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// Copyright The Notary Project Authors.
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package signature provides operations for types that implement
// signature.Envelope or signature.Signer.
//
// An Envelope is a structure that creates and verifies a signature using the
// specified signing algorithm with required validation. To register a new
// envelope, call RegisterEnvelopeType first during the initialization.
//
// A Signer is a structure used to sign payload generated after signature
// envelope created. The underlying signing logic is provided by the underlying
// local crypto library or the external signing plugin.
package signature
import (
"fmt"
"sync"
)
// Envelope provides basic functions to manipulate signatures.
type Envelope interface {
// Sign generates and sign the envelope according to the sign request.
Sign(req *SignRequest) ([]byte, error)
// Verify verifies the envelope and returns its enclosed payload and signer
// info.
Verify() (*EnvelopeContent, error)
// Content returns the payload and signer information of the envelope.
// Content is trusted only after the successful call to `Verify()`.
Content() (*EnvelopeContent, error)
}
// NewEnvelopeFunc defines a function to create a new Envelope.
type NewEnvelopeFunc func() Envelope
// ParseEnvelopeFunc defines a function that takes envelope bytes to create
// an Envelope.
type ParseEnvelopeFunc func([]byte) (Envelope, error)
// envelopeFunc wraps functions to create and parsenew envelopes.
type envelopeFunc struct {
newFunc NewEnvelopeFunc
parseFunc ParseEnvelopeFunc
}
// envelopeFuncs maps envelope media type to corresponding constructors and
// parsers.
var envelopeFuncs sync.Map // map[string]envelopeFunc
// RegisterEnvelopeType registers newFunc and parseFunc for the given mediaType.
// Those functions are intended to be called when creating a new envelope.
// It will be called while inializing the built-in envelopes(JWS/COSE).
func RegisterEnvelopeType(mediaType string, newFunc NewEnvelopeFunc, parseFunc ParseEnvelopeFunc) error {
if newFunc == nil || parseFunc == nil {
return fmt.Errorf("required functions not provided")
}
envelopeFuncs.Store(mediaType, envelopeFunc{
newFunc: newFunc,
parseFunc: parseFunc,
})
return nil
}
// RegisteredEnvelopeTypes lists registered envelope media types.
func RegisteredEnvelopeTypes() []string {
var types []string
envelopeFuncs.Range(func(k, v any) bool {
types = append(types, k.(string))
return true
})
return types
}
// NewEnvelope generates an envelope of given media type.
func NewEnvelope(mediaType string) (Envelope, error) {
val, ok := envelopeFuncs.Load(mediaType)
if !ok {
return nil, &UnsupportedSignatureFormatError{MediaType: mediaType}
}
return val.(envelopeFunc).newFunc(), nil
}
// ParseEnvelope generates an envelope for given envelope bytes with specified
// media type.
func ParseEnvelope(mediaType string, envelopeBytes []byte) (Envelope, error) {
val, ok := envelopeFuncs.Load(mediaType)
if !ok {
return nil, &UnsupportedSignatureFormatError{MediaType: mediaType}
}
return val.(envelopeFunc).parseFunc(envelopeBytes)
}
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