Crate synta 

Synta: ASN.1 parser, decoder, and encoder library

This library provides ASN.1 (Abstract Syntax Notation One) parsing, decoding, and encoding capabilities with support for DER (Distinguished Encoding Rules) and BER (Basic Encoding Rules).

Features

• Safe and ergonomic API leveraging Rust’s type system
• Zero-copy parsing where possible
• DER, BER, and CER encoding support
• Derive macros for automatic trait implementations (with derive feature)
• C FFI compatibility (with ffi feature)
• no_std support (with alloc)
• Optional serde Serialize/Deserialize support (with serde feature)

Cargo features

Feature	Description
std	Enable standard library support (enabled by default). Without this, alloc is used.
derive	Enable derive macros (Asn1Sequence, Asn1Set, Asn1Choice).
serde	Enable serde::Serialize/Deserialize for all ASN.1 types.
unchecked	Unsafe optimization: skip overflow and bounds checks in tag and length decoding. Only enable for fully trusted, pre-validated input. Malformed data may cause incorrect behaviour.

ASN.1 types

All standard ASN.1 types are re-exported at the crate root for convenient import. Two families of string and binary types are available:

Owned types (heap-allocating)

Suitable for constructing ASN.1 structures programmatically or when the decoded value must outlive the input buffer.

Rust type	ASN.1 type
OctetString	OCTET STRING
BitString	BIT STRING
Utf8String	UTF8String
PrintableString	PrintableString
IA5String	IA5String
Integer	INTEGER
Boolean	BOOLEAN
ObjectIdentifier	OBJECT IDENTIFIER

Zero-copy borrowed types

These types borrow directly from the decoder’s input buffer, avoiding allocation. Use them for parse-only workloads where the values do not need to outlive the encoded bytes.

Rust type	ASN.1 type
OctetStringRef	OCTET STRING
BitStringRef	BIT STRING
Utf8StringRef	UTF8String
PrintableStringRef	PrintableString
IA5StringRef	IA5String

Example

use synta::{Decoder, Encoding, Integer};

// Decode an integer
let data = &[0x02, 0x01, 0x2A]; // INTEGER 42
let mut decoder = Decoder::new(data, Encoding::Der);
let value: Integer = decoder.decode().unwrap();
assert_eq!(value.as_i64().unwrap(), 42);

Convenience traits: ToDer and FromDer

ToDer and FromDer are blanket-implemented on all types that implement Encode / Decode. They let you encode or decode a single value without constructing an Encoder or Decoder manually:

use synta::{Integer, ToDer, FromDer};

let n = Integer::from_i64(42);
let der = n.to_der().unwrap();
let n2 = Integer::from_der(&der).unwrap();
assert_eq!(n, n2);

Zero-copy borrowed types (e.g. OctetStringRef<'a>) cannot be decoded via FromDer because they carry a lifetime tied to the input buffer; use Decoder directly for those cases.

Serde support

Enable the serde feature to serialize and deserialize all ASN.1 types with any serde-compatible format (JSON, CBOR, etc.):

[dependencies]
synta = { version = "0.1", features = ["serde"] }

use synta::{Integer, ObjectIdentifier};

let i = Integer::from_i64(255);
let json = serde_json::to_string(&i).unwrap(); // "\"ff\""

let oid = ObjectIdentifier::new(&[1, 2, 840, 113549]).unwrap();
let json = serde_json::to_string(&oid).unwrap(); // "\"1.2.840.113549\""

Re-exports

pub use config::DecoderConfig;

pub use error::Error;

pub use error::Result;

pub use format::format_asn1_bytes;

pub use format::Asn1FormatMode;

pub use hex::bytes_to_hex;

pub use hex::hex_to_bytes;

pub use length::Length;

pub use tag::Tag;

pub use tag::TagClass;

pub use der::decoder::Decoder;

pub use der::encoder::Encoder;

pub use types::oid::ObjectIdentifier;

pub use types::primitive::Boolean;

pub use types::primitive::Enumerated;

pub use types::primitive::Integer;

pub use types::primitive::Null;

pub use types::primitive::Real;

pub use types::string::BitString;

pub use types::string::BmpString;

pub use types::string::GeneralString;

pub use types::string::IA5String;

pub use types::string::NumericString;

pub use types::string::OctetString;

pub use types::string::PrintableString;

pub use types::string::TeletexString;

pub use types::string::UniversalString;

pub use types::string::Utf8String;

pub use types::string::VisibleString;

pub use types::string::BitStringRef;

pub use types::string::IA5StringRef;

pub use types::string::OctetStringRef;

pub use types::string::PrintableStringRef;

pub use types::string::Utf8StringRef;

pub use types::time::expand_yy;

pub use types::time::parse2;

pub use types::time::parse4;

pub use types::time::GeneralizedTime;

pub use types::time::UtcTime;

pub use types::constructed::Element;

pub use types::constructed::Sequence;

pub use types::constructed::SequenceOf;

pub use types::constructed::Set;

pub use types::constructed::SetOf;

pub use types::constructed::SequenceOf as SequenceOfVec;

pub use types::constructed::SetOf as SetOfVec;

pub use types::tagged::ExplicitTag;

pub use types::tagged::ImplicitTag;

pub use types::raw::RawDer;

pub use traits::convenience::FromDer;

pub use traits::convenience::ToDer;

pub use traits::decode::Decode;

pub use traits::decode_implicit::DecodeImplicit;

pub use traits::encode::Encode;

pub use traits::tag_for_optional::TagForOptional;

pub use traits::tagged::Tagged;

Modules

ber

BER (Basic Encoding Rules) support

config

Decoder and encoder configuration

der

DER (Distinguished Encoding Rules) support

error

Error types and handling

format

ASN.1 formatting utilities

hex

Hexadecimal encoding and decoding utilities.

length

ASN.1 length encoding and decoding

reader

Reading utilities

tag

ASN.1 tag handling

traits

Core traits for ASN.1 encoding and decoding

types

ASN.1 type definitions.

writer

Writing utilities

Enums

Encoding

ASN.1 encoding rules

Derive Macros

Asn1Choice

Derive Encode, Decode, and Tagged for an ASN.1 CHOICE type.

Asn1Sequence

Derive Encode, Decode, and Tagged for an ASN.1 SEQUENCE type.

Asn1Set

Derive Encode, Decode, and Tagged for an ASN.1 SET type.