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Overview

    Package asn1 implements parsing of DER-encoded ASN.1 data structures, as defined in ITU-T Rec X.690.

    See also “A Layman's Guide to a Subset of ASN.1, BER, and DER,” http://luca.ntop.org/Teaching/Appunti/asn1.html.

    Index

    Constants

    View Source
    const (
    	TagBoolean         = 1
    	TagInteger         = 2
    	TagBitString       = 3
    	TagOctetString     = 4
    	TagOID             = 6
    	TagEnum            = 10
    	TagUTF8String      = 12
    	TagSequence        = 16
    	TagSet             = 17
    	TagPrintableString = 19
    	TagT61String       = 20
    	TagIA5String       = 22
    	TagUTCTime         = 23
    	TagGeneralizedTime = 24
    	TagGeneralString   = 27
    )

      ASN.1 tags represent the type of the following object.

      View Source
      const (
      	ClassUniversal       = 0
      	ClassApplication     = 1
      	ClassContextSpecific = 2
      	ClassPrivate         = 3
      )

        ASN.1 class types represent the namespace of the tag.

        Variables

        This section is empty.

        Functions

        func Marshal

        func Marshal(val interface{}) ([]byte, error)

          Marshal returns the ASN.1 encoding of val.

          In addition to the struct tags recognised by Unmarshal, the following can be used:

          ia5:		causes strings to be marshaled as ASN.1, IA5 strings
          omitempty:	causes empty slices to be skipped
          printable:	causes strings to be marshaled as ASN.1, PrintableString strings.
          utf8:		causes strings to be marshaled as ASN.1, UTF8 strings
          

          func Unmarshal

          func Unmarshal(b []byte, val interface{}) (rest []byte, err error)

            Unmarshal parses the DER-encoded ASN.1 data structure b and uses the reflect package to fill in an arbitrary value pointed at by val. Because Unmarshal uses the reflect package, the structs being written to must use upper case field names.

            An ASN.1 INTEGER can be written to an int, int32, int64, or *big.Int (from the math/big package). If the encoded value does not fit in the Go type, Unmarshal returns a parse error.

            An ASN.1 BIT STRING can be written to a BitString.

            An ASN.1 OCTET STRING can be written to a []byte.

            An ASN.1 OBJECT IDENTIFIER can be written to an ObjectIdentifier.

            An ASN.1 ENUMERATED can be written to an Enumerated.

            An ASN.1 UTCTIME or GENERALIZEDTIME can be written to a time.Time.

            An ASN.1 PrintableString or IA5String can be written to a string.

            Any of the above ASN.1 values can be written to an interface{}. The value stored in the interface has the corresponding Go type. For integers, that type is int64.

            An ASN.1 SEQUENCE OF x or SET OF x can be written to a slice if an x can be written to the slice's element type.

            An ASN.1 SEQUENCE or SET can be written to a struct if each of the elements in the sequence can be written to the corresponding element in the struct.

            The following tags on struct fields have special meaning to Unmarshal:

            application	specifies that a APPLICATION tag is used
            default:x	sets the default value for optional integer fields
            explicit	specifies that an additional, explicit tag wraps the implicit one
            optional	marks the field as ASN.1 OPTIONAL
            set		causes a SET, rather than a SEQUENCE type to be expected
            tag:x		specifies the ASN.1 tag number; implies ASN.1 CONTEXT SPECIFIC
            

            If the type of the first field of a structure is RawContent then the raw ASN1 contents of the struct will be stored in it.

            If the type name of a slice element ends with "SET" then it's treated as if the "set" tag was set on it. This can be used with nested slices where a struct tag cannot be given.

            Other ASN.1 types are not supported; if it encounters them, Unmarshal returns a parse error.

            func UnmarshalWithParams

            func UnmarshalWithParams(b []byte, val interface{}, params string) (rest []byte, err error)

              UnmarshalWithParams allows field parameters to be specified for the top-level element. The form of the params is the same as the field tags.

              Types

              type BitString

              type BitString struct {
              	Bytes     []byte // bits packed into bytes.
              	BitLength int    // length in bits.
              }

                BitString is the structure to use when you want an ASN.1 BIT STRING type. A bit string is padded up to the nearest byte in memory and the number of valid bits is recorded. Padding bits will be zero.

                func (BitString) At

                func (b BitString) At(i int) int

                  At returns the bit at the given index. If the index is out of range it returns false.

                  func (BitString) RightAlign

                  func (b BitString) RightAlign() []byte

                    RightAlign returns a slice where the padding bits are at the beginning. The slice may share memory with the BitString.

                    type Enumerated

                    type Enumerated int

                      An Enumerated is represented as a plain int.

                      type Flag

                      type Flag bool

                        A Flag accepts any data and is set to true if present.

                        type ObjectIdentifier

                        type ObjectIdentifier []int

                          An ObjectIdentifier represents an ASN.1 OBJECT IDENTIFIER.

                          func (ObjectIdentifier) Equal

                          func (oi ObjectIdentifier) Equal(other ObjectIdentifier) bool

                            Equal reports whether oi and other represent the same identifier.

                            func (ObjectIdentifier) String

                            func (oi ObjectIdentifier) String() string

                            type RawContent

                            type RawContent []byte

                              RawContent is used to signal that the undecoded, DER data needs to be preserved for a struct. To use it, the first field of the struct must have this type. It's an error for any of the other fields to have this type.

                              type RawValue

                              type RawValue struct {
                              	Class, Tag int
                              	IsCompound bool
                              	Bytes      []byte
                              	FullBytes  []byte // includes the tag and length
                              }

                                A RawValue represents an undecoded ASN.1 object.

                                type StructuralError

                                type StructuralError struct {
                                	Msg string
                                }

                                  A StructuralError suggests that the ASN.1 data is valid, but the Go type which is receiving it doesn't match.

                                  func (StructuralError) Error

                                  func (e StructuralError) Error() string

                                  type SyntaxError

                                  type SyntaxError struct {
                                  	Msg string
                                  }

                                    A SyntaxError suggests that the ASN.1 data is invalid.

                                    func (SyntaxError) Error

                                    func (e SyntaxError) Error() string