The private_key_jwt authentication is based on asymmetric key, the private part is generated and only known by the client whereas the public part is communicated and registered in the authorization server for the specific client.
openssl command can be used to generate ES256 asymmetric keys as required by the FAPI part 2 specification. Office will keep the private key and share the public key for registration with WIPO. Below is an example of script to generate ES256 asymmetric keys.
#!/bin/bash
# Set the environment
PRIVATE_KEY_ES256=es256_private.pem
PUBLIC_KEY_ES256=es256_public.pem
CLIENT_NAME=DAS
# Generates the ES256 keys
openssl ecparam -genkey -name prime256v1 -noout -out "${PRIVATE_KEY_ES256}"
# Extracts the public key
openssl ec -in "${PRIVATE_KEY_ES256}" -pubout -out "${PUBLIC_KEY_ES256}"
# Generates an x509 certificate
CERT_KEY_ES256=es256_cert.pem
OPENSSL_CONF=./openssl.cnf
CERT_CN="${CLIENT_NAME} private_key_jwt authentication"
# Build the certificate config file
printf '[ req ]\n' > "${OPENSSL_CONF}"
printf 'prompt = no\n' >> "${OPENSSL_CONF}"
printf 'distinguished_name = req_distinguished_name\n' >> "${OPENSSL_CONF}"
printf '[ req_distinguished_name ]\n' >> "${OPENSSL_CONF}"
printf 'CN = %s\n' "${CERT_CN}" >> "${OPENSSL_CONF}"
# Creates the x509 certificate
openssl req -x509 -new -config "${OPENSSL_CONF}" -key "${PRIVATE_KEY_ES256}" -out "${CERT_KEY_ES256}" |
The following files are examples:
Files | Description |
|---|---|
| es256_cert.pem | Certificate file that will be communicated to WIPO for the configuration of the private_key_jwt client authentication |
| es256_private.pem | Must never be communicated and kept secret, used by the client to sign the private_key_jwt authentication request |
| es256_public.pem | Used only at the generation step, kept for record |
| openssl.cnf | Used only at the generation step, kept for record |
The authentication flow of private_key_jwt is depicted in the diagram below
The private_key_jwt authentication consists of creating a JSON structure containing the following login attributes:
Attribute | Example | Description |
|---|---|---|
| iss | das-api-auth | Issuer: Client id |
| sub | das-api-auth | Subject: Client id |
| aud | https://logindev.wipo.int:443/am/oauth2/access_token | Audience: Token endpoint of the authorization server |
| exp | 1622450728 | Expiration time: The expiration time of the data, current time + small amount of seconds (current epoch + 10s is ok) |
ES256 signing algorithm + above attributes + signature of them must be served in JWT format (rfc7519), see below:
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All parts are encoded and separated by '.' to make up the JWT as follows
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The JWT client assertion can now be submitted to authorization server for authentication with the token endpoint (i.e. POST https://logindev.wipo.int:443/am/oauth2/access_token in the attached specification) including the following parameters for client_credentials:
POST parameter | example | Description |
|---|---|---|
| grant_type | client_credentials | OAuth2 client_credentials authentication flow is used for machine to machine communication |
| scope | das-api/das-access | Scopes (=roles), if any, separated by spaces which are required to use the DAS API |
| client_assertion_type | urn:ietf:params:oauth:client-assertion-type:jwt-bearer | The client_assertion_type indicates to the authorization server the method used to authenticate, private_key_jwt requires jwt-bearer |
| client_assertion | eyJhbGciOiJFUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJkYXMtYXBpLWF1dG giLCJzdWIiOiJkYXMtYXBpLWF1dGgiLCJhdWQiOiJodHRwczovL2xvZ2luZG V2LndpcG8uaW50OjQ0My9hbS9vYXV0aDIvYWNjZXNzX3Rva2VuIiwiZXh wIjoxNjIyNDUwNzI4fQ.BLA6k2kKKFVm6AG-DPDpRU_5JDFGRF1dHjKul7saWCv5OxXGg4EY-J9e1p8Dg0ngD2dZ2grkJ2su7jaHy67YEw | The JWT generated in the paragraph above |
| The above token endpoint is part of third party product that supports OpenID Connect (OIDC) authentication protocol based on the OAuth 2.0 family of specifications |
Below is an example of authentication script.
#!/bin/bash
PRIVATE_KEY_ES256=es256_private.pem
CLIENT_ID=das-api-auth
SCOPE="das-api/das-access"
ISSUER="https://logindev.wipo.int/am/oauth2"
# https://logindev.wipo.int/am/oauth2/.well-known/openid-configuration
OIDC_CONFIG_JSON=$(curl -k "${ISSUER}/.well-known/openid-configuration")
# Generic way to obtain the token endpoint
TOKEN_ENDPOINT=$(printf '%s' ${OIDC_CONFIG_JSON} | jq -r ".token_endpoint")
UTC_TIME=$(date -u +%s)
EXP_TIME=$(expr "$UTC_TIME" + 10)
JSON='{'
JSON=${JSON}$(printf '"iss":"%s"' ${CLIENT_ID})
JSON=${JSON}$(printf ',"sub":"%s"' ${CLIENT_ID})
JSON=${JSON}$(printf ',"aud":"%s"' ${TOKEN_ENDPOINT})
JSON=${JSON}$(printf ',"exp":%s' ${EXP_TIME})
JSON=${JSON}'}'
JSON_HEADER_B64=$(printf '{"alg":"ES256","typ":"JWT"}' | jq -cj | base64 -w0 | tr -d '\n=' | tr '+/' '-_')
JSON_PAYLOAD_B64=$(printf $JSON | jq -cj | base64 -w0 | tr -d '\n=' | tr '+/' '-_')
JSON_SIGNATURE_ASN1_B64=$(printf '%s.%s' $JSON_HEADER_B64 $JSON_PAYLOAD_B64 | openssl dgst -sha256 -sign "${PRIVATE_KEY_ES256}" | openssl asn1parse -inform DER | base64 -w0)
JSON_SIGNATURE_HEX=$(printf $JSON_SIGNATURE_ASN1_B64 | base64 -d | sed -n '/INTEGER/p' | sed 's/.*INTEGER\s*://g' | sed -z 's/[^0-9A-F]//g')
JSON_SIGNATURE_B64=$(printf $JSON_SIGNATURE_HEX | xxd -p -r | base64 -w0 | tr -d '\n=' | tr '+/' '-_')
JWT_ASSERTION=$(printf '%s.%s.%s' $JSON_HEADER_B64 $JSON_PAYLOAD_B64 $JSON_SIGNATURE_B64)
# echo $JWT_ASSERTION
# Access token private_key_jwt
curl --insecure \
--header "Content-Type: application/x-www-form-urlencoded" \
--data-urlencode "grant_type=client_credentials" \
--data-urlencode scope="${SCOPE}" \
--data-urlencode "client_assertion_type=urn:ietf:params:oauth:client-assertion-type:jwt-bearer" \
--data-urlencode "client_assertion=${JWT_ASSERTION}" \
--url "${TOKEN_ENDPOINT}" |
The output of the script is as follows:
private_key_jwt authentication output
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Access_token attributes like signature, validity, audience and scopes must be verified by the client, similarly DAS API must also verify the access_token and must additionally check if the client id (=sub claim) is authorized. DAS API must maintain the whitelisted clients
access_token payload
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