| 1 | // SPDX-License-Identifier: GPL-3.0-or-later |
| 2 | |
| 3 | package cloudauth |
| 4 | |
| 5 | import ( |
| 6 | "context" |
| 7 | "errors" |
| 8 | "fmt" |
| 9 | "slices" |
| 10 | "sync" |
| 11 | "time" |
| 12 | |
| 13 | "github.com/Azure/azure-sdk-for-go/sdk/azcore" |
| 14 | "github.com/Azure/azure-sdk-for-go/sdk/azcore/policy" |
| 15 | ) |
| 16 | |
| 17 | const ( |
| 18 | DefaultTokenRefreshMargin = 5 * time.Minute |
| 19 | ) |
| 20 | |
| 21 | type TokenProvider struct { |
| 22 | mu sync.Mutex |
| 23 | cred azcore.TokenCredential |
| 24 | scopes []string |
| 25 | refreshMargin time.Duration |
| 26 | now func() time.Time |
| 27 | |
| 28 | cachedToken string |
| 29 | cachedExpiry time.Time |
| 30 | } |
| 31 | |
| 32 | func NewTokenProvider(cred azcore.TokenCredential, scopes []string, refreshMargin time.Duration) (*TokenProvider, error) { |
| 33 | if cred == nil { |
| 34 | return nil, errors.New("token credential is nil") |
| 35 | } |
| 36 | if len(scopes) == 0 { |
| 37 | return nil, errors.New("token scopes are required") |
| 38 | } |
| 39 | if slices.Contains(scopes, "") { |
| 40 | return nil, errors.New("token scopes contain an empty value") |
| 41 | } |
| 42 | if refreshMargin <= 0 { |
| 43 | refreshMargin = DefaultTokenRefreshMargin |
| 44 | } |
| 45 | |
| 46 | return &TokenProvider{ |
| 47 | cred: cred, |
| 48 | scopes: scopes, |
| 49 | refreshMargin: refreshMargin, |
| 50 | now: time.Now, |
| 51 | }, nil |
| 52 | } |
| 53 | |
| 54 | func (p *TokenProvider) Token(ctx context.Context) (string, time.Time, error) { |
| 55 | p.mu.Lock() |
| 56 | defer p.mu.Unlock() |
| 57 | |
| 58 | now := p.now() |
| 59 | if p.cachedToken != "" && now.Add(p.refreshMargin).Before(p.cachedExpiry) { |
| 60 | return p.cachedToken, p.cachedExpiry, nil |
| 61 | } |
| 62 | |
| 63 | token, err := p.cred.GetToken(ctx, policy.TokenRequestOptions{Scopes: p.scopes}) |
| 64 | if err != nil { |
| 65 | // Fall back to cached token if it hasn't expired yet |
| 66 | // Re-evaluate time after refresh attempt, because GetToken may block. |
| 67 | fallbackNow := p.now() |
| 68 | if p.cachedToken != "" && fallbackNow.Before(p.cachedExpiry) { |
| 69 | return p.cachedToken, p.cachedExpiry, nil |
| 70 | } |
| 71 | return "", time.Time{}, err |
| 72 | } |
| 73 | if token.Token == "" { |
| 74 | return "", time.Time{}, fmt.Errorf("received empty token for scopes %v", p.scopes) |
| 75 | } |
| 76 | |
| 77 | p.cachedToken = token.Token |
| 78 | p.cachedExpiry = token.ExpiresOn |
| 79 | |
| 80 | return p.cachedToken, p.cachedExpiry, nil |
| 81 | } |