OP Corporate Payment API (1.5)

Authentication in OP Corporate Payment API is based on practices from OpenID Connect (OIDC) 1.0 and OAuth 2.0.

It is extremely important that the client_id, client_secret and client certificate private key are not exposed at any point. Together they represent the identity of the client and thereby the corporation. In the possession of an attacker they could be used to make fraudulent API calls potentially causing considerable damage.

To test the API in sandbox environment, please send an email at corp-payment-APIs@op.fi.

You can get production access for this API on OP API Admin.

To use these APIs against production you should replace host in the API examples below with https://corporate-api.apiauth.services.op.fi/

To ensure that the payment request payload is not altered and evidence of non-repudiation is maintained, a signature is calculated over the payment request body. The signature is a detached content JWS, as defined in RFC7515 with the following mandatory JWS headers:

• alg - string - only RS256 algorithm is currently supported for the signature algorithm
• kid - string - The signature Key Identifier (KID) received from the registration UI, used to map the signing key to the correct public key at the verifying end.
• b64 - boolean - The boolean value for this must be false. This indicates that the detached message payload is not base64 URL encoded when calculating the request signature. See RFC 7797 - The "b64" header Parameter
• urn:op.api.iat - number - This must be a JSON number representing the number of seconds from 1970-01-01T0:0:0Z as measured in GMT until the date/time.
• crit - array of string - This must be an array containing the critical header names, ["b64","urn:op.api.iat"]

The signature is computed in the detached mode, where the payload is not base64 URL encoded when forming the signature base string, but the UTF-8 encoded bytes of the sent request body are used as-is to construct the signature base string. See the example code below for more details.

When sending the payment request, the signature must be included in the request header "X-Req-Signature", and it will be validated against the key matching the kid parameter.

v1.5 (01/2023)

Added

• Request parameter ultimateCreditor added to endpoints SEPA Payment and SEPA Instant Payment. Using this parameter, API users will be able to add information on the ultimate payee (ultimate creditor)

  Changed

• Request parameter ´endToEndId´ now allows for more special characters

v1.4 (09/2022)

Added

• Request parameter ultimateDebtor added to endpoints SEPA Payment and SEPA Instant Payment. Using this parameter, API users will be able to add information on the ultimate payer (ultimate debtor)

v1.3 (04/2022)

Changed

• Response parameter paymentId removed as a duplicate from payment responses in endpoints SEPA Payment and SEPA Instant Payment

v1.2 (12/2021)

Added

• Corporate Payment API now supports OP Corporate Service Provider API usage

v1.1 (09/2021)

Changed

• Improved the description for creditor and debtor address request parameters
• Improved the way in which IBAN account numbers are handled

v1.0 (12/2019)

Initial version

#!/bin/bash

# To run this you need openssl and jq installed.

# Steps for registering the required keys and certificates
# 1. Valid Corporate API contract created in API Admin
# 2. OAuth clientId and clientSecret provisioned
# 3. MTLS private key generated: openssl genrsa -out sandbox-mtls.key 4096
# 4. MTLS certificate signing request (CN and other attributes are ignored): openssl req -new -key sandbox-mtls.key -out sandbox-mtls.csr
# 5. Valid MTLS certificate downloaded from API Admin as file "sandbox-mtls.crt" by uploading the certificate signing request (CSR) from the previous step 
# 6. Payment signing private key generated: openssl genrsa -out sandbox-signing.key 4096
# 7. Signing csr request: openssl req -new -key sandbox-signing.key -out sandbox-signing.csr
# 8. Signing KID (key identifier) received from the web UI by submitting the sandbox-signing.csr.

# OAuth credentials
clientId="TODO put here oauth client id"
clientSecret="TODO and here client secret"
# MTLS credentials
mtlsKey="sandbox-mtls.key"
mtlsCertificate="sandbox-mtls.crt"

# Payment signing credentials
signingKey="sandbox-signing.key"
signingKid="TODO and here signing KID"

API_SERVER="https://sandbox-api.apiauth.aws.op-palvelut.net"

echo "Getting access token"
reply=$(curl -s ${API_SERVER}/corporate-oidc/v1/token \
    --key ${mtlsKey} \
    --cert ${mtlsCertificate} \
    -H 'Content-Type: application/x-www-form-urlencoded' \
    -d "grant_type=client_credentials&client_id=${clientId}&client_secret=${clientSecret}")

token=$(echo $reply | jq -r .access_token)
echo "Access token is: $token"

## Initiate payment processing with payload signature

# Instruction id must be unique for each payment request
INSTRUCTIONID=$(date +%s)
# Sample payment request with dummy data
paymentRequest="{\"instructionId\":\"$INSTRUCTIONID\",\"endToEndId\":\"endToEndId\",\"creditor\":{\"name\":\"Creditor Name\",\"iban\":\"FI3859991620004143\",\"address\":{\"addressLine\":[\"a1\",\"a2\"],\"country\":\"FI\"}},\"debtor\":{\"name\":\"Debtor Name\",\"iban\":\"FI6359991620004275\",\"address\":{\"addressLine\":[\"a1\",\"a2\"],\"country\":\"FI\"}},\"instructedAmount\":{\"currency\":\"EUR\",\"amount\":\"0.16\"},\"reference\":\"00000000000000482738\"}"

## Signing the payload is mandatory for payment requests

# Issued at, in unix timestamp format
IAT=$(date +%s)

# Form the JWS header with mandatory fields
HEADER="{\"b64\":false,\"crit\":[\"b64\",\"urn:op.api.iat\"],\"alg\":\"RS256\",\"urn:op.api.iat\":${IAT},\"kid\":\"${signingKid}\"}"

# Base64 encode the header. JWT encoding is slightly different from default output of base64, so make the necessary changes to make the output URL-safe, and remove trailing padding (=).
HEADER_ENC=$(echo -n "${HEADER}" | base64 | tr -- '+/=' '-_ ' | tr -d '[:space:]')

# Sign the header and payload. The signature calculation in the detached body JWS is slightly different from the standard way, as the payload is not base64-encoded
# before signing, but included as-is in the signature plain text. The signing algorithm is RS256, also known as "RSA Digital Signature Algorithm with SHA-256".
# The resulting signature is base64-encoded, and the same URL-safe transformations are applied.
SIGNATURE=$(echo -n "${HEADER_ENC}.${paymentRequest}" | openssl dgst -sha256 -sign ${signingKey} -binary | openssl base64 -e -A | tr -- '+/=' '-_ ' | tr -d '[:space:]')

# The signature header includes the base64-encoded JWS header, followed by two dots (..), and the base64-urlsafe-encoded signature. The actual message payload is not
# repeated in the signature
REQ_SIGNATURE="${HEADER_ENC}..${SIGNATURE}"

# The signature is included in the "X-Req-Signature" header.
echo "Sending payment request"
paymentResponse=$(curl -s ${API_SERVER}/corporate-payment/v1/sepa-payment \
    --key ${mtlsKey} \
    --cert ${mtlsCertificate} \
    -H 'Content-Type: application/json' \
    -H "Authorization: Bearer $token" \
    -H "X-Req-Signature: ${REQ_SIGNATURE}" \
    -d "$paymentRequest")

echo $paymentResponse | jq -C .