#MoonBit PKI

A pure-MoonBit ASN.1 DER codec and X.509 certificate toolkit.

Published as oilleelssq-wq/MoonBit-PKI and developed at https://github.com/oilleelssq-wq/MoonBit-PKI.

The library is being built feature by feature. The ASN.1/DER foundation (package oilleelssq-wq/MoonBit-PKI/asn1) is implemented and tested; the X.509 layer, PEM support and the x509dump command line tool follow in later increments.

#Why

MoonBit has no general-purpose ASN.1 or PKI library. Everything in the ecosystem that touches certificates, TLS, code signing, x5c JWT headers or PKCS structures ends up needing a DER decoder and an X.509 parser. The only related package on mooncakes.io today is a minimal DER reader aimed at RSA private keys, which covers PKCS#1/PKCS#8 but not certificates, extensions, CSRs or CRLs.

This module aims to fill that gap with a small, dependency-light, well-tested implementation:

A DER/BER-aware tag-length-value reader with strict DER canonical checks.
Primitive decoders for the types used by certificates and keys.
An object identifier type with dotted-decimal rendering.
Later: X.509 certificates (TBSCertificate, extensions, SAN, key usage), PEM, CSRs and a x509dump CLI.

#Goals

Stay in pure MoonBit with no C, JS or WASI dependencies.
Work on every backend (wasm, wasm-gc, js, native).
Prefer zero-copy views over the input buffer.
Report malformed input through a precise error type instead of panicking.

#Install

moon add oilleelssq-wq/MoonBit-PKI

#Usage

Decode a value and inspect it:

import { "oilleelssq-wq/MoonBit-PKI/asn1" @asn1 }

///|
test "read a DER integer" {
  let reader = @asn1.DerReader::from_bytes(b"\x02\x01\x2a")
  let value = try! reader.read_single()
  inspect(value.to_string(), content="[UNIVERSAL 2 primitive] 1B 2a")
}

Decode a certificate-shaped structure and read the first fields:

import { "oilleelssq-wq/MoonBit-PKI/asn1" @asn1 }

///|
fn inspect_sequence(bytes : Bytes) -> Unit raise @asn1.DerError {
  let outer = try! @asn1.DerReader::from_bytes(bytes).read_single()
  let children = outer.children()
  println(children[0].tag().to_string())
}

#Packages

Package	Contents
oilleelssq-wq/MoonBit-PKI/asn1	DER reader, value tree, primitive decoders, object identifiers

#API overview

Item	Purpose
DerReader	Cursor over DER bytes: read_tlv, read_element, read_all, read_single
Der	Decoded tree of Primitive/Constructed values
Tag, TagClass	Decoded identifier octets
decode_integer, decode_boolean, decode_bit_string, ...	Primitive content decoders
ObjectIdentifier	Dotted-decimal OIDs
DerError	Decode failures

#Development

moon check --target all --deny-warn
moon test --target all
moon fmt
moon info

#References

ITU-T X.680, Abstract Syntax Notation One (ASN.1): Specification of basic notation.
ITU-T X.690, ASN.1 encoding rules: BER, CER and DER.
RFC 5280, Internet X.509 Public Key Infrastructure Certificate and CRL Profile.

#License

Apache-2.0. See LICENSE.

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