TLS Certificate Analyzer

🔐 What is a TLS Certificate?

TLS (Transport Layer Security) certificates, commonly called SSL certificates, are digital documents that authenticate the identity of websites and enable encrypted connections. They're the foundation of secure communication on the internet, indicated by the padlock icon in your browser's address bar.

This analyzer helps you examine X.509 certificates in detail, understand their properties, verify their validity, and identify potential security concerns. Whether you're a DevOps engineer deploying certificates, a security professional auditing systems, or a developer debugging TLS issues, this tool provides comprehensive insights.

⚙️ How to Use This Tool

Getting Started:

1. Paste Certificate: Copy your PEM-encoded certificate and paste it in the input area
2. Upload File: Or upload a .pem, .crt, or .cer file directly
3. Analyze: Click the 'Analyze Certificate' button to parse and examine the certificate
4. Review Results: Explore the certificate chain, details, and security analysis

🔗 Certificate Chain Analysis:

• Paste multiple certificates to analyze the complete chain
• The tool automatically identifies Root CAs, Intermediate CAs, and Leaf certificates
• Visual hierarchy shows the trust relationship between certificates

📋 Supported Formats:

-----BEGIN CERTIFICATE-----
MIIDXTCCAkWgAwIBAgIJAJC1...
(Base64 encoded certificate data)
-----END CERTIFICATE-----

📊 Understanding Certificate Information

Basic Fields:

• Subject: The entity the certificate identifies (e.g., domain name, organization)
• Issuer: The Certificate Authority (CA) that issued and signed the certificate
• Serial Number: Unique identifier assigned by the CA
• Version: X.509 version (v3 is current standard with extension support)

Validity Period:

• Not Before: Date when the certificate becomes valid
• Not After: Expiration date - certificate must be renewed before this date
• Public TLS certificates are limited to 398 days maximum validity

Cryptographic Properties:

• Public Key Algorithm: RSA (2048/4096-bit) or ECDSA (P-256/P-384) are common choices
• Signature Algorithm: SHA-256 with RSA or ECDSA is the modern standard
• Fingerprints: SHA-256 and SHA-1 hashes for certificate verification

Important Extensions:

• Subject Alternative Names (SAN): Additional domain names the certificate covers
• Key Usage: Defines what cryptographic operations the key can perform
• Extended Key Usage: Specific purposes like server auth, client auth, code signing
• Basic Constraints: Indicates if certificate can sign other certificates (CA flag)

🔗 Certificate Chain Explained

A certificate chain (or chain of trust) establishes the trustworthiness of a certificate through a hierarchy:

🔒 Root CA (Self-signed, trusted by browsers/OS)
└── 📁 Intermediate CA (Signed by Root)
    └── 📄 Leaf Certificate (Your domain certificate)

Chain Validation Process:

1. Browser receives the leaf certificate for your domain
2. Checks if the issuer's certificate is available (intermediate CA)
3. Continues up the chain until reaching a trusted root CA
4. Verifies each signature and validity period along the way

Common Issues:

• Incomplete Chain: Missing intermediate certificates cause validation failures
• Wrong Order: Certificates must be served in correct order (leaf first)
• Expired Intermediate: Even if leaf is valid, expired intermediate breaks the chain

🛡️ Security Analysis Checks

This tool performs comprehensive security analysis on certificates:

Critical Issues:

• Expired certificates
• Certificates not yet valid
• Certificates expiring within 7 days

High Risk Issues:

• Weak signature algorithms (MD5, SHA-1)
• RSA keys smaller than 2048 bits
• Certificates expiring within 30 days

Medium Risk Issues:

• Self-signed non-CA certificates
• Missing Subject Alternative Names
• Certificates expiring within 90 days

Recommendations:

• Use RSA 2048-bit or higher (4096-bit for long-term security)
• Use ECDSA P-256 or P-384 for modern deployments
• Always use SHA-256 or stronger signature algorithms
• Include all domain names in SAN extension
• Automate renewal before expiration (Let's Encrypt, Certbot)

💼 Practical Use Cases

1. Pre-deployment Verification

Before deploying a new certificate, analyze it to ensure:

• Domain names in SAN match your configuration
• Validity period is appropriate
• Chain is complete and properly ordered
• No security issues are flagged

2. Troubleshooting TLS Errors

When users report certificate warnings:

• Check if certificate has expired
• Verify domain names match
• Ensure intermediate certificates are included
• Confirm certificate is for correct environment (staging vs production)

3. Security Auditing

For compliance and security reviews:

• Verify key strengths meet requirements
• Check signature algorithms are approved
• Audit certificate lifetimes
• Document certificate fingerprints

4. Certificate Inventory

Managing multiple certificates:

• Track expiration dates for renewal planning
• Document issuing CAs
• Record key algorithms and sizes
• Monitor for deprecated configurations

📚 How to Obtain Certificates

From Your Server (OpenSSL):

# Get certificate from remote server
openssl s_client -connect example.com:443 -showcerts </dev/null 2>/dev/null | openssl x509 -outform PEM

# Get full chain
openssl s_client -connect example.com:443 -showcerts </dev/null 2>/dev/null

# Save to file
echo | openssl s_client -connect example.com:443 -showcerts 2>/dev/null | openssl x509 > cert.pem

From Local Files:

# View certificate details
openssl x509 -in certificate.pem -text -noout

# Convert DER to PEM
openssl x509 -inform DER -in certificate.der -out certificate.pem

# Extract from PKCS#12/PFX
openssl pkcs12 -in certificate.pfx -clcerts -nokeys -out certificate.pem

From Browser:

1. Click the padlock icon in the address bar
2. Navigate to certificate details
3. Export or copy the PEM-encoded certificate

❓ Frequently Asked Questions

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