After that, if Mozilla removes that cert completely from the built-in list, it will remain in your cert DB with the remaining trust flag. Mozilla's changes to the built-in 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 built-in 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.

Restoring the Default Trust Bits for a Single Built-In Root Certificate

If you have edited the trust bits of a built-in root certificate, causing it to be copied to your personal database, you may wish to delete the copy from your database so that the default trust bits are again used. (Simply editing the trust bits to match the defaults would not give you the benefit of any updates Mozilla may later make to the defaults.) There is currently no UI to do this (bug 558222), but you can use the NSS certutil command-line tool. certutil does not ship with Mozilla products, and NSS itself does not have official binary releases at this time, but you can build certutil from source, or your OS distribution may include it (Fedora: nss-tools, Debian/Ubuntu: libnss3-tools).

To delete a certificate from your personal database:

  1. Note the Certificate Name as shown in the Certificate Manager.
  2. Locate your profile.
  3. Shut down the Mozilla application.
  4. Run:
    # for older Mozilla products, leave off the `sql:` part
    certutil -d sql:PROFILE_DIR -D -n CERT_NAME
    substituting PROFILE_DIR with the path of your profile directory and CERT_NAME with the certificate name.
  5. Restart the Mozilla application.

Listing All Non-Default Root Certificate Settings

There is currently no UI to list all built-in root certificates for which you have overridden the default trust settings (bug 545498). However, you can use the certutil tool described in the previous section to list all the certificates in your personal database, which includes built-in root certificates whose trust you have changed along with added root certificates and many other kinds of certificates.

Run this command (doing it while the Mozilla application is running is probably unsupported but does not seem to cause problems in practice):

# for older Mozilla products, leave off the 'sql:' part
certutil -d sql:PROFILE_DIR -L

where PROFILE_DIR is the path to your profile as noted above.

Root certificates will have trust fields of c, indicating a disabled trust bit, or CT or C, indicating an enabled trust bit. For example:

Certificate Nickname                                         Trust Attributes

My Favorite CA                                               CT,c,c
Wiretaps R Us CA                                             c,c,c