Configuring Keystone for Tokenless Authorization¶
Definitions¶
X.509 Tokenless Authorization: Provides a means to authorize client operations within Keystone by using an X.509 SSL client certificate without having to issue a token.
This feature is designed to reduce the complexity of user token validation in Keystone
auth_tokenmiddleware by eliminating the need for service user token for authentication and authorization. Therefore, there’s no need to having to create and maintain a service user account for the sole purpose of user token validation. Furthermore, this feature improves efficiency by avoiding service user token handling (i.e. request, cache, and renewal). By not having to deal with service user credentials in the configuration files, deployers are relieved of the burden of having to protect the server user passwords throughout the deployment lifecycle. This feature also improve security by using X.509 certificate instead of password for authentication.For details, please refer to the specs Tokenless Authorization with X.509 Client SSL Certificate
Public Key Infrastructure or PKI: a system which utilize public key cryptography to achieve authentication, authorization, confidentiality, integrity, non-repudiation. In this system, the identities are represented by public key certificates. Public key certificate handling is governed by the X.509 standard.
See Public Key Infrastructure and X.509 for more information.
X.509 Certificate: a time bound digital identity, which is certified or digitally signed by its issuer using cryptographic means as defined by the X.509 standard. It contains information which can be used to uniquely identify its owner. For example, the owner of the certificate is identified by the
Subjectattribute while the issuer is identified byIssuerattribute.In operation, certificates are usually stored in Privacy-Enhanced Mail (PEM) format.
Here’s an example of what a certificate typically contains:
Certificate: Data: Version: 3 (0x2) Serial Number: 4098 (0x1002) Signature Algorithm: sha256WithRSAEncryption Issuer: DC = com, DC = somedemo, O = openstack, OU = keystone, CN = Intermediate CA Validity Not Before: Jul 5 18:42:01 2019 GMT Not After : Jul 2 18:42:01 2029 GMT Subject: DC = com, DC = somedemo, O = Default, OU = keystone, CN = glance Subject Public Key Info: Public Key Algorithm: rsaEncryption Public-Key: (2048 bit) Modulus: 00:cf:35:8b:cd:4f:17:28:38:25:f7:e2:ac:ce:4e: d7:05:74:2f:99:04:f8:c2:13:14:50:18:70:d6:b0: 53:62:15:60:59:99:90:47:e2:7e:bf:ca:30:4a:18: f5:b8:29:1e:cc:d4:b8:49:9c:4a:aa:d9:10:b9:d7: 9f:55:85:cf:e3:44:d2:3c:95:42:5a:b0:53:3e:49: 9d:6b:b2:a0:9f:72:9d:76:96:55:8b:ee:c4:71:46: ab:bd:12:71:42:a0:60:29:7a:66:16:e1:fd:03:17: af:a3:c7:26:c3:c3:8b:a7:f9:c0:22:08:2d:e4:5c: 07:e1:44:58:c1:b1:88:ae:45:5e:03:10:bb:b4:c2: 42:52:da:4e:b5:1b:d6:6f:49:db:a4:5f:8f:e5:79: 9f:73:c2:37:de:99:a7:4d:6f:cb:b5:f9:7e:97:e0: 77:c8:40:21:40:ef:ab:d3:55:72:37:6c:28:0f:bd: 37:8c:3a:9c:e9:a0:21:6b:63:3f:7a:dd:1b:2c:90: 07:37:66:86:66:36:ef:21:bb:43:df:d5:37:a9:fa: 4b:74:9a:7c:4b:cd:8b:9d:3b:af:6d:50:fe:c9:0a: 25:35:c5:1d:40:35:1d:1f:f9:10:fd:b6:5c:45:11: bb:67:11:81:3f:ed:d6:27:04:98:8f:9e:99:a1:c8: c1:2d Exponent: 65537 (0x10001) X509v3 extensions: X509v3 Basic Constraints: CA:FALSE Netscape Cert Type: SSL Client, S/MIME Netscape Comment: OpenSSL Generated Client Certificate X509v3 Subject Key Identifier: EE:38:FB:60:65:CD:81:CE:B2:01:E3:A5:99:1B:34:6C:1A:74:97:BB X509v3 Authority Key Identifier: keyid:64:17:77:31:00:F2:ED:90:9A:A8:1D:B5:7D:75:06:03:B5:FD:B9:C0 X509v3 Key Usage: critical Digital Signature, Non Repudiation, Key Encipherment X509v3 Extended Key Usage: TLS Web Client Authentication, E-mail Protection Signature Algorithm: sha256WithRSAEncryption 82:8b:17:c6:f4:63:eb:8d:69:03:7a:bf:54:7f:37:02:eb:94: ef:57:fd:27:8f:f8:67:e9:0e:3b:0a:40:66:11:68:e6:04:1a: 8a:da:47:ed:83:eb:54:34:3b:5b:70:18:cf:62:e2:6d:7c:74: 4c:cf:14:b3:a9:70:b2:68:ed:19:19:71:6f:7d:87:22:38:8d: 83:c6:59:15:74:19:5b:a2:64:6f:b9:9a:81:3d:0a:67:58:d1: e2:b2:9b:9b:8f:60:7a:8c:0e:61:d9:d7:04:63:cc:58:af:36: a4:61:86:44:1c:64:e2:9b:bd:f3:21:87:dd:18:81:80:af:0f: d6:4c:9f:ae:0f:01:e0:0e:38:4d:5d:71:da:0b:11:39:bd:c3: 5d:0c:db:14:ca:bf:7f:07:37:c9:36:bd:22:a5:73:c6:e1:13: 53:15:de:ac:4a:4b:dc:48:90:47:06:fa:d4:d2:5d:c6:d2:d4: 3f:0f:49:0f:27:de:21:b0:bd:a3:92:c3:cb:69:b6:8d:94:e1: e3:40:b4:80:c7:e6:e2:df:0a:94:52:d1:16:41:0f:bc:29:a8: 93:40:1b:77:28:a3:f2:cb:3c:7f:bb:ae:a6:0e:b3:01:78:09: d3:2b:cf:2f:47:83:91:36:37:43:34:6e:80:2b:81:10:27:95: 95:ae:1e:93:42:94:a6:23:b8:07:c0:0f:38:23:70:b0:8e:79: 14:cd:72:8a:90:bf:77:ad:74:3c:23:9e:67:5d:0e:26:15:6e: 20:95:6d:d0:89:be:a3:6c:4a:13:1d:39:fb:21:e3:9c:9f:f3: ff:15:da:0a:28:29:4e:f4:7f:5e:0f:70:84:80:7c:09:5a:1c: f4:ac:c9:1b:9d:38:43:dd:27:00:95:ef:14:a0:57:3e:26:0b: d8:bb:40:d6:1f:91:92:f0:4e:5d:93:1c:b7:3d:bd:83:ef:79: ee:47:ca:61:04:00:e6:39:05:ab:f0:cd:47:e9:25:c8:3a:4c: e5:62:9f:aa:8a:ba:ea:46:10:ef:bd:1e:24:5f:0c:89:8a:21: bb:9d:c7:73:0f:b9:b5:72:1f:1f:1b:5b:ff:3a:cb:d8:51:bc: bb:9a:40:91:a9:d5:fe:95:ac:73:a5:12:6a:b2:e3:b1:b2:7d: bf:e7:db:cd:9f:24:63:6e:27:cf:d8:82:d9:ac:d8:c9:88:ea: 4f:1c:ae:7d:b7:c7:81:b2:1c:f8:6b:6b:85:3b:f2:14:cb:c7: 61:81:ad:64:e7:d9:90:a3:ea:69:7e:26:7a:0a:29:7b:1b:2a: e0:38:f7:58:d1:90:82:44:01:ab:05:fd:68:0c:ab:9e:c6:94: 76:34:46:8b:66:bb:02:07
See public key certificate for more information.
Issuer: the issuer of a X.509 certificate. It is also known as Certificate Authority (CA) or Certification Authority. Issuer is typically represented in RFC 2253 format. Throughout this document,
issuer,issuer DN,CA, andtrusted issuerare used interchangeably.
Prerequisites¶
This feature requires Keystone API proxy SSL terminator to validate the incoming X.509 SSL client certificate and pass the certificate information (i.e. subject DN, issuer DN, etc) to the Keystone application as part of the request environment. At the time of this writing the feature has been tested with either HAProxy or Apache as Keystone API proxy SSL terminator only.
The rest of this document required readers to familiar with:
SSL with client authentication, or commonly known as two-way SSL
Configuring this feature requires OpenSSL Command Line Tool (CLI). Please refer to the respective OS installation guide on how to install it.
Keystone Configuration¶
This feature utilizes Keystone federation capability to determine the authorization associated with the incoming X.509 SSL client certificate by mapping the certificate attributes to a Keystone identity. Therefore, the direct issuer or trusted Certification Authority (CA) of the client certificate is the remote Identity Provider (IDP), and the hexadecimal output of the SHA256 hash of the issuer distinguished name (DN) is used as the IDP ID.
Note
Client certificate issuer DN may be formatted differently depending on the SSL terminator. For example, Apache mod_ssl may use RFC 2253 while HAProxy may use the old format. The old format is used by applications that linked with an older version of OpenSSL where the string representation of the distinguished name has not yet become a de facto standard. For more information on the old formation, please see the nameopt in the OpenSSL CLI manual. Therefore, it is critically important to keep the format consistent throughout the configuration as Keystone does exact string match when comparing certificate attributes.
How to obtain trusted issuer DN¶
If SSL terminates at either HAProxy or Apache, the client certificate issuer DN can be obtained by using the OpenSSL CLI.
Since version 2.3.11, Apache mod_ssl by default uses RFC 2253 when handling certificate distinguished names. However, deployer have the option to use the old format by configuring the LegacyDNStringFormat option.
HAProxy, on the other hand, only supports the old format.
To obtain issuer DN in RFC 2253 format:
$ openssl x509 -issuer -noout -in client_cert.pem -nameopt rfc2253 | sed 's/^\s*issuer=//'
To obtain issuer DN in old format:
$ openssl x509 -issuer -noout -in client_cert.pem -nameopt compat | sed 's/^\s*issuer=//'
How to calculate the IDP ID from trusted issuer DN¶
The hexadecimal output of the SHA256 hash of the trusted issuer DN is being used as the Identity Provider ID in Keystone. It can be obtained using OpenSSL CLI.
To calculate the IDP ID for issuer DN in RFC 2253 format:
$ openssl x509 -issuer -noout -in client_cert.pem -nameopt rfc2253 | tr -d '\n' | sed 's/^\s*issuer=//' | openssl dgst -sha256 -hex | awk '{print $2}'
To calculate the IDP ID for issuer DN in old format:
$ openssl x509 -issuer -noout -in client_cert.pem -nameopt compat | tr -d '\n' | sed 's/^\s*issuer=//' | openssl dgst -sha256 -hex | awk '{print $2}'
Keystone Configuration File Changes¶
The following options in the tokenless_auth section of the Keystone
configuration file keystone.conf are used to enable the X.509 tokenless
authorization feature:
trusted_issuer- A list of trusted issuers for the X.509 SSL client certificates. More specifically the list of trusted issuer DNs mentioned in the How to obtain trusted issuer DN section above. The format of the trusted issuer DNs must match exactly with what the SSL terminator passed into the request environment. For example, if SSL terminates in Apache mod_ssl, then the issuer DN should be in RFC 2253 format. Whereas if SSL terminates in HAProxy, then the issuer DN is expected to be in the old format. This is a multi-string list option. The absence of any trusted issuers means the X.509 tokenless authorization feature is effectively disabled.protocol- The protocol name for the X.509 tokenless authorization along with the option issuer_attribute below can look up its corresponding mapping. It defaults tox509.issuer_attribute- The issuer attribute that is served as an IdP ID for the X.509 tokenless authorization along with the protocol to look up its corresponding mapping. It is the environment variable in the WSGI environment that references to the Issuer of the client certificate. It defaults toSSL_CLIENT_I_DN.
This is a sample configuration for two trusted_issuer and a protocol set
to x509.
[tokenless_auth]
trusted_issuer = emailAddress=admin@foosigner.com,CN=Foo Signer,OU=eng,O=abc,L=San Jose,ST=California,C=US
trusted_issuer = emailAddress=admin@openstack.com,CN=OpenStack Cert Signer,OU=keystone,O=openstack,L=Sunnyvale,ST=California,C=US
protocol = x509
Setup Mapping¶
Like federation, X.509 tokenless authorization also utilizes the mapping
mechanism to formulate an identity. The identity provider must correspond
to the issuer of the X.509 SSL client certificate. The protocol for the
given identity is x509 by default, but can be configurable.
Create an Identity Provider (IDP)¶
As mentioned, the Identity Provider ID is the hexadecimal output of the SHA256 hash of the issuer distinguished name (DN).
Note
If there are multiple trusted issuers, there must be multiple IDP created, one for each trusted issuer.
To create an IDP for a given trusted issuer, follow the instructions in the How to calculate the IDP ID from trusted issuer DN section to calculate the IDP ID. Then use OpenStack CLI to create the IDP. i.e.
$ openstack identity provider create --description 'IDP foo' <IDP ID>
Create a Map¶
A mapping needs to be created to map the Subject DN in the client
certificate as a user to yield a valid local user if the user’s type
defined as local in the mapping. For example, the client certificate
has Subject DN as CN=alex,OU=eng,O=nice-network,L=Sunnyvale,
ST=California,C=US, in the following examples, user_name will be
mapped to``alex`` and domain_name will be mapped to nice-network.
And it has user’s type set to local. If user’s type is not
defined, it defaults to ephemeral.
Please refer to mod_ssl for the detailed mapping attributes.
[
{
"local": [
{
"user": {
"name": "{0}",
"domain": {
"name": "{1}"
},
"type": "local"
}
}
],
"remote": [
{
"type": "SSL_CLIENT_S_DN_CN",
"whitelist": ["glance", "nova", "swift", "neutron"]
},
{
"type": "SSL_CLIENT_S_DN_O",
"whitelist": ["Default"]
}
]
}
]
When user’s type is not defined or set to ephemeral, the mapped user
does not have to be a valid local user but the mapping must yield at least
one valid local group. For example:
[
{
"local": [
{
"user": {
"name": "{0}",
"type": "ephemeral"
},
"group": {
"domain": {
"name": "{1}"
},
"name": "openstack_services"
}
}
],
"remote": [
{
"type": "SSL_CLIENT_S_DN_CN",
"whitelist": ["glance", "nova", "swift", "neutron"]
},
{
"type": "SSL_CLIENT_S_DN_O",
"whitelist": ["Default"]
}
]
}
]
Note
The above mapping assume openstack_services group already exist and have the proper role assignments (i.e. allow token validation) If not, it will need to be created.
To create a mapping using OpenStack CLI, assuming the mapping is saved into
a file x509_tokenless_mapping.json:
$ openstack mapping create --rules x509_tokenless_mapping.json x509_tokenless
Note
The mapping ID is arbitrary and it can be any string as opposed to IDP ID.
Create a Protocol¶
The name of the protocol must be the same as the one specified by the
protocol option in tokenless_auth section of the Keystone
configuration file. The protocol name is user designed and it can be any
name as opposed to IDP ID.
A protocol name and an IDP ID will uniquely identify a mapping.
To create a protocol using OpenStack CLI:
$ openstack federation protocol create --identity-provider <IDP ID>
--mapping x509_tokenless x509
Note
If there are multiple trusted issuers, there must be multiple protocol created, one for each IDP. All IDP can share a same mapping but the combination of IDP ID and protocol must be unique.
SSL Terminator Configuration¶
Apache Configuration¶
If SSL terminates at Apache mod_ssl, Apache must be configured to handle two-way SSL and pass the SSL certificate information to the Keystone application as part of the request environment.
The Client authentication attribute SSLVerifyClient should be set
as optional to allow other token authentication methods and
attribute SSLOptions needs to set as +StdEnvVars to allow certificate
attributes to be passed. For example,
<VirtualHost *:443>
WSGIScriptAlias / /var/www/cgi-bin/keystone/main
ErrorLog /var/log/apache2/keystone.log
CustomLog /var/log/apache2/access.log combined
SSLEngine on
SSLCertificateFile /etc/apache2/ssl/apache.cer
SSLCertificateKeyFile /etc/apache2/ssl/apache.key
SSLCACertificatePath /etc/apache2/capath
SSLOptions +StdEnvVars
SSLVerifyClient optional
</VirtualHost>
HAProxy and Apache Configuration¶
If SSL terminates at HAProxy and Apache is the API proxy for the Keystone application, HAProxy must configured to handle two-way SSL and convey the SSL certificate information via the request headers. Apache in turn will need to bring those request headers into the request environment.
Here’s an example on how to configure HAProxy to handle two-way SSL and pass the SSL certificate information via the request headers.
frontend http-frontend
mode http
option forwardfor
bind 10.1.1.1:5000 ssl crt /etc/keystone/ssl/keystone.pem ca-file /etc/keystone/ssl/ca.pem verify optional
reqadd X-Forwarded-Proto:\ https if { ssl_fc }
http-request set-header X-SSL %[ssl_fc]
http-request set-header X-SSL-Client-Verify %[ssl_c_verify]
http-request set-header X-SSL-Client-SHA1 %{+Q}[ssl_c_sha1]
http-request set-header X-SSL-Client-DN %{+Q}[ssl_c_s_dn]
http-request set-header X-SSL-Client-CN %{+Q}[ssl_c_s_dn(cn)]
http-request set-header X-SSL-Client-O %{+Q}[ssl_c_s_dn(o)]
http-request set-header X-SSL-Issuer %{+Q}[ssl_c_i_dn]
http-request set-header X-SSL-Issuer-CN %{+Q}[ssl_c_i_dn(cn)]
When the request gets to the Apache Keystone API Proxy, Apache will need to bring those SSL headers into the request environment. Here’s an example on how to configure Apache to achieve that.
<VirtualHost 192.168.0.10:5000>
WSGIScriptAlias / /var/www/cgi-bin/keystone/main
# Bring the needed SSL certificate attributes from HAProxy into the
# request environment
SetEnvIf X-SSL-Issuer "^(.*)$" SSL_CLIENT_I_DN=$0
SetEnvIf X-SSL-Issuer-CN "^(.*)$" SSL_CLIENT_I_DN_CN=$0
SetEnvIf X-SSL-Client-CN "^(.*)$" SSL_CLIENT_S_DN_CN=$0
SetEnvIf X-SSL-Client-O "^(.*)$" SSL_CLIENT_S_DN_O=$0
</VirtualHost>
Setup auth_token middleware¶
In order to use auth_token middleware as the service client for X.509
tokenless authorization, both configurable options and scope information
will need to be setup.
Configurable Options¶
The following configurable options in auth_token middleware
should set to the correct values:
auth_type- Must set tov3tokenlessauth.certfile- Set to the full path of the certificate file.keyfile- Set to the full path of the private key file.cafile- Set to the full path of the trusted CA certificate file.project_nameorproject_id- set to the scoped project.project_domain_nameorproject_domain_id- ifproject_nameis specified.
Here’s an example of auth_token middleware configuration using X.509
tokenless authorization for user token validation.
[keystone_authtoken]
memcached_servers = localhost:11211
cafile = /etc/keystone/ca.pem
project_domain_name = Default
project_name = service
auth_url = https://192.168.0.10/identity/v3
auth_type = v3tokenlessauth
certfile = /etc/glance/certs/glance.pem
keyfile = /etc/glance/private/glance_private_key.pem
