1# VMI Certificate Exchange 2 3Author: 4 Raviteja Bailapudi 5 6Other contributors: 7 Ratan Gupta 8 9Created: 10 07/10/2019 11 12## Glossary 13- HMC - Hardware Management Console : Management console for IBM enterprise 14 servers. 15- PHYP - Power Hypervisor : This orchestrates and manages system 16 virtualization. 17- VMI - Virtual Management Interface : The interface facilitating 18 communications between HMC and PHYP embedded linux virtual machine. 19- KVM - Kernel Virtual Machine : Open source virtualization software 20 21## Problem Description 22On enterprise POWER systems, the Hardware management console (HMC) needs to 23establish a secure connection to the Virtualization management interface (VMI) 24for virtualization management. 25 26VMI is an embedded Linux VM created and run on PHYP which provides the 27virtualization function. 28 29HMC requires client key, client.crt, and CA.crt to establish 30secure connection to VMI. 31 32BMC needs to provide certificate exchange functionality to management 33console due to following reasons: 34- Host firmware (PHYP) does not have authentication mechanism. 35- VMI trusts that BMC has authenticated and verified the authenticity of 36 any client connected as there is a secure authenticated connection already 37 exists between HMC and BMC. 38 39Management console needs an API through which it can send the CSR to VMI (CA) 40and gets the signed certificate and the CA certificate from VMI. 41This design will describe how certificates get exchanged between management 42console and VMI 43 44IBM systems can run both IBM specific host-firmware (PHYP) and Linux KVM. 45This API would be used only for the PHYP based machines. 46 47Enable and disable of this API would be controlled by the build time 48configurable variable. 49 50## Background and References 51- VMI will be created and run on PHYP that will provide the virtualization 52 function. 53- When the VMI is powered on it generates a public-private key pair and 54 a self-signed root certificate is created using this key pair. 55- VMI acts as root CA only for VMI endpoints, its not an official CA and uses 56 its self-signed certificate to sign CSR from client. 57- HMC needs to establish secure connection to VMI to perform virtualization 58 management. 59 60## Requirements 61BMC will provide an interface for management console to exchange certificate 62information from VMI so that HMC can establish secure connection to VMI. 63 64## Proposed Design 65The management console can send CSR string to VMI (CA) and get signed certificate 66and Root CA certificate via proposed BMC interface. 67 68In this interface perspective, the HTTP error code could be 4XX/5XX. 69It would be mapped depending on the PLDM error response. 70 71HMC can query BMC state and use this API to initiate certificate 72exchange.If HMC runs this command before PHYP boots, PLDM command returns error 73If PLDM command throws an error, that would be mapped to Internal server Error (500). 74 75### Design Flow 76```ascii 77 +------------+ +--------+ +--------+ 78 | HMC | | BMC | | VMI | 79 | (client) | | | | (CA) | 80 +-----+------+ +----+---+ +---+----+ 81 | | | 82 | | | 83 +------------------->+ | 84 | VMI Network info | | 85 +<-------------------+ | 86 | | | 87client.key| | | 88client.csr SignCSR() | pldm call to host | 89 +------------------->+------------------->| 90 | | | Sign CSR 91 | SignCSR() response | pldm response from host 92 +<-------------------+<-------------------| 93 | | | 94 Client.crt | | 95 CA.crt | | 96 | | | 97 | | | 98 | | | 99 | | | 100 + + + 101 102``` 103### VMI certificate exchange 104Management console should use the below REST commands to exchange certificates 105with VMI 106 107#### Get Signed certificate: 108REST command to get signed client certificate from VMI 109 110Request: 111```bash 112curl -k -H "X-Auth-Token: <token>" -X POST "Content-Type: application/json" -d 113 '{"CsrString":"<CSR string>"}' https://{BMC_IP}/ibm/v1/Host/Actions/SignCSR 114``` 115 116Response: 117This will return the certificate string which contains signed client 118certificate 119 120``` 121 { 122 “Certificate”: "<certificate string>" 123 } 124 125``` 126#### Get Root certificate: 127REST command to get VMI root certificate 128 129Request: 130```bash 131curl -k -H "X-Auth-Token: <token>" -X GET http://{BMC_IP}/ibm/v1/Host/Certificate/root 132``` 133 134Response: 135This will return the certificate string which contains and root CA certificate. 136 137``` 138 { 139 “Certificate”: "<certificate string>" 140 } 141 142``` 143This interface returns HTTP error codes 5XX/4XX in failure cases 144 145## Alternatives considered: 146 147Have gone through existing BMC certificate management infrastructure if we can 148extend for this use case. 149 150### Current flow for generating and installing Certificates (CSR Based): 151 152* Certificate Signing Request CSR is a message sent from an applicant to a 153 certificate authority in order to apply for a digital identity certificate. 154* The user calls CSR interface BMC creates new private key and CSR Certificate 155 File 156* CSR certificate is passed onto the CA to sign the certificate and then upload 157 CSR signed certificate and install the certificate. 158 159### Note 160 161* Our existing BMC certificate manager/service have interfaces to generate CSR, 162 upload certificates and other interfaces to manage certificates(replace,delete..etc). 163* In VMI certificate exchange, requirement for BMC is to provide an interface for 164 management console to get CSR certificate signed by VMI (CA). 165* We don’t have any existing certificate manager interface to forward CSR 166 request to CA to get signed by CA. 167* Here proposal is to have SignCSR() interface which accepts CSR string and 168 return signed certificate and Root CA certificate. 169* This requirement is out of scope for existing certificate manager so proposing 170 SignCSR interface as management console specific interface. 171 172### Alternate Design 173```ascii 174 +------------+ +--------+ +--------+ 175 | HMC | | BMC | | VMI | 176 | (client) | | | | PHYP | 177 +-----+------+ +----+---+ +---+----+ 178 | | | 179 | | | 180 +------------------->+ | 181 | VMI Network info | | 182 +<-------------------+ | 183 | | 184 | SSL tunnel | 185 +---------------------------------------->| 186 | Verify Password |Nets 187 +---------------------------------------->| 188 | | 189 | pldm |pldm call to authenticate 190 +<-------------------+<-------------------| 191 | | | 192 | pam | 193 | authentication | 194 | +------------------->| 195 | | 196 | session established | 197 |<--------------------------------------->| 198 199``` 200* In this alternate design, Management console establishes connection to VMI and 201 sends Verify Password command to authenticate user to establish secure session. 202* VMI does not have authentication method, so VMI needs to use BMC authentication method 203 over PLDM. 204* There are security concerns if raw password is getting sent over PLDM in clear text 205 over LPC, so this design ruled out. 206 207## Impacts 208- Create new interface GetRootCertificate in webserver which reads root certificate from 209 '/var/lib/bmcweb/RootCert' file.This API can handle muptiple requests at the sametime. 210- PLDM gets root certificate as soon as VMI boots and it writes to 211 '/var/lib/bmcweb/RootCert'. 212- Implement D-Bus interface to create dbus object for each signCSR so that multiple requests 213 can work at the sametime. 214 D-bus service: xyz.openbmc_project.Certs.ca.authority.Manager 215 Object path : /xyz/openbmc_project/certs/ca 216 Interface : xyz.openbmc_project.Certs.Authority 217 Method : SignCSR 218- Dbus object contains CSR,ClientCertificate and Status properties. 219- PLDM looks for interface added signal for each object created and reads CSR property for 220 CSR string and forwards this CSR string to VMI for signing this CSR. 221- Once PLDM on BMC gets the client certificate from VMI, it updates the ClientCertificate 222 D-bus property and updates the Status property to Complete in the Dbus object. 223- Create new interface SignCSR in webserver which takes CSR string as input and returns 224 certificate string.This interface calls SignCSR dbus method and looks for Status 225 property changed signal to verify status.Reads ClientCertificate property content and 226 return certificate string. 227- On completion of serving the sign CSR request, respective dbus object will be deleted 228 before returning certificate string to client. 229- BMC is passthrough which allows certificate exchange between VMI and HMC. 230 BMC does not store or parse these certificates. 231- Build time configure variable defined to control enable and disable of this API 232 in webserver. It is required only for IBM systems with IBM specific host-firmware (PHYP) 233 234## Testing 235- Test the interface command from a management console and verify if certificate 236 exchange worked as expected and verify if management console able to establish 237 secure connection to VMI. 238 239- Certificate exchange fails in the following scenarios 240 * If PHYP is not up 241 * If PHYP throws error for certificate validation. 242 This interface returns appropriate HTTP error code (4XX/5XX) based on type of error. 243 244- If there are issues like certificate expiry, revocation, incorrect date/time and 245 incorrect certificates, then HMC fails to establish connection to VMI. 246