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add support for AWS KMS credentials using .spec.decryption
Signed-off-by: Sanskar Jaiswal <[email protected]>
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Sanskar Jaiswal
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Apr 28, 2022
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,284 @@ | ||
| package awskms | ||
|
|
||
| import ( | ||
| "encoding/base64" | ||
| "fmt" | ||
| "os" | ||
| "regexp" | ||
| "strings" | ||
| "time" | ||
|
|
||
| "github.com/aws/aws-sdk-go/aws" | ||
| "github.com/aws/aws-sdk-go/aws/credentials" | ||
| "github.com/aws/aws-sdk-go/aws/credentials/stscreds" | ||
| "github.com/aws/aws-sdk-go/aws/session" | ||
| "github.com/aws/aws-sdk-go/service/kms" | ||
| "github.com/aws/aws-sdk-go/service/sts" | ||
| "sigs.k8s.io/yaml" | ||
| ) | ||
|
|
||
| const ( | ||
| arnRegex = `^arn:aws[\w-]*:kms:(.+):[0-9]+:(key|alias)/.+$` | ||
| stsSessionRegex = "[^a-zA-Z0-9=,.@-]+" | ||
| ) | ||
|
|
||
| // MasterKey is a AWS KMS key used to encrypt and decrypt sops' data key. | ||
| type MasterKey struct { | ||
| Arn string | ||
| Role string | ||
| EncryptedKey string | ||
| CreationDate time.Time | ||
| EncryptionContext map[string]*string | ||
| credentials *credentials.Credentials | ||
| } | ||
|
|
||
| type Creds struct { | ||
| credentials *credentials.Credentials | ||
| } | ||
|
|
||
| func NewCreds(credentials *credentials.Credentials) *Creds { | ||
| return &Creds{ | ||
| credentials: credentials, | ||
| } | ||
| } | ||
|
|
||
| func LoadAwsKmsCredsFromYaml(b []byte) (*Creds, error) { | ||
| credInfo := struct { | ||
| AccessKeyID string `json:"aws_access_key_id"` | ||
| SecretAccessKey string `json:"aws_secret_access_key"` | ||
| SessionToken string `json:"aws_session_token"` | ||
| }{} | ||
| if err := yaml.Unmarshal(b, &credInfo); err != nil { | ||
| return nil, fmt.Errorf("failed to unmarshal AWS credentials file: %w", err) | ||
| } | ||
| creds := credentials.NewStaticCredentials(credInfo.AccessKeyID, credInfo.SecretAccessKey, credInfo.SessionToken) | ||
| return &Creds{ | ||
| credentials: creds, | ||
| }, nil | ||
| } | ||
|
|
||
| func (c Creds) ApplyToMasterKey(key *MasterKey) { | ||
| key.credentials = c.credentials | ||
| } | ||
|
|
||
| // EncryptedDataKey returns the encrypted data key this master key holds | ||
| func (key *MasterKey) EncryptedDataKey() []byte { | ||
| return []byte(key.EncryptedKey) | ||
| } | ||
|
|
||
| // SetEncryptedDataKey sets the encrypted data key for this master key | ||
| func (key *MasterKey) SetEncryptedDataKey(enc []byte) { | ||
| key.EncryptedKey = string(enc) | ||
| } | ||
|
|
||
| // Encrypt takes a sops data key, encrypts it with KMS and stores the result in the EncryptedKey field | ||
| func (key *MasterKey) Encrypt(dataKey []byte) error { | ||
| sess, err := key.createSession() | ||
| if err != nil { | ||
| return fmt.Errorf("failed to create session: %w", err) | ||
| } | ||
| kmsSvc := kms.New(sess) | ||
| out, err := kmsSvc.Encrypt(&kms.EncryptInput{Plaintext: dataKey, KeyId: &key.Arn, EncryptionContext: key.EncryptionContext}) | ||
| if err != nil { | ||
| return fmt.Errorf("failed to encrypt sops data key with AWS KMS: %w", err) | ||
| } | ||
| key.EncryptedKey = base64.StdEncoding.EncodeToString(out.CiphertextBlob) | ||
| return nil | ||
| } | ||
|
|
||
| // EncryptIfNeeded encrypts the provided sops' data key and encrypts it if it hasn't been encrypted yet | ||
| func (key *MasterKey) EncryptIfNeeded(dataKey []byte) error { | ||
| if key.EncryptedKey == "" { | ||
| return key.Encrypt(dataKey) | ||
| } | ||
| return nil | ||
| } | ||
|
|
||
| // Decrypt decrypts the EncryptedKey field with AWS KMS and returns the result. | ||
| func (key *MasterKey) Decrypt() ([]byte, error) { | ||
| k, err := base64.StdEncoding.DecodeString(key.EncryptedKey) | ||
| if err != nil { | ||
| return nil, fmt.Errorf("error base64-decoding encrypted data key: %s", err) | ||
| } | ||
| sess, err := key.createSession() | ||
| if err != nil { | ||
| return nil, fmt.Errorf("error creating AWS session: %w", err) | ||
| } | ||
| kmsSvc := kms.New(sess) | ||
| decrypted, err := kmsSvc.Decrypt(&kms.DecryptInput{CiphertextBlob: k, EncryptionContext: key.EncryptionContext}) | ||
| if err != nil { | ||
| return nil, fmt.Errorf("failed to decrypt sops data key with AWS KMS: %w", err) | ||
| } | ||
| return decrypted.Plaintext, nil | ||
| } | ||
|
|
||
| // NeedsRotation returns whether the data key needs to be rotated or not. | ||
| func (key *MasterKey) NeedsRotation() bool { | ||
| return time.Since(key.CreationDate) > (time.Hour * 24 * 30 * 6) | ||
| } | ||
|
|
||
| // ToString converts the key to a string representation | ||
| func (key *MasterKey) ToString() string { | ||
| return key.Arn | ||
| } | ||
|
|
||
| // NewMasterKey creates a new MasterKey from an ARN, role and context, setting the creation date to the current date | ||
| func NewMasterKey(arn string, role string, context map[string]*string) *MasterKey { | ||
| return &MasterKey{ | ||
| Arn: arn, | ||
| Role: role, | ||
| EncryptionContext: context, | ||
| CreationDate: time.Now().UTC(), | ||
| } | ||
| } | ||
|
|
||
| // NewMasterKeyFromArn takes an ARN string and returns a new MasterKey for that ARN | ||
| func NewMasterKeyFromArn(arn string, context map[string]*string, awsProfile string) *MasterKey { | ||
| k := &MasterKey{} | ||
| arn = strings.Replace(arn, " ", "", -1) | ||
| roleIndex := strings.Index(arn, "+arn:aws:iam::") | ||
| if roleIndex > 0 { | ||
| k.Arn = arn[:roleIndex] | ||
| k.Role = arn[roleIndex+1:] | ||
| } else { | ||
| k.Arn = arn | ||
| } | ||
| k.EncryptionContext = context | ||
| k.CreationDate = time.Now().UTC() | ||
| return k | ||
| } | ||
|
|
||
| // MasterKeysFromArnString takes a comma separated list of AWS KMS ARNs and returns a slice of new MasterKeys for those ARNs | ||
| func MasterKeysFromArnString(arn string, context map[string]*string, awsProfile string) []*MasterKey { | ||
| var keys []*MasterKey | ||
| if arn == "" { | ||
| return keys | ||
| } | ||
| for _, s := range strings.Split(arn, ",") { | ||
| keys = append(keys, NewMasterKeyFromArn(s, context, awsProfile)) | ||
| } | ||
| return keys | ||
| } | ||
|
|
||
| func (key MasterKey) createSession() (*session.Session, error) { | ||
| re := regexp.MustCompile(arnRegex) | ||
| matches := re.FindStringSubmatch(key.Arn) | ||
| if matches == nil { | ||
| return nil, fmt.Errorf("No valid ARN found in %q", key.Arn) | ||
| } | ||
|
|
||
| config := aws.Config{ | ||
| Region: aws.String(matches[1]), | ||
| Credentials: key.credentials, | ||
| } | ||
|
|
||
| opts := session.Options{ | ||
| Config: config, | ||
| AssumeRoleTokenProvider: stscreds.StdinTokenProvider, | ||
| SharedConfigState: session.SharedConfigEnable, | ||
| } | ||
| sess, err := session.NewSessionWithOptions(opts) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| if key.Role != "" { | ||
| return key.createStsSession(config, sess) | ||
| } | ||
| return sess, nil | ||
| } | ||
|
|
||
| func (key MasterKey) createStsSession(config aws.Config, sess *session.Session) (*session.Session, error) { | ||
| hostname, err := os.Hostname() | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| stsRoleSessionNameRe, err := regexp.Compile(stsSessionRegex) | ||
| if err != nil { | ||
| return nil, fmt.Errorf("Failed to compile STS role session name regex: %w", err) | ||
| } | ||
| sanitizedHostname := stsRoleSessionNameRe.ReplaceAllString(hostname, "") | ||
| stsService := sts.New(sess) | ||
| name := "sops@" + sanitizedHostname | ||
| out, err := stsService.AssumeRole(&sts.AssumeRoleInput{ | ||
| RoleArn: &key.Role, RoleSessionName: &name}) | ||
| if err != nil { | ||
| return nil, fmt.Errorf("Failed to assume role %q: %w", key.Role, err) | ||
| } | ||
| config.Credentials = credentials.NewStaticCredentials(*out.Credentials.AccessKeyId, | ||
| *out.Credentials.SecretAccessKey, *out.Credentials.SessionToken) | ||
| sess, err = session.NewSession(&config) | ||
| if err != nil { | ||
| return nil, fmt.Errorf("Failed to create new aws session: %w", err) | ||
| } | ||
| return sess, nil | ||
| } | ||
|
|
||
| // ToMap converts the MasterKey to a map for serialization purposes | ||
| func (key MasterKey) ToMap() map[string]interface{} { | ||
| out := make(map[string]interface{}) | ||
| out["arn"] = key.Arn | ||
| if key.Role != "" { | ||
| out["role"] = key.Role | ||
| } | ||
| out["created_at"] = key.CreationDate.UTC().Format(time.RFC3339) | ||
| out["enc"] = key.EncryptedKey | ||
| if key.EncryptionContext != nil { | ||
| outcontext := make(map[string]string) | ||
| for k, v := range key.EncryptionContext { | ||
| outcontext[k] = *v | ||
| } | ||
| out["context"] = outcontext | ||
| } | ||
| return out | ||
| } | ||
|
|
||
| // ParseKMSContext takes either a KMS context map or a comma-separated list of KMS context key:value pairs and returns a map | ||
| func ParseKMSContext(in interface{}) map[string]*string { | ||
| // nonStringValueWarning := "Encryption context contains a non-string value, context will not be used" | ||
| out := make(map[string]*string) | ||
|
|
||
| switch in := in.(type) { | ||
| case map[string]interface{}: | ||
| if len(in) == 0 { | ||
| return nil | ||
| } | ||
| for k, v := range in { | ||
| value, ok := v.(string) | ||
| if !ok { | ||
| // log.Warn(nonStringValueWarning) | ||
| return nil | ||
| } | ||
| out[k] = &value | ||
| } | ||
| case map[interface{}]interface{}: | ||
| if len(in) == 0 { | ||
| return nil | ||
| } | ||
| for k, v := range in { | ||
| key, ok := k.(string) | ||
| if !ok { | ||
| // log.Warn(nonStringValueWarning) | ||
| return nil | ||
| } | ||
| value, ok := v.(string) | ||
| if !ok { | ||
| // log.Warn(nonStringValueWarning) | ||
| return nil | ||
| } | ||
| out[key] = &value | ||
| } | ||
| case string: | ||
| if in == "" { | ||
| return nil | ||
| } | ||
| for _, kv := range strings.Split(in, ",") { | ||
| kv := strings.Split(kv, ":") | ||
| if len(kv) != 2 { | ||
| // log.Warn(nonStringValueWarning) | ||
| return nil | ||
| } | ||
| out[kv[0]] = &kv[1] | ||
| } | ||
| } | ||
| return out | ||
| } |
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