Posted in: X.509

X.509 Certificate Validation Process

Written by admin 211 次

The process of X.509 certificate validation involves several steps, including checking the certificate chain, verifying the chain policy, and handling missing root certificates. Here’s a detailed breakdown of the process:

X.509 Certificate Validation Process

  1. Receive the Certificate

    • The application or system receives a certificate (e.g., during an HTTPS connection).

  2. Parse the Certificate

    • The X.509 certificate is parsed to extract its components, such as the subject, issuer, public key, and other fields.

  3. Build the Certificate Chain

    • Start with the End-Entity Certificate: The certificate received is the end-entity certificate (e.g., the server’s certificate).
    • Find Intermediate Certificates: The system looks for intermediate certificates that link the end-entity certificate to a trusted root certificate. These intermediate certificates are typically included in the certificate chain provided by the server.
    • Locate the Root Certificate: The system attempts to find the root certificate in the local certificate store. The root certificate is the highest authority in the chain and is used to verify the trustworthiness of the entire chain.

  4. Verify the Certificate Chain

    • Signature Verification: Each certificate in the chain is verified using the public key of the issuing certificate. The end-entity certificate is verified using the intermediate certificate’s public key, the intermediate certificate is verified using the root certificate’s public key, and so on.
    • Validity Period Check: The system checks the validity period of each certificate to ensure it is within the valid date range.
    • Revocation Status Check: The system checks the revocation status of each certificate using CRLs (Certificate Revocation Lists) or OCSP (Online Certificate Status Protocol). This ensures that the certificate has not been revoked.

  5. Verify Chain Policy

    • Policy Constraints: The system checks policy constraints such as key usage, extended key usage, and other extensions to ensure they meet the required security policies.
    • Trust Anchors: The root certificate must be a trusted anchor in the local certificate store. If the root certificate is not trusted, the chain is considered invalid.

  6. Handle Missing Root Certificates

    • Local Certificate Store: If the root certificate is not found in the local certificate store, the system will attempt to retrieve it from the network.
    • Automatic Root Certificates Update: Windows includes a feature called Automatic Root Certificates Update that can retrieve missing root certificates from trusted sources, such as Microsoft’s update servers.
    • Network Retrieval: If network retrieval is enabled, the system will connect to the network to download the missing root certificate.

Detailed Steps

  1. Start with X.509 Objects

    • The system starts with the end-entity certificate and any intermediate certificates provided by the server.

  2. Build Chain

    • The system constructs the certificate chain by linking the end-entity certificate to the root certificate using intermediate certificates.

  3. Verify Chain Policy

    • The system verifies the signature, validity period, and revocation status of each certificate in the chain.
    • It checks policy constraints and ensures the root certificate is a trusted anchor.

  4. Retrieve Object from Network if Necessary

    • If the root certificate is not found in the local certificate store, the system attempts to retrieve it from the network using the Automatic Root Certificates Update feature.

Example Flow

  1. Receive Certificate Chain

    • Server sends the end-entity certificate and intermediate certificates.

  2. Parse Certificates

    • The system parses the received certificates.

  3. Build Chain

    • The system constructs the chain: End-Entity → Intermediate → Root.

  4. Verify Chain Policy

    • Verify signatures, validity periods, and revocation statuses.
    • Check policy constraints and ensure the root certificate is trusted.

  5. Handle Missing Root Certificate

    • If the root certificate is missing, the system retrieves it from the network.

Summary

  • Start with X.509 Objects: Begin with the end-entity and intermediate certificates.
  • Build Chain: Construct the certificate chain from end-entity to root.
  • Verify Chain Policy: Ensure each certificate in the chain is valid and trusted.
  • Retrieve Object from Network: If the root certificate is missing, retrieve it from the network using the Automatic Root Certificates Update feature.

This process ensures that the certificate chain is valid and trusted, providing secure communication and authentication.

Let me know if you need further details or additional information!

Back to Top