curl -X POST "https://pagamentos.basspago.com.br/oauth/token" \
  --cert ./client.crt \
  --key ./client.key \
  --pass "SUA_SENHA_DO_CERTIFICADO" \
  -H "Content-Type: application/json" \
  -d '{
    "grant_type": "client_credentials",
    "client_id": "SEU_CLIENT_ID",
    "client_secret": "SEU_CLIENT_SECRET"
  }'

<?php

$ch = curl_init('https://pagamentos.basspago.com.br/oauth/token');

curl_setopt_array($ch, [
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_POST => true,
    CURLOPT_SSLCERT => './client.crt',
    CURLOPT_SSLKEY => './client.key',
    CURLOPT_KEYPASSWD => 'SUA_SENHA_DO_CERTIFICADO',
    CURLOPT_HTTPHEADER => ['Content-Type: application/json'],
    CURLOPT_POSTFIELDS => json_encode([
        'grant_type' => 'client_credentials',
        'client_id' => 'SEU_CLIENT_ID',
        'client_secret' => 'SEU_CLIENT_SECRET',
    ]),
]);

$response = curl_exec($ch);
curl_close($ch);

echo $response;

import fs from "node:fs";
import https from "node:https";
import axios from "axios";

const agent = new https.Agent({
  cert: fs.readFileSync("./client.crt"),
  key: fs.readFileSync("./client.key"),
  passphrase: "SUA_SENHA_DO_CERTIFICADO",
});

const { data } = await axios.post(
  "https://pagamentos.basspago.com.br/oauth/token",
  {
    grant_type: "client_credentials",
    client_id: "SEU_CLIENT_ID",
    client_secret: "SEU_CLIENT_SECRET",
  },
  { httpsAgent: agent }
);

console.log(data);

{
  "access_token": "eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9...",
  "token_type": "Bearer",
  "expires_in": 3600
}