DSR-RFC-01 Device Registration

Device registration is performed by the user after previous authentication.

1. High Level Flow

1. At first start, the TrustClient generates the app/device identity key material and a corresponding Certificate Signing Request.
2. The TrustClient then triggers the attestation of the key material, device and app with the help of the Platform Attestation Service and receives attestation results.
3. To register the device for themself, the user signs a Device Registration Token, containing the app/device identity and attestation results and the Certificate Signing Request with their electronic health card (EF.C.CH.AUT.E256). Then the TrustClient sends the Device Registration Token to the Device Management Service (GMS).
4. With the help of the Platform Attestation Service, the Device Management Service (GMS) verifies the received attestations and key material.
5. The Device Management Service (GMS) sends the Certificate Signing Request to the GMS CA which then issues a Trust Client Certificate
6. Finally, the Device Management Service (GMS) stores the app/device identity key material with the corresponding user identity in its database.
7. The Device Management Service (GMS) sents the Trust Client Certificate to the TrustClient.

2. Flow Details

@startuml DSR-RFC-01 Main Flow
autonumber "<b>[00]"
skinparam defaultFontSize 10
skinparam defaultFontName Helvetica
skinparam DefaultMonospacedFontName Courier
skinparam lengthAdjust none

participant TrustClient

participant Smartcard

participant GMS

activate TrustClient

TrustClient -> GMS ++: get ""nonce""
note right
Regular TLS
Server auth only
end note

GMS -> GMS: generate ""nonce""\n store ""nonce""
GMS -> TrustClient: return ""nonce""

TrustClient -> TrustClient: derive nonces\n\t""nonce_keypair_mTLS = SHA256(nonce | 'KEYPAIR_MTLS')""\n\t""nonce_CSR_mTLS = SHA256(nonce | 'CSR_MTLS')""\n\t""nonce_Integrity = SHA256(nonce | 'INTEGRITY')""\n\t""nonce_smartcard = SHA256(nonce | 'SMARTCARD')""\n\t""nonce_attest = SHA256(nonce | 'ATTEST')""

alt#FEFFD5  2.1.1 Create Android Device Registration
TrustClient -> TrustClient: generate key pair and\ncreate ""JWT_registration""
else 2.2.1 Create Apple Device Registration 
TrustClient -> TrustClient: generate key pair and\ncreate ""JWT_registration""
end

TrustClient -> Smartcard ++:  sign ""(JWT_registration, nonce_smartcard)""\n\twith ""PrK.CH.AUT.E256""/""EF.C.CH.AUT.E256""
return return JWS_registration_signed


TrustClient -> GMS: register device JWS(JWS_registration_signed)

GMS -> GMS: verify JWS_registration_signed
GMS -> GMS: check EF.C.CH.AUT.E256 validity
note left
gematik PKI OCSP
end note

alt#FEFFD5 2.1.2 Verify Android Device Registration 
GMS -> GMS: verify ""JWS_registration_signed""\nextract Android specifics
else 2.2.2 Verify Apple Device Registration
GMS -> GMS: verify ""JWS_registration_signed""\nextract Apple specifics
end


GMS -> GMS: extract KVNR from EF.C.CH.AUT.E256\nin JWS_registration_signed
GMS -> GMS: create cert_mTLS(CSR, UUID_device, nonce)

alt#FEFFD5 Store Android Device Registration
GMS -> GMS: store\n\tKVNR\n\tUUID_device\n\tcert_mTLS\n\tcert_attest
else Store Apple Device Registration
GMS -> GMS: store\n\tKVNR\n\tUUID_device\n\tcert_mTLS\n\tattestation_statement
end 
return return cert_mTLS
TrustClient -> TrustClient: store cert_mTLS

@enduml

2.1 Android specifics

2.1.1 Create Android Device Registration

@startuml
autonumber "<b>['2.1.1' 00]"
skinparam defaultFontSize 10
skinparam DefaultMonospacedFontName Courier
skinparam lengthAdjust none

activate TrustClient
participant PlayIntegrityAPI


group Android
TrustClient -> TrustClient: generate\n\t""keypair_attest""\n\t""attestCertChain(nonce_attest)""\n\t""keypair_mTLS""\n\t""keypair_mTLS_cert(nonce_keypair_mTLS)""\n\t""CSR(nonce_CSR_mTLS, keypair_mTLS)""
TrustClient -> PlayIntegrityAPI ++: perform IntegrityTokenRequest(nonce_Integrity)
return return integrityVerdict

TrustClient -> TrustClient: create\n\t""JWT_registration(""\n\t\t""TYPE_ANDROID,""\n\t\t""nonce,""\n\t\t""pubkey_mTLS,""\n\t\t""keypair_mTLS_cert,""\n\t\t""pubkey_attest,""\n\t\t""attestCertChain""\n\t\t""integrityVerdict,""\n\t\t""CSR""\n\t"")""

end

@enduml

2.1.2 Verify Android Device Registration

@startuml
autonumber "<b>['2.1.1' 00]"
skinparam defaultFontSize 10
skinparam DefaultMonospacedFontName Courier
skinparam lengthAdjust none

activate GMS
participant GoogleServer


group Android
GMS -> GMS: extract nonce, pubkey_mTLS, AttestCert_mTLS,\nintegrityVerdict, CSR from JWS_registration_signed
GMS -> GMS: verify attestCertChain and certification extension data
GMS -> GMS: verify AttestCert_mTLS and certification extension data
GMS -> GMS: verify AttestCert_mTLS was signed by pubkey_attest
GMS -> GoogleServer ++: get Key Attestation certificate revocation status list

return return CRL_json
GMS -> GMS: evaluate CRL_json
GMS -> GoogleServer ++: request integrity_verdict(integrityVerdict)
return return verdict_json
GMS -> GMS: evaluate verdict_json

end

@enduml

2.2 Apple specifics

2.2.1 Create Apple Device Registration

@startuml
autonumber "<b>['2.2.1' 00]"
skinparam defaultFontSize 10
skinparam DefaultMonospacedFontName Courier
skinparam lengthAdjust none

activate TrustClient
participant AppAttestAPI

group Apple
TrustClient -> TrustClient: generate\n\t""keypair_mTLS""\n\t""CSR(nonce_CSR_mTLS, keypair_mTLS)""
TrustClient -> AppAttestAPI ++: generate\n\t""keypair_attest(""\n\t\t""SHA256(nonce_Integrity | SHA256(pubkey_mTLS))""\n\t"")""
AppAttestAPI -> AppAttestAPI: attest

return return attestation_statement

TrustClient -> TrustClient: create\n\t""JWT_registration(""\n\t\t""TYPE_IOS,"",\n\t\t""nonce,""\n\t\t""pubkey_mTLS,""\n\t\t""attestation_statement,""\n\t\t""keyIdentifier_attest,""\n\t\t""CSR""\n\t"")""

end

@enduml

2.2.2 Verify Apple Device Registration

@startuml
autonumber "<b>['2.2.2' 00]"
skinparam defaultFontSize 10
skinparam DefaultMonospacedFontName Courier
skinparam lengthAdjust none

activate GMS


group Apple
GMS -> GMS: extract nonce, pubkey_mTLS, attestation_statement,\nkeyIdentifier_attest, CSR
GMS -> GMS: verify attestation_statement
end

@enduml