https://github.com/DominikHorn/ASN1Parser

Minimalistic Swift parser for ASN.1 data. Currently supports DER and therefore also BER binary format
https://github.com/DominikHorn/ASN1Parser

asn-1 asn1 asn1-decoder asn1-der ssh-key swift

Last synced: 3 months ago
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Minimalistic Swift parser for ASN.1 data. Currently supports DER and therefore also BER binary format

• Host: GitHub
• URL: https://github.com/DominikHorn/ASN1Parser
• Owner: DominikHorn
• License: mit
• Created: 2021-11-10T15:58:47.000Z (about 3 years ago)
• Default Branch: main
• Last Pushed: 2023-10-04T12:46:27.000Z (about 1 year ago)
• Last Synced: 2024-07-12T11:27:56.814Z (4 months ago)
• Topics: asn-1, asn1, asn1-decoder, asn1-der, ssh-key, swift
• Language: Swift
• Homepage:
• Size: 354 KB
• Stars: 8
• Watchers: 2
• Forks: 3
• Open Issues: 4
• Metadata Files:
  • Readme: README.md
  • License: LICENSE.md

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README

        
# ASN1Parser

![tests](https://github.com/DominikHorn/ASN1Parser/actions/workflows/test.yml/badge.svg)

![coverage](https://img.shields.io/endpoint?url=https://gist.githubusercontent.com/DominikHorn/abb8b96dc5a9b8354fb3d70216aedc7d/raw/coverage-badge.json)

Safety first ASN.1 parsing in Swift.

## Documentation

You may import `ASN1Parser.docc` into Xcode, open the prebuilt static site found in 

`docs/documentation/asn1parser/index.html`, preview locally using `preview-doc.sh` 

or build the static website on your own using `gen-doc.sh`. 

Note that the static site is sadly not hostable via github pages due to its case insensitive

links which github pages routes as 404.

### Quick Start

Given the a DER encoded ASN.1 representation of a public key, for example as found in `.pem` files:

```swift

// Public key data blob from pem file

let pemBlob = "MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEQPtmXeh4gkzq30Zq3LXdgcl39fgCOBRZExhNWgZTSv5NTvbRoZNx28Ln/+Wtkfc42nWdunurluAeMPr0BrnLtA=="

guard let derData = Data(base64Encoded: pemBlob) else { return }

// Parse DER into ASN.1 value, which is a tree like structure

let tree = try DERParser.parse(derData)

// Access values within the tree

let q = try tree.asSequence[1].asBitString

```

### Feature Overview

- **runtime safe** ASN.1 parsing - error handling enforced by the swift compiler

- **minimalistic** - only contains the features you need

- **quick and easy** to use - immediately start parsing DER or BER encoded ASN.1 without any boilerplate

- **implicit ASN.1 format specification** - no need worry about explicitely specifying the expected data format.

  Simply access values in the ASN.1 tree and dynamically receive errors if they are not available.

Please note that the choice of implicit format specification is a deliberate

one. I believe ASN.1 is not particularily suited to be 1:1 mapped to swift

types. Therefore you will most likely have to introduce an abstraction layer,

i.e., an explicit ASN.1 format specification in addition to the swift type

defintion you'd ideally want to use throughout your remaining code. This

abstraction layer is however unnecessary IMHO, as it only consists of

boilerplate definitions and code for converting between the ASN.1 format and

your swift type. In addition to the often wasteful and messy nature of

boilerplate code, having two different abstractions for the same underlying

concept can introduce inconsistencies and thus bugs.

With implicit ASN.1 format specification, you can access ASN.1 data safely and

quicker while not having having to worry about introducing any accidental

inconsistencies in your codebase, because an additional abstraction layer won't

exist. Simply define your desired type in swift and dynamically load its

values from the decoded ASN.1 representation.

## Contributing

Pull requests are of course are highly appreciated :)