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-- import ""

The macaroon package implements macaroons as described in the paper "Macaroons: Cookies with Contextual Caveats for Decentralized Authorization in the Cloud" (

See the macaroon bakery packages at for higher level services and operations that use macaroons.


const (
	TraceInvalid = TraceOpKind(iota)

	// TraceMakeKey represents the operation of calculating a
	// fixed length root key from the variable length input key.

	// TraceHash represents a keyed hash operation with one
	// or two values. If there is only one value, it will be in Data1.

	// TraceBind represents the operation of binding a discharge macaroon
	// to its primary macaroon. Data1 holds the signature of the primary
	// macaroon.

	// TraceFail represents a verification failure. If present, this will always
	// be the last operation in a trace.

func Base64Decode

func Base64Decode(data []byte) ([]byte, error)

Base64Decode base64-decodes the given data. It accepts both standard and URL encodings, both padded and unpadded.

type Caveat

type Caveat struct {
	// Id holds the id of the caveat. For first
	// party caveats this holds the condition;
	// for third party caveats this holds the encrypted
	// third party caveat.
	Id []byte

	// VerificationId holds the verification id. If this is
	// non-empty, it's a third party caveat.
	VerificationId []byte

	// For third-party caveats, Location holds the
	// ocation hint. Note that this is not signature checked
	// as part of the caveat, so should only
	// be used as a hint.
	Location string

Caveat holds a first person or third party caveat.

type Macaroon

type Macaroon struct {

Macaroon holds a macaroon. See Fig. 7 of for a description of the data contained within. Macaroons are mutable objects - use Clone as appropriate to avoid unwanted mutation.

func New

func New(rootKey, id []byte, loc string, version Version) (*Macaroon, error)

New returns a new macaroon with the given root key, identifier, location and version.

func (*Macaroon) AddFirstPartyCaveat

func (m *Macaroon) AddFirstPartyCaveat(condition []byte) error

AddFirstPartyCaveat adds a caveat that will be verified by the target service.

func (*Macaroon) AddThirdPartyCaveat

func (m *Macaroon) AddThirdPartyCaveat(rootKey, caveatId []byte, loc string) error

AddThirdPartyCaveat adds a third-party caveat to the macaroon, using the given shared root key, caveat id and location hint. The caveat id should encode the root key in some way, either by encrypting it with a key known to the third party or by holding a reference to it stored in the third party's storage.

func (*Macaroon) Bind

func (m *Macaroon) Bind(sig []byte)

Bind prepares the macaroon for being used to discharge the macaroon with the given signature sig. This must be used before it is used in the discharges argument to Verify.

func (*Macaroon) Caveats

func (m *Macaroon) Caveats() []Caveat

Caveats returns the macaroon's caveats. This method will probably change, and it's important not to change the returned caveat.

func (*Macaroon) Clone

func (m *Macaroon) Clone() *Macaroon

Clone returns a copy of the receiving macaroon.

func (*Macaroon) Id

func (m *Macaroon) Id() []byte

Id returns the id of the macaroon. This can hold arbitrary information.

func (*Macaroon) Location

func (m *Macaroon) Location() string

Location returns the macaroon's location hint. This is not verified as part of the macaroon.

func (*Macaroon) MarshalBinary

func (m *Macaroon) MarshalBinary() ([]byte, error)

MarshalBinary implements encoding.BinaryMarshaler by formatting the macaroon according to the version specified by MarshalAs.

func (*Macaroon) MarshalJSON

func (m *Macaroon) MarshalJSON() ([]byte, error)

MarshalJSON implements json.Marshaler by marshaling the macaroon in JSON format. The serialisation format is determined by the macaroon's version.

func (*Macaroon) SetLocation

func (m *Macaroon) SetLocation(loc string)

SetLocation sets the location associated with the macaroon. Note that the location is not included in the macaroon's hash chain, so this does not change the signature.

func (*Macaroon) Signature

func (m *Macaroon) Signature() []byte

Signature returns the macaroon's signature.

func (*Macaroon) TraceVerify

func (m *Macaroon) TraceVerify(rootKey []byte, discharges []*Macaroon) ([]Trace, error)

TraceVerify verifies the signature of the macaroon without checking any of the first party caveats, and returns a slice of Traces holding the operations used when verifying the macaroons.

Each element in the returned slice corresponds to the operation for one of the argument macaroons, with m at index 0, and discharges at 1 onwards.

func (*Macaroon) UnmarshalBinary

func (m *Macaroon) UnmarshalBinary(data []byte) error

UnmarshalBinary implements encoding.BinaryUnmarshaler. It accepts both V1 and V2 binary encodings.

func (*Macaroon) UnmarshalJSON

func (m *Macaroon) UnmarshalJSON(data []byte) error

UnmarshalJSON implements json.Unmarshaller by unmarshaling the given macaroon in JSON format. It accepts both V1 and V2 forms encoded forms, and also a base64-encoded JSON string containing the binary-marshaled macaroon.

After unmarshaling, the macaroon's version will reflect the version that it was unmarshaled as.

func (*Macaroon) Verify

func (m *Macaroon) Verify(rootKey []byte, check func(caveat string) error, discharges []*Macaroon) error

Verify verifies that the receiving macaroon is valid. The root key must be the same that the macaroon was originally minted with. The check function is called to verify each first-party caveat - it should return an error if the condition is not met.

The discharge macaroons should be provided in discharges.

Verify returns nil if the verification succeeds.

func (*Macaroon) VerifySignature

func (m *Macaroon) VerifySignature(rootKey []byte, discharges []*Macaroon) ([]string, error)

VerifySignature verifies the signature of the given macaroon with respect to the root key, but it does not validate any first-party caveats. Instead it returns all the applicable first party caveats on success.

The caller is responsible for checking the returned first party caveat conditions.

func (*Macaroon) Version

func (m *Macaroon) Version() Version

Version returns the version of the macaroon.

type Slice

type Slice []*Macaroon

Slice defines a collection of macaroons. By convention, the first macaroon in the slice is a primary macaroon and the rest are discharges for its third party caveats.

func (Slice) MarshalBinary

func (s Slice) MarshalBinary() ([]byte, error)

MarshalBinary implements encoding.BinaryMarshaler.

func (*Slice) UnmarshalBinary

func (s *Slice) UnmarshalBinary(data []byte) error

UnmarshalBinary implements encoding.BinaryUnmarshaler. It accepts all known binary encodings for the data - all the embedded macaroons need not be encoded in the same format.

type Trace

type Trace struct {
	RootKey []byte
	Ops     []TraceOp

Trace holds all toperations involved in verifying a macaroon, and the root key used as the initial verification key. This can be useful for debugging macaroon implementations.

func (Trace) Results

func (t Trace) Results() [][]byte

Results returns the output from all operations in the Trace. The result from ts.Ops[i] will be in the i'th element of the returned slice. When a trace has resulted in a failure, the last element will be nil.

type TraceOp

type TraceOp struct {
	Kind  TraceOpKind `json:"kind"`
	Data1 []byte      `json:"data1,omitempty"`
	Data2 []byte      `json:"data2,omitempty"`

TraceOp holds one possible operation when verifying a macaroon.

func (TraceOp) Result

func (op TraceOp) Result(input []byte) []byte

Result returns the result of computing the given operation with the given input data. If op is TraceFail, it returns nil.

type TraceOpKind

type TraceOpKind int

TraceOpKind represents the kind of a macaroon verification operation.

func (TraceOpKind) String

func (k TraceOpKind) String() string

String returns a string representation of the operation.

type Version

type Version uint16

Version specifies the version of a macaroon. In version 1, the macaroon id and all caveats must be UTF-8-compatible strings, and the size of any part of the macaroon may not exceed approximately 64K. In version 2, all field may be arbitrary binary blobs.

const (
	// V1 specifies version 1 macaroons.
	V1 Version = 1

	// V2 specifies version 2 macaroons.
	V2 Version = 2

	// LatestVersion holds the latest supported version.
	LatestVersion = V2

func (Version) String

func (v Version) String() string

String returns a string representation of the version; for example V1 formats as "v1".


A native Go implementation of macaroons







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