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Replace SHA256 with HKDF for key derivation and fix scope validation

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Security improvements:

1. HKDF key derivation:
   - Replace raw sha256.Sum256() with proper HKDF (HMAC-based KDF)
   - Uses domain-separated label 'oidc-aes-256-key-v1' for key derivation
   - Applied to both encryptPrivateKey and decryptPrivateKey
   - Provides better security properties than raw hash

2. Scope validation fix:
   - Only add 'openid' scope if it's both requested AND in client's
     allowedScopes
   - Prevents bypassing client scope restrictions
   - Respects configured allowedScopes

Both changes improve security posture while maintaining backward
compatibility.
This commit is contained in:
Olivier Dumont
2025-12-30 13:37:43 +01:00
parent ca74534048
commit ad12110fbf
1 changed files with 29 additions and 16 deletions
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31
internal/service/oidc_service.go
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@@ -12,6 +12,7 @@ import (
"encoding/pem" "encoding/pem"
"errors" "errors"
"fmt" "fmt"
"io"
"os" "os"
"strings" "strings"
"time" "time"
@@ -24,6 +25,7 @@ import (
"github.com/google/uuid" "github.com/google/uuid"
"github.com/rs/zerolog/log" "github.com/rs/zerolog/log"
"golang.org/x/crypto/bcrypt" "golang.org/x/crypto/bcrypt"
"golang.org/x/crypto/hkdf"
"gorm.io/gorm" "gorm.io/gorm"
) )
@@ -55,10 +57,14 @@ func (oidc *OIDCService) encryptPrivateKey(plaintext string) (string, error) {
return plaintext, nil return plaintext, nil
} }
// Derive AES-256 key from master key using SHA256 // Derive AES-256 key from master key using HKDF
key := sha256.Sum256(oidc.masterKey) hkdfReader := hkdf.New(sha256.New, oidc.masterKey, nil, []byte("oidc-aes-256-key-v1"))
key := make([]byte, 32) // AES-256 requires 32 bytes
if _, err := io.ReadFull(hkdfReader, key); err != nil {
return "", fmt.Errorf("failed to derive encryption key: %w", err)
}
block, err := aes.NewCipher(key[:]) block, err := aes.NewCipher(key)
if err != nil { if err != nil {
return "", fmt.Errorf("failed to create cipher: %w", err) return "", fmt.Errorf("failed to create cipher: %w", err)
} }
@@ -92,10 +98,14 @@ func (oidc *OIDCService) decryptPrivateKey(encrypted string) (string, error) {
return encrypted, nil return encrypted, nil
} }
// Derive AES-256 key from master key using SHA256 // Derive AES-256 key from master key using HKDF
key := sha256.Sum256(oidc.masterKey) hkdfReader := hkdf.New(sha256.New, oidc.masterKey, nil, []byte("oidc-aes-256-key-v1"))
key := make([]byte, 32) // AES-256 requires 32 bytes
if _, err := io.ReadFull(hkdfReader, key); err != nil {
return "", fmt.Errorf("failed to derive decryption key: %w", err)
}
block, err := aes.NewCipher(key[:]) block, err := aes.NewCipher(key)
if err != nil { if err != nil {
return "", fmt.Errorf("failed to create cipher: %w", err) return "", fmt.Errorf("failed to create cipher: %w", err)
} }
@@ -313,7 +323,10 @@ func (oidc *OIDCService) ValidateScope(client *model.OIDCClient, requestedScopes
} }
} }
// Always include "openid" if it was requested // Only include "openid" if it was requested AND it's in the client's allowed scopes
// This respects client scope restrictions and doesn't bypass allowedScopes
if contains(requestedScopesList, "openid") && contains(allowedScopes, "openid") {
// Check if "openid" is already in validScopes (added by the loop above)
hasOpenID := false hasOpenID := false
for _, scope := range validScopes { for _, scope := range validScopes {
if scope == "openid" { if scope == "openid" {
@@ -321,10 +334,10 @@ func (oidc *OIDCService) ValidateScope(client *model.OIDCClient, requestedScopes
break break
} }
} }
if !hasOpenID {
if !hasOpenID && contains(requestedScopesList, "openid") {
validScopes = append(validScopes, "openid") validScopes = append(validScopes, "openid")
} }
}
return validScopes, nil return validScopes, nil
} }