Cybersecurity and Ethical Hacking Tutorials

Configure OpenLDAP sudoRole policies with SSSD on RHEL, Rocky Linux, AlmaLinux, Oracle Linux, and CentOS Stream clients.

Fix OpenLDAP Error 49 for wrong bind DNs, passwords, userPassword ACLs, locked accounts, expired passwords, SSSD cache, PAM, and SSH authentication.

Fix OpenLDAP Error 50 for ldapadd, ldapmodify, ldapdelete, password changes, cn=config, and no-write-access-to-parent ACL failures.

Configure OpenLDAP ppolicy for password expiration, warnings, history, account lockout, grace logins, forced resets, and SSSD client behavior.

Configure OpenLDAP olcAccess ACLs for passwords, users, groups, SSSD, entry and children permissions, with safe testing and rollback.

Configure OpenLDAP client authentication with SSSD, authselect, StartTLS, and automatic home directories on RHEL, Rocky Linux, AlmaLinux, Oracle Linux, and CentOS Stream.

Configure OpenLDAP TLS on RHEL, Rocky Linux, AlmaLinux, Oracle Linux, and CentOS Stream using a private CA, StartTLS, LDAPS, and cn=config.

Fix curl error 60 and similar HTTPS failures on Linux when corporate SSL inspection replaces public certificates with a private root CA trusted on Windows but missing from the Linux trust store.

Configure OpenSSH authentication in sshd_config: password, public key, keyboard-interactive, host-based, GSSAPI, AuthenticationMethods, and Match blocks on Linux.

Use OpenSSL to view PEM, CRT, CER, chain, bundle, PFX, and P7B certificates. Check expiry, SAN, fingerprint, remote TLS certs, and verify chains.

Back up a PKCS12 truststore, check the keytool alias and SHA-256 fingerprint, import a CA only when missing, and exit cleanly for Ansible, systemd, and CI pipelines.

Complete keytool tutorial for Java keystores and truststores - generate PKCS12 keys, import CA-signed chains, automate truststore imports with Bash, sign and verify JAR files with jarsigner, build mTLS keystores and …

Create a code-signing keypair with keytool, sign a sample JAR with jarsigner, verify the signature, and read the PKIX chain warnings jarsigner prints for a self-signed certificate.

Create Java mTLS keystore and truststore files with keytool and OpenSSL, then run a mutual TLS HttpsServer lab that fails without a client cert and succeeds.

Set javax.net.ssl.trustStore and keyStore JVM properties after building a PKCS12 file with keytool: property names, -D flags, JAVA_TOOL_OPTIONS, and a lab that fails without trustStore then succeeds.

Fix PKIX after importing into the wrong cacerts. Find the Java truststore your app actually uses, including bundled JRE cacerts, and import with keytool.

Renew an expired TLS certificate in an existing Java PKCS12 keystore by checking expiry with keytool -list -v, exporting a CSR from the same alias, and importing the CA-signed reply without deleting the private key.

Fix keytool Invalid keystore format by matching JKS or PKCS12 storetype to the file, avoiding PEM certificates as keystores, and repairing empty or corrupt keystore paths.

Build a custom PKCS12 Java truststore with keytool for Docker and Kubernetes: RUN importcert in the image, set JAVA_TOOL_OPTIONS with trustStoreType=PKCS12, or use an initContainer with a mounted CA Secret and emptyDir …

Find which Java cacerts file your application actually uses: compare JAVA_HOME, java.home, bundled JRE paths, and javax.net.ssl.trustStore overrides before importing a CA certificate.

Fix Java No subject alternative names present by adding DNS and IP SAN entries with keytool -ext SAN so the certificate matches the hostname or IP clients use.

Fix keytool Failed to establish chain from reply by importing missing intermediate and root CA certificates before the server reply, using the correct keystore alias, or importing a complete PKCS7 chain bundle.

Fix keytool Certificate not imported, alias already exists by listing aliases, deleting or renaming the old entry, and re-importing to the correct keystore with a unique alias.

Fix keytool Input not an X.509 certificate by importing valid PEM, DER, or supported certificate-chain input instead of HTML, private keys, PFX files, or malformed PEM.

Fix java.security.UnrecoverableKeyException: Cannot recover key by aligning keystore and private key passwords in Tomcat, Spring Boot, and KeyManagerFactory.

Fix keytool Keystore was tampered with, or password was incorrect by checking storepass, file path, JKS vs PKCS12, cacerts, import passwords, and corruption.

Enable Spring Boot HTTPS on port 8443 with a PKCS12 keystore from keytool, set server.ssl.key-store in application.properties, add an optional truststore for private CAs, and verify with Java HttpClient.

Enable Tomcat 10 HTTPS on port 8443 with a PKCS12 keystore from keytool: import the CA chain before the server certificate, set certificateKeystoreFile in server.xml, and verify the TLS handshake.

Fix javax.net.ssl.SSLHandshakeException PKIX path building failed by importing your private CA chain into a PKCS12 truststore with keytool, then point the JVM at it with javax.net.ssl.trustStore — without editing …

Generate a private key with keytool -genkeypair, build a CSR with -certreq, sign it with a local OpenSSL CA, and replace the self-signed entry using -importcert on the same alias.