[Fedora-directory-users] NSPR "Certificate type not approved for application" error when a TLS-enabled proxy LDAP OpenLDAP server connects to Fedora Directory Server
Hi!
I have a proxy OpenLDAP server (based on slapd-ldap) backend that connects to Fedora Directory server.
All is fine if OpenLDAP is configured to connect using non-SSL URI without TLS.
However, whenever I try TLS on port 389 or SSL on port 636, OpenLDAP uses its server certificate during TLS/SSL negotiation and Fedora Directory decides that this certificate usage isn't good because it's not a client certificate. In FDS logs I can see:
[14/Apr/2008:11:33:33 +0200] conn=1474 fd=65 slot=65 SSL connection from IP_OF_OPENLDAP to IP_OF_FDS [14/Apr/2008:11:33:33 +0200] conn=1474 Netscape Portable Runtime error -8101 (Certificate type not approved for application.); unauthenticated client E=some_email,CN=hostname,ETC,ETC,; issuer E=ISSUER_DATA [14/Apr/2008:11:33:33 +0200] conn=1474 op=-1 fd=65 closed - Certificate type not approved for application.
Is there a way to relax those requirements in Fedora Directory for this particular case (LDAP client that uses a server certificate)? Like, say some tweaks in nss.conf?
Aleksander Adamowski wrote:
However, whenever I try TLS on port 389 or SSL on port 636, OpenLDAP uses its server certificate during TLS/SSL negotiation and Fedora Directory decides that this certificate usage isn't good because it's not a client certificate. In FDS logs I can see: [..] [14/Apr/2008:11:33:33 +0200] conn=1474 Netscape Portable Runtime error -8101 (Certificate type not approved for application.); unauthenticated client E=some_email,CN=hostname,ETC,ETC,; issuer E=ISSUER_DATA [14/Apr/2008:11:33:33 +0200] conn=1474 op=-1 fd=65 closed - Certificate type not approved for application.
I guess this is because of wrong X.509v3 cert extensions. Maybe you should post a text dump of the public-key cert.
openssl x509 -in certfilename.pem -noout -text
Ciao, Michael.
Aleksander Adamowski wrote:
Hi!
I have a proxy OpenLDAP server (based on slapd-ldap) backend that connects to Fedora Directory server.
All is fine if OpenLDAP is configured to connect using non-SSL URI without TLS.
However, whenever I try TLS on port 389 or SSL on port 636, OpenLDAP uses its server certificate during TLS/SSL negotiation and Fedora Directory decides that this certificate usage isn't good because it's not a client certificate. In FDS logs I can see:
[14/Apr/2008:11:33:33 +0200] conn=1474 fd=65 slot=65 SSL connection from IP_OF_OPENLDAP to IP_OF_FDS [14/Apr/2008:11:33:33 +0200] conn=1474 Netscape Portable Runtime error -8101 (Certificate type not approved for application.); unauthenticated client E=some_email,CN=hostname,ETC,ETC,; issuer E=ISSUER_DATA [14/Apr/2008:11:33:33 +0200] conn=1474 op=-1 fd=65 closed - Certificate type not approved for application.
Is there a way to relax those requirements in Fedora Directory for this particular case (LDAP client that uses a server certificate)?
Do you need to use cert based auth? If not, just configure the application to not use cert. based auth - just use username/password auth over SSL (or TLS). If you must use cert. based auth, you may be able to use the certutil command to change the trust flags of the cert - see certutil -H. See also this page for information about cert. based auth - http://directory.fedoraproject.org/wiki/Howto:CertMapping
Like, say some tweaks in nss.conf?
NSS (Netscape^H^H^H^H^Hwork Security Services) for crypto and nss (name switch service - as in nss_ldap) are completely different and unfortunately share the same name.
Rich Megginson wrote:
Do you need to use cert based auth? If not, just configure the application to not use cert. based auth - just use username/password auth over SSL (or TLS). If you must use cert. based auth, you may be able to use the certutil command to change the trust flags of the cert
- see certutil -H. See also this page for information about cert.
based auth - http://directory.fedoraproject.org/wiki/Howto:CertMapping
Hmm, this has given me an idea for a solution. After switching Encryption -> Client Authentication settings of dirsrv from "Allow client authentication" to "Do not allow client authentication" I got this working.
It seems that whenever certificate authentication is an allowed possibility on the FDS server side, OpenLDAP client tries using it even if it is operating inside an OpenLDAP server environment (in which case it supplies its server certificate as client's - thus the problem).
This case is special since OpenLDAP server acts as an LDAP client to FDS server. I think the problem is on OpenLDAP side (it shouldn't use its server certificate for client authentication when acting as an LDAP client).
Like, say some tweaks in nss.conf?
NSS (Netscape^H^H^H^H^Hwork Security Services) for crypto and nss (name switch service - as in nss_ldap) are completely different and unfortunately share the same name.
Read carefully: I wasn't talking about nsswitch.conf (which is for Name Service Switch), but nss.conf (which is a config file for mod_nss which is based on Network Secirity Services library).
The FDS admin server (dirsrv-admin) is based on Apache and it uses mod_nss for handling SSL connections. So inside /etc/dirsrv/admin-serv/nss.conf you can tweak SSL-related behaviour of dirsrv-admin.
I thought that there might be a similar method to tweak behaviour of dirsrv (although not through nss.conf since dirsrv doesn't use mod_nss and doesn't contain a http server in any part ), like some undocumented setting in dse.ldif. However, more correct fix turned out to be disallow certificate-based client authentication.
Aleksander Adamowski wrote:
Rich Megginson wrote:
Do you need to use cert based auth? If not, just configure the application to not use cert. based auth - just use username/password auth over SSL (or TLS). If you must use cert. based auth, you may be able to use the certutil command to change the trust flags of the cert - see certutil -H. See also this page for information about cert. based auth - http://directory.fedoraproject.org/wiki/Howto:CertMapping
Hmm, this has given me an idea for a solution. After switching Encryption -> Client Authentication settings of dirsrv from "Allow client authentication" to "Do not allow client authentication" I got this working.
It seems that whenever certificate authentication is an allowed possibility on the FDS server side, OpenLDAP client tries using it even if it is operating inside an OpenLDAP server environment (in which case it supplies its server certificate as client's - thus the problem).
This case is special since OpenLDAP server acts as an LDAP client to FDS server. I think the problem is on OpenLDAP side (it shouldn't use its server certificate for client authentication when acting as an LDAP client).
That should be fine. Fedora DS can do the same thing e.g. with server-to-server chaining and replication, using the server cert for client cert auth. It just depends on the type of cert issued and/or the trust flags on the cert.
Like, say some tweaks in nss.conf?
NSS (Netscape^H^H^H^H^Hwork Security Services) for crypto and nss (name switch service - as in nss_ldap) are completely different and unfortunately share the same name.
Read carefully: I wasn't talking about nsswitch.conf (which is for Name Service Switch), but nss.conf (which is a config file for mod_nss which is based on Network Secirity Services library).
The FDS admin server (dirsrv-admin) is based on Apache and it uses mod_nss for handling SSL connections. So inside /etc/dirsrv/admin-serv/nss.conf you can tweak SSL-related behaviour of dirsrv-admin.
Ok. I thought we were talking about the directory server only.
I thought that there might be a similar method to tweak behaviour of dirsrv (although not through nss.conf since dirsrv doesn't use mod_nss and doesn't contain a http server in any part ), like some undocumented setting in dse.ldif. However, more correct fix turned out to be disallow certificate-based client authentication.
See the RHDS 8.0 Admin Guide, Chapter 12 - http://www.redhat.com/docs/manuals/dir-server/ag/8.0/ and http://tinyurl.com/688w9y
See also the detailed information for all of the security/encryption configuration entries and attributes - http://tinyurl.com/35qddb - there is also an apparently undocumented entry cn=RSA, cn=encryption, cn=config.
Rich Megginson wrote:
That should be fine. Fedora DS can do the same thing e.g. with server-to-server chaining and replication, using the server cert for client cert auth. It just depends on the type of cert issued and/or the trust flags on the cert.
If I understand correctly you're implying that server2server ssl connections are handled with the same logic that client2server ssl?
Then it's strange, since I'm using multi-master replication with all s2s connections using SSL (port 636). I've generated all the certificates (for FDS servers and for OpenLDAP servers) using the same OpenSSL CA openssl.cnf config file (but a slightly different configuration section WRT subjectAltName field - see below).
The relevant fields of the OpenLDAP server's certificate are:
X509v3 extensions: X509v3 Basic Constraints: CA:FALSE Netscape Cert Type: SSL Server ... X509v3 Subject Alternative Name: email:postmaster@MY_DOMAIN_NAME
While the same fields of the FDS certificate are:
X509v3 extensions: X509v3 Basic Constraints: CA:FALSE Netscape Cert Type: SSL Server ... X509v3 Subject Alternative Name: DNS:servername2.MY_DOMAIN_NAME, DNS:servername3.MY_DOMAIN_NAME
Other differences are only in key length, crypto algorithms and values of serial numbers, fingerprint etc.
So the only one possibly relevant difference is that in OpenLDAP's cert the subjectAltName field contains an e-mail address and in Fedora Directory Server's it contains alternative DNS host names of the FDS server. Might it be the cause?
I thought that there might be a similar method to tweak behaviour of dirsrv (although not through nss.conf since dirsrv doesn't use mod_nss and doesn't contain a http server in any part ), like some undocumented setting in dse.ldif. However, more correct fix turned out to be disallow certificate-based client authentication.
See the RHDS 8.0 Admin Guide, Chapter 12 - http://www.redhat.com/docs/manuals/dir-server/ag/8.0/ and http://tinyurl.com/688w9y
See also the detailed information for all of the security/encryption configuration entries and attributes - http://tinyurl.com/35qddb - there is also an apparently undocumented entry cn=RSA, cn=encryption, cn=config.
Yup, I've read that but there isn't anything conclusive over there. I was counting on some undocumented configuration attribute that would control which usages are allowed in client x.509 certs.
Aleksander Adamowski wrote:
Rich Megginson wrote:
That should be fine. Fedora DS can do the same thing e.g. with server-to-server chaining and replication, using the server cert for client cert auth. It just depends on the type of cert issued and/or the trust flags on the cert.
If I understand correctly you're implying that server2server ssl connections are handled with the same logic that client2server ssl?
What I meant was that the server handles any client cert based auth the same way, regardless of whether the "client" is a user or another server.
Then it's strange, since I'm using multi-master replication with all s2s connections using SSL (port 636). I've generated all the certificates (for FDS servers and for OpenLDAP servers) using the same OpenSSL CA openssl.cnf config file (but a slightly different configuration section WRT subjectAltName field - see below).
The relevant fields of the OpenLDAP server's certificate are:
X509v3 extensions: X509v3 Basic Constraints: CA:FALSE Netscape Cert Type: SSL Server... X509v3 Subject Alternative Name: email:postmaster@MY_DOMAIN_NAME
While the same fields of the FDS certificate are:
X509v3 extensions: X509v3 Basic Constraints: CA:FALSE Netscape Cert Type: SSL Server... X509v3 Subject Alternative Name: DNS:servername2.MY_DOMAIN_NAME, DNS:servername3.MY_DOMAIN_NAME
Other differences are only in key length, crypto algorithms and values of serial numbers, fingerprint etc.
So the only one possibly relevant difference is that in OpenLDAP's cert the subjectAltName field contains an e-mail address and in Fedora Directory Server's it contains alternative DNS host names of the FDS server. Might it be the cause?
I'm not sure how NSS handles certificate verification with subjectAltName. I know that in order for the validation to work without subjectAltName, the leftmost RDN in the subjectDN must be cn=FQDN of the server e.g. cn=ldap1.example.com, ou=Fedora Directory Server, dc=example, dc=com
I'm also not sure if that applies to cert based auth.
I thought that there might be a similar method to tweak behaviour of dirsrv (although not through nss.conf since dirsrv doesn't use mod_nss and doesn't contain a http server in any part ), like some undocumented setting in dse.ldif. However, more correct fix turned out to be disallow certificate-based client authentication.
See the RHDS 8.0 Admin Guide, Chapter 12 - http://www.redhat.com/docs/manuals/dir-server/ag/8.0/ and http://tinyurl.com/688w9y
See also the detailed information for all of the security/encryption configuration entries and attributes - http://tinyurl.com/35qddb - there is also an apparently undocumented entry cn=RSA, cn=encryption, cn=config.
Yup, I've read that but there isn't anything conclusive over there. I was counting on some undocumented configuration attribute that would control which usages are allowed in client x.509 certs.
Ok. I'm not sure what NSS is complaining about here. If NSS is complaining about the hostname in the subjectDN or the subjectAltName doesn't match the actual server, I don't think that makes sense in the context of cert based auth, since a client will usually not have an associated FQDN. So I believe it's complaining that the cert was not issued as an SSL client cert. I do know that you can issue a cert that can be used for both SSL server and SSL client use. I'm not sure if you can use certutil -M to modify the trust flags of a server cert after issuance to allow it to be used for SSL client use. The guys at news.mozilla.org:mozilla.dev.tech.crypto would know for sure.
Finally, there doesn't appear to be a way in Fedora DS to allow other types of certificates to be used for client cert auth, or to ignore problems of this nature.
Rich Megginson wrote:
I'm not sure how NSS handles certificate verification with subjectAltName. I know that in order for the validation to work without subjectAltName, the leftmost RDN in the subjectDN must be cn=FQDN of the server e.g. cn=ldap1.example.com, ou=Fedora Directory Server, dc=example, dc=com
Yes, for server certs which are validated by the client.
I'm also not sure if that applies to cert based auth.
It doesn't.
Ciao, Michael.
Aleksander Adamowski wrote:
The relevant fields of the OpenLDAP server's certificate are:
What about the keyUsage and extendedKeyUsage extensions?
Ciao, Michael.
Michael Ströder wrote:
Aleksander Adamowski wrote:
The relevant fields of the OpenLDAP server's certificate are:
What about the keyUsage and extendedKeyUsage extensions?
Ciao, Michael.
These aren't present, unfortunately.
I didn't place keyUsage in the openssl.cnf section used for server certificates...
Aleksander Adamowski wrote:
Michael Ströder wrote:
Aleksander Adamowski wrote:
The relevant fields of the OpenLDAP server's certificate are:
What about the keyUsage and extendedKeyUsage extensions?
These aren't present, unfortunately.
IIRC they have to be defined.
Example lines for openssl.cnf: keyUsage = digitalSignature,keyEncipherment extendedKeyUsage = serverAuth
Ciao, Michael.
Aleksander Adamowski wrote:
It seems that whenever certificate authentication is an allowed possibility on the FDS server side, OpenLDAP client tries using it even if it is operating inside an OpenLDAP server environment (in which case it supplies its server certificate as client's - thus the problem).
OpenLDAP client lib supplies the client cert which was configured for back-ldap. Check OpenLDAP's ldap.conf or slapd.conf and the relevant man-pages.
I think the problem is on OpenLDAP side (it shouldn't use its server certificate for client authentication when acting as an LDAP client).
I think the problem is with your particular configuration and the certs you're using.
Ciao, Michael.
Michael Ströder wrote:
Aleksander Adamowski wrote:
It seems that whenever certificate authentication is an allowed possibility on the FDS server side, OpenLDAP client tries using it even if it is operating inside an OpenLDAP server environment (in which case it supplies its server certificate as client's - thus the problem).
OpenLDAP client lib supplies the client cert which was configured for back-ldap. Check OpenLDAP's ldap.conf or slapd.conf and the relevant man-pages. \
The point is that there's _no_ client cert, I don't intend to have mutual authentication here - I'd like slapd-ldap _not_ authenticate itself with a certificate. I'd like it to behave like an ordinary certificate-less client. But it chooses to use its server certificate to authenticate itself as a client to FDS server.
I don't see any options to force _no client authentication_ - neither in slapd-ldap(5), nor slapd.conf(5), nor ldap.conf(5).
I'm using OpenLDAP 2.3.39.
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