Archive for the ‘certificates’ Category

Key File Formats: DER, PEM and PKCS #12 Explained

Posted on 11/26/2019 , Alexander,

Public key cryptography (asymmetric cryptography) is the foundation of the Internet and it is used for a variety of purposes.

Public and private keys can be stored in several different types of files. Each of these types can have its own encoding. The overall format of a file can be quite complex. It is important, however, to understand the purpose of these formats, and how they're used.

This document can be used as a primer for understanding these file/encoding formats.

The actual structure (objects and fields) of public/private keys, including X.509 certificates, is specified in various RFCs using the ASN.1 notation.

For example, an RSA private key contains the following fields:

RSAPrivateKey ::= SEQUENCE {
  version           Version,
  modulus           INTEGER,  -- n
  publicExponent    INTEGER,  -- e
  privateExponent   INTEGER,  -- d
  prime1            INTEGER,  -- p
  prime2            INTEGER,  -- q
  exponent1         INTEGER,  -- d mod (p-1)
  exponent2         INTEGER,  -- d mod (q-1)
  coefficient       INTEGER,  -- (inverse of q) mod p
  otherPrimeInfos   OtherPrimeInfos OPTIONAL
}

The most widely used format is X.509 and it's full syntax is defined by the RFC5280. X.509 provides the support for the "chain of trust" to verify a public key, as well as various extensions, primarily concerning the key's usage. RFC5280 also documents formats for CSR,CLR, etc.

PKCS #8 specification defines the structure of private keys (PKCS stands for Public-Key Cryptography Standards).

These specifications only stipulate the structure (fields and objects), we still need to decide how to "encode" these fields when we want to save them on disk.

Security considerations aside, it would be nice if everything was stored in some sort of a structured format that we're all used to, such as JSON or YAML, but this not the case for the majority of crypto formats, with the exception of JWK as explained later.
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OAuth2 JWT Verification Best Practices

Posted on 10/15/2019 , Alexander,

OAuth2 is very rapidly becoming the de-facto standard for securing APIs.
An OAuth2 JWT token is a signed JSON snippet containing fields (claims) that are needed to make a decision about granting access.

It is important to understand the inherent risks of OAuth2/JWT and make sure that the right mechanisms are in place to mitigate them.

A JWT token is similar to an X509 certificate. If a certificate is signed by a CA we trust (and if it is not expired, the signature is valid, etc.), we will trust the TLS client (or our browser will trust the server using this certificate). A JWT token is signed by an authorization server as opposed to a CA, so we have to trust the authorization server in order to authorize the client.
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Self-Signed Certificates Best Practices and How-to Guide

Posted on 08/10/2019 , Alexander,

Self-signed certificates are widely used for testing/development and sometimes in production for internal websites.

Self-signed certificates are created without any CA, thus they don't have a parent. The issuer is also the subject of the certificate.

In general, the use of self-signed certificates must be discouraged as they present an inherent security risk. For example, there is no way to revoke a self-signed cert. Using an internal CA for issuing all internal certificates is a much better option, we will cover it in a future post.

Self-signed certs come at a substantial maintenance cost -- issuing a cert for a long period of time is unsecure, but the short validity adds to the certificate renewal/distribution overhead.

The following best practices will help to make self-signed and internally-issued certificates more secure:
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How to Troubleshoot and Fix Certificate Validation Issues in Java

Posted on 07/25/2019 , Alexander,

Certificate validation errors are a frequent cause of issues when dealing with APIs and Web services calls, especially when self-signed certificates are used.
The error message is usually javax.net.ssl.SSLHandshakeException: PKIX path building failed.

How to Troubleshoot

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Java Keystore Management Best Practices

Posted on 07/23/2019 , Alexander Ananiev,

A keystore file is a database for storing application secrets (private keys), trust certificates and CA chains. Proper keystore/truststore management is extremely important for application security.

We’ve compiled a list of keystore-related best practices in our keystore management document.

Here is a brief summary of the document:
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Certificate Management Best Practices Summary

Posted on 11/25/2018 , Alexander Ananiev,

For more details, please refer to our certificate management document.

Best practices list:

  • Restrict certificate validity to short periods of time
  • Automate certificate renewal/refresh
  • Implement certificate validation/revocation mechanism (OSCP)
  • Do not use self-signed certs
  • Do not use wildcard certs
  • Establish and maintain a complete certificate inventory—you must know where each certificate is deployed, its expiration, etc.
  • Run frequent endpoint/port scans to detect self-signed and other out-of-policy certificates.
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Certificate Management Best Practices Document

Posted on 11/08/2018 , Alexander Ananiev,

We're incorporating more security reporting/compliance features into DPBuddy and we're also working on a new product related to certificate management.

As part of this work, we're attempting to compile and aggregate best practices related to certificates and key management.
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