micro509/der

DER reading and writing primitives.

The building blocks every other entrypoint is made of, for the cases the typed APIs do not cover:

• decoding a private extension's extnValue inside an ExtensionDecoder
• encoding the bytes a CustomExtension carries
• inspecting a structure this library does not model

Reading accepts definite lengths and minimal length encodings, rejects the high-tag-number form, and applies a nesting-depth guard capped at DEFAULT_MAX_DER_DEPTH. BER-only constructs fail.

Readers and decoders take untrusted bytes, so each one comes as a pair:

• decodeDerInteger returns a DecodeDerResult
• decodeDerIntegerOrThrow throws

Writers take typed input and throw, matching encodeName and pemEncode.

All operations are synchronous.

Functions

• decodeDerBitString — Decodes a BIT STRING element (tag 0x03) into a DerBitString.
• decodeDerBitStringOrThrow — Decodes a BIT STRING element (tag 0x03) into a DerBitString.
• decodeDerBoolean — Decodes a BOOLEAN element (tag 0x01).
• decodeDerBooleanOrThrow — Decodes a BOOLEAN element (tag 0x01).
• decodeDerInteger — Decodes an INTEGER element (tag 0x02) into a number.
• decodeDerIntegerOrThrow — Decodes an INTEGER element (tag 0x02) into a number.
• decodeDerOctetString — Decodes an OCTET STRING element (tag 0x04) into its payload bytes.
• decodeDerOctetStringOrThrow — Decodes an OCTET STRING element (tag 0x04) into its payload bytes.
• decodeDerOid — Decodes an OBJECT IDENTIFIER element (tag 0x06) into dotted-decimal form.
• decodeDerOidOrThrow — Decodes an OBJECT IDENTIFIER element (tag 0x06) into dotted-decimal form.
• decodeDerString — Decodes a string element into text, dispatching on its tag.
• decodeDerStringOrThrow — Decodes a string element into text, dispatching on its tag.
• decodeDerTime — Decodes a UTCTime (tag 0x17) or GeneralizedTime (tag 0x18) element into a Date.
• decodeDerTimeOrThrow — Decodes a UTCTime (tag 0x17) or GeneralizedTime (tag 0x18) element into a Date.
• derChildren — Reads the direct children of a constructed parent within source.
• derChildrenOrThrow — Reads the direct children of a constructed parent within source.
• readDerElement — Reads one TLV element from bytes starting at offset.
• readDerElementOrThrow — Reads one TLV element from bytes starting at offset.
• readDerRoot — Reads the single top-level TLV element from bytes.
• readDerRootOrThrow — Reads the single top-level TLV element from bytes.
• readDerSequence — Reads a DER-encoded SEQUENCE from bytes and returns its direct children.
• readDerSequenceOrThrow — Reads a DER-encoded SEQUENCE from bytes and returns its direct children.
• hexToBytes — Converts a hex string (even or odd length) to a Uint8Array.
• toHex — Converts raw bytes to a lowercase hex string with no separator.
• assertDerMaxDepth — Walks the full DER tree rooted in bytes.
• derBitString — Encodes a DER BIT STRING (tag 0x03).
• derBmpString — Encodes a DER BMPString (tag 0x1e) as big-endian UTF-16.
• derBoolean — Encodes a DER BOOLEAN (tag 0x01): true → 0xff, false → 0x00.
• concatBytes — Concatenates multiple byte arrays into a single Uint8Array.
• derExplicitContext — Wraps a value in an explicit context-specific constructed tag (0xa0 + tag).
• derGeneralizedTime — Encodes a Date as a DER GeneralizedTime (tag 0x18), format YYYYMMDDHHMMSSZ.
• derIa5String — Encodes a DER IA5String (tag 0x16).
• derImplicitConstructedContext — Wraps a value in an implicit context-specific constructed tag (0xa0 + tag).
• derImplicitPrimitiveContext — Wraps a value in an implicit context-specific primitive tag (0x80 + tag).
• derInteger — Encodes raw big-endian bytes as a DER INTEGER (tag 0x02).
• derIntegerFromNumber — Encodes a non-negative JavaScript number as a DER INTEGER.
• derNull — Produces a DER NULL element (tag 0x05, zero-length value).
• derOid — Encodes a dotted-decimal OID string as a DER OBJECT IDENTIFIER (tag 0x06).
• derOctetString — Wraps raw bytes in an OCTET STRING element (tag 0x04).
• derPrintableString — Encodes a DER PrintableString (tag 0x13).
• derSequence — Wraps concatenated children in a SEQUENCE (tag 0x30).
• derSet — Wraps children in a SET (tag 0x31) after DER-sorting them lexicographically by encoded bytes,
• derTime — Encodes a Date as the appropriate DER time type per RFC 5280.
• derTlv — Builds a complete DER TLV (tag-length-value) element:
• derUniversalString — Encodes a DER UniversalString (tag 0x1c) as big-endian UTF-32.
• derUtcTime — Encodes a Date as a DER UTCTime (tag 0x17), format YYMMDDHHMMSSZ.
• derUtf8String — Encodes a DER UTF8String (tag 0x0c).

Types

• DecodeDerErrorCode — Machine-readable failure reason for the DER readers and decoders.
• DecodeDerFailure — Structured failure payload for DER reading and decoding.
• DecodeDerResult — Success-or-failure result from a DER reader or decoder.
• DerBitString — A BIT STRING payload and the number of unused trailing bits in its final byte.
• DerElement — A single parsed ASN.1 TLV element with byte-range metadata.
• ReadRootElementOptions — Options for readRootElement.
• ReadSequenceChildrenOptions — Options for readSequenceChildren.

Variables

• DEFAULT_MAX_DER_DEPTH — Maximum nesting depth allowed when recursively walking a DER structure.