Machine Installation id based Oauth 2

cygnus-cloud-service/src/main/java/com/cygnus/cloud/security/AccessTokenIssuer.java

@@ -0,0 +1,57 @@
+package com.cygnus.cloud.security;
+
+import com.nimbusds.jose.JWSAlgorithm;
+import com.nimbusds.jose.JWSHeader;
+import com.nimbusds.jose.crypto.RSASSASigner;
+import com.nimbusds.jwt.JWTClaimsSet;
+import com.nimbusds.jwt.SignedJWT;
+import java.time.Clock;
+import java.time.Instant;
+import java.util.Date;
+import java.util.Set;
+import java.util.UUID;
+import org.springframework.stereotype.Component;
+
+@Component
+class AccessTokenIssuer {
+
+    private final CommunicationSecurityProperties properties;
+    private final Clock clock;
+
+    AccessTokenIssuer(CommunicationSecurityProperties properties, Clock clock) {
+        this.properties = properties;
+        this.clock = clock;
+    }
+
+    TokenResponse issue(MachineClientPrincipal principal, Set<String> scopes) {
+        try {
+            Instant issuedAt = clock.instant();
+            Instant expiresAt = issuedAt.plus(properties.accessTokenTtl());
+            JWTClaimsSet claims = new JWTClaimsSet.Builder()
+                    .issuer(properties.issuerUri())
+                    .subject(principal.clientId())
+                    .audience(properties.audience())
+                    .issueTime(Date.from(issuedAt))
+                    .expirationTime(Date.from(expiresAt))
+                    .jwtID(UUID.randomUUID().toString())
+                    .claim("client_id", principal.clientId())
+                    .claim("installation_id", principal.installationId())
+                    .claim("scope", String.join(" ", scopes))
+                    .build();
+            SignedJWT jwt = new SignedJWT(
+                    new JWSHeader.Builder(JWSAlgorithm.RS256)
+                            .keyID("cygnus-access-token")
+                            .build(),
+                    claims);
+            jwt.sign(new RSASSASigner(
+                    PemKeyLoader.privateKey(properties.accessTokenPrivateKey())));
+            return new TokenResponse(
+                    jwt.serialize(),
+                    "Bearer",
+                    properties.accessTokenTtl().toSeconds(),
+                    String.join(" ", scopes));
+        } catch (Exception exception) {
+            throw new IllegalStateException("Unable to issue access token", exception);
+        }
+    }
+}