Add an utility method to read CSR PEM files

acme4j-utils/src/main/java/org/shredzone/acme4j/util/CertificateUtils.java

@@ -16,6 +16,7 @@ package org.shredzone.acme4j.util;
 import java.io.ByteArrayInputStream;
 import java.io.IOException;
 import java.io.InputStream;
+import java.io.InputStreamReader;
 import java.io.OutputStream;
 import java.io.OutputStreamWriter;
 import java.io.Writer;
@@ -31,9 +32,11 @@ import org.bouncycastle.asn1.x509.Extension;
 import org.bouncycastle.asn1.x509.GeneralName;
 import org.bouncycastle.asn1.x509.GeneralNames;
 import org.bouncycastle.cert.jcajce.JcaX509v3CertificateBuilder;
+import org.bouncycastle.openssl.PEMParser;
 import org.bouncycastle.openssl.jcajce.JcaPEMWriter;
 import org.bouncycastle.operator.OperatorCreationException;
 import org.bouncycastle.operator.jcajce.JcaContentSignerBuilder;
+import org.bouncycastle.pkcs.PKCS10CertificationRequest;
 import org.shredzone.acme4j.challenge.TlsSni01Challenge;
 
 /**
@@ -91,6 +94,23 @@ public final class CertificateUtils {
         }
     }
 
+    /**
+     * Reads a CSR PEM file.
+     *
+     * @param in
+     *            {@link InputStream} to read the CSR from.
+     * @return CSR that was read
+     */
+    public static PKCS10CertificationRequest readCSR(InputStream in) throws IOException {
+        try (PEMParser pemParser = new PEMParser(new InputStreamReader(in))) {
+            Object parsedObj = pemParser.readObject();
+            if (!(parsedObj instanceof PKCS10CertificationRequest)) {
+                throw new IOException("Not a PKCS10 CSR");
+            }
+            return (PKCS10CertificationRequest) parsedObj;
+        }
+    }
+
     /**
      * Creates a self-signed {@link X509Certificate} that can be used for
      * {@link TlsSni01Challenge}. The certificate is valid for 7 days.

acme4j-utils/src/test/java/org/shredzone/acme4j/util/CertificateUtilsTest.java

@@ -31,6 +31,7 @@ import java.util.List;
 import java.util.Set;
 
 import org.bouncycastle.asn1.x509.GeneralName;
+import org.bouncycastle.pkcs.PKCS10CertificationRequest;
 import org.junit.Before;
 import org.junit.Test;
 
@@ -107,6 +108,30 @@ public class CertificateUtilsTest {
         assertThat(getSANs(cert), containsInAnyOrder(subject));
     }
 
+    /**
+     * Test if {@link CertificateUtils#readCSR(InputStream)} reads an identical CSR.
+     */
+    @Test
+    public void testReadCSR() throws IOException {
+        KeyPair keypair = KeyPairUtils.createKeyPair(2048);
+
+        CSRBuilder builder = new CSRBuilder();
+        builder.addDomains("example.com", "example.org");
+        builder.sign(keypair);
+
+        PKCS10CertificationRequest original = builder.getCSR();
+        byte[] pemFile;
+        try (ByteArrayOutputStream baos = new ByteArrayOutputStream()) {
+            builder.write(baos);
+            pemFile = baos.toByteArray();
+        }
+
+        try (ByteArrayInputStream bais = new ByteArrayInputStream(pemFile)) {
+            PKCS10CertificationRequest read = CertificateUtils.readCSR(bais);
+            assertThat(original.getEncoded(), is(equalTo(read.getEncoded())));
+        }
+    }
+
     /**
      * Extracts all DNSName SANs from a certificate.
      *