BAEL-4219 - How to read .pem file to get private and public key (#9676)

core-java-modules/core-java-security-2/src/main/java/com/baeldung/pem/JavaSecurityPemUtils.java

@@ -0,0 +1,48 @@
+package com.baeldung.pem;
+
+import org.apache.commons.codec.binary.Base64;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.charset.Charset;
+import java.nio.file.Files;
+import java.security.GeneralSecurityException;
+import java.security.KeyFactory;
+import java.security.interfaces.RSAPrivateKey;
+import java.security.interfaces.RSAPublicKey;
+import java.security.spec.PKCS8EncodedKeySpec;
+import java.security.spec.X509EncodedKeySpec;
+
+public class JavaSecurityPemUtils {
+
+    public static RSAPrivateKey readPKCS8PrivateKey(File file) throws GeneralSecurityException, IOException {
+        String key = new String(Files.readAllBytes(file.toPath()), Charset.defaultCharset());
+
+        String privateKeyPEM = key
+                .replace("-----BEGIN PRIVATE KEY-----", "")
+                .replaceAll(System.lineSeparator(), "")
+                .replace("-----END PRIVATE KEY-----", "");
+
+        byte[] encoded = Base64.decodeBase64(privateKeyPEM);
+
+        KeyFactory keyFactory = KeyFactory.getInstance("RSA");
+        PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(encoded);
+        return (RSAPrivateKey) keyFactory.generatePrivate(keySpec);
+    }
+
+    public static RSAPublicKey readX509PublicKey(File file) throws GeneralSecurityException, IOException {
+        String key = new String(Files.readAllBytes(file.toPath()), Charset.defaultCharset());
+
+        String publicKeyPEM = key
+                .replace("-----BEGIN PUBLIC KEY-----", "")
+                .replaceAll(System.lineSeparator(), "")
+                .replace("-----END PUBLIC KEY-----", "");
+
+        byte[] encoded = Base64.decodeBase64(publicKeyPEM);
+
+        KeyFactory keyFactory = KeyFactory.getInstance("RSA");
+        X509EncodedKeySpec keySpec = new X509EncodedKeySpec(encoded);
+        return (RSAPublicKey) keyFactory.generatePublic(keySpec);
+    }
+
+}

core-java-modules/core-java-security-2/src/main/resources/pem/private-key-pkcs8.pem

@@ -0,0 +1,28 @@
+-----BEGIN PRIVATE KEY-----
+MIIEvAIBADANBgkqhkiG9w0BAQEFAASCBKYwggSiAgEAAoIBAQCyO0YiTxLEP44S
+IGk/b9MlQAXS6nC4oYyTrAfxHCi/zxW/MmtWbY0K2JxOTkVSD5QbmvwkCutXi0k9
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+Q3OLn8GeH56ClJmNiWDhsA==
+-----END PRIVATE KEY-----

core-java-modules/core-java-security-2/src/main/resources/pem/public-key.pem

@@ -0,0 +1,9 @@
+-----BEGIN PUBLIC KEY-----
+MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAsjtGIk8SxD+OEiBpP2/T
+JUAF0upwuKGMk6wH8Rwov88VvzJrVm2NCticTk5FUg+UG5r8JArrV4tJPRHQyvqK
+wF4NiksuvOjv3HyIf4oaOhZjT8hDne1Bfv+cFqZJ61Gk0MjANh/T5q9vxER/7TdU
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+Pe9o1TY3VlOzk9ASZ1AeatvOir+iDVJ5OpKmLnzc46QgGPUsjIyo6Sje9dxpGtoG
+QQIDAQAB
+-----END PUBLIC KEY-----

core-java-modules/core-java-security-2/src/test/java/com/baeldung/pem/JavaSecurityPemUtilsUnitTest.java

@@ -0,0 +1,33 @@
+package com.baeldung.pem;
+
+
+import org.junit.jupiter.api.Test;
+
+import java.io.File;
+import java.security.interfaces.RSAPrivateKey;
+import java.security.interfaces.RSAPublicKey;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class JavaSecurityPemUtilsUnitTest {
+
+    @Test
+    public void whenReadPublicKeyFromPEMFile_thenSuccess() throws Exception {
+        File pemFile = new File(JavaSecurityPemUtilsUnitTest.class.getResource("/pem/public-key.pem").getFile());
+
+        RSAPublicKey publicKey = JavaSecurityPemUtils.readX509PublicKey(pemFile);
+
+        assertEquals("X.509", publicKey.getFormat());
+        assertEquals("RSA", publicKey.getAlgorithm());
+    }
+
+    @Test
+    public void whenReadPrivateKeyFromPEMFile_thenSuccess() throws Exception {
+        File pemFile = new File(JavaSecurityPemUtilsUnitTest.class.getResource("/pem/private-key-pkcs8.pem").getFile());
+
+        RSAPrivateKey privateKey = JavaSecurityPemUtils.readPKCS8PrivateKey(pemFile);
+
+        assertEquals("PKCS#8", privateKey.getFormat());
+        assertEquals("RSA", privateKey.getAlgorithm());
+    }
+}

libraries-security/src/main/java/com/baeldung/pem/BouncyCastlePemUtils.java

@@ -0,0 +1,71 @@
+package com.baeldung.pem;
+
+import org.bouncycastle.asn1.pkcs.PrivateKeyInfo;
+import org.bouncycastle.asn1.x509.SubjectPublicKeyInfo;
+import org.bouncycastle.openssl.PEMParser;
+import org.bouncycastle.openssl.jcajce.JcaPEMKeyConverter;
+import org.bouncycastle.util.io.pem.PemObject;
+import org.bouncycastle.util.io.pem.PemReader;
+
+import java.io.File;
+import java.io.FileReader;
+import java.io.IOException;
+import java.security.KeyFactory;
+import java.security.NoSuchAlgorithmException;
+import java.security.interfaces.RSAPrivateKey;
+import java.security.interfaces.RSAPublicKey;
+import java.security.spec.InvalidKeySpecException;
+import java.security.spec.PKCS8EncodedKeySpec;
+import java.security.spec.X509EncodedKeySpec;
+
+public class BouncyCastlePemUtils {
+
+    public static RSAPublicKey readX509PublicKey(File file) throws InvalidKeySpecException, IOException, NoSuchAlgorithmException {
+        KeyFactory factory = KeyFactory.getInstance("RSA");
+
+        try (FileReader keyReader = new FileReader(file);
+             PemReader pemReader = new PemReader(keyReader)) {
+
+            PemObject pemObject = pemReader.readPemObject();
+            byte[] content = pemObject.getContent();
+            X509EncodedKeySpec pubKeySpec = new X509EncodedKeySpec(content);
+            return (RSAPublicKey) factory.generatePublic(pubKeySpec);
+        }
+    }
+
+    public static RSAPublicKey readX509PublicKeySecondApproach(File file) throws IOException {
+        try (FileReader keyReader = new FileReader(file)) {
+
+            PEMParser pemParser = new PEMParser(keyReader);
+            JcaPEMKeyConverter converter = new JcaPEMKeyConverter();
+            SubjectPublicKeyInfo publicKeyInfo = SubjectPublicKeyInfo.getInstance(pemParser.readObject());
+
+            return (RSAPublicKey) converter.getPublicKey(publicKeyInfo);
+        }
+    }
+
+    public static RSAPrivateKey readPKCS8PrivateKey(File file) throws InvalidKeySpecException, IOException, NoSuchAlgorithmException {
+        KeyFactory factory = KeyFactory.getInstance("RSA");
+
+        try (FileReader keyReader = new FileReader(file);
+             PemReader pemReader = new PemReader(keyReader)) {
+
+            PemObject pemObject = pemReader.readPemObject();
+            byte[] content = pemObject.getContent();
+            PKCS8EncodedKeySpec privKeySpec = new PKCS8EncodedKeySpec(content);
+            return (RSAPrivateKey) factory.generatePrivate(privKeySpec);
+        }
+    }
+
+    public static RSAPrivateKey readPKCS8PrivateKeySecondApproach(File file) throws IOException {
+        try (FileReader keyReader = new FileReader(file)) {
+
+            PEMParser pemParser = new PEMParser(keyReader);
+            JcaPEMKeyConverter converter = new JcaPEMKeyConverter();
+            PrivateKeyInfo privateKeyInfo = PrivateKeyInfo.getInstance(pemParser.readObject());
+
+            return (RSAPrivateKey) converter.getPrivateKey(privateKeyInfo);
+        }
+    }
+
+}

libraries-security/src/main/resources/pem/private-key-pkcs8.pem

@@ -0,0 +1,28 @@
+-----BEGIN PRIVATE KEY-----
+MIIEvAIBADANBgkqhkiG9w0BAQEFAASCBKYwggSiAgEAAoIBAQCyO0YiTxLEP44S
+IGk/b9MlQAXS6nC4oYyTrAfxHCi/zxW/MmtWbY0K2JxOTkVSD5QbmvwkCutXi0k9
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+Q3OLn8GeH56ClJmNiWDhsA==
+-----END PRIVATE KEY-----

libraries-security/src/main/resources/pem/public-key.pem

@@ -0,0 +1,9 @@
+-----BEGIN PUBLIC KEY-----
+MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAsjtGIk8SxD+OEiBpP2/T
+JUAF0upwuKGMk6wH8Rwov88VvzJrVm2NCticTk5FUg+UG5r8JArrV4tJPRHQyvqK
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+QQIDAQAB
+-----END PUBLIC KEY-----

libraries-security/src/test/java/com/baeldung/pem/BouncyCastlePemUtilsUnitTest.java

@@ -0,0 +1,41 @@
+package com.baeldung.pem;
+
+
+import org.junit.jupiter.api.Test;
+
+import java.io.File;
+import java.security.interfaces.RSAPrivateKey;
+import java.security.interfaces.RSAPublicKey;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class BouncyCastlePemUtilsUnitTest {
+
+    @Test
+    public void whenReadPublicKeyFromPEMFile_thenSuccess() throws Exception {
+        File pemFile = new File(BouncyCastlePemUtilsUnitTest.class.getResource("/pem/public-key.pem").getFile());
+
+        RSAPublicKey publicKey1 = BouncyCastlePemUtils.readX509PublicKey(pemFile);
+        RSAPublicKey publicKey2 = BouncyCastlePemUtils.readX509PublicKeySecondApproach(pemFile);
+
+        assertEquals("X.509", publicKey1.getFormat());
+        assertEquals("RSA", publicKey1.getAlgorithm());
+
+        assertEquals("X.509", publicKey2.getFormat());
+        assertEquals("RSA", publicKey2.getAlgorithm());
+    }
+
+    @Test
+    public void whenReadPrivateKeyFromPEMFile_thenSuccess() throws Exception {
+        File pemFile = new File(BouncyCastlePemUtilsUnitTest.class.getResource("/pem/private-key-pkcs8.pem").getFile());
+
+        RSAPrivateKey privateKey1 = BouncyCastlePemUtils.readPKCS8PrivateKey(pemFile);
+        RSAPrivateKey privateKey2 = BouncyCastlePemUtils.readPKCS8PrivateKeySecondApproach(pemFile);
+
+        assertEquals("PKCS#8", privateKey1.getFormat());
+        assertEquals("RSA", privateKey1.getAlgorithm());
+
+        assertEquals("PKCS#8", privateKey2.getFormat());
+        assertEquals("RSA", privateKey2.getAlgorithm());
+    }
+}