interface.go

Documentation: github.com/sigstore/cosign/v2/pkg/providers

     1  //
     2  // Copyright 2021 The Sigstore Authors.
     3  //
     4  // Licensed under the Apache License, Version 2.0 (the "License");
     5  // you may not use this file except in compliance with the License.
     6  // You may obtain a copy of the License at
     7  //
     8  //     http://www.apache.org/licenses/LICENSE-2.0
     9  //
    10  // Unless required by applicable law or agreed to in writing, software
    11  // distributed under the License is distributed on an "AS IS" BASIS,
    12  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13  // See the License for the specific language governing permissions and
    14  // limitations under the License.
    15  
    16  package providers
    17  
    18  import (
    19  	"context"
    20  	"errors"
    21  	"fmt"
    22  	"sync"
    23  )
    24  
    25  var (
    26  	m         sync.Mutex
    27  	providers []providerEntry
    28  )
    29  
    30  type providerEntry struct {
    31  	name string
    32  	p    Interface
    33  }
    34  
    35  // Interface is what providers need to implement to participate in furnishing OIDC tokens.
    36  type Interface interface {
    37  	// Enabled returns true if the provider is enabled.
    38  	Enabled(ctx context.Context) bool
    39  
    40  	// Provide returns an OIDC token scoped to the provided audience.
    41  	Provide(ctx context.Context, audience string) (string, error)
    42  }
    43  
    44  // Register is used by providers to participate in furnishing OIDC tokens.
    45  func Register(name string, p Interface) {
    46  	m.Lock()
    47  	defer m.Unlock()
    48  
    49  	for _, pe := range providers {
    50  		if pe.name == name {
    51  			panic(fmt.Sprintf("duplicate provider for name %q, %T and %T", name, pe.p, p))
    52  		}
    53  	}
    54  	providers = append(providers, providerEntry{name: name, p: p})
    55  }
    56  
    57  // Enabled checks whether any of the registered providers are enabled in this execution context.
    58  func Enabled(ctx context.Context) bool {
    59  	m.Lock()
    60  	defer m.Unlock()
    61  
    62  	for _, provider := range providers {
    63  		if provider.p.Enabled(ctx) {
    64  			return true
    65  		}
    66  	}
    67  	return false
    68  }
    69  
    70  // Provide fetches an OIDC token from one of the active providers.
    71  func Provide(ctx context.Context, audience string) (string, error) {
    72  	m.Lock()
    73  	defer m.Unlock()
    74  
    75  	var id string
    76  	var err error
    77  	for _, provider := range providers {
    78  		if !provider.p.Enabled(ctx) {
    79  			continue
    80  		}
    81  		id, err = provider.p.Provide(ctx, audience)
    82  		if err == nil {
    83  			return id, nil
    84  		}
    85  	}
    86  	// return the last id/err combo, unless there wasn't an error in
    87  	// which case provider.Enabled() wasn't checked.
    88  	if err == nil {
    89  		err = errors.New("no providers are enabled, check providers.Enabled() before providers.Provide()")
    90  	}
    91  	return id, err
    92  }
    93  
    94  // ProvideFrom fetches the specified provider
    95  func ProvideFrom(_ context.Context, provider string) (Interface, error) {
    96  	m.Lock()
    97  	defer m.Unlock()
    98  
    99  	for _, p := range providers {
   100  		if p.name == provider {
   101  			return p.p, nil
   102  		}
   103  	}
   104  	return nil, fmt.Errorf("%s is not a valid provider", provider)
   105  }
   106
View as plain text