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BMC Certificate management

Certificate management allows to replace the existing certificate and private key file with another (possibly certification Authority (CA) signed) certificate and private key file. Certificate management allows the user to install both the server and client certificates. The REST interface allows to update the certificate, using an unencrypted certificate and private key file in .pem format, which includes both private key and signed certificate.

Signed Certificate upload Design flow(Pre-generated):

  • The REST Server copies the certificate and private key file to a temporary location.
  • REST server should map the URI to the target DBus application (Certs) object. The recommendation for the D-Bus application implementing certificate D-Bus objects is to use the same path structure as the REST endpoint. e.g.:
    • The URI /xyz/openbmc_project/certs/server/https maps to instance of the certificate application handling Https server certificate.
    • The URI /xyz/openbmc_project/certs/client/ldap maps to instance of the certificate application handling LDAP client certificate.
    • The URI /xyz/openbmc_project/certs/authority/ldap maps to instance of the certificate application handling Certificate Autohority certificates.
  • REST server should call the install method of the certificate application instance.
  • Certificate manager application also implements d-bus object xyz.openbmc_project.Certs.Manager. This includes the collection of "certificates specific d-bus objects" installed in the system. This d-bus provide option to view the certificate on PEM format and delete the same. Refer https://en.wikipedia.org/wiki/Privacy-Enhanced_Mail for details.
  • Applications should subscribe the xyz.openbmc_project.Certs.Manager to see any new certificate is uploaded or change in the existing certificates.
  • Certificate manager scope is limited to manage the certificate and impacted application is responsible for application specific changes.
  • In case of delete action, certificate manager creates a new self signed certificate after successful delete (regards only server type certificates)

REST interface details:

url: /xyz/openbmc_project/certs/server/https
Description: Update https server signed certificate and the private key.
Method: PUT

url: /xyz/openbmc_project/certs/server/https/<cert_id>
Description: Delete https server signed certificate and the private key.
Method: DELETE

url: /xyz/openbmc_project/certs/client/ldap
Description: Update ldap client certificate and the private key.
Method: PUT

url: /xyz/openbmc_project/certs/client/ldap/<cert_id>
Description: Delete ldap client certificate and the private key.
Method: DELETE

Return codes

    200  Success
    400  Invalid certificate and private key file.
    405  Method not supported.
    500  Internal server error

CSR

User flow for generating and installing Certificates(CSR Based):

Certificate Signing Request CSR is a message sent from an applicant to a certitificate authority in order to apply for a digital identity certificate. This section provides the details of the CSR based certificate user flow.

  • The user performs the CSR/create interface BMC creates new private key and CSR object which includes CSR information.
  • The user performs the CSR/export interface Allows the user to export the CSR file which is part of newly created CSR object. This can be provided to the CA to create SSL certificate.
  • The user perform the certificate upload on appropriate services. Example: if trying to replace the HTTPS certificate for a Manager, navigate to the Manager’s Certificate object upload interface. The Upload method internally pairs the private key used in the first step with the installed certificate.

Assumptions:

  • BMC updates the private key associated to CSR for any new CSR request.
  • BMC upload process automatically appends certificate file with system CSR private key, for the service which requirs certificate and key.
  • CSR based Certificate validation is alway's based on private key in the system.

CSR Request

  • CSR requests initiated through D-Bus are time-consuming and might result D-Bus time-out error.
  • To overcome the time-out error, parent process is forked and CSR operation is performed in the child process so that parent process can return the calling thread immediately.
  • OpenSSL library is used in generating CSR based on the algorithm type.
  • At present supporting generating CSR for only "RSA" algorithm type.
  • Parent process registers child process PID and a callback method in the sd_event_lopp so that callback method is invoked upon completion the CSR request in the child process.
  • Callback method invoked creates a CSR object with the status of the CSR operation returned from the child process.
  • CSR read operation will return the CSR string if status is SUCCESS else throws InternalFailure exception to the caller.
  • Certificate Manager implements "/xyz/openbmc_project/Certs/CSR/Create" interface.
  • CSR object created implements "/xyz/openbmc_project/Certs/CSR" interface.
  • Caller needs to validate the CSR request parameters.
  • Caller need to wait on "InterfacesAdded" signal generated upon creation of the CSR object to start reading CSR string.

Example usage for the GenerateCSR POST request

url: /redfish/v1/CertificateService
Action: #CertificateService.GenerateCSR {
 "City": "HYB",
 "CertificateCollection": "/redfish/v1/Managers/bmc/NetworkProtocol/HTTPS/Certificates/",
 "CommonName": "www.company.com",
 "ContactPerson":"myname",
 "AlternativeNames":["mycompany.com","mycompany2.com"],
 "ChallengePassword":"abc123",
 "Email":"[email protected]",
 "GivenName":"localhost",
 "Initials":"G",
 "Country": "IN",
 "KeyCurveId":"0",
 "KeyUsage":["ServerAuthentication","ServerAuthentication"],
 "KeyBitLength": 2048,
 "KeyPairAlgorithm": "RSA",
 "Organization": "ABCD",
 "OrganizationUnit": "XY",
 "State": "TX",
 "SurName": "XX",
 "UnstructuredName": "xxx"
}
Description: This is used to perform a certificate signing request.
Method: POST

Additional interfaces:

  • CertificateService.ReplaceCertificate Allows the user to replace an existing certificate.

d-bus interfaces:

d-bus interface to install certificate and private Key

  • Certs application must:
    • validate the certificate and Private key file by checking, if the Private key matches the public key in the certificate file.
    • copy the certificate and Public Key file to the service specific path based on a configuration file.
    • Reload the listed service(s) for which the certificate is updated.

d-bus interface to Delete certificate and Private Key

  • certificate manager should provide interface to delete the existing certificate.
  • Incase of server type certificate deleting a signed certificate will create a new self signed certificate and will install the same.

Boot process

  • certificate management instances should be created based on the system configuration.

  • Incase of no Https certificate or invalid Https certificate, certificate manager should update the https certificate with self signed certificate.

Repository:

phosphor-certificate-manager

Redfish Certificate Support

Certificate Upload

  • Certificate Manager implements "xyz.openbmc_project.Certs.Install" interface for installing certificates in the system.

  • Redfish initiates certificate upload by issuing a POST request on the Redfish CertificateCollection with the certificate file. Acceptable body formats are: raw pem text or json that is acceptable by action CertificateService.ReplaceCertificate

    For example the HTTPS certificate upload POST request is issued on URI "/redfish/v1/Managers/bmc/NetworkProtocol/HTTPS/Certificates"

  • Bmcweb receives the POST request and it maps the Redfish URI to the corresponding Certificate Manager D-Bus URI. e.g: HTTPS certificate collection URI /redfish/v1/Managers/bmc/NetworkProtocol/HTTPS/Certificates mapped to /xyz/openbmc_project/certs/server/https.

  • Bmcweb initiates an asynchronous call which invokes the "Install" method of the Certificate Manager.

  • Certificate Manager "Install" method validates, installs the certificate file and creates a Certificate object.

  • Certificate Manager initiates Reload of the Bmcweb service to trigger configuration reload.

  • BMCweb service raises SIGHUP signal as part of Reload.

  • Bmcweb application handles the SIGHUP signal and reloads the SSL context with the installed certificate.

  • Bmcweb invokes the Callback method with the status of the "Install" method received from the Certificate Manager.

  • Callback method set the response message with error details for failure, sets the response message with newly created certificate details for success.

  • Certificate object D-Bus path mapped to corresponding Redfish certificate URI. e.g: /xyz/openbmc_project/certs/server/https/1 is mapped to /redfish/v1/Managers/bmc/NetworkProtocol/HTTPS/Certificates/1 ID of the certificate is appended to the collection URI.

Certificate Replace

  • Certificate Object implements "xyz.openbmc_project.Certs.Replace" interface to for replacing existing certificate.
  • Redfish issues Replace certificate request by invoking the ReplaceCertificate action of the CertificateService.
  • Redfish Certificate Collection URI is mapped to corresponding Certificate D-Bus object URI e.g: HTTPS certificate object 1 URI /redfish/v1/Managers/bmc/NetworkProtocol/HTTPS/Certificates/1 is mapped to /xyz/openbmc_project/certs/server/https/1.
  • Bmcweb receives POST request for Replace Certificate, invokes the Replace D-Bus method of the Certificate object asynchronously.
  • Callback method will be passed to the bmcweb asynchronous method which will called after completion of the D-Bus Replace method.
  • Callback method checks the response received, if failure response message is set with error details, if success response message is set with the replaced certificate details.

Bootup

  • During bootup certificate objects created for the existing certificates.

Errors thrown by Certificate Manager

  • NotAllowed exception thrown if Install method invoked with a certificate already existing. At present only one certificate per server and client certificate type is allowed.
  • InvalidCertificate excption thrown for validation errors.

Certificate Deletion

  • For server and client certificate type the certificate deletion is not allowed. In case of authority certificate type the delete option is acceptable and can be done on individial certificates, for example:

    url: redfish/v1/Managers/bmc/Truststore/Certificates/1
Method: DELETE

Returns: code 204 with empty body content.