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Public Key Infrastructure

[!NOTE] This framework started as a fork of the libraries published at https://github.com/sop. It has diverged substantially since — the code has been reworked, extended and maintained to meet the Spomky-Labs requirements — and the two are no longer interchangeable. All credits for the original work go to its developer.

A PHP Framework

• X.509 public key certificates, attribute certificates,
• X.690 Abstract Syntax Notation One (ASN.1) Distinguished Encoding Rules (DER) encoding and decoding
• X.501 ASN.1 types, X.520 attributes and DN parsing.
• RFC 7468 textual encodings of cryptographic structures (PEM).
• Various ASN.1 types for cryptographic applications.
• Cryptography support for various PKCS applications.

Requirements

• PHP >=8.1
• mbstring

The extension gmp or bcmath is highly recommended

Installation

This library is distributed on Packagist; the source lives on GitHub.

Issuing certificates from a certification request

TBSCertificate::fromCSR() builds a certificate from a certification request. Everything a certification request contains is chosen by whoever submitted it, so an issuer must treat it as untrusted input:

• the signature of the request is not verified by fromCSR(). Call CertificationRequest::verify() yourself before using it;
• extensions that decide what a certificate is allowed to do — basicConstraints, keyUsage, extKeyUsage, nameConstraints, policyConstraints, policyMappings, inhibitAnyPolicy, certificatePolicies and authorityKeyIdentifier — are never copied from the request. They belong to the issuer, which sets them with withExtensions() / withAdditionalExtensions();

• name the extensions you are willing to honour as the second argument. Anything not named is dropped:

• leaving the argument out copies every requested extension that is not forbidden, subjectAltName and authorityInformationAccess included, and raises a deprecation notice. That default is a deny list: the set of extensions that matter grows over time and every future one is copied. It becomes the empty allow list in the next major release. Pass null explicitly if you really want it;
• an unknown extension marked critical is never copied. It would be signed verbatim and no conforming validator, this library's own included, would then accept the certificate.

Validating a certification path

The trust anchor is an input to the validation process, never something read out of the material the peer sent. Start from the certificates you trust and let the library build the path to the target:

If you already hold the path, name the anchor explicitly:

Do not validate a chain a peer supplied without an anchor. Left to itself, validation would fall back to the first certificate of the path — one the peer chose — and confirm only that the chain is internally consistent. A path built by CertificationPath::fromCertificateChain() refuses to validate without an explicit anchor for that reason, and a path built by CertificationPath::create() raises a deprecation notice when it falls back, so an application can find the call sites before the fallback is removed in the next major release. A path built by toTarget() is already headed by a certificate from the trust list you gave it and needs neither.

Security

Path validation checks that a chain is well-formed and leads to a trust anchor you named. It does not check revocation: the library never contacts a CRL distribution point or an OCSP responder, so a revoked certificate still validates. Revocation is the calling application's responsibility.

Attribute certificate validation does not implement RFC 5755 section 5 check 4 on its own: name the authorities you trust to issue attribute certificates with ACValidationConfig::withTrustedAttributeAuthorities(), or the validator accepts whatever end-entity certificate the issuer path ends in.

Ed25519 and Ed448 are in the default set of allowed signature algorithms, but whether a signature made with them can be checked depends on the runtime: the OpenSSL extension only grew EdDSA recently, and ext-sodium — bundled since PHP 7.2 — covers Ed25519 alone. Verification fails closed where the runtime cannot do it. Ask OpenSSLCrypto::supportsSignatureAlgorithm() if you would rather narrow the configured set than have a chain refused during validation.

Certificate::equals() compares the two encodings octet by octet, and CertificateBundle::contains() is built on it. Use Certificate::hasEqualSubjectIdentity() for the looser "same subject, same key, same serial number" question — it is not an identity check, since two certificates can agree on all three and still be issued by different issuers with different extensions.

Found a vulnerability? Do not open a public issue — read SECURITY.md and report it privately.

License

This project is licensed under the MIT License.